Rule of thumb re. cylinders and pistons
- Bill Shields
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Re: Rule of thumb re. cylinders and pistons
But not enough to allow the oring to roll in the groove.
Too many things going on to bother listing them.
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Re: Rule of thumb re. cylinders and pistons
Thanks guys, I didn't know there were different groove dimensions for static and dynamic applications, I have them now.
- Dick_Morris
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Re: Rule of thumb re. cylinders and pistons
To ensure long life on the O ring, what's the best way to insure the smoothest cylinder walls? Is pushing a ball bearing through with a slight interference a good choice?
Re: Rule of thumb re. cylinders and pistons
In my opinion, that would be an excellent method of producing a superior finish. Instead of cutting, it burnishes.
Interestingly, that's one of the recommended methods of sizing an Oilite bushing.
H
Interestingly, that's one of the recommended methods of sizing an Oilite bushing.
H
Wise people talk because they have something to say. Fools talk because they have to say something.
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Re: Rule of thumb re. cylinders and pistons
That sounds like something I'm going to have to try, thanks.
Re: Rule of thumb re. cylinders and pistons
Look up Model Engineers Handbook by Tubal Cain. There is a section on using o-rings as as piston rings. It gives modified equations for sizing the groove. According to the book standard o-ring grooves result in too much drag.
There is a pdf of the book you can find with a Google search but it doesn't appear that the book is all that expensive to buy.
There is a pdf of the book you can find with a Google search but it doesn't appear that the book is all that expensive to buy.
Re: Rule of thumb re. cylinders and pistons
I was about to recommend looking for the Parker O-ring Handbook (if such still exists), which at one time was the go-to reference for fitting O-rings, but I would try and trust Tom Walshaw's modifications first.
GWRdriver
Nashville TN
Nashville TN
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Re: Rule of thumb re. cylinders and pistons
many years ago, Tom Patton of Kalamazoo Michigan showed me his Pacific cylinder construction (CI) and he used Teflon tape that was rolled into a string and then the string packed into the CI Piston groove and Tom advocated it's construction as superb. The tape was normally used for industrial sealing.
In my employment, we had High temperature seals , and high pressure, that required custom machined rings of Bronze filled Teflon. The material is superb to over 400 degrees. Since I have been out of that Die machinery work for many years, I cannot give current vendors, but found this FYI.
https://www.fluorotec.com/materials/ptf ... lled-ptfe/
Rich
In my employment, we had High temperature seals , and high pressure, that required custom machined rings of Bronze filled Teflon. The material is superb to over 400 degrees. Since I have been out of that Die machinery work for many years, I cannot give current vendors, but found this FYI.
https://www.fluorotec.com/materials/ptf ... lled-ptfe/
Rich
Re: Rule of thumb re. cylinders and pistons
Rich, I'm certain my dad (Tom Patton) used step cut iron rings on both the pistons and piston valves. The cylinders were fabricated with the cylinder bores machined from a continuous cast iron tube and valve cages machined from a bronze bar. The only tape product in the cylinders is a graphite foil tape packing the piston and valve rods.
Pat
Pat
- Bill Shields
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Re: Rule of thumb re. cylinders and pistons
I lap with non embedding compoundDick_Morris wrote: ↑Sun Aug 15, 2021 12:15 am To ensure long life on the O ring, what's the best way to insure the smoothest cylinder walls? Is pushing a ball bearing through with a slight interference a good choice?
Too many things going on to bother listing them.