Drift chassis question

[Mechbuilds]

Okay front axle is done. And it's pretty rigid. 

It's a sad that the "wheel hubs" have a little bit of play. But i doubt it will matter during drifts. 

[Sariel]

An alternative to RWD, found in real RC drift cars, is to use AWD but with the rear wheels geared to rotate slightly faster than the front ones. Also, I wouldn't put a differential on the rear axle at all.

[Gray Gear]

When spinning the back wheels faster than the front ones, what makes sure the rear tires lose traction, and not the front ones? Usually most of the weight is in the back, so there should be more traction there.

The RC cars probably use tires with low grip in the rear...

[ukbajadave]

RC drift tyres are effectively solid shiny plastic but I used to put off cuts of PVC plumbing pipe over regular wheels. I'm sure you could do the same with Lego wheels.

[Mechbuilds]

2 hours ago, Gray Gear said:

When spinning the back wheels faster than the front ones, what makes sure the rear tires lose traction, and not the front ones? Usually most of the weight is in the back, so there should be more traction there.

The RC cars probably use tires with low grip in the rear...

Well i'm probably going to tape the wheels anyway.. But i was going for 40-60 weight distribution. 40 at rear and 60 at front. I'll mount buwizz in the passenger side and the RC buggy motors will be mounted in the middle of the chassis. 
So the rear only has an empty trunk.. 

[amorti]

Buwizz weigh like 50g each, they're hardly a way to ballast either end. 

[Mechbuilds]

First test with 42111's tyres without tape. (very grippy.)
50/50 weight ratio. using two L motors with 24 tooth gears spinning one 8 tooth gear. (open diff at rear axle) 
I managed to out power the grip and actually spin a nice donut.  Buwizz ludicrous mode.

I can hear gears grinding. Possibly diff wanting to quit. Could also be the gear turning the diff. 

First test was promising. 
Next i will test having no diff at rear and gearing the front end 1.4:1 and rear end 1:1 and seeing if it will give me better results than 1.4:1 front and 1.4:1 rear.


All this possible because it's only the frame currently. 
I'll probably go for two buggy motors to get at least a little bit of torque but heaps of speed. 
Still not completely sure if i should go with L motors instead? I want slow controlled drifts instead of just high speeds. 

[MinusAndy]

Chuck some tape on the back tyres and try it, that could be the answer to what you’re looking for. The lack of grip at the back will take the load off the gears too. Definitely lock the rear diff!

[Mechbuilds]

Tested with 1.4:1 front 1:1 rear ratio. Definitely more slipping in the rear axle and drifting is easier. L motors are also pushing pretty nice power on ludicrous mode. 
I feel like it would be easier to control with taped tyres tho. I'm bashing into furniture. 

Next in line would be building the rear axle but i still don't have the buggy motors till next month.. So i guess i'll just have to wait. 

[2GodBDGlory]

Cool to see the theory behind drift cars! I may have to build another one sometime!

One thing I did once to lower traction on the tires was to cut an empty toilet paper roll into four quarters, and then put the cardboard around a 43.2 mm tire!

[Tazmancrash]

You could always go front wheel drive with trays under the rear wheels?

Would be funny as hell.

[MinusAndy]

12 hours ago, Tazmancrash said:

You could always go front wheel drive with trays under the rear wheels?

Would be funny as hell.

I believe that’s known as McDrifting.

[Mechbuilds]

I can only barely make the buggy motors fit:



2 is overkill right? Is one enough? 

[amorti]

When it comes to drifting, I don't think "too much power" is a thing.

Control it with brickcontroller2 to accurately apply less throttle if you're finding it spins too much. Can even set a max power limit if it's really too much.

On the other hand, if you build it with one motor and find that with the weight of bodywork it doesn't have enough lead in its pencil, you're stuck.

[1963maniac]

Sam Wystrach uses this differential set up in his Crawler.  https://rebrickable.com/mocs/MOC-51296/wystrach_sam/rc-crawler-4x4x4/#comments

With this you can still drive an axle with a differential while it doesn't work as a differential. It has 2 half 2L beams with a 2L axle inside it.

 

Edited October 4, 2020 by 1963maniac

[amorti]

Same in didumos's rocky.

I've just done same in koncept mantis as it spit out a 12t gear from the diff, it's a 10t gear now.

[Gray Gear]

@1963maniac Why would you use a locked up differential instead of just using a gear? What advantage does it have, surely using a normal gear is much stronger?

[Mechbuilds]

5 minutes ago, Gray Gear said:

@1963maniac Why would you use a locked up differential instead of just using a gear? What advantage does it have, surely using a normal gear is much stronger?

The point is that when your front axle has a differential, you can't emulate that same gear ratio with gears. Differential uses 1.4:1 gear ratio. If you use gears, you'll get 1:1.. Which means that your rear axle would be spinning faster than your front axle. 



I'm still waiting for the buggy motors to arrive in the mail.. While i'm waiting, i'm constantly trying to figure out if i could still add a suspension and make it much bigger.. 
But then again adding stuff will make it harder and harder to drift.. Smaller the chassis, easier it is to drift.. 

[amorti]

There's a 28t gear now, however it wouldn't be easy to fit it in a frame in the same way as a differential as it's not a thin gear.

You could argue that's how they do it on real street drifters (welded diff) so it's valid here too.

[Mechbuilds]

14 minutes ago, amorti said:

There's a 28t gear now, however it wouldn't be easy to fit it in a frame in the same way as a differential as it's not a thin gear.

You could argue that's how they do it on real street drifters (welded diff) so it's valid here too.

You can use the half 20t gear to power the 28t gear. So basically yeah if you have the new gear to use then sure it can be done with gears 100%. Probably will be a better idea since the diff is kinda flimsy. 

[amorti]

Good idea. How did I not think of that?

It would remove some play, as the locked diff part does have some slack in it.

Edited October 4, 2020 by amorti

[2GodBDGlory]

 

47 minutes ago, Mechbuilds said:

You can use the half 20t gear to power the 28t gear. So basically yeah if you have the new gear to use then sure it can be done with gears 100%. Probably will be a better idea since the diff is kinda flimsy. 

The trouble with that is that it will no longer fit inside an O-frame, so you would have to get creative with your bracing, and probably accept less strength.

[mktechniccreations]

Here is my take on mini drift car, buggy motor and no diffs, and new strong cv joints. 

[Mechbuilds]

I can see that chassis having the steering pivot point more closer to the outer edge but you will have less steering angle when using the CV joint compared to the U joint. 

A video of that chassis working would be great! Kinda wanna build that and test it. 

[mktechniccreations]

Tested, the buwizz wont handle ludicrous on RC motor, and its too gripy, will try something else