Cylinder honing

[jscarmozza]

I'm rebuilding an old 1" scale locomotive, I noticed that the maximum stroke was different in the right and left cylinders. When I got into the cylinders I found two different length pistons, hence the different strokes. But what was really interesting was someone had used packing yarn instead of rings on one of the pistons, a close look at the cylinder sleeve revealed chatter marks from the boring operation which prevented a piston with rings from sliding smoothly. I figured I'd try to hone it smooth before going through the trouble of making a new sleeve. I heard Sunnen hones were the way to go to true a bore and remove material, but their site is very difficult (at least for me) to navigate to make a purchase. That being said, does anyone have an alternate manufacturer or method for honing chatter marks out of a cylinder? Thanks, John

[gwrdriver]

As late as the 1950s graphite wool yarn was commonplace as a piston and gland seal in models!

The first thing I would consider (if I had this problem), before re-sleeve, would be a re-bore and then hone, but Harold should weigh in shortly with what an engine hone can and can't do, meaning how much correction is possible. That may determine for you what your options are.

[Marty_Knox]

John, look for an automotive machine shop in your area. Sunnen is a manufacturer of honing equipment. You need to find someone with their equipment.
The size you are looking for will probably be a brake cylinder hone.

[jscarmozza]

I believe it, the cylinder with the packing yarn had better compression than the one with rings! And that's with a cylinder that looked like it had a screw thread in it!
Hi Marty, good to hear from you, I'll call around, but I don't think any engine shop is going to want to fool around with anything this small. A few years ago I tried to get someone to bore my lawn tractor engine and couldn't find any takers, I wound up doing it myself. This thing would be a royal pain to try to hold and indicate center of bore, that's why I thought that a hone would do the trick.

[Bill Shields]

It is probably the other way around...different length pistons BECAUSE of different strokes.

Depending on the amount of material to be removed a hone may not be the first choice...and depending on the finished od....need to make custom rings.. which is more work than packing it with graphite / packing material.

[Harold_V]

If you're not familiar with Sunnen hones, it may help you to know that it would likely be cost prohibitive (if you choose to do the work yourself) for you to go that route, thus seeking a shop with one is your best choice. Here's why. Bore size will dictate the size of mandrel you'd need, then you'd have to have the machine in which the mandrel is installed. Even on the used market, it's highly unlikely you'd be able to achieve your goal without spending a thousand bucks, but most likely more.

How much must be removed from the bore? Is it cast iron? What diameter is it?

A Sunnen hone in competent hands will be capable of straightening a bore and sizing it to pretty much any tolerance you wish. They are exceedingly capable of high precision, assuming the operator understands proper procedure. A monkey can be trained to operate one, however, so it's no big deal. They are simple to operate.

If push gets to shove and you can't find any help, I own a Sunnen and have a full complement of mandrels, ranging from .120" up to 6". I'd be willing to hone the cylinder for you, although I'm not close. I live in Western Washington.

I strongly advise you to not use a wheel cylinder hone. While it has the ability to improve the surface finish, it isn't able to correct a bore, and is very likely to destroy one if you don't use exceptional care. Even then, you're subject to the luck of the draw.

Piston length does not determine stroke. If you find each side has a different stroke it's because the pins in the drivers are not located identically.

H

[amadlinger]

Hi John,

I agree completely with the other folks that taking it to an engine shop with a hone is the way to go, and I have the place for you. I tried a whole bunch of places around here when I was doing the 2-8-0 cylinders, but seemingly no one had hones small enough for our size...EXCEPT one! I found a hole-in-the-wall motorcycle and small engine shop on Rt 46 in Hackettstown:

Cycle Pro, LLC
107 US-46
Hackettstown, NJ 07840

Its just west of town, well before you get to Hot Dog Johnny's. I was very nervous when I got there and saw the look of the place, but the guy was extremely nice, accommodating, and it came out great. He did both my main cylinder bore and the valve bore (prior to installing the liners), the latter (1-15/16" dia) would probably be equivalent to the size you are looking for.

I hope this helps!

Sincerely,
Adam

[Mike Walsh]

A while back I was looking into having the cylinders re-done for a 12" gauge Pacific due to excessive crosshead play causing divots in the cylinder bore itself. I had no idea where to start - and I knew that machine shops would charge me like crazy for this. Then I realized that there is a machine shop within 10 miles of me that is basically your ol' mom and pop shop. My dad and I have been going there for years to have our cylinder head rework done. Very reasonable and pretty quick. Walk in the door, go down the stairs into the basement where they have a full complement of machines. I have no idea how they got all this stuff downstairs in the basement - they don't own the building above it! But it smells wonderfully of kerosene, machine oil, and cigarettes (ok, that part not so wonderful, but it adds to the charm). Talked to them and they were very interested in making new liners for the piston bore. They showed me around the shop and their army of Sunnen hones. Unfortunately the project went to the back burner and I never moved forward with this.

Ironically, if I tried hard enough, I could probably walk the three blocks and walk around the back of the Sunnen facility, look for the group taking their smoke break and ask for the foreman and see if he would have been willing to help out - or knew someone who might be willing to. Yeah - I live three blocks from Sunnen.

I am confident that if you look around, you'll find an engine shop that has a hone that will go down to the smaller sizes that are common in 1" scale. Stay away from the "race shops". Those are the guys looking to make $$$$$ off of guys who do nothing but put money into their race cars.

Just takes a little looking around. Might try going to your local Autozone and asking if they know any mom and pop shops that do this kind of work.

[jscarmozza]

Thank you all! Hones are out...Cycle Pro here I come.
Thanks for enlightening me, when I started this restoration I found the the distances from the center of axle to center of crank pin to be different on each wheel, and significantly different from side to side (it would only turn with a few bushings removed). I corrected that and made new side and driver rods, everything turned nicely until I connected to the crosshead and one piston bottomed out...and that's where I am now.
I did go through the trouble of making the piston ring jig shown in Nelson's book and making new pistons and rings, they turned out well, one side fits and works as it's supposed to, the other side with the chatter marks not so much. As I'm writing this with the benefit of your comments, I wonder if it would be easier to press out the cylinder sleeve and just make a new one?

[Bill Shields]

making the rings before the bores are a final dimension can be self-defeating.

were it me, I would press the sleeve out and start over...much easier to bore to size in a lathe...

then LAP....

[Doug_Edwards]

If the shop does not work out for you, Sunnen also makes some portable hones that might meet your needs. They can be used in a mill, drill press, or hand drill, and are rigid hones, not spring hones, so will work to clean up your bore.

One place I worked used Ammco (I think that was how it was spelled) cylinder hones for brake cylinders and such. They also are rigid hones, and can be used like the portable Sunnen hones.

You might be able to find either of these on Epay. I think the Ammco hones tend to run cheaper used, as there is less name recognition and that they tend to be found only in automotive circles.

Regards,

Doug

[thunderskunk]

So my only experience with a Sunnen is professional; we’d drill and bore aluminum parts then hone just about every single hole, from .080 to 3” diameter. For the most part setting up the boring bar was more work than it was worth, and our mills were pushing 35 years old, so the honing was more to make up for bad drilling and boring. Their bore gages are top-notch, with top-notch pricing.

If the cylinder is getting rings, does the bore really need to be honed? From an engineering stand point, I’d think the piston rod would do all the work centering the piston in the cylinder, the ideal scenario would be the piston not rubbing against the walls, and the rings making the seal over the gap produced by clearance and sliding fits throughout.

I’m not being sarcastic, I’m curious. I don’t design engines, I just do whatever the heck the print tells me to do.