Gordon Cheape Compound

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marinesteam
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Re: Gordon Cheape Compound

Post by marinesteam » Wed Nov 14, 2018 3:30 pm

Wes is describing the leading or trailing edge if the same blade. The leading edge is the one furthest away, right side of blade, RH prop

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Re: Gordon Cheape Compound

Post by Lopez Mike » Thu Nov 15, 2018 4:00 am

Ah. So obvious that I didn't get it.

Sort of reminds me of messing about with my fellow students in drafting class once long, long ago. Eighth grade maybe? I held up a french curve drafting aid and said, "Look at that! A horizontal line is tangent to the bottom of the curve." Much looking wise on the part of the group. Of course it's tangent. Any curve has a horizontal tangent.

I'm rather fond of my theory of the arithmetic of intelligence. I was once informed by my grandmother that two half wits added up to a whole wit. I accepted that for many years until I entered the job market. It was immediately obvious that intelligence multiplies rather than adds. Since none of us are playing with a full deck even though we sometimes come close, it follows that multiplying any two numbers that are less than one produces a smaller product than either number. Two half wits equals a quarter wit. Thus committee meetings are always a disaster. With five half wits around a table the group intelligence is undetectably small.

Now back to Gordon Cheape Compounds. Sorry about the thread hijack.
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Re: Gordon Cheape Compound

Post by DetroiTug » Thu Nov 15, 2018 10:01 pm

Easy way to tell which rotation a prop is: Lay it on a table with one blade at 12:00, if the right side of that blade is touching it's right hand, if the left side is touching, it's left hand.

-Ron
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a right handed prop

Post by dampfspieler » Fri Nov 16, 2018 6:41 am

Here you can see my right handed prop.

Image

[Youtube]https://youtu.be/AtfhxuNwAXM[/Youtube]

Here you can see the engine with Joy-Valve-Gear Steam tug mayflower

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Re: Gordon Cheape Compound

Post by Martyn39 » Fri Nov 16, 2018 3:51 pm

Thanks Guys, I have optimised the engine for clockwise rotation when sitting at the back. Another point, the photo posted of a propeller shows the engine with a flywheel. Should my compound have a flywheel? As you will have seen from my initial photographs there is not enough length on the crankshaft to fit a flywheel. I looked at the Savery engine on youtube and that one seems to run ok without a flywheel.
Next question: are there any designs published for a condenser system that would suit this 7 HP engine? Is the condenser considered to be part of the engine or part of the boiler installation? When this is finished I don't really want to make a condenser but will if it is normal practice for the engine and condenser to be considered as a single item.
Thanks again,
Martyn
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Re: Gordon Cheape Compound

Post by DetroiTug » Fri Nov 16, 2018 9:29 pm

Quote: "Should my compound have a flywheel?"

It's not imperative, but it will run smoother with it. The prop directly coupled to the engine will act as a flywheel. Some engines just have a handwheel to get the engine off HP top dead center, if you have a simpling valve, then that is not necessary, but it's still good to have some means to manually turn the engine for setting valves etc. Twin simples do not need a flywheel at all for other than smoothness. A simpling valve (steam admitted on the LP as well) momentarily turns the compound in to a twin simple making it self starting.

Quote "Is the condenser considered to be part of the engine or part of the boiler installation? When this is finished I don't really want to make a condenser but will if it is normal practice for the engine and condenser to be considered as a single item."

I would say it is just part of the whole plant, the condensing portion of the steamplant. The boiler is the evaporator. The engine is the expander. The condenser is a component of the plant. I think the rest of the question is, does it need a condenser? On a compound, the LP likes a bit of vacuum, so yes it's a good idea to condense with a compound.

-Ron
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Re: Gordon Cheape Compound

Post by RGSP » Sat Nov 17, 2018 9:46 am

There are plenty of condenser designs that would work with your engine, and as Ron says, most compound engines do exhaust into a condenser because it significantly improves efficiency and power. You have the choice of a small, inboard, drum with multiple tubes connected to the exhaust line, and the water the boat floats in pumped past them: the Stuart Turner 6A normally has one of these, as do most Leak engines. OR you can use an external condenser of one or two 25mm copper tubes run just outside the boat's skin, parallel to the keel and most probably close it it, perhaps 3 or 4 feet long. Ideally the condensate should come from the condenser into the air/condensate pump quite hot: 70C or 80C which avoids energy loss from having to heat it again, and most people include a small storage tank known as the hot-well at this point, open to the atmosphere. However, it isn't critical, and if the condenser is oversized and cools the condensate too much, the efficiency drop will need careful measurements to detect.

The other major advantage of a condensing system in the UK is the ability to run the boat on salt water: most of us have access to rivers and lakes suitable for steamboats, but even more of us can easily get to salt water estuaries, which are often fine bits of water anyway, but have the further advantage of no expensive licenses or superfluous safety inspections (other than the essential one for the boiler). You could (of course) run a non-condensing engine on salt water, but a large water supply would be needed inside the boat, as in a steam locomotive tender, and most freshwater "puffers" take feed water straight from the river or lake after the initial fill (and sometimes for that too).
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Re: Gordon Cheape Compound

Post by Lopez Mike » Sun Nov 18, 2018 3:43 am

I don't have a high opinion of non-condensing power plants even on fresh water bodies. A boiler is essentially a distillation apparatus and is busy purifying the water as it passes through. The impurities remain in the boiler until somewhat removed by blowdown. If you wish to attempt to purify the lake, stream or canal that you navigate, good luck.

Having decent control over the pH and other properties of your boiler contents is also a worthwhile goal.

In addition, having a hot well allows you to regulate the level of your boiler water with a very simple float. You will have many more urgent things to do than fiddling with various valves when out steaming for the day. Like not hitting things and keeping particularly feckless passengers from touching hot and moving things and perhaps uncontrolled departures from the boat.
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Re: Gordon Cheape Compound

Post by Martyn39 » Sat Dec 01, 2018 10:57 am

We have spent quite a bit of time getting equal valve travels by machining a few thou off the back of the valve suspension, measuring then remachining until we got the right result and it now runs really well on air. The next task is to run it on steam and I am making a 4 way drain manifold system so there is only one control, which should be finished this week. Next up is the lubricator. Following advice given at the Midlands show I am experimenting with a lorry lubricator pump. These are really well made (in England) and very reasonably priced. This should be a simple quickly made fitting, just need to buy a couple of sprag clutches. The air pump is connected but I still have to design a linkage for driving the feed pump.
After that it will just be the cosmetics, i.e. lagging etc. What wood is commonly used? I have plenty of mahogany, ash, oak, elm or yew. I guess the banding would be in brass. Are there any tips for fitting the wood as it seems to be a very fiddly job that could look awful?
Thanks,
Martyn
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Re: Gordon Cheape Compound

Post by Lopez Mike » Sat Dec 01, 2018 1:54 pm

I would be very interested to see how you have arranged your cylinder drain system to use only one valve without having it flow from one end of the cylinder to the other when open. Check valves?
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