[Mark Scrivener]

My Aster Alisan Shay uses "Graphited Yarn" for piston rings and as a substitute for O rings on the throttle and blower valve. The valves are less of a problem as I could always cut an O-ring grove. But for the pistons one needs a good seal and low drag. Any suggestions? Where does one find "graphited yarn" and what other materials would work for piston rings?

Thanks,
Mark

 

[Nick Jr]

Mark, I just ordered some (among other stuff) from Bruce Engineering in the UK. I would think there is someone in the US that carries it also.
www.pollymodelengineering.co.uk Nick Jr

 

[SteveC]

Mark

Don't know if this is correct, but if you put Graphite Yarn in Google you wind up with a bunch of hits, the following is but one.

[url]http://www.sepcousa.com/products/packing/graphyarn.html[/b][/url]

 

[Guest]

Actually, the O-rings are a substitiute for graphited yarn. This common material and will be available at any domestic plumbing supplier or hardware shop worth its salt. It will be larger diameter than you simply separate it into strands, or you can easily make your own with graphite flakes and the yarn of your choice. It's odd to me why folks want to send half-way round the world for something that's available down at the village hardware.

 

[Guest]

Mark, for the valves use teflon round valve packing. The later Aster Shays used this and it can be cut and seperated along its length to make smaller diameters for any size valve packing. The stuff will pull apart just like string cheese.
Dan

 

[HMeinhold]

Mark,
some people just twist common Teflon tape and use this as packing. I did this with my Mamod (new pistons) years ago and it is still OK. And yes, I know mentioning a Mamod in relation to an Aster is a big no-no

Regards

 

[Steve Shyvers]

Mark,

Try teflon per the recommendations. I made some "graphited yarn" from cotton string and graphite that was sold as a lock lubricant (came in a small bottle from hardware store). The cotton string was separated into individual strands and placed in a small jar with the graphite, and then the jar was shaken to coat the strands with the graphite. However never was satisfied that I got the graphited starnds packed to the correct tightness for properly sealing pistons, but maybe I was in too much of a hurry and didn't take time to experiment. (It's messy to work with too.) For packing homemade valves (with imperfect design) I found teflon tape to be easier to use and more effective.

Steve

 

[Mark Scrivener]

Thanks everyone. I think I'll try the Teflon tape route first.....now If I could just get it to stick to the pistons ;-)

 

[Mark Scrivener]

Well, the Teflon tape was easy enough.....but I have a new challenge. The cylinders on the Shay are cast and have brass sleeves. I noticed that the sleeves can slide back and forth and obscure the steam ports. Upon closer inspection I noticed one of the sleeves was copper while the other two were brass, one cylinder has a lip at the top to limit the upward travel of the sleeve, one has a lip at the bottom (but not the top) and the 3rd has no lip top or bottom. Me thinks the sleeves were added by a prior owner as the Aster assembly drawings only show a cast cylinder and does not indicate a sleeve.

So....I now need to find a way to keep the sleeves from obscuring the steam ports. My first thought was to cut longer sleeves that were the proper length and cut a recess for the port, but the sleeves could then rotate and seal off the port. Glue? press fit?

 

[Guest]

You'll need to make new sleeves in order to get a press fit. If you have the tools and ability to make sleeves I would recommend it, to get rid of the brass and copper, both of which make poor cylinder material, especially the copper. Pick up a few bronze sleeve bearings and make the liners from that, but don't use a sintered "Oilite" type bearing.

If you need to keep what you've got, use Loctite.

 

[HMeinhold]

Mark,
McMaster has a wide selection of bronze bushings. See e.g. 6381K468 for reference. We bought these bushings to repair Eric's Falk cylinders. Loctite should be OK to keep them in place.
Regards

 

[Guest]

Why order stuff like this from half-way around the world or from mega-industrial suppliers? These are common household and motor repair shop materials. A good local hardware or farm&home will probably have it in those cabinets of screws and things in slide-out trays. If you are in a larger city a general "bearing" supply house will have a bewildering selection of plain bronze bushings.

 

[HMeinhold]

We both live in the Bay Area and McMaster is in L.A. We usually get stuff from them in one day. More convenient than checking local guys who usually don't have what we need anyways.
Regards

 

[Kovacjr]

How about this from Loctite

http://www.rshughes.com/products/079340_62015.html

good to 450 degrees

 

[Mark Scrivener]

Interesting....seems there is a loctite compound for everything.

I happened to have some Loctite 515 "gasket maker" compound handy, so I gave it a try. Given this stuff is for IC engine gaskets, it should tolerate heat quite well, and provide enough holding power to keep the sleeves in place. I decided to just keep the sleeves that were already there and see what the engine performance is like before going further. If I decide to make new sleeves or otherwise modify the engine it is a simple process to take the cylinders back off.

Looking at the cylinders, I'm playing with the idea of machining new cylinders from brass. This would allow me to increase the bore and eliminate the sleeve. But for the moment I'm just going to loctite the sleeves and see how she runs.

 

[Guest]

Mark,
Why not just simply clean up the existing cylinder bores and make new pistons?
Dan

 

[Mark Scrivener]

Dan,

That thought did occur to me. However, the cylinders are cast (appears to be aluminum). Not sure how well they would hold up.

Mark