The Steamboating Forum

Hello, my name is Martyn and I have just started to commission a Gordon Cheape 2 1/2 + 5 x 3 compound launch engine. I am not a steam boater as my interest is really locomotives. However a member of our club had given up on trying to make this engine work and wanted rid of it. It is brand new and beautifully made with Joy valve gear, BUT I know nothing about compound engines.
I would love to get this engine working so that it can be used by one of you boaters, if that is the right expression.
So my questions are: have any of you made one of these engines? were there any problems and are there any tricks to making it run properly?
To show my ignorance there seems to be an air pump driven by belt from the crankshaft. What is it for?
I hope to get this finished by the spring of next year to take to the festival on the river Wey at Guildford, so any help or advice would be gratefully received.
Martyn Harrold

"It is brand new and beautifully made with Joy valve gear, BUT I know nothing about compound engines."

Joy valve gear was used in England locomotives, and it provides good sorting of valve events, and was therefore popular for a time around the late 1800s to early 1900s. A compound engine uses two cylinders, the high pressure cylinder works between main steam pressure and exhausts to an intermediate pressure, about half way between main steam pressure and exhaust pressure. The steam then passes to the low pressure cylinder, where additional power is produced, then to exhaust. Dividing the steam expansion between two cylinders reduces the temperature differentials between the cylinder and the steam, and thus reduces initial cylinder condensation. A big efficiency gain is possible with compound engines.

I have made small engines with Joy valve gear, and there are no serious complications, if proper plans are available. Free-lancing this type of valve gear is risky, so please let us know what details you have. Many on this forum will be happy to help with your potential problems. Post some pictures please.

"are there any tricks to making it (Joy Valve Gear Engine) run properly?"

Adjusting Joy valve gear does not lend itself to conventional valve diagram setups, but it is not too challenging, so long as you have the critical dimensions of the links and the valve dimensions. Often one finds slide valve dimensions here that are not symmetrical, the head end valve dimensions are different from the crank end, etc. It can be worked out OK, and we can help here.

"seems to be an air pump driven by belt from the crankshaft. What is it for?"

Boats ans ships, having an infinite source of cooling water, can take advantage of having a vacuum during the exhaust stroke of the engine by using a steam condenser. The condenser is capable of creating high vacuum conditions, and thus more output power. Condensers are also necessary when operating in sea water, as sea water is terrible for boiler feed..Therefore the exhaust steam, condensed back into pure water, can be used over and over again as feedwater. Valve stem and piston rod packings will leak air into the condenser, destroying the vacuum. So the air pump withdraws the air that leaks into the system, maintaining a steady vacuum. Often the "Air Pump" is called a "Wet Air Pump", as it not only draws air out of the condenser, it also handles the condensed steam (water), pumping the water out of the vacuum space, and into an atmospheric storage tank where it will eventually be fed back into the boiler. More on this later.

Martyn Harrold, you have come to the right place for help on this subject.

Fred, most of the George England locomotives had Stevenson link valve gear, and I'm not aware of any of them having Joy gear, though I could be wrong. If you meant English locomotives, then yes certainly, Joy gear was used in England a fair bit by several locomotive builders in the mid 19th Century through to the early 20th.

A possible source of up-to-date information might be the Boston Lodge works of the Festiniog Railway, who built a replica L&B Manning Wardle locomotive (Lyd) with Joy gear maybe 5 years ago. I understand the Joy gear was thoroughly CAD modelled, but even so it needed modifying to get best performance. The Lynton and Barnstaple railway have just announced the commencement of two more Manning Wardles
to work their planned reinstatement of a lot more railway, and if they give the same level of study to them as they did to their new Baldwin replica (Lyn), then I'll bet they are the current world experts on Joy gear.

In current UK steamboats both Joy and the similar Marshall gears are unusual, but not vanishingly so, though I gather Marshall gear is fairly common on steam traction engines; some would say they are both developments of Hackworth gear, which I think just about pre-dates Stevenson link. The advantage of the gear in a steamboat is that you can put the steam valves alongside the main cylinders rather than in line with them, and you end up with a very compact engine; the increased sideways projection is not huge. As far as I can see, the main snag is that adjusting the gear after the first run is difficult, and let's say a lot of work using temporary lash-ups is worth while before finalising the geometry on the actual engine. Chris Way from near Norwich currently has a 21' Frolic steaming, with a twin engine using radial valve gear - I think it may be Marshall rather than Joy, but I'm sure Chris would tell all if contacted via the SBA. I can help with that if need be.

I can remember who it was, ( I think it may be in the section on engines in the SBA handbook), but one comment was that the link from the con rod must be horizontal with the piston at mid travel, but I wouldn't take that as gospel without checking.

Gordon Cheape engines are a copy of the Savery compound and use "savery" gear, this is a version of Joy gear but uses swing links instead of the usual curved slide blocks. Below is a photo of a Savery compound, one of the last to be made (1912).
Regards
Jack

Thank you so much for the feedback. I will take some photographs on Saturday and post them here so that you can all see what I have bought. Martyn

I have taken some photographs of the engine to show you were I have got to. I have reassembled it with the parts that I have but there are questions remaining. For example there are tapped holes in the baseplate in two flanges but there is nothing to fit there.
It seems that I can only attach 3 photos. Is this right or am I doing something wrong?

Here are a couple more. You can see that the steam is connected to the top of the high pressure piston valve which I find unusual but is as Gordon Cheape drew it. I have not tried to run the engine yet as the parts are only loosely connected but the previous owner said that it owner dais that it did 3/4 of a turn and locked up and the when the valve gear was put into reverse it did 3/4 turn and locked up again.
I have added a couple more photos.
Martyn

Martyn39 wrote: ↑

Sun Sep 23, 2018 9:41 am

... the previous owner said that it owner dais that it did 3/4 of a turn and locked up and the when the valve gear was put into reverse it did 3/4 turn and locked up again.

This may be teaching grandmothers to suck eggs, but that can be exactly what happens if condensation has not been fully cleared from the cylinders, and some engines require several goes in forward and reverse gear alternately with the drain cocks open before they will run properly. With other engines, warming through with the drain cocks open is enough to blow condensation water out of the cylinders, but it doesn't always work that way.

I can't actually see any drain cocks at all, but that may be my eyes and the way the photographs are taken. The engine certainly needs them.

It has only been run on compressed air so far. There are 4 tapped holes in the cylinders and I have just ordered 4 pressure gauges to fit in these to give me a clue as to what is happening.
Martyn

Hi Martyn,

There are 4 tapped holes in the cylinders and I have just ordered 4 pressure gauges to fit in these to give me a clue as to what is happening.

because your engine has piston valves you need drain cocks. In the tapped holes you have to mount the drain cocks. If you fit there pressure gauges you could destroy them.

Best Dietrich