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Old 02-08-2018, 02:06 PM   #1
Standing Elk
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Default Counter balanced crank

Is there any way to determine if you have a counterbalanced crankshaft as opposed to stock without physically having a look at it? I have not driven any other A's except mine so do not have a feel for what the difference might be. Thanks
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Old 02-08-2018, 02:20 PM   #2
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Default Re: Counter balanced crank

No. You may be able to pull the oil filler out and see it though
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Old 02-08-2018, 02:35 PM   #3
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Default Re: Counter balanced crank

Borescope?
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Old 02-08-2018, 02:49 PM   #4
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Default Re: Counter balanced crank

If it doesn't have one are you going to put one in? Just curious. If you have been driving it awhile it might not hurt to drop the pan at the next oil change and check clearances while you take a look at the crank.

Last edited by J Franklin; 02-08-2018 at 02:52 PM. Reason: added thought
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Old 02-08-2018, 03:05 PM   #5
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Default Re: Counter balanced crank

There is a model B crankshaft (counterweighted) as well as cam in my Late '31 Truck. I am told that a non-counterweighted engine will idle slower. This is from a friend that I have known for a very long time. He has had National Winner A's. We will find out as there is a standard A crank in my Diamond engine Standard Roadster (work in process). Not sure if this will help you or not.
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Old 02-08-2018, 04:02 PM   #6
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Default Re: Counter balanced crank

A heavier crankshaft will slow throttle response . I've never had a problem with lighter crankshafts . If I used a B crank , it would be an early one without counterweights . Larger rod bearing journals and B rods would be enough for my use
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Old 02-08-2018, 08:29 PM   #7
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Default Re: Counter balanced crank

Looks like the answer so far is NO. Search for c/w cranks to see what they look like. pull the filler tube, engine not running. I'd leave it alone if it runs smooth at 45mph.
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Old 02-08-2018, 08:38 PM   #8
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Default Re: Counter balanced crank

I can't see how one could discern from the way a motor is running as to whether it has a counterweighted crank or not?
Usually one lightens the flywheel when installing a counterweighted flywheel to counteract the extra weight of the crankshaft.
As for affecting the idle? it all depends upon tuning, and even with twin Strombergs, I can get my motor to idle smoothly at 200rpm. Recently at a club event, one of the competitions was to see how long it would take to explode a rubber glove connected to the exhaust pipe. Ours took the longest (with 7:1 compression as well) indicating that it was idling slower than all the standard Model As.
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Old 02-08-2018, 09:58 PM   #9
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Default Re: Counter balanced crank

It looks like this. I if there is not a screen in your oil tube, try taking a flash photo with an Iphone down the tube.
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File Type: jpg IMG_4197.jpg (62.3 KB, 213 views)
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Old 02-09-2018, 12:42 AM   #10
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Default Re: Counter balanced crank

Counter weighted cranks have to be made in the correct way, to get the smoothest running balance.

The ones I see, with a chunk of iron hanging off one side, opposite a throw, is the wrong way to try and counter balance a crank, and get all of the advantages of a counter weight sucking up the power stroke impulse.

The right way to weight a crank, is to have some of the weight incircle the center line of the crank. To see what I mean, look at Jim's post No. 9.

With the pin, and the thickness of the weight between the pin and center line, should be about the same amount in weight that is sticking out the opposite side.

That is where you get smooth running balance.

1969 we started building counter weights, like Ford had on the Trucks. The only thing we changed, was we made the weights 5/8's wide, same as the crank disks, and didn't have the heavy chunk of iron that stuck in the way of the rod pin so you couldn't grind it with out removing the weights. In a truck, I can see where the extra weight would help, but would not be of any benefit in a car.

We have about 75 to a 100 out there. We haven't built any for about 10 years now, as we are to busy with Babbitting.

I found two cranks with the weights on.

The first one is a stock Model A crank, with weights.

The second one is an A counter weighted crank that I put in a Model T block for Mel Alexandra, (Spelled wrong ) of Ohama , Ne.



Herm
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File Type: jpg Our Model A Counter Weighted Crank 013.jpg (34.4 KB, 193 views)
File Type: jpg Model A Crank, in a Model T Block 004.jpg (38.0 KB, 194 views)
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Old 02-09-2018, 11:44 AM   #11
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Default Re: Counter balanced crank

You can pull out the oil fill tube then you can see the crankshaft well and you will see the counter weights if it has them. it takes less than a minute to look inside there.
I checked mine when I first bought it hoping to see a nice counterweighted crank but no, I only saw what Henry put in there in 1928!
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Old 02-09-2018, 12:38 PM   #12
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Default Re: Counter balanced crank

I'm not disagreeing with Herm !!! especially the part about the really heavy BB crank weights . I've read that most only remove the amount from the flywheel that was added in crankshaft weight. This will only result in a status quo and no weight will actually be removed from the rotating mass . For any improvement in throttle response, more weight will need to be removed . Removing weight from the flywheel not only improves throttle response, it takes excess weight off the main bearings for longer engine life .
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Old 02-09-2018, 12:55 PM   #13
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Default Re: Counter balanced crank

If you are driving over 55 mph with stock trans and rear end and the engine is not about to shake apart, you probably have a balanced crankshaft.
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Old 02-09-2018, 03:13 PM   #14
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Default Re: Counter balanced crank

Quote:
Originally Posted by Purdy Swoft View Post
I'm not disagreeing with Herm !!! especially the part about the really heavy BB crank weights . I've read that most only remove the amount from the flywheel that was added in crankshaft weight. This will only result in a status quo and no weight will actually be removed from the rotating mass . For any improvement in throttle response, more weight will need to be removed . Removing weight from the flywheel not only improves throttle response, it takes excess weight off the main bearings for longer engine life .
And I'm not disagreeing with Purdy but there is more to it than that, as usual.
When weight is added to the crank shaft, it is closer to the centre-line of the shaft than the metal one would remove from the fly wheel. It therefore has less momentum as it spins than the removed metal had (and less inertia.)
In other words, if say, 8 lbs of metal were added to the crank shaft by the counterweights and 8 lbs was removed from the perimeter on the flywheel, the motor will be more responsive than before because the 8 lbs that were added are closer to the centre line (and have less leverage, if you like.)
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Old 02-09-2018, 03:44 PM   #15
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Default Re: Counter balanced crank

I tend to support Purdy's position on the positioning of counterweights. His version is closest to that of the Model B engines that were remanufactured by Ford during the 1930's and Ford had done a bit of research on the subject.
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Old 02-09-2018, 03:47 PM   #16
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Default Re: Counter balanced crank

I Agree, Mr. Purdy.

I see the flywheel, and crankshafts as two distinct parts, that should be machined, and balanced individually, or the pressure plate bolted to the flywheel, and balanced, or the pressure plate balanced by its self, which is not as good.

Good, crankshaft balancing, always saves the mains, better gas mileage, more power, less wear on engine parts, ect.

Good, Flywheel balance, along with weight removal, will save the center main a lot of wear.

Rods and pistons are a must to balance, also.

Herm.
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Old 02-09-2018, 03:54 PM   #17
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Default Re: Counter balanced crank

Quote:
Originally Posted by Synchro909 View Post
And I'm not disagreeing with Purdy but there is more to it than that, as usual.
When weight is added to the crank shaft, it is closer to the centre-line of the shaft than the metal one would remove from the fly wheel. It therefore has less momentum as it spins than the removed metal had (and less inertia.)
In other words, if say, 8 lbs of metal were added to the crank shaft by the counterweights and 8 lbs was removed from the perimeter on the flywheel, the motor will be more responsive than before because the 8 lbs that were added are closer to the centre line (and have less leverage, if you like.)
I have never found that to be true in any of my experience.

Herm.
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Old 02-09-2018, 05:40 PM   #18
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Default Re: Counter balanced crank

My thought was about using the 1932 model B uncounter balanced crank shaft . The main bearings would have to be machined down to model A size . The rod journals on the 1932 model B crankshaft are larger and stronger than the model A crankshaft . It is way lighter than the heavy replacement BB truck crankshaft . The 32 model B crankshaft is lighter than the often called C forged counterweighted cranks used in 1933 and later model B type engines. The model B original flywheels were lighter .The last one was 18 pounds lighter .This was just a thought for a stronger engine that could have a lighter stronger than model A, lighter than counter balanced and quicker reving than stoick model A or B . I'm not an engineer or machinist . I would have to farm out the crankshaft grinding.I've used stock model A crankshafts since 1960 and have never had a failure . I think I've got five or six beaver tail crankshafts . that is just another lighter stronger crank possibilities that I may never get around to tring . No disagreement .
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Old 02-10-2018, 04:26 AM   #19
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Default Re: Counter balanced crank

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Originally Posted by Kohnke Rebabbitting View Post
I have never found that to be true in any of my experience.

Herm.
It's a simple matter of physics but the difference is not huge.
Herm,
Please read that understanding it is said with respect, not wanting to start an argument.
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Last edited by Synchro909; 02-10-2018 at 04:31 AM.
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Old 02-10-2018, 04:05 PM   #20
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Default Re: Counter balanced crank

I don't know about Physics, but 54 years of every day experience with thousands of crankshafts, balanced, or other wise, and way more bearings, rebabbitted, and with all cranks tested for straightness, and reground.

I can tell you that chunks of iron hung off one side on a T, A, or B, Ford crankshaft, is junk for balance, compared to the Ford designed weights!

Here is a good test that will explain a lot to anybody.

Take a small lathe that has the room to swing a balanced crank, and put it between centers. Then take a crank that has the weights hanging off one side. After it is between centers, put the lathe in the back gear, and run the lathe at the slowest speed it will run. Now between the gears when it is revolving, this is what your going to hear. Clunk Clunk, Clunk Clunk, as it goes around.

Why, because the crank has way more weight on the chunk of weight side, then on the pin side. So as you revolve the crank, the crank runs into its self, and then backs off again, when the force is neutral. A Ford crank weighted crank, will not do that.

So with a chunk of weight crank, and the harmonics it creates, it can hold back speed, gas mileage, Power, ect.

Ever wonder why there is such a difference in the way one motor runs, compared, to another, when they are both rebuilt, only just different builders. There is even way more then this!

Do the same with a Ford crank, or as we did with our copied Ford weighted crank, all you will hear is Quiet.

One of the shops that we weighted cranks for, told me last week one of the crank owners stop in to bring a different brand of car motor for rebuild, and he asked the motor owner about his "A" engine, and he said when it is idling, you can put your hand on the head, and if it weren't for the heat, you couldn't tell it was running.

Thanks

Herm.

Last edited by Kohnke Rebabbitting; 02-10-2018 at 04:37 PM.
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