# Prestolite Timing, low frequency Curtis Start



## EVDL List (Jul 27, 2007)

Hi Jeff & all,

My MTC-4001 had a bar and is going in the factory direction. If it's 
advanced 4.5 degrees it has no other 1/4=20 holes for another brush 
position. I advanced mechanically in the opposite of direction CW rotation 
7 degrees CCW. I bought it surplus with a 70's VW adapter from a friend 
with a PMC 25.

BTW, has anyone put chokes in series with their 1231 Curtis controls? I 
found that on low frequency controls adding 150uH: twin 1kW uWave oven 
transformers with #2 6 turns (72uH each) doubles the acceleration rate at 
2kHz due to peak current pulse averaging (extending the T=L/R time 
constant).


Have a renewable energy day,
Mark in Roanoke, VA

Date: Mon, 30 Jul 2007 11:32:59 -0700 (PDT)
From: Jeff Major <[email protected]>
Subject: Re: Neutral Timing is Better for Commuters
To: [email protected]
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Mark,

MTC-4001 was designed for Jet Ind ElectraVan. It used
the Subaru tranny with reverse. So the MTC motor
would only be driven one direction. I forget which,
CW or CCW. But Prestolite used a 4 terminal frame,
S1,S2,A1,A2, and put an external jumper strap from S2
to A2. So the user would have a two terminal
unidirectional motor to work with. Because the
rotation direction was known ahead of time, the
standard MJU-2x comm end head was used which had the
holes for frame mount offset 4.5 degrees. These MJU-2
die cast comm end heads were used for unidirectional
pump motors and reversible traction motors on
Prestolite's standard line for lift trucks. One MJU-2
version with holes neutral for reversible, and
different versions with holes offset one way or the
other for unidirectional pump motors. This is
apparent when you look at the screw heads in the MJU-2
casting. There is a relief. If the screw is in the
middle of the relief, it is neutral. But there is
room such that the holes can be drilled 4.5 degrees
either way.

The 4 terminal frame was used on the MTC-4001 for
standardization of subassemblies and also to give the
user access to the field in case he wished to used
field weakening.

Like I said, I don't recall which was the standard
rotation for MTC-4001. But if you're using the
original equipment strap, you're going the correct
way. That would be A1 to S1 or A2 to S2. That strap
went parallel to the shaft axis. If you have the S to
A jumper skewed around the frame, then it is contrary.

So, it sounds to me like you went from 4.5 to 11.5
degrees advanced. Would explain larger than expected
loss of torque. I suspect the first few degrees of
advance not to diminish torque as much as further on.

Is this a Jet vehicle? Got it on the EValbum?

Hope this helps.

Jeff



> --- Mark Hanson <[email protected]> wrote:
> 
> >Hi Jeff,
> >
> ...


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## EVDL List (Jul 27, 2007)

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