----- Original Message -----
Sent: Sunday, September 12, 2010 2:10
PM
Subject: Re: [PSUBS-MAILIST] linear
actuators
Thanks Phil,
I just broke some plastic in the motor trying
to put more tension on the springs.
I've got 6 actuators lying about, & they
all need to go at full speed to get a reasonable
piston extension speed.
I've been persisting with the idea of
compensating linear actuators as has Frank, but are
now wondering about the merits of it. I'm
thinking my options are to buy something like
a Lenco trim tab actuator & change the
gearing to speed it up & replace the motor with
a brushless one. Or make one up from
scratch.
Do you have any thoughts on hydraulics V
electric pistons? I'm mainly using them for
rotating my motors, wich will be counter
balanced, so not too much force is required.
Also have thoughts of using them on a light
weight manipulator.
Regards Alan
----- Original Message -----
Sent: Monday, September 13, 2010 8:25
AM
Subject: Re: [PSUBS-MAILIST] linear
actuators
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
