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Piston Rings ... revisited


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  #1  
Old 10-21-2009, 07:12:39 PM
jopeter jopeter is offline
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Default Piston Rings ... revisited

I would like a few opinions on this . I have made new piston rings many times but they have all been small sizes ,max 3inch diam .I have been lucky enough to have a supply of hollow cast iron of various sizes. However this time I have to make a couple of 5 1/2 inch diam rings Obtaining the material to make them was not easy . I decided to use two cast iron grease trap grates . There appeared to be enough '' meat'' on them to make the required rings . Living in the country and it is burn off season I threw these grates into a fire . They stayed there for three days and cooled slowly . My thoughts were that if there were any induced stresses in the castings they would be eliminated. Unfortunately in turning the OD I found there was an ''Inclusion'' that I was just able to eliminate as I turned the OD to size.I have my doubts about quality of the material and that there may well be a weakness .

I have since obtained a cylinder liner that is perfect as far as size and material for the manufacture of these rings.My question is should I stress relieve this new material before i commence machining . I assume this cylinder liner is cenrtifugaly cast and is of good quality. My gut feeling is that is probably not necessary but any opinions would be welcome.
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Old 10-21-2009, 08:46:22 PM
Pat Barrett Pat Barrett is offline
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Default Re: Piston Rings ....re visited

I helped my son, restore a 9hp Hercules hit and miss. 5-1/2" bore. Dave Reed, here, had the rings. My old ones were 7/16" wide with worn ring grooves and we turned them out to 1/2" width, which is what Dave had in stock and boy, did it turn out good. Takes 2 people to roll it thru. Not taking away from what you are trying to do but the price was reasonable for the size and all the mystery was not there in your case.
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Old 10-21-2009, 08:50:38 PM
DaveWachter DaveWachter is offline
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Default Re: Piston Rings ....re visited

All rings are heat treated after they are made not before . When you use any kind of greating you take the chance of hard spots if you get it hot before you machine it bon fire some times will make them hard i buy my rings its cheaper than haveing no tension in your rings dave wachter thanks harry
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Old 10-22-2009, 03:25:25 AM
Merv C Merv C is offline
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Default Re: Piston Rings ....re visited

I have always bought any rings I needed. I have always found I can always get what I wanted x stock. In the case of my Lister R if I remember right Cat D8 rings fitted perfectly, From Memory there were three rings to each land, got great compression. It has been long time since have to replace rings and I know that on other occasions I have used more than one ring in the lands and it works fine. I realise there is a lot of satisfaction in making your own rings, but it is not for me.

Merv.
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Old 10-22-2009, 06:05:38 AM
jopeter jopeter is offline
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Default Re: Piston Rings ....re visited

Maybe I could have bought the rings ready made but if you have the right tools etc then there is a sense of achievment in making your own but then thats just my way.
I will go ahead and use the cylinder liner with out any stress relieving prior to machining . I use the method of machining the OD to bore size plus .004 ''. I split the ring and wedge it open and heat it in an electric kiln and let it cool overnight .This method has been fine in the past .
If the CI gratings had worked then it would have been a good use of a material that was found in the salvage yard.
I guess my practice of using what comes to hand is the result of looking after a machine shop on a remote island where the ideal materials were not always available and we had to improvise .
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Old 10-22-2009, 08:31:22 AM
Wayne Timms Wayne Timms is offline
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Default Re: Piston Rings ....re visited

Hi Jopeter,

I would look for cast iron that, when it breaks, has a fine grain (like a china plate) rather than a coarse grain (like a carrot) to use for your piston rings.

I personally would only make piston rings if I couldn't readily source them.

Regards,

Wayne

www.bluefuel-whitesmoke.com
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Old 10-22-2009, 10:05:12 AM
Ray Freeman Ray Freeman is offline
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Default Re: Piston Rings ....re visited

I think the recommended cast for rings is 3D. I have made rings out of ordinary old gray cast and they work OK too.Its a bit of satisfaction to crank over a restored engine that has heaps of compression that has your own rings in it.
Peter,whats behind your idea of adding 4 thou to the bore size? Is it for shrinkage from the heat treating?
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Old 10-23-2009, 07:06:36 AM
cobbadog cobbadog is offline
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Default Re: Piston Rings ....re visited

I think that there would be a sense of achievement if you have the resourses to make it yourself and you actually do make it and it works,,,,,what would be better. If it didn't work then source them elsewhere or work out why it didn't work. I can only imagine the machining oversize is for shrinkage after heat treatment. An old aussie saying usually sums it up quite well ..... "have a go ya mug"
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Old 11-21-2009, 06:39:21 PM
ozsteamnut ozsteamnut is offline
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Default Re: Piston Rings ....re visited

G'day all the last set i made for a hornsby i had where 6 1/2" x 1/2 from memory,i machined them out of 3 (i think) holden flywheels,i also machine to size and cut and gap them by clamping them between a pair of plates with a the correct gap,then i put them in the wood heater in the lounge room get em a dull red and leave them to cool in there,sounds a bit agricultural but it works.
Regards Phillip
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Old 11-22-2009, 12:39:02 AM
WilliamInOz WilliamInOz is offline
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Default Re: Piston Rings ... revisited

I gotta make some new rings for a 4hp austral open crank my lathe will be too small but will something else fit them?

Cheers, Will
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