Does a crawler really need a tranny?
 

So ive bin thinkin over the last few days on makin a crawler from scratch. My Tmaxx is idea is out and a Emaxx might be the way to go, but i only have to get certain parts and then fab everyting else, which is fine to me. but then i got to thinkin do we need a tranny, could i not do a direct drive? have ur motor with a gear and then the so called drive shaft to the front and back diffs, just have a gear on it also, like the 1/8 buggies. this way even lower COG and less crap to deal with. should even get some nice gearin combos out of it too. another thing i was thinkin of, what about a disc break for a elec crawler ( either on or off ) that way u can take the strain away from the motor, if u have to sit there for a sec and think on how to do a obsticle. and last idea of the minute for me, do we really need big tires? could we not use stadium racers tires, they are smaller land just less mass to spin. well those are my ideas so far, let me know what u think of them.

Re: Does a crawler really need a tranny?
 

there is someone on this site that is doing something like your asking( i think) he is just using motors and gearing..can't think of his name right now, but if you go to the " what are you pimiping" post and you will see what im talking about.. also, i think its maxxzilla ( not for sure)that has his signature line saying something about using a diff there instead of a trans..not really sure how that would go...but i'll look around and get the names


edit- "ACE" has the gear deal setup and i can't find the person i was talking about with the diff setup in their sig line..i thought maybe it was Fishmaxx also, but didn't see it

Re: Does a crawler really need a tranny?
 

He has a "worm gear" setup.

And yes, big tires are a must. Big tires gives you more ground clearance under the axles which is important when crawling in the rocks.

Re: Does a crawler really need a tranny?
 

If you can build it without a traditional tranny then do it, but try to have a final ratio of 150:1 - 200:1 for it to crawl really well. If it's going to be a gas truck then I'd shoot for a higher err.. lower final ratio, like 300:1.

Re: Does a crawler really need a tranny?
 

ive bin looking for parts and ive come up the the GS Storm drive train, HardCoreRacing even uses it for a modified maxx. so im thinkin this might work. use the GS tranny( lookes like a diff without a covering) and attach a elec motor to it. not sure how ill get the gearing i want tho. and then use maxx diffs and tires i guess.

Re: Does a crawler really need a tranny?
 

people have made eletric 1/8 buggies that way so i dont see why you couldnt use it in a crawler. :D

Re: Does a crawler really need a tranny?
 

I think it's a great idea. Jason and I have talked about that before and I believe he may even be working on that type of set up now. You'll have to talk to him about it.
I just wonder how it will be on the motors. Will the motors be able to handle it? I saw someone do a similar set up and they kept frying the copper strands. Maybe he didn't build it right. Not sure!
As for the disc brakes. That is what I was thinking for cutting brakes. Not sure how it would work though.....yet.
I also think big tires are a must. You don't have to go super big but for rc crawling, I think 6 inches is minumum. I guess a lot depends on your clearances, wheel base and track width.

Re: Does a crawler really need a tranny?
 

My Clod has an 8 tooth pinion that gives a gear reduction of 48.75:1. This is a reasonable setup with 6" tires. To duplicate this gearing lets see what we need.

Assuming you use Emaxx axles with 3:1 gearing and a 9 tooth pinion on the motor. How many teeth would you need on the spur gear driving the driveshafts? The formula for gear reduction would be:
Gearing=(spur/pinion) x axle so solve for spur, this is:

spur=(Gearing/axle) x pinion or spur=(48.75/3) x 9 so spur=146.25

We need a spur gear with about 146 teeth on it. Assuming we are using 32 pitch spur and pinion gears we can find the diameter of the spur gear.

Pitch diameter of the spur gear: D=N/P according to my machinists handbook.
D= pitch diameter (a little less than the outside diameter)
N=number of teeth on the gear
P= gear pitch

N/P=146/32 so we will need a spur gear 4.56" in diameter. 8O

That aint a standard r/c gear, I'm sure you could find it through some other sources, and you could still mount the motor on the side of it to keep it low but building a chassis around it could be interesting but I aint saying it cant be done. Let me know if I am wrong about any of these calculations. Post some pics when ya get it done!

Re: Does a crawler really need a tranny?
 

Okay i did some callin around to the lhs and found one that sells the GS Storm kit, so i can get the parts i want now(tranny and diffs) i was thinkin the tmaxx diffs, but i heard that the bugies are a bit more durable, so im goin try them out. So next friday when i get the whole day off (sudden case of sickness :wink: ) ill be goin to get some parts and then hit the local welding shop for sum metal stock. by that time ill have a idea for a chassis. im thinkin of a 2 link setup, but not sure of that right now. im goin to try to keep this thing small but flexxy

Re: Does a crawler really need a tranny?
 

:? So are you using a tranny or not? :?

Re: Does a crawler really need a tranny?
 

goto www.racinghardcore.com then under products goto Traxxas. then look at the Mutant Maxx, that is the so called tranny im goin to use. its from a GS Storm 1/8 nitro buggy. with that thing i should be able to keep a low COG and still have torque to get over things

Re: Does a crawler really need a tranny?
 

Still confused as to how you are gonna get low enough gearing :? but hey, just let us see it when it is done!

Re: Does a crawler really need a tranny?
 

The 1 tooth pinion :flipoff:

Re: Does a crawler really need a tranny?
 

:lol: :lol: I forgot about that, thanks Zilla.

Re: Does a crawler really need a tranny?
 

Why cant you run a gear reduction box between the motor and the tranny?

Re: Does a crawler really need a tranny?
 

That's probably the only way he'll get low enough gearing without a compound gear reduction.

About the 1 tooth pinion. Don't you think that would sound a bit rough? :flipoff:

Re: Does a crawler really need a tranny?
 

A worm gear setup is an excellent idea, in fact you could even use a nitro engine if you used a worm gear setup.

Re: Does a crawler really need a tranny?
 

I thought about the direct drive also but came up with the same issue of getting enough gear reduction. I dont see any way of doing it without some kind of transmission. Thats why I thought that Scalehobbies trans would be perfect. $100 though? So yesterday I talked with our "nitro guy" at the hobby shop. I settled on a single speed conversion kit for the Tmaxx as well as the forward only settup. That gets rid of any clutches or slippers in the trans but still gives the gear reduction. I will machine everything and make a custom case to keep everything as compact as possible. Hoping it will be small enough to also use in a TLT crawler also. What y'all think about that?

Eric

Re: Does a crawler really need a tranny?
 

any updates on this project?

Re: Does a crawler really need a tranny?
 

Slow go here Cutter. I have all the gears for the trans. Now I just need time. Its hard to come by with a new baby. Might have some time to work on it tomorrow.