So to answer these questions when they arise, what mathematical formula do I use to find out what angle the crankshaft journals have to be at?
720/No. of cylinders or 360/No. of cylinders?
I suggest you go back, & hit the link in the 7th post on page 5 of this thread,echedey wrote: ↑Sun Jan 23, 2022 11:09 pmhere is a formula for calculating the firing sequence of v12 aircraft engines.
-In other words: the 720° needed, divided by the number of cylinders, equals the ignition angle (720 : 9 = 80°, twice 40° which is the geometric angle).
-Another story will be the case of a double star (C). First it must be noted that the crankshaft has a neck for each star and at 180°. In the figure, two crankshafts, the first for a single star and the other for a double star.
-The ignition for each star is the same as for a single star, but with 180º between them, giving us a very different ignition order. The numbering of the cylinders is done correlatively but jumping from one star to another. I have always used the same formula. Basically it is N : 2 + 2. Starting with 180 + 720 : N, clearing it out leads to the above formula:
https://i.postimg.cc/MGChBqvS/fo3.png
-In which N is the number of cylinders, being a double star engine with 18 cylinders, the number of cylinders between ignitions is 11 (N:2=9+2), so the next cylinder to ignite will be 12, then 12+11, 23, or the same as 5. Then 5+11 will be 16. 16+11, etc.
let me say that I still don't understand the formula because I'm trying to figure out how to balance my accounts and resorber the ignition sequence with the formula if someone understood it please explain it to me by doing the formula thank you.
Is this a typo?Tommy Cookers wrote: ↑Sun Jan 23, 2022 10:14 pm. . . . ie the crankshaft takes 4 revs for every rod to experience a power stroke . . . . .
C'mon now T-C, you know very well that the Lion also had 66% more energy inputs than an 8 litre 4,Tommy Cookers wrote: ↑Sun Jan 23, 2022 11:35 amJ.A.W. wrote: ↑Sun Jan 23, 2022 12:41 amHowever, the cylinder bank angle ... will alter the dynamics considerably, you need only check how a 360 degree 'flat plane' crank behaves in a zero degree twin, vs V-twin,
or various iterations of V-4/8, with either 180 or 360 cranks, in various V-angle cylinders..
Are you seriously suggesting an ~8 litre inline 4* wouldn't have vibration issues far worse than the Lion?
Napier Lion was hardly "toast" by the mid-20s, given it remained in production/service for another
20 years, & was powering world-speed & distance record machines over that period...
again ....
yes I seriously suggested the 8 litre inline 4 would have about half the vibrational energy than the whole Lion had
(of course the Lions energy is spread over notionally 3x the mass - so the amplitude of whole Lion vibration is less)
and yes - I have flown behind such (an ENMA Tigre c.8 litre inline 4 ) and it's rather smooth
anyway the tens of thousands of 'flat crank' V8s were successful at this time ie the Hispano-Suiza/Wright
T-C, a 2-stroke inline 3cyl with 120 degree crank throws fires at every 120 degrees of crankTommy Cookers wrote: ↑Sun Jan 23, 2022 10:14 pmin a 4 stroke V12 engine each rod experiences .....
a power stroke on one bank within 2 revs - then a power stroke on the other bank within another 2 revs
ie the crankshaft takes 4 revs for every rod to experience a power stroke
each crankshaft plane has 2 crank throws - and each throw has 2 rods
so a 3 plane crank could have 6 crank throw positions
but only 3 positions are needed - 2 throws in each of the 3 positions
all drawings and photos shows this
there were 7 bank engines with 4, 6, or even 8 rows of cylinders
crankshaft counterweights can't reduce vibration - except in singles or twins that behave like singles
Nope, it's parallel - sequential actually. V10 and beyond have 4 turbo's for the Wartsila 31. But they have 5 bar turbo pressure, so that's more the reason for sequential.PlatinumZealot wrote: ↑Mon Jan 17, 2022 9:40 pmWartsilla?Bandit1216 wrote: ↑Thu Jan 13, 2022 4:28 pmI've checked some data of the engines the company I work for makes. We have relative new one with V engines in a brought range, all have Quad sequential turbo's except for the V8 which has 2 (sequential)
Although they are a little bigger and run on diesel or HFO it might give some data? The specific fuel consumption does not differ between V8, V10, V12, V14 or V16 of the same engine type. That would imply there no difference in losses between the configs.
I think those engine is parallel turbo. The other turbine might be an electric generator, or if you see a second compressor it is an electric blower... depending on engine size.. but I doubt sequential because these engines run within a very small rpm band most of the time. If I recall correctly...
Nope, it's parallel - sequential actually. V10 and beyond have 4 turbo's for the Wartsila 31. But they have 5 bar turbo pressure, so that's more the reason for sequential.Bandit1216 wrote: ↑Mon Jan 24, 2022 4:26 pm
Wartsilla?
I think those engine is parallel turbo. The other turbine might be an electric generator, or if you see a second compressor it is an electric blower... depending on engine size.. but I doubt sequential because these engines run within a very small rpm band most of the time. If I recall correctly...
Counterweights act as inertial dampers & as a location for add-on pendulum balancers:Tommy Cookers wrote: ↑Mon Jan 24, 2022 3:36 pmcrankshaft counterweights can't reduce vibration - except in singles or twins that behave like singles
otherwise such counterweights reduce loads locally (eg to benefit main bearings) - but not in sum ie globally
in no engine can counterweights reduce 2nd order vibration - because they move at engine rpm not 2x engine rpm
(2nd order vibration being due to changes in rod angularity twice per crankshaft rotation)
in singles/twins behaving like singles counterweights reduce 1st order engine rpm vibration to twice the 2nd order vibe
about a million races have been won with these
the normal engine (inline 4) produces (only) 2nd order vibration - regardless of counterweights
because the sum of any counterweight forces at engine speed is zero (eg 2 going up - 2 going down)
about a million races have been won with these
whether or not the Lion needed counterweights was a matter for the main bearings and crankshaft
nothing to do with vibration
counterweights might even increase bending due to gas loads
my English teacher had a Railton - with a straight 8 engine
saviour stivala wrote: ↑Tue Jan 25, 2022 7:19 amInteresting titbits about the history of 12-cylinder engines.
One-of-four.
All vee-type engines, not only V-12’s. Trace their origins to the 1889 Daimler vee-twin designed by Wilbelm Mybach. Mybach arranged for the two connecting rods of the engine, with its 17 degree Vee to share a common crankpin. With what became known as the fork-and-blade big end bearing system.
The first Vee-type 12-cylinder engine was produced in 1904 by the ‘Putney Motor Works’ in London. Commissioned for a racing boat, the Graig Dorwald V-12 was impressively light at 950 lb for its 18.3-litr. Its VEE angle was 90 degree.
When you are out with your puppy always have a titbit in your pocket.
Hey T-C, no need to squirm, grunt-guru has safely quoted your faux-pas,