I have been asked for information on my 3 ring piston seal. The reason for developing this was due to my displacer piston seal running about half way up the regenerator at TDC which was accepted, in order to keep the engine compact. The temperature at this part of the cylinder is probably quite high so the sealing ring needed have lots of compliance or it will leak when cold or bind when hot. Preloading a twin split ring with an O ring was not an option due lack of compliance so I added a third ring, thin in section and a close fit in the width of the groove with a leaf spring behind to hold the ring against the cylinder wall. The rings are gapped such as they virtually close at maximum temperarure yet the third ring maintains a good seal when the engine is cold. I have posted two pictures of the seal in the gallery under bits and pieces.
Geoff V
3 Ring Piston Seal
Re: 3 Ring Piston Seal
Is this piston seal system used on GV-3c, you discribe the hot side, is the cold piston similar in its sealing.
My ALPHA/ Ross Yoke motor gets by without extra sealing, the Heylandt Crown is fairly high (couldn't find any info on correct propportions), so the working area is relitively cool, and although the motor is fitted with water jackets, I do not us the cooling system, and it will run all day without over heating. I tend to shy away from ring seals, trying to use a good fit of cast iron piston and bore, I make the motor a little on the tight side, so that it will just run, then work it until it frees up, they seem to get to the correct freedom, and no more wear seems to occur. My longest running motor (2000 hrs to first overhaul, proberbly 100 hrs since then), has 1 3/4" bore made of bored out galv water pipe, and a piston made from a cast iron window weight shows no wear in the bore or on the piston, just polished. Ian S C
My ALPHA/ Ross Yoke motor gets by without extra sealing, the Heylandt Crown is fairly high (couldn't find any info on correct propportions), so the working area is relitively cool, and although the motor is fitted with water jackets, I do not us the cooling system, and it will run all day without over heating. I tend to shy away from ring seals, trying to use a good fit of cast iron piston and bore, I make the motor a little on the tight side, so that it will just run, then work it until it frees up, they seem to get to the correct freedom, and no more wear seems to occur. My longest running motor (2000 hrs to first overhaul, proberbly 100 hrs since then), has 1 3/4" bore made of bored out galv water pipe, and a piston made from a cast iron window weight shows no wear in the bore or on the piston, just polished. Ian S C
Re: 3 Ring Piston Seal
Ian
2000 hours before overhaul, that is quite extraordinary, let me see that's an hour every other day for nearly 11 years or just over 83 days non stop amazing!
Geoff V
2000 hours before overhaul, that is quite extraordinary, let me see that's an hour every other day for nearly 11 years or just over 83 days non stop amazing!
Geoff V
Re: 3 Ring Piston Seal
I used to run the thing 4 to 5 hrs,5 or 6 days a week, the crankshaft, and big ends got very warn, but the motor still have enough power to opperate my little power hacksaw, this was used to cut the metal for the new parts. The motor is based on James G. Rizzo's Dyna from his book "The Stirling Engine Manual", It was my 2nd motor, so I thought it a good idea to flog the thing to death, it's not dead yet by far, it has similar power to the much smaller (35 x 20 mm/ cyl) Ross yoke motor.
I'm listening on the sideline when you start on some of the more technical stuff I'm afraid, I just use fairly basic stuff, but thats OK, but I may pick up a bit with any luck.
One other thing that stopped the trials, was the price of LPG, but I suppose I saved some electricity, because I used the generator on the motor to run my workshop radio. Ian S C
I'm listening on the sideline when you start on some of the more technical stuff I'm afraid, I just use fairly basic stuff, but thats OK, but I may pick up a bit with any luck.
One other thing that stopped the trials, was the price of LPG, but I suppose I saved some electricity, because I used the generator on the motor to run my workshop radio. Ian S C
Re: 3 Ring Piston Seal
your three ring system looks interesting. it will definitly give a lot of ring movement/ conformity so should stop any thermal expansion problems.
do you put the two open ends of the piston rings 180 degress apart and what stops the rings from rotating in there grooves and hence lining up the two cut ends?
using the spring steel to energise the rings is a good idea as it gets around the problem of creep in the rulon. I normally use silicon oring's to energise my rings, but i might try your technique in a future incarnation.
I see you have quite a wide bearer ring with diagonal slots cut into it. is this bonded on to the piston? and if so, what adhesive have you used,as bonding rulon is tricky without pre etching.
do you put the two open ends of the piston rings 180 degress apart and what stops the rings from rotating in there grooves and hence lining up the two cut ends?
using the spring steel to energise the rings is a good idea as it gets around the problem of creep in the rulon. I normally use silicon oring's to energise my rings, but i might try your technique in a future incarnation.
I see you have quite a wide bearer ring with diagonal slots cut into it. is this bonded on to the piston? and if so, what adhesive have you used,as bonding rulon is tricky without pre etching.
Re: 3 Ring Piston Seal
Hello Ratty
The gaps are assembled 180deg apart and todate they have not rotated in the bore, probably wouldn't matter as the third ring seals the gap. The bearer ring is split on the diagonal and just a snug fit in the groove, I had to do it this way as it covers the gudgeon pin on the compression cylinder.
The gaps, as you rightly summise, are not critical, but for piece of mind I heat the assembly with a hot air paint stripper and try to get them to just close a bit over normal operating temperature.
In areas where there is a large temperature change they seem to work well.
Geoff V
The gaps are assembled 180deg apart and todate they have not rotated in the bore, probably wouldn't matter as the third ring seals the gap. The bearer ring is split on the diagonal and just a snug fit in the groove, I had to do it this way as it covers the gudgeon pin on the compression cylinder.
The gaps, as you rightly summise, are not critical, but for piece of mind I heat the assembly with a hot air paint stripper and try to get them to just close a bit over normal operating temperature.
In areas where there is a large temperature change they seem to work well.
Geoff V