How to mount boomilever onto the J-hook

just007in
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How to mount boomilever onto the J-hook

Post by just007in » September 12th, 2018, 3:20 pm

I was wondering how exactly you are supposed to attach the boomilever to the j-hook?

Do you drill a hole into a piece of wood and "loop" the boomilever through the hook? Is there even enough space between the hook and the wall to accomplish this? (the 40-45 cm long part of the boomilever or the tension beams would get in the way)

Or do you hang the boomilever onto the "unbent" part of the j-hook like hanging a coat hanger onto a rack? If so, would you bend the wood physically or cut out a half-circle divet into the wood to fit onto the hook?

Also, what part of the j-hook should the base of the boomilever rest on?
Should it rest on the "unbent" part of the j-hook or the curved portion of the j-hook?
If it is the "unbent" part, would the threads on the j-hook affect mounting or boomilever base designs in any way?

How much space should the base take up on the hook? Should it take up the entire available space on the "unbent" part of the j-hook (so it can't slide around) or it does not have to take up the entire available space (saving some weight)? (assuming you mount the base of the boomilever onto the "unbent" part)

Would the base of the boomilever touch the testing wall? How would it? (the hex nut and flat washer are in the way, or are they?)


Sorry for all the questions! I'm new to this event :?


P.S. A drawing would be helpful and would require less words to explain stuff :) :lol:

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Re: How to mount boomilever onto the J-hook

Post by retired1 » September 12th, 2018, 5:49 pm

Look in past years wiki. I think that there was a diagram of the hook.
Last time around, the kids used a round birch wood dowel between the tension members and this went into the hook. Anything else probably will not stay on the hook. For less weight,later we rounded the center portion of a hard balsa stick and this went into the hook. Then we put a lot of pressure on this stick (in the hook) and it slightly compressed it to a desired shape. The stick was notched to just accept the tension member. Getting the angle correct on both sides took a bit of trial and error. We found a 2 component polyurethane glue that was fantastic as it was a bit flexible I think that it was Devthane 5. The one that they sell in local craft stores is not good. I think that it was Devthane 3. You can get the 5 online for 8 or 9 dollars if you search very well. It is normally like $25 or more.

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Re: How to mount boomilever onto the J-hook

Post by Carrot » September 13th, 2018, 5:30 am

retired1 wrote:Look in past years wiki. I think that there was a diagram of the hook.
Last time around, the kids used a round birch wood dowel between the tension members and this went into the hook. Anything else probably will not stay on the hook. For less weight,later we rounded the center portion of a hard balsa stick and this went into the hook. Then we put a lot of pressure on this stick (in the hook) and it slightly compressed it to a desired shape. The stick was notched to just accept the tension member. Getting the angle correct on both sides took a bit of trial and error. We found a 2 component polyurethane glue that was fantastic as it was a bit flexible I think that it was Devthane 5. The one that they sell in local craft stores is not good. I think that it was Devthane 3. You can get the 5 online for 8 or 9 dollars if you search very well. It is normally like $25 or more.
What do you mean by rounding the center portion of a hard balsa stick? Also, could I ask why you compressed the balsa stick out of its original shape? So, if you just used a dowel, would you still add pressure to the dowel before attaching it to the tension members?

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Re: How to mount boomilever onto the J-hook

Post by baker » September 13th, 2018, 7:22 am

J bolt installations guide lines from National page...
https://www.soinc.org/sites/default/fil ... lation.pdf

J bolt specs.
https://www.soinc.org/sites/default/fil ... ns2014.pdf

In the 2014 Wiki there was some discussion about a 1/2 inch dia dowel fits the inside of the hook. Use your imagination for the connection.

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Re: How to mount boomilever onto the J-hook

Post by retired1 » September 13th, 2018, 12:06 pm

Carrot wrote:What do you mean by rounding the center portion of a hard balsa stick? Also, could I ask why you compressed the balsa stick out of its original shape? So, if you just used a dowel, would you still add pressure to the dowel before attaching it to the tension members?
It was square balsa That we knocked the square corners down. Under stress, all balsa will compress which would slightly lower the boomilever tip. Regular wood will not compress that much, so it is not necessary for it.

We rounded the center so that the pull would be uniform regardless of boom orientation. For some reason, the kids chose to.
Last edited by Unome on September 13th, 2018, 2:00 pm, edited 1 time in total.
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Re: How to mount boomilever onto the J-hook

Post by Araluen » September 20th, 2018, 7:31 am

I read over all the forums for the build events i this was the closest one to the question i had. Are we allowed to remove the wingnut connecting the hook to the wall, connect our boom, and then reconnect the wingnut to the hook? Thus our boom could be flat against the wall. Or are we not allowed to remove the wingnut? :?: If we're not allowed too is the most logical idea to connect the beam using a balsa beam that goes around the hook?

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Re: How to mount boomilever onto the J-hook

Post by Unome » September 20th, 2018, 11:24 am

Araluen wrote:I read over all the forums for the build events i this was the closest one to the question i had. Are we allowed to remove the wingnut connecting the hook to the wall, connect our boom, and then reconnect the wingnut to the hook? Thus our boom could be flat against the wall. Or are we not allowed to remove the wingnut? :?: If we're not allowed too is the most logical idea to connect the beam using a balsa beam that goes around the hook?
The closest the rules get to forbidding removal of the hook, as far as I can tell, is 3.b - which is not quite outright forbiddance. Most event supervisors probably wouldn't allow it. The method you mention is the generally accepted method of attachment.
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Re: How to mount boomilever onto the J-hook

Post by dholdgreve » September 21st, 2018, 5:10 am

Araluen wrote:I read over all the forums for the build events i this was the closest one to the question i had. Are we allowed to remove the wingnut connecting the hook to the wall, connect our boom, and then reconnect the wingnut to the hook? Thus our boom could be flat against the wall. Or are we not allowed to remove the wingnut? :?: If we're not allowed too is the most logical idea to connect the beam using a balsa beam that goes around the hook?
Take a look at 5iii... "One Mounting Hook must be attached to the Testing Wall by the Supervisor with the “opening” up and installed to allow 2.5 cm +/- 0.1 cm clearance between the wall and the
closest edge of the Hook. The Hook must be secured in place with a hex nut and flat washer on the front side and a wing nut and flat washer on the back side of the Testing Wall. The Hook must be horizontally aligned by centering between the sides of the Testing Wall approximately 5.0 cm below its top. The centerlines of the holes must be visible on the face of the Testing Wall."This rule would w3

This rule would seem to indicate that the hook MUST be attached by the Supervisor, not the contestant. This avoids the possibility of inaccurate put backs.
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Re: How to mount boomilever onto the J-hook

Post by bearasauras » September 24th, 2018, 4:49 pm


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Re: How to mount boomilever onto the J-hook

Post by sciencecat42 » September 30th, 2018, 11:43 am

Has anyone made a base yet? Is it best to drill a hole for the J Hook? Or is there another way that’s just as stable?

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