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Nikasil Cylinders

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Mike0101

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If you're asking why change from steel or cast iron to aluminum jugs with special coating(s)?

Aluminum piston's thermal expansion coefficient is higher than that of steel or cast iron. Or it expands (grows) at a greater rate than the bore it's moving up and down in. To account for this, you'd add clearance, but with added clearance comes, more blowby (less power), higher tension rings (more friction), piston slap (when cold), more oil consumption (may or may not be significant).

Also aluminum has a better thermal transfer coefficient than steel or cast iron. So if you can move and dissipate more heat, you can make more power.

No experience with VW stuff, but have a love/hate relationship with Nikasil and other similar coatings on other engines.
 
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TiPi

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I know nickies are available for vw platform. But they are stupid expensive. That and they come with je forged pistons which is a bit overkill for a 40 hp 3100rpm engine when stock cast mahle pistons will work.

I know no one is going to give up their metalurgy of what aluminum they are using. Im asuming cast 356-t6 just like every cast cylinder, Head or block is made of now days.
Even though you do see big bore machined cylinders for 2 strokes and 4 strokes made of 6061 and then plated. Would 7075 be better choice to start with? I have an 8" diameter log of that as well.

I dont understand the difference in strength between centrifugally spun cast and a piece of extrusion. Only thing i can think of not related to strength is the casting is slightly more porous than the extrusion and allows the nicasil or whatever the company is calling it to penetrate deeper into the metal.
Id be leaving my bore finish size to gheir specs for my pistons and having them do the propper clearancing, plating, and honing.

The next question is if running aluminum or mag case, aluminum cylinders, aluminum heads thoughts on bolting cylinders to case with a flange and bolts and bolting heads to the cylinders. Not using the long studs? Not applicable to stock vw configuration but working on something else.
The reason for the centrifugally spun cylinders was to increase the carbon content at the inner surface of the cylinder (carbon is much lighter than Fe) and to reduce the porosity and inclusions in the thin fins and walls.
 

slociviccoupe

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Tipi thank you. I was under assumprion that scotts cylinders were just nickies sold by him.

And anyone thinking nickies are "billet" they are misinformed. They are cast cylinders with their firm of nickel silicon carbide coating on cylinder walls.

Everyone seems hung up on the switch from steel to aluminum but that is not the original question. Many 2 stroke and 4 stroke engines are running milled from 6061 barstock aluminum plated cylinders and do fine.

The question is if the material is adequate?
6061-t6 or 7075-t6
If a cast cylinder most likely made of 356 alloy holds up why wouldnt a turned from extrusion. Only difference being of being an extrusion vs being centrifugally cast.

Id buy nickies of i had to but honestly no reason for that pricing. Especially for 2 cylinder 1/2 vw. And my reasoning to switch is weight and thermal capacity.
 

Hot Wings

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The question is if the material is adequate?
You have to define "adequate".

Aluminum cylinders have some advantages compared to steel. Expansion rate, heat dissipation are different. Both can be plated. The problem for the VW cylinders is the deformation under load. Comparing these with other aluminum cylinders is not apples to apples.
In the VW we are stuck with a given dimension that limits the wall thickness. Outside dimensions aren't a consideration for engines designed to use aluminum cylinders.
On the VW, even with steel, we have found that thick is better. Some of us like using 90.5mm pistons in a thick cylinder cut for 92mm spigot dimensions. The same with 92mm pistons in 94mm size holes. Even in the early days of slip in 88s we found they didn't last as well, or make any more power than the 87s.
If we could move the VW head studs to a larger diameter then we could thicken up the top of the barrels and maybe get reasonable distortion from an aluminum cylinder under load. Is it worth all that work just to get the heat and expansion advantages of an aluminum cylinder?
There will be very little, if any, weight savings compared to a steel cylinder - with equal distortion under combustion pressure.
 

osprey220

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And anyone thinking nickies are "billet" they are misinformed. They are cast cylinders with their firm of nickel silicon carbide coating on cylinder walls.
I think you are wrong. Both Scott's and LN engineering say their cylinders are CNC from billet. I've seen both and held both in hand - they look very very different from a cast cylinder (such as QSC's).

From VW Type 1 - Nickies Cylinders for Aircooled Porsche and VW Engines - Products
"Our NSC-plated, CNC billet, solid aluminum Nickies™"

slociviccoupe, Are you asserting that Scott and LNEngineering are lying?
 

slociviccoupe

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A good quality casting you can turn in lathe and it look like a machined from solid. Your just machining the surface of the casting off. Look at cast aluminum cylinder heads and engine blocks. you can surface them to mirror shine even see the rainbow in them from heat treat.
 

slociviccoupe

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And the term "billet" gets tossed around so much. People will refer to 6061 t6 as aircraft aluminum when its not, an extrusion or solid block will be called a billett.

Maybe they are machined from solid piece of aluminum, who knows. But last i read nickies were centrifugally cast aluminum. Doesnt mean sand cast, wax cast, or investment cast.

And there really is no difference between melting aluminum and other allowy and extruding it through a die and pouring molten aluminum into a spinning mold.

The term "billet" could mean the solid shape it was machined from.

Not calling them liars but its all terms of marketing.

Noy a debate over nickies vs scott casslers cylinders. More of what material would be best to make cylinders out of. More afordable cylinders people could actually afford and run with stsndard mahle pistons with ring pack fot chrome bores. Not a 50-75% markup .
1/2vw was supposed to be afordable 40hp and ive seen everything yet to be afordable.
Prety sad for an ultralight you spend half as much on the engine you do on the whole plane.

I happen to have turning capabilities and good relations with melinnium technologies. Just trying to bring something afordable to the people who would want it. But with everyone arguing over nickies, scotts cylinders, ect i could almost care less and you guys go pay 3 times as much for their cylinders than what they should actually cost.
 

TFF

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Most of its access and volume. You make a thousand cylinders in a year, options open up. You make 50, raw materials is whatever is off the shelf to you. One you can play with technology and one your stuck.
I noticed lots of billet parts showing up on the brand helicopters I work on. Use to be cast and forged parts, but it became cheaper to a CNC it all than to get someone to cast 50 a year, if they had someone who would cast it at all. I knew someone who built a house from the test pour molds for concrete manufacturing. Free materials. Kind of ugly if you were paying for it. For free out in there be country, not bad.
 

lelievre12

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The main benefit if Nikasil is the corrosion protection when the engine is not being used. Corrosion kills more engines than wear does. Particularly if you only fly once every other week or don't fly at all over winter. If you fly regularly and/or squirt some Marvel oil in the cylinders when storing then Nikasil is not needed.
 

osprey220

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Hi slociviccoupe,

Sorry for the cast/billett disagreement. I hadn't read too much about Nickies, just talked with the company, with Scott, and I've held them in hand. And this thread started with the question "Does anybody know of a successful combination using the cast aluminum nikasil cylinders on a type 1 vw??"

My experience and knowledge is limited to Nickies, Scott's and QSC (and I think Aerovee and GP used to resell the QSC cylinders). Nickies and Scott's both have flawless reputations for reliability and wow - in hand they look and feel amazing. Ive never heard a good thing about the QSC's cylinders.

The difference in reputations fits in with what I've read about strength of billet vs cast - but that's just academic and I've not watched them being made.

If you are looking to make cylinders - Cheers! I think thats a great idea! Clearly with the prices of the alternatives there is a lot of room for new suppliers and the market is hungry. While the aviation market is minuscule, there are a lot of street folks that lust for Nickies but aren't willing to pay $3700.

Regarding which material to use - I have no idea. There are a lot of exotic alloys that do a better job of maintaining strength a high temperatures. But your best bet would be to talk to Scott.

Cheers,
Owen
 

slociviccoupe

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To everyone replying no hard feelings. Thanks for the replies. And it seems finding the right alloy is going to be key. Very unlikely scott or ln engineering going to reveal what alloy they are using.
But material cost, machine time, and plating are obviously going to dictate cost.
Replating a 2 stroke cylinder from melinnium technologies usually runs me 150$ each. Havent checked price of material but guessing an 8" diameter log of 6061 t6 would be about 200$. Havent toolpathed it yet to get machine time.

Certain processes like water jet cutting the center out will reduce mill or lathe time and drive down cost. There also are options of having another company centrifugally cast or even forge them but outsourcing drives up cost. Even an extrusion die could be made and eliminate having to machine un necessary material out of the center for the bore.
 

WonderousMountain

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Slo Civic Coupe,

I'm not the expert here, but
were I to do this from billet,
It would definately start out
as pipe stock, not a rod blank.
 
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