Boomilever B/C

[dholdgreve]

I'm not familiar with laser cutters (at all!). but in years past both sides of a boom could remain parallel (or nearly so) without impacting overall weight significantly. Not so this year. To do so would require building a boom that is wider than 8 cm the entire distance. I think most teams will taper their designs inward in both the X and Y axis as it moves out and up from the wall. If so, this design would normally rotate the compression beams inwardly so that the loading block only bears on the very outer edge of the beams, since they are all 90 degree corners.

Can a laser cutter cut the compression beams into more of a parallelogram shape instead of the squares or rectangles available from supply houses? If so, the upper outer and inner under corners would be obtuse angles and the inner upper, and outer lower angles would be their reciprocal acute angles. This way, the loading block would be able to bear continuously across the beams and not cause the beams to want to rotate outwardly.

I think it would be fairly easy to determine the angle of "vertical lean" on each side, but because each side also angles in horizontally, this would affect the calculated vertical angle. It would probably end up being a trial and error process to find the correct angle, but would definitely give the team that figures it out an advantage.

If you do decide to go this route, please do keep us informed as to your results!

[JonB]

Yeah I meant wasted wood lol. I like to test all of my pieces with SPFD before building, is there a method you use to sort your wood pieces after they are laser cut?

So, choosing wood is... tedious. To be honest, the process of wood selection does change for us depending on the competition. For prototyping a design (to see how easily it can be built or if their are structural oversights in a design), we do not really care which wood we use. But, when we are being "picky", here would be the general process.

1. Grain selection based on part of the boomi.
2. "General" weight of the balsa sheet (it is easy to tell very dense from low density)

At this point, we would have selected the balsa sheets we might want to use and then those that we would never use.

3. With the sheets we might use, we then do a "light" inspection. You can see a picture of this process here: https://drive.google.com/file/d/1ojP6xC ... sp=sharing . You can see the wood on the desk that has already been inspected. We are looking at inconsistencies within the wood that are much more apparent with the bright light behind it. Sections of the balsa sheet are marked as usable and unusable.
4. The wood is cut (either by hand or laser, depending on part of the boomi)
5. We weigh the cut balsa to make sure it is as close as possible to each other (if looking for two identical pieces). We find that with the "light" inspection already completed and parts of a sheet already disallowed for usage, the densities of balsa cut from the same sheet are often times similar (not always... but often).

We do see that balsa from common craft stores can be more inconsistent than wood that is special ordered (but is wayyy more expensive).

I'm not familiar with laser cutters (at all!). but in years past both sides of a boom could remain parallel (or nearly so) without impacting overall weight significantly. Not so this year. To do so would require building a boom that is wider than 8 cm the entire distance. I think most teams will taper their designs inward in both the X and Y axis as it moves out and up from the wall. If so, this design would normally rotate the compression beams inwardly so that the loading block only bears on the very outer edge of the beams, since they are all 90 degree corners.

Can a laser cutter cut the compression beams into more of a parallelogram shape instead of the squares or rectangles available from supply houses? If so, the upper outer and inner under corners would be obtuse angles and the inner upper, and outer lower angles would be their reciprocal acute angles. This way, the loading block would be able to bear continuously across the beams and not cause the beams to want to rotate outwardly.

I think it would be fairly easy to determine the angle of "vertical lean" on each side, but because each side also angles in horizontally, this would affect the calculated vertical angle. It would probably end up being a trial and error process to find the correct angle, but would definitely give the team that figures it out an advantage.

If you do decide to go this route, please do keep us informed as to your results!

I agree, I believe that many great designs this year will be tapered. There will be some rotation of the main compression pieces which would seemingly cause the cross pieces between the main compression pieces ("x" or ladders, etc) to break causing failure of the structure. However, based on results and high-speed footage, we are not really seeing that as an issue with our current design (which will inevitably change).

A laser cutter could cut a compression beam in a parallelogram, but it would take some creative placement of the wood by the operator/builder. The laser will fire straight down, perpendicular to the surface of the cutting bed, but the object that is being cut can be placed in any orientation. If the wood was placed on the cutting bed in the correct way (one side of the wood slightly raised) then it would create a parallelogram. It would definitely be challenging to duplicate identically every time, but possible.

Figuring out an ideal angle is definitely an interesting thought and would be a good challenge.

Since I mentioned it earlier- I recently posted some of the high-speed footage we have from our testing of towers over the last few years. When boomi cycles out, I will upload new video of our testing throughout the two years. I think this video will be appreciated by those who understood just how difficult towers was as an event and for boomi builders this year. The video is somewhat sad to watch for builders because the destruction is way more... obvious. Filming towers was a pain (aspect ratios and resolution...) but we typically filmed from 1,000-3,000 fps. Because boomi is a different shape (allowing for a better/easier aspect ratio) we have been able to film as high as 6,000 fps (we also changed our lighting system which helped).

Enjoy the slow-motion destruction of towers here: https://www.youtube.com/watch?v=ctwxwPyr4P8

At the end of the competitive season, look for all of our high-speed boomi breaks to be uploaded to our channel as well. We have really old footage of boomi from 2013-2014 uploaded to our channel for those interested.

I do want to also state that to compete in this, or any, event, you do not need to have a laser cutter or a way to film in high-speed. We enjoy using these tools but the number one most important factor is simply building. Build A LOT, over and over again- no technology required.

[dholdgreve]

^^^^^ THAT was absolutely one of the COOLEST Videos I've ever seen! Thanks for sharing! Can't wait to se the Booms!

[JonB]

^^^^^ THAT was absolutely one of the COOLEST Videos I've ever seen! Thanks for sharing! Can't wait to se the Booms!

No problem! The boomi videos that will be posted from this year are pretty great to watch and fun to create. We bumped up our lighting to about 10x what it was previously. We were able to capture two boomi breaks at 6,500 fps today and yesterday. The resolution is not very high at this frame rate but you can easily see the moment and location of the first piece that fails.

[dankdecidueye]

For my base, I’m using basswood. To clarify, the grains should be vertical on the hook, right? Or should it be horizontal?

[dholdgreve]

For my base, I’m using basswood. To clarify, the grains should be vertical on the hook, right? Or should it be horizontal?

I suppose it depends on your mounting block design, but in our case the grain of the mounting block runs horizontal, perpendicular to the hook, with slots of both sides of the hook.

[JZhang1]

Where do y'all buy basswood for tension members?

[dholdgreve]

Where do y'all buy basswood for tension members?

Specialized Balsa and National Balsa both sell bass as well

[scioly2345]

Where do y'all buy basswood for tension members?

Specialized Balsa and Natuonal Balsa both sell bass as well

They have good 24 inch 1/8 by 1/16 basswood on amazon

[Tendan]

Where do y'all buy basswood for tension members?

Specialized Balsa and Natuonal Balsa both sell bass as well

They have good 24 inch 1/8 by 1/16 basswood on amazon

You can also go to a hobby store and handpick wood, you'll just look a bit weird with a scale and flashlight analyzing the wood in the back of the store.