tunable vibration absorber

[Kevin Jenness]

I came across a reference to this adjustable anti-vibration device dreamed up by Jerry Glaser. Do any of you have experience using such a thing"

 

[Dwayne Watt]

I have no experience with this setup, but what he has done is create a tunable spring mass damper. The rod is essentially a spring. The damping frequency is adjusted by moving the mass (weights) along the rod to find the optimum point at which damper counteracts the lathe vibration. This contraption should work just as well with the mass pointed downward out of the way.
It takes very little offset rotating mass to excite the machine when the first mode natural frequency is encountered. Adding mass to a lathe lowers its natural frequency making it easier to pass through that frequency and get closer to second or third modes which tend to be lower amplitude vibrations. The idea here is to be able to run the lathe faster with unbalanced stock mounted and not adding a lot of mass (weights) to the lathe.

 

[Kevin Jenness]

I understand the principle, I just want to get some user feedback. I saw a post from John Lucas saying he had used one but abandoned it because it needed frequent adjustment as material was removed from the workpiece. Seems like it would be safer than a backplate with screwed-on counterweights that some use but perhaps more touchy. I currently am using a Kelton Balancer, a hub with threaded spindle and integral moveable weights weighing at least 30#, but it is limited to relatively small work,

 

[odie]

I saw a post from John Lucas saying he had used one but abandoned it because it needed frequent adjustment as material was removed from the workpiece.

^^^^^ John Lucas is correct. The vibration intensity does change as material is removed.

Rather than adjusting weights, I've found it much easier to adjust the rpm to suit the current vibration level, during the process of removing material. This usually doesn't require more than a couple of adjustments during the span of roughed bowl to finished bowl. (Normally a bowl doesn't benefit from finite rpm adjustments during the roughing stage.)

Here is a thread where I came to develop my own homemade "vibrometer"....and, grateful thanks to @Clifton C for coming up with the initial idea......which I modified slightly.

Lathe vibration detector ideas please!

I am looking for ideas for devices, or inventions for detecting minor vibrations on the lathe. The purpose is to adjust the rpm to where the least possible vibrations are present. Right now, I use my fingertips on the lathe bed, plus there is one long neck spot lamp that consistently gives me...

www.aawforum.org

^^^^^ There are 3 pages of discussion in the above link, and if any turners are interested in fine tuning lathe vibrations, as it relates to one specific chunk of wood, it would be highly recommended to check this thread out.

I've had my vibrometer in constant use since that thread in 2019, and have found it absolutely indispensable for fine tuning lathe vibration according to one specific piece of wood.

Here's my vibrometer:


-o-

 

[Kevin Jenness]

Odie, I am sure you are right about bowl turning. As you can see from the photo above I am intentionally turning some unbalanced pieces on multiple axes and as such I need counterweights or possibly the damper linked above -or both- to get the vessels spinning fast enough for efficient hollowing.

 

[Bob Brown]

 

[Dean Center]

Here's my vibrometer:
View attachment 65732 View attachment 65733

-o-

Hey, Odie, maybe the answer is in that coffee machine. You just need to adjust the amount of caffeine intake to create a vibration internal to the turner that counteracts the vibration from the lathe. Kind of like noise cancelling technology.

 

[Kevin Jenness]

Added a back plate to the Kelton hub and was able to spin the workpiece smoothly at 500 rpm. The adjustable weights on the hub make it easy to fine tune the static balance. Vicmarc makes a somewhat similar, though lighter, rig. Vicmarc balancing system

There is a lot of force embodied in a rotating system like this, not to be taken lightly. I feel I have the hub, backplate and counterweight solidly connected but I will be checking the fasteners and staying out of the line of fire. I have the main control box below the headstock and an on-off switch at the other end of the ways.

 

[Tim Hunter]

The Glaser apparatus is more of a science project than a practical solution. You would spend more time tuning than turning.

Tim