1 Steam Cars : Phorum
General Steam Car topics
Valve gears
Posted by: David K Nergaard (IP Logged)
Date: November 22, 2002 11:24PM
<HTML>Maybe we need a new thread on this subject.
I can vouch for the quality of the twin cam Skinner valve gear, having often sailed on a ship fitted with two Skinner uniflow engines: R. V. Atlantis II out of Wood's Hole. Standing between those two 735 hp. in the engine room, the loadest noise was the air conditioning! While manuevering the ship to pick up an instrument, it was quite possible to move the ship forward a fathom or so and stop it as needed, which involved giving the engines half a turn forward followed by a fourth of a turn back to kill the momentum!
I always tried to visit the engine room of any steamer I boarded. On one of the Staten Island ferrys, I saw the largest steam engine I ever saw running: a six cylinder Skinner of 6000 hp. This engine seldom ran at its rated power as it shared a schedule with older and slower boats.
An hydraulic valve gear somone might investigate is that of Henry Pilling, used on Galloway Uniflow engines in England. The gear is described in "The Uniflow, Back Pressure and Steam Extraction Engine" by T. Allen, Pitman & Sons, London, 1931, pp. 384-389. (I wish I owned a copy of this book, I only have some Xerographed sections!) It might be possible to duplicate this gear starting with an injector pump from a large Diesel engine. (and I do mean large!)
Some locomotive gears to look at are the Caprotti (of which I have some pictures), the Cossart, the Dabeg and the Franklin. The Caprotti uses the same idea as the Skinner, but with both cams on the same shaft. The Franklin used oscillating cams driven by separate linkages for inlet and exhaust. The Cossart was said to be a pneumatic gear, but I am like Sgt. Schultz on this one: "I know NOTHINGK!" I believe the Dabeg was like the Serpollet sliding cam shaft, but have never seen drawings.
Do any of you out there know about these gears? 73 DK</HTML>
I can vouch for the quality of the twin cam Skinner valve gear, having often sailed on a ship fitted with two Skinner uniflow engines: R. V. Atlantis II out of Wood's Hole. Standing between those two 735 hp. in the engine room, the loadest noise was the air conditioning! While manuevering the ship to pick up an instrument, it was quite possible to move the ship forward a fathom or so and stop it as needed, which involved giving the engines half a turn forward followed by a fourth of a turn back to kill the momentum!
I always tried to visit the engine room of any steamer I boarded. On one of the Staten Island ferrys, I saw the largest steam engine I ever saw running: a six cylinder Skinner of 6000 hp. This engine seldom ran at its rated power as it shared a schedule with older and slower boats.
An hydraulic valve gear somone might investigate is that of Henry Pilling, used on Galloway Uniflow engines in England. The gear is described in "The Uniflow, Back Pressure and Steam Extraction Engine" by T. Allen, Pitman & Sons, London, 1931, pp. 384-389. (I wish I owned a copy of this book, I only have some Xerographed sections!) It might be possible to duplicate this gear starting with an injector pump from a large Diesel engine. (and I do mean large!)
Some locomotive gears to look at are the Caprotti (of which I have some pictures), the Cossart, the Dabeg and the Franklin. The Caprotti uses the same idea as the Skinner, but with both cams on the same shaft. The Franklin used oscillating cams driven by separate linkages for inlet and exhaust. The Cossart was said to be a pneumatic gear, but I am like Sgt. Schultz on this one: "I know NOTHINGK!" I believe the Dabeg was like the Serpollet sliding cam shaft, but have never seen drawings.
Do any of you out there know about these gears? 73 DK</HTML>
Re: Valve gears
Posted by: G. B. Gilbert (IP Logged)
Date: November 23, 2002 05:12AM
<HTML>There is a freeware valve design program here :
[www.tcsn.net]
that works with Franklin and Caprotti design.</HTML>
[www.tcsn.net]
that works with Franklin and Caprotti design.</HTML>
Re: Valve gears
Posted by: David K Nergaard (IP Logged)
Date: November 26, 2002 04:58PM
<HTML>Peter, instant recognition! That is the Skinner gear. I have sailed on Skinner equipped ships. The valves don't slam.</HTML>
Re: Valve gears
Posted by: Jim Crank (IP Logged)
Date: November 27, 2002 02:20PM
<HTML>Peter,
The Skinner valve gear does not slam nor does it leak. That is a very well engineered valve and valve gear.
Jim</HTML>
The Skinner valve gear does not slam nor does it leak. That is a very well engineered valve and valve gear.
Jim</HTML>
Re: Valve gears
Posted by: David K Nergaard (IP Logged)
Date: November 28, 2002 11:32AM
<HTML>I have found that the Dabeg gear, sometimes called Dabeg-Lentz, is the exact locomotive equivalent of the gear Serpollet used in his steam cars; rotary cams, with the cam shaft slid axially to reverse or change cutoff.</HTML>
Re: Valve gears
Posted by: Peter Brow (IP Logged)
Date: November 29, 2002 12:59AM
<HTML>Hi David and Jim,
Sounds good. Any major disadvantages, relative to older types of valves & valve gear? Has anyone ever successfully used this equipment on automobile-sized engines?
Peter</HTML>
Sounds good. Any major disadvantages, relative to older types of valves & valve gear? Has anyone ever successfully used this equipment on automobile-sized engines?
Peter</HTML>
Re: Valve gears
Posted by: Peter Heid (IP Logged)
Date: November 29, 2002 04:44PM
<HTML>David,
I found the names together also. The Lentz was also in marine use and the detailed drawings I have are for a 2500 Hp 4 cylinder compound engine from 1941 with a chain driven cam, but the article indicates the valve gear was maybe from 1920 or so. I wonder if the Dabeg was what they refered to as "Lentzification" or the implementation of the Lentz valve gear and HP cylinder on other brand steam engines.
Peter Heid</HTML>
I found the names together also. The Lentz was also in marine use and the detailed drawings I have are for a 2500 Hp 4 cylinder compound engine from 1941 with a chain driven cam, but the article indicates the valve gear was maybe from 1920 or so. I wonder if the Dabeg was what they refered to as "Lentzification" or the implementation of the Lentz valve gear and HP cylinder on other brand steam engines.
Peter Heid</HTML>
Re: Valve gears
Posted by: David K Nergaard (IP Logged)
Date: November 30, 2002 12:40PM
<HTML>Serpollet used his sliding cam shaft gear from the late 1890s until his death in 1906. I have no data on the number of cars made, but think it was between 500 to a 1000.</HTML>
Re: Valve gears
Posted by: tom ward (IP Logged)
Date: November 30, 2002 02:31PM
<HTML>I like the idea of a sliding cam. It looks simpler and more rugged than a Stephenson linkage. Make it desmonrhombic instead of using springs.</HTML>
Re: Valve gears
Posted by: Jim Crank (IP Logged)
Date: November 30, 2002 04:28PM
<HTML>Tom,
Make it slightly unbalanced and you don't even need that.
Jim</HTML>
Make it slightly unbalanced and you don't even need that.
Jim</HTML>
Re: Valve gears
Posted by: Mike Bennett (IP Logged)
Date: December 02, 2002 11:54PM
<HTML>Tom,
DESMO!! very tough to design! If you know of a good design for steam desmo, I would be very interested. I once knew a rich guy that tried to run a desmo hemi drag boat. It either went real fast or blew up. After about $100K, he gave up! Us poor guys just plagerize everyone elses design.
Regards,
Mike</HTML>
DESMO!! very tough to design! If you know of a good design for steam desmo, I would be very interested. I once knew a rich guy that tried to run a desmo hemi drag boat. It either went real fast or blew up. After about $100K, he gave up! Us poor guys just plagerize everyone elses design.
Regards,
Mike</HTML>
Re: Valve gears
Posted by: Peter Brow (IP Logged)
Date: December 06, 2002 09:12AM
<HTML>Hi David,
I have read that in his last few years of production, Serpollet dumped his single-acting engine design in favor of a double-acting engine. Supposedly he was very pleased with the change, and stated that the stuffing box leaks he had tried to avoid with the SA layout turned out to be no problem after all.
Did he stick with the sliding-cam/poppet valve gear in his final double-acting engines? I have not been able to find pictures or detailed descriptions of the double-acting Serpollet engines.
I also wonder about the durability of sliding-cam poppet valve gear. Seems like the (roller?) follower would have single-point contact on the cam, and higher load concentrations, as opposed to the line contact possible with rollers on straight cams. With several discrete cutoff positions instead of continuously variable cutoff, it would be possible to have line contact with a sliding cam, and perhaps a more durable valve gear. Line contact may be one of the reasons for the durability of the dual-cam Skinner gear.
Peter</HTML>
I have read that in his last few years of production, Serpollet dumped his single-acting engine design in favor of a double-acting engine. Supposedly he was very pleased with the change, and stated that the stuffing box leaks he had tried to avoid with the SA layout turned out to be no problem after all.
Did he stick with the sliding-cam/poppet valve gear in his final double-acting engines? I have not been able to find pictures or detailed descriptions of the double-acting Serpollet engines.
I also wonder about the durability of sliding-cam poppet valve gear. Seems like the (roller?) follower would have single-point contact on the cam, and higher load concentrations, as opposed to the line contact possible with rollers on straight cams. With several discrete cutoff positions instead of continuously variable cutoff, it would be possible to have line contact with a sliding cam, and perhaps a more durable valve gear. Line contact may be one of the reasons for the durability of the dual-cam Skinner gear.
Peter</HTML>
Re: Valve gears
Posted by: David K Nergaard (IP Logged)
Date: December 06, 2002 12:28PM
<HTML>Serpollet continued to use his sliding cam gear with the double acting engine. I agree that the point contact is an issue, but wonder if it not too serious as it is on the falling edge of the motion rather than on the lift. A stepped cam is an obvious answer.</HTML>
Re: Valve gears
Posted by: Peter Brow (IP Logged)
Date: December 07, 2002 07:08AM
<HTML>One thing I have sketched up a few times in the past is a combination stepped/sliding cam unit. The steps in the cam have transitional ramps between them, and the roller followers have coned ends to ride easily over the transition ramp surfaces when the cam is shifted. This gives line contact for better load distribution/less wear, and makes it easier to shift than with some mechanism to lift the followers then drop them after the cam has shifted, but the price of this mechanical simplicity is a longer cam unit which introduces packaging problems.
Peter</HTML>
Peter</HTML>
Re: Valve gears
Posted by: Peter Heid (IP Logged)
Date: December 23, 2002 03:02PM
<HTML>The book "Model Locomotive Valve Gears" 1962-1981 by Martin Evans is a good book for those interested in the design of valve gear. It is quite thourogh and has more than 60 diagrams in the 100 plus pages. All the regular valve gear is listed as well as Cossart, Caprotti, Lentz, Gresley, Baguley, beames and more. A well done work and a good one for the shelf.
Peter Heid</HTML>
Peter Heid</HTML>
Re: Valve gears
Posted by: Peter Heid (IP Logged)
Date: December 26, 2002 04:38PM
<HTML>Another good book detailing many locomotive valve gears is: "Locomotive Valves & valve Gears" By C.S. Lake & A. Reidinger, 1951, Percival Marshall & Co LTD. This book goes into further detail of valve gears and valves than the model locomotive book. The 140 plus pages contain more than 120 illustrations and several pictures. This is a good reference work and belongs on the shelf.
Peter Heid</HTML>
Peter Heid</HTML>
Re: Valve gears
Posted by: David K Nergaard (IP Logged)
Date: December 26, 2002 11:06PM
<HTML>Peter, thanks for the heads up. Any idea where i can get a copy? If push comes to shove, I would even ante up for a Xerograph.</HTML>
Re: Valve gears
Posted by: Peter Heid (IP Logged)
Date: December 27, 2002 01:49PM
<HTML>Dave,
Many book services like abe, biblion and albris have extensive listings and are likely to have a source for these books.
Peter Heid</HTML>
Many book services like abe, biblion and albris have extensive listings and are likely to have a source for these books.
Peter Heid</HTML>
Re: Valve gears
Posted by: David K Nergaard (IP Logged)
Date: February 12, 2003 01:20PM
<HTML>I have just learned that many British Steam Lorries used poppet valve engines in the 1920s and '30s. Do any of you have details of their valve gears? The book I have been reading has tantalizingly inadequate illustrations.</HTML>
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