Help with Coupling

[Chesterfield Canal PhilParticipant @chesterfieldcanalphil]

hi, I'm new to model boat building and I'm having trouble with my prop shaft coupling. I'm using a standard M4 threaded prop shaft going into a threaded insert for a universal joint but every time I've tested it in reverse it unscrews the shaft. am I best changing it for a plain insert with grub or is there a solution?

Edited By Chesterfield Canal Phil on 26/01/2015 13:14:25

[Chesterfield Canal PhilParticipant @chesterfieldcanalphil]

Help with Coupling

[Dave MilbournParticipant @davemilbourn48782]

Phil

Are you using a locknut between the shaft and the coupling? If not then you should. You could also put a drop of Threadlock onto the shaft before you screw it into the coupling. A locknut and threadlock are almost mandatory at the other end or you'll keep losing propellers at a frightening rate.

[Chesterfield Canal PhilParticipant @chesterfieldcanalphil]

Cheers for that I hadn't used either so going to order them.

[Colin BishopModerator @colinbishop34627]

When you fit the locknuts, ensure that they are positioned to give the minimum play on the shaft so that it can't move backwards and forwards. Lock the shaft up and then just ease it off very slightly.

You will also notice in Dave's photo that there is a steel washer between the locknut and the end of the tube. You need one at the propeller end as well. These are important as they actually transmit the thrust to the model and take the load off the motor drive shaft bearings which will make it last longer. The washers are also very useful in limiting the amount of water that can enter the propeller tube.

Colin

[Malcolm FraryParticipant @malcolmfrary95515]

When using a locknut, it should always be the case that the nut is tightened against the object to be locked, which must be held in place while the locknut is being tightened. I've seen lots of cases where the object just has the lock tightened up against it while the threaded rod is held. This results, basically in a rod with two nuts on it close together, to lock, they need to be tensioned against each other so that both are pushing against the thread in opposite directions.

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