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Old Sep 01, 2008, 08:18 AM
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Joe 1320's Avatar
United States, FL, Sebring
Joined Feb 2006
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hextronic 24g outrunner

I've used these in so many applications, but lately I've run into some problems. I keep snapping motor shafts right where they meet the bell. I've pounded the crap out of them in the past and no problems. My latest batch break cleanly even on a good belly flop landing, all I have to do it catch the prop and it's done. Anyone run across this? It looks like the outer shell of the shaft is hardened but the inner part is soft.
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Old Sep 01, 2008, 09:39 AM
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Dr Kiwi's Avatar
Chattanooga, Tennessee, United States
Joined May 2003
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You may need to go to a 3mm drill blank.

http://www.drillblanks.com/metric_sizes.html
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Last edited by Dr Kiwi; Sep 01, 2008 at 01:20 PM.
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Old Sep 01, 2008, 12:55 PM
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anatoly's Avatar
Falls Church, VA
Joined Jul 2006
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I've never broken a shaft on one of these even on a lawn dart, so I'm surprised to hear that. I have prop savers on all of mine so I don't know if that makes any difference.
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Old Sep 19, 2008, 02:12 PM
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I just broke the shaft on mine. It broke really close to the motor...maybe have 1mm sticking out.

I was wondering, to replace the shaft on these is it simply loosen the two set screws and remove? Anyone have any tricks to get it out if it doesn't want to come out easily?

Thanks

Mark
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Old Sep 19, 2008, 11:54 PM
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Livermore, CA
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Quote:
Originally Posted by Igeeky1
I just broke the shaft on mine. It broke really close to the motor...maybe have 1mm sticking out.

I was wondering, to replace the shaft on these is it simply loosen the two set screws and remove? Anyone have any tricks to get it out if it doesn't want to come out easily?

Thanks

Mark
Thats it, just the two set screws. They can be a pain sometimes, they can strip out easy with a old allen wrench or the wrong size. Butch
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Old Sep 21, 2008, 10:10 AM
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Thanks Butch, Ive got the two screw plenty loose and have even removed them and set them aside so they wouldn't get lost. Just can't get the shaft out. Set screws being set haard probably created a burr and I cn't get quite enough grip on the remaining shaft to reak through. Now that you've confirmed that the set screw being removed is all that is need I will try more vigorously
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Old Sep 21, 2008, 02:43 PM
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You can tap on the shaft with a piece of wood or brass. Also, make sure to remove the "C" clip at the end and seperate the the 2 main motor parts. That way your just working with the shaft and bell. Butch
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Old Sep 22, 2008, 08:32 AM
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Thanks Butch!
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Old Sep 22, 2008, 09:19 AM
Jack
USA, ME, Ellsworth
Joined May 2008
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Classic symptoms of a metal tempering process that went bad or was not done right.

Those shafts would be hardened to about the state that the ones you are getting now are in. That would probably be something up around 60-65 on the Rockwell C scale for hardness and leave them very brittle.

They may be ground to diameter in that state but somewhere along the process (before final grinding to finished diameter) they would also be annealed, leaving them at a working hardness that was something in the RC 58-62 or so range. That would leave the shafts still hard but not as brittle.

The drill blanks have been hardened and annealed and should be about perfect for replacement shafts. I made a motor shaft recently and used a thin abrasive cutting disc in a Dremel tool to cut the groove for the circlip. Chuck the shaft up in a drill motor, get it spinning, and just cut a slight groove with the Dremel tool. It will be a little too wide but it will work.

Put a thrust washer in front of the circlip (resting on the inner bearing race), pull those up to eliminate all the play, and then tighten the set screws on the bell end and you should be fine.

I also use the cutting disc to grind slight flats on the shaft where the set screws contact it. And put the blue LocTite on the set screws.

Using the Dremel cutting disc with the motor running is a good way to get a nice square cut off for shortening a shaft and also for rounding and polishing the end a little so the prop can tip off without snagging the end.

Jack
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Old Sep 27, 2008, 12:00 PM
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Jack, thanks for the walk through. I ws pondering the drill bit replacement shaft but couldn't come to grips with the groove for the retaining clip.
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Old Sep 28, 2008, 10:09 AM
Jack
USA, ME, Ellsworth
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You're more than welcome. I usually chuck the drill shaft up in a drill motor and get it spinning too while I am using the abrasive disc. Cut on the side that gets them spinning in opposite directions, use full speed and light pressure on the Dremel (a small but steady and continuous stream of sparks is a good thing). Use a vice and rest your hands and arms on the bench to get a stable position and you'll break fewer of the discs. And use eye protection of course.

To further trim and finish the shaft once it is in the motor, I run the motor and use the flat side of the cutting disc to polish and round off the end of the shaft. If you're using a prop saver and the prop does not tip off the end of the shaft easily, you either have too much shaft hanging out of the prop saver or there is a sharp shoulder on the end that is catching on the prop.

Jack
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