BTW, the mini-petters I sold Sid DO have the aluminum pistons and they run quite smoothly. Many dealers and enthusiasts have been advocating cast iron pistons for the Lister and the Petter engines. If cast iron pistons are so great why doesn't your car and truck have them? Simply because time has proven the aluminum pistons to be superior. This applies to reciprocating weight, strength, and thermal expansion characteristics. Even the R.A. Lister Company changed to aluminum pistons for the higher speeds of the 8/1 and the 16/2. Only the 6/1 and 12/2 used cast iron pistons. Guy, what is your take on this?
weight of reciprocating components or non reciprocating components isn't really an issue by and of itself.
for example, BSA A10 650 cc parallel twin was an alloy engine with an iron head, later models went for an alloy head, it wasn't to save weight.
as far as the listers go whether the engine weighs 600 or 700 or 800 lbs doesn't really make any difference to a static engine
yes different applications like avaition diesels weight matters, but not to us.
balance is also not really related to weight, look at locomotive turntables, they could weigh 2 or 3 hundred tons all up, and yet one man could still easily crank them around.
so
1/ weight isn't an issue.
2/ strength isn't an issue (provided you have enough)
what other factors are there? particularly alloy vs cast iron.
cast iron vs cast alloy there are similar costs, spun or billet alloy is different costs.
machining alloy is cheaper and faster than machining cast iron
in some applcations alloy will conduct heat better than cast iron, and that can be important.
however, we are talking about a piston in an internal combustion engine, so we are most interested in a different property of metals.
their ability to absorb free electrons, the greater this ability, the more they inhibit or slow combustion.
BSA went with the alloy head and that allowed them to raise the compression ratio.
Lister put an alloy piston in the faster revving singles, because the duration of the ignition event was shorter at higher RPM and the heat of compression was greater yet the fuel was the same, so the alloy piston slowed the flame propogation.
an alloy piston will absorb more free electrons at cranking too, and make starting that much harder for any given compression ratio / head design / fuel type / fuel metering - timing setup
so
Fact 1
Choice of combustion chamber components materials has more to do with absorbtion of free electrons than anything else (provided of course other qualities are satisfied such as strength etc)
Fact 2
Lister managed to build these engines*** for fifty years and balance them properly at the factory.
*** 650 rpm 6/1- we _must_ exclude 8/1, and clone 12/1 etc, they are NOT the same animal
Fact 3
The Lister 6/1 was multifuel, the 8/1 wasn't. (or was, but far more limited) so an alloy piston in a 6/1 will screw this up too...
Fact 4
The lister had chromed bores, they weren't exposed during TDC but they were during compression and combustion, and this alters flame speed a little too.... from the MECHANICAL viewpoint chromed rings in plain bores is just as good, many a 2 stroke with chrome bores can be economically rebuilt with chrome rings and a rebore, but you ALWAYS have to adjust the timing and jets ever so slightly afterwards... the Cagiva / harley 2 strokes were a classic example.
Fact 4
A listeroid is not a lister.
Speaking personally here I think we have two camps, those of us like me who have a genuine lister and have never seen a listeroid, and those of us who have a listeroid and have never seen a lister. I believe there are a few who have seen both, but they are not to the best of my knowledge mechanical engineers.
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An observation.
I've read your comments, you have CNC and so on so you are clearly a mechanical engineer, and it appears to me you are setting yourself the task of trying to reverse engineer a genuine lister without actually seeing one, in much the same way people do to avoid patent and intellectual property violations, in short, you are hobbling yourself significantly, for no real patent or IP purpose.
My advice to you would be grab a flight or buy your own genuine Lister, then you have a baseline, then you can draw up a table of differences (___LOT___ cheaper than an new CNC that you might not need) because at the end of the day Lister did it right, so right they could not (__NOT__ did not or not bothered to) significantly improve on the design of the 6/1 for fifty bloody years.
I cannot tell you the precise weight or centre of mass or dimensions at 15 degrees celcuis of a genuine Lister 6/1 piston, (the only one I own is still inside a working motor) and I certainly cannot tell you an accurate materials composition of it.
Until and unless you have that data, you are trying to re-invent the wheel, having only seen a cheap copy that someone else with different priorities and agendas to both Mr Lister and yourself knocked off, which may not be the same as the next batch they knock off.
You need a genuine running Lister 6/1 to strip and play with, and a non runner to pull apart for materials analysis so you know what grade to cast iron to pour for each component. see my successful weld of frost damage on a Lister cast iron barrel with a bog standard steel mig wire... my hunch was right, Lister cast iron was towards the malleable end of the scale, my hunch says listeroid case will be nearer the other end of the scale, because it will be poured from generic scrap.
You almost certainly have a Bridgeport or Cincinatti there is you have any CNC, so make a coffee and go and look at the cast iron on them, don't look at a knee mill or whatever the machine is, look at the material, then look at your listeroid, not as a listeroid, but as material.
One final comment before you go and try and knock up an alloy piston.
20 bucks says the genuine lister cast iron piston is cast and turned on a lathe to be round.
You going to make that same bet that an alloy piston of those dimensions is round and not oval over the gudgeon / wrist pin structure at room temp? coefficients of thermal expansion are different on alloy too.
So bottom line here is if you paid me a thousand bucks as a consultant on this problem my advice would be drop everything until you have looked in depth at genuine lister and established a bet-your-life-on-it baseline to work from.
I have a genuine start-o-matic you're welcome to come over and strip and rebuild and measure and document as much as you like, genuine offer.