# More Motor Questions!!



## Georgia Tech (Dec 5, 2008)

I went to look at a forklift motor today is about 11 or inches in diameter. The thing only had 29 com bars is this an issue for running it at 144 Volts? It said it made 23 hp at 36/48 volt at 925 rpm. Will 29 com bar count be an issue for this machine? Any help or comments on this would be HIGHLY appreiciated..
thanks


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## Georgia Tech (Dec 5, 2008)

I was reading a thread where it was mentioned 3.5 volts per com bar. Now dose that mean you take to total com count which is 29 ans subtract 4 (which there are 4 brushes and they short two bars at a time) and get 25 and dived this by 4, to get the potential between two adjacent brushes? Or do you simple take to TOTAL com bar count and divide it by the voltage??? Which is it?


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## booksix (Aug 26, 2008)

I wish I knew but I'd love to know the answer. I'll be watching. Hopefully Jim Husted will show up again one of these days!


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## major (Apr 4, 2008)

Georgia Tech said:


> I was reading a thread where it was mentioned 3.5 volts per com bar. Now dose that mean you take to total com count which is 29 ans subtract 4 (which there are 4 brushes and they short two bars at a time) and get 25 and dived this by 4, to get the potential between two adjacent brushes? Or do you simple take to TOTAL com bar count and divide it by the voltage??? Which is it?


Hey GT,

The volts per bar is just a rule of thumb. Simply take the number of comm bars and divide by the number of poles (which is the same as the number of brush holders). This gives you the number of comm bars between opposite polarity. Then divide this figure into the nominal voltage. So the 29 bar comm at 48 volts is about 6.6 volts per bar. Seems a little high.

The motor with 29 bar comm must have had a multiple turn per coil armature. This armature most likely uses round wire coils and can have soldered connects to the comm. This can be a problem with regard to heating at overload and at higher RPM. I'd look for the armature type using single turn coils having rectangular conductors brazed or welded to the comm having at least 49 bars. 65 or 75 segment comms would be better.

What brand motor was that? Got pictures?

Regards,

major


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## Georgia Tech (Dec 5, 2008)

major said:


> Hey GT,
> 
> The volts per bar is just a rule of thumb. Simply take the number of comm bars and divide by the number of poles (which is the same as the number of brush holders). This gives you the number of comm bars between opposite polarity. Then divide this figure into the nominal voltage. So the 29 bar comm at 48 volts is about 6.6 volts per bar. Seems a little high.
> 
> ...


The armature is the regular one turn type it is a VERY VERY think rectangular gauge bar wire. At the shaft end, or what you call the opposite com end, has welds where the return conductor is another segment that was welded to the top segment. It is a HUGE motor I think the specs on this beats is 17.5 KWatts at 48 volts and 925 rpm!!! Torque for days and weeks!!!!! This thing must have been 12 or gosh maybe 13 inches...The thing was intimidating to look at. 
It is off of a Hyster 10,000 LB forklift with the Hyster part number of 375015 and a GE part number of 5BT1378B3. I TRUELY wish someone could give me more info on this....Yeah for a motor this big 29 com bars was the biggest downer of the whole thing !!! This was the reason for this thread..I'm glad someone took the time to answer! This is a very important topic to me!!!


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## Georgia Tech (Dec 5, 2008)

Hey Major,
take a look at this sight:
I know its in some wierd languge but it some info, its near the end of this document number 375015....any way, have a look and tell me what ya think..

http://www.kelvin.it/attivita/cataloghi/motorixcarrello-ott08/hyster-nacco-yale.pdf


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## major (Apr 4, 2008)

Georgia Tech said:


> Hey Major,
> take a look at this sight:
> I know its in some wierd languge but it some info, its near the end of this document number 375015....any way, have a look and tell me what ya think..
> 
> http://www.kelvin.it/attivita/cataloghi/motorixcarrello-ott08/hyster-nacco-yale.pdf


Yeah GT,

That's a monster. 335 mm dia, 13 inch. With a long stack. Must weigh in at 300 lbs plus (?). Massive current hog. But like you say, gobs of torque. Even at 48 volts, light load RPM must be really high. I guess Hyster had a very large fork truck to need this baby.

I've seen down to 25 bar comms used at 48 volts. And the MTC-4001 with 33 bars did well at 96 volts, when advanced. I've heard of the MTC being used at maybe double that voltage. Perhaps with further advance. Don't know.

But as for that monster at high voltage, guess I'd beware. Maybe if you could get a Zilla 2k. But I don't think your normal controllers would like having that huge rotating short circuit on the output.

Interesting motor site.

major


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## Georgia Tech (Dec 5, 2008)

Major,
you say the Prestolite MTC-4001 has 33 bars this 13 incher has 29 bars......Question, is 4 bars THAT big a differance? Also what was the max voltage for the Prestolite? Could it be that sheer Lam stack, and diameter could make up for poor bar count?
Its possible that I might be able to get my hands on this motor for about 300 bucks!!! Thats NOTHING, worth buying for that price just to say I had the thing.....


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## major (Apr 4, 2008)

Georgia Tech said:


> Major,
> you say the Prestolite MTC-4001 has 33 bars this 13 incher has 29 bars......Question, is 4 bars THAT big a differance?


Hey GT,

I guess it'd be a factor when you reach the limit of flashover. And don't ask me when that occurs. 



> Also what was the max voltage for the Prestolite?


MTC was designed for 96 volts. Had a factory 4.5 degree advance. Some guys go higher and mess with the advance. But I don't know a "max". Might depend what you're willing to live with in regards to durability and life and little things like that. 



> Could it be that sheer Lam stack, and diameter could make up for poor bar count?


I don't see such a thing as "poor bar count". These motors were designed for specific applications. EV dorks take them and do things the designers never intended to have done to the poor little machines. Chances are that 29 bar 13 inch did very well on that monster Hyster forklift.

Regards,

major


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