’Rolssi’ a homemade 6.28cc 4-stroke vintage model aero engine

Rolssi is a true Finnish classic originally designed back in 1936 at Vyborg Finland by Urho Purhonen and Aarne Heikkinen.
My friend and model engine builder colleague KalleR made the CAD model couple of years ago and built a fine example of this same design about a year ago. This is the second succesful replica of the original engine that I built. The build started in October and the first run of the engine was achieved first of February 2024.
Rolssi seems to be quite sound design given its age and is an easy starter and puts out over 0,2HP at around 6800rpms.
My example has ran now 8th times in total on cdi ignition and future plans hold a proper vintage spark ignition with coil and points and also a vintage style period correct wooden propeller.
The performance with Master Airscrew 12x5 Scimitar propeller is 7000rpms (0.24bhp) and fuel consumption around 236ml/h!

[@erdelybela2416]

I forgot to like it when it came out, but I made amends now. Such a great project to see, from Viipuri of the "golden age", a decade full of hope and progress in Finnish history (until it soured)

[@joseisraelramirez9251]

Very nice . Congrats

[@valic000]

You are amazing Olli! Really an amazing build! It purrs lovely away!!! A lot work, but for sure the sweetest reward....Big thumbs up mate!!

[@OlliKarhun]

Thank you very much Peter! 🙏🏻

[@anovozhilov]

Unbelievable! Hats off to such masters! Great job! +

[@patrickshaw8595]

I think you should use breaker points with a 1988 Ford Thick Film Ignition module of the minivan-remote-from-distributor-on-a-heatsink kind. When used with it's matching coil it can supply a V8 with sparks to 5000rpm. Best of all is somehow it calculates the proper "on" time for it's coil before every spark. It also shuts off after one second of no rotation. Marvelous piece of old tech nearly as hot as GM HEI which everyone know is a PITA but has a strong spark.

[@sicks6six]

McCully racing supply them,

[@sicks6six]

I've just realised how much I need a miniature ICE bolted to my coffee table,

[@billbannister9411]

Very nice job a real credit to you keep up the good work

[@OlliKarhun]

Thank you very much sir!

[@RustyInventions-wz6ir]

Nice work. Looks and runs great

[@OlliKarhun]

Thank you very much sir!

[@ajuste4369]

Bravo ! Formidable ! Excellent travail de Technicien supérieur !

[@EnglishTurbines]

Beautiful old engine design...I can't decide if Im more impressed by the engine or the facility's you used to make it with...🤔😳😏🇬🇧

[@andymunnings9109]

"Know what I like about this engine? It was built solid; And? That is what is needed. No plastic fittings for fluid fuel corrosion due to tolerance of material. However? I would like you to install a spring crank around the shaft area near the spinner for easy start. Overall? The item is good." 👍

[@aileronmodelismo]

Awesome work!!!👏👏👏

[@kencroft7933]

Wonderful work again. Your most complex yet. Congratulations.

[@OlliKarhun]

Thank you very much Ken! 🙏🏻

[@kencroft7933]

It seems hardly any time ago that I was advising you on choosing a small lathe, and then later encouraging you to have a go at making your own castings! You have come a very long way in that relatively short time. You must be very pleased and proud of your achievements.

[@OlliKarhun]

@@kencroft7933Indeed! I looked back and checked, it was about 3,5 years ago 😁 Now nine engines later I am definately very happy how things have gone so far. I also realize I am still very new to machining but really looking forward to the upcoming projects and challenges. I have received a lot of help from people like you and many others along the way. That is the best part. Much appreciated 🙏🏻

[@kellyodom9596]

Beautiful. Thank you for sharing.

[@rcdogmanduh4440]

Nicely done, ignore the peanuts!

[@bambukouk]

thank you

[@suokmi]

Ei tähän voi muuta sanoa kuin että teet hienoa työtä! Luin jo pienenä poikana Rolssi-jutun Tekniikan Maailmasta, se teki minuun suuren vaikutuksen. Minulta tällaiset jäävät rakentamatta, mutta onneksi sain nähdä ja kuulla Rolssin käyvän edes muiden rakentamana.

[@OlliKarhun]

Kiitos Mikko!

[@pirminkogleck4056]

Master Olli ! Superb Engineering here !

[@OlliKarhun]

Merci PJK 👌🏼

[@petercroonen1086]

Great job !!

[@user-pw9np9ue8r]

Respect.

[@markoalho434]

Aivan Uskomatonta tekemistä.😮

[@OlliKarhun]

Thänkjyy Marko 🙏🏻

[@maurohenriquerodriguesdasi261]

Fantástico...

[@tenlittleindians]

It's listed as a 4 stroke; does it have an oil system or is oil mixed with the gas for lubrication?

[@OlliKarhun]

@tenlittleindians it has 2% of synthetic oil mixed in the fuel and 15ml of motoroil inside the crankcase for splash lubrication.

[@Itsme-kz6ui]

I watched your video about making the Nova-1 4.5cc engine, everything was cool, I really liked the video. Please tell me what material the piston is made of? made of the same material as the cylinder?

[@OlliKarhun]

The piston of the Nova-1 is made of cast iron and lapped to fit. The cylinder is 42CrMo4 as is the cylinder sleeve on this one. This article describes the process of making the piston / cylinder fit exactly, highly recommended: www.adriansmodelaeroengines.com/catalog/main.php?cat_id=178

[@simplebronzecasting]

​@@OlliKarhun Very interesting article! I also want to try to make this engine (Nova), but this is after my projects😊

[@OlliKarhun]

@@simplebronzecasting very nice! It is a great running simple engine. I have really liked your investment casting work! My compliments! Would love to try and learn that one in the future also 👍🏼

[@simplebronzecasting]

@@OlliKarhunThank you very much 😊 Yes, this method of casting is quite simple, the components of the molding mixture can be bought in any construction store, and at the same time it is possible to obtain castings of complex shapes with this method.

[@marcossoaresdearaujo]

Perfeito...

[@eeromahonen7282]

Upeaa työtä..

[@RizHassan]

All this hardwork, and you used brass bushing...well atleast you did'nt use needle bearings.

[@EnglishTurbines]

Bronze ..😳🤔🇬🇧

[@sawek2993]

Poezja. Cudowny gang.