Air Cooled 2 Stroke Cylinder Head Using Shell Casting

Not Long ago, we decided to make a custom air cooled cylinder for a two stroke engine that we're developing.

We decided to use Shell casting, mainly because we'd never done it before.

Step 1: Patterns and Sand Box

First we CNC machined some patterns and some boxes to hold the sand

Step 2: Shell Sand Mold

Heat the pattern and invert the sand over it. The sand is coated with a thermoplastic resin that binds together and forms a shell. This is used as the mold to pour the aluminum

Step 3: Make the Castings

Pour the aluminum. fettle and shotblast

Step 4: CNC Machining

Machine the Cylinder head to fit your engine

Step 5: Fit on Engine

Enjoy!!

Comments

[Armilite]

What Engine was this Head for? What do you charge for the Heads?

[thecoolsundar]

It's for a small agricultural engine that we manufacture.

The head costs about USD 6

[Armilite]

You ought to repop some Skidoo/Rotax 2 Stroke Singles Heads and Cases. The Skidoo 277F is also a 277UL Ultralight Airplane Engine. A used 277 Head goes for $50 on eBay. A Rare Expensive Head is the Skidoo Blizzard 292 & 340 Free Air Head $400 if you can find one. The 277F/277UL is (72mm x 66mm) 268.4cc and uses 11.8cr. The 340 Blizzard (36hp) was (78mm x 70mm) and the 292 Blizzard was (75mm x 66mm). 1st photo 277 Head, 2nd 277F, 345 are a 340 Blizzard Engine.

[MarioM90]

Hi, what is the resin composition?

[thecoolsundar]

It's a phenolic resin with a hexamine catalyst

[steveastrouk]

VERY nicely documented.

[steveastrouk]

No, you are making near net shapes by casting, the time to machine the final details is a LOT less than the cost of milling the fins for example.

[Armilite]

If you have a CNC machine, wouldn't it be easier to use Billet Blanks or Pour your Scrap Aluminum into Blocks and then just Machine them into Heads? Depending on the Size of your CNC Table, you ought to be able to setup anywhere from 3-6 Heads to be machined. You can Cut Flat Raw Stock on a cheap Table Saw with the right Blade. What CR are you using on that Head, and what Bolt Pattern? What do you charge for them in USD? You ought to make some Rotax 277UL(26hp@6250rpms) Single Cylinder Engine parts, Head, Cylinder, Case. Head/Cylinder use's a (4) Bolt Pattern based on a 100mm Bolt Circle. They use 8mm Studs. What CC is your Engine and Hp@rpms? What is it for?

[johnip4]

what did you put on top of the casting that burst into flames? Why do you do that?

Thanks

[thecoolsundar]

It's an exothermic hot topping compound. It is sprinkled on the risers to make sure they remain molten till the casting freezes. This ensures a sound casting

[acheide]

Very nice project. Thanks.

[DIY Hacks and How Tos]

Awesome project. You've got my vote.

[thecoolsundar]

Thank you

[gm280]

Interesting project. Looks like you modeled it off a Briggs and Stratton style engine.

[thecoolsundar]

Nope. The starting point was a Honda 2 stroke scooter engine