Sidevalve single

[Niels Abildgaard]

Hello Hopper
How big is such a Harley valve and how much mass.?
What rpm will engine do without valve trouble,dancing bouncing or not closing?
We can use Harley sidevalves as models for small SVmodels.A model valve half size can with tender,loving care run double rpm.(I think)

 

[ownthesky2010]

Thanks for all the help guys.
I finally got a run in today. It seems like 2 steps forward and 1 step back.
The plug location initially did not seem to make any difference until I leaned out the low speed needle and got a good transition.
Then it seemed best with plug over the exhaust valve but the difference was not large.
Still having issues with the carb. When I lean out the bottom end its too lean on the top and the high speed needle has no effect.
I suspect the lean running is what causes the drop in power when the plug isnt lit.
Must bear in mind that this carb is off a .60 2 stroke glow engine so Im not expecting it to be perfect.
The next thing on the list is an own designed air bleed carb. I will make it with two air bleed screws that open at different throttle positions.
WRT the combustion chamber shape, thanks for the info on the harley heads.
As soon as I have the fueling sorted out I will re-design the head.
I'm trying not to work with more than one variable at a time.
For the record todays run topped out at 8100rpm.
That's nearly 10% better than the last so there is definitely progress.

 

[canadianhorsepower]

Just curious are you using 4 stroke plug or two stroke

 

[ownthesky2010]

tried with hobbyking no3 and os f type.

 

[canadianhorsepower]

what size are your valve size
and are they angle are straight up

 

[ownthesky2010]

the valves are 10mm diameter and they are straight up.

 

[Niels Abildgaard]

For the record todays run topped out at 8100rpm.
That's nearly 10% better than the last so there is definitely progress.

Nope
Same prop ( ? ) going from 7000 to 8100 is more than 50% power gain and more than 33% torque gain.
Not bad I would say.

 

[ownthesky2010]

Ya Niels. Same 12.5 x 6 prop. I think it still has more to give.
I built it as a side valve with a roller bearing big end because I want to be able to push it to decent performance.

 

[canadianhorsepower]

the valves are 10mm diameter and they are straight up.

it's to late now but usualy you would incline the valve toward the cylinder
about 15 degree. It doesnt look like much but if you leave the bottom of your valve at the same place and move the top to acheive the 15 degree
it does relocate your combustion chamber more over your piston and really help cylinder scavenging

I would go with your 6.5mm carb it would have a better ventury effect with that size of valve and intake track lenght

cheers

 

[mu38&Bg#]

A carb for a 10cc two stroke is too large. The 6.5mm should be just about right for the amount of air your engine will flow. I don't have any figures for BMEP of model size side valves, but you're getting close to 80PSI, so there may not be much more power available. I wouldn't expect to exceed 9000RPM with that prop.

Did you make plug blanks for the extra glowplug holes?

Greg

 

[Niels Abildgaard]

Hello Richard

Have found a describtion of the first OS 60 OHV engine from the seventies and Yours is better. Astonishing with all that DOHC being better than SV etc.
The man who made the last and winning Aprilia 125 ccm two stroke says he will never make a single cylinder engine again without first order mass balance.
I cannot help feeling that a single mass balanced twostroke with a single Side valve for exhaust deserves a little CAD to compare mass etc.If I was to make a big fortune smaller by making modelaircraft engines,what 10 to 15 ccm fourstroke with spark ignition is the one to beat?My last model fourstroke book is from 1983?

 

[ownthesky2010]

Thanks Luc and Greg. I was thinking the same thing, albeit without the theory. Thats why I tried the smaller carb.
Im still not 100% convinced though because I had the best runs with the larger carb and had power all the way to the throttle stop.
Would it be a worthwhile test to make a carb body with the larger bore and multiple barrels with smaller bores to try.
It shouldnt too take long as I have a 4th axis on my mill.
I didnt make blanking plugs for the plug holes, I just lit the one I wanted to try. I have read up on a lot of forums and it seems they wont self ingite.
WRT further power increases, Im hoping to get a bit more by optimising the combustion chamber shape. Still havent done anything with it.
Neils you are way ahead of me, I dont have any model fourstroke books.
As far as I know the vast majority of model four strokes are glow powered but there is a bit of a move toward spark ignition with people doing their own conversions.
One of the reasons I put a roller bearing in the bottom end of mine is to try it on petrol with lower lubrication. I also supported the cams on ball bearings so the only sliding elements are the small end in sintered phosphor bronze/silver steel wrist pin and the cam/followers.
It was a bit of a pain to fit it all in but the end result is slightly smaller and the same weight as an old sc .60 2 stroke that I have lying around.
I would really like to see you do something with your idea. It sounds great.

 

[petertha]

.If I was to make a big fortune smaller by making modelaircraft engines,what 10 to 15 ccm fourstroke with spark ignition is the one to beat?

Sounds like the popular cliché:
Q) What investment will guarantee me a small fortune?
A) Start with a LARGE fortune & invest in Model Aviation!
<or substitute your 'investment' of choice.. race cars, fast women, cold fusion coffeemakers... >

I've been out of pattern since the 90's & they've predominantly gone electric, but I'd venture a guess YS is probably up there. Cant find referenced or measured HP ratings but maybe if guestimate from prop/rpm references.
http://www.ysengines.net/dz175cdi-dz175/
http://www.centralhobbies.com/Engines/parts/DZ175dz.html

 

[mu38&Bg#]

I didnt make blanking plugs for the plug holes, I just lit the one I wanted to try. I have read up on a lot of forums and it seems they wont self ingite.

The plugs certainly will self heat in a running cylinder. I would try again with blanks. Testing or tuning an engine with plug heat is only useful if you actually intend to use (fly) it that way.

Model engines can be profitable just like any other business, but competing with the Chinese imports would make it extremely difficult.

Currently, Saito produces the FG-14 and FG-17. They also make 11, 21, 30, 36, and 40cc four stroke single cylinder engines. OS produces 30 and 40cc four stroke singles. All of these will run on 5% oil, the larger engines slightly less.

YS does make the 175 and now 185 CDI. Those engines still burn methanol and require a minimum of 20% oil in the fuel. I converted an old FZ-91 to gas and spark, but have only a few minutes of run time on it.

Greg

 

[Hopper]

Hello Hopper
How big is such a Harley valve and how much mass.?
What rpm will engine do without valve trouble,dancing bouncing or not closing?
We can use Harley sidevalves as models for small SVmodels.A model valve half size can with tender,loving care run double rpm.(I think)
__________________
Kind regards

Niels

Niels, they were a 750cc twin, running about 6:1 compression and were spinning at 8,000rpm in later days and developing some 55-65hp.

 

[Niels Abildgaard]

Hello Hopper

It is always easier to tell other people how to design things than doing something usefull meself.
And I do not hurt/dirt my fingers.
Richards engine is quite impressive as is.
To improve it needs drastic measures:
Throw the inlet valve and camshafts away and run rest as two stroke with a crank cam.
Peterha and Greg has mentioned YS engines as the ones to beat and their suction cycle is two cycle under piston.
Using a valve to control exhaust for a two stroke makes noise picture/output equal to a fourstroke I think.
Also the biggest source for two stroke fuel loss is hindered somewhat by having exhaust away from inlet.
The difficulty is that exhaust-valve shall move two times as often as in a fourstroke.
Asume that a Harley Side inlet valve is 44 mm diameter and open 11mm 67 times a second.Richards 10 mm valve can then be lifted 2.5 mm 300 times a second and endure same mechanical Stress .It is 18000 rpm ,quite fast.
It also leaves me with the feeling that Harley valve dynamics was not the limit for power,but rather some horrible flow conflicts.
A two stroke SV Harley would have breathed much more free.

 

[Niels Abildgaard]

Hello Richard

Greg has sent me a link of real nice two strokes in another thread here.

http://www.50products.com/english/index.html

The man had me confused as there are some very strange fourstrokes and then some lovely two strokes but not single side valve and we all know that this is the shining future?
Can You please give me the lowest mass of piston plus pin and connecting rod mass of your 24 times 24 mm engine.I am working on the layout with a geared counterrotating balance shaft .It can be a very compact ,civilized and powerfull engine.
It is a shame that more and more fly electric.

 

[Niels Abildgaard]

An updated sketch of a 24 24 mm sidevalve twostroke.
I realized yesterday that I have NEVER touched,dismantled or adjusted a sidevalves so feel free to make me wiser.
I will be easy to make an OHV two stroke with rocking arm as well .
Has there been some serious measurements (power,rpm fuel consumption ) on the Lynx 15 ccm?

 

[ownthesky2010]

Hi Niels
Your design is coming along nicely. I cant really give you much advice on side valves because the only one I have ever seen or touched is my own one. I chose the side valve layout because its compact, reliable and easy to design/machine and maintain. Also I wanted the engine to be a similat size and weight as a 2 stroke engine. I am prepared for it to have lower power than the ohv but I don't believe its as bad as people say. I am nearly satisfied with the performance of mine and ready to start on the twin cylinder version followed by a 5 cylinder radial as soon as I have built a carb and new head. I have not had time to do any engineering this week and I have broken the blade on my bandsaw so I wont be able to start till next week but I will keep you up to date. Maybe tomorrow I will be able to dismantle and weigh the piston etc. I think it will be very light weight as I kept the parts simple but thin walled. Although the roller bearing is steel.
I did cheat a little and bought the cylinder liner and piston ring from hobbyking. Hence the odd sized bore.
Parts for asp engines are so cheap at hobbyking that its just not worth the time to build them, as long as you are patient.

 

[Hopper]

Hi Ownthesky2010
Good rationale for using a sidevalve design indeed. I would not expect power output near that of a similar sized two stroke but certainly close-ish to a slightly smaller capacity four stroke.
The 750cc Harley sidevalves raced in America up to 1969 against 500cc OHV bikes and performance was neck-and-neck.
The BSA Goldstar 500cc OHV was considered to have the highest hp per litre for any naturally aspirated pushrod engine developed.
But it could not beat the 750 sidevalve Harleys.

So perhaps you could expect a 15cc sidevalve model engine in good tune to give similar power, or a little more, as a 10cc OHV.

Tben the AMA changed the rules and 750 OHVs were allowed to race so the sidevalve racer's days were over. and the Triumph/BSA 750 four strokes took over.
But, then along came the Yamaha 350 two-strokes and beat them all!! So a 15cc sidevalve model engine might have similar power to a 6cc two stroke????

Nevertheless, there is a lot that can be done with sidevalves. They dont have to be tractor engines. Take a look here
http://www.beautyofspeed.com/workshop/motor.htm

and here
http://victorylibrary.com/main_menu.htm

for a wealth of information on squeezing the most out of this simple, reliable design..

The main secret is gas flow both in the ports and through the combustion chamber. It is always trying to find the right balance between opening up the combustion chamber for gas flow versus compression ratio. Harley found the best way was to forget about compression and focus on flow. Hence 5 or 6 to one. But that is on pump gasoline, not model aeroplane fuel!
Another thing they do is to run a "pop up" piston that sticks up above the top of the bore at TDC by quite a bit. This allows a higher combustion chamber roof which allows good gas flow from the valves to bore, but the piston at TDC "pops up" and fills that space, thereby increasing compression to what it would be with a normal flat top piston and flat combustion chamber.

As a bit of a Flathead "nut", I look forward to your multicylinder projects. Please keep us posted.