Dek;

Not having the drawings, but having 1 Sweet Pea, and 2 Simplexes (both variations) in the club, I'd think that the 5" Simplex Cylinders would probably do for the 3-1/2" gauge version of Sweet Pea; the relative sizes of locomotives lead me to think that.

Maybe others with both sets of plans will chime in?

Another JohnS.

Hi, there are a couple of differences, the material being one, the 'Pea' cylinders are normally cast iron and simplex are gunmetal, the bores are the same, but simplex stroke is 1/8th longer (should be adaptable), the only awkward thing I can see is that the steam inlet enters the side of the valve chest on Simplex, through the frames, whereas the Pea inlet goes into the top of the valve chest between the cover and the frames.

Whether there is enough meat on the Valve chest to allow for this inlet fitting on the Simplex cylinders I'm not sure, but you may be able to modify the chest cover to take the steam pipe.

One thing I noticed with mine is that it develops a very high vacuum on the overun with the regulator shut so I fitted snifting valves to the dead center of the chest cover, these if required could always be offset.

Hope this is of help

Lofty