(Edit) Pinion valve rebuilds

[Oscar]

I won't be able to mount it for a couple of weeks

Thankfully my missus and I rarely argue.

My mistake was learning Russian.

[Oscar]

Does anyone know how much play there is on the internal gaskets on the pinion spindle? They've been gradually contracting back down for a couple of weeks now, but are still slightly loose.

Cheers

[Way2go]

What are these gaskets made of , is it neoprene or similar?

If neoprene is stretched it usually has a "memory" of it's original size and will shrink back to this when heated in a hot airflow from a hair-dryer wafted over it.

If you are keeping the rubber parts cold this could be impeding this "memory" effect working so heat carefully applied as above may be the answer.

If you doubt the effect of heat, take a childs balloon after deflation that is wrinkly and use the hairdryer on that and you will see that it reforms as new.

[Oscar]

It's some sort of incredibly hard rubber. They are fitted by warming slightly, then sliding over a sort of sheath to fit onto a sleeve, which is then slid down the spindle to the correct position, and slid off. Don't know if any of that makes sense.

[Defender110]

They are made of PTFE the same stuff they make the white plummers sealing tape out of,

I think it stands for Poly Tetra Floura Ethalene or something like that...over to you Electrokid????

[electrokid]

Very close
polytetrafluoroethylene

Balloons are usually made from latex which is derived from the sap of the tree Hevea brasiliensis which does indeed crinkle after expansion and contraction and the crinkles can be removed by heat. More recently they have been made from synthetic rubbers such as polychloroprene or a mix of synthetic rubbers and latex. Neoprene is DuPont's trade name for it's polychloroprene products.

Not sure how pre-expanded neoprene responds to heat.

Polychloroprenes are a family of polymers so individual manufacturers produce several different mixes which have different hardness and flexibility and other characteristics.

Viton is not a polychloroprene but is still a synthetic rubber which is a mix of a number of different polymers of fluorides but is still classed as a synthetic rubber.

[Way2go]

It's some sort of incredibly hard rubber. They are fitted by warming slightly, then sliding over a sort of sheath to fit onto a sleeve, which is then slid down the spindle to the correct position, and slid off. Don't know if any of that makes sense.

Mmmh....If it's really PTFE as Defender says then heat is unlikely to assist in reforming. PTFE is fairly flexible as plumbers tape because it's thin but thicker blocks are pretty rigid and can even be machined on a lathe.

PTFE is also not noted for returning to original size - could it be that you over stretched it when fitting it on the mandrel? If you think Plumbers tape, when you stretch it - it stays stretched!

This is now not helping I know, so hopefully someone will answer who has first-hand knowledge of doing this job, knows the pitfalls and how to overcome them.

[Defender110]

Hope this helps from the link below you will see that PTFE is; ''A truly amazing material, that can be shaped by compression,
has the lowest coefficient of friction of any solid and is an
excellent choice for gaskets, rings, and bearings''

http://www.dynalabcorp.com/technical_info_ptfe.asp

[Defender110]

heres a much more interesting and detailed link explaining much more about PTFE seals and their creep / memory properties as in;

Because of its chemical inertness, PTFE cannot be cross-linked like an elastomer. Therefore it has no memory and is subject to creep (also known as cold flow). Creep is the increasing deformation of a material under a constant compressive load. This can be both good and bad. A little bit of creep allows PTFE seals to conform to mating surfaces better than most other plastic seals. Too much creep, however, and the seal is compromised. Compounding fillers are used to control unwanted creep, as well as to improve wear, friction, and other properties

http://www.rlhudson.com/publications/techfiles/ptfe.htm

[scarecrow]

I'm a creep
I'm a weirdo-o-o
What the hell am I doing here,
When I don't belong here?

I don't care if it hurts

..... bloomin' song won't get out of my head

NOOO - now I've got Kylie - Can't get you out of my head - that's it, perpetual loop breakdown...

[rayfenwick]

My mistake was learning Russian.

???????

[docchevron]

I'm a creep
I'm a weirdo-o-o
What the hell am I doing here,
When I don't belong here?

I don't care if it hurts

..... bloomin' song won't get out of my head

NOOO - now I've got Kylie - Can't get you out of my head - that's it, perpetual loop breakdown...

Nor should it, Radiohead are genius' of the highest order!

[scarecrow]

I know I was flicking through the TV channels the other day and came across a girl singing it to Simon Cow and Shirley Coal and Williy Walsh.... Imagine my confusion! The girl was quite good too.

[docchevron]

I rather liked Moby's version from Glasto a few years back.

The important question though is: Was the girl signing fit?

[Vanny]

Oscar, i've done the job a few times, sometimes they fit perfectly, sometimes there is still a little play by the time i loose patiance and fit them. I've never had any problems with the loose ones. So long as they are in the right place of course!

I have nipped a new seal before while putting it into the rack, in a hurry, and it hissed a little when changing direction. Eventually i decided enough was enough and swapped the seals again, hiss cured.