# Making a Graphite Piston



## chucketn (May 13, 2013)

I'm making a replacement piston for my non-running attempt at a Poppin Fire Eater Engine. First time I've worked with graphite, and boy is that stuff soft! That brought up a question. How do I attach the piston to the piston rod? Will this material take threading? Do I need to add a nut on the head end, or sandwich it between 2 nuts and washers? What do those of you that have made graphite pistons do?

Chuck


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## portlandron (May 13, 2013)

I have built two engines that have graphite pistons. One has the piston rod and the graphite piston threaded. Then put together with Locitite 603. The other engine has a washer and nut on the top of the piston. So to answer your question yes, graphite can be threaded. Another trick in making the piston is to get it close to size then polish it with a piece of paper when it is still in the lathe to size.


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## Longboy (May 13, 2013)

This is what I do with Graphite pistons for Stirling. My pistons are either 1/2 or 5/8 inch diameter so I go to ACE Hardware and get some brass or steel eyelets, the two smallest size they have with wood screw threads. Drill undersize of their threads into the piston. You can end up going hole-thru the piston top depending on how long the piston is and just seal with a dab of superglue or epoxy then. Pry the eyelet loop open so you can get your con rod with a slightly oversized hole drilled in its piston end over the eyelet loop. The con rod then pivots easily the loop as your crank rotates.


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## lennardhme (May 13, 2013)

Innovative thinking Longboy


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## MCRIPPPer (May 15, 2013)

where do you guys buy big pieces of graphite? MCMASTER carr?


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## BronxFigs (May 15, 2013)

I was thinking about using Graphite as piston material for a Flame-Licker engine with a bore of roughly 1.125" diameter.  Never used this material.  Is it very easy to crumble and fracture?  I have a feeling that I should by extra of rod, just in case.

Any machining tips?  What's the best way to make a piston from graphite?

Frank


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## Longboy (May 18, 2013)

MCRIPPPer said:


> where do you guys buy big pieces of graphite? MCMASTER carr?


....I go to Graphitestore.com. http://www.graphitestore.com/items_list.asp/action/prod/prd_id/25/cat_id/22
I have no machining secrets for graphite round stock and there is no trick or special procedures in cutting such. I get an oversize round and cut/ polish to diameter instead of exact size for cylinder I'm using.....just afraid that it may be too loose in the cyl. otherwise and I'll have an big expensive pencil then.  Dave


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## portlandron (May 18, 2013)

Got my last piece of graphite off ebay. Price was good.


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