Pretorian435

Hey, need a little advice... I bent this prop shaft on my Exceed 4ch J3 Cub. I was hoping I could just remove the shaft itself. It has two Allen screws on either side of the base into which it is inserted, but even with those removed, it doesn't budge. How do I get the shaft off?

Thanks!

scooterinvegas

My Feedback: (1)

Repost in the "electric flight" section.

You need to take the motor off the plane, remove the collars, check for E clips and tap the shaft out. When you replace a shaft in an electric motor, you need to replace the bearing too.

AltaTed

Are there any cross sectional drawings of the various types of motors used for electric flight posted anywhere that can be referred to for just such dissassembly work.  I'm sure many of us would benefit from seeing just how these tiny little motors are assembled.

Altaed

eye4wings

Ken,
The cheaper alternative would be to straighten it as it is. Those puny shafts don't take that much effort to bend - just so long as you have enough strength in your fixings and model joint.
If you're nervous about the model's nose strength you could hold the motor in a vice or mole grips (not too powerfully and preferably by the flat over the front bearing).
Maybe use a prop saver next time out?

lorih

I have to disagree with "scooterinvegas". Unless there is something wrong with the bearing, why replace it? When you remove the shaft, check the bearings. I simply insert the lead end of a common pencil and give a carefull twist or twirl. The pencil should just turn silently with absolutely no noise or rough feeling. If you can feel ANY roughness, THEN you must replace the bearing.

Cliff

AltaTed

If you choose to attempt to straighten the shaft. a method I have used to straingten shafts for years is to not remove anything from the motor and straighten by a gentle method  using something with a hole in it as close to the shaft diameter as possible.  Gently torquingthe bent shaft at the bend until it's as straight as you feel you can get it.   then measure by this method....

First,,, be sure your motor is mounted or held very solidly.

Take a hard felt tipped pen and run your motor 1000-3000 rpm and barely touch to the shaft several places along it's length so the marks show only on the high side of the shaft. Use a small rubber hammer and very lightly tap it at the marks. Clean off the marks and repeat several times if needed until you have a complete ring around your shaft and youll find a very nice straight shaft has been accomplished.  Be sure to check several places along the shaft but the perfect place you want the solid ring to be  is the distance in from the end where the prop. will be mounted and turning.

A good straightening tool is made by using a bolt around 3/8" dia. and a couple of inches long. Select a drill not much larger than the shaft dia. you are straightening. Drill down into the end of the bolt a hole almost as deep as the shaft length of your motors bent shaft and you made yourself straightening tool. It does not have to be perfectly centered in the bolt since it's only for getting gentile leverage. A hand drill works fine if you don't have a drill press.  Don't try a wrench or pliers. That can lead to disaster you can't recover from unless you are very lucky.  Always tap using a rubber or small bounceless type hammer.

Pretorian435

Thanks, Guys! I did end up straightening it by hand with, gulp, pliers; very soft. It actually was darn near perfect on, no vibration, blades tracking nicely. Then today I sheared the whole thing off in a crash!* I think where a SF prop would have boken the APC prop was tougher than the shaft, already weakened by the straightening. I have some SF props coming from China...

I did figure out how to replace the shaft. I wanted to learn this as I think it will be a common occurrence. I took the motor apart today after the crash, and it was PITA to remove, but i got the shaft out. Its a 3x50 mm shaft. Took a while to find a replacement, but I did find some 3x47 at HeadsUpRC.

I like the idea of making a straightening tool, but wow... drilling out a bolt is a little beyond me! Surely someone makes something for this?

*If you'd like to read the NTSB crash report, you may find it amusing!

http://pretorian435.blogspot.com/2011/02/icarus.html

eye4wings

Ken,
Sorry to hear of the further mishap!
If you're making a habit of bending shafts I would seriously suggest something like this...
http://www.webx.dk/rc/prop-saver.htm
I thought it had become more or less standard practice on small models... which I rarely do... it's cheaper and less hassle.

AltaTed

Too bad your shaft sheared off but,,,,, you were flying it after straightening it so ,,, you did good.  Knowing how to replace the shaft and finding the replacement is great news. Let us know how that works out.

Pretorian435

Thanks, Guys! The prop saver idea seems pretty neat. If I make a habit of this I will look at that, saw them online.

I did get the shaft out, with a little work. I ordered another engine, but I also ordered some 3x47mm motor shafts just because I like to tinker. Today I visited my LHS and found some 3x47 shock shafts with C clip ends. It wouldn't fit, being 3.17mm... so I ground off that extra 0.17mm (the tolerance on a shock shaft are clearly less than for a motor shaft), and it fits nicely. I ran the motor, and it runs fine, but the stator rubs on the rotor a little when I hand turn it, not apparent when it runs. Very exciting!

The plane is almost back together.