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Discussion Starter · #1 ·
Hi, have a Slot.it Orange bell. Thing is it was smoking on last run. Ohms across it 1 Ohm.
Just tested two other motors and they read 25 & 34. So I'm guessing that the OB has a dead short somewhere.
Shame really. Nearly new. Cannot be more than six months old. Slot.it F40 kit.
Can someone confirm please?
 

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If its smoking you can be pretty certain there is something wrong with it.
A common cause of smoke is the windings shorting out due to the insulation having failed. If the windings are black or discoloured (often just on one pole) that's a sure sign of that sort of problem. That means you need a new arm (unless you are into home rewinds).
A stray strand of wire across the commutator is another possibility, that might be repairable (unless the high current has damaged something else)

The motor resistance measured through the brush gear with a multimeter is somewhat unreliable. 1 ohm is too low for that sort of motor, although for faster motors it can be that or less. 25 or 34 ohms sounds a bit too high, but that's probably due to the measurement issues.
 

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QUOTE (choc-ice @ 3 Jun 2011, 16:08) <{POST_SNAPBACK}>25 ohms sounds in the right area, that's 0.5 amps at 12V

1 ohm sounds like a dead short, perhaps a stray strand of wire across the commutator

That what i calculated, so confirmed. I'll open her up and take a look.
Cheers

That's it then, COOKED. DEAD, BLOWN, Not impressed with slot.it motors. Only one other motor has done this to me. A Typhoon 18K bit the dust the other week. Trouble was, that one went up in flames over the pond. Under scrutineers for the RAA Proxy.
I run at 16v, Hornby warts. the last outing she made was on a track pushing 13V. It's the AMPS that kill things, so what AMPS, do they run over the pond, and Tony, what AMPS are you pushing?
 

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QUOTE (Saviour @ 3 Jun 2011, 15:51) <{POST_SNAPBACK}>It's the AMPS that kill things, so what AMPS, do they run over the pond, and Tony, what AMPS are you pushing?

Surely the motor only draws the current it needs? The power supply will be able to make enough current, but it's down to the motor to what current will be drawn.
 

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QUOTE (choc-ice @ 3 Jun 2011, 17:36) <{POST_SNAPBACK}>Surely the motor only draws the current it needs? The power supply will be able to make enough current, but it's down to the motor to what current will be drawn.

That's what I would expect. But some PSU give higher Amps at a certain Volt level. Which makes me wonder how little Amps some motors can take before something gives?

Falcon motors. Amps at 12V - Not good for home sets.
Stg12 motors. Amps at 12V - Not good for home sets.
Mabchie motors. Amps at 12v

300SLR...Black as coal inside. No sign of a broken or damaged wire. I think I'll rewire it, have not done that in 40 odd years, so. Hay, why not.
 

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QUOTE (Saviour @ 3 Jun 2011, 17:45) <{POST_SNAPBACK}>That's what I would expect. But some PSU give higher Amps at a certain Volt level. Which makes me wonder how little Amps some motors can take before something gives?
Mabchie motors. Amps at 12v
Standard Scalex motor takes about 2 amps on stall, much less at speed.
If the power supply won't supply that much, then on start up the volts drop till the motor speeds up and requires much less current.

Doesn't matter if the supply is capable of supplying the motor with 2 amps or 50 amps, it'll only take 2 amps.

If however the motor develops a fault so that it takes more current, then the higher current supply can put more amps through it. So a motor that has already failed may produce rather smoke with a higher current supply. The same failure on a lower current supply it would produce less smoke, but hey its only fit for the bin anyway so who cars about a little more or less smoke!
 

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Before you chuck it open the motor up and clean between the comutator segments using a thin blade/shim.
This has happened to me a few times with these motors, seems its quite a common fault due to a combination of oil and soft brush material.
If you haven't run it too long in this condition you should be ok but if run for long periods it could burn the com insulation through to the armature shaft.
Good luck.
[oneofwos]
 

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Try the Scientific Wire Company, they have a site so do a google search.
With a vernier measure the diameter of the wire, should be about 0.15mm [about 38 swg] or possibly less.
Don't forget to count how many turns of wire went on when or if you pull the arm apart.
Have fun!

[oneofwos]
 

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Saviour,
I had a similar problem with my Slot.it F40.
Most likely it is not a fault of the motor itself but it might be caused by the limited space of the interior that is slightly pressing the ferrite man legs to the motor bell.
I just added same insulating tape I had no further failures.
In my case, after binning the motor in a separate box, I tried it after some time once again and with some flashing and sparking I run it at full speed for few seconds and it came back alive once again.

I'm not sure it is the same with your motor and I don't guarantee you will not damage it permanently.
So, unless you don't give a shed of the motor, that's the hard way of revival


Cheers,
JamieG
 

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Discussion Starter · #12 ·
Scientific Wire Company, Here I come...As I said, I have not rewound a motor since I was about 13, 14. But I can still ride a 2 wheel Bike.
Funny thing is. Fire the motor up on the bench, no pinion. And away she goes. But you can tell she is not giving her all. Put the pinion on, and place on track, SMOKE.
Cheers Guys.
 
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