Harmonic damper balancing

[Gary Schulz]

I just bought a MS two piece pulley/harmonic balancer for my S and I had a question about balancing this assembly. Everyone recommends balancing this unit for best operation but how do you guys do it? Do I need to machine a pair of cones and a shaft to run it statically on a pair of straight edges? Seems like a lot of work for a one-off job.

The other thing that is a bit bothersome to me is the fact that when I chuck the harmonic balancer piece in my lathe and take a look at how true it is running, I notice the the machined outer weight (the turned piece) is eccentric to the pressed steel inner disk by about 15 thousandths. It would seem to me that this would be cause for much imbalance to start with given the the basic geometry is off by this much. Looks to me like when the two pieces are fixtured during the rubber bonding/molding process, that the two are not held in perfect concentricity.

This part was recommended by several on the forum instead of me using my old original part but at least my old original seems to run fairly true.... i don't believe you can do any post machining (turning) of that outer weight because it is floating on rubber and will wind-up and move around during any turning operation making it pretty risky for chatter or tool grabbing.

Not sure if I am overly impressed with this new MS harmonic balancer...

Thoughts?

Gary

[Spider]

You can machine it, just use a fine tip and take light cuts, however, all the same, it really should be better than this.

I dynamic Balance them in my friend's Balancer, but not everyone has access to one of these, so could mean send it off for balancing.

Other than this, I'd recommend having your original reconditioned (I think I suggested that previously?)

[dklawson]

Gary, as Chris suggested, there are some firms in the U.S. that will recondition harmonic balancers if you feel better about using the old part.

To each his own but I would not try and carry out balancing at home. You are not after a static balance but a high-speed dynamic balance. I have always taken the rotating parts to a machine shop and asked that they balance them. It's not expensive (compared to the rest of the rebuild) and the machine shops have the equipment to carry out the dynamic balancing.

A quick Google search for harmonic balancer repair found the following:
https://www.damperdoctor.com/
http://www.hbrepair.com/
http://www.winslowmfg.net/
and
http://harmonicdamperrebuilds.blogspot.com/

[Gary Schulz]

Gary, as Chris suggested, there are some firms in the U.S. that will recondition harmonic balancers if you feel better about using the old part.

To each his own but I would not try and carry out balancing at home. You are not after a static balance but a high-speed dynamic balance. I have always taken the rotating parts to a machine shop and asked that they balance them. It's not expensive (compared to the rest of the rebuild) and the machine shops have the equipment to carry out the dynamic balancing.

A quick Google search for harmonic balancer repair found the following:
https://www.damperdoctor.com/
http://www.hbrepair.com/
http://www.winslowmfg.net/
and
http://harmonicdamperrebuilds.blogspot.com/

Thanks for the pointers... Yes, all I can do is static balancing so I will probably either give it to my machine shop who has folks that do dynamic balancing on rotating parts or I may try one of these places in the links. At the same time, I may also have my old one rebuilt. I was surprised at how eccentric the weight is on this new one. My experience at trying to make even the lightest cuts on something that can deflect (even a very tiny amount) leads me to believe that you really can't true this outer ring after it is bonded in-place. I have learned a great deal of respect for what happens to parts in lathes, because that outer ring will have a tendency to shift (all it takes is a microscopic amount) and will want to "walk" on top of the cutting tool. A recipe for disaster, at least for me!

I think the correct way to machine this outer weight is to use a tool-post grinder which will not bite on the outer edge of the ring. I may try to rig this up just to make the part run true.

Little stuff like this just bugs me and I feel like I need to make it right...

Gary

[Terrapin-52]

HI Gary

are you using a 3 or 4 jaw chuck in the lathe to check the runout on the crank pully

regards mike

[Gary Schulz]

3 jaw clamping on the inside of the inner hub assembly. runout is relative to this center hub section this way I can indicate on both the center section (around .001 runout) and compare to the outer ring (around .014).

EDIT: These measurements are made on just the harmonic balancer part and do not include the pulley.

[Gary Schulz]

I redid the measurements but this time on the complete assembly. I have 0.014 to 0.015 runout on the harmonic balancer outer ring compared to the edge of the V-belt pulley which is around 0.001. Don't worry, it is clamped very lightly so there is no scoring on the seal surface!

20190110_075358_resized.jpg

I guess I can have the rebuild place just re-rubber this new ring and make it concentric but that is a little disappointing on a brand new part.

[ricardo]

A few months ago I managed to go to 0.002" runout using a new MS damper by just carefully centering the damper on the pulley.

Lookup for dynamic balancing on the forum and you'll find a long thread about it started by me. In fact, I just balanced my whole rotating assembly the other day and should update the thread.

[Gary Schulz]

A few months ago I managed to go to 0.002" runout using a new MS damper by just carefully centering the damper on the pulley.

Lookup for dynamic balancing on the forum and you'll find a long thread about it started by me. In fact, I just balanced my whole rotating assembly the other day and should update the thread.

I could improve this somewhat but I would need to open up the hole in the center of the damper in order to allow for the damper location to be compensated relative to the pulley. Right now it is an exact fit (which it should be) so there is zero play between the two pieces. I hate to just oversize the centering hole in an effort to have the harmonic damper float and only be located by the bolts. I prefer to have the location determined by the geometry of the parts and just use the bolts to clamp the two pieces together. With this much eccentricity, it is pointless to chase my tail trying to balance the thing....

The rest of my engine has been balanced (crank, rods, pistons etc). the only things not balanced are my flywheel since I am still messing around trying to figure out which one to use and of course this new pulley/harmonic balancer.

[Spider]

Gary, once the happy place is found, you could always pin them

[Gary Schulz]

Gary, once the happy place is found, you could always pin them

Yes, that would be a good compromise.

[Hipwell]

viewtopic.php?f=3&t=22559&p=207459#p207459

Looking at the post balancing photos at the end of this thread, these dampers must have a real problem.

I clocked up a standard small diameter one piece Cooper damper in the lathe and it was out roughly 8 thou.

[Gary Schulz]

viewtopic.php?f=3&t=22559&p=207459#p207459

Looking at the post balancing photos at the end of this thread, these dampers must have a real problem.

I clocked up a standard small diameter one piece Cooper damper in the lathe and it was out roughly 8 thou.

Yes, I am in agreement that these MS Cooper S dampers are actually pretty bad. I just don't have many choices here and returning an item all the way back to the UK is costly so I am looking to make lemonade out of this....

I thought several folks thought these parts were good so maybe I just got stuck with a junk one?

My first priority is to get it true (or at least close) and then deal with balance.

[winabbey]

Have you started a discussion with MS re your concerns?

[Gary Schulz]

No, but I would assume the best case would be for them to take it back and that will probably be too costly for me to ship so I think I will see what I can do to just fix it. Probably foolish but like many parts for these cars, you need to fix them up for them to work right...

[dklawson]

I understand your not wanting to send the part back to MS. It is much less expensive to ship an item from the U.K. to the U.S. than from the U.S. to the U.K.

If you can dress the balancer's OD to reduce the eccentricity, the remaining problems will be addressed by having the assembly dynamically balanced. A tool post grinder would certainly work but single point tool making light cuts will also get you there.

Incidentally, somewhere in my past I came across a clamp block for a lathe. Someone had made the clamp block to hold a Dremel tool so it could be used as a tool post grinder. I don't think a Dremel was the best choice but the same concept could be applied to adapt a proper die grinder for the task.

[winabbey]

No, but I would assume the best case would be for them to take it back and that will probably be too costly for me to ship so I think I will see what I can do to just fix it. Probably foolish but like many parts for these cars, you need to fix them up for them to work right...

I understand, but you seem unhappy with the item you received and unsure if it's faulty or exactly the same as all others MS sell. Maybe ask MS the same question you asked here about whether this damper should or could be balanced and, if so, how. If not, why not? Just suggesting the vendor be included in discussion of your dilemma.

[Gary Schulz]

No, but I would assume the best case would be for them to take it back and that will probably be too costly for me to ship so I think I will see what I can do to just fix it. Probably foolish but like many parts for these cars, you need to fix them up for them to work right...

I understand, but you seem unhappy with the item you received and unsure if it's faulty or exactly the same as all others MS sell. Maybe ask MS the same question you asked here about whether this damper should or could be balanced and, if so, how. If not, why not? Just suggesting the vendor be included in discussion of your dilemma.

What you say makes complete sense and I think I will at least send them an email summarizing things.

Doug,

My "tool post grinder" is actually a bracket that gets clamped to the cross-slide that holds a Dremel! Real tool post grinders are kind of expensive...

Gary

[Gary Schulz]

Instead of a Dremel, I was able to clamp a cheap miniature bench grinder to the cross slide using T-nuts and studs. This should do very nicely and I am certain I could get the runout down to pretty much zero using this setup. I am not cutting anything until I think this through some more however.

20190111_084831_resized.jpg

20190111_084808_resized.jpg

I am also doubting why dynamic balancing would be any different than static balancing in the situation where the object is very thin like this damper. In dynamic balancing you resolve the problem by figuring out the correct angle and length along the axis of the object where you would add or subtract weight. When the object has basically little to no "length" then the balance point must be on the actual outer ring of the damper. It can't be anywhere else I don't think so I would most likely be drilling a small/shallow hole somewhere on the circumference of that ring wouldn't I? Wouldn't static balancing indicate that point?

Gary

[dklawson]

I suggest thinking about it as the difference between bubble balancing and dynamic balancing a tire/rim. You can bubble balance tire/rims but you are not addressing the vibrations occurring at the resonant (harmonic) frequencies of the assembly. For relatively low speed you can get by with static balancing. For high-speed assemblies you want to address the harmonics.

BTW, is that the HF 3-3/4" bench grinder with the flexible shaft?