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Join Date: Apr 2009
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Accelerometer Mounting Instructions

12/17/2009 4:38 AM

Hello everyone;

I will be conducting a vibration test shortly, and I need information on how to mount the accelerometers. I'll first tell my testing conditions

Sine test: 5-100Hz; 20g maximum force between 21-60Hz

Random Vibration: 5-2000Hz; trapezoid spectrum with 0,65 g^2/Hz max and 19.18 Grms total.

The test facility I'll be doing the testing uses beeswax to mount the accelerometers, but I want to use something more reliable. So far, my research has taken me to an adhesive called loctite 430. It is a general purpose adhesive for metal-metal bonding. And I believe there is a solvent to take it off, but I'm not familiar with chemicals and their applications. I also heard that I would need a "removal wrench" to twist and remove the accelerometer.

The points I ask for help are:

1. Would you recommend Loctite 430, or are there any better-suited particular type or brand of adhesive that can be found in regular hardware stores? (I have very limited time and supplies, so procurement might not be possible)

2. What can I remove the accelerometers with? Is the removal wrench a special tool, or is it a regular tool, just renamed? And again, can I find one in regular hardware stores? (see clause 1 :) )

Thank you all in advance for all your help.

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#1

Re: Accelerometer mounting

12/17/2009 5:12 AM

Hi, I have no actual experience on this but I'd venture to suggest shellac.
It will be tougher than bees wax and gentle heat/solvents should lift it. I would think epoxies would be a bit too harsh as you are not subjecting it to much G. (Although some of them soften without too much heat)
A good quality thin double sided tape?

My other sugestion would be to consult the accelerometer manufacturer (and tape manufactures).

(I know my brother uses shellac for temporary mounting of stuff like mother of pearl for turning.)
Del

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#2

Re: Accelerometer mounting

12/17/2009 8:48 AM

Many accelerometers have mounting studs or holes. Use those first. You can also use magnet mounts (though 20 g is probably pushing that). Or, the old standby is super-glue.

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#3

Re: Accelerometer mounting

12/17/2009 9:23 AM

I believe Loctite 430 is their version of cyanoacrylate glue also known as super glue. The stiffness of glue is exactly what you want for your accelerometer readings to be accurate. However, removal can become quite difficult and might mar the surface of either the sensor or what you are accelerating. Acetone I believe is the solvent for this glue and can help weaken the bond but it may still be difficult. My preference would be some mounting hardware that would provide all the stiffness needed and can be easily removed. Any chemical bond or adhesive will run the risk of either leaving adhesive residue or damaging either component.

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#4

Re: Accelerometer mounting

12/17/2009 10:44 AM

Thanks for all the comments. I would prefer physical mounting too, but unforunately neither the test fixture nor the test specimen has the appropriate accelerometer mounting holes on them. So I'll have to stick with the adhesives :)

The accelerometers the test facility will use are (as far as I know) Endevco with mounting pads, but without mounting bolts. So it's the basic slide-into-the-pad type. I think I can stick the pad on the test specimen, so that the accelerometer isn't damaged. The damage on the test specimen is another issue, though.

As far as I understand, people use any super glue to mount the accelerometers, and there are no brands exclusively for this purpose. Am I right? Also, would I damage the accelerometer if I twisted and pulled it off with a plier which has soft paddings on it?

And, how could I apply a solvent into an area that is between the accelerometer and the test specimen. With shims?

I'd appreciate any additional comments on the issue, and once again, thanks everyone.

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#7
In reply to #4

Re: Accelerometer mounting

12/18/2009 6:52 AM

Only a few comments. Have you thought on laser accelerometer? That solve your problems if you need measurements at different points of your eqquipment.

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#10
In reply to #4

Re: Accelerometer mounting

12/18/2009 1:01 PM

"So I'll have to stick with the adhesives :)" What else would you do with adhesives?

I have nothing useful to add.

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#11
In reply to #10

Re: Accelerometer mounting

12/19/2009 3:04 AM

Hahah exactly. :) It was pun intended anyway ;)

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#5

Re: Accelerometer mounting

12/17/2009 3:06 PM

I have always used super glue with acetone for removal. When these adhesive mount transducers are sold new, they also come with the wrench. It is just a plastic peice that fits over the accelerometer so you can twist it off when the acetone softens the adhesive.

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#6

Re: Accelerometer Mounting Instructions

12/18/2009 12:22 AM

G'Day in places that I have worked we would glue/weld two to three bright steel washers to the bearing housings. this allowed the VA technician to use a magnetic mount accelerometer and to be able to measure from the same place every 4 weeks. also allowed the use of magnetic mounts on non magnetic materials.

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#8

Re: Accelerometer Mounting Instructions

12/18/2009 8:22 AM

Any brand of super glue can be used. If you are short on time, you can obtain the stuff used to mount rear view mirrors onto auto windshields. It's available in any auto parts store. When the test is completed, just twist the accelerometer off with a standard wrench. If it leaves an undesirable mark, you will need to use a solvent.

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#9

Re: Accelerometer Mounting Instructions

12/18/2009 8:56 AM

Super glue will work fine, and acetone removes it handily. However, as was already mentioned your accelerometer most likely came with a handy tapped hole and little thread to attach it to your work peice. Remember to clean the surfaces of your metal thoroughly. Superglue sticks well to metal, but it also sticks well to their oxides. Since steels and aluminum produce thin oxide layers naturally which helps ward off corrosion, your super glue will stick to that layer and then flake off if you apply a minimal force. So clean, then glue. And use a small amount. You want it to be as thin as possible.

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#12

Re: Accelerometer Mounting Instructions

12/19/2009 3:14 AM

Thanks everyone! I have limited time and no chance of procurement before the test as I mentioned, so I have to work with the tools I am given. The test lab doesn't have any screw-mounted accelerometers as far as I know, they only have accelerometers with flat mounting pads. So here's the big decision (dun dun dunnn):

I've decided to use Cyanoacrylate Adhesive (actually, I bought some). I'll stick the bottom of the mounting pad, so that I don't damage the bottom of the accelerometers during removal. And I will stick kapton tape onto my surface so that it doesn't get damaged. After the test, I will apply the acetone and twist it with a pair of pliers (I will soften the tip with some felt)

Any specific suggestions on cyanoacrylate adhesives (tips on application or such)? Mine is branded "Alteco".

Thanks for all the help :)

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