My mileage so far with a few days of testing the OpenRC F1 car

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My mileage so far with a few days of testing the OpenRC F1 car in ABS with an optimistic short course truck power system.

The two weak points so far are the pinion gear and the front axles. Snapped off a nose crashing into a wall but that was driver error :-). Interestingly the front wing didn’t snap or get damaged, but the nose snapped in two.

I’m getting occasional loss of steering from the servo saver rubbing against the shell despite grinding a deeper groove - the fit is tight there and I might put another washer in to increase the tension on the saver or sand a deeper groove in the front shell where the arm rubs. If that still fails then maybe I’ll tweak the saver servo arm design to be 0.25mm shorter on the servo side.

I keep destroying pinion gears whenever I crank up the throttle, the plastic isn’t enough to handle the torque of the slightly ambitious power system. I’ve gone through six of those - the gear teeth do fine but the inner hole that fits on the motor shaft gets shredded - and this is in stronger ABS, can’t imagine PLA ones fare much better. Reprinting that with more infill and more shell layers to see if that can be tough enough - if that fails the next step is to switch to a metal pinion. I had to put in a drop of CA to keep the pinion from flying off the motor at even gentle power applications.

The major structural failure I’ve had so far is that I snapped a front axle from road bumps - also reprinting that with a tougher profile. I snapped a couple of those in assembly putting the bearings on, so I was wary of this mechanical failure point from the get-go. They always snap right at the base next to the bevel. The bolt holding the axle to the axle carrier gets loose and sloppy with driving as well making the axles wobbly - I might rework that front part to print the axle and axle carrier as one hopefully stronger piece instead of two - using bridging support for the axle in printing and sanding the rough surface where the bridging support will snap off.

Another potential issue and part I have to reprint is the rear axle, the issue there is that it’s a little flexy - so any weight imbalance in the wheels tends to show up as a wheel wobble/hop at speed which makes the tires (I’m very keen to try the new friction ones that Thomas just posted - thanks!) lose traction very easily. I have to be very careful applying power with this setup. We’ll see if more solid plastic printing profiles can cure this problem.

I also want to mod the lid further to install the motor controller power switch that all the Castle speed controllers come with at the front of the lid just in front of the driver’s helmet (which I haven’t printed or installed yet. Or maybe I can come up with some clever solution to hide the switch under the helmet… The cylindrical hole version I posted actually turned out quite cool and looks and functions fine with an oval inlet shape for motor ventilation and printed well (pics soon). I’m going to adjust that hole to better match the rounded triangular profile of the intake soon if Daniel doesn’t beat me to it.

So far this is awesome though. Going today to find the parts for two more cars so I can challenge my two stepsons to races. Planning to hand them a bag of printed pieces, parts, and then offer them a bounty of $100 on Steam if they can beat me in a race.

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For me my problem was the servo and the rear axle. I couldn’t keep the wheels from flying off at full throttle and at first it was abs at 20% infill and later it was abs at 80-90% infill. It might have been because of the motor I was using. It was really powerful and with an unbalanced shaft you’re going to have vibrations and I think it was too much for my car. Perhaps with some of the stronger filaments it would’ve worked, but I didn’t have the time to do that–I was under the Xmas deadline. The servo, I needed to go with a larger rc servo. So I bought a low profile version.

This car taught me the strength of PLA. I have a delta printer with a Bowden tube so I couldn’t do the ninja flex so when I printed my wheels off I did them in regular PLA. I had to use a 12 ton shop press to push the wheels into the tires. They stood up to the pressure and only one tire broke! The rim on that tire was fine, and in 40 minutes I had it pressed into another tire. So after seeing PLA at 20% infill take 12 tons of force I have a new respect for its strength.

I know that when you sand down the front spindles it will make it weaker and it can break on that line. My suggestion is to buy the correct sized bearings so you don’t have to sand them down. That may eliminate that problem.

Can’t wait to see your car with a helmet! I’m been waiting to see who adds helmet. For me I think it completed the car.

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I might have made a mistake in the bearings. I think it was another member who posted that they received a mislabeled package of bearings that had a 1mm smaller bore, and they sanded the part down to fit. If that wasn’t you then ignore the bearing comment.

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@Dragos_Ruiu Great feedback, have you tried printing the front axles on the horizontal position? That helped me tremendously. As for the rear axle, I switched to an aluminum one that I machined. I too have found the gears to be a weak point as well. Let us know what you come up with.