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Engine basics => Engine set up tips => Topic started by: frank mccune on October 19, 2018, 01:05:10 PM
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Hi All:
Can you tell me an easy to do this. I did it today for the first time and had a thrill a minute. There must be an easy and quick way to do this. Share please.
Tia,
Frank McCune
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Hi All:
Can you tell me an easy to do this. I did it today for the first time and had a thrill a minute. There must be an easy and quick way to do this. Share please.
Tia,
Frank McCune
You did it in what motor, ? different engines take different ways to install them, some you can put the piston/ring in the sleeve before inserting, others you cannot
Randy
Randy
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Hi Randy:
Thanks for the prompt reply. It was an OS SF .46 engine.
I finally marked the top of the piston with a felt tipped pen and attempted to align the pin with the ring gap. I used a dental pick to lightly check to determine if the ring gap was seated on the pin. I assumed that if the ring did not rotate when in the sleeve, all was well. The piston/ring appeared to move in the sleeve sans any difficulty. I hope that this is an accurate indication that the parts are assembled correctly.
Be well,
Frank
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That motor is pinned on the intake side of the motor, and towards the back, between the rear main intake port and the boost port, make sure the piston is pointing that way where the pin is, they came with an arrow on top of the piston pointing the way, but you can just scribe another one in if you cannot read it
The rings are cut on the back side at the gap to clear the pin so the gap goes at the pin. Some engines like the ST 51 have the rings cut about an 1/8 in away from the gap to clear the pin, so double check your motor BEFORE you install the parts .,
IF you buy a ring from a aftermarket ring maker, and he machines the pin clearance in the WRONG place, and tells you to twist the sleeve to match, just look for a new ring that is stock
Be aware some engines the ring has top be install top to bottom correctly, there is a top and bottom to some rings
Many of ringed pinned engines have a bevel cut on the bottom of the sleeve to compress the ring as you slide the sleeve over the top of the piston and into the case, this is doen ALWAYS at top dead center, and you make have to twist and wiggle the sleeve a very SMALL amount to get the ring to compress. CAUTION many people ding or break the ring installing them as they are too aggressive with the technique to install them
Check the ring by just squaring them up in the sleeve and using a feeler gauge,,, DO NOT use a dental pick
Regards
Randy
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The ones that do not have the taper in the bottom of the sleeve, only take twelve finger nails to compress the ring. LOL. The ones with the taper are gently worked in with every thing at your disposal that is not hard. A nylon electronic tuning tool works well to gently push the ring on the side it is not in yet. Working around the ring you can get them in without forcing them.
Somebody should make a small ring compressor for model engines.
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Hi Jim & Randy:
Thanks for the replies.
I used the dental pick to check to see if the ring gap was in the correct position. This was done by removing the head and with the piston at TDC and applying a very small radial force to the ring gap to determine if the ring was correctly on the pin. I doubt that any damage happened to the ring.
In the past, I used a worm screw type of hose clamp for a piston ring compressor. Try it and it may work for you.
All the best,
Frank McCune
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Hose clamp is a great idea Frank. Modelers make things that work out of necessity. That is what makes this hobby so great.
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ST G.51 was the only one I've done. The cylinder was a heat-shrink fit into the case, which I doubt would be a problem on the OS. It was a lot of sweating bullets and application of the heat gun, but came out just fine. If the piston and ring go into the cylinder, the ring gap has to engage the pin, or it won't go. My two G.51's will soon be fitted with ABC setups...YAY! That's the way ST should have made them to start with. y1 Steve
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ST G.51 was the only one I've done. The cylinder was a heat-shrink fit into the case, which I doubt would be a problem on the OS. It was a lot of sweating bullets and application of the heat gun, but came out just fine. If the piston and ring go into the cylinder, the ring gap has to engage the pin, or it won't go. My two G.51's will soon be fitted with ABC setups...YAY! That's the way ST should have made them to start with. y1 Steve
Hi Steve
I have done over 200 ST G51s everyone has had to have the pin engage the ring offset from the ring end gap, NOT at the ring gap, if you put the ring gap at the Pin it will interfere into the port, the ring is machined about 1/8 inch away from the gap to clear the pin, So I guess you may have had an after market ring
Look close at the ring, look near the gap on the left side, the back side of the ring is machined there to clear the pin, and hold the ring AWAY from the port , so the gap does not catch in the port
Regards
Randy
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I still do not see how a person could get the ring to go in if the ring notch was not on the pin. It would push it out enough so that it would not go in the sleeve. Seems like the ones I have seen the recess for the pin was at the ring gap. I just learned that is not always the case. But the only big Tigre's I have owned that were ringed, was a blue head 60, and the old single ring 46 that I have now. As I recall niether one of those were pinned.
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I still do not see how a person could get the ring to go in if the ring notch was not on the pin. It would push it out enough so that it would not go in the sleeve. Seems like the ones I have seen the recess for the pin was at the ring gap. I just learned that is not always the case. But the only big Tigre's I have owned that were ringed, was a blue head 60, and the old single ring 46 that I have now. As I recall niether one of those were pinned.
Hi Jim
You are correct the ring has to be relieved at some part of the ring to clear the pin, this is normally at the gap or just a small amount away from the gap, the older engines that were single by pass models did not need pinned, as they used much smaller ports, the newer Loop Charged ported engines have very large ports in comparison , large enough for the ports to let the ring gaps into the port, and clip off parts of the ring, so naturally you would pin the ring so the gap is running on a surface that clears all the ports
Randy
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Randy's correct, of course! It is a Tom Lay rebuilt G.51...which had a Frank Bowman ring, per his standard rebuild. So, I never saw a stock G.51 ring. The ring wasn't seating, no compression, some shiny spots on the cylinder wall, so I took it apart and gave it a decent crosshatch with a brake cylinder hone. The cylinder (new from Tower) didn't look like it had ever been honed...ever. The cylinder of this particular G.51 is a shrink fit, which I thought was odd. This feature made assembly a PITA, but I got 'er done, the ring seated, compression appeared, and it will now fire off with a digital starter. y1 Steve
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Makes sense Randy. I never thought of the ports on the newer engines being larger so the ring can catch in the port. Most of the engines I work with are old ignition engines which in comparison have very small ports. The Atwood Champion, before the Super had round port windows.
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When I was flying R/C pattern, I flew with a friend that ran YS 120 four strokes. He found that if the ring gap was in a certain place they ran better. He would go fly them until they ran best, shut the engine down and hope the ring did not move. Then he pinned the ring there. Then they always ran consistently after that. Depending on what side the gap was on was where they had the best running compression. You could tell it in the air before he pinned them at times they would just lose power for no known reason. He figured it out. Pinning the ring solved the problem. No port windows to worry about.
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A clearer pitcher ,
(https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcTZFxsP4etKIf3V4wn2axt4VA-iFrCwszHjAd62kh57-MHgsMjO)
Wonder some times , and sometimes dont wonder , Production Line 'rejects ' end in the ' spares ' consignments .
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When I was flying R/C pattern, I flew with a friend that ran YS 120 four strokes. He found that if the ring gap was in a certain place they ran better. He would go fly them until they ran best, shut the engine down and hope the ring did not move. Then he pinned the ring there. Then they always ran consistently after that. Depending on what side the gap was on was where they had the best running compression. You could tell it in the air before he pinned them at times they would just lose power for no known reason. He figured it out. Pinning the ring solved the problem. No port windows to worry about.
Same with the ST46, the end would migrate freely and it clearly made a difference in how it ran. I was to the point of figuring out how to pin the ring, when we went to the Golden State meet and found Paul Walker flying his 40VF-powered model. Then I stopped having to care about ring end gaps ever again.
Brett