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From: N_Cook on 4 Oct 2009 11:26

golf trolley, not cart



From: N_Cook on 5 Oct 2009 03:43
Some Bosch 12V,250W automotive fuel pump brushes are about right, needing
cutting down half a mm W and H to fit, side entry copper wire tails as in
this use.


--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/



From: N_Cook on 5 Oct 2009 10:20
Well that's 2 impossible jobs done reassembling the motor
1/ Tying back the brushes to get them over the armature and then removing
the cord when in place.
2/ How to replace the 5 inch long steel screws , without any built-in
guides, passing between 2 powerful magnets. They go where the magnets want
them, not some midway path. Obviously made scratch marks before
disassempling but required the head of the screw held in molegrips until you
can feel it is in the tapped hole, screwdriver placed in head still in the
molegrips, pushing down, while you release the molegrips.


--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/



From: Wild_Bill on 5 Oct 2009 13:45
The copper pigtails on brushes are a very good feature for almost any
application.
They ensure that the current has a low resistance path, instead of relying
on the brush spring and/or the metal guide (usually brass) in the brush
holder.

There is a special compound that's used to bond the pigtail to the brush,
which has been discussed in rec.crafts.metalworking before, but I don't
recall it's name.. but it's not commonly available anyway (and requires a
special process, IIRC).

Brushes with pigtails generally have a metal disk or other type of terminal
that needs to be securely constrained by the brush cap or connected in a
pressure-type terminal. Some of the disk-type terminals have small tabs to
engage slots at the sides of the brush guides, which reduce the risk of the
pigtail twisting tightly as the brush cap is installed.

I've encountered heat damaged brush springs, most often due to improper
brush installation, and have ended up replacing them with other springs for
other motors of similar size, with approximately the same sized brushes.
This has worked well enough, while realizing that the replacements may not
have been optimal as far as extended long term reliability of the motor.

I don't recall ever seeing a method to calculate a proper brush spring, a
far as contact pressure.
There's likely to be a method of selecting the best spring pressure, maybe
based upon the surface area of the brush.

--
Cheers,
WB
..............


"N_Cook" <diverse(a)tcp.co.uk> wrote in message
news:haan2o$e7c$1(a)news.eternal-september.org...
>
> It looks as though another feature of low V / high A motors is the brushes
> have copper wire tails melded into the graphite , wheras mains ones can
> often get away with end of conducting phosphor-bronze spring just resting
> against end of brush and no copper braid.
>
>

From: N_Cook on 6 Oct 2009 03:39
The 2 paralelled output TO220 thyristors had their identities ground off
before insertion. 200W, 12V motor so 17 amp so would they be say 30V 8amp,
10amp or 15 amp rating each? No fuse in the control anywhere but there is a
main relay and more electronics than just for controlling speed so could
there be an overload sensing cct that drops out the relay ? While at it
there is an off board loop of copper coloured wire, perhaps microbore copper
tube could that be a 20 or 500 amp fuse or just a dropper element for
overload sensing ?


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