[WIP] WV Golf Rallye G60

[miguev]

Hello... long time no see 

I'm slowly getting back to Technic, and got a couple new things to try: BuWizz and SBrick+ ─ in this MOC, I'll try pushing the limits with BuWizz to drive a heavier model faster than Li-Po + SBrick can.

The model of choice is this VW Golf ─ a popular sports car around my early teen years:

 

I'm not entirely sure which model exactly is this (please let me know if I got it wrong) but it looks like it's the 1990 VW Golf Mk2 Rallye G60, indeed the Nicest One Left. 

 

Scale will be roughly 1:10 (1:9.72) as calculated using this blueprint (closest match I could find) and Sariel's model scaler assuming 62.4mm tyres.

 

Initial goals for this model:

• Fast enough to be fun to drive and appreciate suspension at work.
• 4WD with either central differential or separate front / read drive trains.
• Front and rear independent double wishbone suspension.
• Caster angle (for real this time, not fake like in my BJ Baldwin trophy truck).
• Reasonably good looking body work, but lightweight.
• Reasonably good looking interiors, with only front seats like a real rally car.
• Openable bonnet and boot.
• A few lights.

Stretch goals, harder (maybe unfeasible) at this scale:

• RC 2-speed gear box.
• Automatic 2-speed gear box.
• Working steering wheel.
• Openable doors.
• A lot of lights.
• Brakes, at least on rear axle.
• McPherson front suspension and dragged rear axle, like the real car.

I'd like to hear from the more experienced among you, if any of the above is a bad / silly / unfeasible idea. Or if there is something else I should try, or take into account.

 

For the front axle, I'm using 32495c01 wheel hubs (from 8070) to keep ground clearance at around 2-2.5 studs. Made a fairly compact axle, to be able to mount it at an angle, with a slightly illegal alignment (off by 0.4 mm) to achieve a small caster angle of 5.7º ─ is that too little for this kind of car?

 

Drive train is not finished yet, and for now I'm trying the easy way: separate drive trains for front and rear axle, with 2 L motors per axle geared up 1:3. With just the front axle so far, BuWizz is able to drive this at a decent speed with a bit over 1 Kg. of load (model weighs 550 g. and I tried it with a 500 g. package of flour on top). I'm hoping there will be enough power to drive around 1.5 Kg. of model with 2 axles like that. The thin 3L LBG liftarms between suspension arms and steering links are holding a round 1x1 plate to keep the CV joints to pop, otherwise they come apart under stress.

The not-so-easy way I have in mind would be 2 Buggy motors going to a central differential, maybe with a 2-speed (RC or automatic) gear box in between. I have not yet tried anything for this.

 

So far I have a chassis built with bricks, half of which is just scaffolding for the first drive test. Since I wouldn't have decent photos any time soon, I built in MLCad the part of it that is not scaffolding and took a few snapshots:

 

 

A few more snapshots in a Flickr album. Looking forward to reading your comments and suggestions 

[Leonardo da Bricki]

A promising start, and welcome back to Technic! Concerning the feasibility of your ideas, McPherson front suspension is near impossible, as is an automatic gearbox (as far as I know). Brakes on a dragged rear axle would be possible, as are opening doors. From the servo motor's current position, a working steering wheel would be difficult to implement. An RC gearbox is definitely possible, but you will probably need to have one drivetrain, and if you want good performance, especially off-road, don't bother with a central diff, unless you are able to lock it.

Hope this is helpful!

[VKTechnic]

Suspension like that is totally feasible, did something similar with a Datsun 1600SSS rally car in the same scale. Here's one of my prototypes:

Granted, I did take apart shocks to make this work, but it's not too difficult and no pieces are harmed. I've got an LDD and more pics here if you're interested.

EDIT: I skimmed over the part where you mentioned 4WD. I'd be very impressed if you could squeeze that in at this scale, you're already packing quite a bit in there. Hope my post helps anyway

 

[Lucullus]

There is no need to use a central diff, if you want to stay as authentic as possible. The real version of this car uses a haldex clutch in front of the rear axle to transmit torque. Later, they used rigid coupling to connect the rear wheels in the competition version because the haldex clutch causes bad handling characteristics (unpredictable oversteer).

[move5]

first of all, a steering unit like that will create either toe in or toe out when the suspension is engaged, just like 8081 model.

Edited April 10, 2017 by move5

[miguev]

Thanks guys! I hear you all against central diff so that's out.

VKTechnic, your rally car had the same wheels and distance between axles as mine, but was about 4 studs narrower. Was the real car just as narrow or did you have some other reason to make it so? I had seen your axles, and liked them, but I'm hesitant to take shocks apart (done it already) for this model; don't such custom-made shocks (specially yours in the rear axle) tend to fall apart more easily under stress?

I did worry about toe in/out but wasn't sure how bad it'd be, does it realistically affect handling? In any case, I tried to get rid of it and came up with this:

 

[VKTechnic]

8 minutes ago, miguev said:

VKTechnic, your rally car had the same wheels and distance between axles as mine, but was about 4 studs narrower. Was the real car just as narrow or did you have some other reason to make it so? I had seen your axles, and liked them, but I'm hesitant to take shocks apart (done it already) for this model; don't such custom-made shocks (specially yours in the rear axle) tend to fall apart more easily under stress?

The dimensions were based off a blueprint, so yes the real car had roughly the same proportions. The prototype rear shocks did fall apart, but my final ones were much better made:

 

[move5]

nice work! I am certainly following your posts.

[TechnicRCRacer]

@VKTechnic Do you have more photos of your latest rear axle (up there)? I am trying to reverse engineer it.

[VKTechnic]

1 hour ago, TechnicRCRacer said:

@VKTechnic Do you have more photos of your latest rear axle (up there)? I am trying to reverse engineer it.

There's an LDD file in this Brickshelf folder, that's all I have I think.