Custom Gearbox

[Chir]

Greetings!

I'm trying to build a custom gearbox for an upgrade to an older vintage RC I have. I'm looking for a little advice.

The car has two independent gearboxes; one front and one back. They each have a motor mounted to the gearbox. The gearbox looks like this:

My goal is to build a new gearbox that will allow hold a 550 instead of a 380. I need to keep this general formfactor where the motor pinion turns an idler (input gear?), which turns the spur mounted to the diff. I'm not able to mod it for a center diff with a drive shaft without permanently changing the car, and I'm another goal is to do all this without any permanent damge so I can eventually restore it to it's full glory.

Rlaarlo makes a cheap diff for the Terminator, but it has a ring gear on it instead of a flat spur gear.

This is the perfect size (1/10), but the gear is wrong. Can I just replace that ring gear with a flat spur, or does that mess up the weight and balance? Or maybe someone knows of a diff this size that has the gear shape and size I'm looking for?

Any help would be greatly appreciated. I'm at my wits end and have spent too many nights trying to figure out what diff to use...

 

[CertifiedMike]

Welcome to RCTALK.COM!!!

I don't know anything about your car so I'll ask maybe a dumb question... Rather than trying to rebuild the gearboxes, which could be rather tricky, why not try to rebuild the motor mount portion and leave the gear housings alone?
Adapting a larger motor with adjustable mesh seems WAY easier than trying to custom build a gear box.

What car is this for?

I hear 'vintage' and 'restore' and then I hear 'bigger motor' and 'custom gearbox'.

You are headed in 2 total opposites of a build.
If you plan to resto this car, my suggestion is to follow thru eith that plan BEFORE you put a huge motor on it and destroy the whole the car entirely.

If your plan is to overpower your RC and to drive it at rocketship speeds and cut it up, mod it out to make it as fast as possible, do that then.

I can't see doing both tho.

 

[Chir]

So, back in the late 80's, I had this RC Car by Nikko called the Dictator. A while back, it was re-discovered in a box that hadn't seen the light of day in many years. We played with this thing a lot...and it showed. I set out on a project to rebuild. I pulled it apart and 3D scanned every piece of the car. Once I had scans, I built 3d models from them. I didn't need to, but I figured why not -- someone somewhere might benefit from these modes for a car they're trying to restore, so why not help. From here, I learned 3D printed replicas in Nylon plastic.

This one, I wanted to restore it to all it's glory. I recently finished that up and found I really enjoyed the whole project. Going through all my extra parts, I find that I have almost enough pieces to build another car. I just have to print the gearboxes. I figured that, since I already have the gear box designs, why not see how the car would run with modern electronics and bigger motors.

So yeah, it'd be easier to go another route, I don't disagree. But this sounds like fun to me. I'm learning as I go, but I'm tired of talking to AI to try to figure this out and figured I'd start a conversation with some humans.

When I originally started the first part of this project, I went to my local hobby shop to ask for some advice. I was told was I was trying to do was impossible they wouldn't even help me.

For the better part of the morning, I was driving this car around the same back yard I did back in 1987. Maybe the hobby shop inspired me to do what they said I couldn't do, but even better this time!

 

[CertifiedMike]

I love that you took the time to preserve and save the scans of these parts. It might be some years, but someone, somewhere will be most grateful for your efforts!

I guess my question is... are your prints going to be strong enough to hold the motor's torque and weight on jumps, rolls, impacts...
I am not a 3D printer I have no experience here... I'm asking what you think of your prints and if they can take the abuse you are going to be putting your car thru.
Same with your printed replacement parts... can they actually hold up to the abuse you'll be putting those parts under with a pair of 550 motors where 380's were originally?
Without specifics of each motor, I will assume that the 550 is as large a jump in weight, size and power as it sounds.

Its not impossible to do what you want here but its pretty impractical by the sounds of it.
You need to remember that not a single piece in your original car was designed to handle the rpms, torque, speed, power, weight and most importantly, your car is likely going to disintegrate upon first high speed impact.

I'm not trying to discourage you or anything. I'm just asking you if you REALLY need to build THIS car or if they wouldn't both be better off with a restoration with a faster 380 and better esc.
There are smaller motors and esc combos out there with insane power and RPMs!
Replace bushings with bearings, maybe a servo and battery hop up and I bet your cars would still be plenty fast, a BIG increase over stock still and would not double your car's weight in the process.
A pair of 550's over 380's will def need bigger batteries too.
With the extra weight and speed, your car will just become a wrecking ball when it hits a curb.
Since the curb is unlikely to give, guess what gets wrecked.

The extra weight will also mean rebuilding, improving the shocks, steering and suspension if its ever going to handle well at all.

You are not the first person to attempt to over-power a car. Almost everyone on this forum started or eventually attempted a build like this.

I did too.

The results are always the same... "its fun, its fast, and the car blew itself apart because it can't handle the speed and rpms I tried to push thru the car."

This is likely the reason your local hobby shop refused to help. Possibly compounded by the idea that they will not be selling you the dozen or so broken control arms, shock towers... on your vintage rc.
Lots of ppl told me Kyosho was a bad brand, need to move away from... coincidently, it was the same hobby shops that weren't Kyosho dealers.

If you've never overpowered a car before, maybe choose a different platform than a rare vintage car to learn with. There is a learning curve, there WILL be broken parts.
You CAN do this. I'm trying to ask you if you SHOULD do this or if the lightweight approach might be the smarter choice for these cars' longevity.

If you want a fast basher, back yard racer... there are plenty of decent, affordable options with TONS of parts support.
If you want to over-volt, over power, over-speed and curb durability test THAT car, I'll prob drop a similar warning about overpower... then I'll grab some popcorn, pull up a seat and watch the show too!

If you're STILL set on overpowering these Nikkos after that, go for it!

Don't get discouraged if not many ppl help with this project.
I am a vintage fan and I am also unfamiliar with your car. I remember Nikko of course but not many of their cars made it to the tracks I raced on.

I know a lot about car resto and modding, I'm happy to help where I can too. Nikko is not as popular as Tamiya, Associated... my knowledge is very limited on the specifics of your kit.

There are a few 3D ppl here who are EXCEPTIONALLY tallented and can help you with that side of things here too.

 

[CertifiedMike]

Btw, I am equally inspired by a plastic, pointed, crooked finger thats telling me "No" and "Can't"!!!

Vintage RC might not be as fast as tracks today but they also weren't groomed, glued, sifted, refined sugar glazed, ultra smooth mini golf courses that ppl race on today too!
Older cars were built differently to handle different surfaces... mainly, ACTUAL off road!!!

I LOVE that you are still running your vintage RC today!!! THAT makes me happy!!!

 

[Chir]

I appreciate your comments. It doesn't sound like I'm heading down the right path, so I'll stop and re-evaluate.

I'm not a very social person, so I keep my mind busy by building things that teach me stupid stuff. Last year I 3D printed a fully playing electronic guitar, this year I'm playing with RCs. It's just what I do. A year ago I had no idea what a differential was, and now I'm tearing them down and rebuilding them to make them behave the way I want.

I've restored many things over the years, and I appreciate the value of keeping vintage items vintage. I know I'm not the only one like that, so it was important to me that I have a set of parts that I can use to restore my car to all it's vintage glory. And when I say I've modeled the car, I modeled every single piece. Every part, spring, bolt -- you name it. All I needed was the front and rear gearbox, and to be honest, those were the easy parts and I could have stopped there.

When I got this far into it, I realized I was actually enjoying tinkering with these cars. So I decided to make a fork of these parts and build up re-enforced version. This way, I could keep the aesthetics and have stronger parts.

So I took the stock parts, like this gearbox half for the front --

and I did a lot of testing to see where I could re-enforce these parts. My final variation of this version of the parts were considerably stronger.

I also took the opportunity in this version to replace all the self tapping screws with machined screws that mate with a threaded heat press inserts melted into the plastic for strength. My neighbors think I'm crazy because I've been standing out in my front yard just driving my car into the curb to see where it breaks so I can re-enforce it.

This give me an original set and a stronger set. This is where I asked myself, what's the next step -- and that was bigger motors, modern electronics, and stronger parts. So it was that, or be done with this project and move on.

In February, my plan is to buy a small CNC mill and build a car with aluminum parts. I've been 3D printing for about 15 years now, and I've been wanting to introduce CNC into my tool set so I could build custom bolts and screws. This seemed like the next logical step once I've gone beyond the bound of what plastic (in my case, I've settled on using Nylon without carbon fiber or glass) can offer.

I've shared way more of this project than I intended to here, but I figure I might as well just wrap it up with this. I still have one more part that I'm trying to model, but I'm having a really, really hard time getting the geometry right. In the image below, I've got the rear spoiler roughed in, but I've been stuck here for a month or so... I'll eventually get it.

 

[CertifiedMike]

It seems like you have done more R&D than perhaps the original designers did even!
Very cool that you are back into the hobby again!!!

I think most of us here are a bit antisocial. This forum is full of ppl who love RC but hate FB and other social media platforms.

If you have printed a whole car and don't mind banging it up to test on, you may well realize your intended goals.
If you crack up a bunch of brand new stuff and learn from it, maybe can redesign from it... you may suceed where others have failed.
I would really hate to see you crack up your last 2 original gearboxes and have toss your car too.

As I mentioned, bigger doesn't always equate to better. I think you could really gain a lot of performance from upgraded bearings, motor/esc... without getting 'bigger' too.

I am currently building a 1987 Kyosho Optima Mid for track racing. I can't stress enough how much I appreciate your love for vintage.

I think you should maybe not give up nor stop. Rather, redirect your plans towards making your vintage the very best version that it can be.

I have rebuilt my entire car. I've used carbon fiber, race grade EVERYTHING!!! Its built for 2s carpet track racing.
Parts are still availible so its a perfect car for the track.

I have been building this car for over a year now... Tinkering, improving, impressing even myself with how nice some of these upgrades are.... I have absolutely loved this build.

The very same things I am recommending to you, I am also doing to my car. Bearing, brushless, radio, servo, hardware... ALL can give gains on an RC.

I also had this same car in 87 and raced it back then too. I still have my orig car(s) too.
This new build is SOO DIFFERENT from my orig cars and still so similar.
As I said, its been a fun and challenging build.

You are on the right track. You seem like a pretty smart person. I believe you'll get there.
Your car looks really nice in the pic! This is a really unique build!
I hope you'll keep posting!!!

Can you cut a slipper shaft for my Optima Mid with your mini CNC stuff???