Author Topic: fitting small piston rings  (Read 7602 times)

Offline PJW

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Re: fitting small piston rings
« Reply #15 on: April 04, 2014, 09:26:12 AM »
Hi I might try to make some rings, is meehanite ( cast iron ) suitable?? as I have a bit of this :-\
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Offline Jo

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Re: fitting small piston rings
« Reply #16 on: April 04, 2014, 09:49:27 AM »
Meehanite ? That's a bit technical for me.. I buy the round sticks of CI from the usual suppliers, which I suspect is centrifugally cast Iron = no holes.

I was thinking of trying some of my heat treated (in the bonfire  :naughty:) sash weights. The only problem with sash weights is they can be full of holes but they came to me at the right price so nothing to lose  ;).

Jo
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Online Stuart

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Re: fitting small piston rings
« Reply #17 on: April 04, 2014, 11:24:26 AM »
if you are buying cast  iron bar you are 90% sure its mehanite you can tell it cuts like butter and to confirm it makes wonderful rings

I just make them the same size of the bore on the OD the other measurement to suit the piston , snap them make up two washers to clamp the in a stack , wedge the rings open a couple of MM and cover the whole shebang with soap ( bar soap the boss uses green works ok ) get em red hot and keep them at that for ten mins and allow to cool on there own ,not in a draft

rum the faces up with a bit on emery paper on a face surface and your done

the soap just keeps the scale off when heating

other will have different method but thats how I do it , after heat treat the ring are remarkably springy

Stuart
My aim is for a accurate part with a good finish

Offline Ian S C

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Re: fitting small piston rings
« Reply #18 on: April 04, 2014, 12:01:11 PM »
      I'v got some cast iron that I think is Meehanite, it doesn't turn like ordinary cast iron, more like steel, I made some rings for an IC engine, they seem OK so far.
      For the Stuart Turner S9, I used the cast iron from a brake disc,  it turned well, very fine grained.
       I have not used sash weights for piston rings yet,  but I have used them for making pistons for hot air engines, I try to make the skirt of the pistons as thin as I can, I can usually get it down to 1 mm thick, although about 25% fail before they are out of the lathe, none have failed in use.  The only problem I'v had was with a weight that I dropped on the floor, and broke, the fracture was white crystalline. On trying it in the lathe, a carbide tool just bounced of it.      Ian S C

Offline Mosey

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Re: fitting small piston rings
« Reply #19 on: April 04, 2014, 01:19:11 PM »
Meehanite is a brand name (trademark) for a large company producing all kinds of high quality cast iron. It is generally the good stuff. Have at it.
You could turn it into razor thin sections easily, and it is a pleasure to work with.
Mosey

Offline PJW

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Re: fitting small piston rings
« Reply #20 on: April 04, 2014, 03:35:03 PM »
Thanks for the info, I made my cylinder & flywheel out of this & it was nice to work with. I have a nice piece left to have a go with 7 using the feedback I have had I am almost confident in tackling the job :headscratch:
Watch this space :Lol:
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Offline PJW

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Re: fitting small piston rings
« Reply #21 on: April 06, 2014, 09:13:01 AM »
I broke one of the piston rings I purchased trying to remove it, I had nothing to loose so I had a go at making a replacement, I followed all the advice I had received including the heat treatment and ended with a perfect piston ring. All the advice was spot on and my thanks for all the help. I have added a picture of the ring & in situ, its the bottom ring. the last pic shows the build so far!
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Offline Jo

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Re: fitting small piston rings
« Reply #22 on: April 06, 2014, 09:31:43 AM »
 8)

How difficult did you find making it?

Jo
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Offline PJW

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Re: fitting small piston rings
« Reply #23 on: April 06, 2014, 09:54:22 AM »
Morning Jo, I bored out the hole to the desired size, then turned the O/D to the same size as the bore, then just parted to off to width unfortunatly I only had enough material to make one or I would have made  one or two spares! I then snapped it as told ( my heart was in my mouth as I did this) but it was so easy. the next step was the heat treatment, I used an old broken 2mm drill to open up the gap, then clamped it between two penny washers after using soap, then heated it up red for 10 mins and let it cool slowly. a bit of a clean up & job done, what was I worried about. There is a lot of knowledge on this forum & people kind enough to share it,
thanks!
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Offline Doc

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Re: fitting small piston rings
« Reply #24 on: April 06, 2014, 03:09:07 PM »
 The cast iron you speak of should be nodular iron or ductile. The differences are that there are two basic types and granular shapes are different the ductile the molecules are spherical and the what is called gray iron they are like flakes. Nodular iron actually has a tensile strength rating while gray is usually not rated.


Hi I might try to make some rings, is meehanite ( cast iron ) suitable?? as I have a bit of this :-\
Jo I actually tried this with no luck the ones I had were obviously gray iron. They had little to no tensile strength and snapped very easy and was unsuccessful in getting them on a piston. 

Offline Graham Meek

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Re: fitting small piston rings
« Reply #25 on: April 06, 2014, 03:41:29 PM »
As regards heat treating the rings I just use a wedge shaped piece of steel held vertically in my bench vice, (vise), the piston ring is then placed on the wedge such that the gap is the desired dimension and the ring is horizontal. I then start heating the ring with a small hand held Butane torch at one end adjacent the wedge. As the ring gets cherry red I make my way around the ring until I reach the other end, by which time the ring has fallen due to gravity and is now touching the side of the wedge.

The fact that the ring has fallen also indicates that it has taken on a permanent set. The small flame can be easily controlled and I get very little scale which is easily removed in a citric acid pickle for a few minutes, plus you do not use so much gas.

My best regards
Gray,

Offline Brian Rupnow

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Re: fitting small piston rings
« Reply #26 on: April 06, 2014, 04:29:30 PM »
PJW--It appears in your picture that the gas tank is situated higher than the centerline of the carburetor. If so, it isn't going to work properly. There is no float and needle mechanism in that carb to stop the flow of gasoline, so you will experience constant flooding of the engine, and possibly a fire. The top of the gas tank should be 1/2" to 3/4" below the centerline of the carburetor. There is enough vacuum created by the venturi effect in the carb to pull the gasoline up from the tank.---Brian

Offline PJW

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Re: fitting small piston rings
« Reply #27 on: April 06, 2014, 04:39:12 PM »
Thanks for that Brian, the tank is not fitted yet so it will be no problem dropping it, I looked at it this way with no fuel pump it would be gravity fed & the flow would be sorted with the fuel needle. I will shorted the legs to the suggested height,

Peter
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Offline PJW

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Re: fitting small piston rings
« Reply #28 on: May 10, 2014, 06:57:43 PM »
I ran my finished engine with the piston rings I made it ran well, & as an experiment I made another piston & used an O ring as suggested by Chuck, the one with the O ring had the better compression & even ran better!
Nice one Chuck :ThumbsUp:
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