Calvinman

So what is the difference between a Dykes ring and a conventional one, besides it's location on the piston?

Hobbsy

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http://www.ebay.com/itm/O-S-MAX-45-FSR-RSR-DYKES-PISTON-RING-Reproduction-/291084124698

The Dykes type ring allows gas pressure to get inside the ring and push it outward meaning the ring has low static tension during all but the compression stroke, reducing friction. Some are at the very top as yours is and others have gas ports in the edge of the piston to allow gas pressure to expand the ring.

Hobbsy

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Some different ring configurations.

stevegauth30

Yep, i believe Tim's right. Thats an early FSR. I never met an FSR that wasnt worth fixing. Great little engines. The cylinder head is round, correct? The SX-H series heli engines looked similar except with a square head.

Calvinman

Hi Steve, nuts I just broke the ring trying to figure out if there was a pin holding the ring from rotating! I found a website "Metro Area RC flying" and they have the ring listed(.50 FSR Dykes (pin))

Has anyone dealt with these people before? I also have a 46 with a ring that I will replace while I am at it.

1QwkSport2.5r

Dykes rings allow more combustion pressure behind it than conventional rings, but they both operate on the same principle. Combustion pressure forces the ring outward against the cylinder to create a better ring seal and thus more power. Dykes ringed engines make more power than an equal engine in all other aspects except for the ring style. Also, a little more oil in the fuel aids the ring seal and helps make a bit more power as well.

Frank Bowman was the go-to for model engine piston rings though he recently ceased production. You could try to email him and see if he has any rings left for your engines; but I doubt he will have any for an FSR OS. They are highly coveted and I'm sure the rings for those got snatched up.

I know a place that has a NIB .45 FSR currently if anyone is looking for one.

Hemikiller

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According to the cross reference, the 5B carb was originally for the 50FSR-H heli engine.

http://www.osengines.com/parts/discontinued.html

No matter what, the FSR series is good stuff and worth repairing. I just rebuilt a 40 FSR to put on a new-to-me Telemaster 40.

Calvinman

Hi Hemikiller, I just ordered two new rings for both the 50 (dykes) and the 46 (in case I break one putting it on) Is there any tricks to putting on a new ring? I am thinking of machining a tapered rod to slip the ring onto and then onto the piston. After breaking the ring trying to take it off I am a little worried about it. Also do I need to cross hatch or deglaze the cylinder?

Calvi.

1QwkSport2.5r

Frank Bowman always advised scuffing the cylinder liner with 400-600grit emery paper. I trusted his instructions so I always did so. As to installing the piston ring - here's how I do it: http://youtu.be/DYuf7yrj_5I Don't mind much of the banter in the video. If the ring is pinned, make note of where the pin is and install the ring such that the ring gap is at that locating pin. Extra care is needed when installing the piston into the cylinder so that the ring isn't overlapping the locating pin or you'll break the ring. Do not spread the ring to fit it over the whole crown of the piston or you will break it. Be careful not to rotate the piston in the cylinder if the ring gap is in an open port of you can bend the ring.

Calvinman

Thanks, 1QwkSport

Hobbsy

My Feedback: (102)

Cal, I made this by splitting a .25" dowel with a fine bandsaw blade. I run my drill press at it's lowest speed and only make about two passes. It deglazes but does not remove material, if that makes sense.

Calvinman

Yes, I like your idea, I have done similar for our die grinder at work. I will do that.

Cav

Calvinman

Hemi Killer, the carb could be from a helli motor. I picked up ten motors from a gent getting out of nitro. in the lot was a OS 32 helli motor.

Calvi

Calvinman

OK, I recieved my rings from Frank Bowman and I will soon be putting the engines back together. I have never reassembled a ringed RC engine before and I was wondering if there is a trick to getting the con rod onto the crank pin. With the ABC engines I always put the liner in last so I have enough play to fit the rod to the pin. I am assuming that The piston should be put into the liner first with a ringed engine?

Calvi

Happy New year

gerryndennis

Hi Calvi,

You can do it that way on the four strokes that have a hole in the case for the piston pin. You place the con rod on the crank, start the piston into the bottom of the liner but leave the wrist pin hole exposed. Lower the liner and piston in the case until the wrist pin hole lines up, fit the pin and lower the liner the rest of the way.

Every OS two stroke I've dealt with has to go together like your 'ABC' engines though. The bottom of the liner is angled to compress the ring as it slides on to the piston. The trick is to have the ring lined up with it's pin and to have plenty of assembly oil.

Practice getting the piston into the liner outside the engine a couple of times to get the feel for how much wiggling and pushing it takes. Don't push too hard! If it won't go in it'll be because the ring isn't lined up with its pin.

Once you're happy with the feel you can assemble the engine. Line the ring up with the pin then place the con rod and piston assembly on the crank pin and set it at BDC. Lower the liner into the engine until it rests on the piston. If you poke a finger down the bore you should be able to get the piston in position and level. With a bit of luck the ring will slide into the liner. You may need to twist the liner a bit if the ring has moved but don't push too hard, better to start again than persevere if the ring isn't lined up correctly.

Once the ring has started up the bore and before it gets to the ports look through the exhaust port and be absolutely certain the exhaust port in the liner is lined up with the exhaust hole in the case. There's a chance you can get the ends of the ring caught in a port if the liner isn't oriented correctly and then you might say a naughty word when you discover that the engine won't come apart again.

That's how I do it anyway. It's a lot easier to do than write down, you won't have any trouble.

Regarding the ring. I can't stress enough that you must fit the ring the way Tim (quicksprt2.5) says to do. ie get one end started then wind the rest of the ring on ending up with the other end. If you try and spread it enough to fit over the piston in one go it will break. That may be how you broke the first one?

Dont expect to feel much compression. Dykes rings are designed to have less tension so won't seal with the pressure achieved turning the engine over by hand. You will need to run the engine in again to bed the new ring into the deglazed bore.

Good luck, you'll have a great engine.

Dave H

Calvinman

Thanks for the Reply Dave,

I will be messing with the engine tonight, getting the bearings in, sleeve deglazed and maybe the piston and sleeve put in.

Calvi

Calvinman

OK, I opened up the package for the front bearing and it has seals on both sides. I think I need to remove one? The ones I removed only have a seal on one side. If I do have to pry the seal off, how do I go about doing it?

Calvi

1QwkSport2.5r

I remove both seals from the rear bearing and only one seal from the front bearing. Use a small flat head screwdriver, small scriber, or utility knife blade to carefully lift the seal. If you go in too far, you may catch the ball retainer and possibly damage it. It usually doesn't take much to get the seals out.

Calvinman

Thanks QwkSport, I managed to pry out one of the seals, the rear bearing came with no seals so no problem there. I have the fron bearing in now and it seems to be bottomed out nicely.

Calvinman

Got some more done, the rear bearing did not go in easy on the 46, I had to use the press on it. Then the crank did not want to go in, for this I Put the case in the oven a 300 for 10 minutes, shaft dropped right in. I am heating the crank of the 50 the same way for the rear bearing.

Calvinman

Sweet! all done, I got lucky dropping the liners in on both the 46 and the 50, I can see how this could be a royal PITA if luck is not on your side. Well today luck was on my side Thanks one and all for the advice, I will have to run these babies up in a few weeks.

Calvi

gerryndennis

Nah, it's not luck, just skill. Well done.

Hopefully you pressed against the outer race when you pressed your bearings in?

I'm a bit surprised you needed to heat the bearing to get the shaft in though, normally they slide on to the shaft cold without too much trouble (not saying it can't happen though). If that's what it took, it should be fine as long as the shaft turns smoothly and easily.

I've never found a rear bearing that won't slide on to the crank shaft cold, so I do that, heat the case and drop the shaft in, followed by the front bearing. I quickly mount the prop driver and an old prop, and tighten the prop nut. Then I give the back of the crank a calibrated whack with a light hammer and a length of wooden dowel to ensure both bearings are fully seated.

By tapping on the crank I'm risking damaging the bearings but it's only a gentle tap and the case is still hot, so far I've been lucky.

I don't have a press so I have to use the heat method.

Dave H

Calvinman

Yes I did press on the outer race using the outer race from the old bearing. I too was surprised about the inner races being so tight on the shaft. Ha Ha , I forgot to give it a "calibrated" whack but I know what you mean. I tried installing the main bearing using a brass drift and a plastic handle of a screwdriver only to get some plastic in the bearing which I managed to get out after some fooling around with it. After that it was the hydrolic press for the first one(46) then the oven for the 50.

Calvi

1QwkSport2.5r

I had to use a press to put the rear bearing into a 60-4C Enya crankshaft housing. I tried the oven and a heat gun. It would not seat. Into the press it goes. Hopefully it never needs to be replaced. If it does, I'm replacing the whole front housing. That bearing isn't coming out. First time I've ever needed a press to install a bearing and hopefully the only.

blw

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The 50 SX was a good engine.