Making piston rings.

.

I need to make 4 piston rings for use in 1" bores. (I will make more while set up to do so)

But I have never done this before. So what are the members techniques for the heating and cooling process please. Also what size spreader in the gap to splay out the split ring before heating.?

Cheers, Nick

witout wanting to sound rude, do a search, its been discussed in finr detail many times

.

To be blunt, fizzy ... that sounds rude.

MichaelG.

.

It's OK Michael. ............ We are used to fizzy being constantly negative about most things.

TBH I suppose that if I had looked there would even a tutorial on youtube. I could even have asked Jason and received a no nonsense, straightforward and knowledgeable reply.

But what I was trying to do was promote a forum topic of interest on this normally quite flat and quiet forum that not only I would benefit from.

Nick

I used an electric furnace; heat up to temperature, soak for 30 minutes and then let the furnace cool overnight. I can't remember exactly what size spreader, but on the order of 1/4" for 1-3/4" piston rings. The spreader size isn't critical.

Andrew

Search for an essay on piston rings on your choice of search engine and you should stumble upon a usefull article by walshaw.

I don't blame fizzy as some subjects re occur with regular monotony , which lathe to buy is a classic example .

I too would like to see some input by the more experienced engine builders in regards to the process of making rings more easily and with a higher success rate for beginners .

Yes sure i could go and dig through my library and find what i need to know but that doesn't help anyone else as they may not have access to the same books as i do .

Ian.

On the rings I have made, the 1.5" ones for a ST #9 I put a 1/4" gap piece in, heated to red with the gas torch, and held it there for about 5 minutes, then cooled it slowly by backing off the torch over a minute or two, then left them to cool on the hot brick. Did similar for a 2" bore IC motor, and a 3 1/2" bore fullsize industrial Continental engine. The cast iron for the first two was obtained from an old brake disc, the last one from the rim of an old V pulley.

Ian S C

.

Thanks for the replies guy's

Nick

Ok, here's an outline of how I made my piston rings for a hit 'n' miss engine. I started with an offcut of the cast iron bar used to make the liner. The OD was rough turned and then ground to a snug fit in the liner on the cylindrical grinder. Back to the lathe to bore out the inside to a little larger than the OD of the grooves in the piston. I then parted off rings as required a few thou thicker than the piston grooves. The process of 'snapping' rings or using side cutters has never worked for me. So I split the rings using a Junior hacksaw.

Heat treatment was in an electric furnace, around 800ºC I think. The rings were lightly clamped between two steel plates with a spacer holding the gap open. After heating, and a stabilising soak, I let the furnace cool naturally with the door closed. After cooling and a quick wipe with wire wool the rings were reduced to a snug fit in the piston grooves using wet and dry.

Andrew

Here is what I do.

Make the liner first so you can use that to gauge the OD of the rings.

Chuck a bit of suitably sized CI bar in the lathe, face off and then turn sufficient length for the 4 rings, a couple of spares and the parting cuts until it just slips into the liner. Open up the hole with various size drills followed by a boring bar until you get the desired wall thickness.

Zero a thin parting tool against the end of the work, feed along the lathe to get the required width of ring and part off. Repeat by feeding along the ring width plus the parting tool width until you have enough rings. It helps to put a bit of wire or one of those angled scribers in the tailstock chuck to catch the rings as they drop off.

I find that a pair of end cutters will split the rings OK, even quite thick/wide ones. Use the cutters on the two edges hot the inside & outside faces. The black lines are where the ring has fractured not cuts.

Next spread the rings apart, some methods describe fancy jigs but I just pop a bit of scrap flat bar between the ends, about 4mm thickness per 1" dia seems to work OK for me. Not having an oven I just lay the spread rings on the hearth and heat with a blowtorch. Keep the heat even otherwise you will get egg shaped rings if one small area get hot first. I heat to red heat and hold it there for 3-4 mins then allow to cool slowly. The packer will now be loose as the ring will have taken the "set".

Lay a bit of wet and dry on a flat surface and rub the edges of the rings on that to clean them up and remove any burrs and scale from heating. To gap the rings hold them on the edge of the bench with the gap hanging over the edge then pinch the two ends together onto a needle file which can be worked up and down. To test the fit put the ring into the bore and use the piston to push it in so it is not angled in the bore, test the gap with feeler gauges, I go for about 0.002 per 1" bore.

Finally fit the rings to the piston and off you go. Ring grooves about 0.005" deeper than the ring thickness and 0.001" wider than ring width. This pic will also answer your other question

If all else fails revert to O rings like on the drawing

Edited By JasonB on 17/04/2016 14:02:49

Jason,

How does that ring across the gudgeon pin seal the gasses?

Mike

I think the other two take care of that and the third is to scrape a bit of oil off the cylinder wall to lub the pin. There is a drip feed oiler into the open end of the cylinder. The full size had it so the model has the same 3 rings.

Edited By JasonB on 17/04/2016 16:15:31

Understood, If the full size engine does it that way, then you have to do the same.

Mike

.

Thanks Andrew and Jason, very informative.

Nick

Buy them from Stuart models much simpler

.

Simpler yes. ............. But have you seen the price of them.? I think from memory by the time you have added VAT they are around £75 for the 4 plus delivery.

Nick

Home made ones also allow you to be a bit flexible on the diameter of your cylinder as you can make them to suit if it is a bit under or over nominal

Hi Andrew, thanks for your reply , all good information there for the beginner especially using a saw to split the rings .

I must admit i have never considered grinding the OD ! Do you think there is a benifit in doing this?

Hi Jason ,

Wow ! Thanks for taking the time to post such a comprehensive answer! There are two bits of information in there that i think most beginners are looking for :

The size of the spacer to spread the rings for heat treatment and the ring groove clearances .

Most articles tell you to insert a suitable spacer in the ring gap and heat etc but never explain what suitable is !

It would be nice if on the home page there was a link to a page/pages for info like that ,probably never happen though as anything submitted would have to be proof read before adding to the library - but one can only hope .

Ian

.

I agree with all you have said Ian.

Perhaps Neil could over a period of time gather such from the likes of Jason and Andrew (there are of course others) and look to produce a one off 'Engine makers special' magazine for Model engineering workshop. I would for one pay a premium for such.!

Could include things like :-

Piston rings,
Valve making,
Making split bearings,
Boring & honing a cylinder,
Built up crankshaft construction,
Making an eccentric,
Machining a flywheel true,
Keyways,
Close fits and clearance tolerances.

Plus many more others can think of. - I realise that what may be right for one engine may not be correct for another design. But a general overview in a publication would be excellent.

There of course is a lot of cross over of the above that would be useful for both steam and IC engines. I know such publications already exist but most of them were scribed decades ago and as such do not take into account tooling and machines that are now affordable and common in a home workshop that hobby machinists could at one time only have dreamed of.

Nick

Edited By Nick_G on 18/04/2016 10:24:44