Boomilever B/C

[fanjiatian]

Why would you want to extend the load a bit beyond the minimum distance? Wouldn't that make the effective length of the compression member longer, which means shorter bracing distances are needed?
You would want to center the middle of the loading block with the distal ends right? Right where the tension member contacts the compression member?

[Balsa Man]

Why would you want to extend the load a bit beyond the minimum distance? Wouldn't that make the effective length of the compression member longer, which means shorter bracing distances are needed?
You would want to center the middle of the loading block with the distal ends right? Right where the tension member contacts the compression member?

As has been discussed many times- when you have a limiting dimension in the rules - something the Event Supervisor is going to measure, you want some margin of error. Center of load block has to be at least 45cm from the wall. If you use your ruler, and design to 45cm + say, half a mm beyond the minimum(45.05cm), and the supervisor's ruler is a little longer, and he/she measures you at 44.95, you're Tier 2. You want it as little over 45 as you can....get away with. I've seen "good" metric rulers with 1mm+ variation at 45cm. That suggests 2mm is a reasonabe safety factor. The 45.2 I tossed out is 2mm >45cm. So, that's less than 1/2 of 1%, VERY small adjustment to bracing intervals.
And yes, you want the load centered VERY precisely on the tension/compression member intersect, otherwise you're inducing bowing into the comperssion member.

[UQOnyx]

Yes, that is true. The thing with Boomilever in my area, is that they will check, but they won't check to the millimeter or the half millimeter. If I remember correctly, they had an L-Jig, with a line drawn on it for max and min distance. I am not sure if it is super accurate though, so usually I leave about a centimeter or half for margin of error.

[chinesesushi]

Hi guys. I'm having problems with the base. I've read Aia's guide, but I do not know how to make the holes in the base appropriately. How do you account for the angle of the tension members in the base? Do you drill the holes into the base? Also, I've heard that glue is sometimes stronger than the wood itself. If I had a square piece of wood with a 1/4" hole drilled into it, and I attached the tension members to either side, and then glued on the ends of the base to sandwich the tension members with the square piece (end piece-tension member-square piece-tension member-end piece), which would be stronger, this or the one with the holes drilled into it? Thanks.

Example: (Click to Show Hidden Text)

[img]http://i.imgur.com/ziNPAaZ.png[/img]

[iwonder]

As balsaman pointed out, you may want to go over the new rules, the base has changed compared to Aia's guide.

[GeorgeInNePa]

Regarding the post about the eye bolt, I'd say continue at your own risk in October clarifications will open up and you'll be able get a real answer(hopefully) to your question. But don't let that stop you from working on a design, just keep in mind you might have to tweak it later on.

Speaking unofficially of course, I don't think we'll provide a rules clarification that specifies the eye bolt in more detail. Thus you are going to need to be prepared for any of the possible contingencies discussed here so far. of course you could always contact individual event supervisors before a tournament and try to convince them to provide a certain style eye bolt......

Hmmm… I must be missing something…. The lack of specification of the (minimum) shaft length for the load block eyebolt has, I believe, the effect of eliminating booms with a single compression member. Given that, and, if, in fact, no clarification is forthcoming, one has to conclude an intention to do so. That leaves me really curious as to why…. the powers that be would want to do that.

The shortest ¼” diameter (1/4-20) eyebolts commonly available have a 1” long shaft (2.54cm). With a 2cm block thickness, and a wingnut on top of the block, that has the top of the eye right up against the bottom of the block. With either a box section, or a tubular section compression member, where the load block sits on top of the compression member, that member has to have a vertical cross section dimension….as a practical matter, in the ¼ to ¾” range. So, if a particular event supervisor decides – which is fully allowable with the rule as written – to use a 1” eyebolt, with the eye up against the bottom of the load block, then the only designs they’re allowing are two compression member ones, where there’s nothing interfering with the eye. Looking at both Regionals feeding into State competitions, and State feeding into Nationals, a design that might be fine for one level of competition where the ES decided to use a 2” or 3” eyebolt, would be put in Tier 4 for the next – where the ES decided to use a 1”, and the boom “cannot accommodate the loading block.” Sorry, but that doesn’t make sense. Am I missing something, or is this indeed the intent?

I agree. This will limit the design possibilities.

[fanjiatian]

Got it Len! Just checking

[balsaandbass]

I was wondering what the weight range is on most boomilevers? Thanks

[ckssv07]

I was wondering what the weight range is on most boomilevers? Thanks

Last year, mine ranged anywhere from 5.5g- around 7 g I believe for competition, but I am not yet sure how much the mass will differ this year.

[baker]

Folks, there has been very little discussion about the biggest change/challenge of this years build. The mounting block on the 'hook'. There will be some new designs and weight changes. How about a wood dowel mounted between two blocks of wood. Anybody else have some ideas??