Buzzy Wheels
Having a few problems and hope I can get a few solutions from this fountain of knowledge.
I test some donar cars, find the fastest, wheels seem perfect, no noise or wobble when spinning. Split the car and remove the axles, note the orientation so I can place them in the modified car the same way they came out of the donation car. Inspect the wheels, no burrs or abnormalities visible. Go ahead with the modifications. Lock the axlesdown. Sand the wheels and apply graphite. Spin them and they seem really good. Running true, still not wiggling or bumping on the axle. But then if I spin them as fast as I can I get a buzz. Few questions.
1. Is this normal for all wheels no matter how good they are if you spin them as fast you can?
2. Is it only an issue when the wheels are free floating in the air with no weight on them?
3. Am I expecting too much from the wheels, can you make any wheel buzz if you spin it fast enough?
Kinda annoying as the cars in question are still fast, well, fast by my standards anyway.
Discussion
There's an empty gap between the axles and the inner bearing surface of the wheels. Spin them fast enough and the heaviest side of the wheel will pull away more from the axle than the lighter side, closing the gap on the heavy side. What you have then is an imbalanced object spinning at high RPM that has no choice but vibrate the assembly as the wheel is fighting to get away from the axle.
At the lower RPM the wheel isn't trapped against the axle yet, so as it rotates the axle easily slides against the wheel's plastic. At the Higher RPM the two materials are friction locked against each other, like a person swinging a hula hoop around their waist.
A fluid with high enough viscosity between the two materials will nicely dampen the effect! In the case of this hobby, lower viscosity. Oil is the way, get The Juice...
- thank you for that. any recommendations for which oil to go with? — Chipped_Paint_Racing
- Yeah, look into, “The Juice.” Redpill Racing sells it. — X2Whiskey
- thank you — Chipped_Paint_Racing
"At the Higher RPM the two materials are friction locked against each other, like a person swinging a hula hoop around their waist."
I'm stealing that analogy! Imho, it perfectly describes the effect. At certain speeds instead of sliding on the axle, it will shoop shoop hula hoop and buzz. Drop a touch of oil and spin again and it will slide on the axle again... until it won't and then starts hula hooping. I have wondered if it is a weight issue or a fitment or out of round issue... or a combination of many. I don't believe the holes in the wheels are drilled. I believe they are created during the injection moulding process. So miss drilling them isn't the culprit. I am still investigating...
- I'm inclined to think that the axle holes are molded in. Maybe after they are chased through to final dimension? I kind of doubt the extra step with the goal of mass production at minimal costs. Perhaps the mold haves aren't always properly aligned. Often times you can find the main half and back half off-center with each other. I notice this often when sanding wheels. — X2Whiskey
I think 'wheel buzz' is an inherent problem with the bearingless wheel & axle. It appears to be a balance issue, although I'm sure any tiny imperfections in the moulding process could contribute as well. In any case, it has a limiting factor on wheel RPMs which directly affects performance. Smaller wheels tend to buzz more that larger wheels. I've noticed that some wheels will buzz when I spin them by hand but seem to stop when the wheels roll on the track, under load. Not sure what causes that. I just keep them lubed and hope for the best.
FWIW, I think MBX starburst wheels have a consistently higher RPM tolerance than most wheels.