I'm in the market for new piston and valve rings for 58 to be installed during our winter layup. What are my options for a supplier?

Has anyone ever used this company for rings? https://www.precisionrings.com/rings

Also on the same topic, I am curious about cylinder tolerances. 58 has a 15" bore. What tolerance should there be ideally between the ID of the bore and the OD of the piston? What tolerance between the width of the rings and the width of the grooves and the space between the ends of the rings when installed. Once I pull the pistons I can determine how out of round the bores are. I am not planning to rebore the cylinders (unless the out of roundness is severe), just doing some work to the pistons and rings to reduce blowby.

Is building up worn pistons with bronze a recommended practice, as shown in this Baldwin spec?

If I'm reading the BLW sheet correctly, the groove should be .010 wider than the nominal dim of the rings.
You might try asking Strasburg about making new rings.

Adding additional bronze to cast iron parts and then machining back to tolerance is a well known repair technique. I have also done it to build up badly worn brass/bronze bearing parts.

Most brazing rods have a higher tensile strength than cast iron.

Cleanliness is essential, especially on cast iron where oil can get into the "pores". Heating the parts in an old oven to burn off the oil can work.

Also preheating is necessary so the added material will bond well to the base material.

Work in layers, braze all the way around in one layer, then chip off any flux, wire wheel and add a second layer if necessary. Use a new clean wire wheel so you don't contaminate the surface.

In the absence of any other tolerance info a "running slip fit" should be about 1 or 2 thousandths of an inch smaller per inch of diameter, so the OD of a 15" piston should be at least 0.015" smaller than the bore. Depends on straightness of the bore, roundness, etc.

For round parts some kind of slowly rotating welding positioner can help. Even having the piston rod with the piston attached on some rollers and turning it by hand will speed up your progress.

Good luck.

Building up the piston with bronze to correct wear has been a good repair for us. Currently doing this on a uniflow type piston. Since those are longer only applying bronze to each end at the ring grooves. Turning the area to be built up gives a clean consistent surface to work from. This one we honed 60 thousandths over we were able to get the cylinder to the shop and in the power honing machine. We have honed cylinders that size in place by hand about 20 thousandths. It is time consuming and not a lot of fun but can be done. If it needs more than honing will fix making new pistons is a better option. We have used Niagara Piston ring they can have a long lead time but quality has been good. You will likely find it is worn a more than you think.

Rick,

We can likely help you with this, even if it’s just to point you in the right direction.

PM me here, or:
Email: erich.armpriester@strasburgrailroad.com
Phone: 717-687-8421, ext. 157

I look forward to discussing with you, if you so choose.

-Erich

Does this bake out need to be done in an inert environment, such as Nitrogen? Or does one want Oxygen present?

Here’s one possibility: https://adpistonring.com/steam-engine-piston-rings.html

For future reference, I have an extensive list of service shops and suppliers for steam locomotives on my page. It hasn’t been updated in a couple of years, but I believe most of the info is still good:

http://www.trainweb.org/tusp/r_links.html

"Does this bake out need to be done in an inert environment, such as Nitrogen? Or does one want Oxygen present?"

Depends on how dirty it is and how hot the oven is. If there are enough oil fumes to create a combustible vapor then an oven will not work.

I suspect a good cleaning of the part before heating it would prevent vapors that could ignite.

If in doubt heat it in a well ventilated place with a torch.

At any low temperature (under 300-400 degrees F) the cast iron will not combine with gases in the atmosphere so nitrogen should not be necessary.

You could try Niagara Piston Rings. Good folks to work with. They custom make all sizes:

http://www.niagarapistonring.com

First question is: are you getting blow by? I hadn't noticed any sign of it in your video postings. These parts can gather a lot of wear before they actually need to be overhauled.

I worked at a plant in the early 1980's that rebuilt their two IR steam reciprocating air compressors. They sent the pistons out to be powdered sprayed with Bronze.

It may help a little to always use the correct terminology. The difference between a piston and bore is "clearance", which will be one single value, like .030", for example. You need to know what the designers intended in order to asses the wear.

When parts are machined they may not come out at the "perfect" intended size. The amount that they can vary from the perfect size is the "tolerance".

If the piston and bore were both allowed a +/-.005" tolerance, then that .030" ideal clearance could actually turn out to be anywhere between .020" and .040"

People sometimes use these term interchangeably, but that is incorrect and can cause confusion.

When I reassembled the cylinders on 58 I just cleaned up the parts and put them back in. There was a lot of slop between the rings and grooves and a considerable gap between the piston and bore. That was fine when we were running on our initial piece of track that was rather flat. However, the new mainline has a sustained grade and 58 doesn't act as if it has much power going up it. One issue for sure is the left side piston rod packing is bad. The new packing arrived yesterday and will be put in today. That should help but I know the pistons also need some attention.

Thanks for the advice.

There is a company in Cleveland called Auto Diesel Piston Ring Company at 3145 Superior Ave. I have never {yet} purchased steam locomotive piston rings from them but they do advertise that they make steam engine rings, and they say that they can make piston rings as large as 30 inches in diameter. Here is a link
https://adpistonring.com/home-dev.html/ ... on-rings-2