Dave,

Welcome to the forum, I should say the propeller goes on the threaded end with the washer, If the other end of the shaft is plain rod you must have a coupling with a grub screw ?

A picture of what you have would help with further advice

Regards Ray

Hi Dave,

I found it's best to do a trial assembly of the whole thrust line : Motor-Coupling-Shaft-Prop'. This should show up where you have 'free play' in the system.

On the pilot cutter, my shaft was about 2-3mm too long to make the prop a snug fit to the bushing. I trimmed the threaded end with a junior hacksaw and filed off the rough edges (Tip: leave the nut on while you saw the end off ,this will help 'de-burr' the cut end).

For your motor end, I would file a small 'flat' on the shaft so that the little grub screw in the coupling has a good 'seat' to bear on. This should help to prevent any slippage between the coupling and the shaft.

All this can be done before the shafts are installed in the boat. When fitting the prop, you can always use a drop of thread lock for added security. I use Locktite (but other brands are available !).

I also found it useful to have a little adjustability in the motor mount, fore-and-aft and side-to-side. One other thing to think of is whether (or not) the motor end of the shaft will be above the waterline. If it's below, I usually pack the two ends of the shaft with a little Vaseline (or, similar). Otherwise, be prepared to regularly mop out…

Please shout if there's too much jargon here…

Regards,

Dave

Dave, Also worth considering, as you can see in the diagram in Colin's post above there is a thrust washer to transmit the force from the prop into the end of the stern tube and hence to push the boat. I would also suggest, if you have the room, to fit one on the other end of the shaft for when the model is going astern. Dave Cooper's suggestion of assembling off the model before assembly is a spot on method of construction. Also worth remembering is that you want to assemble the propeller first, then slide the shaft up the tube with the two thrust washers before finally fitting the inboard coupling. It is then this coupling that determines the longitudinal play in the shaft. Consequently you want this play to be as small as possible, while still ensuring that there is a clearance and the shaft cannot bind. One way is to insert a piece of thin plasticard, say 0.5mm between the back of the coupling and the thrust washer while you hold everything together and tighten up the coupling grub screw. Sliding the plasticard out would then give you a 0.5mm clearance.

You will also have a couple of millimetres of play by repositioning the propeller as you do not necessarily need the shaft to be screwed right down into the hub as the Loctite and the lock nut are holding things in place for you at that end.

Also don't forget to consider fitting an oiler tube.  This makes lubricating the shaft very much easier and you can buy a type that glues on so are very easy to fit.

This is a fairly typical installation.  I have machined up a brass spacer for this one as the engine had to sit a little further forward so the spacer holds the astern thrust washer in place.  Note the glue around the oiler collar.

Edited By Richard Simpson on 04/01/2022 13:49:20