Sidevalve single

[ownthesky2010]

Hi All
First engine build here and I'm hoping for some advice from the experts.
I have just finished an own designed sidevalve single around 11cc. So far it starts very easily and turns a 12.5x6 at 7000rpm but I'm struggling to get it running smoothly and it feels like its got a bit more to give. I suspect its a mixture issue. I have tried 2 completely different carbs without success but I don't have any idea what size carb bore I should use. I initially used a twin needle carb with a 7.5mm bore. If the throttle was opened all the way it would rev up and then die like its not drawing fuel and it would reach peak rpm before fully open. Even with the needle valve completely open a pinch test showed it was lean. I then tried a single needle carb with a bore of 6.5mm and could not get to the same top rpm at any needle valve setting. I can lean it out with the needle till it gets peak rpm and if I go any further it dies yet when the tank runs out it smoothes out and runs best for a couple of seconds.
I have also noticed a loss of power when the glow driver is removed at any rpm.
My plan is to refine the design and build some multi cylinder engines. I might even sell some. I just need good reliable performance.
The full spec of the motor is:
Bore: 24.65mm
Stroke: 24.00mm
Compression: 9/1
Valve lift: 1.9mm
Ex open: 61 deg BBDC
Ex close: 31 deg ATDC
In open: 25 deg BTDC
In close: 67 deg ABDC
Glow plug: OS F-type
Glow plug location: Bore centre
The main variables that I think need looking at are the compression ratio, Glow plug location and carb type/diameter but I could be completely wrong.
Any advice would be very welcome.

 

[canadianhorsepower]

That cam timing is pretty wild for a single cylinder
and I would increase the lift and reduce compression to 6/1

 

[ownthesky2010]

Thanks for that mate
I got the timing from this useful table I found somewhere on the internet.
I may be able to increase valve lift. The limiting factor in this case is maintaining tangential contact between the cam and the followers. There is limited space for the cam followers so they are 5mm diameter and I had to profile the lobes accordingly.
Reducing the compression would be easy. Would that also need a smaller carb bore to draw fuel correctly?

 

[ownthesky2010]

Thanks for that mate
I got the timing from this useful table I found somewhere on the internet.
I may be able to increase valve lift. The limiting factor in this case is maintaining tangential contact between the cam and the followers. There is limited space for the cam followers so they are 5mm diameter and I had to profile the lobes accordingly.
Reducing the compression would be easy. Would that also need a smaller carb bore to draw fuel correctly?

 

[Chiptosser]

Are you able to create enough flow through the intake tract? Ample fill rate?
It looks like a mighty small intake valve, along with the long intake tract compared to the displacement. Just my general observation.

 

[Chiptosser]

Could you supply a couple of different views of the cylinder?
From the port side at different angles?
And a closer view of the top of the cylinder?

Thank You.

 

[ownthesky2010]

Thanks for that mate.
Here are the pics as requested.
I included a pic of the combustion chamber in the head.
I think it needs opening up to improve flow and reduce compression.

 

[canadianhorsepower]

Thanks for that mate
I got the timing from this useful table I found somewhere on the internet.
I may be able to increase valve lift. Reducing the compression would be easy. Would that also need a smaller carb bore to draw fuel correctly?

close your exaust valve 36 to 42 after tdc
use the same carb
relocate your spark plug over your valve thats were your combustion chamber is.

good luck

 

[Brian Rupnow]

Parts of your design look very familiar. Are you running dual independent camshafts, each with their own dedicated gear, and a third gear on the end of the crankshaft?-----Brian

 

[ownthesky2010]

Thanks for the advice. I will make a new head with the plug between the valves and a bigger chamber for better flow and lower compression.
I will have to make a new cam to alter exhaust timing unless I can move the gear round by 1 tooth. Its 26t 0.6mod.
The design is similar to a few commercial engines like Vega and Laser but I put the cams in a separate module that can be removed without altering the timing.

 

[Niels Abildgaard]

Can we see a drawing?
My fingers itch to make it into something just as outmoded, but never tried before.Two stroke with cam on crank and one side mounted exhaust valve.

 

[Art K]

I won't get into Cam timing but I will make a suggestion to help flow. Take a die grinder or some files and clean up some of the sharp edges in the intake & exhaust passages. That should help flow a bit. Otherwise I would say that is quite an engine you've made. Very clever design.
Art

 

[ownthesky2010]

Sorry Niels.
I dont have anything as organised as a proper set of plans. If you want I can post a bunch of photos of the parts.
Your 2 stroke idea is very interesting. I wonder how the cam and valvegear would cope at engine rpm.
Art thanks for the advice and kind words. I have posted a vid of the engine running if you want to see.
[ame]https://www.youtube.com/watch?v=dG1SIgQecE0&feature=youtu.be[/ame]
My daughter just told me I should have picked up the dog poop first but excitement got the better of me.

 

[petertha]

Cool engine. I'd love to see some build pics if you ever consider posting.

Re your Excel table attachment, first I thought it looked familiar. But the engines are different than what I cobbled together from old Clarence Lee book + some Strictly IC mag designs. I thought I did a more detailed summary inclusive of more recent engines, but cant find it just now. Maybe do a search here on the forum for similar posts, topic gets discussed a lot. You didn't mention fuel type (nitro & oil content) but guessing typical glow fuel?

Anyway, here is some additional info FWIW. By eyeball, I think it agrees quite close with your reference data of commercial glow engines. Maybe consider the established averages & ranges before making radical changes based on well meaning, helpful advice. (btw Orange shade = glow engines, Blue shade = gasoline, Green is the Malcolm Stride book which I'm not sure how he derived but it gets referenced).

 

[petertha]

..and some more info on compression ratio's. The same caveats apply.

 

[petertha]

.. some valve lift information from the deep bowels of my hard drive Take this FWIW, probably did it when I should have been sleeping. Note the comparative metric to valve diameter, found that rather interesting.

 

[Niels Abildgaard]

A german mr Schillings made a 10 ccm overhead camshafts fourstroke-engine that did 28000 rpm easily in 1973.A crank-cam will not be the limit for doing 14000 rpm in a side exhaust valve two-stroke.If 7000 rpm is the goal for propeller reason some very sharp opening ramp can be made.
For ease of experiment valve will be behind cylinder as in Your engine and cam sitting on a loose-follower crank.This loose followercrank can also be host to a Zimmerman rotating inlet disc valve.
I will start Cubifying after breakfast.
20 mm bore30 mm stroke.
V90 degree common crank volume twin.
8-10 mm exhaust vaves
Utterly useless but different.

 

[ownthesky2010]

Peter thats fantastic info. I wish I had that 3 months ago.
I will put up some pics of individual parts soon but at the moment we have all the family around.
Niels Im looking forward to seeing more of that 2 stroke idea. Have you considered desmodromic valves.
Otherwise I think you might need some serious valve springs.
Besides, it would be unspeakably cool.

 

[Niels Abildgaard]

Hello Own the Sky
A Young fellow tolerating the fantasies of an old man.
By the way ,please put something about Yourself,background,location ,lathe etc.
First picture show a maybe possible side valve scheme.Next one my favourite
Side valves can be faster and the top thing have better flow coefficients.

 

[ownthesky2010]

My name is Richard and I live in Yorkshire England.
I have a Chinese lathe that's manual feed only and an Emco pcmill 50 milling machine with mach3.
I do most of my turning on the mill with the stock in the spindle and the tools in a homemade tool holder in the vice.
I recently built a 4th axis for the mill to cut gears.
My background is engineering and cnc programming.
I am approximately 37 years old (not sure exactly) and I have been interested in model engine my whole life.