PSA - Hook vs. Bolt Attachment

[Unome]

Prior to 2014, the boomilever attached to the testing wall via a bolt. This is no longer accurate. Currently, the boomilever attachs to the testing wall by hooking onto the J-hook, which is screwed into the wall.

I've seen way too many people ask this, both on here and directly to me.

[jinhusong]

I was watching a mock C competition at local high school and saw a group attached their boomilever to the tip of the hook, not to the half moon bay of the hook.

This setup has some advantage. The vertical distance will be about 10mm higher than the middle of hook.

I checked the rules immediately but cannot tell it broke the rule or it is just clever. Any thoughts?

Jinhu

[cheese]

Potentially less stable, harder to get accurate, you will have to be very precise to do this. I wouldn't recommend it because the amount of time/effort/skill it takes to get it perfect won't pay off IMO to get the extra 1cm of vertical distance.

[Sciencer101]

I was watching a mock C competition at local high school and saw a group attached their boomilever to the tip of the hook, not to the half moon bay of the hook.

This setup has some advantage. The vertical distance will be about 10mm higher than the middle of the hook.

I checked the rules immediately but cannot tell it broke the rule or it is just clever. Any thoughts?

Jinhu

If you were at a trashy competition, even the littlest bit of variation would kill you. You would have to bend your tension members, making them that much more stressed.
A good idea, but not worth it.

- Sciencer

[dholdgreve]

I was watching a mock C competition at local high school and saw a group attached their boomilever to the tip of the hook, not to the half moon bay of the hook.

This setup has some advantage. The vertical distance will be about 10mm higher than the middle of hook.

I checked the rules immediately but cannot tell it broke the rule or it is just clever. Any thoughts?

Jinhu

Just kicking the already dead horse here, but it all boils down to this:
Having the tension end of the boom bear against the end of the hook raises the angle of the tension chord ever so slightly, thus lowering the mechanical "disadvantage." established by the projection exceeding the height. If you are in division B, this may reduce the force applied through the compression beams from 30 KG to something in the range of 29.98 KG. The disadvantage is that you have reduced the area of bearing from .2453 square inches (if you were to use to 5/8" dowel, for example) to .049 square inches by bearing on the tip of the hook, a reduction of 80%. ... 1/5th the original bearing area... this concentrates the load placed on the bearing area by a factor or 5. So under full load of 15 KG, (~33 pounds), and just to prove the point, you would effectively be changing the bearing pressure at the connection to the hook from 19,372 pounds per square foot to 96,979 pounds per square foot. Those are both some pretty massive loads!

This has always been one on the most problematic challenges in this event with nearly 40% of all boom failure occurring here, so unless you plan on using oak, ebony, ash, hickory, or some other really dense wood as your mounting block to offset the added crushing, I think I'd reconsider.