Christopher Albers wrote:
> Jarrid,
> can you help this guy out? You know far more about this stuff than I.
>
> Christopher
>
> Dear Chris:
>
> My names Dan.I've currently inroled in an automotive technology
> program.I have been assigned to write a report on Crankshafts.I have a
> general understanding of the function of the crankshaft.I know that it
> transfers the power from the pistons to the flywheel and ultimatly to
> the drive train.My questions to are about crankshaft throw to stroke.
> My questions are.
>
> 1.I know that crankshaft throws in 4 cyl.engine are 180 degrees apart
> and the banks are separated by 90 degrees. In a V-6 the throws are 120
> apart and the banks are separated 60 degrees.In a V-8 the throws 90
> degrees apart and banks are separted 90 degrees.
>
> 1A. First of all tell me if I'm right?
>
> 1B.Does the throw change from the V to in-line design?
>
> 2.My second question is can two connecting rods be connected to the
> same journal,if so will this change the throw in all cylinder designs
> from inline engines,To V type designs.
>
> 3.My third and question is how does throw affect the lenght of the
> piston stroke?
>
> 4.Can pistons fire simultainously?
>
> Chris if you could answer this questions for me I would greatly
> appreciate it.Or if you can't can you possibly direct me to someone
> that can.If you can't already tell I'm a novice to the field, so any
> feedback you could give me would be helpful.My E-Mail address is
> hdemarty(at)snet.net
> Thanks.
>
> From: "Hazel C . De-marty" <hdemarty(at)snet.net>
> Subject: Crankshaft Throw,and Stroke
> Date: Wed, 17 Feb 1999 22:58:28 +0000
Answer to 1A, mostly right, 4 cyl crank throws normally are seperated by 180
degrees, alltough V4s look kind of odd.
There is no hard fast rule to any V type engine being seperated by any given
angle, there are a great deal of 60 as well as
90 degree V6 engines, as well as 72 degree, and other anomilies. The crank
throws are generally seperated by 120
degrees, but the angle of the V plays into the apperance, that makes a 90
degree V6 crank look all out of balance.
Also, some exotic V engines, most notible some hot V8 engines have flat
cranks that ressemble inline 4 engines.
These engines are like twin 4 cyls in phase, and sound as such.
Answer to 1B, The throws are the same, but keep in mind no two engines of
the same displacement need have
the same bore or stroke as another. Regardless of inline or V type, the
displacement equation is...
disp = #cyls * (.5 * bore)^2 * 3.1416 * stroke
Answer to 2, yes, in fact most V engines have pairs of con rods sharing a
common journal, as as such have fewer
main bearings per rod then a typical 4 cyl, like most v8s have 5 mains like
a 5 main 4 banger. This does not effect the
throw, because regardless of how the rods are aranged, the radius of the rod
journal relative to the rotationall center
of the crank is still the same.
Answer to 3, the piston movement and the crank throw will be identical.
Answer to 4, pistons can be fired simultaneously, as in the odd flat carnk
V8 mentioned. This will result in odd firing
pattens on aly engine less than a 90 deg V8, and would also require a
special cam that would open and close
the valves simultaneously on complimentary cyls. IE (1 and 4, 2 and 3 on a
typical 4 cyl engine).
Hope this all helps.
Jarrid Gross
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