A new engine for fall---

[Art K]

Brian,
I must say when I replied in my thread this last iteration of your design is more in line with what I thought of as conventional. You just need a few holes for tappets or something.....
Art

[ogaryd]

Hi Brian, I believe your latest design would work fine with the cam mounted in the crankcase and the tappets mushroomed shaped installed from inside the crankcase.                       Gary

[Brian Rupnow]

After having a look at the Val, an engine designed by Brian Fairey, and seeing how his head bolts held the head and the cylinder  to the top of the crankcase, I thought YES---why not!!!  This somewhat lessons the complexity of the cylinder shape, but even more importantly, it opens up a clearance directly below the valves, allowing room for the tappets. Not much room, mind you, but if I followed someones advice about mushroom headed tappets I might be able to make something work here.

[Brian Rupnow]

It may not be impossible to have a side valve engine with dual independent cams machined from barstock, but it's damn difficult!! This configuration looks interesting.

[tangler]

Well, that has a familiar look about it!  It can't be that difficult   

Rod

[Roger B]

You could use some form of rocker to bring the valves closer together. If this was mounted on an eccentric pivot it would also solve the valve clearance (lash) adjustment issues.

[cfellows]

Chuck--Since you have already posted some good pictures of side valve engines, I am going to ask this question here as well as in its own separate thread. 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

Brian, I don't think there is a cast iron liner through both pieces.  The piston could have a slightly smaller diameter above the ring gland and extend up far enough to travel up into the head.  The top part doesn't have to even touch the cylinder wall, it just needs to take up space to increase the compression ratio.  On the other hand, it might not even be necessary.  My little vertical single engine with a 7/8" bore only has a compression ratio of 3.5 : 1 and it runs pretty good.  It has a 1.25" stroke and the piston stops 1/2" from the top of the cylinder at TDC.

Chuck

[Brian Rupnow]

Thanks chuck--any information is good information, and I know you have just built your engine recently.---I will go right now and have another look at it.----Brian

[Jasonb]

Another way to bring the valves closer would be to have a wider gear on the crankshaft and then the two cam gears could be staggered so thay can overlap. Also do you need such large gears, if the end of the crankshaft were reduced in dia then the pinion could be smaller and therefore the two cam gears.

J

[JMcRae]

I have a Honda g31 engine that uses one cam lobe for both valves, they use an
"L" shaped rocker on either side of the cam works slick.

[b.lindsey]

Brian, your lattest drawings remind me so much of the Briggs engine valve arrangement though there, the junction between the tappets (inside the crankcase) and the valve stems was not open but enclosed in a small chamber presumably to get a bit of splash lubrication from the crankcase. While the springs and retainers were also a tight fit, it was do-able just as it had been done in the prototype. Perhaps the attached cross section views may help in some way.

Bill

[Brian Rupnow]

Jason--That is a very novel idea about staggering and overlapping the cam gears. I really like that. And yes, I could probably reduce the crankshaft and cam gears by going to a 3/8" diameter on that end of the two piece crankshaft. I would still keep the other side of the crankshaft at 1/2" diameter simply because it would have to take all of the con rod torque and support a flywheel.

[Brian Rupnow]

Brian, your lattest drawings remind me so much of the Briggs engine valve arrangement though there, the junction between the tappets (inside the crankcase) and the valve stems was not open but enclosed in a small chamber presumably to get a bit of splash lubrication from the crankcase. While the springs and retainers were also a tight fit, it was do-able just as it had been done in the prototype. Perhaps the attached cross section views may help in some way.

Bill

Bill--That's marvelous!! I had forgotten that you built that model. Do you have a set of drawings available for that? I would love to see how you handled the cylinder fabrication/machining.---Brian

[Brian Rupnow]

Bill and Jason--Here's a quick question. If I machine the cylinder/combustion chamber from one piece of aluminum and put a cast iron liner in it as seen in the section model, then the cylinder head will bear on the top of the liner everywhere but in the actual valve space/combustion chamber area. Is this okay, or will there be issues of combustion gasses leaking down between the liner and the cylinder.---Brian

[Jasonb]

If the top of the liner lip and the top of the cylinder as perfectly level I don't see an issue. Maybe press or loctite teh liner into the cylinder and then take a finishing skim over the two.

J