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Rehashing the Classic Single Side Damper

color0 — Sun, 09 Dec 2012 12:49:26 GMT

It's been said before that there are never any new ideas, everything new is just a rehash of something old. That's not always true but for the new racing "season" I'm doing it, using one Kyosho Oil Shock as a single side damper (SSD) on the MR03. The idea has been around a long time -- they've faded in and out of fashion in 1/12 pan cars, the InZane (now Lajf) P28 carries one, and to be fair, we at Greyscale have been playing with SSD's for a long time already. It just never occurred to me till recently that the Kyosho shock might be the best candidate to actually implement the concept with. For shame. :rolleyes:

And it's simple as heck too.

The philosophy behind this kind of a setup is that you have a narrow setup window in which you can use a tube damper for bump and a proper oil shock for roll -- the bump stiffness must be a fair bit higher than the roll stiffness, such that individual road bumps hitting a rear wheel will actuate the roll (oil) damper more than the bump (tube) damper. Fortunately, we deliver! since most MR-03 T-plates are cut to be softer in roll than bump stiffness. Should the outside rear wheel encounter a mid-corner disturbance, the Kyosho oil shock can handle it better than any existing side shock or disk damper setup, thanks to the "packing" effect.

Unfortunately, I couldn't find any good pictures to illustrate, but I'll explain: The "packing" effect is one inherent to oil shocks, whereby if you actuate the shock fast enough, you can cause it to lock up. In a nutshell, oil shocks' pistons directly push and pull on a volume of oil, whereas tube and disk dampers indirectly do so via something akin to friction between the surface and the layer of grease itself (FYI, the grease at the interface between grease and surface actually doesn't move relative to the surface. This is called the "boundary layer" for almost all fluid flows, gas or liquid). Because there's no direct force exerted on the grease by a tube or disk damper, you can wail as hard as you want on them, and they will simply move more the faster you actuate it. Do it too fast and the grease can even cease to remain attached to the surface (disks/plates or tubes/shafts). If you lose the bond, you no longer have damping for that split second, and that is a nice big problem to have mid-lap on the track isn't it. :)

Oil shocks work differently -- since they push directly on an oil volume, in both compression and extension directions, if you push sufficiently hard you will actually not give the oil time to gather itself and flow around the piston. Instead, the oil in the oil shock will resist your movement while it's still gathering itself, and the remaining volume of oil that can't move yet essentially is an incompressible fluid that your piston is trying to compress. The piston can't move then, and thus you get lockup, or "pack", of the oil shock. With this opposite effect from tube and disk dampers, you are (barring mechanical failure) guaranteed not to lose damping with an oil shock, the only question is how you control the transition between normal damping and "pack" damping, and the magnitude of pack once you hit the transition.

And I will be the first to admit that I haven't played with it much yet! The Kyosho oil shock is a tiny, tiny thing and it's going to take a lot of experimentation with different viscosity oil, as well as possibly developing different sized pistons, before one can master packing of this particular shock. Till we do (and it'll probably happen), I used Kyosho/R246's #400 oil as the normal, non-packing damping characteristics came out similar to my old PN Tri-shock with Kyosho 15k grease in the tubes.

The brackets may look familiar, I used them a long time ago to experiment with a SSSD setup (sprung! lol) using the PN Dual Spring Shock, but it did not turn out as nice as I needed it to, mostly due to the annoyance of readjusting the shock every time you wanted to do maintenance. But with the Kyosho shock you just build it one, build it right, and then forget about it till it starts feeling scratchy. I lament the loss of rear tweak adjustment, but the rear end of my car was found to be 100% square so long as you build the shock right -- figure out the ideal resting length that the Kyosho shock should be, and then when filling the shock, set it to that ideal length before installing the bladder and shock cap. The bladder provides a little spring force to keep your rear suspension centered, so do it right or regret it. You can probably use the bladder preload to adjust tweak, too! But that takes even more care, and likely redos, before you get the car properly tweak-adjusted.

With the new shock in replacing the tri-shock components, I believe you save a little bit of weight, but the setup lies higher so there may not be a CG benefit. But on the bench, the damping smoothness feels perfect and I'll make good of my next Kenon time to figure out the right fluid weights and T-plates to dial in the setup properly on track. Studying the packing effect will be particularly fun, thankfully Grant has a slow-motion enabled camera, maybe if we're slow enough you might be able to catch the pack differences between tri-shock, disk damper and our SSD concept! Till we do, this will be an exciting new development for me and I can't wait to pair it with something else I've also been working on since before the Worlds. ;)

PNWC 2012 F1 Pro Setup

color0 — Wed, 05 Dec 2012 08:10:24 GMT

I realize I haven't said much about the F1 I own, and it's mainly because this car just takes a lot of work to get it running... mostly electrical gremlins occurring in heavily populated areas.

As far as the Worlds' go, F1 Pro was just pure frustration -- my car was definitely the fastest in the field and proved it with the fastest lap in qualifying and IIRC, the fastest F1 lap of the weekend. But the GLITCH! kept coming back again and again and in the end it just wouldn't hold together for 8 minutes without punting itself into the wall.

Since the mechanicals are good, however, I will go into a little detail on the setup and a couple general thoughts on how to make the Mini-Z F1 dance.

My car is a bit of a Frankenstein MF-015, it's running all the right electronics, chassis, body and accessories but it was put together from a combination and new and used parts. The normal MF-015 Ferrari body is here, minus two sub-wings on the front wing. Taking them out removed some unnecessary front downforce I think, I first noticed this at Kenon that the car got a lot easier to drive. It does NOT help that the new Ferrari has a very shallow rear spoiler vs. the new McLaren and pretty much every other Mini-Z F1 in history -- no rear downforce. I was planning to make a gurney flap for the rear wing the minute I bought it, but after breaking off the front sub-wings, seems like I didn't need it.

I reinforced the rear wing with epoxy, "just in case" for PNWC. Never had to find out whether the epoxy or the plastic wing mount is stronger though. :)

Edit: If you run the old-school PN F1 motor mount like I do, make sure to dremel out the MF-015 bodies to make enough clearance for suspension travel. My rear end was locked up till I thinned out the offending plastic to near zero!

Suspension and tire wise I was also able to sort it all out great. The combo to run is K30/K20, the newest slicks only (don't use the old grooved stuff, the compound pales in comparison to the new tires). PN6 could be used in the rear but they don't last as long, and I really don't like mounting F1 tires. The front end of the F1 takes very little work (as you don't want too much grip anyways). I stuck with 0deg camber and used Kyosho Green springs with 0.6mm of shims under the knuckle to lower the car.

The rear is nowhere as sophisticated as my MR03, just flex plates and the Kyosho carbon disk damper, which I believe I mounted upside down. Had to ream out holes in the stock bridge to mount the carbon plate under the metal, which lowered the entire assembly enough that I didn't have to cut through a brand-new ASC F1 body just to have some damping.

As far as rear end "feel" goes, the disk damper works well with polished carbon disks and plate, and some Ruby Lube for slickness. It would feel underdamped if I had not removed the middle screw in the F1 flex plates though (keep reading).

The flex plates on the car are Kyosho's FRP plates -- interestingly, they offer more traction than the carbon plates despite being stiffer.

I'm also gonna call it now, everyone should just quit using the middle screw in the F1 flex plates. Sure, you weaken the car but it handles so much better, I promise you won't spin or crash as much. The suspension becomes much softer in roll (good!) and the rear end gains a lot of droop to keep the inside rear wheel planted on the ground (even better!). The corner exit characteristics go from feeling skatey/darty and start feeling like the MRCG, planted and big on rotation. Makes sense, their rear suspensions are similar after you've removed the extra screws. And given I designed the MRCG, you can imagine how much I appreciate the change in behavior.

Rear diff: Always the kicker for 2WD, right? There's something magical about this diff lol. I got it with the car from Ryan Sagisi and it appears to be a straight Kyosho diff with a Reflex spur (borrowed from Alex M). I 1) never had to clean it and 2) it spins consistently free despite visual dirt inside the Reflex spur. I wasn't about to fix something not even remotely broken, and this diff probably contributed a lot to my 12.6 fast lap. Guess I have a thing or two more to learn about building diffs... :)

But yes, since this car has proven electrically unreliable at Binh's place, I'm not sure I'm going to continue racing it. When it did listen, it was super, super fast, easily keeping up with Mod cars for corner speed. It just needs to listen more often. :roll:

---------------------------

And that's it for my brief review of my PNWC setups... I'm sorry it couldn't be a bit more detailed but recovering from the flu seriously put a damper on my experience, at least on the technical and racing side. Now that I'm all better though, and more caught up on the other parts of my life, we can start playing with a new rear end setup for the MR03 -- next week. :)

PNWC 2012 GT Mod Setup (Rather NG, but People Asked!)

color0 — Sat, 01 Dec 2012 14:01:18 GMT

Hokeydokey, so a long time ago (...a few weeks) I went to the PNWC 2012 race held at Inside Line Racing/Vallco Mall in Cupertino, CA. Unfortunately, I was sick, and my driving was pretty shot, so I knew I had no chance of winning, and instead I tested out a lot of different setups, got a lot of data on different bodies and diffs, and eventually settled on a 599XX with a ball diff and a LOT of holes. While I'm still not happy with how my setup performed at the Worlds', a couple people have asked me for the setup and so here it is -- pics below. I'll do my best to explain the significant and more unique bits of the setup.

For me, this Worlds' was mainly learning about how different setups complement different driving styles, and, body modifications to incrementally improve performance. Hence, my 599 now looks like Swiss cheese. To my surprise (and maybe yours), all of those holes help free up the car from being too planted and improve steering, surprisingly enough. The only bad holes in my testing were the ones just before the rear wheels -- something about them, probably air being allowed to enter the shell in front and somewhat under the rear wheels, started causing the car to traction roll in the main! I'm still wondering how two tiny holes can push the car over the edge just like that. They will be glued over from now on. I've only got one more set of holes I've yet to try with this body, and that's the front grill... Grant often cut his out and his body did corner a lot flatter than mine, on the same chassis. But after that, there's officially nothing left to cut on this body lol.

Additionally, something was up with the tech inspection jig IMO... I never had a problem clearing Philip's 20mm rear bumper rule up until this race. I checked my bumper height off the ground on qualifying day and found that I was definitely about to be DQ'd lol. So in a last-ditch effort to pass tech, I slathered 5-minute epoxy all over the lip (you can kinda see it in the pic). It hardened in 20 and I dremeled it all even and flat -- total weight gain maybe half a gram, and passed tech by about 0.5mm. :cool:

I'm not a fan of thinning out the white bodies, but I did thin out the roof. You can of course also see the other things that have been ground or cut out, including the headlight buckets. Screw those things, they saved over half a gram. :)

Two last dremel mods before the B Main (yep, no A Main for me, reflexes were too dulled) to avoid stupid mistakes, basically. Cut off the front splitter, rounded it off -- it worked sometimes but I noticed it got caught more and more as the RCP rails got more damaged. The trick is to always have the front bumper polished (if not Teflon taped). Elliot M. showed me his polished 599 front bumper and true to form, I rode the rails lap after lap with no consequence. Live and learn Brian! I also rounded off the leading edge of the side skirt, just in case. Thankfully, no issues to report there.

Chassis-wise, I don't have much to be proud of in this setup. It hasn't changed a whole lot, just spring changes here and there mainly. I stripped out my double A-arm's top mount, thus ended up borrowing Grant's silver one and using his ride height/spring preload settings to boot.

He runs the roll center higher than me, and well, I guess now I'm running the same roll center lol. I put an Atomic 0.2mm shim below each (new batch) PN Green spring, otherwise the car would droop way too much. The setting works well I think, objectively producing the same laps as my older, lower setup, but a little more forgiving (the new springs are shorter by more than 0.2mm, so I guess I've added some droop since stripping out my top mount).

Also nothing specially changed up top: green spring to plant the rear end better at throttle tip-in, and loosened up rebound spring (still purple, still using a Kyosho AWD spring spacer to give the short spring some room to play) to ease the off-throttle behavior. Binh's track is not known for being grippy, especially not when freshly laid out on a cold tile floor that is Vallco Mall. So easy to drive and non-twitchy is paramount.

Same deal with the tri-shock... soft roll stiffness for more rear grip and more time to save the car when it slides. I suspect now though that this still isn't soft enough -- I felt up some of the other drivers' cars (with permission) and the rear end of the disk damper Mod cars is super soft in roll. And all of them drive smoother, rounder lines than the tri-shock equipped cars (a lot of PN drivers). So what's the deal here? I much prefer to drive smooth lines, as I can't time anything well enough to do point-and-shoot (aka Grant-style). And I've been trying to make it happen with a tri-shock for a LONG time, yet here I am getting reminded once again that the disk damper setup works just fine with the right quality components (for the record: polished metal plate and Teflon disks). The biggest difference that I could feel was not the damping force or the speed, but simply that the roll stiffness of the DDS cars was so much softer than any tri-shock car. Does it make a difference? Honestly, I haven't tried in a long time. Is it worth it now that PNWC is over? Absolutely. I'll have a new post about the new setup very soon, I couldn't quite put the PN dual-spring shock down so I had to get another setup personalized just for me lol.

Back to PNWC performance, what I did notice with all the body mods and my almost standard chassis setup is the corner speed is still characteristically high. I think I was one of a few drivers in Mod not to use brakes or drag brakes at all and get away with it. The car carried lots of speed and rotated quickly about tight corners and I simply didn't need to slow down unless I wanted to play it safe. Which, in retrospect, should have been done since I simply wasn't in the right health to drive well. As another PN driver pointed out to me, my car was stupid fast in the infield, but every few laps -- oops! -- a wall tap. The inside wall, too, indicating the car was too twitchy. Now, my setups have been getting mellower and mellower over the years to avoid tapping the inside wall but clearly, that weekend I was so gone I would've needed a lot more compensation in the setup for the level of driving I put out. So I gave up on tuning by the 3rd qualifier and honestly kinda gave up driving as well, just aiming to produce some semblance of clean racing with the other cars on track and staying out of the actual battles.

You can also see I'm back to the 126p PN ceramic ball diff after using a gear diff for the better part of the last year... this was mostly for safety reasons, with the new RCP being so loose, a gear diff and a torquey new 33t just didn't seem like a smart idea. In practice, the car actually hooked up quite alright (using the 90/80/70% throttle speed reduction as traction control) but mid-corner adjustments were scary. Despite all my efforts my MR03 was still too twitchy for this track, and mostly because I forgot to set the ICS! Recall my ICS settings for the car's steering:

SPEED: Fast
PNCH: 2

Ah right, I forgot about my recipe for a "lively" car. While yes, I've always liked these settings back when I raced 80t, in Mod it just makes small steering corrections difficult (doesn't help that my pot was old). So between the 599's side vent cutouts and ICS tuning making the steering waaaay too fast, I traction rolled so much in the B Main I wasn't even competitive. Anyways, it ticks me off and when I get another chance to play with ICS, I'll be setting the PNCH to as low as possible and the SPEED probably one click slower than "Fast". Mod for me is still all about getting the car to make up for the complete lack of driver talent, such that I say "go" and it figures out the rest for me (aka the Prius, lol). So that's the game I guess, and I will continue playing with a brand new setup approach this coming "season". Coming soon!

PN Racing 4D Trigger -- Setting it Up

color0 — Sun, 23 Sep 2012 02:20:52 GMT

Hey everyone,

Sorry it took me so long to get this article out, but it is here finally. :)

The PN Racing 4D Trigger is a pretty clever bit, essentially it puts all the contact surfaces (forward/reverse) of the trigger on relocatable pivots so you can very carefully control how the trigger feels in your index finger. This allows you to have a true no-play, no-lag trigger, and you can have full confidence in modulating the brake and throttle input as this trigger (when set up properly) WILL NOT slip off your finger. It also looks like the freakin' Terminator, if that's your thing.

You do have to put in some work to get the functionality out of it though, and if you've been wondering how the heck it should be done, you can take a look at my setup and try it out as a baseline. :)

First things first, adjustments on this trigger are made by a normal 1.5mm hex wrench, which secures a set screw sitting inside a ball. Overtighten any one of these balls and you will mar the steel shaft, so be warned -- I messed this one up early on and had to Dremel polish the shaft to get the balls back on lol.

As far as adjusting the trigger goes, it's all giong to depend on how your hand is preferably positioned. My left hand tends to sit high/"choke up" on the EX-10 pistol grip, so that's why the first alu piece on your finger pad (let's call this the forward pad, as you press this to go) sits almost at its highest setting for me (teal arrow pointing up). If you grab your radio at a lower position then you will want to lower this part to match where your index finger most naturally lines up.

The second arrow in the above image indicates the slight twist outwards that I give the forward pad, in order to mesh exactly right with the angle of my index finger when in neutral trigger position. It's less than 5 degrees of twist, but this makes all the difference because the edge of the forward pad can be sharp! I actually filed mine down on all edges with a dremel and sandpaper to smooth out the contours.

On to the piece that contacts the back of your finger (let's call this the "reverse pad"). There are many ways to set this one but the most important thing is to avoid scratching your finger at any point during the forward/reverse throttle travel. Again, the edges are sharp so I filed down everything, but even then the curve of the reverse pad is a little too much, and I can't make it fit comfortably on my relatively slender finger. So, that's why the velcro is there. To make it fit with the extra thickness of the velcro, I moved the shaft mounting the reverse pad outwards (arrow pointing left, below), slide the reverse pad itself downwards to match up to where the forward pad would place my finger, and finally gave the reverse pad a bit of a twist too in order to feel the best in the "transition area" between forward and reverse/braking. With the velcro in place, the twisted mounting of both pads allows the trigger to be really snug, but without pinching my finger in any range of movement.

The way I placed the velcro is also important: the top edge of the forward and reverse pads is exceptionally narrow and no amount of Dremeling/filing would dull it off for me, so I went with plan B and just covered up those edges with velcro. However, you can see (left side of the velcro strip) that the contact area with the forward pad is very, very small, and so I ended up supergluing the entire velcro strip in once I had confirmed that everything was comfortable. :)

So there you go, from this last closeup you should be able to see that the 4D trigger can really take out 100% of the free space between your finger and your trigger -- the hole left in the gap is pretty much the exact cross-section of my index finger lol. Pretty slick. And with the velcro acting as a comfort pad, I've become much more willing to use the brakes than before, as well as much more able to modulate the brakes from 0-50%. It's an expensive part to buy at first but the added comfort and precision have improved my ability to place the car a lot -- even if you don't gain in absolute fast lap times, you definitely should notice more consistency when your finger doesn't shift on the trigger anymore.

Lastly, the trigger evidently fits all EX-1 (Mars, Mars R, UR), EX-1 KIY and EX-10 models from KO Propo without modification. So for now at least, you can buy only one trigger and move it around whenever you decide to upgrade/change radios. :)

Function Art, Part 4

arch2b — Sun, 26 Aug 2012 23:06:15 GMT

I started painting yesterday. The inside of the channel was painted with a flat black to keep a dull finish. I paint the exterior with a satin black. The process starts off with light coats and each builds on that.

With The final coat, I back up an inch or two to give it a slight texture. I prefer this over trying to get a glass smooth finish.

There are some slight paint bleeds and peels but overall it came out really well.

It took over an hour to peel all the letter of the biblical quote.

Body Modifications for Perfect Stance

color0 — Sun, 26 Aug 2012 09:21:20 GMT

One of the great things about the Mini-Z's styrene plastic body is that it is a lot more modification-friendly than the polycarbonate bodies used in other scales. You can cut, sand, polish, weld, melt, etc. allowing you to push the envelope on your creation, whether that is reducing weight for racing, adding lights for show, or, as we'll be covering here, achieving the perfect lowered stance while keeping the car driveable.

I'm going to assume that we already understand how to lower a Mini-Z body in general -- space out the front clip on the chassis to lower it, then raise the side clips on the body to seat the body lower relative to the chassis. The problem though is that if you're trying to fit wide enough wheels/tires to fill out the fender, you can only lower it so much before it starts rubbing (of course). So we bust out the trusty Dremel and have a go -- naturally. :)

For fine-detail bodywork I actually prefer using this tiny dremel bit over files/sandpaper now, because my fingers just aren't that small and this little bit (~4mm diameter) has a sharper tip that really gets to wherever I need it to go. For the record, this is Dremel silicon carbide grinding bit #83322.

Using this bit, gently carve out the inside of the wheel well: you only need to carve the top "side" of the wheel well -- basically, carve wherever you see the tire rub the inside of the body. Carve, measure, carve, measure, carve, and you'll start to see your wheel make it farther up into the wheel well before the tire rubs.

Depending on your wheel/tire setup, you may end up grinding the wheel well plastic so thin that the Dremel bit starts pushing the fender outwards -- this isn't necessarily a bad thing, since pushing it outwards gives you more space, but you do want to watch out for the edge of the plastic becoming way too fragile. See red arrow below, where my F430's rear fender started to bow outwards from the pressure.

Shaving the plastic that thin also makes it susceptible to fraying at the edges, but thankfully we do have a fix for that. Take your fingernail, and fold the edge inwards. This gives a nice clean "rolled" edge as well as preserving it from tearing. If you want to be extra anal you can find something to roll the fender edge, which will make it even cleaner, and, while you're at it, you can even pull the fender out further to give you more tire clearance since the plastic has been thinned out. I did a little bit with the smooth side of my nail, but a proper scaled-down fender roller is the best tool if you want to do this.

So, you continue this process of carve, measure, fold, and if you've picked the right wheel offsets, you'll get the "stance".

On this particular F430 I've fit +2.2N up front (MR03W front end) and +2W in the back, and it's perfectly flush, and not rubbing, front or rear. I wouldn't recommend running this close clearance for racing of course, but it's very driveable "at home" and looks downright cool. On the Mini-Z AWD, since you can dial in more camber into the front and rear ends, you can potentially pick even wider offsets and make it look even more aggressive. The front end, as you might notice, is not quite as low as the rear, and there's no real way out of this with the MR03's steering geometry -- wheels gotta steer lol. Nonetheless, it's not too obvious (just look at the first picture in this post), so I hope to see more beautifully stanced Mini-Z's soon running parade laps on the RCP. :)

Functional Art, Part 3

arch2b — Sat, 25 Aug 2012 16:53:41 GMT

Short follow-up this time...

For the club title, I printed half a dozen options at least before settling on the final selection. I believer it's a good fit for the club, it's mission and personality. It was not the easiest option for sure but I feel it fit the best.

Functional Art, Part 2

arch2b — Sat, 25 Aug 2012 16:47:19 GMT

I immediately dove into the 'art' portion of the build which is dressing the bridge channel. It starts with of course the 2x2x36 aluminum channel. This sounds like a lot of surface area to work with but the limitations of working within a 2" vertical dimension gets tricky.

36" just fits the width of a two tile wide RCP 50cm track. These come in various widths and can easily find a length that will fit a 3 tile wide track however that limits you to only 3 tile wide tracks that are infrequent in our parts so it's best to stick with 2 tile wide.

First thing to do is sand the surface to clean off any residue and surface anomalies. This process also helps with paint adhesion so it's worthwhile to do. I typically use a fine grit foam sanding block you can get from any hardware store. Always wipe down the surface with an appropriate cleaner to remove all the dust, finger oils, etc. Its then onto covering the canvas with masking tape. I always use Tamiya simply because i can buy it locally and it works. I've had great success with it so no reason to fix something that isn't broken. There are other quality products out there however this works for me so go with what your most comfortable with it your doing this or something similar. I can't stress enough how important it is to start with a quality masking tape. It can make or break your paintwork.

You will want to minimize the overlapping as much as possible as it simply makes it harder to complete delicate stencil work through multiple layers of masking tape and overlap joints. I used the 40mm tape for the job as it allowed me to cover the entire surface in 4 strips. 3 would have been better...maybe next time. This tape is different from the normal 18mm tape i use. The tape less pliable and the surface tension is greater than the thinner tapes. I typically only use the 40mm tape for larger coverage areas without curved surfaces.

I did not get as many pictures of this build so far so I will use examples from the previous build when needed.

I use Photoshop, Autocad, Word or whatever works best and available at the time to plan out the text, character spacing, font choice, etc. to scale and proper fit for the area it is intended and print out on whatever paper it available. If i had the resources, you can get stencil cutting printers that would create the masking stencil for you eliminating a few steps in this process but alas, that is not in my budget so I'm bouncing between masking tape, paper and cutting knife.

Example of various text stencil options i print to choose the one i like most when looking at the actual channel. I feel it's important to review the options as they would appear on the material vs. deciding off a screen or print.

Simply tape the stencil pattern (call it what you will, it serves as a pattern for my use) to the location where it will be applied. I use the Xacto knife with rubber grip as it's easier to hold for long periods of time and less prone to slipping in my fingers. when i do this again, I'll pick up one of the stenciling knives as the blade looks like it will be much easier to control vs. the standard #11. Use the knife to trim out the letters. Its much easier said than done at times. when you push to hard you end up fighting the grain of the metal and it's very easy to apply to much pressure when your going over areas of overlapping masking tape. The metal also dulls the blades very quickly so the longer one is used, the more force I need to use to keep clean cuts. I don't always change them enough so i am often cutting into the surface of the metal. A professional wouldn't even scar the metal surface but i'm no professional.

When the stencil work is completed and masking tape removed it looks like this

For this commission I included some logo's and graphics as well as text.

For this commission I also included a personal touch and stenciled a biblical quote, Ecclesiastes 9:11. I thought it suite this particular club very well and thoughtful prose applicable to the activity.

Quote:

I returned, and saw under the sun, that the race is not to the swift, nor the battle to the strong, neither yet bread to the wise, nor yet riches to men of understanding, nor yet favour to men of skill; but time and chance happeneth to them all.

Let me tell you, I was not prepared for all the cutting it took to get this done. I spent 1-2 hours a night for 3 days cutting out this bible quote. I'm confident that it was time well spent and will look fantastic when finished. It also took 2 days to peel the masking tape off as well. I peeled it back in two rows, first the bottom half and then the top half so i could ensure the lettering came out cleanly.

Functional Art

arch2b — Sat, 25 Aug 2012 15:51:58 GMT

After completing my 1st custom Giro-z Bridge I was given the opportunity to manufacturer an improved version:p I learned a lot of fabrication lessons on mine that will hopefully make this one easier to build and perfect right out of the gate.

First build

To begin with, I order 90% of this stuff from Amazon simply because it was more cost efficient. I'm sure i could source these materials locally but the enormous amount of time i spent attempting this the 1st time has led me to Amazon where you can buy just about everything, competitive pricing and free shipping for Prime members. I will update this materials list as they are purchased.

Materials:
Aluminum 6063-T52 U-Channel, Square Corner Style, AMS QQ-A-200/9, ASTM B221, 1/8" Thick, 2" Base Width, 2" Leg Length, 36" Length - $25.29

Stainless Steel 303 Round Rod, Annealed Temper, AMS 5640, 1/8" OD, 72" Length - $2.50 each

Loos Cableware SL2-4P 25 Piece Zinc Plated Copper Crimping Sleeve Set for 1/8" Diameter Wire Rope - $13.14 box of 25

Cables To Go 27267 Shielded Cat5E Molded Patch Cable, Red (25 Feet/7.362 Meters) - $11.20

Krylon Indoor/Outdoor Satin Black - $3.98 (already have)

Tamiya Masking tape $3.00+/- (already have)

1x1/2x double line clamp and 3/16 fasteners - $5.00+/- (already have)

M4x16 cap head screws - $.80 (already have)

nylon washers - $.56 (already have)

black cable ties - $4.54 (already have)

1/8 ferrules- $1.48 (already have)

M4 hex nut - $.80 (already have)

599XX: Flex and Aero Short Post

color0 — Wed, 15 Aug 2012 08:17:14 GMT

Lack of Internet last week, sorry guys.... anyways, new developments.

I recently got to run my 599 and Grant M's 599 back to back, and I noticed that while mine is WAY more stable in the rear end, Grant's loses only a little bit of rear end stability but gains a lot of front end traction, whether or not the front grill is opened up. The result of this was me getting owned at our Kenon "hot lap" battles, 8.036 vs. 7.852. Clearly I'm not happy about that :D so I've got work to do.

The main difference between our two body setups is that he tends to cut a lot of holes into the 599, but they're all small and out of the major airflow to be aerodynamically critical. Instead, I think that the cuts are creating flex. So at some point, I'm going to try those same cuts to make the body softer and get more mechanical grip out of my car. We've visited this theory a long time ago, with the 2007 Super GT 350Z body, as well as the new Audi R8 LMS which is super-flexible and, so far, looking extremely fast in Mod (Grant put down some 7.6xx at Kenon with the Autoscale!). But before that, I want to try getting more front steering without sacrificing the rear downforce advantage I have on Grant. :) Hence:

Hood vents are a proven method of reducing lift on the hood area -- the low-pressure bubble that normally forms on the hood will instead now pull air out from underneath the car, sucking the car down towards the ground. :) If the hood vents seem to work, we're going to go even further and cut out the big vents on the fenders. Then all the vents on the sides, as well as the gas cap, are next in line, etc. etc. All these cuts will make the 599 flex more, and thus, if my suspicions are correct, faster. :)

I also bothered to weigh my car for once, before and after the modification. I've now got both the PN double-A-arm front end AND the Reflex top cover, so the chassis is pretty dense and only the Lexan window is bringing everything in at 123.0g without batteries.

Cool news is, the hood vents cut out 0.5g so now we're actually at 122.5g. Plus batteries, I'm sitting at about 169.5g which means I need to add a little lead to the bottom of the car for big races (170g).

More to come! Hopefully next time I post I will have the laptimes to back up this little experiment. :)

MR-03 Chassis Configs: Stock Black vs. SP Grey

color0 — Sun, 29 Jul 2012 23:21:53 GMT

Hi again after another break, everyone. :) For the past 2 months I've been switching back and forth between the grey SP chassis and the stock black chassis on my MR03 -- which covers both Stock and Mod class racing -- and I think I have enough data to report now. But especially since this seems to be a somewhat controversial topic with mixed results, I can only present my own impressions and it would be great if you guys and gals reading my blog could respond with your own. :)

So first testing started with the stock black chassis, which I've posted about before:

This setup, reverse-kingpin and all, is decently quick and forgiving to drive, but I did notice that it lacked steering. So, I cut the chassis tabs and popped on the PN Double A-Arm again, and that is our new baseline for this experiment.

(Don't forget the 1 degree lower arms! Necessary on the MR03.)

My baseline setup follows.

----------------

Front Suspension:
PN Double A-Arm
Camber setting 0deg
1deg camber lower arms
Purple springs
Preload/height: make lower arms flat on bottom, then lower 1/2-turn more
Total camber: Almost 2deg
AA +0.5deg tierod (double A-arm specific tierod)
Total toe: About -0.5deg (toe out)

Rear Suspension:
PN 98mm LCG V4 motor mount
Motor in lowest position
Axle height: #1 eccentric with # facing down (axle in raised pos.)
PN G10 #3 T-plate
PN Alu T-plate mount
PN Tri-shock: Blue side springs
PN Top shock: Green main spring, MR02 Purple rebound spring
Ver. 2 tri-shock mount (lowers inboard mounting of side shocks)
Raised outboard mounting of side shocks 0.5mm
Kyosho 15k grease on all shocks

Drivetrain:
PN 70, 80, or 33t
Geared at 14/53, 13/53 or 9/53
PN Gear Differential
3x2 AN0113 FET

------------------

So, what gives? Honestly, the black chassis is impractically fragile -- you do one too many rounds of maintenance and a screw hole WILL start to strip. Then you need to save it with whatever methods you have (vaseline/epoxy, etc.) and eventually all your screw holes will be partially made of adhesive lol. The stock black chassis also has a weakness on the top cover, you install anything to that top cover and it will bow outwards, letting dirt into the electronics compartment of the car. Tri-shock mounting to the black cover is a nightmare since screw tension will raise or lower the mounting point! :eek: And of course, installing batteries in an older stock black chassis will noticeably bow the chassis as well. It's just a very flexible part.

That said, the flex that the black chassis provides makes it fast. On low-grip tracks, the MR03 has no weight to warm up the tires so the flex helps generate grip. In Mod, the flex also slows down the car's reaction time, so if you're a twitchy driver it staves off a lot of traction rolling.

So, fast and forgiving -- the only problem being the complete lack of durability. A possible remedy for at least the top cover is the Reflex replacement top cover, which I have in black (sorry no installed picture). I threw it on for the next test, and noticed 2 things:

1. Precision is great. I suppose what they say about rigid suspension attachment points is true, the car does feel more consistent.

2. Chassis got stiffer, and front end traction dropped. The Reflex top cover raises CG and stiffens up the black chassis, so it's either the extra roll or the extra stiffness that's reducing the car's total grip. More on this later.

My rate of traction rolling, however, increases with the Reflex top cover, and that's more than likely due to the extra CG height (the Reflex cover adds 2g up top) which I normally don't lug around. I haven't changed the setup yet to match the Reflex top cover though, because at this point the experiment still needs to be controlled. :)

To diagnose point #2 above, I then overhauled the car and replaced the black chassis with the grey SP chassis and now the car looks like this:

As you can see, the top cover is back to bowing out with the tri-shock installed -- this is with barely enough torque on the screws to keep the tri-shock mounting plate secure! But at least it's stiffer than the black chassis and bows out only about half as much.

And what of traction? It's about the same really -- and without an extra 2g of weight up top to move around the only way to induce this car's traction rolling last Saturday was to yank the steering and brakes at the same time, which thankfully is not necessary in my car. Again, the suspension and drivetrain setups did not change, so I could see what the chassis swap/mods themselves do. It is another experiment entirely to change the chassis and then optimize around it. A good one, yes, but I haven't gotten there yet.

At this point, it's worth testing the final combination of grey SP chassis + Reflex top cover, and then see if it miraculously makes the car better, or worse (which is what I think will happen). Yet I've seen the grey chassis + Reflex cover combo work for several very fast drivers, so it will be fun trying to figure out how to make these different combinations of chassis and top cover work for me. :)

Late Report: Tekin 1/28 Setup

color0 — Wed, 30 May 2012 06:34:16 GMT

Dear readers,

My apologies for dropping the ball the last couple months -- it's been another helluva school term and things are only winding down just now!

So, the next couple weeks are going to be a little bit of recapping of things so you can see where I've been (Mini-Z wise) and where we're going towards as the summer season approaches. And to start that off, I kept some pictures from the Tekin race in March that may prove helpful for those new to Mod racing on low-traction tracks.

Here's my pit! Nice and clean. My pit setup is finally converging on something efficient I think, I've got my parts boxes on one side, tools on the other, chargers up front and radio in my lap. :)

My Mod setup is also starting to come together as of AFTER the Tekin race, lol... so count these as "before" pictures.

At the Tekin race I definitely ran into some problems with grip... the PN X15's kinda glazed over on the Inside Line track and the reverse kingpin keeps them cool, unlike the double A-arm suspension which warms up tires (sometimes to the point of overheating). Going to Orange springs in the front improved front grip at the expense of rear grip, and I ended up tucking into the inside rail many more times than would be ideal.

And *that* problem should be solved by not using the older-style PN 98mm V4 LCG motor mount (pictured here on race day), which frees up the rear end and makes it slide. The looseness helps on entry steering, true, but there's no stability for mid-corner corrections and no corner exit speed when I drive with this motor mount because the car's not 100% hooked up. It's 95% of the way there, maybe, but not 100%, and it was killing my performance on the fast, flowy layout when I was already way down on power compared to everyone else. So to get more grip, recently I've gone back (again!) to the carbon fiber "reconfigurable" motor mount, as I can definitely feel that the rear end is more hooked up with that mount. I think that for me, this is going to be the way forward and I can even personalize the rear end behavior to my needs by cutting custom lower plates for the motor mount.

So there it is -- my half-baked setup from March. The biggest problem with this car during the B Main was that I had grooved the front X15 tires and they REALLY didn't like that. Now that I understand that better, as well as the practical limitations of my Stock-based setup, my Mod performance has been getting better and I think I can start aiming for the A Main at big races.

Next post, I'll go over the new Mosler body that I put together for this race (which is good, unlike the chassis setup) and detail out the quintessential modifications that should be done to extract the best out of the body. :)

Consistency Wins: Using TH. SPEED to Tune Gear Diffs

color0 — Mon, 20 Feb 2012 02:59:17 GMT

One of the curiosities I've encountered after making the switch in my car from ball diff to gear diff is how the instantaneous power delivery causes a lot of problems with my setups -- setups that have been honed very carefully for the smoother power delivery of a ball diff. What happens? Well, in my case, I get a bunch of spin-outs on power:

[Wall] <-- [My car]

Since my setups tend to emphasize turn-in oversteer and powering out of the corner before the apex, I tuned quite a lot of steering into the overall setup so that even with some ball diff slip, the motor power would still break the rears free just a tiny bit to rotate the car around the apex and fire it out. This setup strategy relied heavily on PN Racing's Limited Slip Spur Gear in the ball diff to lock the rear axle on power, so that the rear tires would actually slip a bit, but not too much. If only one tire unloads, there wouldn't be any rotation, but if both tires slip too much then the oversteer will just put my car into the wall.

So I've had my setup pretty well-tuned for a while when along comes the new PN Gear Diff, and the moment I put it in I notice that the power delivery is both instantaneous and strong. The acceleration off the line is insane, but if I had any semblance of motor power (say, a PN 33t or an Atomic Chili) then all of a sudden, corner exits became pretty hairy. Thanks to the design of the teeth on the gears inside the diff, the PN Gear Diff locks quite strongly when you hit the gas, and that's the reason why.

(Wikipedia image)

When you apply a torque to the spur gear (blue), it transfers to the spider gears (green); the spider gears then apply that force to the side gears (red/yellow), but there's a catch:

(Wikipedia image)

Because of the shape in the gear teeth, when you mash two gears together they actually apply a force that wants to push their axles apart. The blue arrows show the force/reaction force directions quite clearly. :)

Now look back at the blue diff and the green spider gears -- if we apply force to the the green spider gears in the blue diff, they will actually force the red/yellow side gears outwards into the housing! This creates a significant amount of friction, generating a limited-slip effect that is quite a bit stronger than that of the PN LSD spur gear. The same thing that happens in the blue diff applies to the PN Gear Diff: the spider gears mash the side gears into the restrained sides of the diff assembly (Delrin nut on left, E-clipped bearing on right) and create friction, though of course a bit less since we do have a bearing in there.

So the PN Gear Diff locks strongly on-power and also happens to lay down all the power you give it immediately: this combo was killing the rear tires and killing my consistency, thus I reduced the Throttle Speed setting on my EX-10 Eurus in an attempt to gain back the forgiving feel that I used to have with the ball diff, and hopefully start being able to flog the car again instead of babying it around the track.

As I've written about before in "Transmitters Explained", the Throttle Speed setting available of many high-end radios pretty much limits the speed at which the actual, transmitted signal (that the car receives) matches the input from your trigger finger. This isn't to say the actual signal is slowed down -- this means that when you yank the trigger, the radio will tell the car something like,

"Hey dude, go 25%, now 50, now 75, now 100!"

rather than

"Hey dude, go 100% now!"

Basically, it emulates you having a smoother trigger finger than you actually do. :p The slight reduction in instantaneous power delivery approximates the initial slip that you get with a ball diff, thus the car WON'T burn up the rear tires at the tap of the throttle and I can avoid spinning out so much even with the stickiest tires money can buy.

Does it work? Absolutely. I took it to Kenon for a quick club race last night and for testing purposes, tried out three different TH. SPEED settings on my Eurus -- 100%, 75% and 65%. 100% is unfiltered throttle input: i.e. spin out city. At 75% I started getting the ball diff feel back -- I could hit the gas early without spinning out, the rear would rotate a bit before pinning itself down and firing the car out of the corner. And finally, at 65% the car was just too smooth -- the throttle was too dull at this setting to actually cause throttle steering, and so the car would have to wait till after it cleared the apex to apply power (I will admit it was quite consistent though).

From this quick experiment I would say that for KO radios, TH. SPEED ranges between 75% and 85% are about right for gear diff use as it seems the closest to replicating the slight slip and slight lag in acceleration that you get from a ball diff (there's still an advantage of course -- don't forget that the freer gear diff increases corner speed overall). At 65%, as I started to get used to the feeling I also noticed that it felt a little too laggy to be quick. Very smooth and very consistent, but a little too slow to be competitive. So that's the result I'm reporting today, that 75-85% TH. SPEED makes a gear diff feel a lot more like a good ball diff and generally combines the pros of the gear diff (corner entry, mid-corner speed) with the pros of the ball diff (consistency, smooth exits). I will be continuing tuning my Mod MR-03 to race with a gear diff as I love the indestructibility and tunable power delivery of the PN gear diff, now that we have this trick in our tool belts. :)

1 More Point! Box Stock Mini-Z Tuning

color0 — Mon, 20 Feb 2012 01:45:09 GMT

In response to the last article, mugler writes:

Quote:

Originally Posted by mugler

I think there is one more thing that can be played with which is screwing or unscrewing the rear shock shaft to its bottom post mount and changing rear droop. If you can comment on the effect, that'll be great!

Of course, he is referring to the stock top shock that comes with MR-02 and MR-03 chassis kits:

The way this shock is assembled is similar to the way a "normal" oil shock is assembled, with a shock shaft screwing into the shock end. The "piston", in this case though, is the head of the screw that you put through the shock "body" (open-ended, it's not a real oil damper) and then into the screw end. The shock "shaft" is short enough that if you screw it all the way in (as the cars come from the factory), you'll end up with a preloaded spring on the top shock with the cars at running weight, i.e. zero droop.

So what mugler is asking is whether or not loosening up this screw -- increasing rear droop to more than 0 -- will improve the handling; and I think that depends on the way you drive as well as the tires you're using on the car. If you're using the kit tires that come with Mini-Z's, I imagine that more rear droop might be quite welcome! Kit tires are not exactly grippy, except for a few batches of the newer cars. If you're using a good tire combo though that has good rear grip but not enough front grip, I imagine you would want to reduce the rear droop to zero. As I mentioned before in my "rebound spring" discussion, you would want the rear wheels to lift right off the ground in this case to put more pressure on the front tires, giving you more steering.

So in the case of Box Stock at Kenon -- which uses PN 25 Slick front tires and PN 8 Radial rear tires -- I imagine that loosening the shock shaft for droop will not be necessary, as we're always looking for more steering with this tire combo!

Box Stock Mini-Z Tuning

color0 — Tue, 31 Jan 2012 23:42:29 GMT

Box Stock is a Mini-Z racing class getting popular nowadays because of its low entry cost for serious racing action -- anyone can go out and buy an MR-02EX for $180, put in some AAA's and off you go! It also appeals to veteran racers because of the potential for even-performance racing: in theory, no one racer will have the advantage of the part-of-the-day cutting-edge upgrade, everyone will gravitate to the same gear ratio, same motor, same everything.

But of course, this is my technical blog we're talking about. ;) There are things we can do to a "Box Stock" car to make the car more enjoyable and predictable to drive, and therefore better. In keeping with the spirit of most Box Stock rulesets, I'm not talking about tweaking motors to make them faster or making the spec tires stickier via special truing tricks. These tweaks are simply going to turn a decent Box Stock car -- in my case, a FOB (fresh out of box) MR-03W-MM -- into a smooth-driving, beginner-friendly car suitable for battling other FOB Mini-Z's in one of the closest racing classes I've ever partaken in. :) I apologize for the lack of pictures in this post btw, but at least these tips aren't really requiring of detailed diagrams.

Step 1: Wheels and tires.

Depending on the track, tire tape and truing wheels and tires may be allowed to get the cars operating within a comfortable performance bubble (decent steering and no traction rolling). Almost no track owner I know of complains about taping the tires -- it's a simple matter of helping keep the cars right-side up. When truing is allowed on top of taping, I recommend cutting the tires down to something smaller but reasonable, say like 23.5mm. Truing too small is unnecessary (this isn't Mod racing) but not truing at all sometimes leaves the car too high = traction rolling. My Box Stock car runs at RC Kenon with a spec tire package, so I have trued the front PN Slick 25's to 23mm. My PN Radial 8's in the rear are not trued, just left as is. No traction problems even after several weeks thanks to the weak stock 70t motor.

Step 2: Run in the motor and bushings.

Sometimes Box Stock classes will allow for bearings to replace the stock bushings, and in those cases, that's fine. But sometimes they don't -- and in those cases that's still fine because the stock Kyosho bushings are surprisingly smooth once run in correctly. :) The procedure isn't rocket science -- pop those bushings into your stock wheels with mounted tires, and spin spin spin! I don't like to use polish with plastic bushings just because I might not be able to wash it all out, leading to eventual wear and slop. Just hone out the bushings a little bit with a natural break-in process. In the rear, I recommend gently running in the rear axle bushings and the motor on the bench: put the car on a stand and hold full throttle for 10-15 minutes or so. This break-in process helps the car run smooth and fast the very first time it hits the track.

Step 3: Check other sources of binding.

With Kyosho's build qualities, typically the only other source of binding is on the older MR-02 chassis, at the front kingpin suspension. Try to work the suspension up and down to free it up, but if that doesn't work then polishing the kingpins in a dremel will be the final solution. I also recommend flipping the spring perches such that they rest against the top of the chassis' "arms" -- a much smarter setup than stock, where the perches slid up and down the kingpins. Luckily, the MR-03 comes with very smooth kingpins and suffers no such issue.

Step 4: Lower the front.

Tuning theory as covered by myself and many others teaches that a little rake towards the front increases steering, and with no rear traction issues to worry about, a little more steering means faster. The MR-03 front suspension comes with one shim above the knuckles and one shim below -- move both shims below the knuckles to drop the front end about 0.3mm. At the same time (not applicable for all bodies), MR-03 chassis kits and readysets should come with an extra pair of shims: rules allowing, I like to lower the front clip with these (good for another ~0.6mm I believe) to add just a little more rake to the setup. For the MR-02 or 02EX chassis, it's possible to lower the front ride height by removing the preload shims on the front springs. You may or may not be able to get away with gluing them to the underside of the knuckle to use as lowering spacers. :D

Step 5: Add a little damping.

Some tracks will not allow this, but I would push for it as it makes all Box Stock Mini-Z's ten times more enjoyable to drive. With the exception of the unfortunate RML (Rear Mount -- Low) chassis configuration, all MR-02's and 03's come with a top spring in a crude tube damper assembly. Shove a significant quantity of thick diff grease (think Kyosho 30,000wt thick!) into this top shock, and you will have sufficient damping to significantly smooth out the rear end of your Box Stock car, making it a lot more predictable in corner entries as well as high speed corners. This makes the biggest difference for experienced drivers I think as we can see the chatter and intrinsically want it gone -- but for any driver of any skill level, eliminating the chatter makes the car more obedient to commands and IMO generally improves the racing action.

If you want to take this trick to its logical conclusion, then you can achieve roll damping too to complement the bump damping you just implemented. Pop the metal ball out of the end of your top shock, and find the thickest, heaviest industrial grease that you can get your hands on. Slather this grease around the inside of the plastic ball joint before popping the metal ball back in, then roll the ball around a bit to distribute the grease. Attach the shock back to your stock motor pod and notice that there's now a tiny bit of damping action when you roll the pod. Even that tiny bit of damping will reduce the chatter you get from these cars and improve corner speed just a tiny bit. ;)

With these little tweaks, my Box Stock MR-03 GT-R is not the fastest in a straight line, nor does it have the most turn-in steering compared to its competitors, but it is without a doubt the smoothest-driving car in the field and allows its driver to push it hard. At a recent club race at RC Kenon we held a hot lap challenge for the Box Stock class cars, and while most of the hot laps being laid down were in the 10.6xx and 10.7xx range, I was able to push my little GT-R to a single 10.0xx hot lap, turning in early, maintaining corner speed and not being afraid to lay on the throttle VERY early. That's really all it took, just five very slight changes to the car, fully allowed at Kenon, that took off more than half a second from the car's lap potential.

My final point in writing this post is that Box Stock class is a fine class for beginners, in that no tuning is expected, but at the same time it's the best environment to introduce the concept of competitive tuning -- here are the very limited areas that you can modify on your car, go play! -- without being overwhelming. Not only does doing so prime casual hobbyists for more involved and technically challenging racing, but it also educates, teaching basic mechanical sense and (hopefully) inspiring a "tinkering spirit" in a fun package deal. As such, I'm a big proponent of the class and I look forward to helping as many new racers as possible dial in their Box Stock cars and have an enjoyable experience their first time in Mini-Z. :)