Handhold for Rock Climbing
by SketchySam, published
Description
Recent Comments
view all
Tried the hold? I'm sure ABS is fine, and even PLA might work. Just build it with the right orientation, in order to have layers in compression and not in tension!
Please update if it worked...
A related note on the strength of ABS plastic. My quick tests in the BotCave show that ABS plastic has an ultimate tensile strength (UTS) of around 6 ksi. This means that a strand with a 1 in^2 cross-sectional area should be able to hold 6000 lbs. By comparison, here are the material properties for some common engineering materials:
6061-T6 aluminum: 42 ksi
This aerospace grade aluminum is commonly used in bike frames and rock climbing equipment.
A36 Steel: 58-80 ksi
This plain vanilla structural steel is commonly used in buildings (e.g. I-Beam girders).
Red Oak: 8 ksi
Used for furniture. Wood is also a common material for
climbing handholds.
(Source: http://en.wikipedia.org/wiki/U...
So the point is: ABS is just about as strong as wood, which is also used for handholds. In theory it should work. But - neufeld's comment about the potential for shear failure bears some further investigation.
@neufled - That's an interesting point you bring up about the primary failure mode of the ABS plastic being in shear. I hadn't thought of that. If I have the time, I'd like to try your suggestion of printing the hold rotated 90 deg and see if that cures some of the flex.
Also, I agree that the bigger the washer the better. I used no washer in the previous text and the hold flexed considerably.
On the multiple screw issue - this is possible. There are basically two types of handholds: bolt-on and screw-on. The first type, bolt-on, accepts a single 3/8" socket head
cap screw bolt in the center of the hold. This bolt is screwed into the climbing wall, which has T-nuts pre-installed. The second type of hold, screw-on, accepts multiple drywall screws. These drywall screws are screwed directly into the plywood of the climbing wall. So - if we find that the hold f
lexes too much we can simply shore it up with more attachment points.
Tags
License
Give a Shout Out
Instructions
*** WARNING *** Rock Climbing and Indoor Wall Climbing are inherently dangerous - you could get seriously hurt or die. Don't climb without first getting proper instruction from an expert. Don't try to use this design unless you're willing to assume all the risks associated with its use.
Comments
You must be logged in to post a comment.
A related note on the strength of ABS plastic. My quick tests in the BotCave show that ABS plastic has an ultimate tensile strength (UTS) of around 6 ksi. This means that a strand with a 1 in^2 cross-sectional area should be able to hold 6000 lbs. By comparison, here are the material properties for some common engineering materials:
6061-T6 aluminum: 42 ksi
This aerospace grade aluminum is commonly used in bike frames and rock climbing equipment.
A36 Steel: 58-80 ksi
This plain vanilla structural steel is commonly used in buildings (e.g. I-Beam girders).
Red Oak: 8 ksi
Used for furniture. Wood is also a common material for
climbing handholds.
(Source: http://en.wikipedia.org/wiki/U...
So the point is: ABS is just about as strong as wood, which is also used for handholds. In theory it should work. But - neufeld's comment about the potential for shear failure bears some further investigation.
Ok the results are in... I bolted the handhold to a climbing wall and tested it out. Here's what I observed:
- The bolt hole is too small to fit a standard 3/8" socket head cap screw. I used a smaller lag screw to attach it to the wall for the test. I need to make the hole bigger.
- The hold withstood my bodyweight, but it creaked and flexed. I was concerned that it might break unexpectedly. I think setting the infill ratio in Skeinforge to a higher value would strengthen the hold.
Thanks to all of your comments and suggestions. This being my first post to Thingiverse, I am very impressed at the feedback and supportiveness of the community. You guys rock!
Now onto the next iteration...
Oooh yes, I think that if you print hammer out of ABS it will work :-)
Uhh, is ABS really durable enough for this application?
A related question would be how ABS fails. If a hold wears and deforms over time, you have some indication of when to replace it. If it will suddenly fracture with no warning, that might be worse.
I'm concerned about the layers delaminating and shearing -- the layer bond is much weaker than the extruded filament. (Demonstration: Put a printed part on a bench with a layered edge facing up, put a chisel tip in the groove between layers, and rap it with a hammer. It'll pop right apart because the layer bond is the weakest part.)
Right now I'm only worried about the tip of the grip shearing off. I think it'd be slightly stronger if printed rotated 90 degrees about the Y axis, so that the shear planes run front-to-back / top-to-bottom and the part never has shear planes intersecting the segment between the bolt and the app
lied force.
Even so, I'd use as large a washer as possible (fender washer) around the bolt head, and I'd be inclined to use two bolts side by side (but I bet that doesn't work with premanufactured climbing walls).
My $.02.
If anyone wants to run off a copy for me, I'd be happy to put it through the proper tests.
(about me: Rock Climbing Instructor, manage 2 climbing walls, consult for a few others, etc...)
With a heavy honeycomb inside structure, I bet it could be-- I'd recommend testing it with several times your own weight before trying it as a rockclimbing surface though!
Tried the hold? I'm sure ABS is fine, and even PLA might work. Just build it with the right orientation, in order to have layers in compression and not in tension!
Please update if it worked...