Subject:
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Re: questions about swapping rubber bands
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Newsgroups:
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lugnet.trains
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Date:
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Mon, 7 Apr 2003 17:52:27 GMT
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Viewed:
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1565 times
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In lugnet.trains, Cary Clark writes:
> In lugnet.trains, Reinhard "Ben" Beneke writes:
> ...
> > <SNIP>
>
> Odd thing was, after looping for a while, the motor stopped working at any
> speed. The light on the train still responded to the regulator, so the
> problem is definitely in the motor, not the regulator.
>
> <SNIP>
> One more thing: when swapping rubber bands around, I noticed that the fried
> motor was missing one rubber band altogether. Has anyone seen motor damage
> resulting from missing bands?
>
> Cary
Hi Cary,
I remember that i got also once a problem with a 9V motor (from a new
Metroliner set). I could replace him for a new one after contacting LEGO
abouth it. The train could run for abouth 10 rounds and then stopped, but
the light in the train kept on shining. Now, past year opened i 6 9V
motorblocks to convert them for DCC operation. Then i noticed a small disc
between the motor and the wheel assembly. This look to me as a PTC or a
Polyfuse. This means that it acts as a kind of interuptor to prevent the
motor to burn through at overload or stalling.
If it's a PTC then : When the current through the motor exeeds a certain
limit (at overload) the PTC heats up and increases his resistance,with limit
the current through the serie connection of the motor and PTC. The PTC's
resistance goes back to its previous value after cooling down of the PTC.
If it's a Polyfuse then : When the current through the motor exeeds a
certain limit (at overload) the Polyfuse increases also his resistance but
this goes from a verry low resistance (mili Ohm )to a verry high resistance
(Mega Ohms)in a short time, so acting as a regular fuse witch is blow up.
BUT, a polyfuse restore automatic to his previous state after the current is
cut so that the Polyfuse can cool down.
Personally i think it's a Polyfuse because i can't measure an initial
resistance when it's at room temperture. A PTC has ALWAYS a basic resistance
of a few Ohms / tens of Ohms (4.7 or 6.8 ,47,68 ... Ohms). Asume it's a PTC
then you have ALWAYS power loss on the motor because you have two resistors
in series. If it's a Polyfuse (initial resistance = some mili Ohms) then is
the powerloss over the Polyfuse neglectable comparing with the powerloss
over a PTC.
I hope your problem motor runs again after cooling down.
Regards,
Ludo
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Message is in Reply To:
 | | questions about swapping rubber bands
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| In lugnet.trains, Reinhard "Ben" Beneke writes: ... (...) Last night I finally got around to filing down a few of my many defective wheel sets and successfully got a single Santa Fe engine (for the first time) to pull five stock Santa Fe cars around (...) (21 years ago, 2-Apr-03, to lugnet.trains)
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