# Sidevalve single



## ownthesky2010 (Dec 21, 2014)

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 (Dec 21, 2014)

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


----------



## ownthesky2010 (Dec 21, 2014)

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 (Dec 21, 2014)

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 (Dec 22, 2014)

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 (Dec 22, 2014)

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 (Dec 22, 2014)

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 (Dec 22, 2014)

ownthesky2010 said:


> 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 (Dec 22, 2014)

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 (Dec 23, 2014)

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 (Dec 23, 2014)

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 (Dec 23, 2014)

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 (Dec 27, 2014)

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 (Dec 27, 2014)

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 (Dec 27, 2014)

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


----------



## petertha (Dec 27, 2014)

.. 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 (Dec 28, 2014)

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 (Dec 28, 2014)

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 (Dec 28, 2014)

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 (Dec 28, 2014)

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.


----------



## mu38&Bg# (Dec 28, 2014)

The timing figures for the Vega 30 are much wilder than your engine, ownthesky2010. http://modelenginenews.org/cardfile/vega30.html I think plug location would be the first thing to investigate. Being side valve it simply won't make a ton of power. Anything you can do to make it run better than it is, should make a little more power. In the video it seems pretty rich, but that could be poor combustion due to plug location. You want to try to get the plug centered to the chamber. Later Ricardo chambers put the plug over the exhaust valve to reduce knock, but I don't think knock will be much of an issue here. Opening the passage to the cylinder would be worth trying. I would think compression ratio shouldn't have much effect, unless it's knocking.

How much oil is there in the fuel you're using?

Greg


----------



## ownthesky2010 (Dec 28, 2014)

Thanks for the advice Greg. I have read that side valve engines can be choked by too much compression and that's why I'm considering lowering it but I will move the plug first. It would be great if I had some idea what to aim at as far as rpm is concerned. I know the vega series were considered under powered but can't find specific prop and rpm info. 
in the video it is running rich at lower rpm but the carb only had a high speed needle. I will revert back to the original carb I used with twin needles and a larger bore as the first run was definitely better.


----------



## ownthesky2010 (Dec 28, 2014)

also I have found no difference between 25% and 18% fuels.


----------



## canadianhorsepower (Dec 28, 2014)

please have a look at the complete engine configuration
 before making any statement .


----------



## mu38&Bg# (Dec 28, 2014)

Sidevalves require a lot of compromise in combustion chamber design. That's why they were abandoned so long ago. Ricardo did a lot of work with this head design. His work would be well work the read if you intend to optimize it.

Here's another sidevalve, the Puck by Little Locos. http://modelenginenews.org/ed.2008.03.html 9.5:1 compression ratio.

https://www.facebook.com/media/set/?set=a.10151419042489804.542453.173276619803&type=3

Greg


----------



## canadianhorsepower (Dec 28, 2014)

did I mention this before......

 please have a look at the complete engine configuration
before making any statement .

 anybody can copy and paste article. understanding them is another matter


----------



## ownthesky2010 (Dec 29, 2014)

Thanks for all the advice. Dieselpilot I will do a bit more research into head design.
I have done another video with the first carb I tried. I get 7380 rpm do there is some progress.
I have cleaned and smoothed out the combustion chamber since then but is too late to get rpm measurement so I will try it tomorrow.


----------



## ownthesky2010 (Dec 29, 2014)

[ame]https://www.youtube.com/watch?v=NDNAYWDaQfw[/ame]


----------



## mu38&Bg# (Dec 30, 2014)

That sounds much better. It seems to sag as it warms up at full power? Are you familiar with the carb you're using? Some have a lot of interaction between the two needles, I'm not sure about the one you have. ASP?


----------



## mu38&Bg# (Dec 30, 2014)

petertha said:


> .. 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.



Peter, does valve lift include rocker ratio?


----------



## canadianhorsepower (Dec 30, 2014)

it does sound better but before trying any major change
 block that plug hole and relocate your plug.
 that massive extra fuel sptiing out must be fixe first

 good luck


----------



## petertha (Dec 30, 2014)

dieselpilot said:


> Peter, does valve lift include rocker ratio?



No sorry, I'm glad you brought this up. Its inconsistent to the point of being borderline useless. I should probably remove the chart altogether to avoid any confusion. 

I remember starting a spreadsheet that took rocker arm geometry into consideration. For example the Edwards has short length of 0.500" & long length of 0.625" (short is to pushrod side, long is to valve side). But around this point I also recognized its still not a simple 1.25 ratio either because of geometry. The pushrods move the rockers in varying 3D space because they are driven by the cam followers moving radially outwards against the cam ring, but in offset plane. Actually this engine gets more interesting. The intake & exhaust cam followers are positioned fore & aft but on the same clock position. From what I can see, the max lift on both Intake & Exhaust cam lobes is 0.075", so that infers a (slightly) different resultant lift between I/E valves on that basis.

Because I was then specifically comparing valve lift of radials, I spot checked a few engines (Edwards, Ohrdorf & Jung) with Solidworks assembly motion, determined they were somewhat similar on resulting valve lift & called it good.

Good catch, please disregard my table. One day maybe I will backtrack & fix, but right now I'm working towards making swarf!


----------



## petertha (Dec 30, 2014)

ownthesky2010 said:


> Thanks for the advice Greg. I have read that side valve engines can be choked by too much compression and that's why I'm considering lowering it but I will move the plug first.



I don't know anything about side valve engines, my table was meant to be helpful about methanol glows in general FWIW. But the other thing I wanted to point out is, how sure are you of the CR? Did you do the syringe & liquid trick to validate head & displacement volumes? 

Reason I mention is, when I was messed around with this aspect, I was quite surprised at how 'little changes' can have a large affect on the CR number. I pylon race 2-S methanol engines & its a daily ritual to play with shims, plugs, even plug washers depending on the conditions. The rpm effect can be quite dramatic. Here is the post, but the part I wanted to illustrate was the 'effect' table.

http://www.homemodelenginemachinist.com/showthread.php?t=23705&highlight=compression+ratio


----------



## mu38&Bg# (Dec 30, 2014)

Peter, I have not checked lift/diameter ratios in model engines at all. Books say .25 valve lift/diameter is common. More lift than this requires careful port design to take full advantage of.

Greg


----------



## Niels Abildgaard (Dec 31, 2014)

Found this:

http://www.google.dk/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=0CCEQFjAA&url=http%3A%2F%2Fwww.ukintpress-conferences.com%2Fconf%2Fpmw07%2Fpdfs%2Fperformance%2Fpendlebury.pdf&ei=N6SjVIiYJ6GeywPvuoGQCw&usg=AFQjCNHbh2XqMDfY2FHKsAFZv6fkJ3b4Pg&bvm=bv.82001339,d.bGQ

where a fourstroke bike engine with 35 mm valves was made to go 16000 rpm.
There is not much more mass and flexibility in a sidevalve train than in a DOCH valve.Speed is not going to be the limit.


----------



## ownthesky2010 (Jan 1, 2015)

Dieselpilot there is definitely an issue with the carb. If I lean out the low speed needle it covers too much of the metering slot and affects the high speed mixture. I am focussing on the high speed for now. My plan is to make an air bleed carb at some point.
Peter I have knocked up a quick and dirty multiplug head to test various plug positions. I am also considering ultimately using a twin plug head so it will be interesting to see what affect it has.


----------



## canadianhorsepower (Jan 1, 2015)

[quoteDieselpilot there is definitely an issue with the carb. If I lean out the low speed needle it covers too much of the metering slot and affects the high speed mixture. I am focussing on the high speed for now. ][/quote]
 this is how these carbs work. you set up the secondary way ritch.
 then you set your Idle 1 and 2 to youre needed  then at full RPM you set the second one
 the total of the first and second needle is what you need for the complete fuel range
  the change in comp ratio I sugjested was only to have a faster acceleration


----------



## mu38&Bg# (Jan 1, 2015)

That's definitely a way to get through some plug position testing quickly. The carb issue is a little surprising. I don't think I've run into a carb that simply wouldn't tune. It would be worth finding the initial settings for the engine that carb is supplied with and starting from there. Usually just starting rich on both needles and adjusting the main needle at wide open throttle, then the low speed needle for a good transition, will work just fine.

Greg


----------



## Hopper (Jan 2, 2015)

Wow. Looks to me like you need to get rid of the restrictions between the valve area and the  bore area. I would get rid of those two pointy bits that stick out into the gas flow area and neck it down to one small channel. There needs to be a direct channel the width of the valve straight from the valve to the bore, in line with the centre of the bore. This gives maximum flow.

I don't know much (anyting) about model size side valves but I have been working on and hotting up side valve Harleys for 40 years or so. Below is some pics of the cylinder head and cylinder from a Harley KR side valve racer that lapped Daytona at 149.8mph in 1968.  Note how the head cavity offers no restriction to gas flow and is open all the way from valves to bore. Also, if you want max flow without too much compression loss, you can do like the picture of the cylinder and carefully grind "trenches" from the exact top edge of the valve seat contact area across to the bore. Just don't let the trenches get down too close to the top ring. Even so, the racing Harleys found that more than about 6:1 compression restricted gas flow too much.

If you want more info on tuning side valve (flathead) Harleys, google Harley KR, or Victory Library or Beautyofspeed.com.
It may not be directly relevant to model engines, or it may be. I don't know. But Harley developed those sidevalve racers for 40 years and they are the yardstick by which all others are judged. And fascinating reading if you are a side valve fan.
\


----------



## Hopper (Jan 2, 2015)

PS, forgot to add that the Harley design in the pics allows full exhaust gas flow at the same time as full intake gas flow during the period of  valve overlap. It looks to me, and I may be wrong, that in your model head, the incoming and outgoing gasses are all fighting to get through that one narrow notch at the same time.


----------



## Niels Abildgaard (Jan 3, 2015)

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 (Jan 3, 2015)

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 (Jan 3, 2015)

Just curious are you using 4 stroke plug or two stroke


----------



## ownthesky2010 (Jan 3, 2015)

tried with hobbyking no3 and os f type.


----------



## canadianhorsepower (Jan 3, 2015)

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


----------



## ownthesky2010 (Jan 3, 2015)

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


----------



## Niels Abildgaard (Jan 4, 2015)

ownthesky2010 said:


> 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 (Jan 4, 2015)

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 (Jan 4, 2015)

ownthesky2010 said:


> 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# (Jan 5, 2015)

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 (Jan 5, 2015)

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 (Jan 5, 2015)

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 (Jan 5, 2015)

Niels Abildgaard said:


> .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# (Jan 5, 2015)

ownthesky2010 said:


> 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 (Jan 7, 2015)

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 (Jan 7, 2015)

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 (Jan 8, 2015)

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 (Jan 9, 2015)

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 (Jan 10, 2015)

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 (Jan 11, 2015)

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.


----------



## Niels Abildgaard (Jan 11, 2015)

Hello Hopper

In racing it is the cubic that give the class to race,but from a technical point of view it is much more relevant to compare mass of engines.Is it unrealistic that a flathead 750 with racing crankwebs was same mass as the 500 ccm OHC competitors in racing trim ,engine plus gearbox?


----------



## Hopper (Jan 11, 2015)

Niels, hard to compare really. The Harley flathead used cast iron cylinders whereas the BSA Goldstar 500 used all aluminium alloy. Doubtless the Harley engine was heavier.  But what Harley did was lighten the whole bike and engine to compensate. Because it produced the same power as a 500 OHV, the chassis and the engine components were pared down to what woiuld be run on a 500, not a normal 750 OHV.

Same could be said for building a flathead model engine - if a 15cc sidevalve engine is producing the same power as a 10cc OHV, then you can make all components of the sidevalve engine such as con rods, piston, casings etc to the thicknesses and weight of a 10cc OHV engine. You should then end up with a 15cc engine that weighs just slightly more than a 10cc OHV and puts out about the power of a 10cc OHV.


----------



## Niels Abildgaard (Jan 11, 2015)

Hello Hopper

Thank You for reflections that are very close to  my own.That is always nice.
These fellows 

http://www.d-motor.eu/nl/fuel-consumption-110.htm

are making a SV aircraft engine and claims 260 gram of petrol per kWh.
The watercooled Continental that went around world unrefueled was 240 and the Rotax 912 is 280.


----------



## Hopper (Jan 12, 2015)

Hi Niels
Thanks for the link. That is fascinating stuff.it
With 2700cc engine producing about 90hp, it is obviously tuned for economy and reliability and not maximum performance -- which is good in an ultralight!!
I see it has 8:1 compression listed. This would limit performance on a flathead by reducing gas flow between valves and bore.

Compare this with the Harley KR producing 50-60hp from 750cc at 6:1 compression. That's, say, 80hp per litre. Compared with with the D-Motor at about 32 hp per litre at 8:1 compression.

A huge difference. But of course the Harley racing engine might last only a race or two between major overhauls -- not something the ultralight owner wants. 

However, for a model engine, I think some of the Harley head/cylinder breathing designs may be of interest to play with. Also the cam profiles. They used very high lift cams with long duration and overlap. No worry about valves hitting the piston or hitting each other, so the cams looked almost square, and in some cases hourglass shaped, slamming valves straight to full open and keeping it there until closing time then slamming it shut. 

The two cams on the left are the race cams, compared with stock cams on the right, in the pic below. (All these cams are used with roller cam followers, which influences the shape to be less pointy than with flat tappets.)


----------



## Hopper (Jan 12, 2015)

PS, plus of course the D-Motor flathead compares well with the Rotax 912 by producing about the same HP from an engine of about the same weight as the 1200cc Rotax. A big capacity but lightly built motor with flathead simplicity. Perfect!
Perhaps we will see the return of the flathead to general useage?? Who knows, strange things happen.


----------



## Cogsy (Jan 12, 2015)

I have been following this thread with interest, but I must admit I'm missing something. These power figures being tossed around seem incomparable to real world OHV engines. For example, the 2011 Kawasaki ZX10 displaced 998cc and supposedly made around 210bhp at speed and over 200bhp without ram air effect. This is a road bike, built and intended for high mileage between rebuilds, not a highly stressed racing engine.

I realise you guys are primarily focused on model aircraft engines but I can't see the flatheads getting close to this type of possible performance.


----------



## Niels Abildgaard (Jan 12, 2015)

Hello Al
To compare flying engines on cubics is not right.
TBO,mass per power unit and specific fuel consumption at 75% max power is better.


----------



## Cogsy (Jan 12, 2015)

Fair enough. I know nothing about the bike's fuel consumption, nor relative engine weight for it's displacement. I do know the whole bike, frame, wheels, lights, brakes, seat, gearbox, etc, weighed only 198kg which seems light for 200+hp, but the aero engines may well have equal power to weight ratios. 
The only reason I asked was because of the discussion of the harley's vs 500cc OHV bikes. I thought it only fair to throw the ZX10 specs into the mix as a more modern example of a normal OHV bike.


----------



## Hopper (Jan 13, 2015)

HI Cogsy, I think the OP's intent is to build a simple, compact, lightweight engine for model aircraft, which the sidevalve suits admirably. Miniaturizing the technology that gives a Ninja 200hp is not really do-able for the average home-shop builder. Harley flathead technology though was so basic and simple it is not hard to repllicate. 

I think the link that Niels posted to the D-Motor aviation flathead and comparison to the Rotax engine is pretty encouraging. The Rotax is putting out only 90-100hp from a 1200cc. And Rotax do know how to build high performance engines if they want (viz BMW, Aprillia, Buell etc  etc) but for aircraft engines weight and size and fuel economy are also a big factor, not just straight horsepower. The Flathead D-motor by comparison is putting out 90-100hp from an engine that is 2700cc but the same weight and physical size as the Rotax. 

Is an interesting point though -- 210hp per litre is a far cry for the racing bikes' 80hp per litre of 1968. Of course the fastest road bike of that year was the 60hp Triumph Trident/Rocket 3 -- about the same as Harley's flathead racer.. How times have changed. Pity the Harley riders who try to drag race me off the lights when I am on my sportbike don't realise that!


----------



## Niels Abildgaard (Jan 13, 2015)

Hello  Richard

Here is my proposed fourstroke beater with lowest possible parts number count,but no first order balance.I am working on that but need the piston weigth.
Am asuming around one gram per ccm ie 11 gram for yours.


----------



## mu38&Bg# (Jan 13, 2015)

Niels doesn't your software figure at least volume for the piston?

The D-motor is an interesting result. Because it runs slow, it doesn't have to breathe particularly well, so the flat head design isn't as much of a problem. Surprisingly, it's efficient at 260g/kWh. I wonder what hydrocarbon emissions are like.

Greg


----------



## Niels Abildgaard (Jan 13, 2015)

Hello Greg 
The problem is that I have never constructed a piston for sale,but many others have.That means that a rule of thumb is better here but it interest me what Richard has dared to come down to.
One of the SV advantages is that piston mass can be low as pressures are not that high.
Considering emissions You should rather be concerned what comes out of american engines over Your head.
Lead is criminal and unnessecary.


----------



## ownthesky2010 (Jan 13, 2015)

This is some excellent discussion. I am soaking it all up here and its really showing me the gaps in my knowlege.
Thanks to everyone who has made a contribution.
I have started on an air bleed style carb and got as far as machining most of the main body and made a complete mess of the air bleed holes.
I drilled them 2mm instead of 1mm and now they intersect which makes having 2 of them pointless.
I cant decide if I should scrap it and start again or try to sleeve one of the holes.
Niels
I finally managed to weigh the parts you asked about.
Piston: 10g
Con rod: 6g
Wrist pin, ring and clips together: 2g
The total is 18g
A bit more than I thought but not too bad considering the only 4 stroke engines I have ever seen the inside of were motorcycle engines and none of them were sv engines.
Incidentally the spare conrod that I have without the bearings/bushes installed is 3g.
I think I will do some more weight elimination on the piston. The walls could be thinner. I have already re-designed the crankcase and timing module to lose some weight there.


----------



## ownthesky2010 (Jan 13, 2015)

This is some excellent discussion. I am soaking it all up here and its really showing me the gaps in my knowlege.
Thanks to everyone who has made a contribution.
I have started on an air bleed style carb and got as far as machining most of the main body and made a complete mess of the air bleed holes.
I drilled them 2mm instead of 1mm and now they intersect which makes having 2 of them pointless.
I cant decide if I should scrap it and start again or try to sleeve one of the holes.
Niels
I finally managed to weigh the parts you asked about.
Piston: 10g
Con rod: 6g
Wrist pin, ring and clips together: 2g
The total is 18g
A bit more than I thought but not too bad considering the only 4 stroke engines I have ever seen the inside of were motorcycle engines and none of them were sv engines.
Incidentally the spare conrod that I have without the bearings/bushes installed is 3g.
I think I will do some more weight elimination on the piston. The walls could be thinner. I have already re-designed the crankcase and timing module to lose some weight there.


----------



## Hopper (Jan 14, 2015)

Hi Niels,
I think one area you will need to look at carefully on your "fourstroke beater" is the exhaust valve. Because of the poor combustion chamber shape, flathead exhaust valves and ports get very hot. 
On a four stroke, the exhaust valve gets a rest every second revolution  but on a two stroke will get heated every revolution. I think it will need some serious cooling fins or even liquid cooling, ala D-motor, in that area.


----------



## Niels Abildgaard (Jan 14, 2015)

Hi Hopper

I had not realized that so thank You for warning.It will be eased somewhat as two strokes exhaust is a mix of  hot real exhaust and cool fresh charge. 
I am wondering how the inlet ports shall be placed around cylinder to minimize this air/fuel loss as much as possible.
The bst cylinder material is probably aluminium with an inserted bronce valve seat ring.
Bang went the low cost goal.


----------



## Niels Abildgaard (Jan 15, 2015)

ownthesky2010 said:


> .
> Niels
> I finally managed to weigh the parts you asked about.
> Piston: 10g
> ...



Hi Richard
Thank You for numbers.Amazing good engineering yourside.
Have been scheming a firstorder mass balancing system using Your numbers and it can be easily done without tungsten or unobtanium.


----------



## ownthesky2010 (Feb 6, 2015)

Hi all
I have this thing about where I want it now. Been through a few carbs and finally settled on a slide carb from an rc car with a modified low speed needle. This engine likes the fuel metered up to around 80% throttle so the lsn had to be re-profiled a few times. The high speed needle only affects the last 20%. I still have a bit of tuning to do but I'm confident that this carb will work and give me a stable 7800rpm on top. 
I have also managed to get it running well without glow power constantly attached.
The head is a quick and dirty test part with a bigger combustion chamber and lower compression, hence the lack of cooling fins.
I'm going to stop working on this engine now and start on the twin version. 
Then build a carb based on the rc car model with a few of my own tweaks.
Thanks a lot for all the contributions everyone, its great to have a place to go to for advice.

[ame]https://www.youtube.com/watch?v=Z1zmY6bEN8Q&feature=youtu.be[/ame]


----------



## Niels Abildgaard (Feb 7, 2015)

Hello Richard
Very nice engine sound and your devellopment speed is impressive.
What kind of twin and crankshaft is next?


----------



## ownthesky2010 (Feb 8, 2015)

Thanks Niels.
I'm planning a flat 180 degree twin with shared crankpin. 
The cylinder, cams, piston etc from the single will be reused.
I only built the single to test the design. 
After the twin I will build a 7 cylinder radial.


----------



## Art K (Feb 8, 2015)

Hi, ownthesky2010,
I caught your last post and was reminded of a portion of Herschel Smith's book "A History of Aircraft Piston Engines", and yes I read the whole book. Chapter ten is about the opposed engine. He talks of a 1917 Lawrance C-2, "It set at naught the basic advantage of the opposed engine by using a single throw crank." He also used Mickey Mouses name in vain and mentioned Newtons first law. The gist of this was that both pistons going back and forth shook the airplane apart. I would suggest a two throw crank, although not as simple to make, the pistons going back and forth cancels each others movement out, making the engine fairly well balanced.
Art


----------



## mu38&Bg# (Feb 8, 2015)

Saito produces single throw opposed twins. People say they run smoothly. I did run one maybe eight years ago and didn't remember any unusual vibration. The crank just needs enough counter balance mass. It balances just like a single cylinder. I can say that the opposed boxer twins OS makes run very smoothly. I have an FT-160 on an aircraft now.

Greg


----------



## Niels Abildgaard (Feb 9, 2015)

Hello Richard
A hanging V2 will be much smoother and fit the nose of ME 109 models.
It is not difficult to design the counterweigths.
Bring relevant parts in these two positions and  remove or add mass to counterweigths so that center of gravity is the same.


----------



## Hopper (Feb 9, 2015)

Hi Ownthesky2010 -- Your engine sounds beautiful, that distinctive flathead noise. Very nice work. 
Sounds like you got the right compromise between compression and flow. At the end of the day, all that counts is the actual pressure in the cylinder at the end of the compression stroke -- whether achieved by small combustion chamber or by cramming more charge into the cylinder before compression begins. Seems the latter is the way to go for flatties.

Looking forward to seeing your flat twin. Seems like the small mass of model engines allows makers to get away with single throw crankshafts. I know that all flat-twin motorcycle engines (BMW, Zundapp etc) use double throw cranks so both pistons travel in opposite directions, aka "boxer" like two fists pumping in and out alternately. 

Might be the secret to single throw crank is getting the right balance factor? Makes may head hurt just to think about it. Like balancing a single, but then you have the weight of the other rod big end rotating and piston reciprocating in the same direction as the first piston. So balance weight might need to be double the weight of what you would use for a single??

Any how, have fun with it and keep us posted.


----------



## ownthesky2010 (Feb 9, 2015)

Thanks for the encouragement guys.
I think I just have my own funny little ways.
As long as I meet a minimum standard of performance/efficiency I don't think that more makes a better engine.
What really interests me is character and presence.
I chose the single throw crank because I'm hoping for a nice lopsided/offbeat exhaust note that will sound good in a model plane.
I'm thinking of it as a 180 degree v twin or 2 cylinder radial  
These engines are a compromise in every way.
Maybe by getting it all wrong in all the sensible ways it will end up just right in the way of character.
Niels thanks for the v twin info. Its on my todo list too, although with another 10 cylinders.
As far as balancing goes, it does have me a little worried. 
I think I just balanced the rotating mass + half the reciprocating mass with the single so I might try that again. 
I will probably need to insert something heavier than steel as the crank web is not very thick. 
Maybe tungsten carbide, my local Tesco doesn't sell depleted uranium.
At least a crankshaft is fairly easy to remake/modify.
If you turn it from an 8.8 bolt its halfway to the right shape already.


----------



## Hopper (Feb 20, 2015)

Hi OwnTheSky
Yeah, I reckon you should get away with the single throw crank in a small engine. 
What you are doing is essentially the same as what goes on inside  parallel twins having a 360 degree crank: two pistons and rods travelling in the same direction at all times. I know from vertical 360-degree twin motorcycles (Triumph, BSA, Norton etc) that the 350cc and 500cc models were sweet running bikes. But the 750s were vibrating monsters and the 850 Norton necessitated a rubber mounted engine!
So such an unbalanced set up can work in small engines better than large.

Yes, I would think balancing like a single - all the rotating plus half the reciprocating mass -- would work ok. Just remember that the reciprocating weight now includes two pistons and the proportion of two rods. So it will need a counterweight twice the weight of the single. 

Another advantage of the side valve is that its low compression causes less vibration than a higher compressed engine of the same layout. So that should help you get a smooth runner.

Have fun doing everyting the "wrong" way and making it work.


----------



## Niels Abildgaard (Jul 24, 2022)

Niels Abildgaard said:


> 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.


I dreamt up a two stroke with sidevalve exhaust many years ago and have the pleasure of seeing it considered as future car engine.
Try reading session five papers from a conference 2020
Future two stroke


----------

