A portable engine

[arnoldb]

Hi Rich

I think that would be just dandy for optimum performance without any compensation for lead or lap. Maybe it might be better to add a bit of meat (0.1mm) to the wall thickness on the port side walls - i.e. make the length of the valve 12.1mm and the length of the recess 11.9mm - but that's just me keeping a bit of a machining allowance in mind.

Kind regards, Arnold

Well, Jason beat me, with easier tolerances - you might be better of with those Thm:

 

[firebird]

hi

Thanks Arnold and Jason :bow: :bow:

I'll re draw again maybe tomorrow night and see what I can fit in.

Cheers

Rich

 

[Don1966]

There is a book called "Model Engineering, A guide to model workshop practice" you can get it for $9.95 from amazon. The port bars ( this is the space between ports and exhaust B1 and B2)should never be less in width than the steam ports; the width of the exhaust port (WE) should be twice that of the steam ports. Therefore the width of WE = one-eighth the stroke of the cylinder. The cavity of the slide valve must be exactly B1+WE+B2. The total length (T) of the valve (TV) depends on the lap adapted. The lap in a small power-engine should never exceed half the width of the steam port. (TV) therefore= T+lap1+ lap2. In small and slow model engines and locomotives the length of ports may be reduced to 3/8 or 1/4 of cylinder bore.

I am not trying to step on anyone's toes here as Jason and Arnold are very capable guys and are very good at what they do. I am merely giving you what my manual says. There values are very close.

Regards Don

 

[firebird]

Hi Don

Thanks for the input.

I'm going to study all this for a bit before proceeding.

Cheers

Rich