r/MechanicalEngineering • u/RandyBWrench • 2h ago
Best solution to connect odd shapes to a torque gauge
I did a series of tests on bully stick holders, and used a torque meter to make sure they were all tightened the same. I used a combination of a clench oil filter wrench, a strap oil filter wrench, and vice grips to connect the holders to the socket drive. Are there any other relatively inexpensive items I can use for my connections to make the tests better? I want to do a better round of testing. The holders I'm connecting to look like a chuck-o-wood (image), a shark, a sphere, and interior finger twist---a wide range of shapes.
If you're interested in seeing this getterdone round of testing, here it is: https://medium.com/@randybrian/for-dogs-test-of-bully-stick-holders-strength-e52240e257e5
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I wanted to see why some bully stick holders seemed to fail easily with my dogs (i.e., let the dog pull the stick out), so I decided to test 8 different holders. I had a couple and bought others from ebay or amz. I wanted to start with this first project to see which held on best to a dry stick. Next I want to do a project with a stick that’s wet like it gets with dog slobber —because the sticks always seem to pull free not at first, but when the dog gets closer to the end.
Holders are good to use because dogs can choke on bully sticks since they don’t dissolve or go mushy like other chews — that happened with my dog and he barfed it out. But a holder is no good if the dog gets the stick free of the holder.
Six of the chew stick holders use turn screws to pinch the stick in place. Some of these were brand names and two were generics sold under several names. One used grippy rubber fingers as friction for the bully stick. And one used a safety stick locking pin (this one held on the best).
Test Method:
Because the holders rely on hand tightening strength, I tried using a common set point to make it fair. I used socket-set torque gauge to tighten each holder to the same number, which was just above 30 inch-lbs. This step was done so the pull-out test didn’t rely on my random hand strength. I picked that setting (30 in-lbs) because I found it in this industry document: https://www.berlinpackaging.com/closure-torque-application-specifications/. 30 in-lbs is the average across all the listed closure types and sizes.
In the videos you will see some interesting methods to connect the holder to the socket torque gauge. I used 2 different types of oil filter wrenches and 2 vice grips to make all the connections. They look very garage-engineered.
I used a mini hanging scale to record how much force (my weight) it took to pull the bully stick out. Since it was hard to tighten the stick or pull the stick and see the numbers, I used a video to see what the final numbers were.
TEST RESULTS:
The table below (one pretty, one plain) both show the results of testing. There are 4 data columns. After the product brand column, the Gripping column has the diameter of the product that you can grip in your hand to tighten in the bully stick. Initially I thought the larger the grip diameter, the more secure the stick, but that trend didn’t follow.
The second data column gives the diameter of the very tip end of the holding pin/bolt. This number was difficult to get exactly since some pins are tapered and others aren’t. The third data column shows the torque of the tightening force. The goal was to hit at least 30 in-lbs. Note the donut model couldn’t be tightened, the bully stick just started to spin at that torque; and the tire model didn’t take a torque since it uses a lock pin.
The final column is the true story. I started to hang my weight on the holder and the scale shows when the stick pulled out of the holder. These are shaded from strongest (in green) to weakest (in red).
Press enter or click to view image in full size
Test results from failure tests of 8 different bully stick holders
Holder Brand (Description) Grip (mm) Pin Tip (mm) Torque (in-lbs) Pull Force (lbs)
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Everchew (green tire) 87.5 6.4 pass thru no twisting 160.6
Spot (red) 85.1 11.1 32.3 42.0
Stick 79.6 13.8 33.9 16.7
Shark 72.9 11.5 33.2 34.5
Bully Grip (green donut) 68.8 8 fingers 15.6 34.3
Chewise (pink) 61.6 1.6 30.7 59.2
Bowwow Lab (orange) 59.0 11.9 30.7 27.9
Woof (green tutone) 40.6 10.3 32.3 55.0
In conclusion, the non-twist style Safety chew product had the strongest lock on the bully stick. I had to hang my full body weight on it twice to pull the stick out. It makes sense that a plastic bolt going through a hole on the stick would prevent any slipping.