TOPIC:

Hi All

First post, and straight in with the questions!

Back in the day I had both XR311 and Cheetah models. Long gone now and I'm scouring eBay for rebuild-worthy replacements.

I'm convinced I recall reading an article in one of the magazines of the day about someone converting an XR311 to 4WD, but no amount no googling has found any reference. I'm quite keen to have a crack at something similar, does anyone have any info at all?

Thanks
Andy

That sounds like quite an ambitious project. I'd like to see it if you attempt it.

First of all, welcome.
Sounds like a very interesting project (talking as a fan of modifications) - and in line with the real scale car.
Couldn't give you any tips myself though. Never seen a conversion like that.
To some Tamiya purists it would be a bit sacrilegious to do such a thing though.

Edit - might be easier to adapt the body to fit on a 4WD chassis...

Edou wrote:

First of all, welcome.

Thank you.

Edou wrote:

To some Tamiya purists it would be a bit sacrilegious to do such a thing though.

I know, but I can't help it. Standard cars were made for modifying... Besides, if I recall the steering and suspension could use improvement. And I'd probably like to give it an ESC, and replacing those horrid brass bearings with rollers would be nice... That's just from memory, I imagine the list could go on.

Edou wrote:

Edit - might be easier to adapt the body to fit on a 4WD chassis...

That's a good point, and I sort of considered it, but then it wouldn't be quite the challenge. I do like a challenge.

I'd really like to find an original 70s car and modify while restoring, but the temptation to buy a new re-release is gaining momentum. EBay needs to come up with something suitable quickly!

The rerelease has the same model number so that makes it a bit more justifiable getting one.
It would be a better option than a bashed up old car with a bunch of parts missing.
Personally, I'd be very interested to see this project. Hope you get ahead with an idea of the design.
I'm a purist when it comes to shelfers but for runners anything goes (as long as the core 's still Tamiya)...

Welcome on board, andystev

It's an intriguing possibility ... but having built an XR311 & a couple of Cheetahs recently, it's difficult to see where you'd find the space to do it without losing a lot of the original features, even if you have some mad fabrication skills at watchmaker scale...

I guess it's theorectically possible to get drive out of the rear gearbox via another bevel gear off the crown/spool gear (?) & a driveshaft up the centre of the car - but that would mean the servo for the speed control, battery, radio switch and steering servo all need relocating, which means modifying the chassis & inevitably the underside of the body & the interior ... then, what do you do with the drive at the front? Even if you could make a gearbox small enough, all the steering gear is where it'd need to be ... I'd love to see it, but phreow, it sounds difficult....


Using an alternative chassis is an option.... wheelbase at 250mm for the Cheetah & 260mm for the XR311 isn't the problem, it's the width - only 163mm. I would think if you want to stick with Tamiya you'd be needing to look at extending a modern, very plastic M- chassis to get drive at each end, and you'd need to do some hellacious hacking of the underside & interior of the body to make it fit.

I can't help thinking that the "easiest" way (apart from on the wallet) would be to find a suitably old, chunky metal chassis, modify it so the length/width proportions are correct, then making your own XR311 body to fit - it's mostly flat planes, after all...

I'd thought about doing that with a recent XR311 project to "wow" the audience, but like Jonny said, as much as it seems simple to get drive from the back to the front (Even looks like Tamiya may have been thinking about it for the original release) & yeah you can move the electrics about, it really isn't that simple.

The problems will come doing the front end - 1st question is how to do the steering? - there's no where else to run the trackrods at sensible angles, other than where they currently reside, to make room for a front 90 degree transmission shift (I was planning go diffless for simplicity, using TL01 diff bevels). I'd thought about mounting the steering mechanism in front of the front suspension assembly, but thougth it would look untidy.

Next, although you could get some small driveshafts between the wishbones, you'll need to come up with new/special C-hubs that would clear the shafts during steering/suspension movement.
Then, there is the problem of space required for UJs where the shafts meet the hubs - ideally the joint wants to be in-line with the kingpins & outer wishbone pivots.
Next problem is stub axles & hubs - how do you do the stub axles to keep the bearings in place? Kinda looks like new/special hubs as well...

The reason I abandoned the idea was that for me, the more bits you replace with "special" bits, the less "Vintage XR311" it will be, which for me, kinda defeated the object of the project - you may as well have just scratch built the car (Or bought M-chassis running gear) & plonked an XR311 body on it.

Have a look at my modded XR311 project. That was only special torsion bars, ballraces & body (+ a pile of repro parts) in the end, but it might give you some idea of how awkward these cars can be to do anything with - I finished with a sense of "Well, that was fun, but it was a lot of effort for not much gain"

I don't want to put you off, I'd be really interested to see someone go through with it (To see how they tackled the problems), but I often make up special bits & scratch builds (See also my 25th scale carbon racer project) & I'd come to the conclusion that the 4wd XR311 idea was just too much effort & modding

Edou wrote:

The rerelease has the same model number so that makes it a bit more justifiable getting one.
It would be a better option than a bashed up old car with a bunch of parts missing.

Indeed, I may well be coming to that conclusion too.

We're all having similar thoughts at least! The front end is certainly the interesting bit. I've kind of got an idea how to sort the drive out, and, yes, it'll need custom hubs. But without a car to look at I'm struggling with steering. That's why I'm on the hunt for that article. It's driving me nuts that I can't find it! I seem to recall thinking something like "what a neat solution!" at the time.

Once I've got a car to play with I'll give autocad a dusting off and see what I can come up with.

Thanks for the thoughts, and the welcome.

I had thought about running the steering links straight into the sides of the chassis (Cutting holes/slots to suit) & do a rack & pinion type affair, so I could run a shaft (Possibly with flexible joints) to wherever I could remote-mount a servo in-line with said shaft. But like I said, too much effort & more non-original hacking/parts!