# Single cylinder OHV - "Snöffy"



## srobovak (Oct 7, 2019)

Hi HMEM,


I have been working on this one for over 4 years now and it finally came to a successful end...

After researching numerous builds from other people and combining things together I eventually distilled my own engine design.
I wanted to work in the metric system and also wanted to adjust the size of the model and its complexity to my own demands. As most of these models serve only the purpose of pleasing the builder as they come "alive" I also wanted a design that would suit my own aesthetic ideas of how it should look like.

I opted for the looks of an early 20th century motorcycle single.  After about 3 years of irregular work, I had my first test run which was a failure. The engine would not run continuously even though I had a few puffs. I re-evaluated a couple of things and decided to change the cams to milder timing characteristics, enlarge the flywheel, improve the valves and their sealing and also improve the sealing of the carburetor. This work took me about 5 more months to complete.
But the second try was an immediate success. The engine now starts really easily and runs quite well. The RPM range is quite narrow though - it idles at around 950 RPM and reaches its maximum at 1800 RPM.
It also needs some time to rev up and down this range which is due to the large flywheel. I am also pleased with the way it sounds which was also one of my goals.

Some engine details:

- the square design of 25 mm stroke to 25 mm bore
- spark plug ignition using NGK CM-6
- home-brewed stand-alone ignition module using automobile coil
- O.S. 1A carburetor
- running on Coleman fuel mixed with 5% 2-stroke oil
- splash lubrication

I would like to thank everybody on this forum for your time to share this great hobby with others. Special thanks to Terry (mayhugh1) whose posts helped greatly in finishing this project.

Till next time. Cheers,

Branislav


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## johnmcc69 (Oct 7, 2019)

Beautiful engine & it sounds great!

 Real nice job!

 John


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## awake (Oct 7, 2019)

Beautiful indeed! I love the mounting using the curved sections.

Any thoughts about whether you might offer the plans for sale?


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## Brian Rupnow (Oct 7, 2019)

Beautiful engine. One of the nicer ones I've seen.---Brian


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## kuhncw (Oct 7, 2019)

You've built a very nice looking engine.  I like the low rpm idle.  Sounds great.

Chuck


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## Cogsy (Oct 8, 2019)

Nicely done and runs as nice as it looks. Congrats.


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## TonyM (Oct 8, 2019)

Very impressive and a really smooth runner. Sounds lovely.


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## tornitore45 (Oct 8, 2019)

On top of all compliments given by others I should say I never seen an engine with suck a slow stable idle, one can almost count the revolutions.
Great work.


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## minh-thanh (Oct 8, 2019)

The engine sound is great , Great engine and congratulations !


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## ShopShoe (Oct 8, 2019)

Congratulations. What everyone has already said. Beautiful, well-thought-out design, Runs smoothly and sounds great. Fantastic low-speed idle and smooth throttle response. I wanna make one someday!

Can anyone give me a hint as to how the name should be pronounced? I'm not good at umlauts.

--ShopShoe


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## peter2uat (Oct 8, 2019)

ShopShoe said:


> Congratulations. What everyone has already said. Beautiful, well-thought-out design, Runs smoothly and sounds great. Fantastic low-speed idle and smooth throttle response. I wanna make one someday!
> 
> Can anyone give me a hint as to how the name should be pronounced? I'm not good at umlauts.
> 
> --ShopShoe


The "Ö" is spoken like the 'e' in "her"


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## dethrow55 (Oct 8, 2019)

hello that is a super nice build. any plans for sale? thanks  pm me.


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## Mechanicboy (Oct 8, 2019)

peter2uat said:


> The "Ö" is spoken like the 'e' in "her"



Same as in norwegian "Ø". Stirling <Støling>, Bird <børd>.. 

Nice build engine


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## plipoma (Oct 8, 2019)

I would also like to purchase drawings.


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## Johno1958 (Oct 8, 2019)

Beautiful engine. Congratulations.


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## e.picler (Oct 8, 2019)

Congratulations! Top Noch project and work.
Very nice low idle.

Also interested in the plans.

Edi


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## srobovak (Oct 9, 2019)

I thank you all for your kind words and your interest in this engine. 

One of the most important lessons learned is that one must properly finish the 3D-model and all technical drawings before the machining begins. I was impatient and kept changing and adjusting things as I went along. This means that the drawings are inconsistent and include plenty of mistakes. There are about 20 combination drawings and I would have to revisit them all and probably start with updating the 3D-model itself. I'm on a tight family schedule now and can not afford to do this. 

Maybe I will revisit it someday and compile the set of drawings that I would feel comfortable about and can make public.


Till next time. Cheers,

Branislav


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## John Antliff (Nov 8, 2019)

Beautiful engineering.  I guess the large mass flywheel is mostly responsible for the smooth slow running just like the full size hit and miss engines heavily rely on the large rotating flywheel mass to keep going.  With a single cylinder engine you definitely need a big flywheel!


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## SteveM (Nov 9, 2019)

A truly unique and stunning piece of engineering Branislav, beautifully designed and created. I'd just like to add my name to the long list of people who'd happily pay for the plans if they ever became available.


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## oldCB (Nov 11, 2019)

srobovak said:


> Hi HMEM,
> 
> 
> I have been working on this one for over 4 years now and it finally came to a successful end...
> ...




  Absolutely Gorgeous!!


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## kadora (Nov 11, 2019)

congratulation Branislav -really perfect runner.
are you from Slovakia ?


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## srobovak (Nov 11, 2019)

Thank you all, and yes I'm from Slovakia.


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## nel2lar (Nov 11, 2019)

Beautiful engine with a gorgeous sound, prefection.


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## necchiom (Nov 17, 2019)

Awesome! Well done.


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## Rozlo (Nov 19, 2019)

Awesome build.  Runs great Nice job.


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## Drew (Nov 28, 2019)

Really great engine. Everything looks so well detailed. 
Thank you for sharing.


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## Mark Lewus (Dec 8, 2019)

What a great build! It sounds beautiful, especially at low idle. I too would gladly pay for plans.


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## popnrattle (Dec 9, 2019)

Very nice!


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## werowance (Dec 18, 2019)

Nice,  and the adjustable height fuel tank is such a good idea.  ill have to copy that idea some day.


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## srobovak (Dec 23, 2019)

Yes, the adjustable fuel tank is quite handy. I was experimenting also with the fuel pump but I have found out there was no real need for it. 

One thing I would suggest to do differently is to add a height adjustment screw running parallel to the post. This way you can experiment more easily with the influence of the fuel level with respect to the carb's nozzle height.

cheers,
Branislav


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## bluejets (Dec 23, 2019)

You could go with the standard arrangement for model aircraft engines as an example, where the centre of the tank is placed 10mm below the centre of the venturi.
Later model engines had the tank centreline the same height as the venturi centre.
Then set needle a tad on the rich side with a full tank.
As you found, no need for any fuel pump.


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## littlelocos (Dec 24, 2019)

Great Job!  Beautiful.  It sounds like such a happy little engine.


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