Westbury Seal by Vixen

[Charles Lamont]

If an edge of the combustion chamber overlaps the bore you theoretically have very little clearance above to piston crown. On the Seagull I relieved the combustion chambers. The last two sections here http://www.charleslamont.me.uk/Seagull/cylinder_head.html explain.   

[Jasonb]

Do you actually need them to be long reach? I've several engines where the plug is quite recessed, even got ones where they screw into a completely separate casting that puts them a long way from the combustion chamber but engine still runs.

Don't know if Jo's cheap far eastern sourced ones do long reach, you may have to PM her as I think she gave up on this thread early on as she could not follow the imperial dimensions being talked about.

[Jo]

I think she gave up on this thread early on as she could not follow the imperial dimensions being talked about.

Too true 

[Vixen]

If an edge of the combustion chamber overlaps the bore you theoretically have very little clearance above to piston crown. On the Seagull I relieved the combustion chambers. The last two sections here http://www.charleslamont.me.uk/Seagull/cylinder_head.html explain.   

Thank you Charles,

There is often a conflict between Westbury's drawings and a CAD drawing created from exactly the same set of his dimensions. The piston crown/ cylinder head clearance for the Seal is one glaring example. It is a case of build it as best you can and sort out the problems as you encounter them. I see how you handled the piston crown clearance and I may need to do the same, when I get there.

Jason/ Jo  I have several sets of spark plugs from a number of different manufacturers including the far east. I will give them a go and see if there is a problem or not.

Sorry about the imperial measurements Jo, too bad you cannot follow them.

Mike

[Jo]

Sorry about the imperial measurements Jo, too bad you cannot follow them.

I am not the only one so many young people and engineers who have lived/worked all their life with metric have similar problems, it is especially difficult converting legacy stuff at such stressing times as this Covid pandemic.

I for one remain hopeful that there will be another generation of model engine makers to come after us and am doing as much as I can to make model engines accessible to them by detailed descriptions of how to make engines and using language/measurements that they understand but sadly with the coming economic depression I see the chances of many taking it up as a hobby as increasingly remote 

Jo

P.S. Did I ever mention the reaction I got when I took a copy of one of our well known model engineering magazines into "work" and the engineers saw the use of imperial measurements , I never did it again

[gadabout]

Mike,
All you work looks so magnificent!!
I used long reach Rimfires from S&S think they were 25$US each.
I had to machine the combustion chambers on mine as the were all a different shape
regards
Mark

[stevehuckss396]

There are cheaper options.

www.miniaturesparkplugs.com


If you click on the blue text next to the picture a pdf will appear with some basic dimensions.

[Vixen]

Hello Steve

Thanks for your spark plug.......plug 

Mike

[steamer]

Mike I purchased a set of 10-40 plugs from Steve.     NICE stuff........just sayin

[Jasonb]

How does the Corian stand up to heat? Mike's engine has the plugs quite close to the exhaust manifold and his engine will be in a confined space with little air flow.

Corian is quite easy to thermo-form and I have had quite a few counter tops made by Corian fabricators who heat form it as well as doing small bits myself and you don't need that high a temperature to get it soft.

[Vixen]

How does the Corian stand up to heat? Mike's engine has the plugs quite close to the exhaust manifold and his engine will be in a confined space with little air flow.

Corian is quite easy to thermo-form and I have had quite a few counter tops made by Corian fabricators who heat form it as well as doing small bits myself and you don't need that high a temperature to get it soft.

Interesting So how does a spark plug with a Corian insulator survive the heat of the combustion chamber?

Mike

[Jo]

Interesting So how does a spark plug with a Corian insulator survive the heat of the combustion chamber?

Think of it like boiling water in a paper cup over an open flame and the paper not catching alight 

Jo

[Jasonb]

Interesting So how does a spark plug with a Corian insulator survive the heat of the combustion chamber?

Think of it like boiling water in a paper cup over an open flame and the paper not catching alight 

Jo

Only until the water boils away.

Corian is generally said to be heat resistant to 100degC but can be damaged by putting a hot pan or curling tongs on it, always tell customers not to put pans on Corian worktops. Only needs about 150 deg C to get it pliable enough to thermo form easily but go too hot and it starts to blister.

[Jo]

Corian is generally said to be heat resistant to 100degC but can be damaged by putting a hot pan or curling tongs on it, always tell customers not to put pans on Corian worktops. Only needs about 150 deg C to get it pliable enough to thermo form easily but go too hot and it starts to blister.

Du Point says their's is good for 175 deg C for a short time, i.e. you can lift something out of an oven put it down and then realise you have done it 

The Seal has a water cooled head. But like the piece of paper over the heat if you take away the water it is a different experiment 

Jo

[stevehuckss396]

The plugs in my peewee have been in there since 2010 and still work fine.