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MrCrankyface

3D Printed RC Buggy: Version 2 (RWD)

by MrCrankyface Dec 29, 2018
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Добрый день! Помогите!
При обработке в слайсере Simplify3D файл BuggyV2_Tyres_Rear.stl у меня нет наружного контура и получается шипы висят на воздухе, что мне делать?

After some more runs my dogbones seem to be digging into the nylon hubs causing a lot of friction (Taulman 645).
What Nylon are you using? Will try Taulman Alloy 910 or PA-CX12 next.

Auch! Looks like the gear has been heating against the sides of the case.
It's important to put a long screw through both dogbone hubs and then check so the gear can't hit the sides of the case.
If they've shrunk or gotten loose it's possible that they have too big of a side clearance and allows the gear to rub and heat everything up.
I also added a bit of grease to all my gears, I find that it usually helps reduce friction.

I think I used taulman bridge but it also deforms/digs in after a while. I reprogrammed my ESC to apply the power a bit softer, it's hardly noticeable but damages the dogbone hubs a lot less.

another amazing work!!
is this 1/10 scale buggy?
i am going to buy wheels and tires, which scale size would fit this?

It's roughly 1:10.
Tires with a diameter of 80-100mm works great.

Just got my dog bones and had a small run in the garden. Wow this car feels much more durable than the previous version, handling is great and no issues with a brushless setup. Many improvements over v1 there.

Some remarks:

  • I need a slightly shorter pinion as it runs into the cover.
  • The speed it is rather moderate. I'm using a 2s battery with 3300kv motor. Do you have an idea what speeds you get on 2/3s? Is there a bigger gear reduction compared to v1?
  • The car is a little bouncy, mainly in the back but might have to tweak my suspension a bit

Is the pinion gear itself hitting the cover or is it the motor shaft? It's quite tight but should be ~1mm before it hits the cover, it's supposed to seat quite far in.

Calculated speed with current ratio on my 3S/3000kv motor is around 51 kph.
@ 2S/3300KV it should be 38kph.
I think the gear ratio is 11.47 to 1, assuming my calculation is correct, it's an old spreadsheet that I hardly remember making. :)
This is with 86mm diameter tires.

My source files for V1 are a bit incomplete but I think it had a ratio of 8.17 so it would be considerably faster with same battery/motor.

I ended up running quite a soft rear, seemed to reduce the bounciness but unfortunately also makes it "dive" more in the rear when accelerating.
I think it would've benefited from the COG being further backwards as I think we've previously talked about.

I ended up taking a look at different ratios .. Apparently the motor adjustment geometry was off so I fixed this with a new BuggyV2_rearSusp_HubA part.
Also uploaded BuggyV2_RearSusp_Gears_MotorGear_lowratio and BuggyV2_RearSusp_Gears_SecondGearC_lowratio for higher speeds. Should give you a theoretical top speed of 55kph.

I will first try a 3s battery and see how that handles. Do these new gears also fit in the motor cover? 50kph is more than enough for a printed car :-)
What was off on the motor adjustment geometry?
Attached a picture of the pinion, don't think I can slide it any further on the motor

The pinion should sit flush with the larger gear, maybe the frontend of your motor looks different so it can't fit as deep?
The new gears have the same width so should fit the same.

Running different pinions would require you to rotate the motor a bit to adjust the gear engagement. The slot it slides didn't have the correct pivot point which greatly reduced the amount of movement you could have without the pinion gear hitting the hub part.

I'm uploading a new gear cover which should make it a lot more forgiving for variances. :)

That gear cover will fix the issue for me :-) Big thanks

Just had a run on 3s and except for some tooth skips sometimes on full throttle everything runs great. Most of my gears are nylon and because of shrinkage they might have ended up a bit smaller. Also today it was freezing so quite slippery, with dry grass and more traction this skipping might get worse. I'll keep track and report back if there are any structural issues.

Hi MrCrankyface,
love your projects.
Have this Buggy printed the last week with the following result.
My only problem was the gears and wheelshaft. I have some PU filament but I did not manage to print with it. (Anet A8 with blue masking tape, bed 75 ° C, extruder 235 ° C) Always comes loose from the bed. So there with PLA. Maybe that's why it makes a hell of a noise when I run the engine. Still without the dogbones I'm still waiting for from China.
Go smear the BuggyV2_RearSusp_Gears_DiffB, DiffC and BuggyV2_RearSusp_WheelshaftA, WheelshaftB with XTC-3D that I have as a reinforcement resin.
So I'm going to take it easy with this Buggy.
Have also let my imagination run about the body.
Maybe you recognize the front wheels. Made one mistake, ra ra ra which?
regards
Christiaan

Добрый день! Красивая багги получилась. А где вы взяли двигатель и трубы, очень здорово смотрится, тоже хочу так сделать.

Thanks! That's an amazing build, I love it! Nice rear wing! ;)

Thank you, and correct answer.

That looks great! Also waiting for those dogbones here, will post a make when they arrive.

Could it be that the 4 bottom front suspension M4 screw holes have a too big diameter? I had the same problem with v1. The M4 screw holes on the other parts are much tighter.

They were actually a bit slack at 3.9.
I've adjusted them to 3.85 which is what I normally use nowadays and uploaded new stl.
Good find!

Looks like something is wrong with the wheel spacers, the axle holes are too deep and the flat side only starts after ~5mm. This causes them to push against the bearings which in turn causes friction during rotation.

They could definitely benefit from some adjustments though. I will see if I can get it done tomorrow!

They could definitely benefit from some adjustments though. I will see if I can get it done tomorrow!

They're supposed to push against the inner race of the bearing, this should not create any friction as the inner race spins with it.
It's possible to squeeze teh bearings together if the spacer between the bearings is too short, this makes them rotate poorly.

What is the reasoning behind this? Typical RC cars have a pin in the axle to grab and avoid this kind of pressure. I would expect the pressure to be at the end of the axle against the spacer (where you now have a cavity). That way the rest of the system is not under any stress?

Also when using the provided wheels this pressure is not applied as the flat part of the axle fits the hole?

Last time I played with a 'real' Rc car was probably around 20 years ago so I just made something up that seemed to work. My wheels are very free spinning. The B part of the wheelshaft should take up any compressive load.
I wasn't even aware of the cavity until I took that picture, somewhere/sometime I must've missed a measurement.
I've uploaded new wheel adapters that should also relieve this pressure by now allowing it to get too squeezed together. :)

For the previous version of the buggy, you released a design of 3d printed rod ends for the steering links. These printed very well on my printer. Do they fit this design as well?

https://www.thingiverse.com/thing:2404788

Rod end prototype for R/C vehicles and servos

It might work if you use spacers and modify the mesh so it's the correct length.

It might work if you use spacers and modify the mesh so it's the correct length.

What battery/ies are you using?

I'm using a Vapex VPFlight 3S 4000mAh 25C

Any alternatives you know of for that HSP 02003 dogbone? I'm looking for a local reseller (EU) but it's hard to find.

Here's the 02003 from a UK seller:
https://goo.gl/Pk93LH

As long as it's 61mm total length I think it should work.

Looks like RER02003 (Redcat) is an alternative but more expensive.

What is that white stuff you used on the body?

I used a 3D pen to fuse it together at points, not necessary but I imagine it makes it a tiny bit stronger at the seam.

Where did you get those open 3d printed tires in the picture? Were they any good?

They're from this set:
https://www.thingiverse.com/thing:1408635

As fronts they're nice.
As rears they are a little skinny, will depend on terrain.

Printed truck: Tyres

What size is the pinion gear? I would like to use a steel one if possible. Awesome design!

it's a 1M(module in mm), 12 tooth, 20* pressure angle.

That is some elaborate rear suspension, wonder how it's like.
suspension travel is one thing but you want droop too.

It looks fancier than it is. :)
The function is the same as if the shock was at the same position as the front shocks, just flipped around.
Droop will depend on how hard you preload the shocks, zero preload will give you more droop.

W00t, happy new year to you!

GREAT!! Already getting parts list, to see what I need to order. Great 2019 project. Excited!!