Model Boat Mayhem
Technical, Techniques, Hints, and Tips => Other Technical Questions... => Topic started by: Ian on June 20, 2007, 02:25:57 pm
-
Hello All,
I am just finishing up my Al Khubar tug, and during some testing I have noticed a little water coming through the propeller tubes. Is a little water normal? If not, can anyone give me some help on fixing this ?
Cheers,
Ian...
-
Yes, a bit of leakage is normal especially if the motor end of the shaft is at or below the waterline. There are ways of reducing it though. One is to put a close fitting washer, say brass or similar, on the ends of the shaft next to the tube. This will bear against the tube and help seal it. Another option is to introduce some grease or thick oil into the tube which will also help prevent water ingress. Don't stuff the tube with grease though as the drag will be enormous. If you do a search on this site there are quite a few entries dealing with this issue. It happens on real boats and ships too!
Have a look at http://www.modelboatmayhem.co.uk/forum/index.php?topic=1153.0
-
Just a quick point Ian. If you go the washer route make sure you do not have things to tight.
I did on one of my prop shafts and it got so hot it took the skin of my finger.
I should try the silicone grease first.
-
One of the single most usefull things you can do is to fit shielded roller bearings instead of bushes. Much better at holding water at bay.
Then a water proof grease is better than oil but it depends on how much power you have available to overcome the drag of the grease. I don't get a drop inside on the steamer and the tube is full of grease.
When I tried grease in the u-boat tubes the motors wouldn't turn! Each one is an individual case that you have to evaluate. By the way the u-boat tubes do not let in any water either now.
-
Hey, Thanks a Lot to all you guys for your help,
I have got some work to do and I am sure there will be no more leaks. I think I will try a little grease first, and look for some brass washers too.
Cheers,
And thanks a lot,
Ian...
-
Hello Ian,
I built a HFM Deep Dive sub which I was lucky enough to win at a HFM open day. The instructions recommended melting vaseline and injecting into the prop shaft. Seemed to do the trick.
Clive :)
-
Clive ive used this method aswell only problem is when the vaseline gets hot due to friction it tends to melt and run everywhere.
Tamiya grease always does the trick for me now
Jay
-
Unfortunately Vaseline is also water soluble - or at the very least, readily breaks down in water.
Incidentally, I'm currently experimenting with oil sold for refilling motorcycle Scott oilers - so far so good....
-Rob
-
Building mainly submarines, I have to make sure my shafts never leak! You can use an oring or better still a Simmerring seal on the end of you propshaft. Just epoxy it to the end of you propshaft, fit and forget, no more messing with oil, grease etc..
-
Mankster - are you suggesting sticking an O Ring on the shaft in place of the washer I suggested earlier? If so, is it likely to wear?
-
You can use an oring trapped between a washer and the bushing on the propshaft and held tight by a nut on the prop side of the shaft. An oring / cupped seal is hard to stick on the motor end of the shfat, unless its enclosed in a carrier like SBS-2 and BHS seals from Subtech. A Simmerring seal is much easier. Yes I guess they can wear out over time. It hasn't happened to me yet. A Simmerring has a spring to compress the lip onto the shaft, so watertightness is maintained even if ther is wear. As The bronze bushing in the average model boat propshaft would probably wear out sooner though.
-
Hi gents.
Could someone please explain the design and application of a simmering seal?
It may be common in naval construction but I have never heard of these seals and I am intrigued.
Many thanks
Tom
-
Hi gents.
Could someone please explain the design and application of a simmering seal?
It may be common in naval construction but I have never heard of these seals and I am intrigued.
Many thanks
Tom
http://translate.google.com/translate?hl=en&sl=de&u=http://de.wikipedia.org/wiki/Wellendichtring&sa=X&oi=translate&resnum=1&ct=result&prev=/search%3Fq%3DSimmerring%2B%26hl%3Den%26rls%3DGEUA,GEUA:2006-01,GEUA:en
-
Fill the shaft with fishing reel grease.
Thin and waterproof!!
Bob
-
I'm trying thick Silicon oil ( nicked from the photo copier repair man! ).
I'll water test next week and report back.....
-
Hi Mankster,
Thank you for the link. Unfortunately the page does not give a lot of information.
Never mind, I was only hoping for some help.
Tom
-
HI ya there Tom
as regards simmering seal I must confess I have never heard of them being called this before ;D its a new one for me - and no doubt others will say 'Of course you have heard of this before - but, Ive always known them as an oil seal' - their uses are mainly in engineering in gearboxes, car engines etc., and as the name implicates it seals the oil in around the rotating shaft keeping the oil in the right place ;D I hope this is the information you are after.
aye
john e
bluebird
-
Thanks Bluebird.
As an engineer of some 40 years experience, mainly in the manufacture and servicing of aircraft and aircraft components I have come across various types of oil seal. I have just never heard of a simmering seal until seeing it mentioned on this thread. That is why my interest was aroused.
I am interested to know something of the design and use of this particular type of seal as apposed to others.
Thanks for you help
Tom
-
I have heard them called "lip seals".
Bob
-
I have heard them called "lip seals".
One or two people on here might find them useful then...
-
I have heard them called "lip seals".
One or two people on here might find them useful then...
I think that boxing gloves to stop the buggers typing might be a better idea.
-
Hi Mankster,
Thank you for the link. Unfortunately the page does not give a lot of information.
Never mind, I was only hoping for some help.
Tom
Hi Tom, no problem. The Wiki entry exceeds my knowlege on the subject. Maybe you can contact the manufacture http://intl.simrit.de/web/public/contact/callback They should be able to give you all the help you were hoping for.
-
They are definately "Lip" seals to the Marine Engineering fraternity.
They are usually fitted in such a location as to require many hours of downtime of a very expensive peice of equipment to enable to exchange of a 2 dollar seal. More substantial ones have a spring backing to the lip but not always.
The arrangement of the lip seal even extends to the multi-lipped variety used on stern seals where you may have 3-4 lips in one seal of maybe 600mm diameter
-
The arrangement of the lip seal even extends to the multi-lipped variety used on stern seals where you may have 3-4 lips in one seal of maybe 600mm diameter
Sounds a bit like a toilet pan connector then?
-
Hi Guys
Do the edges of the seal actually overlap the end of the shaft? (I assume this is the "lip")
If so I also assume that the spring grips on the diameter of the shaft or have I got it wrong?
Thanks
Tom
P.S. the reason for my interest is that I also have a slight water leak problem with the shafts of my Yorkshireman. The problem became pronounced after I fitted a mixer but has diminished a fair bit since I packed the shafts with silicon grease. As always I am searching for another way....
Tom
-
The arrangement of the lip seal even extends to the multi-lipped variety used on stern seals where you may have 3-4 lips in one seal of maybe 600mm diameter
Sounds a bit like a toilet pan connector then?
Not too disimilar an arrangement.
-
Delving into the construction of seals could become a large posting site as there are many - and I mean many different types and for models I would employ the keep it simple method. why/
a too tighter seal will drag on the shaft, cause the shaft to have a wear line (yes rubber will cut into steel etc)
a miss aligned seal will as above but would fail quickly at the tighter point
From reading the postings I think most of the models seem to use a 3mm or 4mm shaft with a tube to match having brass or nylon bushes at each end fitting a greasing port to the inner end would aid filling with light grease (I use spray chain lube) and as "we" all seem to look into the vessel at the end and the beginning of each use why not top up this grease then, both as a lubricant and as a water flushing agent (to stop corrosion if the model is lay-ed up for any length of time).
I know that the SUB mariners amongst us have a different view on things and I think (I'm not sure as I don't use a sub) that they employ a total seal system
this is just the ramblings of ME and my thoughts
Richard,
-
I would definately recommend a shielded ball bearing as a replacement for a brass or nylon bush, especially for a model under construction.
Better alignement and much better sealing of the end of the shaft with considerably improved clearances. Whats more they only cost a couple of pounds for such sizes and can be purchased to replace most common bushings.
Fit these and you don't have to worry about any other form of seal to restrict the shafts rotation.
-
http://www.canalworld.net/forums/index.php?showtopic=9354
-
These prop shafts are a bit dearer than most,But they are in a class of there own. if you are going to put a few hundred hours in to a boat this can solve a lot of problems ,fit and forget.
Peter
http://www.scalehobbies.net/id24.html
-
I would definately recommend a shielded ball bearing as a replacement for a brass or nylon bush, especially for a model under construction.
Better alignement and much better sealing of the end of the shaft with considerably improved clearances. Whats more they only cost a couple of pounds for such sizes and can be purchased to replace most common bushings.
Fit these and you don't have to worry about any other form of seal to restrict the shafts rotation.
Hi, where can you get these shielded ball bearings in small quantities?
Thanks, Pete.
-
I have just ordered of these two sellers They are not stainless steel but cheap enough to be changed every so often.
Peter
http://stores.ebay.co.uk/Technobots-Ltd_Bearings-Steel-bar_W0QQcolZ4QQdirZ1QQfsubZ5QQftidZ2QQtZkm
http://stores.ebay.co.uk/Dinball_RC-Accessories_Bearings_W0QQcolZ4QQdirZ1QQfsubZ7867823QQftidZ2QQpZ5QQtZkm
-
I Dont bother, but i make sure i keep all the electrical bits...reciever etc on a platform [to keep it above any water that leaks in]...and every 45 minutes or so...i just stop the boat and use a syringe to take most of the water out...another trick is to line the bottom of your hull near the propshaft with Thick absorbant kitchen towel..this soaks up a lot of the water...