Packing pistons

[Bob LambParticipant @boblamb44747]

I am making LBSC's Mona and have got to the stage of packing the piston grooves with graphited yarn. Last night I just tried to follow LBSC when he says – " the packing rings will stand a shade above the grooves but as you enter the piston into the bore, prod down the packing with a narrow screwdriver ir similar, and the piston will then enter" Easy.

Not for me. I had great difficulty doing this as bits of the packing got stuck between the piston and the end of the bore and would not stay in the groove. The piston just wouldn't go in. I was concerned that the screwdriver might slip and damage the piston, the bore or me. On the one occasion it did go in it was very tight and I think a small bit of packing escaped from the groove in the piston and got between the piston and the bore.

What am I doing wrong? Is there a knack to this? Has graphited yarn been superceeded and would it be easier to turn new pitons and use O rings? Should I roll the yarn in some way to reduce it's size and get it in quickly before it expands again?

Any suggestions would be really welcome – thanks – Bob

[Bob LambParticipant @boblamb44747]

[JasonBModerator @jasonb]

Make up a ring that is the size of the cylinder at one end and tapers out at the other, it will act like a short funnel and guide the packing in, does not need top be very long, 1/4" will do. This is often done on IC engines where the end of the bore is tapered out so getting the iron rings in is easier

The PTFE gland packing is a bit easier to use.

J

Edited By JasonB on 22/04/2012 14:11:22

[Bob LambParticipant @boblamb44747]

Thanks Jason – I'll give it a go and see if I can manage it – Bob

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