Harmonic dampener pulley

AL in NY

AL in NY

Well-known member
I posted a thread a couple of weeks ago about engine vibration (harmonics) at 2100 RPM's and got a lot of great replies. I have been thinking about my problem and some of the solutions posted. Also got to thinking, would the engine harmonics be lessened or eliminated by the addition of a front crankshaft dampener? I think it's do-able by using the seal end of the two piece Model A pulley and machining a modern dampener to fit it. Also machine a 5/8" X 5.25" V-belt pulley to add to the front of the dampener. Has anyone tried putting a front dampener on a Model A counterbalanced engine to lessen the harmonic vibration? And if so, did it do the job intended?
 
Here's a pic of big block Chev. damper on a B.
In a stock chassis you will have to trim the front cross member slightly.
Fluid dampers work very well.
Stay away from the shot filled ones.
 

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HEre is a post I saved from a few years ago describing my experience with the reproduction Winfield damper sold by a shop in CA (Rosemead, I believe). Another fellow had a different model on display at the 1998 Joint Meet in Tacoma. Also, an engine rebuilder in Texas was selling for installation on the flywheel, which is just one of the many things I have never understood.

At the time, Gene Scott was running the shop. He promised very little if any in perceived vibration reduction, and that is what I got. I had one on my car for 10 years and just removed it when the motor was redone. Couldn't tell any difference, but always hoped that the crankshaft appreciated it. Other than not being able to tell any difference, I left it off because I wanted to try Cling's serpentine belt system and wanted to spare my crank the work of spinning that extra 8 pounds or so. Also, it makes for such a tight fit that it's tough to change the belt.

I have read very contradictory things about using a damper, including disagreement about what the thing should be called! Some experts (aren't we all?) say that great damage could be done by using one not expressly designed for the motor, and, then, what happens when we add counterweights and a high-comp head, I wonder. I have read that the fluid type are safe, but none are available for the A that I know of. There is great disagreement about whether the style installed in the flywheel makes sense. I hoped that Winfield's genius carried over to this topic too, when I bought mine.

My thinking about why they don't create much perceived difference is that the damper works against the torsional twisting of the crank that happens with every power stroke. This tends to break the crank if not cushioned. However, it's not often a problem with Model A's, I suspect because of their low power and rpms. I think that the major vibrations perceived by the driver are not torsional in nature. They are from the fact that the straight-4 engine is fundamentally unbalanced: the pistons at the top of their strokes undergo a much more abrupt change in direction and momentum than they do at the bottom of the strokes, where the crank throws swing the rod ends around in a circle. I believe that the net effect of this is to make the engine bounce up and down and to whip the crank into an arc that wears on the main bearings, especially the center main. That's what makes the motor bounce on the mounts and is what we feel.

I agree with Tim that all Model A's have preferred vibration points. Interestingly, the worst vibrations and bearing loads occur when backing down from high speeds, rather than when loading the engine; the exhaust stroke with the piston coming up against an empty combustion chamber really hammers the bearing. Or so I understand.

Steve
 
A good way to tell if a damper is working is, after going for a drive where you vary the engine speed often, feel it to see if it is warm.
Be careful because if your engine has a lot of torsional vibration, the damper can get hot enough to burn you.
This is the reason to stay away from shot filled dampers. On some engines they get so hot the shot actually welds itself into a ball and when this happens it will start vibrating so bad it will explode.
 
I think that Jim Gordon at Specialty Ford parts in Rosemead CA now produces the Winfield vibration dampener that some others may sell. Try calling 626-280-4546 the address is Specioalty Ford parts 9103E Garvey Ave. Rosemead CA. 91770 Jim also produces the aluminum Winfield heads and sells lots of interesting parts.
 
Al, your engine is counterbalanced and has a vibration? Sounds to me like you should find the problem not seek somthing to mask it. I didn't read your prior thread but I would check the internals and the flywheel area for the problem.....

Good luck
 
I agree with ctlikon0712, check the crank. Just adding flyweights does not make a counterbalanced crank, it can make a disaster. The crank has to be checked for straight and balanced AFTER the weights are added. I had an engine come in for rebuild that the crank was counter-weighted but had not been straightened and was out several thou. Consequently the balance was wrong and caused a severe vibration. The crank had also been cut for a modern seal but leaked probably because the cut was either done on a worn lathe that had run-out or cut too much. The person that modifies the crank has to know what they are doing as does the grinder tech so the weights do the job correctly. The counterweights don't eliminate all the vibration in a Model A but they help greatly. It is also advised greatly, to add a lightened and balanced flywheel since, it can have a negative effect on vibrations.
 
I installed a SBC dampener on my modified model A engine after breaking 2 crankshafts, both at #4 throw, I was told by engine builder that many were using the dampeners so I bought the dampener they were adapting to the A B crankshaft. Again, I'm speaking of a modified model A engine. The current crankshaft seems to be broken. haven't pulled the engine out of the car to see just where. I also have one on the engine in my RPU and have found it is slipping on the hub. I will clarify, on the dampener hub and not the crank. I changed my distributor and have found my timing mark for TDC is off by quite a bit. So if I replace them it will be with liquid filled units. Another point for those who might be interested, the breakage seems to occur at 4,000 RPM's. The first 2 cranks were A's with welded counter weights the 3rd was a B ground off set 5/32" to A sizes. I'm now saving for a Scat crank.
 
ctlikon0712, you should have taken the time to read my prior thread before commenting here. I'm not trying to band aid this problem. I am looking for way to minimize harmonic vibration that occurs in my engine at 2100 RPM's. I will disassemble and double check the crankshaft and flywheel/pressure plate balance. I'll also check piston and rod weights. As stated in the prior thread, doing all this probably won't eliminate the harmonic vibration that is inherit in L4 engines, I'm just hoping to minimize it some by possibly adding a front harmonic dampener. Please take the time to read posts before making critical comments.
 
Purdy Swoft, thanks for the contact information. I'll give them a call.
James Rogers, I'll be sure to have my counter-balanced crank check for straightness........thanks
1931 Flamingo, didn't see the dampener in the Sac Vintage Ford online catalog.
 
AL in NY said:
I posted a thread a couple of weeks ago about engine vibration (harmonics) at 2100 RPM's and got a lot of great replies. I have been thinking about my problem and some of the solutions posted. Also got to thinking, would the engine harmonics be lessened or eliminated by the addition of a front crankshaft dampener? I think it's do-able by using the seal end of the two piece Model A pulley and machining a modern dampener to fit it. Also machine a 5/8" X 5.25" V-belt pulley to add to the front of the dampener. Has anyone tried putting a front dampener on a Model A counterbalanced engine to lessen the harmonic vibration? And if so, did it do the job intended?
Click to expand...

This has been posted before but might be good for a review here.

The degree of balance in any rotating part is directly proportional to the rigidity of the mounting.
A 4 cylinder engine with a single plane crank cannot be be so called "completely balanced".
It has the same problem as a single cylinder engine.
You can only balance it for a narrow rpm range.
This is why you still feel a model A engine shake at certain rpm ranges even after being balanced.
You can change the rpm it shakes at but you can't eliminate the shake.
Certain types of industrial and racing 4 cylinder engines have achieved something close to ideal balance by using "balance" shafts. This is a counterweighted shaft that is mounted on the oposite side of the engine from the camshaft with the weights synchronized to counteract the vibration of the crank.
In a model A/B engine, the ideal situation would be to have the harmomic damper the same weight as the clutch/flywheel assembly to reduce harmonic vibration. This however will not eliminate the felt vibration.
It will prolong the life of the engine though. In the real world this is difficult to achieve but can be approched by using a damper from a big block Chev. and a 12 lb. aluminum flywheel with an aluminum clutch cover. The idea is to get the weights at each end of the crank as close as possible to the same weight.
Reducing flywheel weight has an added advantage in making shifting easier and faster.
All of this modification will all but eliminate TORSIONAL vibration but will not eliminate total engine vibration. You do not normally feel torsional vibration in the seat of your pants.
Crankshaft counterweights help reduce overall vibration by adding rotating mass and hence damping of felt vibration. There is not enough room in the "A" crankcase to add enough counterweight to acheive a comfortable "seat of the pants" vibration level. 60% is about all the weight that can be squeezed in without redesigning the whole engine.
As far as felt vibration on deceleration that appears to be more than on acceleration, there are several explanations but mainly it is due to the cushioning affect of the charge in the cylinder on acceleration as opposed to the lack of on deceleration. This effect almost disappears when the weights on each end of the crank approach the same.This would indicate that torsional vibration does play a small part in the problem.
A couple of definitions are offered here for a better understanding about balancing.
Static balancing is balancing in a single plane.
Dynamic balancing means the object is balanced over it's whole length.
Both are done while the part is rotating in the balancer.
Bob weights are not used to balance single plane cranks except for extreme rpm racing engines.
 
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AL in NY, in no way was my comment critical; I was offering my honest opinion/advice on the matter. If I was being critical I wouldn’t have said at the end "good luck". Al, Perhaps you should include a link to the previous thread if you don't want repeat or rehashed advice.
 
ctlikon0712 said:
Al, your engine is counterbalanced and has a vibration? Sounds to me like you should find the problem not seek somthing to mask it. I didn't read your prior thread but I would check the internals and the flywheel area for the problem.....

Good luck
Click to expand...
As do all Model A engines, counterbalanced or not.
 
The explanation for vibration in a 4 cylinder engine that is most logical to me is one I heard long ago: In a 4 cylinder inline engine, all 4 pistons stop and start at the same time, twice per revolution. I know it is not an engineering explanation, and I know nothing about harmonics, but it seem logical that with all pistons stopping and starting at once, it might cause vibration at some point. I have noticed that 6 cylinder or 8 cylinder engines do not have the same problem, so that explanation may have merit. If it is true, than it would seem that the vibrations we notice in the model A are inherit, and "normal", and the best we can do is mask them, isolate the engine from the car the best we can, and drive at the RPM range that avoids the most vibration.
 
CarlG said:
I have one of these, not really sure what it does or doesn't do.
Click to expand...

I too have never figured that one out. The flywheel (which is a heavier mass than the dampener) is on the same end as the dampener. The "whip" or flex is in the crank throws. In the opinion of many that I have spoken with, the dampener would only be effective if it is on the opposite end of the crank from the flywheel mass. Does anyone know of any other type O.E. engine that uses the dampener located within the flywheel?
 
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