Scratchbuilt transmission?

[Duuuuuuuude]

So I'm nearly done with the second rebuild/redesign of my homebuilt crawler, and I'm really not that happy with the E-Maxx trans I'm using. Budget is a top priority (just got laid off a few weeks ago...), so I can't really go buy a better, smaller, lighter unit. Has anyone here built their own trans? I was thinking about constructing one using some E & T-Maxx parts, and also a few Revo gears I have laying around.

The E-Maxx trans is just too bulky, and I'd like to get it geared down some more.

I'd really like to hear some idea's or see some pics.

[ctrwannabe]

I'm sure it could be done I haven't seen it yet (maybe I haven't been looking in the right place) but you could try and sell it or trade it for a tranny that would work for you

[JohnRobHolmes]

Lots of guys built trannies back before we had many options. Maybe search for custom tranny?

[jetboat]

I was digging for pictures of mine... I used 1/4" lexan for the case and e-maxx/t-maxx parts. It worked ok but back then I didnt have a mill so everything was very rough. If I had it to over again (and I do) I will use aluminum and mill it out to fit.

[Robbob]

same here, 15 years ago when i built my first Bruiser Nitro conversion it was aluminum, a dremel, some blackfoot gears, schumacher gears and steel rods for drive shafts. it was scary and surprisingly functional.


found this site link in some old RCC posts, pretty neat proggy for helping to find gear centers when building a tranny. lot better then the nail + hammer + looks good there style i used in the day.

http://www.scriptasylum.com/rc_speed/_gear_calc.html

[EGRESSor]

i use savage gears for my trannys
strong and cheap and modul 1

the most used
http://www3.towerhobbies.com/cgi-bin...?&I=LXERG6&P=7

[Duuuuuuuude]

Thanks for the info so far. I tried doing several different searches and came up with squat.

For $3 I scored a small sheet of 3/16 aluminum to build a case. Figured that should be strong enough. Also after taking stock of my available gears I decided to go with 2 idlers instead of one. Kinda going to look like a miny Pete Jackson gear drive...lol. I also took one of the shafts that I'm not going to use and made one end pointy to mark the centers. What I'm concerned with now is that I may have to try and drill some holes in the hardened gear shafts for roll pins to help keep everything in place. I don't know if I'll be able to make the case as skinny as I'd like...

My gear selection isn't as diverse as I thought it would be, so any lowering of the ratio's from a stock trans may be negligable. I may have to experiment with them a bit, but I've already set aside the smallest input and largest output.

I've got a 65t motor on its way to replace the somewhat worn out 27t I'm using now, so going super low may not be needed. I've also got my choice between a 9 tooth or 13 tooth pinion. I think that little pinion with the 65t would give me pretty good results anyway...

On the plus side, all this unemployment has really free'd up my tinkering time.

[The1nonlyJ]

Can you post a pic of what parts you have?

I just did the same using the remains of my Tamiya 3 speed, an oldish nitro transmission and some odd tlt parts i had lying round.

[azvader]

Here's a couple of mine. Check here

Project Bula Buster

Originally Posted by JohnRobHolmes

Lots of guys built trannies back before we had many options. Maybe search for custom tranny?

They were fun to build but I agree with John Rob, too many options now.

[Duuuuuuuude]

Originally Posted by azvader

Here's a couple of mine. Check here

Project Bula Buster

Thats awesome, thanks! I was hoping to get my ratio to at least 3:1, but it seems the best I can do is slightly better than stock @ 2.7:1 without making it overly complicated. Ive got zero hobby shops locally, so I may have to hit the hardware stores and see what they have...or tear apart a couple of old cordless drills I have laying around.

[Duuuuuuuude]

Well I think I may have a winner here! It's at about 80% complete and appears to be a fairly decent build. I did have a bit of a goof though. The shaft I used for the output wasn't really the one I should have used, the diameter is too small for my driveshafts. Still, it should work. I also had an issue getting a couple gears to mesh properly (my fault) and had to shave down and recut one by hand. I also came up with a pretty good way to custom fit the "new" plastic gear to the existing metal one. Valve lapping compound. Dab some on the gears, hook a drill to the input shaft, and wind it up. After about 30 seconds of grinding and binding, it became as smooth as butter. I was fairly impressed.

Tommorow I will get the plate clearanced and cut to mount the motor, then install everything in my rig. It feels like its going to be pretty light. I'll be sure and post pics of the finished product.

[Duuuuuuuude]

It turns out there were two flaws in my design, one fatal, the other semi-fatal. The not-so-bad one was that there was too little room between the metal idler gear and the motor can. When going foreward and trying to climb something, the idler would shift over just a bit and rub on the can. I moved it this morning, and its better, but it brings me to the not-so-good portion of the build...

That shifty idler is too shifty. No matter where I bolt it down, it has just enough play to start binding when any amount of torque is applied to it. I may have to to a total reconstruction here. Bummer. :?

Now that I've built an ugly prototype, the next will be a bit more thought out. At best, at least for this time around, I just wanted to see I had the cognative capacity to do it, and I did, so I'm happy. Next time I won't eyeball everything...lol.

[Culetto]

You might do a google search for R/C Pullers also, i know they do alot of scratch built trannys and huge gear reductions.