Piston Valve Rings help

[WetHeader]

Hello all,

I'm attempting to make some Piston Valve rings for a friend's Speedy, but I'm having difficulty.

I turn the cast Iron down to final dimension (5/8"), then drill and bore out to 9/16" giving a radial width of 1/16. I split the ring with a hacksaw, then use a small brass wedge (which is 10% of the OD) and place it in the gap. I then heat the ring until it is an even cherry red then allow to cool naturally. I then try to expand the ring over the valve head and each one keeps breaking in two.

I was just wondering if there is something in my method I am doing wrong as to why I keep having snapped rings!

Thanks

[suctionhose]

Maybe reduce the section from 1/16 to 1mm? Also, following a method written up by a mini IC engine builder, you can snap the ring instead of using the hacksaw resulting in a practically zero gap. I've done it several times without problems. Obtaining uniform heat for the "expand with the wedge" step is critical for circularity of the installed ring.

[uuu]

For splitting the ring, see this YouTube video, about 19 minutes in: www.youtube.com/watch?v=7L4rNagoOzo

He files a small groove, then uses pliers. I've done it like this too. You can alternatively stretch it to snap by filing the groove, then sliding it down a taper- morse taper perhaps.

Having a zero gap will mean your wedge stretches the ring a bit wider, which should help.

Wilf

[stevep]

When Tubal Cain (I think it was) described making rings, not only did he wedge the gap open, he also sandwiched it between two steel plates, so they cooled slowly after heating to cherry red. He split the rings on a taper mandrel.

[chris vine]

The Tubal Cain method wasn't just to help the heat treated rings cool evenly. It was, more importantly, to ensure that they were stress relieved evenly all the way round by holding them in the correct shape while being heated.

If you just do the "wedge and heat" method, the ring will relax at the point of highest stress first, IE opposite the gap. This will mean that when it is compressed to go into the bore it isn't round. Also, and perhaps in this case, the most amount of spring will be at this point opposite the gap, making the ring much more likely to break.

So, in essence, you need to nip the ring(s) between two washers, in the sprung open shape, and then heat treat so that the rings stay that shape while hot.

Hope this helps,
Chris.

[jo479]

I always make piston rings by turning a small billet of Cast Iron with the OD plus and the ID minus, take it out of the chuck put it in a vice and mill a 1/16" slot lengthways, return to chuck and close the jaws then finish turn ID and OD to size, part off to length, deburr carefully and fit to piston, probably not the right way but it works.

[racinjason]

I make my ring oversize on the OD and ID but correct thickness, then machine to final size after heat treating to achieve a true round ring. When I heat treat my rings I hang them over a tray with sand just to catch them, I place a bar of the required thickness for the ring gap out over the sand. When heating the ring it will get red then they will fall off the bar at just the right temp, holding the gap open and making a springy ring.
Regards Jason.

[44767]

They are breaking because your radial width is far too great. This dimension should be in the order of 1/22 of the diameter of the ring so for your 5/8" ring, the ID should be approx. 0.568"

[chris vine]

I think he was using 1/16” which isn’t so different from your suggestion.
C

[44767]

Feb 14, 2024 7:23:09 GMT chris vine said:

I think he was using 1/16” which isn’t so different from your suggestion.
C

The thickness of the ring should be 0.0285"; 0.057" is the difference in diameter.

[chris vine]

I completely misread your post!!
Sorry.
C

[WetHeader]

Hello all,

Thanks for your advice and suggestions. I ended up making the radial width to just under 1mm and also used the technique of file and pliers to create the split. Rings went on a treat and are perfect fit in the bore!

Thanks again