15cc Seal Help

[Vixen]

Hello Mark

Thanks for your help and advice.

Following your suggestion, I have just drawn up the valves and find the tappet buckets would be too long by 3/64" (0.047") if made to Westbury's dimensions.

I will have to wait for another two weeks (or longer) to see what Kirk's new batch of castings look like.

Mike

[gadabout]

Mike,
So I didn't stuff up then!
I think I will take mine apart and fit ball races with seals too to the crankshaft which will mean deepening the end bore to accommodate the slightly wider bearing as when it sits at 6 degrees in the boat oil seeps out the bearing behind the flywheel. Also I would like to fit a float chamber to the carb as it tends to flood when the fuel level in the tank is above the needle valve.
Mark

[Vixen]

Hello Mark,

I'm only going by my CAD drawings based on Westbury's dimensions, and I believe there are quite a few dimensional errors. The trick is deciding which ones are bad.

Are you thinking about rubber seals or metal shields for the new bearings? If you are careful you can pull out the rubber seal from one side to reduce drag.

How would you get the fuel into the float chamber? Maybe you have the space available to lift the tank above the needle valve level and use gravity.

Mike

[steamer]

Stay on it Mike!....

[Vixen]

Hi Dave,

The more I look into this, the more I am sure that the Westbury con rods for the 15cc Seal are actually 1/32" (0.031") too long between centres. Most folk build to print and only later discover the pistons protrude above the cylinder block by that amount. They then need to compensate for this dimensional error by deepening the cylinder head pocket to suit. It is a 'fix' that works, but hides the fundamental error.

I will be making my conrods to the reduced length to attempt to get the pistons flush with the cylinder block at TDC. just like the Seal Major, your Wallaby and most other engines.

If I have it all wrong, then others can learn from my mistakes.

Mike

[steamer]

Thanks Mike!    we'll sort it out.   I'll get back to the Wallaby eventually.....Gotta help my Daughter first

Dave

[gadabout]

Mike, Yes I will probably lift the tank a wee bit more if I fit a float chamber and let gravity work. Thinking of using the rubber seal bearings with one side picked out.
I'm not totally sure now how deep the combustion chamber was as cast now but from memory you might struggle to get it machined up clean if you go with not having the pistons pop out, as usual with castings there are compromises to make!!  Make sure there is clearance from the bottom of the pistons to the crank if you shorten the rod length, I know mine ran very close
Mark

[nj111]

Mark, the crankcase oil will easily find it's way through the remaining bearing race rubber seal, so you'll need to fit a thin section conventional oil seal as well,  Nick

[michelko]

Hi mike,
since i built mine from whole Scratch and converted to metric i canīt say whats right or wrong.
I made my pistons flush with the sealing face of the head.

That worked for me and the engine.

Regards Michael

[gadabout]

Nick ,
 I don't  think there will be room to fit a conventional oil seal in there. I have google searched and am having trouble finding a thin one, the size needed would be .375" id by .875", anyone suggest where to get one?
thanks
Mark

[Vixen]

Hello Mark,

Still looking for a thin section lip oil seal?. However, there is still a reasonable space inside the recess behind the flywheel, could you remake the 'rear main bearing housing' to accommodate a thin 'O' ring instead. You would need to choose a hard rubber and adjust the groove dimensions to get a very light nip on the crankshaft, all to reduce friction.

An alternative, more pragmatic approach, may be to reinstall the whole engine so it sits level in the hull and use a flexible (universal) joint between the horizontal engine and the sloping stern tube.

Mike

[Vixen]

Hello again Mark.

Would this 0.375 x .0.875 x 0.25" lip seal be of any use? http://www.wychbearings.co.uk/w08703725-r23-nbr_oil_seal.html

If you look at the bottom of their page there are some alternative material types of the same sizes to choose from.

Mike

[gadabout]

Mike , I have found some .375 X .563 X .0935 seals that will work but I will probably need to make a new rear bearing housing if I fit it after/behind the bronze bush that's behind the ball race!!
It would probably make it easier to mount the motor level but once underway it's going to be out of level again anyway. Want to make it look reasonably like the full size boat that I am modelling it after
Regards
Mark

[michelko]

Hi guys,
i fitted my seal with an 10-14-3 lipp ring at the flywheel side.
Works  nice, no oil leacking.

Regards Michael

[gadabout]

Michael,
That's pretty much what I am going to do but with an imperial size seal.
Regards
Mark