Vibration Damper/ Harmonic Balancer

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Model T Ford Forum: Forum 2005: Vibration Damper/ Harmonic Balancer
Top of pagePrevious messageNext messageBottom of page Link to this message  By Arnie on Monday, March 03, 2008 - 08:23 pm:

Many new vehicles have a device that reduces the harmful torsion/twist effect on the crankshaft because of the uneven load from the piston after the spark plug ignites the fuel mixture. Since the Model T Ford crankshaft has, relatively speaking, small diameter journals for the main bearings, has anyone considered attaching some sort of vibration dampner/harmonic balancer to the front of the crankshaft. Perhaps it would be tight space wise, but with a number of cranks breaking it might be worth the effort. What do you think?

Or has this already be done without success?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ken Kopsky on Monday, March 03, 2008 - 09:06 pm:

Interesting idea but I doubt the T crank produces harmonics that would benefit from a dampener. The engine speed is low and the mass on the other end absorbs vibrations. (When it's not creating it's own.)

But...I wonder. Maybe try it by filling the front pulley with lead or a cushioned lead ring? I'd be willing to try it but my engine assembly is a ways down the pike.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Thomas J. Miller on Monday, March 03, 2008 - 10:44 pm:

For a damper to have any effect, the inertia ring has to be a significant diameter. There isn't enough room in the nose area of the pan to package a damper.

One of my T-engines had a lead ring on the pulley that increased its diameter by almost a half inch. When I got the car, the lead was already cracked and was loosening from the pulley. I didn't notice any difference when it was there.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Mike Walker, NW AR. on Monday, March 03, 2008 - 11:20 pm:

Maybe that's what was accomplished by the accessory Dunn counterweights attached to two points on the crankshaft. Isn't a harmonic balancer just another flywheel? The Dunn counterweights were two more flywheels.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Thomas J. Miller on Tuesday, March 04, 2008 - 07:12 am:

A harmonic balancer is a damper that has an rubber ring between the hub and the outside weight. The ring oscillates to counteract the vibration of the crank.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Seth Harbuck on Tuesday, March 04, 2008 - 02:52 pm:

Attaching a harmonic dampener with that 3/8" diameter pin arrangement would be the biggest hurdle to overcome, in my opinion.

There are oscillations that a dampener could help absorb and they are there because of the "flimsiness" of the tiny-journaled crankshaft, but due to the low speeds the dampener would have to be huge and there simply isn't enough room as Tom said. Again, in my opinion.

Your best bet to prevent crankshaft oscillations is way larger journals and large connections between them and no counterweights, the last of which creates other problems. A third time, in my opinion.

Seth


Top of pagePrevious messageNext messageBottom of page Link to this message  By Chris Barker on Tuesday, March 04, 2008 - 03:36 pm:

A harmonic damper only addresses torsional vibrations. They were invented (by Fred Lanchester)to counter early problems with 6 cylinder engines where the forcing frequency was 1.5 times higher than a 4 cylinder (because it has 6 cylinders) and the natural frequency of the crankshaft in torsion was lower than a 4 cylinder (because it was longer), so 6 cylinder engines have a 'period' somewhere in their rev range where resonance occurs. Edwardian Napiers had what they called a 'power rattle' at about 1100rpm for instance.
4 cylinder engines do have these dampers, but only to counter problems at much higher rpm.
In the case of the Model T:
- They rarely go above 1600rpm (unless modified)
- The torsion frequency will be well above the associated forcing frequency (for 1600rpm this will be 53 cycles/sec).
Moreover, my understanding is that most T crank problems are caused by bending, not torsion - misaligned 4th main bearings etc.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Seth Harbuck on Tuesday, March 04, 2008 - 04:26 pm:

The "diamond" crankshaft (pre "improved-cars") which is soft compared to the AISI 1071 steel one, plus iron pistons, plus 2400 rpm (right before one shifts from low to high) and I'll bet there is plenty of torsional vibration.

Yes, the T is a four banger - with a crankshaft more than 20" long from the rear of the front main bearing to where the flywheel bolts on. Mighty long in my opinion to have 1.25" journals and boat anchors for pistons.

Would a harmonic dampener save a T crank from destruction even if it could be fitted? No, I don't think so either. A far better use of redesign time would be coming up with a pan about three times as stiff as the one that came with the car. Then, when you slapped a big journal crank in there, you'd have something.


Top of pagePrevious messageNext messageBottom of page Link to this message  By arnie on Tuesday, March 04, 2008 - 07:26 pm:

Yes, I agree that larger journals on the crank would help reduce the breakage problem. That is an expensive and time consuming effort.

When one looks at the literature with cranks twisted in a knot (I think to show off the vanadium steel) and not fractured, it indicates that the material is tough. I think that perhaps cycling of the metal (fatigue) may add to the crankshaft breakage. Even with low rpm, perhaps over time, cycling of the crank metal causes failures. That is why I brought up the vibration damper. Many modern 4 cylinder engines with larger journal diameter cranks have a vibration damper so I would think it has some benefit.

And certainly misaligned 4th bearings are a factor.

The vibration damper is different that the counterweghts. The damper has an inertia ring that speeds up or slows down relative to the crankshaft to reduce the effect of the torsion variation due to the pulses from the piston firing. My thought was that reduced torsion cycle values on the crank my improve its life.

Thanks for all your inputs. My idea was to see if anyone had found a way to put a damper on the front end of the rather tight area in the front of the Model T crank. I think that a Winfield vibration neutralizer was used as an accessory on a Model A (can I mention that vehicle here???), but I do not know if it was successful or not.

Ok all you engine designers out there any more comments???

Thanks,

Arnie


Top of pagePrevious messageNext messageBottom of page Link to this message  By Thomas J. Miller "Tom" on Tuesday, March 04, 2008 - 07:48 pm:

If you want to do it right, go with two counter rotating balance shafts rotating at twice crank speed to counteract the second order vibrations. A vibration damper will never balance a straight four cylinder engine no matter how many counterweights you throw on the crank. In addition to the chains or gears driving these balance shafts, you'll need to add a pressurized oiling system to lube these high speed parts. And if you go through this much trouble.... Beef up the crankshaft with "way larger journals" and beef up the cheeks between those journals. Of course you'll no longer have a T engine by then.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Seth Harbuck on Tuesday, March 04, 2008 - 07:57 pm:

I think you stopped having a T engine and had a stroked Mitsubishi 2.6 when you added the balance shafts.

Seth:-)


Top of pagePrevious messageNext messageBottom of page Link to this message  By Thomas J. Miller "Tom" on Tuesday, March 04, 2008 - 08:13 pm:

Seth, What's a Mitsubishi? Didn't they make fighter planes during WWII? I was thinking more along the lines of the 2.3l Duratech I-4 with its balance shafts in the pan. We're a T group so think Ford first.

Regards,
Tom


Top of pagePrevious messageNext messageBottom of page Link to this message  By Seth Harbuck on Tuesday, March 04, 2008 - 08:25 pm:

Tom,

Well, in this case, Mitsubishi thought first and patented the balance shafts. Nobody could use them without paying patent royalties to Mitsubishi for many years. Porsche chose to with the 944's engine.

Sorry, I'm not a "Ford guy" - the 89 year old is the one and only I'll ever own. I might consider a 2.4 liter Ecotech from the General someday, but only if they stopped making their pushrod V-6s.

Seth


Top of pagePrevious messageNext messageBottom of page Link to this message  By Thomas J. Miller "Tom" on Tuesday, March 04, 2008 - 08:43 pm:

Seth,

You've got me with Mitsubishi and their patent around 1975. We both know the concept is basic physics and is much older than that. However, I'll be danged if I can find some American example from the 20s or 30s where they had one.

Enough talk, I'm going to the garage....

Tom


Top of pagePrevious messageNext messageBottom of page Link to this message  By Hap Tucker on Tuesday, March 04, 2008 - 09:18 pm:

For us “non-engineer” types “Wikipedia’s” short version of the subject (probably flawed with some errors – but with little background on the subject – I felt better for reading it.) http://en.wikipedia.org/wiki/Torsional_vibration

I don’t think pulley/damper size would be a limiting factor on the pre-Ts. For the NRS Fords shown below, the flywheel and fan were combined so plenty of width for something to be added. The two-cylinder Fords also had a fairly large open flywheel.



On my 1931 Model A Ford – prior to having the engine rebuilt it vibrated quite a bit. When I had then engine rebuilt, I had it balanced (flywheel, crank, pistons, rods, -- I believe the flywheel and crank were balanced dynamically also – but that was many years ago so I don’t remember for sure). I discovered that it now was smoother in some RPM ranges, but it actually vibrated more at the RPM range that equated to 43-45 mph which is where I previously liked to cruise. At that time I was looking into trying to obtain a harmonic dampener to see if it would help. But before I obtained one to install, I switched over to a Model B engine with the counterweighted crankshaft. (It also had been balanced). Less vibration at my cruise speed of 43-45 so I quit looking for a harmonic dampener.

Sacramento Ford sells a functional replica of the CRANK PULLEY/VIBRATION NEUTRALIZER WINFIELD 1928-34 at: http://www.vintageford.com/sect_search.cfm?LineName=Hot%20Rod&Line=Hot%20Rod&Category=Engine&StartRow=61&PageNum=4 but as pointed out already – it probably would not fit on the front a T that had the stock oil pan attached to the block. It probably would if you changed the front of the oil pan. Could a slot be cut in the pan to allow it or something similar to fit and then the front be reinforced so it would still hold the engine to the frame? Or a different mounting?

A related idea that I saw on a Hiller helicopter was the use of a liquid mercury filled damper/balancer for the main rotors. The helicopter still vibrated, but it supposedly helped control the vibrations.

Over the past few years I’ve read about liquid mercury filled balancers/dampers for experimental aircraft such as:
I don’t remember what site I pulled the following but it shares about the use of such a balancer and after that I have the links to that “Sun-Tech-Innovations” balancers.
June 10, 2002
When we began testing the engine vibrated enough to blur the carbs... We have adjusted the motor mount bolts to bring the rubber bushings in contact with the tubes and compressed 1/8" on each side of the firewall... A careful adjustment is important for proper vibration damping - do not over tighten these bushings... We put a wide area washer between the engine case and the rubber bushings on the bottom mount bolts because the case did not give support around the full circumference of the bushing... We have installed a Sun-Tech Innovations balancer under the prop crush plate... This addition changed the vibration enough to let the carbs work properly - they were not flowing fuel when the carb slides were more than half open... The engine vibration is modest at idle and not noticeable above 2500 RPM at this time with a ragged spot between 1200 and 2000 RPM...
The product is described a little at:
http://www.balancemasters.com/ultralights/index.html

http://www.balancemasters.com/driveshafts/index.html

I wonder if one of the drive shaft balancers might be small enough to be adapted?

http://store.balancemasters.com/osCommerce/product_info.php?cPath=28&products_id=38

I also wondered if installing the larger balancer on the flywheel side would be of any help? Or would it just duplicate what the flywheel is already doing?

It may turn out that for a stock T engine – it isn’t a problem/a single additional damper might not help anyway at the low RPMs and the low horsepower produced. But if someone could come up with something that was helpful in reducing the out of balance feel to the T engine – and was relatively easy to install (even if during engine overhaul) I would be interested in learning more about it.

Respectfully submitted,

Hap Tucker 1915 Model T Ford touring cut off and made into a pickup truck and 1907 Model S Runabout. Sumter SC.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Chris Barker on Wednesday, March 05, 2008 - 07:10 am:

Back to balancing shafts rotating at twice engine speed:

1. These were also invented and used by Fred Lanchester (my hero) before 1910!
2. They do nothing to reduce stresses in the crank - they create equal and opposite forces into the engine block so that the car feels smoother.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Thomas J. Miller "Tom" on Wednesday, March 05, 2008 - 07:39 am:

I've seen the engine with the flywheel/fan on the front of the crank. What a horrible place to put a flywheel. With it being over the front axle, any turning forces are going to sideload the front crankshaft bearing just like a gyroscope resists turning when you hold it in your hand. AND you have the clutch on one end of the crank and a rotating flywheel on the other. Talk about torsionals.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Jerry Hansen on Thursday, March 06, 2008 - 01:03 am:

We have a Clark fork lift built somewhere around the early seventies with a four cylinder
Waukesha engine, it has been ten years or more since we spun a rod and rebuilt the engine. It has either one or two (can't recall and don't have a parts book) gear driven balancers in the pan about a foot or so long that look like the blades on the old reel type lawn mowers. It is my opinion it is the smoothest four cylinder engine I have ever owned, particularly on high rpm's. Again if I recall correctly the blades are partly/totaly submerged in oil, for damping the vibrations and possibly for throwing oil through the bottom of engine. No way could it be installed in a T engine, thought it was an interesting concept


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