How to correctly install piston rings on a 1" diameter piston

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cl350rr

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I am seekin input on how others do this.

I made a round set of rings by the no heat method and after cranking them in the bore, they appear to be touching on about 70% of their diameter. they were round prior to being installed on the piston so I can only assume that my bore is not round or the method I installed them with distorted them...

please let me know what you use.

thanks
Randel
 
cl350rr said:
I am seekin input on how others do this.

I made a round set of rings by the no heat method and after cranking them in the bore, they appear to be touching on about 70% of their diameter. they were round prior to being installed on the piston so I can only assume that my bore is not round or the method I installed them with distorted them...

please let me know what you use.

thanks
Randel

I don't know if its the proper way, but here's how I did it with 3/4" rings.

I hooked the open ends of the ring over the side just past the top of the piston. With my two thumbs I spread the ring and pulled downward on it till the opposite end went over the piston. And sliped it carefully in place. For the bottom ring I did the same thing and slipped some shim stock under the ring to slide it up to the bottom groove.

I haven't broken any yet, but I still have plenty of time! :big:

-MB
 
You may have bent them during the install. Did they fit the bore when you checked the gap.

Before you install rings you should but them into the cylinder to check the end gap. If the rings were good, you spread them too much when installing. Some guys make a cone shaped install tool to minimize the amount the ring is expanded. I set the ring on top the piston. Then pull one end down into the ring groove. Once the end is in the groove you can roll the ring around the piston and it will seat into the groove.

 
I worked on making rings about half of yesterday, and they are a bit tricky to make if you want a somewhat exact fit.

These are made from gray cast iron, and were made larger than the bore, a gap was cut in them using a dremel.
I made a mandrel, compressed them on the mandrel with a hose clamp, and turned them to final bore size.

I see why people use the other method now where you make the ring to the exact bore size, and them wedge them open and heat treat them.
The method I used (start with an oversized ring, and don't use heat treatment) works well, but takes a great deal of care to get right.
From what I have read, most do not heat treat their rings correctly anyway, and overheating or underheating a ring, as well as letting it cool too fast accomplishes nothing.
The oversized rings do not have to be heat treated, and they work well.

I ruined 6 rings before I finally got the method down.

It is a trick to figure out exactly how much gap to cut out.
I finally started making the rings a tiny bit too large, and then filed the ends of the ring very slightly to get the exact gap clearance in the bore.

I had to rework the mandrel to include a ridge so that the ring would stay centered and I could cut an equal amount off all around. (I make symmetrical rings, some make rings thicker on the side away from the gap).

I use an autmotive ring spreader, and it works well to keep from overexpanding the rings. I have also used the method Steve mentions above, and it also works.

The rings I made are 1.125" dia. (final turned size).

I used a feeler gauge to check the gap with the ring in the bore.

I generally make extra rings, in case I break some, but I have not had much of a problem with breaking rings made from good quality gray cast iron.

I make the ring width to fit the parting tool size that is about the right size for the piston size I am using.

When parting off, I use the carriage dial, and part off a tiny bit larger than the groove in the piston, then use 400 grit wet/dry to clean up the sides of the ring and remove any flash.

Rings for small pistons can be a bit delicate, but it can be done, and is not that difficult once you get the method down.



Rings-TB5-01.jpg


Rings-TB5-02.jpg
 
I've used the no heat treat, machined round type of ring in two of my hit and miss engines. The rings are narrow and a bit fragile. To get around the installation deformation or breakage issue, I made my pistons in two parts. The main body, which includes the skirt, pin bore, etc in one piece. The back and lower surface of the ring groove is machined into the main body. The separate piston top, completes the ring groove and serves as the piston crown. I hold the crown on with a small socket head capscrew inserted through the under crown of the main body. You just drop the ring on and install the crown. These are single ring groove pistons, but they seal very well and have very low drag in my fifth scale Chanticleer and my quarter scale Galloway. The Chanticleer has two rings in one groove and the Galloway has just one ring on the piston.

Regards,

Chuck
 
I like to make my rings more like conventional practice fullsize automotive engines. They seem to be able to resist distortion better upon installation. Placing the ring grooves closer to the dome of the piston also helps with installation on these style rings. I tried to keep the ring grooves in the piston to within .001 of ring width but found the ring didn't want to flex enough to go in the groove. Now I make my grooves .0015 - .002 wider than the thickness of the ring itself and the ring installs easily. Most of my rings are .035" thick or thinner with a cross section of around .060". Dave
 
I made these test rings the other day when Brian R. was looking at rings for his Kerzel, just to see if 3/4" diameter rings were feasible.

These are also gray cast iron (Speedy Metals), and I did not have much trouble at all with breakage.

I made a number of rings, and a test piece with grooves in it, and put these rings on and off three times. I only broke one out of about 6, and that was with some rough handling.

I used both a ring spreader, and by hand, and both worked well.

I have pretty much settled in on a square ring in section.
These rings do have an elastic limit, and once you pass that limit, yes they will break easily. You have to get a feel for where the elastic limit is.

Some may be making the ring too thick in the radial direction.
A thiner ring seems to have better spring.

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IMG_3265.jpg


IMG_3267.jpg
 
Thanks for all of the replies.

The rings fit the bore before they were installed on the piston with a .002 gap. once installed I worked them in the bore with some kerosene to seat them and found that both have high spots in them.

the way I installed them was to put one end into the gap and roll the ring around the crown of the piston until the other end can be slid into the gap. doesn't seem that it would stress one spot any more than the next but it clearly distorted them somehow.

I'm gonna mess with them a bit more then make another set and see if I can get closer to a good seal.

Randel
 

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