321apex wrote:Tommy Cookers wrote:
this is nothing to do with the mythical 'big bang' motorcycles
for 20 years (pre Doohan era) all 4 cylinder GP 2 strokes were more or less BB but no-one noticed ....
until, going to 67? deg V, Honda had the option of BB or the (Doohan's choice) small bang aka screamer and suddenly people noticed BB
if you are interested in BB do a search (this site) and you can read posts, mostly mine, (or message me)
Greetings again.
Can you provide brief comment what was the benefit of "big bang" engines you mentioned? I had always heard it had primarily to do with rear wheel bike power down traction. Is this true?
Now forwarding to 2014 F1, what may be the benefit of "big bang" here?
Thanks.
no benefit
since square 4 2 stroke and related narrow angle so-called V4s of the 60s they had paired firing or nearly paired for convenience
ie 2 biggish bangs per rev(sq 4), (or quite close to that eg with 15 deg V4 Yamahas) not 4 small bangs
(EDIT but anyone can re-mesh the crank coupling gears eg of their RG500 and get 4 small bangs ie firing every 90 deg or so)
when Honda chose the bigger V angle the quite close to 2 biggish bangs became 3 bangs quite close then 1 rather seperate
this was the origin of the BB term (recordings were said to show 3 firings within about 110 deg of crank rotation)
maybe Honda redesigned the crankshafts (towards cross-plane) to do this (not possible with 180 deg cranks ?)
and this redesign could with different meshing also give roughly 4 small bangs 'the screamer' ?
the late Prof Gordon Blair said that there would be power band differences with different firing intervals (his line of work)
Honda riders had a choice
a 12000 rpm torque ripple won't reach Earth via a loaded tyre because this won't pass any ripple above about 5 Hz
and if you wanted a torque ripple in pursuit of improved traction you could engineer the transmission to do this anyway
the reason sprockets don't have less than about 12 teeth is to avoid creating torque ripple aka vibration
so BB for traction is a myth
(Gordon Jackson etc won trials by using a only a few hundred rpm , that single cylinder torque ripple did get through to the ground)
the firing intervals are uneven in F1 only because a 90 deg V6 with 3 crank throws is dictated by the rules
the turbine would prefer equispacing, this was used by having 120 deg V eg in the Cosworth F1 turbo and older F1 Ferraris
each pin counterweighted by 1 reciprocating mass eliminates all vibration at engine rpm ('primary frequency') in a 90 deg V
ie all throws at 0 deg would allow 3 cylinders to all fire at 0 deg, then the other 3 all at 90 deg, then the first 3 (at 720 deg) etc
a really BB crankshaft, and it's legal, but pointless or worse