# Prestolite MTJ4004 hydro pump motor for ev?



## ruckus (Apr 15, 2009)

Please.. Anyone?


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## major (Apr 4, 2008)

ruckus said:


> Please.. Anyone?


Hi ruck,

Somehow I missed this post until now. Looks like a Prestolite 7.2 inch diameter motor. Those were strong motors. Used both for traction and pump drives on forklifts. It has 3 bolts per pole, so would be a 7 inch stack like the MTC or maybe a 6 inch stack (core length). The MTC had a 33 bar comm. I'm not sure on this MTJ. Could be a 33 bar, but there was a 29 bar job released for Clark. The 29 bar design would be a little higher speed.

Anyway, this size motor was used for on-road EVs and proved capable of the task. Hopefully it is the correct rotation for ya. If not, it will require internal mod to reverse. And then likely need to reposition the brush for advance in the opposite direction. Most Prestolite unidirectional pump motors in this frame size came with a factory 4.5 degree advance. Which would be good for up to 96 volts. 

If you ventilate this well, it should do close to 200 amps for one hour. Fully capable of handling 500 amps on accelerations, probably higher. You have a good horse there. It should pull strong for ya.

If you can, count the number of commutator segments (bars) and post it for me.

Regards,

major


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## major (Apr 4, 2008)

ruckus said:


> This motor is available (MTJ4004)


Hi ruck,

Me again. Reread this. Appears you have not got the motor yet. And you ask the difference between traction and pump motors. So, I thought I'd add this.

Like you see, forklift pump motors were unidirectional. And, like I think the drive end (DE) of this pump motor will reflect, had internal splines which mated to the male spline on the pump. In some cases, the DE bearing was lubricated with the hydraulic oil. In which case, you'd have to install a sealed lubed bearing. This particular pump motor has a shaft extension out the comm end (CE). Not sure what that was used for in the forklift. Maybe a aux fan or something. I doubt it was the main power output for the motor. The CE shaft may be insufficient size for an EV drive.

So, besides the unidirectional rotation, the mechanical design of the pump motor may give you problems for an EV. But, the electromagnetic design for these pump motors is very good and capable for EV traction duty.

Occasionally, the unidirectional 2 terminal pump motor would be compound wound to limit light load speed and keep the pump quieter. I think the MTJ is series wound, but not sure.

There you go, some more thoughts from me.

major


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## ruckus (Apr 15, 2009)

Thank you for the information.  It sounds pretty good then.?

If it were compound wound, how would that affect things (like power and efficiency)? Would I need a different controller? 

Have folks found a good way to couple to internal spline motors? We were thinking of making the mounting plate ourselves...


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## major (Apr 4, 2008)

ruckus said:


> If it were compound wound, how would that affect things (like power and efficiency)?


Not much difference in power & eff, but less starting torque than a series motor. With that motor if you have a current limit in the controller of 500, or maybe even 700 amps, it won't be a big deal.



> Would I need a different controller?


A controller made for series motors would probably work fine. However the shunt field (compound motors have both series and shunt fields) is voltage sensitive. So, if you plan to run a compound motor above rated voltage, you would have to drop the shunt field voltage. No big deal. If it is compound, you could get it to work. Nobody I know of makes a "compound motor controller".



> Have folks found a good way to couple to internal spline motors? We were thinking of making the mounting plate ourselves


Always a problem, or should I say challenge. Jim Husted of hiTorqueElectric, actually is pretty good at replacing such shafts. There are other ways. Make your transmission input look like the pump 

Regards,

major


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## ruckus (Apr 15, 2009)

major said:


> Make your transmission input look like the pump


Exactly... but the devil is in the details. Anyone do this successfully?


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