piston ring size

[tarawa]

I am in the process of building a copy of the Henry Ford engine. I decided to try to use as much scrap steel that I have laying around the shop. I have seamless tubing that is a little larger than the plans called for, so I really cant use the piston rings that were included with the plans. I have cast iron round stock which I will attempt to make piston rings from.
Is there a rule of thumb or calculation that will tell me the optimum OD and ID diameter for a given bore size? I dont want the piston to be too loose or so tight that I cant install it correctly. Or even worse, break the rings after making them.
Thanks in advance.
george

 

[bobsymack]

I built one of these engines and I just used a viton o ring instead of a cast iron ring and it seems to hold up well, hope this is of help and good luck with the build

 

[Lakc]

Yes, there are pretty tight tolerances to the dimensional relationships of OD, ID, height and thickness, as well as gap and fixture dimensions to heat treat them for the proper stress relief. I think there used to be an excel spreadsheet somewhere in the files section with all that information. If your designing from scratch, you definitely need that sheet, or Walshaw's equations to rewrite a spreadsheet for yourself.

 

[Lakc]

Duh, googled "Walshaw trimble piston rings spreadsheet" and it points back to my own thread!
http://www.google.com/url?sa=t&rct=...k85UIylYkowxa8KUwOeoQtw&bvm=bv.47380653,d.dmg

I think thats a sign of old age......:wall:

Anyway, you have to belong to the yahoo group "Min_Int_Comb_Eng" to get access to that spreadsheet so sign up.

 

[stevehuckss396]

Is this the one you are looking for?

View attachment Piston Ring Design.xls

 

[Lakc]

Thats not the one I use, although it may work, and has the same name. Its the one by phillip_burman in the files folder of Min_Int_Comb_Eng. I would repost it here, but fairly certain that would upset some people over in the Yahoo groups, nonetheless not having the permission of Phillip who obviously put a whole lot of work into it.

 

[tarawa]

Piston ring making is much more complex than I imagined. I found a site (Otto Engine Works) that seems to stock piston rings. Hopefully they have rings to match the cylinder /piston combination that I am going to use. Using an o-ring instead of a piston ring is also an option. Thank you for all the good information.