Crankshaft Opinion
04-18-2019, 11:01 PM
#16
Rainman
Rennlist Member
Rennlist Member
It's interesting that if I remember correctly, the Cosworth/Merc crank took off the center sets of counterweights and left the end cylinder weights intact.
I asked Michael Mount about this once because his business card reads 'Porsche/Cosworth' but I think it was more because it was lost in multiple points of conversation and he just forgot to reply to this point rather than a lack of experience or formed opinion on it.
Seems that it would be a torsional force nightmare.
If you are into the 16V, and I know you are, find all you can read on that Cosworth/Merc 190e engine, it's pretty interesting since they were from the same era, that even with the force of Cosworth helping Mercedes along with development, the 944S 2.5 16V by comparison is still pretty impressive.
I actually bid on (just missed) a Cosworth?Merc 190e header to measure it and see if it could be adapted to the 944S engine.
It has square/flat exhaust port interface.
T
I asked Michael Mount about this once because his business card reads 'Porsche/Cosworth' but I think it was more because it was lost in multiple points of conversation and he just forgot to reply to this point rather than a lack of experience or formed opinion on it.
Seems that it would be a torsional force nightmare.
If you are into the 16V, and I know you are, find all you can read on that Cosworth/Merc 190e engine, it's pretty interesting since they were from the same era, that even with the force of Cosworth helping Mercedes along with development, the 944S 2.5 16V by comparison is still pretty impressive.
I actually bid on (just missed) a Cosworth?Merc 190e header to measure it and see if it could be adapted to the 944S engine.
It has square/flat exhaust port interface.
T
you know, if you're looking for headers...
Last edited by V2Rocket; 04-21-2019 at 10:31 AM.
04-19-2019, 07:58 PM
#17
Rennlist Member
Oil in liquid form, you can rule out the front half of the crank "splashing" because that part of the pan is basically oil return.
I would guess there's 2 quarts or less in the sump with our engines running at anything past 3000 rpms, the crank weights would scarcely touch this oil.
Oil in a mist/cloud form is another story.
How much cooling effect this would have is open for interpretation but I would guess, in an infrared spectrum, the crank main and rod journals would show to be way hotter that the counterweights. That's where this oil would have just come from, so, it's cooling effect....?
I would guess there's 2 quarts or less in the sump with our engines running at anything past 3000 rpms, the crank weights would scarcely touch this oil.
Oil in a mist/cloud form is another story.
How much cooling effect this would have is open for interpretation but I would guess, in an infrared spectrum, the crank main and rod journals would show to be way hotter that the counterweights. That's where this oil would have just come from, so, it's cooling effect....?
Inertia could be substituted by "momentum", it's the engine's resistance to slow down vs the work load.
It stores energy.
The weighted parts do not want to slow.
You lighten everything reciprocating and you reduce this resistance.
An example, you ever cut grass with a self propelled push mower and it's cutting along at a set speed.?
You come to a high patch and the engine slows, slows more and almost kills.
The combination of the engine's power output + momentum of the weighted parts could not overcome the load.
Now, take hat same mover and bolt a 10lb flywheel to it and chances are, it'll cruise right on through.
In the adverse, take 1/2 the weight off the crank and it won't get as far as the stock engine.
I read a paper once that stated that without the inertial power storage of a flywheel, a single cylinder engine (because it has no other firing opposing cylinder) could not run past the combustion stroke. It would not be able to even run long enough to make it to exhaust stroke.
Reducing the crank to a smaller diameter, center of rotation would have the same effect.
T
It stores energy.
The weighted parts do not want to slow.
You lighten everything reciprocating and you reduce this resistance.
An example, you ever cut grass with a self propelled push mower and it's cutting along at a set speed.?
You come to a high patch and the engine slows, slows more and almost kills.
The combination of the engine's power output + momentum of the weighted parts could not overcome the load.
Now, take hat same mover and bolt a 10lb flywheel to it and chances are, it'll cruise right on through.
In the adverse, take 1/2 the weight off the crank and it won't get as far as the stock engine.
I read a paper once that stated that without the inertial power storage of a flywheel, a single cylinder engine (because it has no other firing opposing cylinder) could not run past the combustion stroke. It would not be able to even run long enough to make it to exhaust stroke.
Reducing the crank to a smaller diameter, center of rotation would have the same effect.
T
04-19-2019, 09:00 PM
#18
Drifting
I was thinking more of splashing on the cylinder walls.
I understand momentum which is the whole reason for lightening an engine, less rotating mass means it gets up to speed quicker, less hp used in the engine to get up to speed quicker (open to debate as to significant hp being saved from lighter rotating parts). I am having trouble with the engine being detrimentally effected while driving through a corner.
I understand momentum which is the whole reason for lightening an engine, less rotating mass means it gets up to speed quicker, less hp used in the engine to get up to speed quicker (open to debate as to significant hp being saved from lighter rotating parts). I am having trouble with the engine being detrimentally effected while driving through a corner.
04-19-2019, 11:08 PM
#19
Race Car
You get behind it and push it straight...., you'll get it going by yourself, maybe even to the speed of jogging.
Now, from a stop, get your helper to turn the wheel to right hand lock.
Try to push it again.
T
04-20-2019, 08:52 PM
#20
Rennlist Member
Again the engine is being driven through the corner. Its rpm is being directly effected by the wheel speed, in my car's circumstance never much below 3,000 rpm. Under braking if it drops below 3,000 I will down shift in all but the rarest of cases. And if I am not braking then I am under throttle, even if it is just maintenance throttle. In the cars I have tracked rarely has the rpm been much below 3,000 rpm even in my naturally aspirated cars. The only time I have seen rotating mass be beneficial is either getting the car rolling or while driving in the pits where the rpm's are significantly lower than track rpm's in first gear where they are magnified.