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Old Jun 18, 2010, 12:15 PM
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KenS999's Avatar
United States, IL, Huntley
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Help!
How To Straighten Bent Motor Shaft??

Hello,

Is there a tried and true method of straightening a bent motor shaft on a 400 size brushless inrunner ? Hammer? Vise? .... Maybe something more civilized?

Thanks,
Ken
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Old Jun 18, 2010, 12:27 PM
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freechip's Avatar
Canada, ON, Rockland
Joined Aug 2008
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Yes there is one that works extremely well and actual it is the best method available.

Step #1-A Remove motor shaft from motor.
Step #1-B If shaft is bent alot and removal is not possible without damaging magnets, buy new motor.
Step #2 Roll motor shaft on a flat surface (glass talbe) to be sure its bent.
Step #3 Pick-up phone and call LHS or order online a new replacement shaft.
Step #4 Wait for replacement to arrive.
Step #5 Rebuild motor with new shaft.

Or

Use what available to you aka HAMMER OR VISE and try to get it as close to as possible. Bend in the shaft will be less visible on lower KV motor then higher KV motor.
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Last edited by freechip; Jun 18, 2010 at 04:32 PM.
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Old Jun 18, 2010, 12:42 PM
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Boston, MA subburb
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One of the better ways of straightening a slightly bent piece of wire rod (a motor shaft or solid control rod) is sandwich it between two flat, hard surfaces (like the flat part of your vise behind the jaws and a flat, steel bar) and pound the top steel bar with a hammer as you roll the rod to be straightened. Works OK on spring steel used for landing gears but I doubt it would do anything to a hardened steel shaft.

I think you'll find that replacement is the best solution.

Alan
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Old Jun 18, 2010, 12:57 PM
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USA, FL, Lakeland
Joined Jan 2010
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Agree with everyone, it's not really worth the effort to try and straighten it.
If it's not perfectly repaired, along with a vibration, you risk destroying the front bearing, and also take the chance of the armature hitting the windings inside the case.

Granted I straightened more then my share of cheap outrunner shafts, but even those 5 or 6 dollar motors are worth just replacing the shaft.

If the motor supplier doesn't offer a shaft, just go buy a long shaft drill bit in the correct diameter. Cut off what you need and you will now have both a hardened motor shaft, and another drill bit. If the old shaft had notches for a prop adapter or collar, they are easy enough to reinstall with a Dremel.
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Old Jun 18, 2010, 01:36 PM
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United States, WI, Oconto Falls
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Did not read origanal post properly,
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Last edited by wellington53; Jun 18, 2010 at 04:36 PM. Reason: Misread Op post, wrong advice.
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Old Jun 18, 2010, 01:47 PM
And You're Not
Timbuktu, Mali (Happy?)
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Quote:
Originally Posted by freechip View Post
Yes there is one that works extremely well and actual it is the best method available.

Step #1 Remove motor shaft from motor.
Step #2 Roll motor shaft on a flat surface (glass talbe) to be sure its bent.
Step #3 Pick-up phone and call LHS or order online a new replacement shaft.
Step #4 Wait for replacement to arrive.
Step #5 Rebuild motor with new shaft.

Or

Use what available to you aka HAMMER OR VISE and try to get it as close to as possible. Bend in the shaft will be less visible on lower KV motor then higher KV motor.
You missed the step of

Figure out how to get the shaft out of the rotor without destroying the magents, since this motor is an inrunner, not an outrunner.
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Old Jun 18, 2010, 02:00 PM
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O. C. CA
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You are right, this is something everyone has missed, from the motors I have seen, the shaft can not be removed, to be replaced. Many in runners can not even be taken apart.

Quote from above

(Figure out how to get the shaft out of the rotor without destroying the magents, since this motor is an inrunner, not an outrunner. )

H.
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Old Jun 18, 2010, 03:39 PM
Glenn
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United States, WI, Oconto Falls
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Quote:
Originally Posted by Jeffery View Post
You missed the step of

Figure out how to get the shaft out of the rotor without destroying the magents, since this motor is an inrunner, not an outrunner.
Good catch Jeffery, Just shows how we can misread something.
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Old Jun 18, 2010, 04:29 PM
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Canada, ON, Rockland
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Quote:
Originally Posted by Jeffery View Post
You missed the step of

Figure out how to get the shaft out of the rotor without destroying the magents, since this motor is an inrunner, not an outrunner.
The O.p did not ask how to remove it but how to bend it back into shape. So I assumed it was already removed so I made changes to my post.

Funny how our brain just registers the some parts of what we read, Over looked the inrunner part.
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Old Jun 18, 2010, 04:53 PM
And You're Not
Timbuktu, Mali (Happy?)
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We're just "wired" differently. I'm a diehard old inrunner guy who's never really made the outrunner scene. I do actually own a couple of outrunners.
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Old Jun 18, 2010, 08:07 PM
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Wallingford, Ct
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You have to learn to rely on good luck.
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Old Jun 19, 2010, 12:35 AM
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United States, CA, Bear Valley Springs
Joined Feb 2000
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You can get inrunners apart. They went together in the first place, right?

Usually there is some kind of backplate that needs to be removed. Some screw them on and that'll be obvious, others use Loctite or similar to glue the backplate in. Heat usually softens the loctite up enough so that a rap on the opposing end of the shaft will pop it loose. The shaft is likewise loctited in. Usually a press of some kind that is relatively accurate (bearing press) is emploed. Once the shaft is pressed flush with the end of the rotor, a smaller diameter pin will finish pressing the shaft out. At this point I measure the diameter of the shaft and buy a piece of matching drill rod. Some Dremel work later and you have your replacement shaft. Reinstallation is the opposite of the disassembly with cleaned components and fresh red loctite. Or:

Call the hobby shop and buy a new shaft. The old one isn't usually worth straightening out and the more you work it, the less strength the shaft will have and bend easier the next contact. Use directions above. Or:

Go online and order another cheap motor to replace the other cheap motor.

mw
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Old Jun 19, 2010, 09:26 AM
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Allentown, PA
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I have successfully straightened an inrunner motor shaft by clamping the end of the shaft in a drill press and using the motor case as a handle to bend the shaft straight. Start by clamping the shaft in the drill press, then hold the motor case gently and turn on the drill press to observe how much wobble there is. Turn off the drill press and rotate the drill chuck by hand until the motor case is at the far right point of it's wobble. Hold the motor case and push it to the left, going a little past center since the shaft will bounce back. Rotate the chuck again to see how well you have done, and repeat until it looks perfect. The final test is to turn on the drill press again and see if there is any wobble. If there is, just keep trying until you get it the best you can.

Dale
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Old Jun 19, 2010, 10:53 AM
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USA, TX, Spring
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Typically motor shafts will be hardened. By bending them you are cold working them causing possible embrittlement. Also you will likely not be able to completely remove the bend and likely load your bearings non-axially and thus shorten their life. A new shaft is your best bet.

http://en.wikipedia.org/wiki/Work_hardening

http://en.wikipedia.org/wiki/Embrittlement
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Old Jun 19, 2010, 10:58 AM
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Thank You !

Thanks for all the great info, it is indeed helpful.

Ken.
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