Model Engine Maker

Help! => Specific Engine Help => Topic started by: Mcgyver on November 04, 2018, 02:08:34 PM

Title: Tricks to installing pistons with rings
Post by: Mcgyver on November 04, 2018, 02:08:34 PM
Yesterday I'm trying to assemble my Stuart Triple, and wasted a bunch of time trying to get a piston in a bore.  The trouble of course is the rings.  I've done this many times with bigger pistons using binding wire but just could not get it with this - small bore, 3/4", three rings and the bore is situated in the middle of a bigger casting so its difficult to twist binding wire up to it.  I tried gear clamps, wrapping steel strapping, nothing but frustration

Has anyone made a miniature piston ring compressor, or have any winning ideas for this frustrating task?

thanks
Title: Re: Tricks to installing pistons with rings
Post by: Florian Eberhard on November 04, 2018, 02:37:28 PM
Hey McGyver

What about a funnel? That is what works for teflon piston rings and I guess it could also work for normal piston rings.
And it is easy to make. The only critical part is that the small diameter should be exactly like the cylinder bore. (or even slightly - like 0.02 to 0.05mm less if the piston is small enough for that)

Florian
Title: Re: Tricks to installing pistons with rings
Post by: Bluechip on November 04, 2018, 02:39:22 PM
Did use a nylon Ty-Wrap on a titchy compressor piston once. Just used it to put the ring hard into the groove then shove the piston in. The wrap just slides off 'cos it's slippery. Then cut it off.

Might work for you. Might not. Cheap enough to try.

Dave
Title: Re: Tricks to installing pistons with rings
Post by: kvom on November 04, 2018, 02:45:16 PM
Florian's idea is exactly how Kozo shows for inserting pistons in his locos.  Basically a piece of round stock with a hole the same diameter as the bore or slightly smaller.  Then carefully cut a shallow taper into the hole walls.
Title: Re: Tricks to installing pistons with rings
Post by: Stuart on November 04, 2018, 03:30:27 PM
Yes make up a funnel only needs to be short

The most fun I had getting ci piston rings in was on the last loco I built the end of the cylinder had a recessed part into which the steam port emerged pretty big one to boot , had to make up a funnel with a thin extension to fit in the cylinder  and let the piston pass though

Loco now sold but I hope they do not pull the piston out without the tool else that ring will enter the steam port and cause much knashing of teeth 🦷

Title: Re: Tricks to installing pistons with rings
Post by: Mcgyver on November 04, 2018, 03:44:50 PM
great idea - thank guys!  Simple little funnel would have avoided all that frustration.  D'oh!