Model Engine Maker
Help! => Specific Engine Help => Topic started by: Brian Rupnow on July 22, 2014, 05:44:40 PM
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I have a question about side valve engines. I have looked at a number of pictures of side valve engines, and they seem to fall into two categories. One is as per the Philip Duclos Gearless engine, where the cylinder is a plain bore separate part and the combustion chamber is actually in the head, which bolts to the top of the cylinder. The valve cages, seats, and housings bolt onto the outside of the head and are connected to the combustion chamber in the head through passages drilled through the sides of the head. The piston does not travel up into the head, but stops flush with the top of the cylinder.
T he other type, (and I'm really not sure about this) seem to have a plain bore cylinder, then a separate piece with the combustion chamber and valves buried in it bolted to the top of the cylinder, and then a flat, rather featureless (except for sparkplug hole and cooling fins) head bolted to the top of this intermediate piece.
It kind of LOOKS like the piston would have to travel up part way into this intermediate piece, but I just can't imagine a bolted joint that the piston and rings would have to travel over. (see picture) ----Or--is it possible that there is a cast iron liner that fits down through the intermediate piece and the cylinder so the piston can travel all the way without passing over a joint? Who can set me straight on this.----Brian
(http://i307.photobucket.com/albums/nn294/BrianRupnow/BrianRupnow015/sidevalveengine001_zpscd16662f.jpg) (http://s307.photobucket.com/user/BrianRupnow/media/BrianRupnow015/sidevalveengine001_zpscd16662f.jpg.html)
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Would a look inside Rod's engine help
http://www.modelenginemaker.com/index.php?topic=3573.msg63762#msg63762
I would assume the "intermediate piece" as you call it also has a skirt that fits down into the crankcase and this forms a one piece bore all the way through from the crankcase in much the same way as a lot of the compression diesels do.
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Jason--It appears to me that the cylinder and the portion directly above it which contains the valves are all machined from the same block of metal.
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Yes I was editing mine as you posted, the valve block, intermediate and skirts are all one on these type of engines.
I'm sure when Rod sees this post he wil add the cross sectional drawing, its on teh forum somewhere I think.
J
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Your wish, oh masters.......
(http://i104.photobucket.com/albums/m180/rod_sally/SCAUPcs_zpsf42efb71.jpg)
HTH
Rod
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One of the things that attracted me to this style of side valve design was having the valve seats and guides cut directly in the steel body rather than having bronze inserts in aluminium. It was also rather neat having the valve gear at the rear of the engine, although obviously this only works with a single. For a slim installation the carb and/or exhaust could be mounted at the rear rather than the sides.
Cheers,
Rod
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Thank you Tangler. I like that. I would like to do much the same thing, only perhaps I would make the round cylinder and the part directly above it which contains the valves from aluminum in two separate pieces, and put in a cast iron liner similar to Malcolm Stride's engines so the piston wouldn't have to slide over a gap between the two different parts. I like to make the valve cages a separate item, that way if I mess one up I can replace it without replacing the entire cylinder. I will have to think on this.---Brian
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The only major difference I see between the engine in this link that DP posted and the engine I might consider building is that on this engine the round cylinder and the part directly above it which houses the valves is all whittled from one solid chunk. I could do that--but it would be a bit of a pig to cut the cooling fins on.--Wouldn't be able to use the lathe.--At least not on the part above the round cylinder.--Of course the round part of the cylinder is down towards the bottom of the piston skirt, so probably doesn't need fins on it anyways.
https://www.flickr.com/photos/15794235@N06/5245356917/ (https://www.flickr.com/photos/15794235@N06/5245356917/)
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There is something rather intriguing about Tangler's design. If I gave up on the idea of a gearless engine, and made one very similar to Tangler's I see the possibility of two different types of valving systems with interchange of only the cylinder head----perhaps. I like a slower running engine than Tangler's, which appears in the video to be fairly high speed. I like my many hit and miss engines which have a cam operated exhaust valve and an atmospheric intake valve. If I was to build an engine similar to Tanglers with two cams driven by two separate gears, then I could have an engine where both valves are cam operated independently of each other. With no modifications to the main cylinder body, if the intake valve and spring were left in place to "plug the hole", and the cam/gear were removed, I could make up a different head. The different head would have an atmospheric intake valve mounted in it, with a sub manifold to mount the carburetor on. God alone knows why I would want to do that, but it does give the option of two very different engines with the modification of only the cylinder head.
http://i104.photobucket.com/albums/m180/rod_sally/SCAUPStotal_zpsa2cef6ea.jpg
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Tangler--What was the bore and stroke on your engine?---Brian
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Hi Brian,
Bore is 1.0" and stroke is 0.9". It was designed to be high revving, hence the over square design. A longer stroke engine would, I think, have a better slow speed behavior.
Cheers,
rod
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Thank you, Tangler.---Brian
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Your wish, oh masters.......
(http://i104.photobucket.com/albums/m180/rod_sally/SCAUPcs_zpsf42efb71.jpg)
HTH
Rod
Looking at that drawing makes me wonder if it would be feasible to take some of my older pylon-race engines and convert them to side-valve 4-strokes. The crankcase castings and crankshaft are already the right configuration (the crankpins have a spiggot to drive a disk or drum valve which could just as easily drive a cam gear - I'd need to make the cams, drive gears, followers and valves, with a new backplate/camcase assembly, plus a new cylinder head and new piston/liner/rod assemblies. The new piston/liner assemblies would be needed because the existing (2-stroke) ones have ports in them and and the new rod would be needed to move the piston up the bore so that it's flush with the top of the flange at TDC (they're currently about 1/4" sub-flush to accomodate a head-button). It all looks do-able.
In fact I'm wondering if I could actually get away with just sleeving a 2-stroke liner (to close the ports) or even just filling the ports in the crankcase, and then using the existing pistons and liners. They're ringless "ABC" designs with tapered bores, and I have access to an engis lap of the right size that would allow me to ease the bore sufficiently to move the pinch point to the top of the cylinder - I'd just need to make a new (longer) rod. I'm also wondering if I could make a 4-stroke diesel out of one of them. I probably have nearly a dozen obsolete donor-engines of perhaps three different types, plus boxes of spares (including unused piston/liner sets), so there's scope for making lots of mistakes!
When I get my workshop back up and running I may be wanting a chat with you, Rod...
AS
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Tangler--Forgive me for asking so many questions please. That engine looks like it would have real problems with the cooling, if it were not equipped with a propeller blowing a fresh stream of air over it as it ran. Am I correct in this assumption?---Brian
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Brian, no problem at all - fire away. Always ready to talk, that includes you AS :)
The engine is designed to be air cooled. I've seen no issues with over heating, so my smooth cylinder head appears to be adequate. I've got one of these infra-red non contact pyrometers - I must take some measurements the next time I run the thing. Bear in mind that this is a methanol fuelled glow engine which I believe will run cooler than a petrol (gas) engine. I would go for water cooling with a stationary or marine installation. Hydroplane engines, which were one of Westbury's great interests, tended to be air cooled but they were whizzing along at 80+mph with their cylinders in the (damp) slipstream.
Cheers,
Rod
Addendum: It's never really occured to me before but it would be straightforward to convert the design to an OHV with pushrods and a new head. It would be interesting to test the power difference....
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Maybe I wasn't clear in what I asked you. When you run that engine with a prop on it as it appears in your video, there would be a lot of air flowing across it to cool it. If you ran it WITHOUT the prop on it, I am assuming it would overheat very fast. Have you ran it for any periods of time without the prop. I am going to assume that it is like the Nemett Lynx and Bobcat---Great as an air cooled engine when ran with a prop, but if ran without a prop would probably need to either have the cylinder water cooled or have an auxiliary fan mounted blowing over the fins as I did on my recent build.
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Brian,
I've never run it without a prop - I would expect it overheat. The finning on the cylinder is rudimentary and there is no finning on the cylinder head. If you have a look at the engines that are made for model helicopters or cars you can see some of the arrangements that are made for enclosed engines but all this is beyond my ken.
Cheers,
Rod
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Addendum: It's never really occured to me before but it would be straightforward to convert the design to an OHV with pushrods and a new head. It would be interesting to test the power difference....
Thinking that one through you could also replace the gears with a toothed belt and sprockets (or put some intermediate idler gears in there) and make SOHC and DOHC configurations as well. Or even a Cross rotary valve (belt drive or with idler gears). Or if you really wanted to be different the same basic layout could be given bevel gears and a vertical shaft to drive either a vertical rotary valve or an Aspen valve. In fact I think the only configuration that would be difficult would be a sleeve valve.
Have you considered an opposed-piston variant? :LittleDevil:
AS