OT: Engine Firing Order etc.

[newshound]

Other way round? Vincent twins have two cylinders per throw. Hence the lovely exhaust sound!

[bert]

In article , Cursitor Doom writes

I suspect it might offer more protection in a collision than the original tin can on wheels.

[Bob Eager]

Another issue with the original (which I still prefer) was the sharp outside seams!

[harry]

The Yanks used a radial engine in some Sherman tanks.

[T i m]

And both of mine sound lovely. ;-)

It's funny, being an engineering (rather than 'arty') type you would have thought I would have considered the Yamaha 900 Diversion I borrowed for a week (when my R100RT ate it's clutch splines) to be the_ideal_solution. Everything worked perfectly and smoothly (even on this high mileage model), it pulled like a train, was well planted and nearly indestructible ... but I only rode it twice in the week I had it because it had no 'character'.

It turns out that in spite of it being the least reliable bike I have ever owned, there was something about the old Airheads that really floated my boat.

Now, if I was unfortunate enough to need to commute any distance on a bike, I don't think I'd choose the Airhead (but not sure what else I would use).

For local / traffic stuff it could be my other twin, the CB250 Nighthawk. ;-)

Cheers, T i m

[T i m]

My Messerschmitt KR200 has two sets of points but because it's a 2/, the points are for forward and reverse. ;-)

Did I read right in that some cars (that do the stop-start thing) use the starter motor for the initial start of the day and then the generator / dynamo(?) for all starts after that?

Again, not a new idea as the 'Dynastart' on the Messerschmitt was both a starter motor and dynamo. ;-)

Cheers, T i m

[Vir Campestris]

They put radial (not rotary) aircraft engines in Sherman tanks.

Andy

[Vir Campestris]

AIUI there are two types of 5 - one with a crank every 72 degrees, and one that looks like a flat crank 4 almost - except that the 5 are off to one side of the plane slightly, and the centre piston is just over 90 degrees from any other.

But I don't have any good references, so I haven't fixed that article.

There are definitely two types of V8 - flat plane and crossfire. The flat plane has a 4 cylinder's crankshaft, but with a piston for each ban on each big end. The crossfire looks like a cross from the end, with a crank every 90 degrees.

I want an inline 6. I've done the arithmetic, and they balance everything.

Or a RR Merlin :)

Andy

[Dave Plowman (News)]

As I said before, the angle of the V also influences firing intervals. Most V8s have a single crank throw shared between cylinders - 1&2, etc. The most common angle is 90 degrees which gives irregular firing intervals

- hence the V8 'beat' A 60 degree gives even intervals. Or a 90 degree with a flat plane crank.

Yes - although the longer crank can cause problems of its own.

A good engine in its day - but things have rather moved on since then. ;-) Even in supercharged form and with very high octane petrol, never achieved

100 bhp/litre.

[tony sayer]

I had a bad wallop in a Mini back in 1974 spilt every bloody seam on the body!

After seeing that and surviving it, no more Minis ever since!

[Halmyre]

Just about every engine uses 1-3-4-2; this is one of only two firing orders possible with a conventional in-line UDDU crankshaft:

--| |-- |--|--|

The other is 1-2-4-3, which only Ford use nowadays.

[The Natural Philosopher]

1234 1342 1423 1324 1432

these are all possibles.

Because UDDU is not the only crankshaft you can make

[Halmyre]

That's why I said 'conventional'.

[NY]

What other types of crankshaft have been used in 4-cylinder engines. Has anyone made a crankshaft with every cylinder rotated 90 degrees with respect to its neighbour?

If UDDU is 0, 180, 180, 0 degrees with respect to the first cylinder, has anyone used 0, 90, 180, 270 or any other similar variant? Or are all practical crankshafts made with only 0 and 180 bearings (in some order), and no 90 or 270?

As a matter of interest, for a UDDU crankshaft, is there any advantage of

1342 over 1243, given that both have one pair of consecutive cylinders (34 in the first case, 12 in the second). I realise why 1234 is the worst possible firing order, because of creating standing waves.

How does the smoothness of a V engine vary according to the angle of V? An inline is one extreme and a flat-4 boxer is the other extreme (effectively a

180 degree V) but between those extremes, is there any advantage of one V angle versus another, other than that the flatter the V the lower the engine height (but the wider the engine).

[Halmyre]

Yes, see

I would hazard a guess that when you've got an engine with a lump of gearbox at one end, 1342 is smoother than 1243 (1 being the front of the engine). although that doesn't explain why Ford used 1243.

[harry]

There are two sorts of "flat" engine, "boxer" and non-boxer. The boxer engine has four crank pins and the pistons on opposite cylinder move away and towards the crank together. They are very vibration free.

The non-boxer engine only has two crank pins and are more unbalanced.

Crankshafts are made "flat" because anything elese can't be forged in a single operation.

[Halmyre]

The non-boxer flat is just a 180 degree V. However, that makes me think - what if you were to bend a boxer engine to 90 degrees or whatever? I'm trying to picture the shape of the crank but it's too much for a Sunday morning.

[NY]

I'd forgotten about the non-boxer inline engines. Yes I can imagine that they will vibrate a lot more.

My dad had a Citroen GS with a flat-four engine. It was very smooth (so it was probably a boxer) but then it needed to be because the engine was only

1200 cc and had to rev very fast to get any power. I can remember it was normal to see about 4000-4500 rpm on a motorway in third (he went for the C-Matic transmission which was a three-speed automatic with torque converter, but the gear-changes were made manually with a conventional gear lever rather than automatically. It was weird to change gear without having a clutch.

Yes, a 3D crankshaft, with one crank bearing sticking up from the plane and one sticking down, would be more difficult (impossible?) to mould and to cast.

[NY]

Do V engines normally share crank pins (one piston from each side of the V) rather than having a separate one for each piston as in inline or boxer? Didn't know that.

[Dave Plowman (News)]

It's common on V8s. Hence the angle of the V determining the firing intervals. It's why the most common - 90 degree - burble. The firing intervals aren't regular. Which also makes it tricky to fit four carbs.