My Car Is Eating My Tire

[MikeyAutobahn]

I was racing the other night, and after my usual post-race inspection, I noticed that the motor shaft was eating into my tire:



Aside from cutting it off with a dremel [which I don't currently own], is there anything else I can do about it for the time being?

Thanks.

[Audi1]

It looks like that's a podded car, Mikey; likely a Slot.It SW pod(?)

That's a strange routing of the tire; it looks uneven, like the tire is only hitting the armature end on certain spots. If that's the case, then you have: 1. rear tires that are too large I diameter for the car with the armature extension still in place, or, worse 2. tires that are way out of round (not trued), or both. Rotate the rear wheels/tires while looking at the armature extension; that will tell you where you problem lies.

I'd purchase or borrow a Dremel tool with a cut-off disc. Not a lot of expense and you'll use it over and over again if you stay in slot car building/racing.

Allan

[Rleog]

Tire contact with the armature may not be apparent when rotating the wheel by hand. The tire may be enlarging its diameter due to centrifugal force as it reaches a high RPM when driven by the motor.

You'll need to look for contact while the tire is spinning rapidly.

[mikeinclover]

If the tire is not glued to the rim it maybe expanding and hitting the armature when under full throttle.
Mike

[hksk25]

Looks like your tires are expanding at speed. If you choose not to glue, about 1/2 down this rebuild post, an explanation of trimming the motor shaft. PitRow/TunaClassicLola/flyclassictuning.htm

Harry

[MikeyAutobahn]

Glue.

I don't know how that one got past me. I didn't even think about it being the issue. The tires are stock C1's that came with the car. I never glued them. What's good? Crazy glue? Something less harsh? I'm of the belief that it's likely what Bob Goulet mentioned about the high RPM's causing it. The other day I was innocently enough running on the CRV mode on my controller, and punching it pretty hard in the straights. I'll bet I did it then.

I checked the tires, Chris, and found that, at least by the eye, they look pretty even. There's no discernible difference in the height as the tire goes around. I know that the naked eye is about as useful as a screen door on a submarine, but it's all I got. Totally going to get a dremel, which now goes on my ever-expanding list of stuff to pick up. That cut, however, lines right up with the motor shaft.

Thanks guys.

[Modlerbob]

One way to handle that problem is to use an emery board (sanding stick) while the motor is running at about 6 volts.

[chrisguyw]

Hello Mike, As others have suggested, the most likely cause of your problem is that the tire is expanding and touching the armature shaft at high speed/rapid acceleration. Gluing the tire to the wheel will alleviate this. CA will work just fine, but look for a rubberized CA (it looks black/gray in the bottle) as the rubberized stuff has better shear strength and is less brittle than the normal (clear) CA variants.

Cutting the armature shaft is a very good idea, particularly on cars where you may want to use a larger diameter tire, and a dremel with a good quality cut off wheel is the only way to go!!!........A tip!....apply some power to the motor when cutting the motor shaft....you will get a much cleaner/truer cut, and you will put less lateral pressure on the motor shaft/bushing.

There are other quick fixes........1/ bevel the inside edge of the tire so that it clears the motor shaft, 2/ space the rear tire outwards a touch.........again, these are quick fixes, and while they will work, neither will eliminate the "expanding tire" issue.

Looking at your pic. it would appear that you have not glued/screwed your motor into the pod cradle........it is quite common for there to be some movement between the motor and the pod cradle, both fore and aft, and, from side to side, neither of which are good things.......a motor that can move in relationship to the rear axle will result in poor gear mesh and have accelerated gear wear, and, heaven forbid if it pops out in a crash when you are leading a race. Additionally, securing the motor will add some much needed stiffness to the rear of the pod, both torsionally and longitudinally. Slot-it (and others) sell 2.0 mm machine screws for securing the can end of the motor to the pod motor lugs, and you can also use Shoe Goo or tape. In plastic car pods, I generally use machine screws on the can end, and a thin bead of shoe goo around the perimeter of the pod motor interface. The Shoe Goo is easily cut with an exacto for motor removal.

Cheers
Chris Walker

[MikeyAutobahn]

Thanks Modlerbob. I have an emery board that I use, as well as two different grades of sandpaper. They work okay so far, I guess, but I really want a tire truer.

Chris, again you are a huge help with advice. You're absolutely right; I never glued/screwed my motor pod in. I didn't even think it could be a thing that I needed to worry about at this point, but apparently I do. I'll add those to my list. Thanks. Wouldn't beveling the inside of my tire give me less of a contact patch? Or am I kind of s.o.l. regarding contact now because of that cut in the tire? I'm going to get new tires as well when I make the big parts purchase, but I'd like to run these ones for awhile before doing so. I haven't noticed any strangeness out of the car with the cut tire yet. I ran about 300 or so laps today on it, and it's not nearly as noticeable as before. Seems to be getting sanded out by the track.

Gluing happening now. Will report.

[Audi1]

Here's a video that Mike did a few years ago; very helpful for gluing (and then truing) tires.



Allan

[MikeyAutobahn]

:music-rockout:

Thanks!

[MikeyAutobahn]

The gluing worked great. Cars run much better.

Those Cloverleaf videos are really helpful.