resitance

[michael burton 1Participant @michaelburton1]

hi many thanks to the replys of my other post much apprecaited, this may seem a stupid quistion but i really dont know the answer, well today my graphited yarn arrived and i proceded to fitting it to the tich pistons what a nightmare of a job first it wasnt 3/16 it came up bigger (is this right) anyways i finnally get thew packing in and would now like to know what is a sensible amount of resitance obvousily it cant be to tight but at the same time i should imagine beening to loose is pointless please help me out with this one thanks to all you have all been a great help so far

 

many thanks mike

[michael burton 1Participant @michaelburton1]

[MICHAEL WILLIAMSParticipant @michaelwilliams41215]

Hi Michael ,

 

Packing with graphited yarn is a black art .

 

The fit that you want on a newly packed piston is ‘ just stiff ‘ in the cylinder bore . Bit difficult to quantify but something like 1 to 2 lbf to move it is ok . After just one steam up the yarn will settle down and run much more easily .

 

As bought graphited yarn can be to some extent ‘ rolling pinned ‘ to a better shape and size – just roll a bit of round bar along it against a clean hard surface .

 

You may wish to consider fitting O rings instead . If you want to do this ask again and I or someone else will tell you how to set about it .

 

MW

[michael burton 1Participant @michaelburton1]

hi many thanks for the reply rolling pin great idea, also they are slightly stiff will roll but needs abit of a push but is getting easier the more i turn the wheels hopefully with abit of air test and some steam up its pipe it will run in nicley.

 

 

many thanks

[Ian S CParticipant @iansc]

Mike the method I was told, and used was , pack the grooves tightly, and using a narrow strip of wood, and a hammer tap it down, but leave it proud of the surface of the piston, then enter the piston into the cylinder (this should have a sharp edge, not a taper that you have with cast iron rings), the edge of the cylinder will shave the surplus of the yarn off. Ian S C

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