Model Engine Maker

Help! => Specific Engine Help => Topic started by: grizelli on January 20, 2014, 07:37:31 PM

Title: Piston ring retainers
Post by: grizelli on January 20, 2014, 07:37:31 PM
Apologies if this has been covered before. I am building my first engine, a 2 stroke single-cylinder of my own design and I need to find some way to stop the piston rings from rotating in the cylinder to prevent the ends poking into the ports and snapping off.  The only way that I have thought of so far is to fit a small peg in the ring groove and file a corresponding recess in the back of the ring - however, the rings are around 19mm diameter and only 1 mm wide so I can see this becoming a bit of a trial, with lots of broken bits of ring all over the floor.  Are there any other methods that I could try, or am I being over-cautious?

Thanks for any help.
Title: Re: Piston ring retainers
Post by: ian cable on January 20, 2014, 08:19:04 PM
hi mate just make sure your pegs are opposite side of the piston , the peg only needs to be .2 to.5 of a mm high then just carefully file a step on one side  of your gap  at the back , that way it will not weaken the ring do this before heat treating good luck ian c
Title: Re: Piston ring retainers
Post by: ian cable on January 20, 2014, 08:21:33 PM
ps I mean the back of the ring :headscratch:
Title: Re: Piston ring retainers
Post by: grizelli on January 20, 2014, 08:24:53 PM
Thanks Ian, that's what I had planned to do but I was hoping that there might be a less fiddly way.  Lazy, that's me :-)
Title: Re: Piston ring retainers
Post by: ian cable on January 20, 2014, 08:58:42 PM
the only other way I have seen is a peg flush with the o/d of the piston and a shorter ring ,but it has to be a very good fit , ian
Title: Re: Piston ring retainers
Post by: grizelli on January 21, 2014, 06:15:13 PM
Well, I did one of the pistons today, and apart from the poor combination of bad eyesight, fat fingers and 1mm diameter pins, it seemed to work.  I ended up pressing the pins in and then carefully trimmed them to length with a cutting disc in a Dremel.  I guess I'll find out if it works if/when the engine starts and has been running for a while....

Thanks again for your help