Boomilever B/C

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chinesesushi
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Re: Boomilever B/C

Postby chinesesushi » February 18th, 2014, 8:25 pm

AALin wrote:I am attempting to build a tube boomilever for the first time. Does anyone know if people typically have an entirely hollow tube, or do they put in pieces of wood at the ends of the tube? Also, for building the part of the tube to hold the loading block, i've been looking through the blog and I don't understand how a single hole will fit the loading block. Are we allowed to unhook the hook on the loading block and thread it through the boomilever? Thanks in advance


For the first question, scroll up. iwonder says that the tension members pulling at the tube means it needs a higher density at the end. Also, you are allowed to disassemble the block as it states in the rules, but you may run into the problem of a too-short eyebolt because no minimum is given for the length of the eyebolt, discussed on pages 5(?) - 6 I think.

jasontang wrote:Hey guys so states is coming up. For my regionals boom, I used all purple CA glue and then gorilla glue in the base. Where would it be beneficial to use blue CA?

Also, what woods have people had success with in their bases? I tried using a quarter inch piece of bass in front of some balsa in the back, but that broke after ~5kg, so we stuck with a small piece of pine. Obviously, that's pretty heavy.

One more thing. How does a compression tube boom compare to the standard? One big question I had was how the loading block was mounted and the competitiveness of such a design. Also, does anyone have any pictures? I can only find one.


Blue CA is thin CA? I only use thin CA and no gorilla glue (mainly because I'm too lazy to go by any XD). I'm not sure what you mean by a heavy base. What's considered heavy for you? For me, ~0.7 g for a base to pretty heavy, but it may be different for you. One of scioly's members posted he/she reached a score of ~1300(?). Depending on the state you're in, the compression tube boom could be reasonably competitive.
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Re: Boomilever B/C

Postby iwonder » February 19th, 2014, 5:54 am

Compression booms aren't typically very beneficial since the compression member is longer than the tension members. Compression members tend to buckle (bend) when they reach their critical load, and the load is related to the length of the member, so you want to keep the compression member as short as possible. Tension members don't have this issue. So a typical boom is a tension boom where the tension members are long and the compression members are shorter (albeit be a few cm).

Also, I use a large balsa dowel for my base, it works alright, it's a bit tricky to handle, but it only weighs .2-.3 grams or so.

As for the glue, what do you mean by purple and blue? I use a slightly thicker ca, they call it 'gap-filling' or something like that, just because it doesn't run everywhere like the thin ca does when I do laminations. I'm thinking of switching over to the thin ca now though since I have a better method of applying it :D
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Re: Boomilever B/C

Postby UQOnyx » February 19th, 2014, 6:32 pm

Blue CA glue is better for balsa to balsa connections as it soaks through the wood. It is less effective for bass wood. A thing I learned: ca glue loses potency over time. It will become weaker, and will take longer to dry. Also a rule of thumb would be, if your glue joints are taking longer to bond than what it says on the bottle, you are using too much glue. Another thing is that if you have been holding the bond and its been a while and when you raise your hand from the bond and it still is unbonded, KEEP PRESSING ON IT. Adding more glue will just increase the problem. Just a few bits of wisdom.
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Re: Boomilever B/C

Postby jasontang » February 20th, 2014, 9:56 pm

Thanks for all the feedback!
chinesesushi wrote: What's considered heavy for you? For me, ~0.7 g for a base to pretty heavy, but it may be different for you.
Well, it's a small block of pine that's about 3/4 x 2 1/2 inches, so it's a lot heavier than 0.7g. My scale at home has a resolution of 1 gram and the better ones are at school, but it's break right now, so I can't get an exact mass. However, I can tell you that it is extremely heavy. But it does hold all the weight. What is your base made out of and how much does it hold?

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Re: Boomilever B/C

Postby chinesesushi » February 20th, 2014, 10:57 pm

Well, iwonder up above stated that he has a base made out of a balsa wood dowel that weighs 0.2-0.3 g, which is reasonably light. You can find those here: http://www.specializedbalsa.com/products/dowels.php . I'm not sure how much it holds, so I suggest you ask iwonder about that.
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Re: Boomilever B/C

Postby iwonder » February 21st, 2014, 5:22 am

If you're careful about the gluing it holds 15kg, but it's the most finicky part of my design. Also, I use a 5/8" dowel which is a custom size and not exactly cheap to get from specialized. You could probably get away with a 1/2" dowel and gorilla glue, or if you're good at shaping maybe turn down a 3/4" dowel to 5/8".
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Re: Boomilever B/C

Postby xchampkevin » February 22nd, 2014, 9:46 pm

:D Just finished regionals. Got third place with a score of 1226 :D
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Boomilever 3rd
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Rotor Egg Drop 4th

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Re: Boomilever B/C

Postby xchampkevin » February 23rd, 2014, 8:27 am

xchampkevin wrote::D Just finished regionals. Got third place with a score of 1226 :D


However, this boom sucked because it had a contact depth of 16.5 and it broke at the base. All my past booms broke at the base or distal end. Any suggestions? P.s. 1st place was in the 1800s and 2nd was in the 1400s.
Suzanne Middle School
Regionals
Boomilever 3rd
Helicopters 3rd
Rotor Egg Drop 4th

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UQOnyx
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Re: Boomilever B/C

Postby UQOnyx » February 23rd, 2014, 10:40 am

Were you tiered down?
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Forestry
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2013 Events:
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Shock Value
Forestry


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Re: Boomilever B/C

Postby Azn » February 23rd, 2014, 12:49 pm

UQOnyx wrote:Were you tiered down?

I think xchampkevin is B division

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Re: Boomilever B/C

Postby UQOnyx » February 23rd, 2014, 12:57 pm

Oh, my mistake, I didn't see that. Kevin, why didn't you increase the height? If you are getting a score like that, increasing the length would GREATLY lower the forces on the members, letting you shave off a considerable amount of weight from the boom, giving you a higher efficiency.
Noor-ul-Iman School

2012 Events:
Forestry
Storm The Castle


2013 Events:
Boomilever
Shock Value
Forestry


I know the voices aren't real, but they have some great ideas..

xchampkevin
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Re: Boomilever B/C

Postby xchampkevin » February 23rd, 2014, 8:50 pm

UQOnyx wrote:Oh, my mistake, I didn't see that. Kevin, why didn't you increase the height? If you are getting a score like that, increasing the length would GREATLY lower the forces on the members, letting you shave off a considerable amount of weight from the boom, giving you a higher efficiency.


I know that it gives you a higher score, but I bumped it while gluing the distal end. :(
Suzanne Middle School
Regionals
Boomilever 3rd
Helicopters 3rd
Rotor Egg Drop 4th

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Re: Boomilever B/C

Postby mwloveslm » February 23rd, 2014, 11:12 pm

@xchampkevin

what school do you go to and do you know what school got first?
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Re: Boomilever B/C

Postby xchampkevin » February 24th, 2014, 7:39 am

1st Mesa Robles, 2nd Chapparal, 3rd (us) Suzanne
Suzanne Middle School
Regionals
Boomilever 3rd
Helicopters 3rd
Rotor Egg Drop 4th

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Re: Boomilever B/C

Postby boomileverccs » February 24th, 2014, 2:01 pm

what is best thickness of wood to use? Do braces give better support horizontally or vertically, sides or top and bottom; can you do both? Distance from hole on block to end of lever between 45-50cm. best to be closest to what number? Should braces be same wood as the lever is? Are j bolts put on at event by officials? Where can you get the j bolts tried Lowes and home depot? Sorry for all the questions this is my first year doing the Boomilever.


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