Leaking prop shaft

[JonnytheboatParticipant @jonnytheboat]

Hello Folks,

I'm pretty much ready to sail my model of a raised quarterdeck coaster the ' Briar field ' the prop shaft is fairly low in the water as she has a deep hull. I've been ballasting her to get her close yo the waterline and I'm getting a lot of water in through the propshaft. Does anyone have any solutions please?

Thanks in advance

Jonny

[JonnytheboatParticipant @jonnytheboat]

[Colin BishopModerator @colinbishop34627]

Hi Jonny,

Could be loose seals. Also check that no threaded section of the shaft is inside the tube as this allows water in

Very useful article by Glynn Guest here:

**LINK**.

Waterproof grease can help but try the above suggestions first. You should be able to get away with just greasing the ends of the shaft around where the ealsa are rather than packing it which can sometimes cause friction.

In your setup, a small amount of leakage is normal and can be contained by building a small dam across the hull under the inboard end of the tube.

Colin

[ashley needhamParticipant @ashleyneedham69188]

As colin says, a small amount of leakage is something which you may have to manage with.

I use a nylon washer either side of the propshaft bearings at either end with a steel one backing next to the adjusting nut, and adjust the shaft for zero clearance (not tight, just no back and forward movement). teh nylon is water lubricated, and this help cut down water ingress.

Glynn`s afrticle should be read. No one here will agree on the best way forward!!!!

Ashley

[Colin BishopModerator @colinbishop34627]

No one here will agree on the best way forward!!!!

Only in respect of whether or not to use grease or oil and if so, what type and how much.Glynn's (and Ashley's) principles for getting a good basic seal at each end of the tube are recognised good practice.

Colin

[JonnytheboatParticipant @jonnytheboat]

Thank you for the information. I'll follow your advice and also build a dam as suggested.

Kind regards

Jonny

[Richard SimpsonParticipant @richardsimpson88330]

Jonny, can you tell us a little more about the shaft, i.e. does it have plain plastic or bronze bushes in the end or is it fitted with ball bearings? Sometimes plain plastic bushes can be a really bad fit and leak way too much.

The problem with some scale models is that the inboard end of the shaft has to be below the water line and hence unforgiving when it comes to sealing it. The challenge is that is you try to seal the shaft with grease or vaseline to keep the water out you put more load on the motor. If you have plenty of reserve power this might be acceptable.

When I built a raised quarterdeck coaster I used ball bearings at either end and still incorporated a dam in the hull to collect any ingress. On trials though there was no sign of any water coming in. Assuming you cannot now fit ball bearings you have to make the best you can of it. The best approach is to try to stop the water entering in the first place so concentrate on the outside bush. If you get water in the tube it will eventually lead to rusting of the shaft and possible seizure so it is better to try to prevent ingress in the first place. This will require as close a fit as possible of the stern bush coupled with a thrust washer and possible use of vaseline at that end. If that bush is loose then you might even be worth considering replacing it.

As has been mentioned, as many solutions as there are members on here but at least there are plenty of things to try!

[JonnytheboatParticipant @jonnytheboat]

Hello,

It has plain bronze bearings l believe. I’ve ordered up some nylon washers and will build a dam in the hull. It’s a first attempt at model making so l won’t beat myself up about it. I was hoping to use a waterproof shaft but sadly there were none in the country!

[John W EParticipant @johnwe]

hi there

as has been mentioned earlier on, you will get numerous replies with differing methods of sealing prop shafts tubes & lubricating of them. This is the method I have used for many a year and it has worked – for me anyway. First of all, with nothing in the prop tube (no grease or anything) I run the motor, which has been connected directly to a 6 volt battery. In between the connection between the motor and the battery there is an amp meter connected – I note how much amperage the motor is drawing. Golden rule here is – the least amps the better – meaning there is no friction between the motor and the prop tube. When I am quite happy with that, and, done all my adjustments if required to reduce the amperage – I then proceed to remove the prop shaft from the prop tube – and with a syringe filled with grease from the automotive trade (not the heavy grease used for axles on cars – but the brown grease used on bushes) I squirt approx 10cc of the grease into the prop tube and then placing my finger over one end of the prop tube, I force the prop shaft through the other open end of the prop tube – forcing the grease into the tube. You will find that some of the grease will pass between your finger out to the other side of the prop tube. Then, the procedure is to remove the prop shaft from the tube, wiping any excess grease off the prop shaft and then replacing the prop shaft back into the tube. Connecting up to the motor, reconnect the amp meter just to check to see you haven't overpacked the tube with grease. If you have, you will see on the amp meter a higher drawing of amperage. If that is the case, remove the shaft from the tube again and wipe more grease off the shaft. A Slightly higher amperage drawn than originally started with is OK. This is the method, like I say, that I have been using for many a year and I have yet to build a dam in the bottom of the boat for collection of water.

john

[John W EParticipant @johnwe]

Hi again, stage 2 when you are happy with the above.

here are a couple of pictures of the Moray Forth and also the MV Duburg showing the amp meter set up. These models both have the prop tube parallel to the keel and are pretty deep in the water and they don't have water seepage after many years being used.

John

 

 

Edited By John W E on 05/10/2022 16:17:17

Edited By John W E on 05/10/2022 16:21:47

[JonnytheboatParticipant @jonnytheboat]

Thank you John for such a comprehensive reply and I'll certainly give that a go, I'll dig out my multimeter.Your model has many similar features to mine ( I think exactly the same type of shaft and coupling ) and I'm sure it will work. Is that a camera up in the bow, would you mind me asking which camera you're using?

[John W EParticipant @johnwe]

Hi ya there, yes its a camera a Go-Pro – I obtained it from Ebay yay…. it is a cheapy. We fitted it on the model so we could manage a close up pic of some of the wild life on the lake – ducks, baby swans etc – and we managed to photograph/record a good view of the lakeside. Couple of rowing boat sides and that was it.

What I did was make a new hatch that bolts into the model which the camera is fitted into for safety reasons – so, when I sail without the camera, I change hatches.

John

[JonnytheboatParticipant @jonnytheboat]

So filled the prop shaft with light automotive grease. 450 milliamps beforehand and 550 afterwards. Hopefully that's within the ballpark. also fitted nylon washer to prop end of shaft.

[JonnytheboatParticipant @jonnytheboat]

John W E I was taken by how similar the bow and stern of your model are to mine. when I work out how to resize some photos I'll post some.

[John W EParticipant @johnwe]

Hi Jonnytheboat

John here – as all things, whilst looking for something totally different in my photographs/pictures which my Son says I should put in folders to keep them in order – I came across more pictures of the Moray Forth with a go-pro on the deck. Here is one of the pics:

Also, I have been having a nosey in your album I noticed the cargo ship which is in there – looks as though you are building – is the hull of your model made in the 'old' bread and butter way – where planks of wood have been glued together. Looking at your pic it looks as though it is solid timber and not a plank. Is this right?

Nic e model you are doing – keep the pics coming. Easier to put your pics in your album and then transfer them onto the thread you are tying in – just look for the camera icon at the top – next to the smiley – well it is on mine

John

[Richard SimpsonParticipant @richardsimpson88330]

I recently had a play with a Go-Pro Hero Session. A nice little cube version, as with John a second hand Ebay purchase. Not brilliant picture quality but good enough for playing on the pond with:

From Graupner Corvette

From HMCC Badger

Edited By Richard Simpson on 08/10/2022 22:58:45

[JonnytheboatParticipant @jonnytheboat]

Hello both,

Yes, I'm very fortunate that I teach carpentry at an FE college. I was walking past a skip on site and saw two pieces of timber cladding sticking out so extracted then and took them back to the workshop. After pulling out a few nails I allowed them to dry and then ran them through the thicknesser, it turned out they were very clear western red cedar. We took them down to 12mm and I then drew a line plan with horizontal sections every 12mm. Much to my amazement we then imaged the sections and sent them to a guy I knew on our allotments who had a cnc router, without any modification to the images the router reproduced the sections which I then transferred to the timber and cut the out using a bandsaw and a curved spokeshave. I didn't really need to go down the cnc route but I was curious to see if it would work. After that it was all the usual shaping using spokeshaves, chisels ,gouges and a palm detail plane, the trickiest bit being around the stern. I've spent more than I should on brass etch but I wanted to make something that would reflect the glorious models I used to see in the Science Museum as a child. Apart from the struggles with modern technology and prop tubes the build has bee fairly straightforward if a bit time consuming. I'm not beating myself up about any shortcomings in the model as it's a learning process although I think it reflects my ambitions pretty well. Thank you for your interest and support, I really will have to try and resize the pictures.

Edited By Jonnytheboat on 09/10/2022 10:00:43

[John W EParticipant @johnwe]

If you have never worked from a plan and this is all just 'shall we say' from your memory and pictures – you have done a remarkable job on this model.

Do you think, after this model, you will venture on building another one – perhaps plank on frame because judging by what you have done here – plank on frame will be well within your capabilities.

Have a look at Sarek the plan people – on the front page of this forum – and you will see one or two plans of coasters etc. That is, if coasters are your thing.

Lovely model.

John

[Dave Cooper 6Participant @davecooper6]

Coming back to the prop' shaft – I usually angle mine so that the inboard end is above the waterline. Then I put a little "Vaseline" (petroleum jelly ?) at the top and bottom of the shaft just next to the bushes…no leaks so far !

Where you have a prop' in the vertical plane, you could always use a universal joint (eg Huco type) to bring the shaft's thrust line back into horizontal. OK, there will be a slight loss of efficiency, but does that really matter on a Coaster ? After all, it's not going to be planing is it ?

Just a thought,

Dave

[JonnytheboatParticipant @jonnytheboat]

Hello,

It was an important consideration for me to keep the prop shaft parallel to the keel as in the original as l’m going to be spending a fair amount of time looking at the model out of the water. I did think about turning the drive through 90 degrees but unfortunately all this is being done after the model is built, another lesson for next time!

[Richard SimpsonParticipant @richardsimpson88330]

Posted by Dave Cooper 6 on 10/10/2022 11:15:56:

Coming back to the prop' shaft – I usually angle mine so that the inboard end is above the waterline. Then I put a little "Vaseline" (petroleum jelly ?) at the top and bottom of the shaft just next to the bushes…no leaks so far !

Where you have a prop' in the vertical plane, you could always use a universal joint (eg Huco type) to bring the shaft's thrust line back into horizontal. OK, there will be a slight loss of efficiency, but does that really matter on a Coaster ? After all, it's not going to be planing is it ?

Just a thought,

Dave

Dave, if the prop has to be vertical, i.e. the shaft horizontal, a UV joint is not going to allow you to have the inboard end of the tube above the water line. Unless the UV joint is inside the tube and the tube is bent!

[Ray Wood 3Participant @raywood3]

Hi all,

I think each type of craft will be different, Briarfield is horizontal as the original ship, Dave's cutter is a totally different kettle of fish with an auxilliary motor, at least Jonny won't need so much ballast with the bread & butter construction weight.

Regards Ray

[Dave Cooper 6Participant @davecooper6]

Ah ha, Richard is right if you use a single, angled shaft. My cunning plan incorporates a small (horizontal) jack shaft the other side of the U/J coupling….this, of course would then need supporting and sealing with a pair of bushings – one on the prop' side and one on the coupling side.

On second thoughts, it may just be easier to make a miniature mop out of dowel and string and leave that in the engine room !

Ray, of course, also brings some common sense to the thread (unlike my ramblings)…

Happy modelling,

[Andy Stone 1Participant @andystone1]

Ive found with a leaking prop shaft limited success using plumbers PTFE tape wrapped around the shaft, it creates a nice smooth surface and your able to thicken or thin down the shaft to prevent leakage, When I say limited success i mean it only works well on one direction shafts but not so well on forward and reverse drives.

Andy

[JonnytheboatParticipant @jonnytheboat]

Hi All, interesting ti see the other models of Briarfield, you may note mine has a covered bridge, has lost the mizzen mast and gained lifebelts etc. This is because I was making her using the plans from Coastal and short sea traders as well as a photograph I had obtained of her later showing her later on in her career.I am hoping t build another ship, the Scillonian built in 1922. I'll use the bread and butter method as I'm familiar with this method and enjoy shaping the hull. I'll post some more pictures when I finally get around to launching her.

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