I have used this type of coupling on many of my models both brushed and brushless and agree they work well. You may need a lathe to make the metal coupling or you can use the commercial brass type with silicon fuel tubing. I have drilled a small hole through the coupling and used a brass pin to stop the tube from slipping but this is probably only necessary in very fast racing craft which I don't sail. I agree with JB if you have vibration it is probably caused by misalignment/badly fitting bushes/bent prop shaft/worn bearings or unbalanced prop.
dave976

Hi Roger, no worries using the idea, that's why I put it up, as many people have had the same problems I've had with the Chinese stuff,(with planes and boats) As long as your tubing is a good tight push fit it should hang on ok, but if you can fit those really small zip ties, just place the zip locks at 180 deg to each other and they should be fine. You can also experiment with the ties for any fine balance required, -leave them only just tight enough to be able to move them, and move them round alternately 30deg at a time to see if there is an improvement (if it's not way out). If you can get 2 small ties on each end 180deg apart, you have more balancing opportunities. I've balanced 46 diam outrunners like this. You also need to check the shafts, - rolling them on a flat surface with a light behind is a good way to spot any bowing,- doesn't take a lot to cause vibration (gets worse the higher the revs).

You might need to manipulate the silicone a bit on the splines if it's been in a tight coil, as it can cause a small vibration initially,- usually sorts itself out though. You could fill the inside gap up with silicone (or a piece of smaller tubing) which might stop it twisting on hard starts if you have a powerful motor, but it's probably not necessary if you use the thick tube . Cheap as chips to experiment with, and once you have the size, you can cut a bunch of spares for the tool box. Hurts nothing if it breaks. If you hear it squeal just back the throttle off, it will be the silicone slipping (automatic throttle control 😁) Good luck with the experiment.

JB

what a brilliant idea
I've just purchased a bonded HD coupling to swap over from the mechanical monstrosity that rattled like an old diesel engine in my ORCA build. but i still notice a vibration in the shaft. on further investigation i have found that the bonding of the rubber to metal of the three parts of the coupling are not inline. although i took great care to line the prop shaft to the motor shaft in all planes, this defeats all my own hard work.
but within a couple of days of my disappointment along comes your genius idea. i hope you don't mind me trying this system out for myself, as i have the splined brass end joints all I need is some silicone tubing.
a couple of questions 1st though
1, once the silicone tube is fitted over the splines and because of the diameter of these splines quite a large cavity is left inside the tube, do you fit a smaller tube inside to stop it collapsing under torque?.
2, you say you will zip tie the tubing to help grip the splines. will this not cause imbalance with the zip tie locking catch being on one side, and especially one being at each end, or are they opposite each other, to counteract themselves.
or, in the end, am I worrying to much.
Regards Roger

Thanks JB, suspected it might have been you.
Am pleased it worked out. The idea is a good one and one I might pinch for a future project.
Thanks again.
Rowen

Hi Rowen, might have been the one I made, using large diameter silicone tube on splined aluminium end pieces I made . You could probably use the Radio Active brand ready made splined ends for the plastic universal joints from CMB and use silicone instead of the plastic coupling. I used the 12mmx6mm automotive tube and made the ends to suit. Works pretty well, although had an accidental failure with a big overload on the coupling (about 40A), while in the test tank, but that was with the ends just pushed in and not zip tied.

Aluminium ends were reamed for a precise fit on the motor and shaft. Most of the usual Chinese universals are useless for high speed, as they have far too much movement all round (the rattling sound you hear in a lot of models). Only really suitable for cars or slower speeds. This one has been run to around 30,000 RPM unloaded. I've put this info in the Hartley cabin jet boat blog. Good thing about a silicone coupling is it has a built in safety release if the prop jambs in weed etc (depending on your motor power and the size of tubing you use) and is cheap and easy to replace. I have a meter of the tube, so lots of replacements in that if necessary.

JB

Some time ago was in contact with a member about couplings.
Think it might have been jbkiwi , but not sure.
Anyway, they were hoping to try plastic tubing fitted over the splined hub of standard prop shaft fitting.
Never heard anymore- was this successful?
Thanks
Rowen

A simple and reliable alignment method is to fit telescoping tubing, be it brass, aluminum ect, to both the prop shaft and the motor shaft until the tubing fits snuggly on to each. Essentially it directly aligns the shaft to the motor. Once done, adjust, presumably, your motor mount to align with your shaft and fix into place. Once the glue has dried, remove the tubing by withdrawing your shaft and reinstall same, but fit your universal. Alignment should be very close with little to no angular offset to be taken up by the universal.
Hope this helps.

Thanks Steve for your thoughts. Appreciate the identification of the coupling type.
Agree with your recommendations on alignment. Guess to paraphrase a military expression "Time spent on alignment is seldom wasted!"
That coupling seems to accommodate any slight mis match by straining as you suggest. The Hookes joint type absorbs it by speeding up and slowing down every half rpm. Accounting for the noise and vibration.
My first experiences of the "stepper motor" type coupling are encouraging. So much so ordered a spare set yesterday. They are inexpensive anyway.
Biggest concern is if any straining will ultimately result in fatigue, which might cause failure.
Time will tell.
Cheers
Rowen (right way up!)

Hi RHBaker,
The coupling on the right of your photo is a zero backlash coupling mainly used for servo or stepper motors connecting to a ball screw on machinery, there is nothing wrong with using this type of coupling except it does require a high degree of alignment in both planes (best done with a dial indicator) between the driver and driven shafts.

It may be quieter even with some misalignment possibly due to the coupling "straining" this may transfer forces onto the motor bearings or shaft bearings therefore making it quieter.
A simple test would be to use an Amp meter, running the motor with the new coupling then perhaps free then with the old coupling comparing the findings, this should give you an idea if unwanted force is being used to spin the prop shaft.
Alignment is always critical what ever coupling is being used.
Cheers,
Stephen.

Thanks Rowen will look for them.
Rick