My Two Cylinder Design - Feedback welcome

[Goldflash]

Considerations. Side Valve engines. Side valve engines run hot in the region of the exhaust port which in the case of a side valve engine is in the cylinder block.
cooling in this region is very important. Therefore you should consider having water cooling in the cylinder block and using cast iron or good quality steel sleeves.
The cylinder heads would most probably work ok without water cooling as long as they had well machined fins as most of the heat generated in the combustion process is going out the exhaust port.
I would not try to go over a compression ratio of 6.5 to 1 as side valves can actually be choked by excessive compression ratio. Good breathing and gas flow is more important to get good performance.
Had a bit of experience with tuned Side Valve V twins ( Indian ) and you can actually be quite radical on cam timing and valve lift.

 

[Hopper]

I would not go much over 6:1 compression on a flathead. Less than that and the restriction to breathing in the area between the valves and the bore outweighs the performance gain of the higher compression.

If you want ideas on tuning/designing flatheads, Google "Harley KR". Harley had the 750cc KR flathead racer lapping Daytona at 150mph in 1968.
An outfit called Victory Library sells some excellent publications on tuning up old flatties. Lots of good info on combustion chamber design (very critical in these engines) and cam timing.
Another website called the Beauty of Speed has some good flathead info too. As does KRXLRTT.COM

If you use the 90-degree offset crankpins (ie a 270 degree crank) it gives a loverly loping v-twin exhaust note due to the uneven firing intervals, as well as running smoother.
Triumph is doing this with some of its new twins (the America model I think), and Yamaha did it with the TDM800 I think, and Laverda sometime in the 90s. Lot of guys doing it to Nortons in the classic race scene these days.

 

[Goldflash]

Triumph TRW 500 CC Twin Side Valve. Made for the British army.

 

[Rivergypsy]

Just going back to the 3D printing comments, there is a print material suitable for using for lost wax casting IIRC. I've also got some info from Objet on how to do this at work, so I'll try and remember to difg it out and post it when I get back there on Monday.

Looking forward to seeing how you go with this - good luck!

 

[smpstech]

OK so a few updates.

I lowered the compression by cleaning up the combustion chamber design. It sits at about 5.5:1 now. I hope this will also help reduce the heat generated by combustion a bit.

The camshaft profile has been changed. It now has a 240 degree duration, as per stevehucks suggestion, and I also fattened up the nose a bit.

Regarding the engine block cooling. Unfortunately, I do not have much room to allow for water jackets inside sleeves. The hottest side of the engine block will be the side with the ports on it as that is where the exhaust gases will be passing through. I plan on making the valve chest cover and intake/exhaust manifold as one piece and will act as a heat spreader and heat sink as it will have fins machined into it. on the opposite side of the engine where the cut out is, I may not cut that piece out entirely and instead opt for fins there too.

 

[ShedBoy]

There is nothing wrong with a 180 deg. crank on a parallel twin. The Honda CB350 had one and nobody can argue that it was not good running machine. No doubt there were other motorcycles, that used that set-up, but I don't have personal knowledge of which ones did.

RWO

Didn't say there was anything wrong with them just that other types are smoother. Not trying to take anything from a 180° crank.
Up until about the mid 90's most parallel twins were 180°.

Brock

 

[stevehuckss396]

Looks great! When are we going to start building.

 

[Art K]

Steve,
If you're not careful you will have the engine built before smpstech starts on his.
Art

 

[neseng]

.......A bit larger all round but similar to your design ideas in some ways. It is a side valve, air cooled, 10 hp, twin cylinder, 360 deg, 3 bearing crank, petrol fueled, magneto ignition, 6:1 compression ratio. Bore 85mm, stroke 82.5mm, 468 cc per cylinder, ign 12 deg BTDC, inlet valve 6 deg before TDC to 30 deg after BDC, exhaust valve 41 deg before TDC to 19 deg after BDC. There you go, you can chew on those figures for a while!

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Cheers, neseng

 

[smpstech]

Steve,
If you're not careful you will have the engine built before smpstech starts on his.
Art

Ha, probably. Machining begins in September is all goes well.

 

[Goldflash]

Have a look at the Westbury Seagull 10 CC side valve twin on the web site below it should give you some ideas

http://www.modelenginenews.org/etw/seagull/

 

[stevehuckss396]

Steve,
If you're not careful you will have the engine built before smpstech starts on his.
Art

I think it's kind of cool. I would build one.

 

[Hopper]

Some interesting stuff on flathead cam tuning here:
http://www.harleykrxlrtt.com/technical_info_on_kr_cams.htm

And the ultimate combustion chamber design is probably this:
http://www.harleykrxlrtt.com/images/01p-1965-krtt-head-barrel-2.jpg

 

[smpstech]

Just going back to the 3D printing comments, there is a print material suitable for using for lost wax casting IIRC. I've also got some info from Objet on how to do this at work, so I'll try and remember to difg it out and post it when I get back there on Monday.

Looking forward to seeing how you go with this - good luck!

Apparently PLA plastic will work, which is pretty much the standard filament used by most consumer 3d printers. It has the lowest melting point and is the cheapest, so it makes sense and sounds like something that might be worth looking into in the future.

 

[Metal_slicer]

smpstech,

I love the design! I have been trying to design a simple 2 cyliner engine with the exact dimensions you have. A 2" x 2" x 2.5" block of aluminum. This is a good size for my Sherline mill. Seems I always start to run out of room for the valves and intake and exhaust ports. I like the simple approach of having the cam on the side vs having it overhead.

Any latest images of your design?

 

[smpstech]

That is indeed why I went with the flathead engine design. I wanted an engine that will be able to be ran for long periods of time, possibly at higher RPMs and with a load so cooling and lubrication were key points. With all the valve train in the block and open to the oil pan with splash lubrication, almost everything that needs lubrication is at the bottom where the connecting rods can fling oil around. The valves in the block mean there is just so much more room for the spark plug and larger valves as well as having more material around everything for greater strength.

And as for the design, it is largely unchanged. Hopefully I can get the first chips flying in about a week or so. I am still wrestling with the block cooling, I may use coolant passages, but was thinking of a aluminum intake manifold/valvechest cover that would act as a heatsink for the hotter side of the block. The exhaust manifold would most likely have to be steel to sustain longer run times. If it was a piece of the "dual purpose cover" it would transfer more heat into it which is kind of the opposite of what I want to do.

 

[gus]

Sad. Lister and Petters Plants are no more in existence. Used both to power air compressors.
Lister engines run forever.