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Ok, so I put a brushless engine (5.5) on a brat, RESULT: 15 minutes of fun a burnt gears!!!!! OUCH!!! I guess it was too much power. Or was it because it wasn't correctly mounted??? Still have to take it apart to see what the damage is. Has anyone put a brushless engine on their tamiyas without burning the gears? If so, what engines do you have installed?

Cheers!

that gearbox can't handle that kind of power. if it had a full thorp gearset it would have faired better but still 5.5 is too much for that old girl.
what happens is under extreme power the gearbox side spread and then the diff gears start to jump or chatter, a few minutes of that and it's done.

there is a thread on tamiya club about a mod that enables you to screw the diff together allowing more power to be applied.

Wow...the same thing will happen if you put a Keith Black supercharged Hemi motor in a Dodge Aries K-car. Even if you could doesn't mean you should.

HI!... I have a 6000KV brushless set-up in my 1986 Tamiya Bigwig. I've never had a problem running it. I've even run a 11.1 volt lipo in it a few times. It's hit over 80KPH (50MPH). I usually run a 7.4 lipo in it. When I rebuilt it I used all new gears and full sealed AVID ball bearings, and carefully deburred all the gears. I run just a touch of wheel bearing grease in both the front/rear gear boxes. Last time I tore down the gear boxes was last year and they still looked brand new inside. Been running it like that for over 2 years.

THE H.P FREAK wrote:HI!... I have a 6000KV brushless set-up in my 1986 Tamiya Bigwig. I've never had a problem running it. I've even run a 11.1 volt lipo in it a few times. It's hit over 80KPH (50MPH). I usually run a 7.4 lipo in it. When I rebuilt it I used all new gears and full sealed AVID ball bearings, and carefully deburred all the gears. I run just a touch of wheel bearing grease in both the front/rear gear boxes. Last time I tore down the gear boxes was last year and they still looked brand new inside. Been running it like that for over 2 years.

bigwigs drive train is a bit more stout then a frog/brat/mb/blkft gearbox.

THE H.P FREAK wrote:HI!... I have a 6000KV brushless set-up in my 1986 Tamiya Bigwig.

Heh...if this is your Bigwig build, I would hardly think it compares to a stock Brat with Froggy gearbox. Even the stock Bigwig gearbox was tons better.

http://www.rcuniverse.com/forum/m_9555430/anchors_9555484/mpage_1/key_/anchor/tm.htm#9555484

If that's yours, nice build, btw.

HI!... Ya that's mine. I have 3 BIGWIG's all together. I got sick and tired of breaking the 25 year old brittle stock plastic chassis's. So I built a custom all aluminum chassis. I still have to have it powder coated. (black). The other two are shelf queen's. I do run brushless in all my other vintage Tamiya's as well. Never had a problem.

So what you're implying is a 5.5T motor should be fine in a Brat...? I'm impressed with your own mods but c'mon man. Let's keep it real.

I believe you need the power to plastic ratio forumula which is something like the power to weight ratio for 1;1 scale, I have it around here somewhere, Ill look.
Id say rebuild it and try again. Take pictures

Coelacanth wrote:So what you're implying is a 5.5T motor should be fine in a Brat...? I'm impressed with your own mods but c'mon man. Let's keep it real.

HI!... Well I have a 5000KV BL in a Blackfoot. It basically has the same gearbox as a frog. It's got full ball bearings, and all new gears that were blueprinted. Only mod in the gearbox is a vintage (NIP) Thorp diff. It also has a plastic gear. Never had a issue with it.

I'm not saying the Tamiya's are indestructible. I'm say that most of their gearbox designs will handle a BL motor and lipo power. Prep goes along way to keep it together. Full ball bearings goes a long way, spend time de-burring everything. If you notice a ruff spot while spinning the gearbox by hand, go back inside and find out why and fix it. I find bearing grease helps alot in keeping the gears from shredding. Now if you take a brand new high power BL system and just stick it in a 25 year old stock RC car that has many hundreds of runs on it, then don't expect it to last long. Also longevity of the older gearboxes depends on what your settings are in the ESC. Just don't set it up for 100% punch control etc.

Fair enough...my experiences with a Frog & Thorp diff were quite different. Full bearings too. I can't remember what motor I tried in it, but it was pretty mild, not even as powerful as a 480 Gold, and no matter what, it sounded like a first-timer on a stick-shift: If ya can't find 'em, grind 'em.

slapshot1979 wrote:I believe you need the power to plastic ratio forumula which is something like the power to weight ratio for 1;1 scale, I have it around here somewhere, Ill look.
Id say rebuild it and try again. Take pictures

Take pictures of the gears? Let me know about the ratio formulas you mentioned, that would be much aprecciated! Unfortunately I am new in this and my experiments are obviously exagerated. So what would be a recommendable brushless motor for these type of gears. I hear lots of versions but still not sure what to install. I'm thinking of trying with a Robitronic 10.5 on a 35A esc. That should be enough power without destroying the car......I think.....LOL.

Thanks for all the posts!

From time to time an aluminum counter gear and diff gear show up on eBay. As a matter of fact they are on there now as of this post.

Theres also a mod you can do to keep the gearbox halves together. I forget what it entails exactly though. Something to the effect of putting a bolt through it.

Ok, took the brat apart and its wasn't the gears or diff in the end! They were fine! It was the axles that wore out and were turning freely in the wheel conection. THe axles are not T bone shape but have a hexagonal shape at the end so its rounded off. I don't know if that was clear...... Anyway I ordered new axles and hubs (t bone this time) and will install a 10.5 engine and voila that should do the trick! Will let you know!

good luck, thats still alot of power for that poor little gearbox.