M.p.h.

[GHC]

[edit]

Anyway, lets get started: I want to show you how to measure the miles per hour of your zz or any micro rc.

First measure 10 ft. somewhere flat in your house. Then time how long it takes for your car to go the 10 ft. Multiply the time times 10. Now we have x seconds.

(fractions)100 ft./x sec. times 60 sec/1 min times 60 min/1 hour. I fyou cross cancel the min. and sec. and multiply, you have 360,000ft./x hrs.

Now there are 5,280 ft. in a mile

1 mile/5280 ft. times 360,000 ft./x hours. cross cancel the ft. and you have 360,000 mi/5280 times x hours.

Divide 5280 times x hours into 360,000.

Helpful hint: if 5280 times x hours ends in 1 zero take that zero out and divide 5280 times x hours - 1 zero into 36,000. If 5280 times x hours ends in 2 zeros, take those zeros out and divide 5280 times x hours - 2 zeros into 3,600. And so on , up to 4 zeros.

Happy timing!

[Demon666]

damn i hate math! but good work.;)

[Zephyranthes]

Here is the easiest way to figure scale speed.

Here is the equation for scale mph and explanations why you do them for people how really want to understand the equation.

If you want to know the gear ratios with a 7 tooth pinion gear (K.I.T. Racing pinion gear), here are the ratios. I recommend using this pinion gear because it visibly improves speed. Light green 8.25:1 gears with a 7 tooth pinion gear becomes 7.07:1. Orange 9.86:1 gears become 8.45:1. Light blue 12:1 gears become 10.2:1.

Take your motor rpm. (3.0 = 30,000)

Divide the motor rpm by the corresponding gearing you have. 56(8.25:1 gears), 48(8.25:1 gears with 7 tooth pinion), 67(9.86:1), 57(9.86:1 gears with 7 tooth pinion), 81(12:1 gears), 69(12:1 gears with 7 tooth pinion), 31(4.57:1 gears), 26(3.95:1 gears), or 23(3.43:1 gears). This number is the ratio between the motor rpm and feet per minute.

Multiply it by 60 for you want miles per HOUR

Multiply it again by 64 for the scale of a ZipZap is 1:64

Divide by 5,280 for there are 5,280 feet in a mile.

(If you are using all ZipZap stuff, they have a chart for rpms at the site, but if you have 3.0's, different gears and stuff, then use this formula.)

I calculated my car to go 457 scale mph with a 3.0 motor, 7 tooth pinion gear, and 8.25:1 speed gears.

Note: This is the speed if there was no such thing as friction and other uncontrolled variables.

[GHC]

Zephyranthes thanks for your contribution to this thread and the idea of it.

Demon666 thank you.

And as for the 'I hate math part'. That was just to explain how i did it.

Basically all you have to do is measure the 10 ft., open up your comp's calculator,multiply your speed times 10, multiply that times 5280, and divide that into 360,000.

Hope this helps!

[Namuna]

Or....

Do a scale 1/4mile, which is 20'7"

Take whatever time and use it to divide by 900 and that equals your scale MPH.

If you get a time of 4.5seconds...900/4.5 = 200mph (scale).

That's the 'easy' math.
-------------------------------------------
Here's how I got to that simplistic equation...

At 1/64th scale, 82.5ft = 1 scale mile (because 5280 divided 64 equals 82.5)

A scale 1/4mile is 20feet 7inches.

Then you run your car on that 20'7" run and time it. Let's say 4.5 seconds.

If it takes your car 4.5seconds to go 20.625feet (same as 20' 7"), then how many feet (represented by x) do you go in 3600 seconds (1 hour)?

A little Algebra says 4.5x = 3600*20.625
4.5x = 74,250feet
x = 16,500feet

So your car can will travel 16,500feet per hour (REAL distance)
- or 200mph (16500/82.5, scale mph) Scale.

The 3600*20.625 is a contant (74,250) and to find the 'scale mph' that number is divided by 82.5 = 900

Seems almost TOO easy, so if anyone can spot errors in my logic, please feel free to point it out!

[GHC]

Great Job Namuna. That is the way to find M.P.H. to scale... so this is what they did on zz.com? intersting.

To add to my point, it doesn't necessarily have to be 10 ft. As long as you multiply it to equal 100. (ex. 25 ft. times 4)I said 10 because I thought it would be more convinient to most people , because you may not have a big space to measure. My original equation was 100 ft.

[Namuna]

Originally posted by GHC
That is the way to find M.P.H. to scale... so this is what they did on zz.com? intersting.


Mmmm, not exactly. ZZ.com has it as...
Feet Per Minute * 60 = Feet Per Hour
Feet Per Hour / 5,280 = Miles Per Hour
Miles Per Hour * 64 = Scale MPH

Not to mention their method doesn't take into account any kind of real world conditions or load.

My way is SIMPLE...Just divide 900 by the time (in seconds) when running on a 20'7" stretch. That's it, that's your MPH (to scale). My way calculates from ACTUAL distance traveled at a certain time (so this is actual scale MPH)

While 10' is probably more convenient to folks, it's NOT a good indicator of actual TOP SPEED...10' just isn't enough for these little demons to get to their top end.

If anyone is interested, I can create an Excel spreadsheet and you can plug in WHATEVER distance you decide to use (10ft, 20.625ft, or whatever) and it'll automatically churn out the scale mph, based on runtimes.

[GHC]

kool.'Not to mention their method doesn't take into account any kind of real world conditions or load.' That makes a lot of sense, because i was wondering how it could be going 174(if i recall right) with a stock, out of the box zip.

As for the spread sheet,thank you but i wont be needing it. As you said if anyone asks though.

Anyways, thanks Namuna.

[GHC]

WOW! its a great honor to be in bit science,especially since ive never done a real mod. LOL. Anyway thanx to whoever moved me.

[noobguy]

to be exact, a scale mile is 20'7.5". here is how:

1/4 mile = 1320 ft

1320 ft/64 = 20.625 ft.

But that is in decimals so you have to convert from decimals back to the unit system.

so .625=x/12........and x=7.5 inches

i don't want to be picky or anything but this could affect your times by .1 sec which people in real life are really anal about sometimes ;)

[scottyboyfun]

There are websites with calculators on them for speed, torque, etc. Ill post when I find it again!

[Icedragonad]

This is the easiest way:

1. Measure a distance of 8 feet 3 inches.
2. Record how long it takes your car to complete the distance.
3. Take that time and multiply it by 10.
4. Then divide 60 by it. (60/x)
5. After that multiply it by 60.
4. The result will be your smph!

[syncronized]

Isn't the easiest way to measure your mini rc's scale speed is place it on a tread mill which measures in either km/h or mp/h. Mine is in km/h (cuz im from Canada eh!) and then just slowly increase the speed of the tread mill until your mini rc is running in the same spot. Then take that number (I got mine up to 4.1 km/h with a fresh 2.6 in my shen qi wei clone) and multiply it by 64.
~ 260 km/h

[Icedragonad]

What if you don't have a tredmill!

[syncronized]

Well....then....you're pretty much screwed! LOL

[charliebrown]

Here's how I do my calculations for ZipZaps, with the 6T pinion gear:

Motor RPM divided by Gear Ratio = Wheel RPM

Wheel RPM times Wheel circumference (which is 4.5 cm)= distance per minute

Distance per minute(in cm) divided by 2.5 = inches per min

Inches per min divided by 12 = feet per min

feet per min times 60 = feet per hour

feet per hour divided by 5,280= actual miles per hour

actual miles per hour times 64= scale MPH

[flatlander_14]

namuna, you need to make sure you zip is up to full speed before it crosses the start line because otherwise that is checking your scale 1/4 mile time, if you do it froma standing start then you are losing scale speed data during acceleration. just a note :D

[adamace]

or u could just spend 5 bucks on this....



http://www.radioshack.com/product.asp?catalog%5Fname=CTLG&category%5Fname=CTLG%5F006%5F008%5F003%5F000&product%5Fid=60%2D7530


and divide the result of mph by 64.