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Hi, Alan
Ditto Vance's response re viscosity - but if the
motor run 'jerkily' when oil comped it's usually a sign of the brushes
'floating' - that is, the oil is thrown away from the rotor surface by
centrifugal force and 'lifts' the brushes -which causes the brushes to lose
contact momentarily - it's a function of motor speed,viscosity and spring
tension. If the motor runs at a lower rpm the spring tension is sufficient to
maintain contact - so,when at high speed - the brushes float, the
motor is 'off', the rpm slows, the brushes regain contact and the rpm goes up,
the brushes float and so on. Hence the herky-jerky.
Would seem that the simple
remedy is to increase spring tension on the brushes - but if the motor is a
variable speed ( in the case of a lineal actuator - they come both ways, fixed
speed and variable) then at lower rpm, the brushes will contact the rotor at
greater force and will wear down quickly, contaminating the comp oil and making
it conductive - which is, of course, no bueno. You can tell a contaminated motor
pretty easily, after the fact , since your nice clear baby-bum oil is now
black or dark grey!
Jes' so you know!
----- Original Message -----
Sent: Sunday, September 12, 2010 11:55
AM
Subject: Re: [PSUBS-MAILIST] linear
actuators
Thanks Vance,
the motors are only a couple of inches long &
lack any screws to take
them apart.
One of the thoughts behind testing them was that
perhaps these small
motors don't run as well in oil as larger
motors.
I'll try it with the WD40.
Alan
----- Original Message -----
Sent: Monday, September 13, 2010 12:36
AM
Subject: Re: [PSUBS-MAILIST] linear
actuators
It may be the viscosity, rather than the brushes. Brushed motors have
run well in oil for decades. Is there any way to add a little tension to the
brush spring?
Vance
-----Original
Message----- From: Alan James < alanjames@xtra.co.nz> To: personal_submersibles@psubs.orgSent:
Sun, Sep 12, 2010 6:10 am Subject: [PSUBS-MAILIST] linear
actuators
Hi all,
I just filled a linear actuator motor up with
baby oil (mineral oil)
to see how it went. It was running rough. It
would run consistently
but jerky, it ran slightly better in
reverse.
It occurred to me that most electric
linear actuator motors were probably
brushed DC & wouldn't run that well with
oil compensation.
I used the mineral oil instead of the WD40
(wich is more commonly used
in larger motors), because in experiments I
found WD40 dissolved some
plastics in time, & there were plastic components in my actuators that it might
effect.
Not sure where to go with this one.
Hydraulics?
Alan
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