3.17mm (1/8) Shaft Couplers/Uni Joints

[Tal]

I'm running a sealed thruster housing (although I'm not really sure on how I'm setting up the seal yet...) and I need to run a drive shaft from the motor to the prop. The motor shaft is 3.17mm (1/8) and the drive shaft will also need to be 3.17mm (1/8) for the prop assembly. My problem is that I cannot find a 3.17mm to 3.17mm(or 1/8) coupler, or universal joint, anywhere. I also tried searching for a shaft extension with no luck. Is there a special name for this?

The closest I got was a 3.17mm to 4mm coupler, which is all fine, but I've got 2 thruster housings which would mean doubling my expense, because I could run a 4mm shaft but then need to switch back to 3.17mm for the prop assembly. Can anyone point me in the right direction? or is there another way of approaching this problem that I'm not aware of. I'm new to ROV's, and this is my first build.

[gumma]

I had a similar problem, i purchased M5 propellers and had 4mm motor shaft. I couldn't find right right couplers (M5 to 4mm shaft) so i purchased 3.175 to M5 propeller adapter and I abraded motor shaft from 4mm to 3.175 mm. I think you won't find 3.175 to 3.175 adapter so buy new propellers (M5) or find someone who can make custom adapter on lathe machine.

[scubersteve]

or you could make yor own couplers...
find a piece of thick walled tubing and drill it out to the required I.D., drill two more holes perpendicular to the bore and thread them for set screws.
You could even start with a solid piece of metal, but using tubing of some sort would help keep the bore centered and therefore better balanced.

or start with these...
http://www.ebay.com/itm/Nickel-Plated-B ... 27ca7f0c57

That would be my approach.

odd that you can't find 1/8 to 1/8 couplers...

[amarillo_rocket]

I make my own. I use a 1/8" id piece of brass tubing then put a piece of 3/16" id brass tubing over it for strenght. Drill a hole through the tubing on both ends a use model airplane wheel collars which has setscrews. If your prop is threaded you can get a die and thread a solid piece of 1/8" brass rod then instead of running the 1/8" tubing the entire lenght you cut it in half and sub in your 1/8" threaded rod on one end. Of couse this will all need to be soldered together. I put a nut on the threaded prop end with loctite and have not had a prop spin loose.

[Tal]

Thank you all for your feedback and suggestions,

As is usually the case, outside events led me to a solution.

My prop assemblies arrived in the mail and while they were suitable for my drive shaft, the shaft inside the prop housing was too short for my propellers. With these unusable it made my decision easier. So, as I've updated my project posts, I'm switching the entire thruster assembly to 4mm, with 3.17mm - 4mm universal joint ordered, already have the 4mm shaft, and ordered a couple of new props suitable for a threaded 4mm shaft (that include grub screws as well). So I guess I've followed Gumma's advice

Thanks to you all again, for taking the time to give me your advice and passing on your experience.

[gumma]

YEEEEEEEEEEEEEEEEEEEEEEEEEEEEEE!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!