# Caterpillar AU-2451



## Yabert (Feb 7, 2010)

Welcome
This motor rating of 7kw is probably the intermittent rating.
7kw for maybe 10 mins but after it will need to cool down before restarting to output 7 kw.
Anyway, if it's a 6,7 inch diameter motor it can do a great job for your project.
If there is large copper bars on the rotor and the stator, that mean it's a serie wound motor.
You can find 48v to 72v Alltrax motor controller for this motor type on ebay or many other places, but I will let the other UK peoples give you advice about the ''street legal'' part of your project (you maybe need special certificate).
A 72v controller will work with a 48v battery and give you more power and speed capacity if you use a 72v battery.

Spline, maybe look at golf cart equipement.
Also, if this motor have only two terminals it can only spin one way.


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## darkmunk (Dec 15, 2015)

Thank you.
It's 7" dia x 11" long in total.
It only has the two terminals. Does this mean it can never go backwards? or can I switch the polarity (at standstill)? Seriously, I have a lot to learn 
I think I can get the buggy tested and run it on 'Q-plates'. Insurance might be a problem...


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## major (Apr 4, 2008)

Internal modification is needed to reverse rotation. And you will not find matching spline on a golf cart. Look on a hydraulic pump or industrial /automotive equipment.


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## darkmunk (Dec 15, 2015)

OK. 
Anybody know if this is a series-wound dc motor? I don't really understand the 'things to look out for'.
There's a Curtis SEPEX Motor Controller going, but I don't know if it's appropriate as it says, 'for separately exited motors'. It's not very high powered (48v 500amps), but it'll get me moving.


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## major (Apr 4, 2008)

darkmunk said:


> OK.
> Anybody know if this is a series-wound dc motor? I don't really understand the 'things to look out for'.
> There's a Curtis SEPEX Motor Controller going, but I don't know if it's appropriate as it says, 'for separately exited motors'. It's not very high powered (48v 500amps), but it'll get me moving.


There's about 95‰ chance it's series wound. Possibly compound. Could physically be shunt but they never used those. No chance it's seperately excited. You need more than 2 terminals.


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## darkmunk (Dec 15, 2015)

Thanks.
The Alltrax controllers seem reasonable. If I stick to 48v/650amp controller and gear the motor quite high, so it doesn't have to spin very fast, will it draw a large amperage and produce enough torque for a lightweight buggy? (350lbs I'm guessing)
I like the idea of saving on batteries, but need to hit 40mph pretty comfortably to be any use and getting away from the lights smartly would be fun of course


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## Yabert (Feb 7, 2010)

darkmunk said:


> ... gear the motor quite high, so it doesn't have to spin very fast...


Electric motor are generally more efficient if they spin faster.
For the same price, if you have to choose between 48v-650A and 72v-450A there is no to hesitate, go 72v.
Let say you need 6kw (6000w) to drive at 40 mph, each controller will be powerful enough because 48v x 650A = 31Kw and 72v x 450A = 32Kw.
The difference is to have 6Kw at motor shaft with the 48v system the motor will need 125A and only 83A at 72v*.
The copper lost in the motor will be lower and the efficiency will be higher.
Finally, to have the same acceleration, simply use a proper gear ratio.

*I simplified the calcul for the explanation


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## PZigouras (Jun 5, 2010)

darkmunk said:


> OK.
> Anybody know if this is a series-wound dc motor? I don't really understand the 'things to look out for'.
> There's a Curtis SEPEX Motor Controller going, but I don't know if it's appropriate as it says, 'for separately exited motors'. It's not very high powered (48v 500amps), but it'll get me moving.


I built a go-cart with this motor. Works good, but needs a LOT of cooling... gets hot quick.... even in the winter!

To make a coupler, you need a male 3/4 x 11-spline shaft, which are fairly easy to find. These shafts come hardened, but can easily be welded. 

Keep in mind that these shafts are rather expensive... mine was over $100 USD --- about as much as I paid for the motor.


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## darkmunk (Dec 15, 2015)

PZigouras said:


> I built a go-cart with this motor. Works good, but needs a LOT of cooling... gets hot quick.... even in the winter!


Ah ha, hands-on experience. Awesome 
Did you cool yours, or just let it cool down?
How much power did you feed it?
Your post suggests it's not ideal for a buggy, if it gets hot in a kart?


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## PZigouras (Jun 5, 2010)

It's not so much about buggy vs. go-cart, as it is about not letting it run for more than 10 minutes straight. 5 to 10 minutes is all you can do (no matter what the application) because the internal fan sucks.... its flow rate is probably less than 60 CFM at full speed.

I ducted a 3-inch marine blower into the commutator end... that was a pain... plus I had to add another 12v battery just to run the blower. But it did allow me to run it continuously.

There is nothing fun about this motor, unless you want to run it for short bursts. By short I mean like 40% duty cycle. I was running 48V of lead, but I did not have a current meter on the cart. Judging by the wire temperature, it was probably pulling 90 to 130 amps most of the time.


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## darkmunk (Dec 15, 2015)

Ok, thanks. That's a bit disappointing to hear.
Was your kart fast enough with 48v?


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## PZigouras (Jun 5, 2010)

At 48v, it takes off like a bullet... there is not a gas cart on the street that can keep up.

It probably would have worked just as well at 36v too. Overall, the performance is great... the installation took some effort, however.


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## darkmunk (Dec 15, 2015)

Do you think I can wrap cooling tubes around the outside? or do I have to force air through the inside to get it cool?


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## dcb (Dec 5, 2009)

since it is already open frame, forcing more air through it makes the most sense IMHO, and you can cool it independent of rpm. FWIW most dc air cooling I've seen forces the air towards the brushes/commutator. water jacket/tubes won't help there. https://www.google.com/search?q=war...X&ved=0ahUKEwjlnomS76TKAhWFrD4KHRGOCyEQsAQIMA


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## darkmunk (Dec 15, 2015)

Thanks guys


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