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cbusse1
04-21-2007, 06:27 AM
I converted my new 30 year old Honker to electric and on the second rather rough landing the prop shaft got bent. I tried to straighten it by hand and it helped a little but it is still not right and the vibration is pretty bad. It is just a small outrunner motor with a threaded shaft.
Are the shafts easily replaceable? I would rather try to replace the shaft instead of the entire motor. I'm rather new to electric flight so I don't know much about motor construction. Please help.

max2112
04-21-2007, 09:20 AM
cbusse1,
The only luck I've ever had was using a bench vise. Maybe it was a stroke of luck because I've tried this several times and only one attempt came out straight. The other two looked straight but still had a bad vibration.

Just clamp on the shaft with some needle nose VGs and insert it into the vise jaws lengthwise. Tighten the vise as much as you can. Rotate the prop shaft 180. Repeat. keep rotating in small increments and squeezing with the vise. If you get it close it'll roll flat on your workbench with no wobbles.
This can damage threads if you're not careful.

Good luck.

flydiver
04-21-2007, 05:50 PM
Depends-I think a lot of motors you can get the shaft out. If it has a single bend it may be fixable. It it has an 'S' bend (roll it on a flat surface and look underneath), just give up. Some motors have replacement shafts. What kind is it?

Now, the next takes special tools. I have a large drill press and a thing called a dial indicator. I chuck the shaft in the press so the bent part is sticking out and the straight part is up inside. The dial runs on the shaft and measures movement in thousands of an inch. Spin it by hand, find the high/low spot, and start slowly bending it back toward the "middle" so the shaft run is true.

If you don't already have these tools you probably won't want the expense of buying them.

You might be able to "eyeball" the same process with a vise and a very flat surface to check it with but you just won't be nearly as accurate which will play hell on the bearings and motor.

flydiver

Spencer J
04-22-2007, 07:41 PM
I normally use a vise to bend out a damaged prop shaft. I have only bent a prop shaft on my Slow Sticks, and since I use a prop saver, I do not care if I strip the threads on the shaft. Needle nose pliers also work well.

Another killer that I had with my Slow Sticks (when I was in the brushed motor era) is that I would forget to turn on throttle lock after landing, and while changing batteries, I would bump the throttle. This would strip and ruin the gearbox since my leg or the ground would prevent the prop from spinning, and the stronger pinon would take off 4 or 5 teeth off of the main gear. :( Oh well....

Bill G
04-24-2007, 07:01 AM
I've straightened a number of motor shafts successfully, and found that they actually want to return to their original postion. That said, I've found the best way is to pad the surface of whatever you use to straighten the shaft with plastic sheet or hard rubber, since you don't want to point load the shaft, or you will risk kinking it.

Bill

cbusse1
04-24-2007, 07:25 AM
Thanks for all the great suggestions. I ended up using a rubber mallet and it did a fair job. Not perfect, but good enough that it took out most of the bend and vibration.

robosteve2002
05-03-2007, 02:35 AM
I've bent and straighted motor shafts many times...even on motors that folks say that you can remove the shaft. For example, on my esskay 400xt, I remove the retainer pin and place the motor upside down in the vice and drive the bent shaft out with a nail (appropriate size) and hammer. After getting the shaft out I place it on the flat surface of the vice and tap tap tap while slowing rolling the shaft around. After a few whacks with the hammer I usually come out with a reusable shaft. May not be as precision as the original but it works for me.

cbusse1
05-05-2007, 03:35 AM
I don't understand how you can tap on a threaded shaft and not ruin the threads before you get the shaft straightened.

Grasshopper
05-05-2007, 03:45 AM
I've put mine in the chuck in the drill press and slowly turn it by hand looking for the High Side. I gently tap it with a small brass hammer, keep turning it and repeating it until it's straight. If you're really carefull and take your time, you can get them back to within .001" to .002" of runout.

cbusse1
05-05-2007, 05:06 AM
I have a drill press but no brass hammer. I'll have to get one and give it a try. I guess the brass hammer is the trick. If you used a regular hammer I'm sure you would smash the threads.
I do have a rubber hammer that I might try first. I had never considered putting the shaft in the drill press. It's really a good idea. Thanks.....

Grasshopper
05-05-2007, 05:23 AM
A rubber mallet or even a wood mallet will work too. You can even use just a block of wood. You don't have to hit them very hard. Just light taps.

Good luck.

flydiver
05-05-2007, 05:50 AM
I have a drill press and a special measuring device called a dial indicator. It measures run-out in thousanths. Find the high/low spot and I just use a small bar to push it the opposite direction and keep working it until it's straight(ish). Works well with single bends, not so hot with 'S' bends.

fly

robosteve2002
05-08-2007, 07:27 PM
A threaded shaft would be almost impossible due to the damage that you could do to the threads. Depends where the bend is on the shaft. Truthfully, the thing that most folks worry about is just getting the shaft out of the motor. Once you've done this you've already won half the battle. Besides, what do you have to lose anyway? If you try to straighten the shaft and you damage it you will need to buy another one anyway. FYI...I buy my shafts from an online Denver hobby store.

robosteve2002
05-08-2007, 07:28 PM
Great idea! I will try it next time.

Joe 1320
05-18-2007, 07:01 PM
A threaded shaft would be almost impossible due to the damage that you could do to the threads. .

The trick I use is to not strike the threads. Wrap the shaft tightly with small gauge solid wire for it's entire length, make sure the wire wrap is above the level of the threads. A bit of tape on both ends will secure it. Now tap and straighten, any damage from strikes will be to the wire and not to the shaft. When the shaft is straight, uncoil the wire and reassemble the motor. Works like a charm. ;)

Bill G
05-22-2007, 08:48 PM
I just thought of another solution:
Drill the prop hole at an angle, rotate it until it counteracts the effect of the bend, and lock 'er down.:D

Bill G
05-26-2007, 11:33 PM
I just thought of another solution:
Drill the prop hole at an angle, rotate it until it counteracts the effect of the bend, and lock 'er down.:D
Aw c'mon people, somebody post over this.:D
I didn't want it to stay here for 5 whole days.:eek:

Grasshopper
05-26-2007, 11:40 PM
Aw c'mon people, somebody post over this.:D
I didn't want it to stay here for 5 whole days.:eek:

I was thinking more along the lines of boiling the prop to soften it and bend it to offset the bent shaft.

Bill, do you think anyone will take our advice anymore? Do you think they take it any way?:red:

Bill G
06-03-2007, 06:04 AM
I was thinking more along the lines of boiling the prop to soften it and bend it to offset the bent shaft.

Bill, do you think anyone will take our advice anymore? Do you think they take it any way?:red:
Actually that way's a lot easier.:Q

Bill

Flying B
06-17-2007, 11:58 PM
Anyone know how to straighten out a bent stryker c (stock) prop shaft? Is it possible to take it out and replace it, or do i have to buy a new motor?

Bilbobaker
06-27-2007, 07:51 AM
there was an article in a Park Flyer magazine some time ago that walked one through the process of straitening a bent shaft. (inrunner only)
They put the motor in a vice and used a peice of hardwood drilled to the size of the shaft as the tool to fix the bend. A small pipe would work as well.
Using a dial indicator they managed to get it pretty straight.

wjmoore
08-10-2007, 05:48 PM
Ok, now between my freinds and I, we have 2 bent shafts for Stryker C. Has anyone found a way to fix the bent shaft. I have already upgraded mine with new ammo motor, my son just bent his shaft on a landing that didn't seem to justify bending the shaft, but none the less the motor doesn't spin well now.

??PLEASE HELP.....hate wasting money time and again.

Thanks to all.