v-ring crankshaft seals

[vile_fly]

I am eyeballing these v-ring seals for my v-twin stirling engine so I can pressurize it. The crankcase must have a thrust surface to seal against these, so I will come up with something. They are made of teflon, but are only available in english sizes. Has anyone seen metric versions of these seals or used them for that matter? 35mm is the shaft size I am working with. 1 3/8" is as close as it gets in english.
They look rather promising, since I intend to pressurize up to 150 psi. The "V" side is opened against the pressure side so that the pressure forces a tighter seal. What is more interesting, they can be stacked thick enough to deal with just about any magnitude pressure one can reasonably deal with.
I know everyone will complain about the friction it might impart......but I will pay any price to pressurize my stiring engine without having to come up with a new crankcase or enclosure. This is doing it the hard way, but I am trying to keep the project costs down. A complete V-ring seal requires at least one V-ring, one male adapter, and one female adapter. The female adapter provides an extra sealing edge. V-rings are sold in packages of 10; adapters are sold in packages of two males and two females.
These are from mcmaster-carr. http://www.mcmaster.com/#rotary-seals/=gazo1j

[Ian S C]

those rings look interesting, what are they made of? maybe something like PTFE/teflon? Must see if they are available here. Ian S C

[vile_fly]

Yep, these are teflon/PTFE seals.
I found nitrile seals in my english size at another site.
http://www.sealsales.com/packing/vpacking10.shtml
I would rather find them in teflon, but the nitrile can seal against thousands of psi.
use 3 to seal from 0 to 500 psi. Just stack more if you have a sealing problem.
This is their diagram......


Another name for them is Vee packings or chevron seals or parachute packings . Parachute is the last thing I would call them, but I didn't invent them.

These guys sell v-seals....but you will have to request a quote. http://www.jameswalker.biz/product_rang ... land-seals
They have a NZ location.

This is how they should be installed according to the manufacturers.

[Ian S C]

The thing I would perhaps find a difficulty with is shaft diameter, round about 3/8" / 10 mm. It gives me an idea though, I could make a die to make my own, in the same fashon as I made dies for making rubber fittings for vintage vehicles. The factory that used the dies is still cordoned off because of the earthquake a year ago, so I don't know if they survived, there's a few thousand bucks worth of gear there, never mind thats OT.
I could mould them the same way as I make carbon impregnated teflon bushes for displacer glands, maybe worth a try. Ian S C

[vile_fly]

Stretch-fit Rotary Seals



You can stretch these to fit over a shaft, while the flexible hinged lip still presses firmly against the shaft's face to deflect dust, dirt, and water. Seals also self-adjust, stretching to maintain fit when the shaft begins turning. They prevent the loss of lubricants such as grease and are made of carboxylated Buna-N for better abrasion resistance. Use on motors, pumps, and bearings in water, water-glycol, and water-soluble oil service. Seals resist weather, UV rays, ozone, water, compression set, grease, oil, detergents, salt water, hydraulic fluids, alcohol, and some refrigerants. Durometer hardness is A85. Temperature range is –20° to +225° F. Maximum pressure is 6 psi in the opening direction and 100 psi in the closing direction.
"Stretch-Fit Rotary-Shaft Ring Seal 3/8" Shaft Diameter, 0.37" to 0.45" Shaft Diameter"

This type of seal might be more of a better fit for your application, Ian. Too bad it can only handle 100psi. Still requires a smooth thrust surface to press against. I do wonder how well they might work against gas pressure, though. I never used these, either....so this is theoretical for me. But something is better than nothing, I say.
Mcmaster sells these as well. http://www.mcmaster.com/#rotary-seals/=gbgzgt

Making seals from scratch is quite the skill to have for stirling engine building. You just might have to post an article on how to do it so that the technique is not lost forever. :D

[Ian S C]

There are a few photos on my album on www.model-engineer.co.uk
That last seal would be easier to make a die for, might try after I finish the job I'm on. I'm building an open crank IC motor, and at the moment I'm making piston rings. I think the motor will work, but it's taking a bit of fiddling around but theres hope, its 2" boreX 3 1/2" stroke. Ian S C

[vile_fly]

Just make sure you don't try building a baby Deltic engine. You'll go crazy with 6 sets of 3 cylinders with 2 pistons per cylinder, no cylinder heads and 3 crankshafts (2 CW rotation, 1 CCW rotation)

[Ian S C]

Don't worry I know about Deltics, and Junkers 2 crankshafts, and 2 pistons per cylinder, compression ignition aero engines used by Germany during WW2. Mine has 1 cylinder, and at times I think thats 1 too many, perhaps I should convert it to a Stirling Engine, at least the timing is easier with a Stirling Engine.
While picking some RTV type gasket of a cylinder head, I thought to myself, perhaps there is a RTV suitable to mold as a seal, easier if it can be done cold, although the heating is no real problem. Ian S C