The Bucket Foundry

[WilDun]

With this HCCI the piston can now be ceramic, a heated piston might be a good thing (and head), how do you work with ceramic? This ceramic in my hip is some sort of ceramic matrix being a little bit flexible, so I'm told and light weight.

We used to have a ceramic dinner set. made in USA, called "Corelle" from memory and I was very impressed with them, they were very thin and lightweight but you could drop them and they would bounce where a normal plate would shatter.
I believe that they are still on the market today but obviously they are slightly flexible and springy and it might be an idea to find out just how they are made - they tried to make them in England as well but they obviously weren't told exactly how it was done, so they were dropped (not literally of course ).

Update :- I woke up this morning and remembered that the name of the company was "CORNINGWARE",

[lohring]

Zirconium https://en.wikipedia.org/wiki/Yttria...lized_zirconia has been used in dental crowns and bridges for a while. That is actually a high stress application due to the very small sizes. The advantage over previous porcelains and ceramics is that it behaves more like metals and is crack limiting. I have never had a zirconium crown or bridge chip or break, unlike previous porcelains. It has been used in jet engines and knife blades as well.

Lohring Miller

[lohring]

More details are available at http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4026739/ Filter out failures in the relatively weak porcelain that's applied to the zirconia framework for appearance. The base zirconia framework is very durable. The dental crowns are fabricated by cad/cam machining in the sintered state. This compensates for shrinkage when the zirconia is fired. After that, even machining with diamond burs is difficult. The particular "alloy" seems to be important. Still, I see similar zirconia ceramics replacing metals in a lot of applications in the future.

Lohring Miller

[Frits Overmars]

More details are available at http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4026739/ Filter out failures in the relatively weak porcelain that's applied to the zirconia framework for appearance. The base zirconia framework is very durable. The dental crowns are fabricated by cad/cam machining in the sintered state. This compensates for shrinkage when the zirconia is fired. After that, even machining with diamond burs is difficult.

Ceramics cover a very extensive field. They're not all white, they're not all brittle, and what may surprise you the most: they're not all bad heat conductors.
I used to play with the idea of baking my own cylinder from a type of ceramic that is an even better heat conductor than aluminium. Moreover, it would be lighter, have a far lower coefficient of expansion, be much more dimensionally stable and hard enough so that it wouldn't need any form of bore coating.
The problem that eventually stopped me from trying was that I could not think of a way of tapping any screw threads after baking. For a moment I even thought about baking the studs in, but since such a cylinder would shrink about 30% in the oven, I thought better of it.

[WilDun]

I used to play with the idea of baking my own cylinder from a type of ceramic that is an even better heat conductor than aluminium.

You could probably have baked in studs instead (if they could have withstood the temperatures of course!) - but then they if they ended up a little brittle, tempering them would have been a nightmare
I remember that some companies were experimenting with 'silicon nitride' ( which I read was silicon pressed into shape and nitrided) for pistons and liners - probably this process would have kept temperatures much lower.
That was somewhere back around eighties or nineties - dunno what happened there, it all seemed very promising at the time (and still is it seems) - guess that's what you have in your hip Neil?

http://accuratus.com/silinit.html
https://www.youtube.com/watch?v=FDUNsRRHVPo

[Flettner]

Thankyou Lohring Miller, I have no idea about ceramic's (apart from tea break) how they are made? I'm assuming you can't work it like metal on a lathe, I guess it get's sintered in a die. Anyway for now I'll just cast an aluminium piston.

[Frits Overmars]

Thankyou Lohring Miller, I have no idea about ceramic's (apart from tea break) how they are made? I'm assuming you can't work it like metal on a lathe, I guess it get's sintered in a die. Anyway for now I'll just cast an aluminium piston.

I don't know much about ceramics either but I understand they are moulded and in their 'green' (= before baking) form you can modify them at will.
Cast aluminium pistons can be every bit as good, if not better than forged pistons. But I don't expect they will be gravity-cast. And centrifugal casting may be a bridge too far. But steel pistons are making a revival, and for HCCI their lower heat conductivity may even be an advantage. Below are some pics of a modern steel foul-stroke racing piston. And if you are going to use your hypocycloid piston rod, things will become much simpler and you might end up with a giant steel nail.

[Grumph]

Impressive saving on weight in the pin bosses due presumably to the higher tensile strength of the steel. More gain with the shorter pin too.
I'd have thought that the steel Vs alloy thing favours steel in the larger bore sizes where you can do something spectacular like that one - but alloy where it's a small bore and to an extent, small end width governs what you can do.
Must be a crossover point I'd have thought.

Neil - There's a guy down here who was squeeze casting his own pistons some time back with very good results. I could probably find him again if you want to talk to him.

[Flettner]

Impressive saving on weight in the pin bosses due presumably to the higher tensile strength of the steel. More gain with the shorter pin too.
I'd have thought that the steel Vs alloy thing favours steel in the larger bore sizes where you can do something spectacular like that one - but alloy where it's a small bore and to an extent, small end width governs what you can do.
Must be a crossover point I'd have thought.

Neil - There's a guy down here who was squeeze casting his own pistons some time back with very good results. I could probably find him again if you want to talk to him.

Hey, you know me, I'll talk to anyone.

[Grumph]

Hey, you know me, I'll talk to anyone.

I'll see if I can track him down. I like Frits large nail comparison, LOL.

[Flettner]

Just screw on a piston. No gudgin pin, small end bearings or gudgin pin bosses, just a few webs under the piston and it's short because the exhaust ports don't go to the bottom of the cylinder. All things being equal this piston should not even touch the bore, if the epicycloid crank is set up correctly but I will get the bore coated anyway if for no other reason than to offer a good wear surface for the ring.

[Frits Overmars]

Just screw on a piston.

Yep. But there's one problem you'll need to solve: the ring gap can't be just anywhere, not if you wish to keep the piston ring in one piece.
How can you make sure that the piston doesn't unscrew itself, and that after unscrewing the piston and screwing it back on, the ring gap will still be in the same place?

I haven't found a solution yet, but I did think of a way to circumvent the problem: Using a split guidance for the epicycloid con rod will allow you to make the piston and con rod in one piece.

[ken seeber]

Getting close. Ignition on. Plug lead cap done. Carb on.
Was thinking of an additional flywheel, remembering that the CR will be high when the cylinder is low, corresponding to idle & low load/speed conditions. Fletto independently suggest this today, so decision made. So, when to the off-cut bins and there it was, just waiting. Bit of a simple facing off and boring op and almost done. Occasionally there IS some satisfaction in being a bit of a hoarder.

[husaberg]

Yep. But there's one problem you'll need to solve: the ring gap can't be just anywhere, not if you wish to keep the piston ring in one piece.
How can you make sure that the piston doesn't unscrew itself, and that after unscrewing the piston and screwing it back on, the ring gap will still be in the same place?

I haven't found a solution yet, but I did think of a way to circumvent the problem: Using a split guidance for the epicycloid con rod will allow you to make the piston and con rod in one piece.

KISS, Jam nut, it works for rose joints and tie rods.

[ken seeber]

But steel pistons are making a revival, and for HCCI their lower heat conductivity may even be an advantage. Below are some pics of a modern steel foul-stroke racing piston. ]

These are impressive. Look like investment castings made from a 3D printed sacrificial cores, judging by the witness of the series of lines. Agree, it might be the go for HCCI, but for the fact that it needs a skirt for port sealing. Perhaps one could do a composite design with a very thin skirt (eg 1 mm wall extruded aluminium tube). Easy to say, but quite a few issues to be addressed.