motor drive ?

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Night Train
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Location: Manchester

Postby Night Train » Tue Jan 06, 2009 2:17 am

You may need to make a shaft that has the female drive on one end and the type of shaft coupling on the other end that you want to use. Then mount that shaft on a pair of bearings and then into a mounting plate that will mount and locate the shaft securely onto the end of the motor.

Basically you will be putting a new end bearing cap on to the motor to take a short shaft. The problems will be that the bearings for that short shaft will not give much support to the shaft so it will not be able to take any radial loads like gears or pulleys unless it has another bearing located at the far end of the shaft that is in a secure housing.

If you have to drive a gear then you may want a shaft that has the female to fit the motor and the gear as close to the motor as possible and the other end of the shaft located into a bearing in the gear housing. The motor will then be mounted on the gear housing too.

Too late in the day to draw pictures so I hope you get what I mean.

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Location: forest hill, south east london

Postby richard » Tue Jan 06, 2009 5:44 pm

yes pretty much the sort of ideas i had,
Find or use the female of the drive peg, on the other side of it weld a shaft with a bearing around the shaft, and the support for the bearing to be attached to the back of the motor casing where the pump used to bolt on.This will serve to support the shaft and stop the two half of the peg comming apart.
The other end of the shaft will need to have the same splined female of the input shft to the gearbox of what ever car i get.
Have to see what can lay my hands on.
What about the spec of the motor, does anything think this will drive a small car ?

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Postby MalcolmB » Tue Jan 06, 2009 6:27 pm

richard wrote:Regarding the spec of the motor it is 80 volt, 15 KW, 220 Amp. 2000 rpm.The motor without the pump is about 10 diameter and 14 inch long.
I do know you can safely overvolt motors a fair degree, but do not how this affects the kw, i would prefer to keep it to spec and hope to be able to use this for to and from work on mainly flat roads at 30 mph for a small 4 door town car, hoping to do this very low cost and not want to have to buy a motor.

That motor sounds like it will be more than adequate for a small car conversion Richard.
Just to give a comparison, I have a pair of (relatively) small motors rated at 36V, 3.7 kW and 130A @ 2500 rpm. I showed photos of the stripped down motors to Jim Husted, who set up the motors for several very successful electric drag racers, and he reckoned each one would be capable of powering a small car, although this will involve advancing the brush timing and adding forced air cooling. But since your motor is already rated for a relatively high voltage and you're not looking for high speeds I believe you could use it as rated and get very decent performance.

It seems a crude measure of performance, but suitability for a conversion can be judged roughly by motor weight, with 40 kg being about the lower limit for a small car (for a series motor at least). The bigger the motor, the greater the thermal mass and the faster the motor can dissipate heat. Obviously there are other factors to take into account, such as the number and contact area of brushes, commutator bar count and the gauge of the windings. Any chance you can get some photos of the brush gear and rotor? Do you know how much it weighs?

A motor that has a continuous rating of only 12.5 kW could well have a peak output of 5–10 times that figure.

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Location: forest hill, south east london

Postby richard » Tue Jan 06, 2009 6:35 pm

I do know the one i have off at present has 4 brushes, not sure about the other one, but will aim to get a few decent picture of both and let you all see them.

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Drive dog

Postby hyve » Sat Jan 10, 2009 2:20 pm

Richard, a small suggestion for when you make your coupling: in the forklift it gets intermittent use so they use this crude slot-drive design, but in a car it will work harder.
For the female part can I suggest you make the ends of the slot closed, to prevent the two halves from gradually springing apart. The torque from this motor could be quite fierce at stall.
If I were doing it I'd look into making a blank end and having it spark eroded for an exact fit, after all the other machining was done and any heat treatment. With all the load going into just two edges on the male dog there will be a wear factor as well, which is why I suggest heat treatment. Spark erosion is not as expensive as you might think and will guarantee a very snug fit all round, where milling would mean making the slot a little over length to allow for the tool radius at the end of the flats.

Good luck !
Peter Ph

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