Author Topic: Graphited packing for a piston ring  (Read 447 times)

Offline JR72

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Graphited packing for a piston ring
« on: October 31, 2019, 05:27:28 PM »
I want to use graphited packing as a piston ring, the piston is 1 inch dia. ( similar to the Victoria ) the plans show a groove of 3/32" deep by 1/8" wide. It seems the most popular size of the packing is 1/16". Would this mean the packing is wound round two or three times given that it would compress? Would it be better to form a smaller grove? I would prefer to use graphited packing and not piston rings as I doubt if I will run the engine very much but would like to keep the cylinder bore lubricated.

Your help will be much appreciated.
Thanks

John
(JR72)

Online Jo

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Re: Graphited packing for a piston ring
« Reply #1 on: October 31, 2019, 05:38:19 PM »
Make the groove the size on the plans (you can then fit piston rings in the future if you choose) and wind the yarn round the piston a good few times.

I normally separate out the strands in the yarn to make it thinner: you get more rotations and it is easier to adjust the amount of packing for a good fit  ;)

Jo
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Offline JR72

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Re: Graphited packing for a piston ring
« Reply #2 on: October 31, 2019, 06:00:34 PM »
Many thanks Jo for your quick reply. Your advise seems good to me I will certainly give it a try thank you.

John

Offline Jasonb

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Re: Graphited packing for a piston ring
« Reply #3 on: October 31, 2019, 06:34:32 PM »
Bit of 1/8" dia with an angled cut to the ends would pack down perfectly into that size groove as cross section of groove is just a fraction less than cross section of 1/8" dia.

Offline JR72

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Re: Graphited packing for a piston ring
« Reply #4 on: October 31, 2019, 06:41:48 PM »
Many thanks Jason, I now have two options using the same size groove so I will see how I get on.

It`s replies like this that makes this Forum a great place to be.

Thanks again

John

Offline derekwarner

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Re: Graphited packing for a piston ring
« Reply #5 on: November 01, 2019, 02:07:30 AM »
John....

Remember the graphited yarn in this application will be a pressure energized ring....so yes by all means, machine the piston 'ring' groove as per Drawing dimensions and then as suggested unravel the yarn to add additional windings whilst still maintaining a vertical float for the yarn

The impregnated graphite provides excellent lubricity between the piston OD & the cylinder bore, and eliminates any potential for the natural twine/cotton/yarn to stick or burn at our modest steam pressure/temperatures and whilst at all times providing a ZERO steam bypass in your engine  :ThumbsUp:

People tend to dismiss 100 year old   :happyreader: technology just to use the latest & greatest ...[sometimes we must ask at what cost?]

[As a 1st year Apprentice  :old: 55+ years ago, I remember my Saturday overtime shift unravelling graphited yarn from those large Silver Boxes of J Walker Gaphited Packings, then repacking the gland seal of a 48" diameter [very scored] vertical piston rod in an oil/water extrusion press imported from the UK in 1948?......the actual gland seal was ten [10] split cut bands of 1" square  JW Grade 600...[the 600 was a steam temperature rating in degrees F} and nothing to do with the oil/water fluid at 500 PSI working pressure @ ambient temperature]

So as that Apprentice, I asked my Tradesman why I could not make one semi continious ring of x 10 high  instead of the 10 x individual staggered rings?......:facepalm::hammerbash:... I then learnt a little of what amounts to fluid sealing characteristics as lectured by a Mr Daniel Bernouli ...which is part of the basis of thermo dynamics  and still valid today some 300 years later

Derek
« Last Edit: November 01, 2019, 05:31:34 AM by derekwarner »
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Offline JR72

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Re: Graphited packing for a piston ring
« Reply #6 on: November 01, 2019, 07:44:19 AM »
Thank you Derek,
I am so pleased with the response I have received from yourself, Jo and Jason. Really good to know that I have made the right choice especially with a long tried and tested method. I have already ordered the graphited packing and look forward to having a go.

Tanks again to all of you.

John

Offline steam guy willy

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Re: Graphited packing for a piston ring
« Reply #7 on: November 01, 2019, 03:15:19 PM »
Hi John, I make my own graphite yarn by running thin cotton string over the carpenters pencil lead.... works for me ok impregnated with thin oil .

Willy

Offline JR72

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Re: Graphited packing for a piston ring
« Reply #8 on: November 02, 2019, 07:48:20 AM »
Hi Willy,
Many thanks for the tip, I might try that but as I have order he graphite string (only 2.50 inc. p&p ) I can try both. But that is a handy tip for the future.
Thanks again

John