Boomilever B/C

[iwonder]

We did remove the eye bolt from the Block, sometimes tough at the fist competition for 7th and 8th graders. My point was that if the chain is permanently attached as part of the testing apparatus, it should be defined so that teams can design for it, do you disagree? Thanks

But it is defined as permanent (well, basically), the rules say that it uses an eye bolt, so we know that it can be permanently attached, and should probably design for the worst case of it being attached. At least to me, this means that I assume it's permanent at all times. That way if it's removable you've had a lucky day and it's easier for you, but if it isn't then you aren't any worse off. From a coaches perspective this is a pretty good learning experience for kids, just plan for next time!

[jander14indoor]

to jander14indoor

Any chance they will define the the hook for hanging the bucket this year as part of the testing apparatus. We ran into an issue last year, where we went to one invitational, and they had an Eye Bolt, where the chain was permanently attached and we had not designed for this. We had designed the compression members to be just slightly wider then a 1/4" J Hook, and with the chain attached it would not fit though the frame. Nowhere did any of the rules define the size of the chain attached, so there was no way to design for it. This was not an issue at another invitational where they used a J Hook and separate chain. Has this been discussed at all, define this part of the testing apparatus. Thanks

First, don't assume I have any special knowledge of this event. I'm not the National ES, and did not write these rules. In this context I'm just an experienced mentor for the building events.

That said, take the following with an appropriate grain of salt, READ THE RULES FOR YOURSELF!! I cannot emphasize this enough. Success requires a deep understanding of the rules in SO.

Finally had a chance to re-read the rules, there seems to be no requirement for the base to touch the wall. You specifically CANNOT adjust the J-hooks. There is a spec on how big the opening has to be, but no criteria on how vertical the hook has to be. Word to the wise, this is probably important to your design, you should be able to tolerate some deviation of the hook from vertical!!!!

On your specific question, the hook for hanging the bucket seems LESS defined than previously. You have a 1/4 inch eye bolt with length up to 4 inches (no minimum!). You are allowed to dissasemble the loading block to mount it on your boom. NO definition of the chain. A hook is mentioned, but not described whether it is to hook over the eye, or over the bucket handle! Since the eye bolt has no minimum lenght I'd be careful to leave as much room below the loading block as you can. DON'T assume a 4 inch eye bolt! In other words, I'd be coaching teams to leave as much room under the loading block as possible.

Jeff Anderson
Livonia, MI

[yoliu]

Regarding the 1/4" eyebolt for loading block:
In 2013 rules, there is no specification about the length of eyebolt or the size of the eye-hook portion (of the eyebolt).
We have seen eyebolts' threaded bolt portion ranging from 2" to 6" (with majority being 4"~6"). Most eyebolts need to attach chains separately, and most eye-hook is about 1" in diameter.

For 2014, it adds that NO LONGER than 4" in length. It does not clarify whether 4" is for the threaded bolt portion or the entire thing including the eye-hook, and it does not indicate the max size of the eye-hook portion.

The bolt portion really needs to be 1.25" to go through the 2cm load block, plus washer, wingnut, and some margin (so the bolt does not thread off when the bucket spins).
Assuming the commonly available 1" eye-hook portion, we are really looking at a 2.5" minimum for the entire eyebolt including eye-hook portion.

However, with such a short eyebolt, the compression tube design that Balsaman and others discussed in 2013 would not work - as there is no bolt portion left to go through the diameter of the tube.
The compression truss design that are very popular would fit - as long as the eyehook is 1" and you leave an opening of at least 1". But obviously with the eye-hook inside the distal end, it may be hard for middle school students to attach the chain and not damage the boom distal end. For high school students with big hands, it might be difficulty too:) For 2013, most eyebolts are long enough such that the eye-hook is below most boom's distal end.

However, one can obviously take it to the extreme and have a huge 2.75" diameter eye-hook plus the 1.25" bolt portion to meet the 4" rule. In this case, the compression truss would not work either as the widest possible opening is 2" (5cm).

So do we interpret the rules to the extreme? Or follow the commonly available approach and assume the eye-hook is the common 1" diameter and the threaded bolt portion is at least 2.5" such that all the compression designs (including tube) are possible? -- hopefully the rule really meant to say no shorter than 4" : )

I would like to assume the common approach, however, since this 4" is a change from 2013, what would be the reason?

What does everyone think and what's your interpretation?

P.S.: sorry for the long post: )

[johnguackmbl]

Where can one get basswood longer than 24 inches?

[balsa]

Where can one get basswood longer than 24 inches?

online

[iwonder]

Regarding the post about the eye bolt, I'd say continue at your own risk in October clarifications will open up and you'll be able get a real answer(hopefully) to your question. But don't let that stop you from working on a design, just keep in mind you might have to tweak it later on.

[chalker]

Regarding the post about the eye bolt, I'd say continue at your own risk in October clarifications will open up and you'll be able get a real answer(hopefully) to your question. But don't let that stop you from working on a design, just keep in mind you might have to tweak it later on.

Speaking unofficially of course, I don't think we'll provide a rules clarification that specifies the eye bolt in more detail. Thus you are going to need to be prepared for any of the possible contingencies discussed here so far. of course you could always contact individual event supervisors before a tournament and try to convince them to provide a certain style eye bolt......

[UQOnyx]

Where can one get basswood longer than 24 inches?

For those who did seem interested in no base at all, with the bass being a continuous loop around the J-hook, it will probably not work. I tried doing something like that as a test, and the problem is, that when bending bass, (I used boiling water to soften it), no matter how slowly or evenly you bend it around the hook, a part of it always splits, or a very sharp angle appears on the inside of the curve. I don't think I am explaining it well enough, but try it out for yourself and you can see what I mean. Of course, with a lot of patience, it would work, but I don't think it would be worth the effort.

[iwonder]

It's due to the fact that the inside of the curve is shorter than the outside(if I'm understanding you correctly) so the outside of the bass tends to break and the inside tends to crush together and spread out? It's a typical problem when bending wood, steam helps, but only so much. This is also the reason why bent tubes are so hard to make well, when you force wood into a shape it wasn't originally in, there's internal stress/strain in the material that weakens it.

[ckssv07]

Are you allowed to put the nut and washer after the attachment base like last year or must the nut and washer stay adjacent to the wall?