1 Steam Cars : Phorum
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Engine clearances
Posted by: Kobus van Jaarsveld (IP Logged)
Date: May 02, 2002 04:03PM
<HTML>
We are rebuilding the EX engine and have to make new cast iron pistons and rings.
Can someone please advise the correct piston to bore clearance and ring gap. Also the sliding valve faces on the cylinder block are scored. How much metal can be removed here before the actuation of the valces are compromised ?</HTML>
We are rebuilding the EX engine and have to make new cast iron pistons and rings.
Can someone please advise the correct piston to bore clearance and ring gap. Also the sliding valve faces on the cylinder block are scored. How much metal can be removed here before the actuation of the valces are compromised ?</HTML>
Re: Engine clearances
Posted by: Kobus van Jaarsveld (IP Logged)
Date: May 02, 2002 05:12PM
<HTML>
Finger trouble, I meant valves.</HTML>
Finger trouble, I meant valves.</HTML>
Re: Engine clearances
Posted by: ronald parola (IP Logged)
Date: May 02, 2002 11:51PM
<HTML>I don't know about valve surfaces, but I'm running 5thou piston clearence with no problems, and 12 thou ring gap, cut at a diagonal. good luck Ron P</HTML>
Re: Engine valve ,shaper job
Posted by: C Benson (IP Logged)
Date: May 03, 2002 12:41AM
<HTML>The valve surface is proud in the steam chest,,,If U machine it ,,,remember the valve MUST NOT run into a ''hill''as it reaches FULL TRAVEL <<<<< FULL GEAR ,,,that is ,,full ahead [or rev'],,,,,If necessary clean the corners by hand if necessary,,,, even w/ a chisel ,,,Now remember take only smallest amount off JUST enough so it dont leak ,,,,Youre talkn'n junkin a block,,, right here ,, NOW !! Dont mean to be harsh,,,only to get your FULLEST attention,, If U clean the valves on a shaper ,,make the cut 90 deg to the valve seat cut ,,they will polish in better,,,Hey Dave we need your fatherly comments on the FEEL of the pedal after a re/fit U can choose the words better than I Cheers Ben p/s Shaper tool chatter NOT allowed,,practice first,,,...</HTML>
Piston ring end gap
Posted by: Pat Farrell (IP Logged)
Date: May 03, 2002 02:41PM
<HTML>As told to me years ago by Hemo Schuur, a German machinist, "a steam engine does not need piston ring gap clearance like a gas engine does. Use zero clearance". There isn't any heat generated in the steam cylinder like a gas engine does, and therefore steam parts all run at the same temperature. Since all the parts are cast iron they all expand at the same rate with no binding. Push your new rings all the way through the cylinder and check for binding. If they bind up because of too big, grind more off the ends until they pass freely. As they wear in, they will increase their end gap. Personally, I like to fit them with 0.005" or less clearance.</HTML>
Re: Engine valve ,shaper job
Posted by: Kobus van Jaarsveld (IP Logged)
Date: May 03, 2002 07:10PM
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Dear Coburn,
Thanks for your advice, you have secured my full attention. On our block, the valves slide fore and aft between two ridges, one on each side of the valve. These serve to locate the valves so they cannot deviate more than a fraction up or down as they perform their work accross the ports. The ridges are the full length of the valve travel about 1/8 inch wide by 1/16 inch high. There are no "hills" at the ends of the valve path.
The problem with shaping the block at right angles to the direction of valve movement is that the ridges will be removed in the process. The shaper tool will not work in a closed flat valley.
My intention was to use a small dia milling cutter in the Bridgeport milling machine and to mill metal away between the ridges in the same direction as valve travel until the scoring is just gone. This will of course make the ridges,as seen by the valves, more pronounced.
Further guidance and comments will be appreciated. Junking the block is unthinkable. Best regards, Kobus</HTML>
Dear Coburn,
Thanks for your advice, you have secured my full attention. On our block, the valves slide fore and aft between two ridges, one on each side of the valve. These serve to locate the valves so they cannot deviate more than a fraction up or down as they perform their work accross the ports. The ridges are the full length of the valve travel about 1/8 inch wide by 1/16 inch high. There are no "hills" at the ends of the valve path.
The problem with shaping the block at right angles to the direction of valve movement is that the ridges will be removed in the process. The shaper tool will not work in a closed flat valley.
My intention was to use a small dia milling cutter in the Bridgeport milling machine and to mill metal away between the ridges in the same direction as valve travel until the scoring is just gone. This will of course make the ridges,as seen by the valves, more pronounced.
Further guidance and comments will be appreciated. Junking the block is unthinkable. Best regards, Kobus</HTML>
valve ,shaper job,lap? temp
Posted by: C Benson (IP Logged)
Date: May 03, 2002 11:44PM
<HTML>The original surface did not have the guide ridges U speak of,,,WHEN the valve surface wears it becomes low in the middle,,,and for this reason , changing the valve adj' is to be avoideed on a worn engine,,,somehow I suspect someone has cut this surface purposly this way,,,CAN anyone tell us if this has been seen before,, I would look at possibly using a dummy cast iron LAP to lap out the grooves ,, this would be trickey ,,,U would need to go back an fourth AND sideways !! Can U estamate how much needs to be taken off to clean the surface?? Does it seem to be flat across the middle?? Good luck an' dont forget the tea at 4, for jobs like this it's essential,,[Carl 'n I differ on this haha]] , as ever Ben. P/s Pat,,,,I disagree,,,,The small parts heat sooooner,,,so there WILL be clearence changes ,,,Ongoing,,,as the engine heats,,,,CB</HTML>
Re: valve ,shaper job,lap? temp
Posted by: ronald parola (IP Logged)
Date: May 04, 2002 01:46PM
<HTML>I believe the "ridges" are just the valve seat surface worn away, the vavles don't need to be located sideways. Ron P</HTML>
Re: valve ,shaper job,lap? temp
Posted by: George K. Nutz (IP Logged)
Date: May 05, 2002 02:23PM
<HTML>Kobus,
Ed Gallant had refaced and made a large quantity of 20 and 30HP blocks, possibly did hundreds of valve seat surfaces. There were never any side guide ridges, some blocks would come in with almost 1/4" of wear and the valve seats were "rocking chair" shape and they were junked---to think the engines would still run with all of this!!! He had a special antique machine that would finish the valve surfaces perpendicular to the valve travel direction, Coburn would know what this machine was/is. Sounds like you have had a little bit of wear that could be taken care of.
Best , George</HTML>
Ed Gallant had refaced and made a large quantity of 20 and 30HP blocks, possibly did hundreds of valve seat surfaces. There were never any side guide ridges, some blocks would come in with almost 1/4" of wear and the valve seats were "rocking chair" shape and they were junked---to think the engines would still run with all of this!!! He had a special antique machine that would finish the valve surfaces perpendicular to the valve travel direction, Coburn would know what this machine was/is. Sounds like you have had a little bit of wear that could be taken care of.
Best , George</HTML>
Re: valve ,shaper job,lap? temp
Posted by: Kobus van Jaarsveld (IP Logged)
Date: May 06, 2002 12:57PM
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I drove to Pretoria this afternoon where my machinist and I took some careful measurements:
Distance from top of ridges to current valve surface 0.022 inch
Amount of metal to be removed to get to below score marks 0.029 inch
Amount of metal that will remain proud of the cylinder casting after machining 0.031 inch
The observation that the ridges are the result of previous machining is clearly correct. We will now proceed with the job and shape the ridges away and then go down until the scoring is gone. I am relieved that a significant platform will remain when the job is done.
Thanks to Ron, Ben, Pat and George for your wisdom, and thanks to JW for providing this excellent facility. How else would we, living in the Southern tip of Africa, have made sense of it all?</HTML>
I drove to Pretoria this afternoon where my machinist and I took some careful measurements:
Distance from top of ridges to current valve surface 0.022 inch
Amount of metal to be removed to get to below score marks 0.029 inch
Amount of metal that will remain proud of the cylinder casting after machining 0.031 inch
The observation that the ridges are the result of previous machining is clearly correct. We will now proceed with the job and shape the ridges away and then go down until the scoring is gone. I am relieved that a significant platform will remain when the job is done.
Thanks to Ron, Ben, Pat and George for your wisdom, and thanks to JW for providing this excellent facility. How else would we, living in the Southern tip of Africa, have made sense of it all?</HTML>
Re: valve ,shaper job,lap? temp
Posted by: Kobus van Jaarsveld (IP Logged)
Date: May 06, 2002 01:03PM
<HTML>
I understand that the scoring of valve surfaces is caused by poor lubrication
Is this the only cause and how does it come about that one gets a score mark almost 29 thou deep if lack of oil is the only enemy? How do I make sure I never have to do this job again?</HTML>
I understand that the scoring of valve surfaces is caused by poor lubrication
Is this the only cause and how does it come about that one gets a score mark almost 29 thou deep if lack of oil is the only enemy? How do I make sure I never have to do this job again?</HTML>
Re: Engine clearances
Posted by: David K. Nergaard (IP Logged)
Date: May 07, 2002 10:44AM
<HTML>The usual recommended clearance for pistons in steam engines was one thousandth of an inch per inch of diameter. This means about 0.003 for any Locomobile.
I have read of a locomotive repair shop that planed worn valve seats perpendicular to valve travel and the valves, parallel to travel. This meant the machining marks crossed at right angles when the engine was assembled. The valve was then allowed to bed itself in while in use. I have tried this method and find it successful. One drives the car about a hundred miles in long cutoff, to get the maximum valve stroke with minimum steam pressure on the valve. For the first fifty miles or so, the engine is very rough, but it soon smooths out and runs very nicely for the next several thousand miles, if properly lubricated.
This method has the advantage that the final valve surface is obtained under normal operating conditions with the valve and block hot. I feel that careful fitting the valve to the seat when at room temperature is a waste of effort, the valve won't be the same shape when hot. The Stanley factory ran their engines for several hours on a "test" stand before fitting them to the cars. I think they were actually quickly bedding in the valves under controlled conditions, possibly without oil.</HTML>
I have read of a locomotive repair shop that planed worn valve seats perpendicular to valve travel and the valves, parallel to travel. This meant the machining marks crossed at right angles when the engine was assembled. The valve was then allowed to bed itself in while in use. I have tried this method and find it successful. One drives the car about a hundred miles in long cutoff, to get the maximum valve stroke with minimum steam pressure on the valve. For the first fifty miles or so, the engine is very rough, but it soon smooths out and runs very nicely for the next several thousand miles, if properly lubricated.
This method has the advantage that the final valve surface is obtained under normal operating conditions with the valve and block hot. I feel that careful fitting the valve to the seat when at room temperature is a waste of effort, the valve won't be the same shape when hot. The Stanley factory ran their engines for several hours on a "test" stand before fitting them to the cars. I think they were actually quickly bedding in the valves under controlled conditions, possibly without oil.</HTML>
Re: valve ,shaper job,lap? temp
Posted by: C Benson (IP Logged)
Date: May 07, 2002 10:52AM
<HTML>It sure gets to be a small world,,Hope we can share a meal someday,,,It is verry,,/VERRY good U have metal above [the surface]to work on My thot' was Stanley didn't leave much so they would sell blocks,,,Maybee all the blocks ive seen are hi milage,,OOOO The slot BEHIND the valve surface is needed for the shaper tool to clear OOOO Old shaper hands are hard to find now,, so if he's under 85 warn him about chatter,,,haha tell him I said so What make of shaper do U have there,,,Are most tools English or other??Stanley factory had a Uxbridge 14-16'' they had a unique fast return by eccentric gear!!! Mine weighs about 4000# but is not under power after my move [ 100mi ] I thot it to be a interesting add'n to my stanley collection Who else would,,,,,oh forget it,, Cheers Ben</HTML>
Re: Engine /Plainin' valve
Posted by: C Benson (IP Logged)
Date: May 07, 2002 11:03AM
<HTML>Thanks for this verry important detail overlooked by many TOO MANY Thanks again,, Ben P/s Dave,, please explain the FEELING in the pedal ,,,when all is well an' when it all just went south,,,cb</HTML>
Re: Engine clearances
Posted by: Rolly Evans (IP Logged)
Date: May 07, 2002 03:29PM
<HTML>I agree with the .001 for clearance per inch of diameter. However this is on each side of the piston. A three-inch piston would be finished cut .006 smaller in diameter then the cylinder bore.
Rolly</HTML>
Rolly</HTML>
Re: Engine /Plainin' valve
Posted by: David K. Nergaard (IP Logged)
Date: May 08, 2002 12:02PM
<HTML>When the valve is rough, it causes vibration in the reverse pedal, especially when the steam pressure is high (climbing a hill). If the valves have bedded in correctly, there will be little, if any, pedal vibration, even when climbing hills. You will be able to hook up or go to long cut off without feeling any "kick" in the pedal.
If, in normal driving, you hear or feel pedal vibration, it is a sign that all is not well. Check lubrication and, if the vibration is bad, go to long cutoff on hills to relieve the pressure on the valves. It is also a good idea to completely close the throttle from time to time so oil can get under the valves.</HTML>
If, in normal driving, you hear or feel pedal vibration, it is a sign that all is not well. Check lubrication and, if the vibration is bad, go to long cutoff on hills to relieve the pressure on the valves. It is also a good idea to completely close the throttle from time to time so oil can get under the valves.</HTML>
Re: Engine /Plainin' valve
Posted by: ronald parola (IP Logged)
Date: May 09, 2002 01:41AM
<HTML>For what it's worth I run mine on compressed air for a few hours (we've got a BIG compressor at work) with an automatic line oiler ( air motor oil) and that seems to bed the valves in fine. Probably not as well as under steam but well enough that it cuts out the break in time RON P</HTML>
Re: Deep Scratches
Posted by: Peter Heid (IP Logged)
Date: May 13, 2002 12:01AM
<HTML>With score marks .029 deep, I would guess there was some foreign matter floating about. In the machine shop work I am familiar with the only other reason for such deep grooves in wearing parts would be galling of metals that are not appropiate for use together under the influence of available lubrication.
Peter Heid</HTML>
Peter Heid</HTML>
Engine clearances
Posted by: Pat Farrell (IP Logged)
Date: May 23, 2002 02:46AM
<HTML>For piston clearances and ring gap on the Stanley 20 H.P., I agree with Ron Parola of 5 thou for the piston clearance and 12 thou for the ring end gap. Any less than that, would create excess drag. I put it to the test today and that is what I found out. I also had to cut my piston ring grooves deeper as my new piston rings needed the clearance.</HTML>
Re: Engine clearances
Posted by: Kevin Harpham (IP Logged)
Date: January 23, 2003 05:03AM
<HTML>I’m not sure if anybody will see this due to how old this thread is but I was wondering, when designing a steam engine what is the absolute minimum clearance you could put between the top of the piston and the cylinder head without risking damage and what would this clearance be when hot?
Assume that the proper materials were used and the engine was well constructed.
Also I don’t know if these are any factors but lets say it is single acting, has a 4 inch stroke and a working temperature of 700 degrees.
Kevin Harpham</HTML>
Assume that the proper materials were used and the engine was well constructed.
Also I don’t know if these are any factors but lets say it is single acting, has a 4 inch stroke and a working temperature of 700 degrees.
Kevin Harpham</HTML>
Re: Engine clearances
Posted by: Turd Ferguson (IP Logged)
Date: April 14, 2004 12:36PM
<HTML>your gay and really gay</HTML>
Re: Engine clearances
Posted by: Turd Ferguson (IP Logged)
Date: April 14, 2004 12:38PM
<HTML>zane wants to make sweet love to you when u bend over at night....because your gay and hes gay</HTML>
Re: Engine clearances
Posted by: john (IP Logged)
Date: February 25, 2005 12:02PM
<HTML>what im going to do if the engine turn into over heat
<a href="http://steamgazette.com/phorum-3.3/profile.php4?f=1&id=3">Kobus van Jaarsveld</a> wrote:
>
>
> We are rebuilding the EX engine and have to make new cast
> iron pistons and rings.
> Can someone please advise the correct piston to bore
> clearance and ring gap. Also the sliding valve faces on the
> cylinder block are scored. How much metal can be removed
> here before the actuation of the valces are compromised
> ?</HTML>
<a href="http://steamgazette.com/phorum-3.3/profile.php4?f=1&id=3">Kobus van Jaarsveld</a> wrote:
>
>
> We are rebuilding the EX engine and have to make new cast
> iron pistons and rings.
> Can someone please advise the correct piston to bore
> clearance and ring gap. Also the sliding valve faces on the
> cylinder block are scored. How much metal can be removed
> here before the actuation of the valces are compromised
> ?</HTML>
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