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KrisCubed

3D Printed RC Car v3 -- Tarmo3 -- Rear Parts [2/3]

by KrisCubed Apr 6, 2019
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Can I use a different ESC? if so, any recommendation? because it's hard to get the exact same motor and ESC in Canada. Also, how did you orient the steering linkage for printing? Thanks.

You can use any ESC you want. The motor is more important though, it needs to be the same formfactor. The linkage should be printed with the holes perpendicular to the build plate.

Thanks. For the same ESC, which type of plug should I choose for my battery?

Just get one that matches the one your battery has--Or buy an adapter.

Ok, printed the top of the rear differential case twice and both times the holes for the shock mount are too large - the screws have nothing to grip on. The screws for the arms are fine. Any thoughts?

Interesting! Would you mind telling me what printing settings you are using?

Hi Kris
Love your work.
Having a real close look at all the parts and assembling them in blender before I start the print.
I have noticed that there is a difference in the primary steering link .stl and the detail pictures.
Looks like the .stl is not really useable as uploaded and different from the link photographed.
Am I missing something or is the uploaded file an older version?

Keep up the great work, my son and I are really looking forward to building this.

Hey Kris. I love the design of the car, but i have a problem while building, and maybe can you help me.

Here is the video of problem:
https://youtu.be/jFc8cu4Vqj8

As you can see, one axle have problem turning. I put a lot of lubricant inside both axel and one is ok, but the second have problems turning.
Any idea

That looks to be normal. That's just how a differential works. Is the other side spinning non-stop? Once it has a load from the tires it will spin both.

Great job on your modeling, this is pretty awesome. My son and I have been putting this together and noticed that only one side of the rear chassis has an inset for the nut

Yes, that's because on an older version of the chassis, front and rear were the same part and you just needed to print it twice, having one insert on only one side made it such that when you mirrored the part, each rod had one inserted nut and one nut to tighten. But I have ditched that design and now the front and rear chassis are different--So each can be designed differently--I never updated the rear chassis because that design didn't work well anyway, the nut would always vibrate loose, so thats why I put locking nuts on the BOM to replace that idea, the insert is no longer needed you can cover it with a washer or use it--Just make sure to use locking nuts like the BOM says.

Is everything with the car going well?

Going well so far. Still waiting for the shocks, motor, and torsion spring to to be delivered. There will likely be a few places that I still need to go back and replace regular M3 nuts with locking versions now that I'm closer to a recognizable car but for the most part it wasn't hard to put together. =-)

Did you ever design rod ends for the connection between the servo and steering mechanism? I saw your other "Fully 3D printed RC Rod-Ends / linkages (Various Lengths)" but I didn't see any that would handle the twist between from the servo to the linkage. I ordered Rod End already, but I was just curious.

I can't wait to get it fully assembled and test it out next week.

Did you ever finish the car?--I'm interested to see it! Post a make!!

Has everything worked well?

I hadn't thought to design a linkage there, but I should have--Perhaps I will.

I did finish it! I had a couple challenges, but all in all it worked out really well. I've attached a couple pictures. I think the brown filament I used wasn't as strong as the black and I had a couple early breaks. I also have it in rear wheel only mode right now as I managed to mangle the spring when I had it in 4 wheel drive mode, but likely I just need to adjust the sensitivity settings between the speed controller and remote.

Thank you for sharing!! Its so cool to see people making the car!~I appreciate you taking the time to try my design.
I also found that some filament is stronger than others. Currently the best stuff I've found is a marble PLA from amazon. its super hard and prints well. I normally drop the punch setting on the ESC down to keep that sort of thing from happening with the spring, though in the past I have distorted a spring, I've never broken or damaged one to the point that it was no longer usable. Very interesting.

Have you thought about a 4 wheel steering version? With a second servo and today's fancy controllers it should be possible to setup a speed and steering angle dependent degree of how much rear steer gets applied. At low speeds and high front steering angle you'd want a lot of opposite direction rear steer for maneuverability. At high speeds you'd want less rear steer, even a slight steer in the same direction as the front.

In the 90's two companies produced a car model with 4 wheel steering. One went all high tech with electronic control of the rear steering.

The other used a 100% mechanical system with a gearbox and shaft from the front to the rear. As the driver turned the steering wheel, the rear would begin steering the same direction as the front. As steering angle increased, the rear wheels would go back to straight, then eventually steer opposite to a greater angle. Their rationale for doing it that was was at higher speeds the steering angles tend to be small for lane changes while at low speeds steering angles are usually larger, which would benefit most by larger opposite rear steering for parking a U-turns.

Yes, I know all about those cars, and its true that I had the same idea, putting a second servo for rear steering. It's definitely not off the table as a cool idea. I don't see it really helping the performance of the car, but I love mechanical complexity, so I bet this would be really cool!

We shall see.