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For one of my '60s F1 proxy cars I chose to use the Mabuchi FF-N20PN motor in stock form. It's pictured on my website. After a two days of sporadic testing I have found this motor to be failure prone when run at three times its rated voltage


What I've found is that the shield mounted on the commutator base seperating the comm area from the poles/windings et al will come off at high speeds. It generally takes about 7 laps of a 65' track. I found a way around that problem by disassembling the motor and removing the shield. Not a pleasant operation but possible. Unfortunately the precious metal brushes won't survive the modification. That's the second and final problem I've encountered so far with this motor, brush failure. If you're not familiar with precious metal or don't know what the FF designation means for Mabuchi motors, it's this, no carbon brushes. Just copper fingers with silver plating. On a motor this small, that's a big problem when pushing it well above its rating.

At this point in time my schedule does not permit extended research and development of a new brush assembly but I ought to be able to do something with it eventually. Some may ask why. This is a very small motor with half decent power for its size. It allowed me to build a '64 F1 Honda with a sidewinder
It took a bit of effort but for the few laps it did run it was very smooth and controllable with excellent top speed. If this motor can be made durable then we'll all be able to build skinny F1 type cars that whoop up on full size cars running without magnets. Besides, it's different.

Unfortunately for me this puts one of my '60s proxy cars on the sideline until I can work something else out for it. The other '60s F1 proxy car will be shipped as scheduled.
 

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Phil Kalbfell
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I have one of these sitting here in parts and it is the same size as the Moto GP from Scalex! Why not use the Scalex version as a replacement!

Phil
 

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Al Schwartz
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QUOTE (Phil Kalbfell @ 6 Oct 2004, 04:06)I have one of these sitting here in parts and it is the same size as the Moto GP from Scalex! Why not use the Scalex version as a replacement!

Phil
<{POST_SNAPBACK}>

Bill gave me three of the motors he is referring to last weekend. Thye are much smaller than the Moto GP motor which appears to be the same size as the TMM that I use. The Moto GP is probably a Mabuchi FK 050SH (from memory - may be off a bit) which is much narrower than an S-can but about as long.

EM
 

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QUOTE (compound_goose @ 22 Oct 2004, 08:25)generally running anything at 3 x reccomended voltage aint good! i ran a 3v motor in a slot car before, the com disssasembled itself!
<{POST_SNAPBACK}>

I'm running some Mabuchi FF-130SH motors that I got for about 50p ($1 US) each and they are rated at 1.5-3v, but they run great! I have 4 cars running on them now, 3 non mag and one with. They are the same size as the little Fly race motor in the M3 and seem to have similar power characteristics. I have several hundred laps on each and haven't had one fail yet, in fact they don't even get warm?!
By the way, this is with the stock 17v Scaley walwarts, one per lane!
 

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Discussion Starter · #6 ·
DC motors really aren't that particular about actual voltage. In this case it is primarily a poor armature design intended for something else. When I can get more time I'll make them work. It's just one of those things I do to amuse myself.

I can usually get twice as much power out of anything before I need to do any really serious modifications. Still having trouble finding a low cost mini turbo charger for the weed whacker though
 

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Why dont you try upping your gear ratios to reduce the amount of time the motors are at full tilt. That will be what is throwing the shield off the comm, Im surprised the copper fingers are surviving the current though
 

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Discussion Starter · #9 ·
The commutator is holding up fine. The problem lies in this disk that they positioned between the comm and the windings. Not sure why it's there to begin with but when it lets go it takes a few wires with it


I rarely run a motor at full speed. I always save a little extra for 'emergencies'
That's something I learned long ago in the street scene, never show them what you've got, leave them guessing.
 

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Do the wires not run over the disc before being soldered to the comm???

If they d then the idea is to stop the windings shorting on the shaft.....................I think
 

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Brian Ferguson
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aBill, can you not cover the explosion prone area with a thin layer of good epoxy? It won't help with the brush problem, but may stop the arm from grenading?


My usual method is to heat the epoxy (24 hour stuff, not the 5-minute version) until it is very runny then apply it sparingly with a toothpick or small brush, working it in as deeply as possible, and bake the arm in an electric fry-pan at about 150 degrees F (higher if the materials allow), turning frequently for the first 10-15 minutes or so. Turn the heat off after 20-30 minutes and let it cure standing vertically. Only the most radical 1/24 winds will explode after this treatment.

As I said, you'll still have the brush problem, but the arm should stay together?
Just an idea...
 

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Discussion Starter · #12 ·
I'll have to see if I can get a picture of the thing. My description isn't that good. Unfortunately the armature is kind of dinky and my camera doesn't do well with small subjects. See how I casually blamed the camera for my lack of photographic ability?
 

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Discussion Starter · #13 ·
This is a poor picture, as promised
but you can make out that there is a circular thingamajig between the comm and the windings. This thingamajig comes off with predictable results at high speed. The other armature is a stock size arm for comparison. Plus it gave me something to focus on, that little arm kept disappearing


 

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Discussion Starter · #14 ·
Fergy, I'm trying the epoxy on the windings side of the comm disk thing. Can't hurt and it'll probably work. Sure beats what I was going to try to do
 

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Brian Ferguson
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aBill, any idea what that thing is for?
Looks like an automotive flywheel!
Part of an external rotation speed sensor???? Part of EM's anti-gravity system????
 

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Hi Fergy

The disk makes it easier during the winding process for the machines.. Cuts down on the failure rate and makes it easier for the inspectors to spot a flaw.

Fate
 

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Brian Ferguson
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Hmmm... okay Fate, that makes sense I guess.
I realize these motors were never intended for slot use (or should I say 'abuse') but it does seem ironic that they grenade in our hands just so a machine has an easier life!
 

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Discussion Starter · #18 ·
I think the epoxy will work but I'm still having trouble with the end bell. Those precious metal brushes are awful to re assemble.
 

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Discussion Starter · #20 ·
Well, the epoxy held but the brushes are toast. This makes seven dead motors with no real gains in longevity. I'm rather disappointed in myself. This motor was originally intended to be used in Professor Fates '60s F1 race. I wanted a sidewinder in a skinny tired F1 car
So at this time I'll have to set this failure aside and concentrate on dumb things, like the holidays. Perhaps in late January or early February I'll be able to get my act together and make this thing work.
 
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