DIY Electric Car Forums banner

Prestolite Timing, low frequency Curtis Start

1746 1
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

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]
MIME-Version: 1.0
Content-Type: text/plain; charset=iso-8859-1
Content-Transfer-Encoding: 8bit
Message-ID: <[email protected]>


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.


--- Mark Hanson <[email protected]> wrote:

>Hi Jeff,
>I didn't realize the MTC-4001 was advanced 4.5
>degrees, which way? There were only single holes not 2 options for neutral
>advanced so I don't see how they would manufacture a motor not knowing the
>direction of the application. I advanced the motor 7 degrees turning
>the brush end CCW into the CW motor direction with the vehicle forward
>motion and tapped 4 new 1/4-20 holes for that setting.
>(Advance DC engineer said their motors are *not*
>advanced since they don't know the user direction or application).
>best Regards,
>Date: Mon, 30 Jul 2007 07:46:29 -0700 (PDT)
>From: Jeff Major <[email protected]>
>Subject: Re: Neutral Timing is Better for Commuters
>To: [email protected]
>MIME-Version: 1.0
>Content-Type: text/plain; charset=iso-8859-1
>Content-Transfer-Encoding: 8bit
><[email protected]>
>Hi Mark,
>It's great to see you doing some real tests and
>sharing. 25 to 33 seconds is more than I expected.
>Remember a few weeks ago. I said:
>"Chances are you have a 4 pole motor. And your 7
>degree figure is actual or mechanical degrees. So
>really have it advanced 14 electrical degrees. If
>advanced it 45 mech degrees (90 elect degrees) you
>would have zero torque. I am not sure it is a
>relationship, but it might give you a feeling. 7
>divided by 45 equals 0.155. So your 7 degree shift
>might result in 16 percent less torque at current
>Acceleration is proportional to torque. So does 7
>degrees equal 16% less torque equal 16% slower
>Give it try and let us know."
>Your tests don't sound 100 percent scientific, but
>show show a trend. Now, if commutation (sparking)
>acceptable, you've got something.
>BTW, I didn't realize you had the MTC-4001. The
>factory shift was 4.5 degrees. Did you go 7 degrees
>further? Or total?
--- Mark Hanson <[email protected]> wrote:
> >Hi,
> >
> >I stopwatch checked my acceleration starting in 2nd
> >gear going from 2 fixed points uphill 10% grade
>between my drive & the
> >neighbors. I tried 7 degrees mechanical advance
>and then set it back to >neutral
> >on my Prestolite MTC4001 at 96V E-Porsche 16
>ni-cads. I got 33 seconds at >7
> >degrees and 25 seconds at neutral and it popped up
>my 30% grade garage
> >better too with neutral timing. I checked at speed
>holding hills and it >was
> >at 3600 rpms in 3rd doing 60mph at 250 amps on the
>same section of
> >highway. I noticed a bit drop-off above that speed
>but overall it ran >better
> >with better acceleration set to neutral. I think
>the low voltage and rpm's
> >are the factor.
> >
> >The racers are operating at higher voltage and
> >higher RPM's I believe where the performance is
>noticed about 5-6k rpm's
> >
> >Best Regards,
> >Mark
> >

Pinpoint customers who are looking for what you sell.

1 - 2 of 2 Posts
1 - 2 of 2 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.