TRF 202x Shaft Drive 2wd

[Tweaky]

Hi, just like to share these pictures of my 2wd, 502x Hybrid. This has been in the back of my mind for a while but seeing Dave Burton’s DB1 conversion prompted me to give it a go. As I didn’t have all the Tamiya bits to hand I decided to build up a Schumacher SX3/Cougar Belt drive 2wd from parts I had. This was a great conversion, quite simple and with a minimal amount of new components, and it worked really well, even had an F1 grade driver using it for a while. Pictures of the Schuey conversion are lurking around in the 'I made this' section SX3/SV. Meanwhile I had accumulated a couple of Tamiya donor cars and set to work. This defo not straight forward as this time I did not want to cut the chassis. So plenty of 3D cad work later I ended up with a lot of new alloy components to hang the 201 front end onto the 502 chassis, a funky steering bellcrank had to be used as the servo needed to be kept well inside the chassis, again this worked really well and was from other Tamiya parts. Also a new carbon top deck had to be designed to stiffen the front end and topped off with a Proline 502x Bulldog shell.
As you can see it all looked rather sweet. So how did it go? Well rather dissapointingly, we tried it a few meetings and did some test day’s but couldn’t find a sweet spot with it and the conclusion is we are carrying far too much weight at the front. There is so much new alloy up front and the motor position is probably just too far forward, we could compensate with weighting the back down, but then the rear end geometry on the 502 doesn’t really suit 2wd car either. So after all that hard work, I’ve now shelved it and now looking for a 511 Belt drive to try the conversion on. I’m pretty sure this will be a better platform to base it on, as it will be closer to the Cat SX3 Hybrid, which I know works.
Anyhow, enjoy

[MHeadling]

What a fantastic job you have done there

The quality of the build/machining is top notch! Mr Tamiya would be proud!

Shame it didnt work out, how about flipping the motor and running a shortly lipo down one side.

Have a look at this website of Hiroshi Oda for ideas:

http://motogo-rc.blog.ocn.ne.jp/

[kidcongo]

That's quite the project and sad to hear it wasnt a winner. Maybe next put the front end of the TRF 502X on a TRF 201 to make TRF 501X.....wait a minute.....hmmmm

[Origineelreclamebord]

Wow, that's very classy looking for a prototype Very cool project! This car indeed has the weight very far forward - I think the suggestion to flip the motor and use a shorty could work very well - and it seems there's some spare room to move the whole slipper assembly+motor mount further to the back?

With this amount of work on it, it would be a shame to bin the idea (even more so because the Tamiya's part in (2WD) offroading is quite small).


I've got two questions about this project:
1. Do you have a video of this in action?
2. Why did you choose the 502 and not the 501/511? I would imagine the motor position+rotation direction would help rear bite on acceleration, and the belts will give slightly so the power delivery is smoother (=more grip again). It's the same thing I wondered with the DB1... why a shaft drive instead of a belt drive donor?

[Tweaky]

Many thanks guy's for your comments.

Unfortunately no video of it in action.

I like the flipped motor and shorty lipo ideas, defo help the balance.
Perhaps i should give the shorty lipo a go it would be fairly esy to do.

As for shaft drive, i just liked the idea of simple drivetrain and enclosed gearbox. Maybe it would of been better with the belt drive instead.

Regards

[Matt Butcher]

Nice work

Maybe make it something like this? http://www.oople.com/forums/showthread.php?t=113864

.

[Oval/offroadracer43]

That looks very cool. I did the same thing with my 501x.
I had to make it 2wd because the class that I'll run in is a 2wd class.
Belt drive is alot smoother.

[Origineelreclamebord]

Originally Posted by Tweaky

Many thanks guy's for your comments.

As for shaft drive, i just liked the idea of simple drivetrain and enclosed gearbox. Maybe it would of been better with the belt drive instead.

Regards

I thought about it when I saw the DB1... I thought they might have chosen for a shaft drive car because a motor mounted longitudinally will tend to twist/transfer from side to side instead of increasing the weight transfer towards the rear on acceleration and the front on braking (like a belt drive mounted motor or 'regular' 2WD gearbox).

Reducing the weight transfer to the front and back I thought would make the car's behaviour towards understeer and grip-roll more consistent and less extreme - as the weight transfer to gain traction on the rear for acceleration is not needed on high bite tracks, but things like grip-roll and understeer due to heavy weight transfer may be more pronounced, a shaft drive chassis might work better.

So my theory would be that a shaft drive 2WD layout like this 202X would work better on (even) higher bite than the belt drive 2WD layout of your SX3/SV. However, as I am a novice on this sort of stuff, I'd have someone check what I just wrote down

[kidcongo]

Originally Posted by Origineelreclamebord

I thought about it when I saw the DB1... I thought they might have chosen for a shaft drive car because a motor mounted longitudinally will tend to twist/transfer from side to side instead of increasing the weight transfer towards the rear on acceleration and the front on braking (like a belt drive mounted motor or 'regular' 2WD gearbox).

Reducing the weight transfer to the front and back I thought would make the car's behaviour towards understeer and grip-roll more consistent and less extreme - as the weight transfer to gain traction on the rear for acceleration is not needed on high bite tracks, but things like grip-roll and understeer due to heavy weight transfer may be more pronounced, a shaft drive chassis might work better.

So my theory would be that a shaft drive 2WD layout like this 202X would work better on (even) higher bite than the belt drive 2WD layout of your SX3/SV. However, as I am a novice on this sort of stuff, I'd have someone check what I just wrote down

I a perfect world, if the Tamiya engineers have done their homework, the rotational mass of the longitudinal motor in the 502X should exactly equal the rotational mass of the drivetrain (slipper, driveshafts, bevel gears, spur gear) turning in the opposite direction to the motor. In other words as the motor accelerates and decelerates the car never shifts weight left or right. I have tried this with my 502X, by holding it in my hand and gunning the trigger. It stays eactly flat left to right, but does pitch backwards on throttle like any normal car with 4 wheels and tires spinning in the same direction. This tells me that Tamiya achieved proper balance between opposing rotational masses with the TRF 502X.

[Origineelreclamebord]

Originally Posted by kidcongo

I a perfect world, if the Tamiya engineers have done their homework, the rotational mass of the longitudinal motor in the 502X should exactly equal the rotational mass of the drivetrain (slipper, driveshafts, bevel gears, spur gear) turning in the opposite direction to the motor. In other words as the motor accelerates and decelerates the car never shifts weight left or right. I have tried this with my 502X, by holding it in my hand and gunning the trigger. It stays eactly flat left to right, but does pitch backwards on throttle like any normal car with 4 wheels and tires spinning in the same direction. This tells me that Tamiya achieved proper balance between opposing rotational masses with the TRF 502X.

I understand - and I'm sure TRF did good work there. Of course though, this balance will be off once you take the forward driveshaft and the pinion that drives the crown/ring gear. It's probably the reason why on this setup we've seen driveshaft weights: to get (some of) that balance back.

The pitching backwards on throttle is only logical (you can't completely remove that, and you probably don't want to either), but theoretically should be less than on a TRF501/511X...