Piston and Cylinder Clearance?

[Steve Harris]

Hello Fellow Stakkers.
We a Friend with a Waterloo under restoration. Long ago the mice found a comfortable home in the cylinder. The nest left an area that is badly pitted. He has found a shop in his area capable of making repairs to the cylinder.

What we are looking for is if someone whould have figures on what the clearence gap between the cylinder and piston should be.

Thanks for the Help.

[SleepyEyedJohn]

Hi Steve,
Check this out...
http://www.smokstak.com/forum/showthread.php?t=26109

Start with 0.001" and then add 0.001" per inch of cylinder bore.

I'm sure our friend Nick could elaborate further, if needed. I don't have my design books handy at work...about 4,300 miles out of reach.

Take care,
John

[Pat Barrett]

John is absolutely correct in the previous post. Add, .001 to begin with and then add ,001 for every inch of diameter.

[DaveWachter]

On cast iron or aluminum you kneed about.004 thousandths per in or when she gets hot she will stick tight now on real large boars this will not work as it will get real loose. Ps ask your machinest he mayhave the answer .004 up to 6 in will work fine dave wachter

[J.B. Castagnos]

Originally Posted by DaveWachter

On cast iron or aluminum you kneed about.004 thousandths per in or when she gets hot she will stick tight now on real large boars this will not work as it will get real loose. Ps ask your machinest he mayhave the answer .004 up to 6 in will work fine dave wachter

Dave, I think you're off on this . There's no way you need .016" on a 4 inch bore. I usually go a thousandth per inch on the cylinders I sleeve, most have been in the 3 1/4 to 4" range. The extra thousandth mentioned would be more critical on smaller bores, larger bores can be a little tighter.

[Eric M.]

The 0.001" per inch of cylinder bore is only good for engines under 8" bore. Nordberg Diesel engines, even their HUGE ones (30" and bigger bores) were designed with 0.001" per inch diameter up to 8" diameter. Even their biggest diesel pistons were designed for a maximum of 0.008" clearance.

[Steve Harris]

Thanks for the replies, Folks.

We are aware of the 0.001" per inch bore rule but we were uncertain if this would still apply to a cyclinder with such a large bore such as one on a steam tractor.

John thanks, and you're nailed it...Nick, this one is right up you're alley. Give us a reply.

Hows the weather at work John? It must be like a tropical vacation to come home to sunny Ohio.

[Kelly Tytlandsvik]

I believe the .004 per inch of cylinder should refer to the end gap in the rings .......not piston to cylinder clearance. I believe gas engines have .003 to .005 inch clearance between cylinder and piston on bores in the 3-5 inch range. I am not sure the clearance for a steam cylinder though as I have never done one........ so I am not much help in that respect.

Kelly T

[Nick Stanley]

Hello John, Steve, and all,

I have very few steam engineering books with me at school, and the few that I went through today had nothing on the topic. When overhauling a small vertical engine several years ago that had significant cylinder wear, I was interested in trying to find what was considered acceptable for piston-cylinder clearance when new. I found very few books that even mention the topic at the time. I don't have the measurements I took from the Baker with me either, for comparison.

I have used the "thousadth per inch of diameter" rule for bearings under about 8" dia., and it seems to work well in one that is well fit-up with good contact. I think it would also be ok for piston/cylinder clearance, but I would try to err on the side of more clearance, as the velocity is higher. On the 21-75 Baker the tangential velocity, at 250 rpm, of the crank journals is ~ 245 ft/min, while the maximum piston velocity at the upper and lower quarters is ~654 ft/min. Also, unless the crosshead guides are bored with the cylinder, they will probably not be perfectly straight or perfectly in line with the cylinder, and a little more clearance could be allowed in this case than would be for a new engine. Just some thoughts.

One reference I do have are some drawings from a vertical triple-expansion Corliss. The HP, IP, and LP cylinders have bores on the order of 30, 60, and 100 inches, and a stroke of about 60". What is interesting to note on this large engine is that the piston-cylinder clearance is the same on all three cylinders. The center ring land is dimensioned fractionally as 1/32" less than the cylinder bore, while the outer ring lands were turned to 1/16" less than the bore, in the case of all cylinders. So, a HP cylinder sleeve, which was steam jacketed, is dimensioned as being bored to 2'-6" dia. "run." No tolerance is given other than the note "run". The respective piston has a center land diameter of 2'-5 31/32" and outer lands of 2'-5 15/16". The Baker piston is machined in this way. If you look at the end of the piston in the cylinder, it looks to have about .100" too much clearance. However when the piston is removed, the center land is turned to fit the bore nicely.
It appears that the "thousandth per inch of diameter" rule is followed in the case of the HP cylinder, but not in the case of the IP and LP cylinders, which use the same clearance with a larger diameter. Note that this is a vertical engine, and there may be a difference in the amount of clearance allowed for a horizontal engine. It is also unclear to me what the note "run" means, other than that the machinist should aim to have the bore larger rather than smaller for a running fit?

A reference giving the information your looking for directly was posted by Gary K some time ago. Here's a link to his post: http://www.smokstak.com/forum/showthread.php?t=54511
The information is in the 7th post. Gary K's information recommends that the clearance be 0.015" for a bore of 10" or less.

Using modern ANSI standard for fits from Machinery's Handbook, for a cylinder bore an ANSI RC 7 free running fit may be correct. If the cylinder bore is between 7.09 and 9.85 inches, an RC 7 fit gives a clearance range of 7.0 to 14.3 thousandths of an inch with a hole tolerance of +4.5/-0 thou and a shaft(piston) tolerance of -7.0/-9.8 thou from the nominal. What is the bore diameter now and about how much will need to be removed to clean it up?

This is an interesting design problem that I have very little information on. Perhaps someone with Case(or any maker's) blueprints could post clearances that were used. Sorry for the long post, I hope it helps out somewhat.

-Nick

[Gary K]

Hi Nick:
My MODERN MARINE ENGINEER'S MANUAL has these tolerances up to 80" bore. If your interested, I'll scan them, and post it, as it's too much typing? (It's a challenge making all of this fit properly on this website!) Also have tolerance's for PISTON VALVE BORES, PISTON VALVES, and PISTON VALVE RINGS, etc., .....if your interested?

Below I have tolerances for reciprocating steam pumps, in case someone is interested?

RECIPROCATING PUMPS
(All measurements are in inches)

Steam Cylinders
................. Designed clearance........ Maximum Permissible
Cylinder..... between piston and..................... Taper or..Total clear' between
diameter......... cylinder............ Out of round..barreling.. piston and cylinder
Up to 7.5" ......... 0.008" ............... 0.010" ...... 0.020" .......... 0.030"
8 to 11" ............ 0.013" ............... 0.018" ...... 0.030" .......... 0.050"
11.5 to 16.5" ..... 0.018" ............... 0.025" ...... 0.045" .......... 0.100"
17" & Over ........ 0.024" ............... 0.035" ...... 0.060" .......... 0.100"

Auxiliary Piston Valves
Up to 3" ........... 0.004" ................ 0.003" ...... 0.006" .......... 0.010"
3 to 5" ............. 0.005" ................ 0.004" ...... 0.007" .......... 0.014"
5" & over ......... 0.007" ................ 0.005" ...... 0.009" .......... 0.020"

Cylinders, Liquid,High-pressure Pumps (Feed, Fuel Oil, Lubricating, etc.
Up to 7.5" ....... 0.031" ................ 0.010" ...... 0.012" ......... 0.051"
8 to 11" .......... 0.031" ................ 0.018" ...... 0.016" ......... 0.056"
11.5 to 16.5" ... 0.031" ................ 0.025" ...... 0.020" ......... 0.061"
17" & Over ...... 0.063" ................ 0.035" ...... 0.025" ......... 0.113"


Gary K

[Nick Stanley]

Gary,

I'd be very much interested in a scan of that information of the tolerances up to 80" and the piston valves, Thanks again! What is the author and publisher of that book?

-Nick

[Gary K]

Originally Posted by Nick Stanley

Gary,

I'd be very much interested in a scan of that information of the tolerances up to 80" and the piston valves, Thanks again! What is the author and publisher of that book?

-Nick

Nick:

MODERN MARINE ENGINEER'S MANUAL
Editor-in-Chief, ALAN OSBOURNE.
U. S. Maritime Commission.

CORNELL MARITIME PRESS
Cambridge, Maryland

I don't know when I'll get that stuff scanned, as I got too many irons in the fire today . . . hopefully soon?

Gary K

[Steve Harris]

Nick and Gary,

Thank You Both for the very helpful information.

[Gary K]

Originally Posted by Steve Harris

Nick and Gary,

Thank You Both for the very helpful information.

Steve & Nick:

Here's 3 scans: Cylinder, piston valve, and eccentric tolerances that I scanned off.












I have two more on bearing clearances, but I'll have to post them on another posting!


Gary K

[Gary K]

Steve & Nick:

Here's two on bearing clearances . . .hope you can read them without too much trouble?








I also have a chart on cylinder linear clearance, more on reciprocating pumps, and one pertaining to pins, guides, bearing in stems, valve links, etc., clearances. I will post them if your interested?


Gary K

[Nick Stanley]

Thanks again Gary! Very handy and interesting information, and it looks like I need to be on the lookout for copy of that book!

-Nick

[Rob Bryce]

Hi Gary,

More scans would certainly be appreciated! Is this from the 2nd edition of the book in 1965?

--Rob

[Gary K]

Hi Rob:

How did you know this is the 2nd Edition . . . and 1965?

I have Volumes 1 and 2. Looking at Volume 1, I'll write down some of the information on one of the first pages:

MODERN MARINE ENGINEER'S MANUAL
Volume 1. Alan Osbourne
Second Edition
A. Bayne Neild, Jr., Editor-in-Chief

NOTE: There's 11 contributing editors I won't write down!

CORNELL MARITIME PRESS, INC.
CAMBRIDGE 1965 MARYLAND

Looking at Volume 2, there's no mention of it being 2nd Edition or the year 1965 . . . just Volume 1?

Here's a scanning of Linear Clearances I have on file:





Gary K

[Rob Bryce]

Thanks Gary,

I appreciate the spec's that you've posted. I took a guess at the edition you had after googling the book info you had earlier posted, that's all.

You posed a question earlier about what other companies were doing for clearances. The Case 75 drawing for the eccentric shows basically half-again more diametral clearance but did not specify side clearance (may have been on an earlier revision that I don't have). I suspect this change may be due to the lubricants of the day.

--Rob

[jht1057]

Hi Gary,

I know this is a rather old post, but would you happen to have the ISBN number for the book you are referencing in this post?

Thank you, Jim