2 speed transmission idea

[jeremy_n]

I like your idea capt.

The only problem I can think of so far is how to disengage first gear after second gear is engaged. But yes that is a good idea. I was thinking a centrifigul clutch would work best. When I was in the pit crew for mini road bikes, we used centrifigul clutches on the machines because the way you sat on it, there was no way to shift using a clutch...
Anyways, I would really like to help with this idea. I think it would be worthwhile and having been thinking about it for awhile now...
Those people who say that the weight of the whole system would make it not worthwhile have a point but I believe that if done right it could mak a big difference.

[Capt.ArD]

thank you for the support

i lack the supplies and machines to try it, but i can offer a tip on how to disengage the first gear. i figure that if you had a one-way bearing, once the second gear kicks in, then the wheels will outspin the first gear pinion. dunno if that helps.

imagine a mountain bike. pedals catch the chain going one direction, but not the other. the pinioin will drive the axel, but when the axel gets to the high rpms in second gear, the first pinion will not be able to catch and will just spin in idle.

size is the only issue i see. most of the parts can probably be milled aluminum, which probably won't wiegh down the car THAT much.

[sawhit4]

wow it seems as if everyone who is for this cant read. you say that we said that it wouldnt work. No one has posted on this forum if a two speed on an electric motor would work or not. anyone who says it wont just has to be shown a picture of an emaxx. What we have said is that there is no need for one and that building one that would actually fit in an xmod would be very very difficult.

Anyway now that thats out there lets look at capts idea. It would probably work but you would have to play with different types of springs to get it where you wanted. Also jon.jon wants to use a two speed in an xmod with larger tires so he can offroad. The connection made by the springs would be weak and might not connect if a wheel was stuck. Especially if he was using a locked diff since they are harder on the motor.

Also making something this small would require very precise machines. Remember not only does that have to work it has to spin perfectly true.

Oh and as for flaming others ideas, no one here is flaming anyone. No one has been rude or disrespectful besides some stuff from the people that are actually supporting this idea. The is a public forum. If they werent ready for positive as well as negative responses they shouldnt have posted here.

[viperdout]

Originally posted by sawhit4
wow it seems as if everyone who is for this cant read. you say that we said that it wouldnt work. No one has posted on this forum if a two speed on an electric motor would work or not. anyone who says it wont just has to be shown a picture of an emaxx. What we have said is that there is no need for one and that building one that would actually fit in an xmod would be very very difficult.

Anyway now that thats out there lets look at capts idea. It would probably work but you would have to play with different types of springs to get it where you wanted. Also jon.jon wants to use a two speed in an xmod with larger tires so he can offroad. The connection made by the springs would be weak and might not connect if a wheel was stuck. Especially if he was using a locked diff since they are harder on the motor.

Also making something this small would require very precise machines. Remember not only does that have to work it has to spin perfectly true.

Oh and as for flaming others ideas, no one here is flaming anyone. No one has been rude or disrespectful besides some stuff from the people that are actually supporting this idea. The is a public forum. If they werent ready for positive as well as negative responses they shouldnt have posted here.

I think the best way to do it would be to make it like a centrifical clutch, with a very long motor pinion. When the gear spins enough, it'll move out, off the bevel, engaging another gear which would go through a set of gears to get back the the bevel gear.

[Murcielago659]

Originally posted by sawhit4
Also making something this small would require very precise machines. Remember not only does that have to work it has to spin perfectly true.

This right here is where this project will be made prohibitively expensive.

[jon.jon]

If you know what your doing it wont be expensive

[jeremy_n]

I've been doing a little research... unless you've got free access to a really nice CNC machine the cost would be pretty high. Unless you're willing to spend $70 or $80 for a 2 speed tranny then I don't quite think it would work. I think what we need to concentrate on would be finding a cheaper alternative. I'm not syaing it's not possible at all, it's just finding a happy medium between cost, quality, and weight/size. I'm wokring with a couple of ideas, but nothing has really stuck out in my mind yet...

Check out this article though...it's pretty good. I find the drawings a little confusing, but if you think about it it all makes sense.

RCTek Article

Jeremy

[Capt.ArD]

that article is good. i think it is a similar idea to mine and probably works a lot better, especially if you want to offroad like jon.jon.

as for parts, the outer gear car be standard gearstock with the center drilled out. the plates to contact it ouldn't be too hard to make either. i bet any mill machine could do it, if you know how to make one. also, a lot of high schools have mills, and if you just get permission they'll probably help you out.

[sawhit4]

im not even sure if a large mill like one a highschool or local machine shop would have could do it. It would need to be very small and i dont think that most of those machines can do that. I think a mini mill like from sherline might be the best way to do it but at close to $3000 a pop they arent exactly cheap.

Also the people who run places like local machine shops dont know what your making or how its supposed to work. They just see a drawing and they make it. They cant say well since this is a two speed tranny i know that this should be here and that should go there so whatever it is you show them has to be exactly what you want.

[jeremy_n]

Sawhit and Capt make a good good point. Standard gear stock would work but you would need a quite detail oriented machine. But also we would need to have the drawings perfect in order to get it to work. It's great to have the ideas, and I think everyone here has great ideas, but we need to work on some specifics. Either today or tomorrow I'm going to start taking some measurments of the rear end of the chassis where the tranny would be.
Also, I've been tring to think of the material to use for the contact area for the second gear. I'm not sure if was mentioned here but someone had said to use sandpaper. I don't think this would work because a) it would wear down the inside of the gear, and b) the sandpaper would wear out pretty quickly. I think since the weight and materials we are dealing with are fairly small scale that some kind of rubber would work best. Maybe even some of the material from the XMods tires. This way it wouldn't wear down the inside of the gear but would be easy to replace when the rubber itself does wear down.
I think all of the ideas are really starting to make sense! Everybody seems to have really good ideas and people seem to be seriously thinking about this. I am willing to spend some money to make this work, but we need to solidify our ideas first. So, let's sum up what we have so far:

The basic principles is to use a centrifigul transmission. Any other kind of system would be too big and too heavy. So, the way this would work is there is a standard first gear the spins on a one way bearing. This means that when the motor is spinning the first gear the bearing acts like any other bearing, but once the clutch shoes engage the bearing it basically just works as a free floating assembly. The second gear is larger so the same amount of rpms=more wheel rotation. So while in first gear, the rpms rise and the clutch shoes move out until they press against the inside of the second gear. Once the second gear engages, the first gear just rotates freely without having an effect on the actual wheel rotation.

Now, as I was writing this out I've come up with a few issues. The motors we use for the XMods rev up to max rpm almost instantly. So the first gear wouldn't be engaged very long. I'm not sure if this would actually be an issue, because the short amount of time that the first gear is engaged would probably be enough to get it up to a great enought speed that when the second gear engages it would basically just take over for the first gear and continue rasing the speed.
Also, before we send this out to any machine shop we need to determine exact gear sizes to make sure that we are getting the most out of the system.
Later on today I will be breaking out my old engineering books and trying to figure out some gear sizes. Also I will try to get some measurments on the rear end of the chassis and start to mock up a non rotating assembly.

Anyways, we seem to have the right group of people working on this so let's get cracking and see what we can do. I definitely think we're making some progress. I should be back later on today or first thing tomorrow with some of the calulations i've come up with.

Take it easy everyone.
Peace
Jeremy

[jeremy_n]

Okay, here's a crude drawing of the space we have to work with.

Red = Space for tranny
Blue = Black shock/rear plates mounts
Green = Front of motor

[Capt.ArD]

ok, if what i imagine this thing's size to be, then 19mm should be enough. i have to check with some friends to see how small the high school's mill can go, but if it works, ill be glad to have a prototype milled. i'm good for ideas, but when measurements and specific designs come in, i fail... can sombody else try and do that?

yet another thought:
has anyone seen a governor(sp?) for a steam engine? it operates on a similar idea as a centrifugal tranny, but has fewer moving parts. that may be an easier thing to make. explaination later.

[jeremy_n]

Hey capt,

I am currently woking on some drawings right now. I think they should work. The only thing is the motor needs to move forward in the car if we want to keep all the rear components in the same place. It really shouldn't be a problem but I have to think about it for a bit. Anyways hopefully by the middle of the week I should have some preliminary drawings. I'm starting to think that this could really work....

Anyways, keep thinking on it and we'll see what we can come up with.

Jeremy

[Capt.ArD]

ok, im working on a slightly different idea on the side, one that i can do at home. I got a question about some parts.

motor shafts, can i geat an armature with about 10mm extra length on the shaft? where + how much?

also, pinion gears. i heard of pinions with different numbers of teeth, how many and how few teeth can you get? are the gears the same diameter, even though they have different numbers of teeth?

hopefully, if i can get these parts, i'll be able to build a tranny that won't require power machines and alot of $ to make. don't give up on that one though, jeremy, that is a much better design than my new idea.

[Capt.ArD]

btw, is there an easy way to cut key grooves in motor shafts? i need to get a metal collar to slide along the shaft without rotating or slipping at all... thanks for the help.