Ducati in MotoGP

Originally Posted by philc2000

Wasn't Melandri in the D'antin team with Hodgson last year?

No.

T'was Xaus!

aye - I new it were some bugger with long legs who kept falling off - Melandri was in a Yamaha team

Of course, it's not the first time that Ducati have been in the "big class" of GP racing. They had a 500cc Desmo twin in 71/72 and I believe that Ing. Taglioni originally used the then new 750cc v-twin crankcases before reverting to a parallel twin layout. Phil Read scored points on it in (I think) '71 although Mike (Hailwood) was the rider that Ducati were said to want. Mostly though, Bruno Spaggiari rode it (Known as "Spag" to us younger Jessops, in a silly reference to the Spagthorpe which Uncle Edgar was alleged to have ridden).

Coincidentally, the machine developed 72 bhp at 12,000 rpm which is rather similar to an SV650 I think - and it was one of the first GP bikes to have a 6-speed gearbox. I have often wondered whether, because of its 750 origins, it might have had the V-twin firing order - or "big bang" as you lads call it - but although I was allowed a ride on the Seeley-framed version in '79, before I started with the Pantah, I had never experienced a big-banger so I didn't know what I was supposed to be feeling!

Anyway, in '79, it was already long a museum piece and overtaken by the two stroke screamers of the day but that is another story!

[ophic]

"big bang" is a reference to the firing order of an IL4 being closer to the engine pulses of a twin. You can't have a twin with "big bang" cos it sort of already is. I'm told the theory is that you get two cylinders to fire close to each other (not at exactly the same time) and this apparently aids traction, due to the bigger gap between large engine pulses allowing the tyre rubber to accommodate better. Or something like that anyway. It's not quite the same as v-twin firing order.

Interestingly, if the new 800cc engine restrictions come into place, won't that push the revs up in order to make more power? If the revs go high enough, then they'll need a "big big bang" firing order in order to achieve the same effect - ie all 4 cylinders firing like a single...

[fizzwheel]

Originally Posted by ophic

"Interestingly, if the new 800cc engine restrictions come into place, won't that push the revs up in order to make more power? If the revs go high enough, then they'll need a "big big bang" firing order in order to achieve the same effect - ie all 4 cylinders firing like a single...

Yes it will, revs will go up, there is some talk already of F1 technology being used. But then look at what happened to Aprillia when they got Cosworth to help them out, they made a bike that nobody could ride...

Originally Posted by ophic

I'm told the theory is that you get two cylinders to fire close to each other (not at exactly the same time) and this apparently aids traction, due to the bigger gap between large engine pulses allowing the tyre rubber to accommodate better. ...

That's how I understand it as well.

Well done Ophic. You reminded me of an article in a Spanish bike mag last year.In this they showed via a bike wheel graphic the standard power pulses per revolution of the rear wheel. Very clever stuff and the Big bang thang does indeed provide more.

Originally Posted by ophic

"big bang" is a reference to the firing order of an IL4 being closer to the engine pulses of a twin. You can't have a twin with "big bang" cos it sort of already is.

I don't want to appear a smart @rse but although that's nearly right, it misses a bit, and it has to do with crank spacing. I'm pretty sure that the first "known" racing engine with "big-bang" was the Honda NSR500 V-4 two-stroke, and Mick Doohan credited as the man who proved it worked. It originally ran in "screamer" mode - ie evenly spaced firing sequences for high rpm and a well-balanced engine, but based on experience with other V engines, the engineers realised they got better drive with uneven pulses (although a lot more vibration). So it landed up with bizarre crank spacing of something like 117 degrees and two unevenly spaced big bangs per revolution instead of four evenly spaced smaller ones - think of it as b-bang instead of bang-bang.

If you take a 4stroke engine, you get half as many firing impulses per revolution compared to a 2 stroke, and on an in-line engine, the usual thing is a flat crank (360 degrees for an IL2, 180 degrees for an IL4) giving you symetrical impulses. It's your typical 1342 car sequence firing order.

What I think Camilla was saying is that maybe the 500 Duke twin ran an asymmetrically spaced crankshaft - and instead of one firing every revolution(ie typical 4 Stroke bang-bang-bang etc), it ran with two-firings every other revolution - ie, like a V-twin.

I stand to be corrected, but I think Yamaha have made assymetric crankshafts for their MotoGP and BSB engines - they fire with the uneven pulses of a V engine and every other revolution like it was a twin. Sort of B-Bang (where each B is two cylinders going off), miss a revolution, B-Bang, miss a revolution, and so on. It's not just two big evenly-spaced bangs!

But, like I say, I stand to be corrected so if there's an engine designer in the house.......

Originally Posted by El Boccadillo

Stuff

I was going to say something along those lines, though alot less detailed.
As for the Yamaha timing, from what I've read they've looked into doing it something like having 2 cylinders very slightly offset and then offsetting those two ba-dum ignitions by a little more so you might get 1 then 3 very quickly, then not long after 2 then 4 very quickly.
That was certainly one of the useful options, anyway.
Another was something like 1 then 2, 3 alone then 4 alone, all relatively quickly.

Originally Posted by Carsick

I was going to say something along those lines, though a lot more concise and less boring .

Originally Posted by Carsick

As for the Yamaha timing, from what I've read they've looked into doing it something like having 2 cylinders very slightly offset and then offsetting those two ba-dum ignitions by a little more so you might get 1 then 3 very quickly, then not long after 2 then 4 very quickly.

Etc

I didn't know that! When I started in Industry, anything other than 1342 (or something like it) was thought liable to shake things to bits! I find it really fascinating....but then I'm really sad!

Wonder if Camilla was on to something.