PTFE or Graphite Yarn packing?

[tmuir]

Can anyone tell me if there is a benefit or disadvantage of using PTFE packing over graphite yarn.
The reason I'm asking is I just received my gradfathers Stuart 10V he build in the 1980s but it is in need of an overhaul and I'm making a list of what I need to order at the moment.

Besides it being made by my grandfather this engine has another reason its special to me.
When I was 13 I spent 2 weeks with my grandfather in Sydney (I live in Perth about 4500km away) and he showed me his not long built Stuart. As I showed so much interest in it he found and gave me his old 'toy' steam engine.
It is because of this engine I took the interest in model engineering.
If I had never seen it I probably wouldn't have a workshop.

ANd now of course just a few photos and yes the Stuart 504 boiler came with it which is huge!

Here is why I'm stripping it down.

 

[cidrontmg]

Since it obviously will be used with steam (because it has a boiler next to it), I´d use graphite yarn. Teflon is just fine with compressed air, and so is graphite yarn also, but with steam, IMHO, graphite has a slight edge. It will last longer, and it will be easier to tighten when needed. Either one will certainly work.

 

[Chazz]

Very nice work, well worth fixing, even a project or 2 to use that 'massive' boiler?

Curious though, what would have been used\available for packing when these lovlies were built?

Chass

 

[Blogwitch]

Tony,

For 'real' steaming, I would always recommend using graphited yarn. It should give trouble free running for years.

If you are going to consider a full refurbish, if you can, try to obtain some thin (0.005") PTFE sheet for making the gaskets out of. It doesn't deteriorate like paper gasket and doesn't stick to the metal surfaces. It truly is a good replacement for paper gasket material.


John

 

[cidrontmg]

Very nice work, well worth fixing, even a project or 2 to use that 'massive' boiler?

Curious though, what would have been used\available for packing when these lovlies were built?

Chass

Linen yarn, impregnated with tallow (and graphite, if available), was old hat when Watt and Newcomen were building their engines. It has been used "forever" in pumps and pipework.

 

[tel]

My 10V has graphited yarn and is still going strong 30 odd years later, with the original packing, even tho' these days I am an advocate of PTFE.

 

[tmuir]

Looks like it is agreed graphite yarn is the way to go and I agree that the boiler needs another 'project or two' to hang off it.
I'm in the progress of getting myself a better set of BA spanners as the new ones I got a couple of years back are really low quality. I've got my eyes on getting myself a set of Terry's BA Spanners off ebay UK.

I'll make enquiries on the teflon sheet, as I have some but mine is much thicker as I got it to replace fibre washers on toy steam engines.

I'm also debating whether to replace the bolts with BA studs and nuts like it was suppose to be made, but haven't decided yet.

Thanks for the advice everyone.

Tony


Edit.
I have another question.
What size of graphite yarn should I get for the packing on the 10V?
I'm guessing 1/16 as Stuart doesn't say what size their yarn is and at £3 for 6 inch I would rather go to Reeves 2000 where I can get 18 inches for the same price. I always like to buy more than I need with stuff like this as it saves me waiting 2 weeks for it to arrive next time I need some.

 

[cidrontmg]

"What size of graphite yarn should I get for the packing on the 10V?"

I tried measuring mine, but it´s next to impossible :shrug: But it´s definitely thicker than 1/16". It´s actually 3 threads twisted loosely together, and it´s easy to separate just one, or two, of the threads apart and use that, for a narrow groove. I much like it, it can be used for just about any packing, even rather large pistons with all 3 threads, and small glands with one.
Handling graphite yarn will get your hands dirty, and even more if you separate it to three threads. Other than that, I´d certainly go to a rather thick yarn. And there´s soap for dirty hands Thm:

 

[tmuir]

Thanks,

The burner should be operational this week.
I've got some 0.005 teflon sheet making its way over from the US.
I need to order some new nuts and bolts and some studs. I will work that out this week and then place an order for them and the graphite yarn at the same time.

If all goes well I will have the engine running in a couple of weeks.
Then it will all get stripped down, fitted to a newer, nicer looking base board.
I will probably rework some of the pipework, fit a water pump and maybe make provision for a whistle at some point.