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retiming motors


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Glen
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Joined: 16 Jun 2004
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retiming motors

im looking to retime my fan motor for the spinning weapon full foward.

just wondering how i would go about retiming a motor. is it just as simple as rotating the magnets?

Post Thu Jul 08, 2004 7:15 pm 
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andrew



Joined: 16 Jun 2004
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Location: Castle Hill, Sydney. N.S.W


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Well i wouldnt have a clue mate but how the hell did u get taht kickass picture of cobra there.
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Post Thu Jul 08, 2004 8:43 pm 
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Spockie-Tech
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I dont know if Gary will de-lurk for this one or not seeing as how's the auto-electrician.. but from what I know, you can move the magnets OR the brushes (some motors have rotatable brush plates). Given that the Rotor goes round and round, I would guess that either would have the same effect.

Post Thu Jul 08, 2004 11:12 pm 
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DumHed
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Joined: 29 Jun 2004
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moving the magnets always sounds like hard work - and they need to be aligned perfectly afterwards.

I've re timed a few motors (first one many years ago after I had a crazy idea that if you advance the brush timing then the motor will run higher rpm due to the field expanding earlier, so having peak efficiency at higher rpm - just like a petrol engine Smile)

Much later on I found out that it's common practice for R/C racing people.

With the 540 / 550 style motors you can usually un bend the retaining tabs that hold the back plate on the motor, then rotate the whole thing around (you may need to cut some plastic locator tabs if it has any).

Remember that to advance the timing you want to turn the end plate (or brush mountings if it's a larger motor) against the normal shaft rotational direction.

About 20-25° seems to work the best for very high rpm, but you might want to stick to a bit less than that for most robot uses. Also, with advanced timing in one direction it will obviously be retarded when the motor's running backwards - so you're reverse power output, rpm, and efficiency will be way down.

The best way to set the timing is to set up a generator to drive off your motor, and load it up to keep the rpm where you want maximum power - then adjust the timing till you get the best compromise between output and input power.
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Post Fri Jul 09, 2004 12:06 am 
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Nick
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Since you have a fan motor, it might be good to look at sites that show retiming the EV Warrior. From what I have seen, moving te magnets would be a nightmare - they are usually glued in and immovable. All the info points towards rotating the brush housing.

If you have a fan motor, there's a chance its ALREADY timed to spin faster in one direction. We can test that with an ammeter or tacho- if the current draw or speed is different when the motor is reversed, then the motor has its timing advanced in that direction.
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Post Fri Jul 09, 2004 10:41 pm 
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DumHed
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I pulled apart my saw motor the other day, and it has a big circular plate that the brushes mount on.
It's located by a small tab on the middle housing, and by the two bolts holding the ends on.

By drilling new bolt holes in the brush plate and grinding off the locating tabs it'll be really easy to change timing on it.

One thing I noticed too is that the casing is about 5mm thick steel!
No wonder it's heavy!
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Post Sat Jul 10, 2004 1:00 pm 
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timmeh
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Joined: 20 Jul 2004
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Can i retime my model plane starter motor full forward or at least faster?

Heres a pic of the motor just in case there is any confusion with which motor i have.

http://robowars.org/forum/album_pic.php?pic_id=361
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Post Mon Nov 15, 2004 8:59 pm 
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Knightrous
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Can you pull the motor apart and get us a few snap shots of the brush holder and the position of the magnets?
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Post Mon Nov 15, 2004 9:18 pm 
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timmeh
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Give me 5 mins Very Happy
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Post Mon Nov 15, 2004 9:25 pm 
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timmeh
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Brushes http://robowars.org/forum/album_pic.php?pic_id=363

winding http://robowars.org/forum/album_pic.php?pic_id=362

endcap http://robowars.org/forum/album_pic.php?pic_id=364

Very Happy
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Post Mon Nov 15, 2004 9:33 pm 
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timmeh
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quote:
Originally posted by teamvertex:
Can you pull the motor apart and get us a few snap shots of the brush holder and the position of the magnets?


Any ideas then?
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Post Tue Nov 23, 2004 5:55 pm 
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