1000cc two stroke

[DEATH_INC.]

Just to clear up one little thing, a normally aspirated two stroke cannot share a common crankcase between two cylinders, the reason for this is that the thing that makes it all work is the piston pushing the air/fuel mixture outta the crankcase on it's downwards stroke. This is why you must have a reed valve, a rotary valve or the piston closing off the intake (piston port I think that's called). The amount of crankcase compression is determined by the size of the piston relative to the crankcase size, and the amount of piston travel downwards before the transfer ports open.The capacity of the casing doesn't matter a lot, the area under the piston will take care of the air/fuel you need.

You can't join two CR cases side by side unless you can key the cranks together, a one piece will not be possible as I'm sure the CR cases join vertically, so no way to get the crank in there. Better to make yer own one so you can join it horizontally and have a one piece crank.
Prolly the easiest way is like the RZ500, two cranks one in front of the gearbox and one above it, both driving on to the clutch.(gears on the RZ from memory)
This sounds like a fun project....

[Sollyboy]

There was a rz500 with rz 350 barrels and top ends fitted a few years ago, apparently it was really fast , but being a 2stroke 700 it would be, I love the sound of a big 2 stroke

[speedpro]

I said "Pretty typical setup for the BIG turbo diesel 2-strokes as in ships etc. They are in-line engines though.!"

Nope - two stroke diesels dont have to be in-line. You must have seen GM 6,8 or 12 cylinder two strokes in Vee configuration, eg 6V71 or 8V71.

The engine I saw and was working around was about 3 stories high, in-line 9 cylinders, triple turbo, single exhaust valve per cylinder. You could easily walk down the intake manifold stooped over a bit. All three turbos fed the manifold which in turn fed all 9 cylinders. It had an open crankcase, idled at 2rpm, a redline of 200rpm and max power at 180rpm. The rear 3 cylinders could be run seperately from the other 6 when just moving round in port.

Pretty sure I would have noticed another bank of cylinders.

[speedpro]

What about a flat twin. 2 cranks side by side, geared together so contrarotating and therefore no torque reaction. I'm thinking it would need a counterbalencer to counter the crank forces at right angles to the bores. Pistons would be at TDC at the same time so would balance each other out. sort of like a BMW only better. The crankshafts could be enclosed seperately or together, it wouldn't matter as both pistons would be travelling up or down their respective bores at the same time. Actually probably better seperate just in case of a blow-up. You could even run a 2:1 chamber if room was a problem.

BIG bang 1000cc 2-stroke twin. The transmission could be a problem plus it would need a 90deg turn somewhere.

[Mr. Peanut]

Why don't you just use a jet-ski engine?

[Ixion]

What about a flat twin. 2 cranks side by side, geared together so contrarotating and therefore no torque reaction. I'm thinking it would need a counterbalencer to counter the crank forces at right angles to the bores. Pistons would be at TDC at the same time so would balance each other out. sort of like a BMW only better. The crankshafts could be enclosed seperately or together, it wouldn't matter as both pistons would be travelling up or down their respective bores at the same time. Actually probably better seperate just in case of a blow-up. You could even run a 2:1 chamber if room was a problem.

BIG bang 1000cc 2-stroke twin. The transmission could be a problem plus it would need a 90deg turn somewhere.

One crankcase chamber for two cylinders? How you going to ensure that each transfer port gets half the mixture ?

[Ixion]

I wonder if anyone's ever built a two stroke Lanchester engine?

Horizontally opposed, piston heads facing each other, with the combustion space between them, and a crank at each end . Would have to be big bang firing but the induction and exhaust should work OK. And that would be a BIG bang.

[kevfromcoro]

Bit of topic ,,but still bike mods.
Was out the other day ,and spotted a couple of trikes.caught up with the owners .a older man and lady just out riding.
the trikes were both suzuki 1500.
apparently there is a guy in Taupo who converts bikes into trikes.
these were shaft models with a shortened holden diff in them..
looked quite kool accuatly
comfy and lots of room to store your goodies

[Mr. Peanut]

I wonder if anyone's ever built a two stroke Lanchester engine?

Horizontally opposed, piston heads facing each other, with the combustion space between them, and a crank at each end . Would have to be big bang firing but the induction and exhaust should work OK. And that would be a BIG bang.

I don't think the British had enough time to make something that idiosyncratic, another 30 years of motorcycle market dominance and who knows? They made the Ariel square snore after all.

Bit of a waste of space? Why not just make a parallel twin.

[Ocean1]

One crankcase chamber for two cylinders? How you going to ensure that each transfer port gets half the mixture ?

Most 4T multi cyl single carb engines seem to manage ok...

I wonder if anyone's ever built a two stroke Lanchester engine?

Horizontally opposed, piston heads facing each other, with the combustion space between them, and a crank at each end . Would have to be big bang firing but the induction and exhaust should work OK. And that would be a BIG bang.

What'd be the point? Good curiosity value but it'd be heavy, with the mass at the ends. And bloody long, for/aft mounted?

I built some weird steam toys when I were a nipper, still got a couple burried in the shed somewhere. One's an elbow engine, two six-shooter type rotating magazines mounted at 90deg, with common 90deg bent pistons in each bore pair. Looks bazarre but makes lots of torque, serious revs too.

[DEATH_INC.]

Why don't you just use a jet-ski engine?

I meant to mention it before, guys in the US use big two stroke snowmobile engines...

[Ixion]

We know that. Look, if we wanted PRACTICAL we'd use four strokes .

[DEATH_INC.]

Yeh, I know that
Just thought I'd throw it in there.....I'm all for the idea of building something from scratch.
The question is really whether the machinist / designer is up to scratch building and designing a crankcase and crank. With the common-crank twin you'll need to make up cases, with a twin crank you could prolly boogey up something using the cr bits. If you're gonna use a common crank the engine will be nearly as wide as a four as you gotta run two near complete engines side by side, whereas if it's a (what do you call a twin crank v twin again??) it'll be longer or taller. As Speedpro (i think it was ) mentioned a twin crank has the advantage of being able to blow up 1 cylinder/crank and hopefuly salvaging the other....
Personally I'd like to see the single crank option it'll be a more compact engine

[speedpro]

One crankcase chamber for two cylinders? How you going to ensure that each transfer port gets half the mixture ?

With the suggested layout both pistons rise in both bores simultaneously, all the transfer ports open simultaneously. In fact EVERYTHING in each cylinder happens simultaneously. Both pistons move out and both pistons move back at the same time, but in opposite directions thus cancelling out any reciprocating forces. The beauty of this arrangement is that the crank would only need to be big and heavy enough to handle engine running forces and there would be no requirement for crank counterbalance. There would be a reasonable imbalance acting perpindicular to the bore's centreline which would need a balance shaft or somesuch to counterbalance.

[Ixion]

Common crank shouldn't need to be much wider than a 4T twin with a centre bearing. Needs the end shafts pressed out of the two cranks, and a common joining shaft machined to join the two together and hold the centre bearings and seals (will be a bit wider than the 4T , cos of the seals, and you really need two bearings not one). Still narrower than a four though.

If one were designing from scratch one could maybe offset the cylinders to make up some of that, but that's a bit hard in a fabricated jobby.

Centre split is much better for this purpose than horizontals split, because the runout tolerances on a centre split with a chain/belt primary drive don't have to be super critical, ball race mains can take up a bit (I'm talking point of a thou here) of misalignment. The old Briddish twins were never truely in line, Ive seen the main bearing housings out by near a millimetre.

Trouble with twin crank engines is , unless you keep them really closely tuned, they end up trying to run at different revs, which causes lots of issues for whatever you are using to connect them.