Lathe vibration detector ideas please!

[Mike Johnson]

Odie,

You will have some difficulties coming up with rules to live by when it comes to vibrations. Vibrations are a direct response to harmonic resonant frequencies that are generated by the design of the machine. This frequency can change based on RPM, weight of the billet, balance of the billet, wear on the drive belt, wear on the drive bearings, mounting of the machine to the floor, wear on drive pulleys, shaft alignments, motor alignments, belt alignments, bent shafts, motor faults, machine mass and weight, structural design of the machine, etc.

Mass and weight is the easiest way to overcome machine vibration, changing the RPM of the machine is the other most commonly used method to control vibration. Each time you install a new billet on the machine you are changing the equation, as the chips come off it will constantly change. If you have a large wood billet with a large dense knot on one side you will never eliminate all of the vibration unless you install a counter balance on the billet similar to mounting a weight on a tire that is out of balance. Each wood billet will be changing the equation as no two pieces of wood are the same. This can be your ZEN moment when you become one with the wood and accept each piece of wood for what it is, nature providing a unique raw art form for all of us to enjoy. Without the knots, voids, colors and grain variations wood would be very boring, have you hugged a tree lately?

 

[hockenbery]

RPM drops when you start to cut. The rpm change alone will change the vibration.

I saw Ron Gerton do a demo using strobe lights a couple of times. The strobe has the effect of stoping the turning. Ron had to use a timing mark and a dynamic stone that could adjust to changing rpm. One of the things he showed and talked about was that the RPM would drop when the cutting started. This happens will big lathes and small ones too. The cool thing about using a strobe was that working a Burl with a undulating surface you could see where you are cutting so you can leave parts you want to keep.

Just need to look at the vibrometer while cutting and adjust the speed to minimize the vibration while cutting.
I can do most cuts one handed and can adjust the speed while cutting and watching the vibrometer. Maybe combine it with video so to can watch the turning and the vibration at the same time

 

[Stan Semeniuk]

RPM drops when you start to cut. The rpm change alone will change the vibration.

I saw Ron Gerton do a demo using strobe lights a couple of times. The strobe has the effect of stoping the turning. Ron had to use a timing mark and a dynamic stone that could adjust to changing rpm. One of the things he showed and talked about was that the RPM would drop when the cutting started. This happens will big lathes and small ones too. The cool thing about using a strobe was that working a Burl with a undulating surface you could see where you are cutting so you can leave parts you want to keep.

Just need to look at the vibrometer while cutting and adjust the speed to minimize the vibration while cutting.
I can do most cuts one handed and can adjust the speed while cutting and watching the vibrometer. Maybe combine it with video so to can watch the turning and the vibration at the same time

This is why I like this forum so much! You old dudes make me feel so young.

 

[hockenbery]

This is why I like this forum so much! You old dudes make me feel so young.

Hey I represent that remark.
Be aware that old age and treachery will overcome youth and ambition every time!

Not sure if you understand RMD north of the border.
But we are there....

 

[odie]

RPM drops when you start to cut. The rpm change alone will change the vibration.

Morning Al.....

Actually, this isn't much of a consideration, since the cuts I'm concerned with are so light and delicate, that any change in rpm is negligible, if there is any change at all.

This whole discussion may start with an application of creative thought combined with a little intellect......but, the real test is in the real world results. I'm already getting a refined cut that very few turners will ever get without the dedication it requires, and it is this that allows me to turn without the need for aggressive sanding. My ornery attitude towards evaluating my own successes, keeps me from being satisfied, and continually pondering how to improve.

Vibrations are a direct response to harmonic resonant frequencies that are generated by the design of the machine.

Hello Mike.....

Perhaps my use of the word "harmonic" has you confused as to the vibrations I'm talking about. These are not related to how the wood reacts to the lathe, but solely how it reacts to speed, and how the long grain and end grain, combined with shape and ability to flex, resists, or reacts to centrifugal force.

-----odie-----

 

[odie]

This can be your ZEN moment when you become one with the wood and accept each piece of wood for what it is, nature providing a unique raw art form for all of us to enjoy. Without the knots, voids, colors and grain variations wood would be very boring

Really like your state of mind here, Mike.......

-----odie-----

 

[Mike Johnson]

Odie,

You can always use the old military approach adapt and overcome any and all problems that arise.

 

[odie]

Odie,

You can always use the old military approach adapt and overcome any and all problems that arise.

Yep, absolutely, Mike.......

I mentioned "rules" in one of my posts here.....and, when it comes to turning wood on a lathe, the rules are nothing but a predictable starting point. From there, adjustments almost invariably become necessary, as each piece of wood is different from the last, and will be different than the next. At this point, I have very little experience with the vibramometer.......but, I think it can help provide some additional perspective, or input to the equation......and I think might help connect a few of the dots!

-----odie-----

 

[Dennis J Gooding]

A splash of Cold Water. I don't believe that the rubber band mounted laser pointer is telling you what you want to know. The vibration of interest is the vibration of the workpiece itself. Ideally, you could mount a weightless light source on the work piece and look for the change in blurring of the image as you change lathe speed. That being difficult to carry out, the next best thing is to measure the vibration of the headstock or tailstock which is related (although imperfectly) to the vibration of the workpiece. Now, the frame of the rubber band mounted laser pointer, if securely fastened down, will track the vibration of the lathe where it is mounted. However, the motion of the laser pointer will not. It will respond as a separate dynamical system determined primarily by the mass of the laser and the spring constant of the rubber bands. Simply put, any increase of vibration of the laser pointer compared to the vibration of the frame of the device as you change lathe speed will be the result of resonances in the rubber band/pointer system not resonances of the workpiece/lathe system.

 

[odie]

A splash of Cold Water. I don't believe that the rubber band mounted laser pointer is telling you what you want to know. The vibration of interest is the vibration of the workpiece itself. Ideally, you could mount a weightless light source on the work piece and look for the change in blurring of the image as you change lathe speed. That being difficult to carry out, the next best thing is to measure the vibration of the headstock or tailstock which is related (although imperfectly) to the vibration of the workpiece. Now, the frame of the rubber band mounted laser pointer, if securely fastened down, will track the vibration of the lathe where it is mounted. However, the motion of the laser pointer will not. It will respond as a separate dynamical system determined primarily by the mass of the laser and the spring constant of the rubber bands. Simply put, any increase of vibration of the laser pointer compared to the vibration of the frame of the device as you change lathe speed will be the result of resonances in the rubber band/pointer system not resonances of the workpiece/lathe system.

Good morning Dennis!

It seems there is disagreement as to what, how, and why I'm attempting to measure these vibrations!

Well, toss all that out the window, and we should all acknowledge that the vibrometer is measuring something that is likely very usable from a turner's perspective......or, that's the way I perceive it, anyway! As I said, all this is in the experimental phase of just how I can apply this new found information to any possible new improvement these observations can help deliver.

Maybe I'm doing nothing more than barking up the wrong tree.......and, if that's the case, I'll find that out, too!

I've been doing a photo session, and adding some new listings this morning, and been monitoring this thread.....but, closing up now. Good to hear from you all. On my way out to the shop.......but, who knows......I may end up firing up the laptop while I warm up the shop!

-----odie-----

 

[Mike Johnson]

The industrial Biorefinery Complex that I work at use 1000's of Piezo type vibration sensors mounted solidly to the equipment in vertical, horizontal and axial positions to accurately measure "vibrations". We also use a triaxial type sensors that takes all of these readings at one time from a single mounted position and uses a complex algorithmic software to break the signal down into the (3) values. With the vertical, horizontal and axial values a trained analyst can decipher the information into an educated guess as to the source of the vibration. There are scientists that have PHD's in this discipline. Listening to an engineer go on for 8-hours of vibration physics and analysis you will end up walking away with a lot of knowledge but also have a headache.

 

[George Stratton]

Do you guys actually have any time left to do some turning???

 

[odie]

The industrial Biorefinery Complex that I work at use 1000's of Piezo type vibration sensors mounted solidly to the equipment in vertical, horizontal and axial positions to accurately measure "vibrations". We also use a triaxial type sensors that takes all of these readings at one time from a single mounted position and uses a complex algorithmic software to break the signal down into the (3) values. With the vertical, horizontal and axial values a trained analyst can decipher the information into an educated guess as to the source of the vibration. There are scientists that have PHD's in this discipline. Listening to an engineer go on for 8-hours of vibration physics and analysis you will end up walking away with a lot of knowledge but also have a headache.

Heh,heh,heh.......Ya, there is a point where the overload of techie information isn't likely to produce usable information for our particular discipline......I'd probably just tune out at some point, lest I get a headache, too! Ha!

At the same time, I'm thankful for those who do pursue the unknown, the bold and adventurous.....as opposed to those who only travel the known paths!

-----odie-----

 

[Richard Hodsdon]

All this high tech of vibration checking reminds me of having my car serviced many years ago. The Italian Car Center worked on any make (mine was a Ford) but had Italian trained mechanics . One in particular had been trained by Ferrari and I remember coming in to pick up my car. This Mechanic was busy tuning a 12 cylinder Ferrari of Lamborgini in the bay next to mine. He was tuning it by ear and eye. His device was to place a lighted cigarette (no HSE officers around) on the vehicle and adjust the carbs until the smoke rose in a perfectly straight line. As he adjusted it you could see a slight wavering of the smoke at the tip which disappeared as he got it perfect. That was old fashioned vibration detection.
And he used to put the same effort into my Ford, something the agents never did.

 

[Mark Jundanian]

It’s new……It’s amazing…..It’s amazing and new…
.
It’s the new, MK1 mod2
.
odie inspired……… “LATHE VIBROMETER”.

I think the laser measuring tools are the best home laboratory answer, but, Clifton, I didn't understand the purpose of mounting the laser on rubber bands?

 

[stu senator]

I think the laser measuring tools are the best home laboratory answer, but, Clifton, I didn't understand the purpose of mounting the laser on rubber bands?

The band's amplify the natural frequency of the bands if the lathe head stock of that frequency is reached. (The harmonic frequency of The rubber band support system.)
The interest is really at the point the tool meets the wood.
Perhaps some sort of strobe set to the RPM or some multiple of the RPM.
Or a laser pointing at a polished spot on the tool reflected on a screen in sight of the turner.

Stu

 

[Clifton C]

Mark, Just a feeling I guess. Knowing a tuning fork will start vibrating from nearby vibrations, something about sympathetic vibrations, and then thinking about harmonics, I just thought that having the laser hard mounted to the lathe was headed in the wrong direction. So the other direction was soft mount or, something that would move, maybe even amplify the vibration. A picture of a science class barometer made with a balloon stretched over a mason jar with a straw pointer came to mind, discounted that and went back to the laser I already had mounted on a light already in use. Its original purpose was to point out a ridge or blemish in a bowl without having to mark with a pencil. It also ended up giving a visual of lathe vibrations. Listening and feeling work, but now I had a visual.
Used all the time? No. Just another tool in the tool box.

Then odies question and I started thinking of refinements, then retirement, then dollar signs, a movie deal… Oops, I digress…


So here is a side by side The OLVM and a no name laser hot melt glued to the head stock. The vibration generator is a chuck with a magnet on the inside of one of the jaws. the speed is somewhere in the 17 to 3900 rpm range. The lathe is my traveling lathe, used because as you can see, it’s mounted to a chop saw cart with built in vibration capabilities. The hard mounted laser shows no useful data, other then showing the OLVM does...
Ps This is probably not useful when roughing bowls...

 

[odie]

Ps This is probably not useful when roughing bowls...

You're right, Clifton.......not useful at all when roughing bowls. Making extreme effort to refine the cut there is wasted because the surface will ultimately be removed later, after seasoning. This doesn't mean that any normal care in making the cut isn't appropriate......because torn grain actually disrupts the grain below the surface. This should always be avoided, but there is a point where there are diminishing returns to invest the effort it takes to refine the surface to "ready for sanding".

Since making my "vibrometer", I've finished off a couple bowls. The one I finished yesterday was a large maple burl with a small foot, and a detailed undercut rim. This burl is the kind of bowl that traditionally has weight/balance issues for me. The vibrometer helps to fine tune the rpm better than my previous methods......but, is it better in practical application? I think it is, but at one point, I noticed a felt vibration with my fingers on the bedways, that didn't show up on the vibrameter. As before, it may end up being a help, but ultimately, a variety of sources for detecting vibrations may be the way to go.....

-----odie-----

 

[robo hippy]

I thought of this thread last weekend. I was in an antique shop and saw some thing that had to be a vibration indicator, but didn't get a picture... Anyway it was a vertically mounted spring. Not stiff, but not like a slinky, more like the old springs on screen doors before we got those spring piston things... It sat about 6 inches high and had a little 'deelybobber' hanging off the end of the spring....It vibrated as I walked by on the wood floor....

Like the laser pointer hot melt glued to the top of the lathe idea too...

robo hippy

 

[Mark Jundanian]

Mark, Just a feeling I guess. Knowing a tuning fork will start vibrating from nearby vibrations, something about sympathetic vibrations, and then thinking about harmonics, I just thought that having the laser hard mounted to the lathe was headed in the wrong direction. So the other direction was soft mount or, something that would move, maybe even amplify the vibration. A picture of a science class barometer made with a balloon stretched over a mason jar with a straw pointer came to mind, discounted that and went back to the laser I already had mounted on a light already in use. Its original purpose was to point out a ridge or blemish in a bowl without having to mark with a pencil. It also ended up giving a visual of lathe vibrations. Listening and feeling work, but now I had a visual.
Used all the time? No. Just another tool in the tool box.

Then odies question and I started thinking of refinements, then retirement, then dollar signs, a movie deal… Oops, I digress…


So here is a side by side The OLVM and a no name laser hot melt glued to the head stock. The vibration generator is a chuck with a magnet on the inside of one of the jaws. the speed is somewhere in the 17 to 3900 rpm range. The lathe is my traveling lathe, used because as you can see, it’s mounted to a chop saw cart with built in vibration capabilities. The hard mounted laser shows no useful data, other then showing the OLVM does...
Ps This is probably not useful when roughing bowls...

Humor me. What was the size of the dot produced by the hard mount laser with the motor off as compared to lathe running?

 

[odie]

One thing that is a consideration in your thinking, Mark.....is the vibrometer is holding the laser with 4 rubber bands, at 8 points of contact. I can say for sure, that the visual indications of the laser mounted this way, are coinciding with what I can detect with the spot light and felt through my fingers. The vibrometer is more sensitive, but appears to be responding to the same vibrations that can be detected by other methods......

-----odie-----

 

[Clifton C]

Here are the pics, from off, running, vibrating and dialed in...
Dot on left is laser glued to head stock, dot/dash/oval to right is OLVM.
First two are out of focus, but the dots are just sitting there. Pic three and four show hot melt glued on laser as still just a dot
while the OLVM shows vibration as an oval, then, as the speed is increased thru the vibration, the oval shrinks to a small dash.
Size of dot in pic three? Heavy 1/16th not quite an 8th.

Lathe off.....................Lathe on.....................Turned up to vibrate....turned thru vibration

 

[Clifton C]

Stu, I'm sure you are right in your assessment, however I cannot get there being as cheap as I am

 

[odie]

So here is a side by side The OLVM and a no name laser hot melt glued to the head stock.

Clifton.......since you have a laser hot glued to your headstock, and a "vibrometer", I'd be interested in seeing you compare the readings you get when using both at the same time. I have another laser attached to a magnet, and along with my vibrometer, did this test this morning. What I found is what I suspected......the vibrometer is more sensitive. The vibrometer detected a vibration that was also detected by the spot lamp, while the second laser did not see this vibration.

My opinion is still forming, but as I said before, the vibrometer is definitely useful for my needs.......along with my fingers on the bedways, and the long neck spot lamp.

-----odie-----

PS......By the way, I'm really cheap, too.......

 

[Clifton C]

odie, I glued that laser on this morning after reading Mark Jundanians post #55 asking about why mount with rubber bands. I thought I knew what would happen hard mounted, but not 100%, so, easy experiment, and now we know, a dot. I might not be understanding the question but here are both lasers shown mounted on the head stock and then the results, both lasers on the wall at the same time.
Lower left is glued laser, upper right is vibrometer

 

[odie]

Lower left is glued laser, upper right is vibrometer

OK, thanks for doing this experiment right away, Clifton.
It does appear that the vibrometer is a bit more sensitive for you, too. Is that the way you read the result?
It doesn't look like the glued laser is detecting anything in either of your photos.
How do you sum up the results you are gettng?
Do you think the vibrometer is reading from the rubber bands only, or detecting actual vibrations felt at the headstock?

-----odie-----

 

[Clifton C]

The glued to the head stock laser showed a dot thru all of todays trials, moved and taped to the body of the Vibrometer it showed a dot while the vibrometer showed an oval. I think the rubber bands are playing a part, they let the body of the laser oscillate in harmony with lathe vibrations. The vibrations produced by the vibration generator (pic 2 post 57) are vibrations I would expect from an out of balance turning, as opposed to out of round. I think the vibrations are from the turning, to the head stock, to the Vibrometer. As an experiment I marked the rheostat after dialing in the smallest oval. I could get back to that spot using the Vibrometer but was just in the vicinity when searching by sound and feel...
To my thinking it works, and seems to be more accurate then fingers and sound. But, fingers and sound are quick and easy and still pretty darn close, and sometimes that's good enough. There are two in use, we'll know in a couple of months...

 

[Russell Nugent]

Won't the rebound of the elastic bands, however small affect the results?

 

[stu senator]

Has anyone tried to calibrate the rubber band vibrometer RBV?

1 On the lathe with nothing mounted run thru all speeds slowly and see if you get any vibration of the RBV.
2 mount a chuck and repeat.
3 Put a magnet on the chuck to get an imbalance and repeat.

That should give you a base of the response of the RBV. You will see if it is really working or it is a result of the system or the RBV. You can also compare the results with your hearing and fingers.

Stu

 

[Clifton C]

Yes, but in a positive way. The "rebound" of the elastic bands let the body of the laser oscillate with the vibrating frequency of the lathe, the laser light shining on the wall shows this. As the lathe speed is turned up or down, the vibrating frequency of the lathe changes and the laser light showed this change as a larger or smaller oval scribed on the wall. as shown in posts #57 #62 and #65

 

[stu senator]

As the lathe speed is turned up or down, the vibrating frequency of the lathe changes and the laser light showed this change as a larger or smaller oval scribed on the wall. as shown in posts #57 #62 and #65[/QUOTE]

The large circle is the natural frequency of the RBV.
Stu

 

[Clifton C]

Stu, The large oval was at max vibration using vibration generator shown on post #57 pic two.
Without the magnet, you get a pretty nice dot thru all speed ranges.
Post#62 showes Lathe off .......Lathe on.....Turned up to vibrate....turned thru vibration.
The laser dot lower left is from a laser hot melt glued to the headstock.

 

[Russell Nugent]

Yes, but in a positive way. The "rebound" of the elastic bands let the body of the laser oscillate with the vibrating frequency of the lathe, the laser light shining on the wall shows this. As the lathe speed is turned up or down, the vibrating frequency of the lathe changes and the laser light showed this change as a larger or smaller oval scribed on the wall. as shown in posts #57 #62 and #65

What I mean is couldn't the rebound actually cause the vibrations to look worse than they really are. I'm no scientist.

 

[Clifton C]

Russell, me neither. Hanging out in the shop, or discussing this at the galley table, some of this would be obvious. This exercise in vibration detection isn’t for a chainsawn, out of round bowl blank but for vibrations that some folks wouldn’t even notice or even care about. On odies bowls with the incised detail on the rim, a small almost undetectable vibration would cause a discrepancy of a few thousandths of an inch, noticeable and unacceptable, and something that could not be sanded into submission.

I believe the laser hot melt glued directly to the head stock is oscillating, I just cannot see it. Maybe if I shot it across the street, as in got some distance on it I might be able to see some movement. But then the neighbors would call the police etc. etc. I think the elastic bands are amplifying the vibrations or “making them worse” which is why they are visible, represented by the oval. Bigger vibrations equal bigger oval, smaller vibrations equal smaller oval. Now with a visual it can be “dialed” in.

 

[Clifton C]

On odies bowls with the incised detail on the rim, a small almost undetectable vibration would cause a discrepancy of a few thousandths of an inch, noticeable and unacceptable, and something that could not be sanded into submission.

Odie, I should have asked if this is a true statement, sorry to presume...

 

[odie]

Odie, I should have asked if this is a true statement, sorry to presume...

Yes, I believe so, Clifton.....

The bowl must be spinning as true as possible in order to get the best final cut that is possible. Any vibrations tend to reduce the results that are possible. Other things, such as sharpness, presentation, technique, etc., are also a part of the overall equation.....so, getting that one best refined rpm is only one element of the whole package. Any one of those elements not at the best advantage will nullify any advantage to be had by ALL of the other elements.

As for sanding......just about any surface can be "sanded to submission", but the more sanding required, the more surface is removed. The more surface removed, the further from "perfect geometry" it gets. The further from perfect geometry it gets, the less aesthetically pleasing to the eye, the details, or crispness of surfaces, corners, edges, grooves, etc., it becomes. This "aesthetic appeal" is below the threshold of consciousness......and, is exactly that which gives the observer a sensation of seeing superior quality.

Most of the time, the casual observer doesn't know just why they are getting that sensation of superior quality, or aesthetic appeal......but, they know darn well when they see it!

-----odie-----

 

[Mark Hepburn]

Here you go Odie...

Glad I could be helpful my first day back on the forum!

 

[Mark Hepburn]

You know I'm just kidding around, right?

 

[odie]

You know I'm just kidding around, right?

Yeah, I know......that's a little too high tech for me.....besides the price is out of my budget allowence.

Glad to know something like that exists, though.....

-----odie-----

 

[Bill Boehme]

Here you go Odie...

Glad I could be helpful my first day back on the forum!

Should we do a GoFundMe for Odie? He really does need the Fluke vibration analyzer.