Re: [EVDL] How hard is it to turn a DC motor counter/clockwise?
I have two motors on the bench that I just turn CW and CCW. One is a GE-11
and one is a WarP-9. The GE is smooth as glass in either direction and the
WarP-9 which I did not detail yet, has a slight resistance in the CCW
The GE motor has the communtator polish to a micro mirror surface which is
V-groove slightly between the communtator bars. The brushes angle greatly in
the CW direction where the face of the brushes bridges four communtator
The WarP-9 motor has a rough lathe surface with no V-grooves between the
communtator. The brushes also are angle in the CW direction, but not
greatly angle like the GE motor. The edges of the communtator bars are
rough and sharp which would dig into the sharp edge of the brushes when
going into the CCW direction.
Another thing that causes the increase resistance in the CW rotation with a
torque converter, is the torque converter blades are curve in the CW
rotation which will increases the resistance.
----- Original Message -----
From: "Cor van de Water" <firstname.lastname@example.org>
To: "Electric Vehicle Discussion List" <email@example.com>
Sent: Thursday, July 05, 2012 2:52 PM
Subject: [EVDL] How hard is it to turn a DC motor counter/clockwise?
> Little question for the DC motor experts here:
> When my EV is off, the motor is essentially unloaded
> as I removed the power steering belt and also the
> automatic transmission has no pressure so it will
> rotate freely (this is noticeable when I place the
> gear in Park and turn off the car, the motor will
> spool down from "idle" (which is about 200-300 RPM)
> until standstill in several minutes with a distinct
> screeching sound that I attribute to the brushes
> moving across the commutator.
> Now, when I grab the pulley at the tail shaft, I can
> easily rotate the motor, but I notice that the resistance
> in the normal driving direction is much larger (and is
> accompanied by the soft screeching sound from the brushes)
> while rotating the shaft counter-clockwise (seen at the
> tail shaft pulley) will run much lighter.
> Something in me says that the normal rotation direction
> should result in the smoother and easier turning, but I
> can also reason that pushing the brushes backwards will
> lift their surface from the comm and result in lower
> friction. In reverse I do not hear the soft screeching
> from brushes.
> I wanted to check with the experts here that these are
> correct observations, as I am still hunting for the
> reason of the bad efficiency of my DC conversion with
> automatic transmission.
> BTW, yesterday I drained the transmission fluid, it was
> indeed overfilled as normal it should have 3-4 quarts
> and I could not get all oil in a gallon milk jug, so
> it was probably 4.5 quarts in there. I put 3 quarts
> back in, I did not notice much improvement though.
> Cor van de Water
> Chief Scientist
> Proxim Wireless Corporation http://www.proxim.com
> Email: firstname.lastname@example.org Private: http://www.cvandewater.com
> Skype: cor_van_de_water XoIP: +31877841130
> Tel: +1 408 383 7626 Tel: +91 (040)23117400 x203
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