propshafts

[HaigParticipant @haig]

Hi Andy,

This is what I have been doing on my model boats and ships.

I use marine grade grease. When I first inject it into the propeller tube and run the motors there is some friction, so I usually run the motors for a few minutes and then it frees up. This is then good for several months. There is no oil slick from grease, but where I have external 'A' frames just before the propeller I usually put a drop of oil on the propshaft at the bearing and that can cause a very small slick.

The use of grease provides a seal against water ingress. This is especially necessary where the inside end of the propeller tube is below the waterline of the boat. I have tried Lithium grease and found it to be very 'sticky' so the friction is a lot greater than the marine grease.

Haig

[Dodgy Geezer 1Participant @dodgygeezer1]

Propshaft Practices.

In an ideal world, I:

1. Arrange for a fairly close fit between prop and prop-tube end bearing.
2. Put a PTFE or Teflon washer in between the prop and prop-tube end bearing. Run it for a bit out of water while pressing the prop to transfer a thin PTFE layer to each metal surface. (do this out of water, since fluid interferes with this process).
3. Coat the shaft with a thin film of Lithium or Silicone Water-Pump grease (to minimise rusting from water which may remain in the prop-tube). This coating does not touch the prop-tube sides.
4. Add a dab of water-resistant grease to both end bearings
5. Assemble and run.
6. IF the prop-tube is below the waterline throughout its length, I add a short silicone tube water seal at the motor end. See the bottom of this page: **LINK**

Edited By Dodgy Geezer on 19/02/2016 13:01:31

[ashley needhamParticipant @ashleyneedham69188]

DG has it bang to rights there, in my opinion, and of course as its a propshaft post, not shared by anyone else(<other than DG> I also use (as a cheap substitute) washers made from plastic milk containers, and arrange to tighten the nuts either end (if fitted) so that there is NO clearance at all (but not tight of course). This obviously does not coat the surfaces with anything, but is water lubricated and thus can tolerate a close fit.

I like the silicone tube arrangement, bit trickier when a nut is fitted to larger shafts at the inner end…unless you find the right size of tube!

The eze site is well worth a peruse, economical boating, and what can be achieved without spending loads. Much of the method can of course be applied to larger craft, and I would not worry about any theoretical inefficiencies in the designs, all the stuff will work just fine.

Ashley

[Len Morris 2Participant @lenmorris2]

Hi Andy,

If your prop is metal then I would use Locktite 601 to stick it on the shaft. It is solid in operation but easily broken with a heat gun. Model submarines need leak proof low drag prop shafts. Many companies sell them but at the end of the day they all use a simple O ring or lip seal at the prop end. You would be quite surprised at how small these seals can get! I bought a 'leak free ' propshaft from a firm in Holland but big doos and little doos destroyed the seal by pulling the threaded shaft through it. A replacement from the supplier was very expensive but my local tool shop managed to source them quite cheaply. Having seen a 'leak free' shaft, you realise that these seals can be easily engineered into any shaft. Hope this helps a little bit and good luck with the build.

Len

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