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[Davo]

The propshaft is a key element of any propeller driven boat, and are available from many suppliers.  My 1965 Sea Queen (detailed in another post here) had a major refit around 1984 which saw an excellent heavy duty prop shaft fitted.  This was from Prestwich Model Boats and included a roller bearing at the top with a 6mm dia shaft.  This was in anticipation of fitting a 15CC Gannett engine I had acquired in un-run condition.  A real work of art.  However, the 10cc Merco remained in the boat until the late 1990s.  It then went electric to enable it be to use a neighbours lake and simplify running.

I decided that, in going electric, it would need a lighter propeller shaft and found that most new shafts were 6mm O/D and could simply be slipped into the Prestwich bearing locations.  It being impossible to remove the Prestwich shaft without a lot of work.  A bracket was made up that utilized the grease nipple and a collar to locate the new shaft.


Recent electric running showed a lot of noise in the propshaft area, and I could rattle the shaft in the bearings.  So a complete new shaft was purchased from a regular supplier.  However, I found the new shaft rattled in the bearings as much as the one in the boat.  (This shaft seemed to have a centre bearing, but this was just left in place.  Maybe replace it in the future).


To try and improve matters, I purchased a pack of 10No Oilite bearings 4mm I/D  6mm O/D x 12mm long.  These proved to be a precision fit on the 4mm dia shaft. Not having a lathe I reasoned I could file a waist on the 12mm long  bearing using my drill. These bearings were a friction fit in the tube. Using the shaft for alignment, I used Loctite 222 (non-permanent) to fit them.  Running the boat in my test tank the improvement was impressive and the boat very quite.  So the bearings were worth the effort.  The threaded prop end goes through the prop to allow a lock nut to be fitted.  Reversing could be an embarrassment if the prop falls off!


I wondered if other builders considered the quality of prop shafts to get the best efficiency out of their electric boats.  Or perhaps made there own.


David


(bearing pic distorted for some reason.  Ends are not 45degrees!)


PS The shaft in question is 18" long

[DJW]

Hi David


Interesting subject.  I like to make my own prop tubes and bearings but I do buy the shafts and props.  I use ball races at the motor end, usually with an oil seal, but I've started to use an engineering plastic for bearings at the lower (wet) end.  My 1/10th Aquarama has clocked up quite a few hours with these bearings, so far so good.  I've also used the same material in the 1/5th:





You do need a lathe, mine is a very modest machine and has no trouble with it.  I use a drill then reamer to get a good shaft fit.  Interference fit in the tube and P bracket.


This is the material: https://www.igus.co.uk/product/barstock_round_rod_X


Best regards
David.

[roycv]

Hi Dave I have been making my own prop shafts and tubes lately.  This was after taking on a donated boat that the builder had ended up with screw thread in the bottom bearing.  I had various spare shafts but found that standard 4mm shaft is often a few thou away from 4mm.  I had to pair up bearings from spare tubes and the game was on, with several variations of tube diameter and shaft diameter. 

Since then for actually smaller boats with prop tubes about 6 - 8 inches I have been given a long length of tubing and bought a similar length of shaft and use brass tubing usually 2 close fit ones and these are the new bearings.  I have also altered 2 motors of the old fashioned vertical red magnet type and I used 2 off 6mm long interlocking brass tubes with a washer soldered on at one end and tight fitted into the motor housing, which was a light aluminium frame.  A disaster waiting to happen!  But I love old electric motors.

The prop tube and shaft with revs around 1000 or so not any noticeable wear.  A friend with a lathe does the screw thread end and I use a plain shaft at the motor end.  I have found that screwing a brass Huco coupling on and lock nutting it in position can put the brass end slightly off at an angle and this causes extra noise and vibration.  I use Huco brass couplings but not the u/j as now I have some thick walled tubing that when cut into 1 - 2 inch lengths makes a quiet coupling, OK for 30 or 40 watts electric but probably not for i/c.
Roy


 
 

[roycv]

I have tried 4 times to upload a small image but nothing happens!
Roy

[dodgy geezer]

I have made my own prop tubes and shafts for many years. It's cheaper, quicker and you get to specify exacly what you want. The EeZeBit boats I make do not have a high power requirement, but they do appreciate a thin prop-tube!

Most of the time, for 2mm particularly, I use the method described by RoyCV - a brass tube with a smaller section of tube slid in each end. For larger requirements I make up a brass bearing insert on a lathe, but occasionally I have used Nylon, which is quite satisfactory. In theory you could make a nylon insert by spinning a chunk of nylon in a drill and using a file.  I have made torpedo shapes this way with a bit of sandpaper.

My prop shafts are usually piano wire, threaded at one end. This is easy to do on a lathe, and even easier if the end is heat-softened first. I have used brass shafts and found them to be adequate for low power use, so long as rapid reversing is not required. It's nice not to have to worry about rusting!

[Colin Bishop]

Ingenious, but not everyone has a lathe. There are plenty of reasonably priced commercial options available If you don't want to make your own.

Colin

[Davo]

Wandering around my local antique store I spied an Ezebilt model boat, the launch version.   And was surprised to see online that they are still available as plans.


KK EezeBilt Boat Kits - Plans


Quite a trip down memory lane to these simple models that must have been the first steps for many into model boating.  It had a flat 4.5 volt battery (in a state of disintegration) with the brass prongs simply pushed through the balsa bullhead and connected with crocodile clips.  But I am sure it gave the builder a lot of enjoyment.
Davis

[dodgy geezer]

 I spied an Ezebilt model boat, the launch version.   And was surprised to see online that they are still available as plans.


KK EezeBilt Boat Kits - Plans

Yup - that's one of my sites. Note that it's changing from eezebilt.tk to eezebilt.uk shortly. At the moment both these URLs work...

[Davo]

I found the picture I had taken of the model.  Asking around 25.00 GBP
These would be lovely models if scaled up to take radio etc.
Thanks for keeping the name going.
David

[Davo]

A few days after the above posting, the model had gone. Not something you would buy unless you wanted to restore it; so hopefully it has a secure future.
David