# Piston & Cross Head clearance



## portlandron (Feb 16, 2010)

I have built several I.C. engines and now want to try my hand at steam engines. I have a Stuart #10V and #9 (picked up the #9 at an estate sale for less the $20.). 

Before starting about a month ago I ordered "Building a Vertical Steam Engine" and Building the Stuart No. 9. As of now don't have eather of the books and the vendor will not answer e-mails but that's another story.

I started the #10 and have progressed to machining the piston and cross head and have some questions. 

1. The drawing calls for 3 oil grooves on the piston but gives no further information.
  What shape and size should they be?

2. What clearance should the piston have in the cylinder?

3. What clearance should the cross head have?

Thanks for any help!


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## gbritnell (Feb 16, 2010)

The grooves in the piston can be .032x.032. They are nothing more than to hold some oil to help lubricate the piston. With the cast iron cylinder not that much oil is needed. On the other Stuart engines they supply piston rings to help seal the cylinder but they don't have them for the 10 series of engines. As far as piston to cylinder and crosshead to guide I would try for .001 clearance. With no rings or packing on the piston you want to try and keep it a nice close fit. The same thing goes for the crosshead. It takes the side thrust from the connecting rod so that it's not transfered to the piston rod. The looser it is the quicker the piston shaft and packing gland will wear.
gbritnell


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## portlandron (Feb 16, 2010)

gbritnell, thanks for the advise - now back to making chips!


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## GWRdriver (Feb 17, 2010)

portlandron  said:
			
		

> I have a Stuart #10V and #9 (picked up the #9 at an estate sale for less the $20.)


Now THAT is a gloat if ever I heard one! ;D I'm looking for a garage sale Sanderson beam engine.


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## tel (Feb 17, 2010)

> 1. The drawing calls for 3 oil grooves on the piston but gives no further information.
> What shape and size should they be?



From memory - it's been a while since I've been able to locate my copy - the book also suggests the alternative of s groove for soft packing, this is wot I did and 30 years later it still runs as good as the day it rolled out of the shop, AND it's had some pretty heavy runs in that time - one memorable 12 hr non stop and quite a lot of 8's and 10's


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