Boomilever B/C

[DoctaDave]

With my experience, I have found that Gorilla glue isn't much better than regular old CA glue. Even for parts like the distal end and attachment block, and I have been able to hold the entire load without using gorilla glue. I have also found that my boomilevers that are built with just CA glue vs. my boomilevers built with gorilla glue do not have any significant weight difference at all. I actually prefer not to use gorilla glue for several reasons:

1. Its a pain to work with; its sticky, hard to clean, and it expands A LOT when it dries, so if you aren't careful, you will make a mess.
2. You have to clamp it. By clamping parts of your boomilever, you will risk damaging it.
3. As far as I know, there isn't any sort of Gorilla Glue remover... so there isn't any way of fixing errors if you use it
4. It takes a long time to cure, and if you're like me and you always build the day before the competition, then it might not be at its full strength when it becomes the time to test

Don't get me wrong, gorilla glue is extremely strong, but it does have its cons.

[nxtscholar]

Out of curiousity, what do you guys do with the boomilevers after you test to failure? Do you guys reuse and salvage any of the pieces, or just throw it out?

I actually just rebuild and fix some of my booms and manage to still obtain decent scores, but I was wondering what the general consensus was on what to do with the wood you're left with after a boom breaks, and how you know a piece of wood is exactly reusable.

[iwonder]

While loading I always listen for cracks and watch for bending pieces, is any of that happens I throw it out right there. Otherwise, if something simple breaks, like a base connection, I'll typically rebuild but only for testing reasons, not for contest (because most of the time I'm trying to push the compression member). If anything on the compression member breaks (beside bracings) I'll scrap it.

[Can_Of_Tuna]

I've never tested a boomilever to failure, but I'd probably keep it for future reference on how it broke, and improvement of future designes, but also just as a souvenir XD

[A Person]

I've never tested a boomilever to failure, but I'd probably keep it for future reference on how it broke, and improvement of future designes, but also just as a souvenir XD

That's interesting. How many have you tested? I'm usually the exact opposite, I keep the ones that survive.

[boomileverccs]

This is our first year competing in the Boomilever B/C build. We were just curious if grading scores are better for more creative builds or being successful adhering to just bare minimum requirements. Or is grading scoring is just on whether your build succeeds the required task and has minimum damage to levers and such?

Team CCS

[Can_Of_Tuna]

I've never tested a boomilever to failure, but I'd probably keep it for future reference on how it broke, and improvement of future designes, but also just as a souvenir XD

That's interesting. How many have you tested? I'm usually the exact opposite, I keep the ones that survive.

The truth is, that I haven't tested that many. And it's not as if I would throw away the ones that survive. I meant that I would keep all of them, and didn't specify about the ones that did hold 15 kg,since it was a given that the working booms would be kept.
I plan on building 5 more,and testing at least 4 before state

[Can_Of_Tuna]

This is our first year competing in the Boomilever B/C build. We were just curious if grading scores are better for more creative builds or being successful adhering to just bare minimum requirements. Or is grading scoring is just on whether your build succeeds the required task and has minimum damage to levers and such?

Team CCS

Sadly, there are no no bonus points for creativity. Otherwise my team wouldn't have gotten last when our boom's elliptical side supports popped off.(All the other teams' booms were various variations of the standard). The scoring is the weight of your boomilever divided by the weight held, and if ANY part of the boomilever fails, you will have to stop loading sand.

[JMDugan]

I have read many of the posts, but I apologize, I do not have time to read through hundreds of pages.
I am a non-engineer coach trying to help my kids improve their boomilevers. We have a nasic box compression made of 1/8 balsa, 1/8 bass tension. 3/32 bracing and trusses. The last few booms have failed in compression.

I have novice builders and I know the design is pretty basic, but the best efficiency we've gotten so far has only been 400. Our booms are heavy -- about 13 grams. They are very well cross braced - . The last one broke on the bottom compression member. The one before that broke at the wall. Dating back to last year, we have had three or four break at the wall.

What should I be looking for as the likely culprit for early failure? Non-symmetry? Bracing?

Any basic help appreciated.

[iwonder]

This is our first year competing in the Boomilever B/C build. We were just curious if grading scores are better for more creative builds or being successful adhering to just bare minimum requirements. Or is grading scoring is just on whether your build succeeds the required task and has minimum damage to levers and such?

Team CCS

Sadly, there are no no bonus points for creativity. Otherwise my team wouldn't have gotten last when our boom's elliptical side supports popped off.(All the other teams' booms were various variations of the standard). The scoring is the weight of your boomilever divided by the weight held, and if ANY part of the boomilever fails, you will have to stop loading sand.

The score is the load held in grams divided by the mass of the boom in grams

Also, rule 5.j state that loading must stop when the boomilever fails, which is defined as the inability to carry additional load, or the load being supported by anything other than the boomilever. So just because your bracing fails, you can keep loading as long as the boomilever is still supporting it.

I have novice builders and I know the design is pretty basic, but the best efficiency we've gotten so far has only been 400. Our booms are heavy -- about 13 grams. They are very well cross braced - . The last one broke on the bottom compression member. The one before that broke at the wall. Dating back to last year, we have had three or four break at the wall.

What should I be looking for as the likely culprit for early failure? Non-symmetry? Bracing?

Basic designs are honestly just fine until you try to push 1000, and it makes for a good learning experience. It's hard to tell what the issues are from your description, but it basically sounds like you should try a larger main compression member (which may not be necessary, but it would get you going in the right direction). Another thing is to look at how you're building it, everything should fit very snug, be square and feel solid. I'm also not sure what you mean by very well cross braced, depending on your design a spacing of 5cm is a good starting point to tweak from once you have a good design. Also, if you can, weigh the all the main compression members and try to match them in weight (within reason, .1g or so should be fine), since balsa's density varies widely so does it's strength and having one member slightly weaker could cause uneven loading.