Boomilever B/C

[chalker]

Am I missing something, or is this indeed the intent?

Unofficially of course, there was no explicit intent to exclude certain designs. What you are missing is that there are a lot of things, people, and processes that go into the rules making process. Sometimes certain aspects / impacts of the rules don't even occur to us or we don't spend significant time considering because of higher priorities.

Thus we have the FAQ / clarification process in place. However, we are hesitant to issue official clarifications except in 'game breaking' situations. I personally don't believe that is the case here, thus why I think we'll be unlikely to issue one related to this. While I understand how frustrating it can be for there to be some uncertainty regarding this or inability to produce the optimal design, the rules are generally 'set in stone' now, and thus everyone needs to work to the best design they can within the constraints provided.

Of course you are more than welcome to submit a FAQ request and lobby for a clarification. I'm just trying to provide you with some insight from one of the many people who are involved in the process.

[jander14indoor]

<SNIP> I know it's more difficult to specify but a minimum length would really make the event more about design and engineering than who can construct a boomilever to the most exacting specification, which, to me(and I may be totally wrong) seems more to the point of science Olympiad.<SNIP>

Just to take a slighty contrarian view. In real world engineering seldom are the boundary conditions known precisely. Good design tries to take account of these uncertainties and work well under the widest range possible. It is not unreasonable for the rules writers to intentionally build in uncertainty as part of the challenge to the students.

Not saying it was conscious in these rules, but its there now, so it IS part of the challenge.

Thanks,

Jeff Anderson
Livonia, MI

[dholdgreve]

<SNIP> I know it's more difficult to specify but a minimum length would really make the event more about design and engineering than who can construct a boomilever to the most exacting specification, which, to me(and I may be totally wrong) seems more to the point of science Olympiad.<SNIP>

Just to take a slighty contrarian view. In real world engineering seldom are the boundary conditions known precisely. Good design tries to take account of these uncertainties and work well under the widest range possible. It is not unreasonable for the rules writers to intentionally build in uncertainty as part of the challenge to the students.

Not saying it was conscious in these rules, but its there now, so it IS part of the challenge.

Thanks,

Jeff Anderson
Livonia, MI

Jeff, Although I understand your concept, I would have to disagree... I actually work in that real world, and the very first thing that is done is to identify those exact parameters... how wide is the gorge we are bridging over? How deep? How many lanes? how much traffic? are there load limits? can existing traffic be detoured? If the answers cannot be retrieved from someone, then investigations are launched to procure those answers from within before the first stitch of engineering is done... That is exactly what is happening here. The questions are being asked. In the real world however, a gorge can be surveyed and design parameters established... here, we are asked to design and engineer a structure without knowing, and having no way to identify ourselves certain critical parameters that we cannot retrieve on our own... This paradox would frustrate most Professional Engineers... to be asked to design a structure to support a specified load, not knowing if the load would be suspended directly beneath it, or hung several "feet" below, allowing for a much deeper structure.

[yoliu]

I'd like to assume the common sense approach, and believe that it is NOT the committee's intention to implicitly prohibit certain designs - like Dr. Chalker "unofficially" stated above:) 2013 rules had no specification of eyebolt, but probably every ES provided common eyebolts with at least 2" shaft to accommodate almost all designs. So we probably can assume the same for 2014. Otherwise, the only 100% sure design that allows for the shortest 1" shaft would be the single deck wide tension boom as shown in the wiki - probably less than 40% of all boom types towards the season end. The issue just got "hot" as the max length is added with no minimum so everyone wonders why and starts begging for clarification

The same goes for the J-hook definition of "UP". I'd like to assume it means almost at the 12 o'clock position (as shown in the rule book illustration) - as much as the ES's eyes can tell. I assume it does not mean that ES would put it at 1 o'clock or 2 o'clock position and call it "up" (otherwise base would not fit at all or rotate badly and the J-hook can rotate and un-thread due to Z direction moment). I would also assume that the J-hook is almost perpendicular to the test wall - otherwise the J-hook could be slanted whichever way the 1/4" hole was angled at(and could cause the tip of the J-hook to drop way below the 1/4" mounting hole center line - imagining it angles down at 45 degree angle for example - you could have 25mm to the wall horizontally, but 25mm below the mounting hole center vertically therefore short change the contact depth by 25mm) - causing the boom unable to fit or drop below the contact line even with normally enough design margin.

So in short, I assume folks need to design the booms to tolerate reasonable margins (J-hook extruding at 25mm +/- 1mm, almost 12 o'clock orientation, probably 2mm/3mm safety margin with the 15cm/20cm contact line, distal end can fit at least a short 2" shaft eyebolt, etc etc). I assume we should not get into the extreme interpretation of the rules as "Gotcha" Well, it is the hope any ways:) Just 2c.

[jander14indoor]

dholdgreve, we are probably saying some of the same things, but maybe not, or maybe our perspectives are different.
My business is automobile design. With a strong background in reliability & quality which tends to drive me to view the world as uncertainty and variability.
Drivers cover a huge range of sizes, we don't try to accomodate all, but do accomodate a wide range, look outside that range, and recognize the results aren't the same for all drivers in terms of comfort, ergonomics, etc. Driving behavior is wide ranging. Again, we design around specific points, but look and and try to accomodate a range. And we have to cover the range well to sell cars in volume vs niche marketing.
Roads are hugely varying, different lane widths, surface texture, pot holes, curves, hills, bumps, you name it. Our cars have to accomodate a huge range in some sort of efficient manner. Our trucks an even wider range.
And when the range is too wide, or there are multiple peaks we do niche design and market. Thus police, cab and limo special versions of otherwise normal looking cars. And while a police special may not seem very different to a casual driver and the way they might use it, the regular version of that car would not last long in police service.
And that leaves out manufacturing variability entirely.

Yes, we spend a LOT of time defining the range of human variability, driving style, road conditions etc. Yes we design to specific points in the variability curves. But we have to perform across the range to satisfy customers. And it is a competition. Inefficent performance, not hitting the range correctly, etc are a lot of the explanation on why the US big three lost out to the competition for so long.

What I'm suggesting for SO competitors is to be aware of the variability (it will exist in the best, most precisely written rules) and account for it in their designs. Consider risks explicitly. Specifying a vertical hook will inherently have SOME uncertainty. Whether its specified as from 1-11 oclock, plus or minus one degree, or plus or minus a tenth of a degree you should know how your design is sensitive to that and understand your risks accordingly.

Oh, and I'm NOT trying to say to not ask for clarifications. I'm good with that. Just that whatever the answer is, there will still be uncertainties and risks to manage.

Jeff Anderson
Livonia, MI

[thsom]

....the base had not chance of moving and this allowed for much more fixed testing and predictable results...

You're absolutely correct in that there will be some additional instability and maybe we'll see some students come up with clever ways to overcome this challenge. This might end up shaking up the event and might even lead to some unorthodox designs.

Speaking of fixed testing and predictable results, the students in Wright Stuff/Gliders want to have a word with you ^^.

The students in Wright Stuff/Gliders want to have a word with me? What? I'm confused...

[iwonder]

Jeff, Although I understand your concept, I would have to disagree... I actually work in that real world, and the very first thing that is done is to identify those exact parameters... how wide is the gorge we are bridging over? How deep? How many lanes? how much traffic? are there load limits? can existing traffic be detoured? If the answers cannot be retrieved from someone, then investigations are launched to procure those answers from within before the first stitch of engineering is done... That is exactly what is happening here. The questions are being asked. In the real world however, a gorge can be surveyed and design parameters established... here, we are asked to design and engineer a structure without knowing, and having no way to identify ourselves certain critical parameters that we cannot retrieve on our own... This paradox would frustrate most Professional Engineers... to be asked to design a structure to support a specified load, not knowing if the load would be suspended directly beneath it, or hung several "feet" below, allowing for a much deeper structure.

To clarify, I do industrial electronics design in the summer, I work for an power systems company specializing in marine and drilling control/power systems.

Ok, I think I see what Mr. Anderson is saying, and it's the same as what you're saying from another angle. Yes, you absolutely need exact specs in the real world, and you would need to know how wide a gorge is, how deep, lanes, load limits, etc. However, lets think of this as a load limit, when you design the bridge and put a nameplate rating of 20 tons on it, it can hold more than 20 tons. From the mech e's I've talked to it might handle as much as 100 tons depending on the situation.

In our case, the values are different, but the premise is the same. The bolt could be as small as possible but only up to 4". For my case, I want the longest eyebolt possible. Therefore, I'll think of it as, I'm going to build to accommodate a 1" eye bolt, and that way I'll be perfectly fine with a 4" one.

Basically, there are certainties in designs, but it also needs to be able to handle extreme situations without failing.

[yoliu]

I think the focus of the discussion is not about how much force variation (due to swaying bucket) is introduced by 1" vs 4" eyebolt. It is rather that with 1" eyebolt and a big eyehook, most designs would simply be implicitly prohibited. So it is no longer about design to counter the force variation, but whether you can use certain designs at all or disqualify half of the designs at competitions - when interpreting the rules to the extreme. I do not think that is the intention.

[penclspinner]

....the base had not chance of moving and this allowed for much more fixed testing and predictable results...

You're absolutely correct in that there will be some additional instability and maybe we'll see some students come up with clever ways to overcome this challenge. This might end up shaking up the event and might even lead to some unorthodox designs.

Speaking of fixed testing and predictable results, the students in Wright Stuff/Gliders want to have a word with you ^^.

The students in Wright Stuff/Gliders want to have a word with me? What? I'm confused...

I was referring to any flight building event, it's hard to find a perfect venue to fly things in.
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[Balsa Man]

Interesting discussion; interesting issues.
Two very different kinds of issues in discussion.

When I posted a few days ago, I was (incorrectly) assuming/remembering that last year’s rules had included an eyebolt length. As yoliu noted, they didn’t.

So this year’s rules take us from only the ¼” shaft diameter specified, to ¼” shaft diameter with a maximum length (of 4”) now defined. As I noted, should an Event Supervisor for whatever reason decide to use/provide a 1”, ¼” shaft diameter eyebolt, they would be fully within the rules. With an eyebolt that short, you can’t mount a load block to any reasonably conceivable single compression member boom design.

On the one hand, this was true for last year – and as far as I know, both from postings on this board, and communications with other competitors and coaches, nobody ran into the potential problem I raised; having a single compression member design that requires...1 ½ to 2” minimum eyebolt to not be Tier 4’d, and showing up and being confronted with an eyebolt that was too short to work. That would suggest there’s not a problem. But, on the other hand, as a number have pointed out, when there is ES latitude around a constraint in the rules, you’re asking for trouble if you don’t design to the worst case.

So this issue – while it did in fact exist -wasn’t on anybody’s radar screen last year. Single compression member booms needing an eyebolt length greater than the minimum commercially available appeared, evolved, and were clearly competitive. The constraint it effectively imposed wasn’t recognized, and wasn’t encountered. Makes it totally understandable it wasn’t seen/considered in the process of working up this year’s rules. So, what does the fact that it is now recognized mean? It sounds to me like there was no intent by anyone in the rule making process to rule out such designs. Given the lack of recognition of the potential problem, it also seems fair/reasonable to assume there was no intent to build in a wild card effect- where someone using such a design could sail through one level of competition, and show up at the next and get Tier 4’d.

So, what does recognition of the issue that has now emerged mean, in light of the ... let me call it somewhere between apparent and possible reluctance to provide clarification?? Is this a “game breaking” constraint/wild card? One could argue that either way. Rather than go down that path, I would have to argue that, because of the now recognized consequences of the rule as written, a decision to not clarify and provide a minimum length would have to come from an intention to rule out a design approach, and impose a wild card factor. If such intentions are not there, not at work, with all due respect, it seems to me there is only one reasonable way to proceed.