I'm actually not sure it's made of Delrin, but I've noticed that for the white colored plastic blocks that are for support of things like the flap weldment supports, if I actually torque the bolts to a normal spec it tends to deform/squish the blocks. The black blocks seem a lot harder. Should I just be snugging down these bolts just until I can see the plastic start to squish and then stop?
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Torque Delrin Block Bolts?
- Thread starter skelrad
- Start date
RV8JD
Well Known Member
This thread might help: https://vansairforce.net/community/showthread.php?t=204097
wcalvert
Well Known Member
The concept of torque and the use of torque tables seems to be frequently misunderstood. Any torque value obtained from a table is based on some assumptions, and those assumptions may not be well defined on the table itself.
Considering that the torque on a bolt is a way of defining the force the bolt exerts between the head and the nut, it's clear that considering the material being bolted is of utmost importance.
"Torque is a twisting force measuring force multiplied by distance. It is the application of force acting at a radial distance to create tension in threaded fasteners. When the nut and bolt are tightened, the thread converts the applied torque into tension, which is converted into a clamping force." from americanbelleville.com
If your fastener is made of a material with a known tensile strength, and the material you a clamping is of a know compressive strength, the torque specified will stretch the bolt slightly, like a spring, and not plastically deform the material you a clamping or the bolt itself. All simple when you are using a standard AN bolt through 2024/6061 aluminum, the numbers come right off the chart.
Now that you've combined the torque specification for a bolt used in aluminum with a material being clamped is NOT aluminum, you're on your own. The compressive strength of UHMW is approximately 3k psi, while for 2024 aluminum it's around 47,000 psi. You get the idea.
Using a torque value from your handy chart will deform the UHMW significantly. A new value must be determined to achieve your goal for the blocks.
So the question might be "what is the goal of this fastener in the UHMW?" Honestly the design of the free standing block is not the best, using the UHMW itself to support the rod without any structure to assist the effort isn't really how this material is meant to be used. But, the loads are low and the UHMW is strong enough to get the job done in this application.
I contend that the bolt should hold the block in place without causing any deformation of the block itself. Using an oversize washer under the head of the bolt may help, and on my craft, due to the low torque value, they are safety wired to prevent any movement.
Cheers
Considering that the torque on a bolt is a way of defining the force the bolt exerts between the head and the nut, it's clear that considering the material being bolted is of utmost importance.
"Torque is a twisting force measuring force multiplied by distance. It is the application of force acting at a radial distance to create tension in threaded fasteners. When the nut and bolt are tightened, the thread converts the applied torque into tension, which is converted into a clamping force." from americanbelleville.com
If your fastener is made of a material with a known tensile strength, and the material you a clamping is of a know compressive strength, the torque specified will stretch the bolt slightly, like a spring, and not plastically deform the material you a clamping or the bolt itself. All simple when you are using a standard AN bolt through 2024/6061 aluminum, the numbers come right off the chart.
Now that you've combined the torque specification for a bolt used in aluminum with a material being clamped is NOT aluminum, you're on your own. The compressive strength of UHMW is approximately 3k psi, while for 2024 aluminum it's around 47,000 psi. You get the idea.
Using a torque value from your handy chart will deform the UHMW significantly. A new value must be determined to achieve your goal for the blocks.
So the question might be "what is the goal of this fastener in the UHMW?" Honestly the design of the free standing block is not the best, using the UHMW itself to support the rod without any structure to assist the effort isn't really how this material is meant to be used. But, the loads are low and the UHMW is strong enough to get the job done in this application.
I contend that the bolt should hold the block in place without causing any deformation of the block itself. Using an oversize washer under the head of the bolt may help, and on my craft, due to the low torque value, they are safety wired to prevent any movement.
Cheers
