Guy:

unless i am missing something, (likely) the flaw in your calculations is very basic

"If we assume 250 psi cylinder pressure at 90 degrees past TDC firing stroke "

your answer is based on an assumption? perhaps the flaw is not in the math, but in the assumption

It was an assumption, but a fairly good one.

see

http://www.kyma.no/sitefiles/site59/files/files/KDAreport.PDF 4 page pdf, some nice interesting data there.

then you need to do some of that math stuff to plot bearing load and torque at each degree of rotation, which will give you a bunch of other interesting answers.

few of which correlate with the dreaded "common sense"

also rated engine torque is something that is arrived at, at a constant rpm, without undue strain or temperature rise, undue smoking or other detrimental effect. rated torque is an average figure and not an instantaneous figure derived from a simple formulae based on on degree crank angle.

so your response is torque is not instantaneous, but the average figure over 720 crank degrees of the 4 stroke cycle.

good answer, it would require vastly higher instanataneous torque between TDC and TDC + 90 degrees, lower mechanical advantage of just past TDC compensated for by vastly higher cylinder pressures, as crank turns and mechanical advantage increases, cylinder pressure is dropping, so peak cylinder pressure is going to rise from 17:1 or 250 psi at injection to whatever the design peak is at around TDC firing stroke + 15/20 degrees, which will coincide with peak torque wear piston/barrel and big end / journal

getting back to the point here

oh, we never left the point.....

If you have peaks of maybe 1000 ft/lbs acting inside your engine you damn well need to know, because this directly affects where the centre of effort of these forces is going to be located.

you insist that lister got it right by spec'ing out a yard of concrete or was it a ton of concrete, you further insist that they arrived at this spec thru careful engineering

if remember correctly you state that lister made only one recommendation and that was the ton of concrete. have i fairly restated your position?

if i remember correctly you have stated that they made no other recommendation as to spec for a concrete base

could you tell me what the fundamental difference between a 5/1 and a 6/1 as it relates only to the concrete base?

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A 6/1 is just a 5/1 running faster.

Each individual power stroke isn't generating any different loads, they are just happening faster, higher frequency, shorter wavelength, same amplitude.

the concrete block is about amplitude, not frequency per se, it keeps coming back to that math.

i dont have all the spec's/dimensions on a 6/1 but i do a 5/1, so would you consider them to be virtually the same engine, for purposes of determineing the proper concrete block, size, weight and dimension?

they are the same engine, apart from the frequency issue mentioned above.

or can i calculate base on the 5/1 spec's to figure the concrete base to mount a 6/1 onto?

it is my understanding that both engines are basically the same, physically, i would assume there to be a slight difference in bore perhaps, or slight increase in rpm for a 6/1

but all else is virtually the same.

6/1 is a 5/1 running at 650 rpm instead of 600 rpm

i think i am getting closer to an understanding, but could use your continued input

bob g

you gotta do the math.

you did not tell me what was wrong with my "question" and then tell me the right answer.

you hinted at it, but you didn't answer directly and lay it on the line

go work out the answer and ideally the reasoning in some detail and lay it out here, it will solve much of the question you keep asking.

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everyone thinks 650 rpm = 650 rpm = 650 rpm

nope, it is a MEAN speed.

why else do your lights flicker?

you think your lights visibly flicker because the engine went from 650 rpm to 649 and back up to 650 again? a change of 0.15%???

get real, there are two full rotations in a 4 stroke, you only get (useful) power on one quarter of one rotation, the other one and three quarter rotations are drag, in varying amounts, the last compression stroke being the worst.

measure rotational speed degree by degree for each of those 720 degrees of rotation and you see some remarkable changes.

5% is nothing to talk about, 10% isn't even exceptional.

5% is 32 rpm, you think you can see it, you can't.

32 rpm acceleration in 90 degrees of crank travel.

with a 24 inch dia flywheel you have 75 inches of circumference, 32 extra rpm is 32 x 75 = 2400, 200 feet.

650 rpm is 10.83 revs per sec

1 rev is therefore 0.092 sec

90 degrees of crank rotation is a quarter of that, 0.092 / 4 = 0.023

200 extra feet of flywheel rim travel in 0.023 seconds, is 8695 feet per second

say you have 100 lbs of iron in each rim, 2 flywheels, 200 lbs of iron being accelerated an extra 200 feet in one fortieth of a second.

whats the tensile / shear / compression numbers of cast iron?

Why is the apparently incredibly conservative 60 mph rim speed always used?

what do you think actually causes the stress failures in flywheels that allow them to explode in overspeed conditions?

You weren't going to destructively test your flywheel on a smooth electric motor and then take those number as being good for a single cylinder engine were you?

why were early cast flywheels made with s shaped spokes?

what happens to torque output if you double flywheel mass, or halve it?

work the math