Boomilever B/C

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TheChiScientist
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Re: Boomilever B/C

Postby TheChiScientist » December 25th, 2018, 6:08 pm

MadCow2357 wrote:
TheMadScientist wrote:You mean that it is ok to leave the last 5 cm of the boom without bracing at all? I was thinking it would drive down the score since booms would snap at the 5 cm point away from the distal end... or is that why the tension members are so important??

From my experience, yes, it is okay to leave the last 5 cm without bracing. Normal x bracing, that is. I had a breakage in the last 5 cm on my third boomilever, and I ended up adding two ladder pieces to help take some load. I also rotated my main compression members (rectangular) so that they were longer vertically. Haven't that kind of breakage since, so I suppose what I did helps. If you want @TheMadScientist PM and I can send you a picture or two of what I changed.

Well someone took my username...(Kinda. Welcome to the forums :) ) From my experience you should focus more on the distal ends if you want results so I wouldn't panic over the bracings yet...
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Re: Boomilever B/C

Postby DarthBuilder » December 25th, 2018, 7:34 pm

TheChiScientist wrote:
MadCow2357 wrote:
TheMadScientist wrote:You mean that it is ok to leave the last 5 cm of the boom without bracing at all? I was thinking it would drive down the score since booms would snap at the 5 cm point away from the distal end... or is that why the tension members are so important??

From my experience, yes, it is okay to leave the last 5 cm without bracing. Normal x bracing, that is. I had a breakage in the last 5 cm on my third boomilever, and I ended up adding two ladder pieces to help take some load. I also rotated my main compression members (rectangular) so that they were longer vertically. Haven't that kind of breakage since, so I suppose what I did helps. If you want @TheMadScientist PM and I can send you a picture or two of what I changed.

Well someone took my username...(Kinda. Welcome to the forums :) ) From my experience you should focus more on the distal ends if you want results so I wouldn't panic over the bracings yet...


I would think you shouldn’t just leave out the bracings but there should definitely be a balance. But the bracings should be strong enough to allow some warp I guess. If it’s too thin/weak it would snap.
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Re: Boomilever B/C

Postby musicalwhang » January 3rd, 2019, 1:09 pm

I am unsure of the specs of the J-bolt listed on the rules. https://www.amazon.com/National-Hardwar ... B000BO54X8
Can anyone who has this confirm that the length from the wall to the inner part of the "J" is about 4.5 cm? (2.5 cm opening plus an inch of just the "J"?)

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Re: Boomilever B/C

Postby Carrot » January 3rd, 2019, 1:17 pm

musicalwhang wrote:I am unsure of the specs of the J-bolt listed on the rules. https://www.amazon.com/National-Hardwar ... B000BO54X8
Can anyone who has this confirm that the length from the wall to the inner part of the "J" is about 4.5 cm? (2.5 cm opening plus an inch of just the "J"?)


Yeah, it's like like 4.5cm +/- .1

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Re: Boomilever B/C

Postby musicalwhang » January 3rd, 2019, 1:56 pm

Would a 1/4" diameter wooden dowel at 3cm suffice butt-jointed between 2 bass tension members at 1/8x1/16?

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Re: Boomilever B/C

Postby MadCow2357 » January 3rd, 2019, 5:38 pm

musicalwhang wrote:Would a 1/4" diameter wooden dowel at 3cm suffice butt-jointed between 2 bass tension members at 1/8x1/16?

Would it suffice? Likely not, but depends on your goals and what your design is. Try increasing the surface area on the tension member...
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Re: Boomilever B/C

Postby retired1 » January 3rd, 2019, 5:59 pm

A better way would be to very carefully cut grooves in the end of the dowel that will just fit the tension members . I used Devthane 5, but a good epoxy will work well.
The real trick of this is to get the two end cuts to be perfectly parallel. If it is not, re cut a new piece. The joint will withstand a great amount of abuse and still not fail.

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Re: Boomilever B/C

Postby musicalwhang » January 3rd, 2019, 6:36 pm

Thank you for the responses. Another question: I was wondering what the trusses that connect the tension members and compression members do for the boom. Some designs have it but some don't.

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Re: Boomilever B/C

Postby MadCow2357 » January 3rd, 2019, 7:46 pm

musicalwhang wrote:Thank you for the responses. Another question: I was wondering what the trusses that connect the tension members and compression members do for the boom. Some designs have it but some don't.

They have two purposes:
1. Preventing the boom from "splitting open".
2. Prevent buckling along the compression member
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Re: Boomilever B/C

Postby waffletree » January 3rd, 2019, 7:49 pm

MadCow2357 wrote:
musicalwhang wrote:Thank you for the responses. Another question: I was wondering what the trusses that connect the tension members and compression members do for the boom. Some designs have it but some don't.

They have two purposes:
1. Preventing the boom from "splitting open".
2. Prevent buckling along the compression member

yea ^^that
and prevent the whole boomi from collapsing because it's too much pressure downwards for the chords to handle
also to make the boomi firm and prevent it from wobbling side to side
just adds support overall like you dont see real life cranes with no trusses at all
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Re: Boomilever B/C

Postby musicalwhang » January 3rd, 2019, 9:04 pm

I'm having trouble visualizing how the dowel attaches to the tension members. People on this forum have recommended putting in a small grove on the dowel in order to make the tension member attach to the dowel on all 4 sides. Can someone explain how this can be done and why this is best option? are there also different options on how the j-hook should latch onto the boomi?

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Re: Boomilever B/C

Postby retired1 » January 4th, 2019, 3:12 am

You should have 2 tension members attaching to the dowel, not 4. The reason that the notched en is best is that you have more glue surface, thus a stronger joint.
The dowel option is probably the best because of the less wood (weight) and the ease of attaching it to the hook.

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Re: Boomilever B/C

Postby jinhusong » January 4th, 2019, 2:02 pm

Put tension member into the grove, then laminate it with a sheet. This way, 4 sides of the tension member are glued to the base.

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Re: Boomilever B/C

Postby Cow481 » January 4th, 2019, 2:58 pm

Wouldn’t it be easier and more effective to just drill a hole and gorilla glue the tension pieces to the dowel rod?
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Re: Boomilever B/C

Postby Vstorm34 » January 4th, 2019, 5:01 pm

Cow481 wrote:Wouldn’t it be easier and more effective to just drill a hole and gorilla glue the tension pieces to the dowel rod?


If the tension is a square piece of wood and not round then using a drilled hole will reduce the surface area of the joint. A notch will a allow for more coverage since the flat edges will have more contact with the wood.


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