barrel coatings

[gofastclint]

I have noticed many companies offering various ceramic coatings for aircraft cylinders. I can see a few major benefits in using these coatings but would like to hear the opinions of someone who isn't just trying to sell it. Has anyone used it and noticed a big difference?

 

On another note, I see ceramic coatings offered for exhaust systems, with claims of drastically reducing the exhausts outside surface temp.... wont this affect using heat and wont it take longer to de-ice the carbs?

 

 

[facthunter]

Ceramic coatings.

 

Ceramic coatings generally INSULATE some heat in. They are not good conductors. Heat dissipation is a complex thing and surface finish/colour have a bearing on it. Thick coatings are not desired IF you are trying to get rid of heat. Nev..

 

 

[Vev]

There has been some previous discussion on exhaust insulation and ceramics were in the mix.... it doesn't answer your question but may help add some additional thinking and context.

 

http://www.recreationalflying.com/forum/jabiru-users-group/10826-exhaust-insulation-wrap.html

 

Cheers

 

Jack

 

 

[Harthy]

ceremic coatings

 

Ceremic coatings have been around for a long time now, and are widely used in high performance and racing engines.The major problem with ceremics is that it is brittle. Ideally an engine totally manufactured from ceremics would be be way to go. The hotter an engine can run the more thermal efficient they are, and then there would be no need for a cooling system.

 

Ceremic coatings on pistons and valves achieve outcomes. But I have not heard much about ceremic coated cylinders. I too would like to hear how they go.

 

Piston rings need to seal well with the cylinder wall so we can have adequate compression for combustion to occur. Oil that is trapped in the hone marks on the cylinder wall aids in sealing the rings and lubrication. This is why a glazed cylinder will burn oil. I am interested to hear how ceremic cylinders over come this problem

 

Cerremic coated exhaust systems are generally done for cosmetic reasons. They always look great and don't rust.

 

Harthy

 

 

[facthunter]

Coatings where?

 

Think GFC is talking about doing it on the outside, which I don't recommend, as the cylinder will run hotter, the opposite of what you want. Nev.

 

 

[gofastclint]

"Ceramics" can be used for so many things.

 

Ceramic coatings in general keep heat in but another great use is in reducing friction.

 

On the outside of a cylinder is a bad place as it keeps the fins from dissipating heat properly.

 

The coating I am talking about is a "nickle-ceramic-carbide" i used the old version of it in motorcycle racing in an air cooled head in the bore. the motor was a 100cc two stroke, the rings were replaced yearly and i sold it after 6 years, the bore was still fine, just wondering if anyone used it in aircraft engines?

 

 

[gofastclint]

most American magazines have the add, "nickle bore 5 year warranty 150,000 barrels strong"

 

 

[facthunter]

Electroplated or diffused.

 

I saw a cyl with a nickel bore advertised in a mag.today, but I think it was a repair to a steel cylinder.

 

The nickasil coating, which is different in the way it is applied is commomly used in aluminium bores, usually with 2-strokes. A similar coating is used on rotax 4-strokes. It is hard, long wearing and doesn't corrode when the engine is not in use. Nev..

 

 

[gofastclint]

I saw a cyl with a nickel bore advertised in a mag.today, but I think it was a repair to a steel cylinder.The nickasil coating, which is different in the way it is applied is commomly used in aluminium bores, usually with 2-strokes. A similar coating is used on rotax 4-strokes. It is hard, long wearing and doesn't corrode when the engine is not in use. Nev..

It is a great repair coat, but it would also add more life to a new bore. like when you order new barrels, send them off for a coat new. if it doubles the life of the barrel an is less that a 1/4 of the cost of a new one, you would be saving a lot of money.

 

 

[facthunter]

Nickel coat new Cylinder.

 

GFC, that doesn't make ecomomic sense. with Lycoming/Continental motors. I wouldn't be grinding metal out of a new cylinder, just to bring the size back to standard with a nickel coat. (which you have to do as the range of piston sizes isn't availableto go undersize).You have to use special ring material (Chrome isn't suitable) The cyls will last over 3000 hours anyhow, bore-wise, and other things can go wrong with them too (head cracks).

 

It might be a proposition with the Jab. cylinders where smaller pistons are available easily, and there are some bore glazing and corrosion issues in some instances. The cylinder would have to be heat treated after plating to avoid hydrogen embrittlement. That is a standard process in aviation circles, but frequently overlooked in the general world. Nev

 

 

[gofastclint]

GFC, that doesn't make ecomomic sense. with Lycoming/Continental motors. I wouldn't be grinding metal out of a new cylinder, just to bring the size back to standard with a nickel coat. (which you have to do as the range of piston sizes isn't availableto go undersize).You have to use special ring material (Chrome isn't suitable) The cyls will last over 3000 hours anyhow, bore-wise, and other things can go wrong with them too (head cracks).It might be a proposition with the Jab. cylinders where smaller pistons are available easily, and there are some bore glazing and corrosion issues in some instances. The cylinder would have to be heat treated after plating to avoid hydrogen embrittlement. That is a standard process in aviation circles, but frequently overlooked in the general world. Nev

Very true, I was talking about a Jab as their heads are rather cheap in price compared to the rest.

 

I never new hydrogen embrittlement was the reason behind the heat treating of new bores, that is something I will read up on cheers.

 

As they say, "if you are not learning you are dying".

 

 

[facthunter]

Hydrogen embrittlement.

 

relates to plating and is ANY part (not just cylinders). CASA have an extensive amount of information on their website. Sorry I do not have the link, but that is a reliable source of info on this matter. Nev..

 

 

[Guest Maj Millard]

Hydrogen embrittlement used to be a problem under chrome if the part wasn't cleaned/prepared properly prior to chroming. One of the reasons you didn't see many chromed metal ripcord handles in the old skydiving days !!.............