Project Streamliner: V5 Design and Testing

The RC Streamliner saga continues. V5 fixed a lot of issues of V4, but ultimately still isn't a great solution. Let me know what you think.
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#rc #3dprinting #arduino

[@briangschaefer7048]

Magnificent video! Such an interesting project.

[@IndeterminateDesign]

Thanks. I’m hopeful the next version will be more successful.

[@koopdi]

Cast polyurethane resin tires are popular in combat robots for durability and traction. Most people use the vytaflex series - overmolded onto TPU hubs.

[@IndeterminateDesign]

I want to try that out as a material and see how it holds up. I've seen some high speed wheels where the urethane is cast around a plastic skeleton that is part of the rim.

[@Liberty.Francis]

Thanks for the mention. I will say my RC cars find great traction above 100 mph when the down force is really taking effect. With foams I may only be at 50% throttle by 100 mph. It takes the right road and long distances to do the car the justice it deserves. The car side of the hobby has many challenges and a majority are based on the road. I have recently moved to rc boats for that reason. I'd love to see what you can design for outrigger rc boats.

[@IndeterminateDesign]

The boats would be fun. Are the wrecks as bad with the boats? I’m not sure my wife would let me start another hobby 😂. I really like the idea of having some sort of downforce that can get the car up to speed quickly. Maybe active aero or a fan car. Every time I run the simulations, it’s almost a mile to reach 200mph and that’s way too long.

[@Liberty.Francis]

@@IndeterminateDesign the wrecks with boats can be bad but so far mine have survived. A v bottom hull or mono hull does not go very fast. Many of the records with governed groups are in the 80-107 mph range. Hydroplanes run in the mid/low 100s and riggers have been as fast as 206 mph.

[@EngineeringAfterHours]

I think your stability has a lot to do with the drag center of pressure in this case. Dragsters like to have their rear wing behind the rear axle so that it's self straightening at high speeds. Think of it like a parachute. When you switched the traction force to the front of the car, the drag center of pressure was far behind thebdrive wheel. When it's real wheel drive, the CoP is in front of the drive wheel.

[@IndeterminateDesign]

That’s true. I had the weight pretty far back trying to get traction. I think if I wasn’t so weight conscious it would be a lot easier. I may play with FWD some more because making one of these front heavy is better for packaging too.

[@bytesandbikes]

I wonder if active aero might help? Basically suck the car onto the ground?

[@IndeterminateDesign]

I think active aero is definitely the way to go. Especially since when braking, extra downforce and drag would be hugely beneficial. I am concerned about getting enough downforce at lower speeds. The aero devices have to be fairly large to get meaningful downforce below 80mph or so. I’ve thought about a vacuum/fan for downforce. I’d love to have a car that could go 0-60mph in 2 seconds or so 😂

[@toolscientist]

This is probably a rabbit hole that you don't want to go down, but what about making your own tyres? This could give you more flexibility with wheel diameter and width. It would be very easy to do with construction adhesives like Sikaflex 11FC or Soudal T-Rex. They're on the heavier side, but you could make your rims with holes in them so that some seeps through and forms a positive lock. If they're no good, then you can try latex or EVA resins. I'd love to see a destructive max RPM test on the different compounds, and then a simple coefficient of friction test with weights and a pull scale. Could do abrasion resistance with sandpaper.

[@IndeterminateDesign]

I’m definitely looking at making my own tires, and I made a tire test rig that scares me. There are a few others working on tires as well. I have heard the silicone based tires haven’t been as strong as the natural rubber or epdm tires. But possibly with some reinforcement they could be used. The silicone is certainly a lot easier than vulcanizing your own rubber. I had no idea you could buy EVA resin. That would awesome if I could tune the properties of the foam and possibly reinforce it with some composite. I’m looking at some aramid reinforced rubber tubing or even o-rings in harder durometers. If money was no option, I found a company that makes carbon nanotube reinforced rubber wheels 😂

[@fredlarochelle]

You should definitely be using magnetic encoders. They are super cheap nowadays and gives the control loop way more information to work with.

[@IndeterminateDesign]

Definitely on my list. I had some custom PCBs with encoders made for the RCHyper car and they work great and I don’t need any filtering. I’m going to get more for these motors. The other challenge is the sensorless brushless ESC in a direct drive setup. The motors have to spin at a decent speed to generate enough back EMF. So low speed traction control isn’t great.

[@fredlarochelle]

@@IndeterminateDesign You should use a driver that supports FOC control. Something like an ODrive or you could get into the rabbit's hole that is SimpleFOC... For the magnetic encoder, if you haven't come across them yet, MagnTek, make some pretty good and affordable sensors. The MT6701 is pretty much unbeatable for the price or they have higher end parts like the MT6835.

[@IndeterminateDesign]

Ah, I’m going to check those encoders out. I’ve been using the AS5047P which is pricey. I’d love to try an O drive but they’re pretty big and pricey. I’m playing with drone ESC’s now for my RC Hypercar running the AM32 firmware that would allow me to have telemetry and they have a sine wave mode for low speed smoothness.

[@fredlarochelle]

@@IndeterminateDesign Open-loop ESCs for brushless motors at low speed aren't great. The motor doesn't generate enough EMF at low speed. That's the problem you are having.

[@hampopper3150]

Maybe you should make a car that can drive on ice instead of trying to get more grip. Like I said before you need two motors that steer and drive the car and you can use them like a gyro. I have done different setups and nothing beats 2 motors.

[@IndeterminateDesign]

I agree, the multiple motors is probably the way. I found some drone ESCs with the AM32 firmware and they’d be great for a multi-motor setup with differential torque to steer. Packaging the steering is one of the most difficult things.

[@dzidmail]

Actually, wouldn't ESC report speed that would be usable for traction control? Perhaps, at least for high speed, the stability could be achieved similar to how rockets work - "The center of mass should be towards the rocket's nose and the center of pressure should be towards the rocket's tail for the rocket to fly straight." But you probably thought about.

[@IndeterminateDesign]

The ESC I’m using doesn’t report the RPM, but yes higher end ESCs can do this. I used the front wheel speed sensor to compared against because the GPS wasn’t as responsive. Yes, I’ve tried to make the car as front heavy as possible and keep the center of pressure as far back as I can. I think that is another reason FWD might be better. More weight in the front and better stability than RWD too.

[@alexruiz1197]

10:22 chatgpt? haha