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Discussion Starter · #1 ·
I was fortunate to get a Tyco S chassis for a Lotus Indy project but found one of the motor magnets to have a chunk missing. The car runs, albeit pretty weak. These are flat magnets (not contoured to the armature like most other can motors) so I'm curious if anyone has found a decent alternative or replacement? As always, thanks for sharing your knowledge!
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I have noticed that magnet strength needs to be balanced with the rotor windings. I remember putting a super strong magnets in a vintage car and I believe it ran slower*. (Can someone confirm this to be true?) *I didn't record timings however.

We have electronic surplus stores and Hobby Lobby sells a lot of magnet sizes. Since the vintage magnets are not rare earth, a black magnet will do.
 

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Rich Dumas
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People that tune pancake type cars have known for years that the armature and magnets need to be matched for the best performance. The reason for that is that a DC motor that is turning is a generator and will produce a voltage that is the opposite polarity from the applied voltage. The term for that is back EMF and that will cancel some of the track voltage. The amount of back EMF will be proportional to the motor RPMs, the magnet strength and other factors. The main effect is that magnets that are too strong will reduce the top speed of a car.
I looked to see if replacement motors are available, Slot Car Central is often a good place to look for more obscure things. I did find some similar Tyco motors, but the magnets were larger.
Just for kicks you might try stacking a neo dot magnet on the side of the motor with the damaged magnet, otherwise you would have to find regular ceramic magnets that are the right size. If the replacement magnets were a little small you would need to glue them in place. If the magnets were too big grinding them down would probably demagnetize them to some extent.
 

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Knee jerk:

Short of direct replacements for the old bar magnets, later Tycopro magnets MAY be a possibility. Although their faces are contoured, the backside is flat. (for sanding, should the fitment be a hair off).

I'll have to rummage around in my box of vintage box motors tonight and see. Several manufacturers of the era used this design.

Edit: Temporarily? Flexible refrigerator magnets, perhaps. The trade marked product was called "fasson" in my day. Easily sliced, diced, and glued. As those armatures are whimpy anyway, it may be about the right balance.
 

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Follow up and reality check. Doh!

It 'd been a while since I'd had one of these old timers apart. The retainer clamps arent re-useable. I broke four of four for a perfect score. I've got a trick for securing the commbox to the motor frame after you kill one taking it apart.

Due to the design of the one piece plastic combox and magnet retainer/pockets, only flat bar magnets will work.
 

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Rich Dumas
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McMaster-Carr sells flexible magnet sheets that can easily cut to size, they are available in various thicknesses. I suspect that the material will not be strong enough, but you could give it a try.
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Discussion Starter · #8 ·
Thanks for all the ideas; worked on it more this morning....
Cutting a magnet to size, nope, magnets are brittle. ;-)
Stacked thin refrigerator magnets, way too weak. Orig measured ~1K on my magnetometer.
This one will have to accept his role as "last place" for now, didn't have much of a chance anyway.
Solution is going to be buy another parts chassis and hopefully match up magnet strength a bit better.
Pretty easy to make your own magnetometer for matching magnet strength which helps performance.
I loosely followed these instructions: Make a Magnetometer

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