Counterweighted Crank

[hardtimes]

Originally Posted by Pete

I am wondering if any of you that are giving balancing advice have actually run a balancer?

Hey Pete,
Are those crickets I hear..
My favorite fishing bait !

Schalms does nice A/B engine work. Why not ask him, if your going to have him do work for you ?

[40 Deluxe]

Originally Posted by Pete

I am wondering if any of you that are giving balancing advice have actually run a balancer?

Uhhh…..no but I saw some pictures in a book once!

[Joe K]

Originally Posted by johnneilson

I am sure that Herm is correct on the Babbitt details.
There is another problem with the article, the dynamic balance of a 4 cyl inline motor can never be achieved due to the differences in acceleration of the pistons.
You can get close and at low speeds it will be perceived as so, but still not correct.


John

I think I intimated that when I said dynamic balance could be "optimized."

The crank/rotating assembly can be spot on. Attach a whole bunch of other things to it - not so much.

Joe K

[Railcarmover]

Well I'm not a machinist,I know that.But you don't need to run a balancer or be a machinist to understand basic principles,as a mechanic they are valuable in understanding what you are doing.Its my opinion that in a street driven model a counterbalanced crankshafts are oversold.As others have pointed out there are inherent balance issues with a four cylinder engine that cant be cured.
I do know a flywheel stores kinetic energy,and although an engine might ramp up and down faster with a light wheel there are tradeoffs in engine longevity and smoothness of power transfer.Racing?the lighter the better,engine durability isn't considered.Street driving? Ford designed the A to get into high gear as fast as possible and leave it there,flywheel mass supports this effect.

Back to the topic,the benefits of a counterbalanced crankshaft are real,and can be supported by theory.However I contend the benefits don't necessarily outweigh the cost.

[Joe K]

Back to the topic,the benefits of a counterbalanced crankshaft are real,and can be supported by theory.However I contend the benefits don't necessarily outweigh the cost.

The counterbalance of what you want to improve vs the depth of your wallet?

Agreed - and when you're done you have at best a car still "challenged" by todays automotive competition.

Graduating from college in 1977, I was offered by Dad to have him "buy me a car" - which in dadspeak means a "reasonable safe reliable car." I had his hand-me-down 1970 Chevrolet Bel-Aire - the one with the door pillar rot - and he and I could both see the issues of that (then) 7 year old car. He had my best interests in mind.

"Dad I want to buy a Model A"

"Don't" he says - "I think you need a 'better' car."

Having owned one "back in the day" Dad knew full well the issues attendant to the Model A: relatively underpowered, with original mechanical brakes a tad difficult to stop, periodic engine tear-down and shim removal, and - not the least of which - a car which was (then) 40 years old. Improvement had happened in things automotive since 1930 - not the least of which occupant safety. And old things deteriorate in hidden ways unless you know what you're doing and can anticipate them - which is frequently more expensive than simply buying new.

All of these shortcomings can be overcome - but at what price?

I have reported the 29CC pickup of my avatar was a 'graduation present' from my parents - but that is only approximately true. A "real car" of the gift allowed me to hold a "real job" at distance (most are in our modern world) and make "real discretionary dollars" with which to buy a "real discretionary car."

"Oh the choices you will make" I tell my own children.


Joe K

[Jim Brierley]

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Just to dispel a myth, The crank doesn't know what kind or weight of flywheel is bolted to it, they are totally independent of each other. A lighter wheel will accelerate and decelerate more quickly than a heavy one, but does not increase horsepower, it just feels like it does.

[johnneilson]

So, just to clarify about the flywheel and crank weight.
There has been mention of removing the difference in weight from the flywheel to keep the total rotating weight the same. This is not completely true. The Moment of Inertia is the major factor in the rotating weight game. In simple terms, at the diameter of the crankshaft, approx 7", adding 1# weight would equate to about 5# removal of weight to the flywheel at approx 11" dia.
John

[updraught]

I think the moment of inertia is mass x radius squared. Therefore gets bigger quick at the 11 inch rather less at the 7 inch.

[Railcarmover]

The storage of kinetic energy,or inertia from the flywheel has many effects on the driveabilty of a car,from smoother clutch engagement to reduced driveline vibration.It was a subject of debate during A engine development,Ford felt the mass of the flywheel minimized the main bearing issue (it was identified during development) while others, including Farkas and Hicks wanted a larger crankshaft journal.Ford won the battle in '27,but the engine engineers won the war in '32,when larger journals,pressurization and mechanical advance distributors were introduced with the B..

[Joe K]

One source I've seen says you machine off 24 lbs of the 67 lb flywheel. That same source replaces the Model A with the later V8 pressure plate and throwout assembly (any weight difference with the Model A components not mentioned, one assumes the total weight is less?)


Joe K