# Dual motors and power



## major (Apr 4, 2008)

Spence said:


> Can someone explain the basics of how the white zombie uses two 9" motors that only put out around 75hp peak, but are able to put out 400hp and 800ft-lbs of torque?


Can you explain how you determined the 75hp peak?


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## major (Apr 4, 2008)

Spence said:


> Can someone explain the basics of how the white zombie uses two 9" motors that only put out around 75hp peak, but are able to put out 400hp and 800ft-lbs of torque?


Hi Spense,

You got my short reply because I had an appointment this morning. Here is the long version.

I really do need to write that book on my nameplate theory J There are, and I guess will always be, those who believe in nameplates and the numbers they see on them. And then there is the real world. They’re not necessarily the same. Just because a motor nameplate says 10hp doesn’t mean that it runs exclusively at 10hp all the time. Just because you read some specification about a 75hp peak doesn’t mean it applies forever and ever. 

Nameplate data and specifications as well as marketing BS and advertisements are fashioned for certain purposes. They probably have some relevance to the actual performance of the product, but maybe not. Much depends on the conditions surrounding the use of the product.

Take a 1 watt 50Ω resistor. Take it out of the package and look at it. Is it dissipating 1 watt? No. It is lying on the table unconnected and has no power associated with it, therefore 0 watts. It is in fact 50Ω within the specified tolerance, hopefully. But it is not 1 watt. If you use that 1W, 50Ω resistor in a circuit where it has 7.07V applied to it then it will in fact dissipate 1W. This condition is “rated” and one would assume that the resistor will function properly and last for the advertised service life.

Now, if you change the circuit and the resistor now has 8.0 volts across it, the power dissipated by the resistor is 1.28 watts. So is it a 1 watt resistor or a 1.28 watt resistor? It is still a 1 watt rated resistor. But it is functioning at 1.28 watts. So it is at overload or operating beyond its specified or nameplate rating. It may function perfectly well at 28% overload. But it may run hotter than intended which could shorten service life. 

The point is that actual performance depends on the operational parameters (the application) and not the specs or nameplate. You can run that resistor at higher than rated wattage and you could provide a cooling system for it and get the originally intended life. 

So I guessing you saw some spec on some website stating a peak power for the Zombie motor. Then you saw an actual or claimed performance number by John Wayland. And John’s number is much larger. John has applied the motor in such a way that he overloads it and is able to operate at a different (and higher) power level. How does he do it? He uses higher than rated voltage and higher than rated current. So he gets higher than rated peak power.

Now John has been at it for a long time. He has learned from years of experience and numerous “incidents”. Each incident is an opportunity for; let’s call it, application improvement. This is like that secret sauce. He and his crew and suppliers make adjustments to the equipment and are able to push the limits. This is how racing works. Yes, it is machine abuse. And you aren’t trying hard enough if you don’t break those machines. I think John has forgotten about that nameplate on his motor years ago. 

Regards,

major


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## Spence (Nov 18, 2011)

major said:


> Hi Spense,
> 
> You got my short reply because I had an appointment this morning. Here is the long version.
> 
> ...


Wow your response is full of intelligence and real world examples; most people say this is how it is and don't explain, but you have done a very good job of explaining. Thank you!


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## Go-carter (Dec 18, 2011)

While were' at it: two motors of the same output mounted on the shame shaft(like white zombie), the torque is duplicated, but the hp stays the same?

Going to run a dual setup as well in my racecar, and just wondering what I can expect.


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## major (Apr 4, 2008)

Go-carter said:


> While were' at it: two motors of the same output mounted on the shame shaft(like white zombie), the torque is duplicated, but the hp stays the same?


2 motors on the same shaft have the same RPM so the torque from each adds for the total torque from the pair, and therefore the power from each contributes. The power from the pair is the sum of the two.


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## Spence (Nov 18, 2011)

major said:


> 2 motors on the same shaft have the same RPM so the torque from each adds for the total torque from the pair, and therefore the power from each contributes. The power from the pair is the sum of the two.


can you give us an example circuit drawing when two motors are used?

Also what does it mean to run dual motors in series or parallel?


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## Coulomb (Apr 22, 2009)

Spence said:


> can you give us an example circuit drawing when two motors are used?


I think that's getting a bit basic. Try here:

http://www.allaboutcircuits.com/vol_1/chpt_5/3.html

Resistor and motors can be connected in series or parallel just the same, except with motors you have to consider the polarity, or they will run in different directions.

My apologies if I misunderstood your question.


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## Go-carter (Dec 18, 2011)

I think what he meant - atleast thats what I am curious about - is that unless I've misunderstood something, many dual-motor setups run the motors BOTH series and paralell, beeing able to switch via contactors. This would give the car a different torque graph, and could probably use the two motors even better.

Now - I know this is basic as well, but how would you wire up something like this? And when would you change between series, and paralell?

...sorry if this is completely retarded, or I've misunderstood things 

EDIT: Never mind, this page explained both the concept and wiring quite easy for me:
http://www.railway-technical.com/tract-01.shtml


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## Coulomb (Apr 22, 2009)

Go-carter said:


> Never mind, this page explained both the concept and wiring quite easy for me:
> http://www.railway-technical.com/tract-01.shtml


Ok, the basics are good, but note that the "transition" circuit is a short circuit across the supply (considered harmful ).

I also initially found the series-parallel switch difficult to follow, but it's just the tiny size of the switches and their unusual form. Once you get what the dotted lines are supposed to represent (the other position of the switch), it makes sense.


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## major (Apr 4, 2008)

Coulomb said:


> Ok, the basics are good, but note that the "transition" circuit is a short circuit across the supply (considered harmful ).
> 
> I also found the series-parallel switch difficult to follow, but it's just the tiny size of the switches and their unusual form. Once you get what the dotted lines are supposed to represent (the other position of the switch), it makes sense.


http://cafeelectric.com/downloads/HB202.pdf See page 23


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## Spence (Nov 18, 2011)

major said:


> http://cafeelectric.com/downloads/HB202.pdf See page 23


oh god... 

Anyway I was just wondering how the application of using dual motors and switching from series to parallel during acceleration increased performance?


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## major (Apr 4, 2008)

Spence said:


> oh god...
> 
> Anyway I was just wondering how the application of using dual motors and switching from series to parallel during acceleration increased performance?


You can get twice the torque per amp with the motors in series for low speed torque and then in parallel get higher power at higher RPM than what was possible when they were series connected (more voltage per motor).


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