Stand for Pull Off Test

Looking at your design, there are a few points to consider

For 120 foot-lbs you should have a clamp or have a block to hold the other side, or the whole disk edge, otherwise it will deform the disk. If there is a hole in the center of the disk, clamp it there instead. Your design creates the possibility of the disk being pulled out from under the clamp.

The sliding bolts (purple) in the clamp should go straight through, heads on the bottom. Otherwise they will be ripped out by the lever action of 120 foot lbs force.

I would move the whole spanner assembly 90 degrees to the left so that it is easier to load the disks and pull the force lever. (disk in right hand, clamp with left hand pull lever with right hand)

I rotated the "clamp". The purple screws are 1/4"-20, I was thinking of adding some swivel serrated pads on them to help hold the disc, but let me look into a different clamping system. I added a disc for reference .

So far...

Thanks for your comments.

It might be better to forget the bolts and just have a hole big enough to hold the metal part of the disk. Otherwise you are not testing pull-off, you are testing rip strength

Add a spring at the pivot point to normally push the clamp up.

How is the gauge attached to the rack?

How is the disk material attached to the gauge?

I'm thinking of adding one of these to each screw. What do you think?

As for the gauge, it will be mounted on a pad, and this pad will be welded to the rack, or maybe just screwed on.

The gauge will pull the threaded fastener (black, on top of the disk); I already have the fixture to hold it, since this test has been done manually.

The teeth are a good idea, however may be expensive.

Make sure the center of the disk is directly below the rack.

Is there a seperate test for perpendicular pull-off forces?

Serrated pads are $4.50 from McMaster.

The gauge will be directly above the center of the disc, so the force will be normal to it, do you mean like a peel off test?

Not sure, What is a peel-off test?

I am thinking of when a disk is being used, it spins. When it touches an object to sand or grind, a torque is created. This results in a perpendicular pulling force(red arrow,) tangent to the side leaving the work. The opposite side has approximately equivalent compression forces.

A perpendicular pull off test (could be the peel test) would more closely match the forces in use. A vertical pull off test, that you have set up, does test the strength of the bond. Maybe this is sufficient. Honestly, I have not read the standards - just curious.

This is how I see your design woorking.

Just to confirm all steps

1. The fixture is removed from the gauge
2. The fixture is screwed onto the disk
3. The disk must be put below the clamp and secured.
4. The rack is lowered by raising the handle
5. The fixture is attached to the gauge
6. The test is done by pulling the handle down.
7. The maximum reading is taken
8. The shaft is separated from the fixture.
9. The disk is removed from the clamp.

If this is so, You could save some steps (removing fixture from gauge) be modifying the clamp to be completely out of the way while loading.

Just an Idea

Yes, these are the steps.

The fixture is held by a cable, and this cable is hooked on to the gage, so it can be moved to the right allowing the disc to be screwed on without much trouble (turning the clamp like you suggested helps on this).

I see what you're saying about the tangential force. This was my original thought but my boss asked/told me to do it this way (I already had friction coeffients for different substrates and some maximum applied loads to stablish minimum shear force*safety factor... ). At least this test seems easier to pull off .

Here are a few other ideas

http://www.defelsko.com/adhesion-tester/adhesiontester.pdf

http://www.schleuniger-na.com/DesktopDefault.aspx/tabid-220/406_read-1564/

http://www.directindustry.com/industrial-manufacturer/test-set-75330.html

Best if the gauge has a resettable maximum reading detector.

Ok I think you are good to go. better check with the boss

Would you look at that, hydraulics/pneumatics...

Wow, I like that defelsko system. Thanks for the links.

If you simply modified the dollies to accept the shaft.... and had a larger diameter pipe to encircle the back plate.

Hydraulics.

Easier to generate highly presice forces, with less to fabricate. Most test stands i have used utilize hydraulics as the force generation method.

Force is too small to justify hydraulics, pneumatics could be better if number of tests significative and if cost is within limits, if not hand actuating is OK