Cylinder Bore Reconditioning

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Fender
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Cylinder Bore Reconditioning

Postby Fender » Sat Aug 26, 2017 8:53 pm

I'm trying to decide whether the cylinders on the LE mogul I have need to be re-honed or re-bored. I'm getting a bit of a "blow" when it is running, meaning that I hear steam continuously escaping out the stack when running, rather than clean "chuffs". On occasion, if I get the water level in the boiler too high (and the engine primes), the problem seems to get worse. This loco has bronze cylinders with cast iron sleeves, and slide valves. I've looked in the valve chests and they both look good, nice smooth shiny metal with good lubrication. Today I pulled the cylinder heads and examined the cylinder bores. The right side looks ok, but the left has a little corrosion on the bottom of the cylinder. See photos below.
So the question for the brain trust: should I re-hone the left (or maybe both) cylinders? I pulled the left piston to examine the rings, and they look good, no corrosion or scoring, and the rings move freely.
The "blow" might have another cause. I understand that there is a history of porosity in the cylinder castings for this particular model (the castings are at least 40 years old), and it could be that there are leaks between the steam passages. Don't have a way of diagnosing this, nor a remedy if this happens to be the case :(
Attachments
LE Mogul Left Cylinder Bore resize.jpg
Left Cylinder
LE Mogul Right Cylinder Bore resize.jpg
Right Cylinder
Dan Watson

Greg temp
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Re: Cylinder Bore Reconditioning

Postby Greg temp » Sat Aug 26, 2017 9:19 pm

I'd suggest giving both cylinders a hone,can't do any harm,if you rebore them then I'm surmising you'd have to re ring it as well,
It's better to try and fail than not to try at all,

BClemens
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Re: Cylinder Bore Reconditioning

Postby BClemens » Sat Aug 26, 2017 10:53 pm

Fender,

That's a tough call... You probably should do more 'checking' before making a final decision. With the possibility of casting porosity, that decision becomes somewhat complex without going farther with the 'tear-down' and make some checks and tests of the cylinder inlet passage ways - that test could also check ring seat at the same time. That may involve removing the 'D' valves if need be, make a sort-of rubber stamp type of blockoff/manifold that fits the ports and with the pistons at their extreme end of travel, blow compressed air into the port. Oil the rings well and you should get little if any blowby on the rings but you could also note and hear a loss of air pressure due to the possible porosity. Actually unless the castings are porous enough to cause all of the ports to relief over into the associated exhaust port - it would seem unlikely that they are all leaking due to porosity. My suspicion is too loose rings or rings that have not totally seated to the bore. By your photos, one bore looks like corrosion damage but not so much to need rebored - a flex hone would probably clean that up. (but it's a photo....)

I watched a mechanic check condition of the rings on a steam engine (10"x12") on a steam powered mill (that made locust insolator pins for telephone pole cross beams - giving away my age). He basically blocked the piston at the extreme end of travel at the crosshead and blew air into that end steam port. He made a wooden block to cover the port along with some oily rags and noted the loss of air pressure (compression check) - in this case he did not need to remove the valve because the ports are exposed - or in open position; only the chest cover was removed. I never witnessed the actual replacement of the rings. That mill was located in Huntersville, WV - near Marlington. I spent many entire summers at the mill with my grandparents.
BC

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Dick_Morris
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Re: Cylinder Bore Reconditioning

Postby Dick_Morris » Sat Aug 26, 2017 11:52 pm

Just thinking out loud - You may be able to remove the valve and put a layer of rubber gasket in the steam chests, held against the ports with a piece of wood and the steam chest cover. Heads are left in place. That should isolate the cylinder block just to those passages between the valve and the cylinder and isolate the passages from each other. Block the driver through the spokes so the piston won't move and remove the cylinder cocks. Apply a few pounds of pressure through one cylinder cock port and see if the blow-by in one cylinder is worse than the other.

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Marty_Knox
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Re: Cylinder Bore Reconditioning

Postby Marty_Knox » Sun Aug 27, 2017 7:52 am

How well do the rings fit in the piston? Steam leakage past rings is more often between the ring and the piston, rather than between the ring and cylinder bore.

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Fred_V
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Re: Cylinder Bore Reconditioning

Postby Fred_V » Sun Aug 27, 2017 8:06 am

With a 40 year old engine the rings could be worn and the gap has opened up or the rings could be rusted in the piston. Looks like the engine was put up wet at some time in it's life.
Here is an engine I helped rebuild that was put up wet 25 years ago. Still had water in the cylinders.
Attachments
Termite Pics 4 003.jpg
Fred V
Pensacola, Fl.

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cbrew
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Re: Cylinder Bore Reconditioning

Postby cbrew » Sun Aug 27, 2017 8:12 am

having already addressed this issue on a friends loco. here is what i would do if this was me,
if the issue is related to bore damage, the blow by will likely only happen at specific areas. if the blow by is present through the full stroke, its either will be defective ring/s or valve seat, casting defeat, etc.
1) pull the pistons and inspect the rings.
2) pull the rings and check the gap.
3) using a bore gauge, inspect the bore for being "out of round", if found, likely will need re boring, new pistons and rings.
4) since its has slide valve. i would lap the valves. blue the surface, using a piece of glass and a piece of 2000 grid wet sanding paper. round the valve in a figure 8, it should clean up evening in a couple figure 8 passes. rinse and repeat on the other valve and casting surface.
if it does not clean up, you likely have found the problem.

these first three pictures are from my allen american, I bought the chassis 18 years ago even tho it run ok for 14 plus years, i still found machining defects that i had to fix during the full rebuild.
amer1.jpg
as pulled

amer2.jpg
resurfacing

amer3.jpg
finished


here is want i found on the "machined" cylinders for the ten wheeler project. even tho the surface looked "ok"
using the bluing process, i found a defect that would have been a major issue with blow by :)
ten2.jpg

ten1.jpg

ten3.jpg

just food for thought, good luck
If it is not live steam. its not worth it.

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Fender
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Re: Cylinder Bore Reconditioning

Postby Fender » Sun Aug 27, 2017 1:18 pm

Thanks for all the advise. To answer a few questions, I inspected the rings on the left side. I haven't measured their width nor the width of the groove, but they seem tight and move freely. The rings are "stepped" so that there is an overlap at the joint. Next, I'll take a look at the right side piston and rings. Also check the bore diameter on each side.
Before trying to do any honing or grinding, I need to do some more diagnosis. I like the idea of blocking the drivers and putting air pressure in the cylinders. It wouldn't be difficult to disconnect the steam lines in the smokebox and put air pressure separately into each side, to try and isolate the problem or problems. I could also disconnect the valve gear and move the valve manually to see how well it seals in various positions.
Dan Watson

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Fred_V
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Re: Cylinder Bore Reconditioning

Postby Fred_V » Sun Aug 27, 2017 3:10 pm

A friend has a K-27 with cyl liners and had the same symptom of constant steam coming out the stack. It was a tapered cyl liner that was passing steam at the loose end.
Fred V
Pensacola, Fl.


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