Towers B/C

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Balsa Man
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Re: Towers B/C

Post by Balsa Man » November 12th, 2016, 6:40 am

hearthstone224 wrote:Hey everyone, I'm going to put the numbers I got out there for verification. The "safe strength" column refers to the strength a stick of 36'' balsa must have to be braced at that certain interval and work out. I want to get this part right once and for all so that I don't need to think about this anymore.

Is there any disagreement? If not I think people can use these numbers.

I think only the colored ones will matter because the sticks usually don't reach 220 g in BS :) At least I don't have any.

So do you think the main composition will be bracing at 1/5th interval around 80 BS? Because I thought maybe we could be using 1/4th interval with sticks around 130BS or so. They are fairly heavy though.

And just out of curiosity, can we brace at a let's say 1/4.5 interval? I know it sound fairly weird but would that maybe have a positive tradeoff?
Nice. Essentially correct (I get a slightly different number in the "Proportion" column for 1/7th (0.96 vs your 0.91), which makes makes the number in the "Multiplier" column 109.26 (vs your 120.76) might want to re-check that.

Your conclusion that bracing at 1/5 intervals for a stick with a 36" buckling strength testing at 80 gr should hold is correct, and that a stick with a 36" buckling strength of 130gr should hold at 1/4 interval, and that to go to 1/3 interval, you'd need a stick testing at 220gr.

The (1/8 x 1/8 x 36") stick weights you should expect to get those buckling strengths are (from the table I'm having trouble attaching) are:
1/5 interval- 1.5-1.6gr range
1/4 interval- 2.2-2.3gr range
1/3 interval- 3.5-3.6gr range. I'm not surprised you haven't seen any this heavy, it's pretty uncommon/pretty high density. They do exist; in fact, you can order sticks up to 4.7gr from Specialized Balsa . They start to get pricey as you push past 3gr. Bottom line, 1/5 and 1/4 bracing intervals should be achievable with common/typically available balsa.

As to 1/4.5 interval, you end up with the same number of bracing points/ ladders you would have at 1/5 intervals, with top or bottom one being significantly shorter than the others; the leg in that shorter section would be much stronger than needed (inefficient), and the other sections would be longer, requiring heavier leg material than would be needed with 1/5 bracing. By evenly dividing, you minimize the leg strength needed.

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Re: Towers B/C

Post by BrS » November 13th, 2016, 8:23 am

what's some secure, sturdy packaging gear for storing and cushioning builds and devices for teams that travel to invitationals out of state, especially if they are flying?

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Re: Towers B/C

Post by bernard » November 13th, 2016, 12:31 pm

BrS wrote:what's some secure, sturdy packaging gear for storing and cushioning builds and devices for teams that travel to invitationals out of state, especially if they are flying?
Securely attach a sheet of foam board insulation to the inside of a slightly oversized plastic storage box, then securely and carefully tape or pin (without puncturing your tower) your tower to the foam. Bring as carry-on if you have any concerns with security personnel handling your device. If your luggage will only undergo mild agitation, securely fixing your tower to the inside of the box is not necessary.
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Re: Towers B/C

Post by Random Human » November 13th, 2016, 1:20 pm

BrS wrote:what's some secure, sturdy packaging gear for storing and cushioning builds and devices for teams that travel to invitationals out of state, especially if they are flying?
We usually have a plastic box (big enough for our tower) where we put styrofoam inside of it to prevent the tower from moving.
Most airline companies do not allow storage big enough for our boxes we use in the overhead compartment so you may need to find a new solution. Maybe shipping the thing with the luggage or something.

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Re: Towers B/C

Post by hearthstone224 » November 13th, 2016, 4:21 pm

Yeah, you're right I got the 1/7th column wrong, but to be honest, I don't think I'll be using any of those sticks :)

So an ideal tower that places well you would think has around the 1/5th interval for each leg at around 80 g BS? Alright, I'll look out for that. I still haven't figured out the tradeoff between using 1/4th interval qualifying legs vs 1/5th interval qualifying legs. With 1/5th interval, I have a much wider variety to choose from.

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Re: Towers B/C

Post by Balsa Man » November 13th, 2016, 6:06 pm

hearthstone224 wrote:Yeah, you're right I got the 1/7th column wrong, but to be honest, I don't think I'll be using any of those sticks :)

So an ideal tower that places well you would think has around the 1/5th interval for each leg at around 80 g BS? Alright, I'll look out for that. I still haven't figured out the tradeoff between using 1/4th interval qualifying legs vs 1/5th interval qualifying legs. With 1/5th interval, I have a much wider variety to choose from.
Given that, I'd lean toward the 1/5 interval.....

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Re: Towers B/C

Post by baker » November 15th, 2016, 2:31 pm

Bass Wood - a 3/32 x 3/32 x 24 inch (60.96cm) weighs in the 1.5 gram range. That's about 6 grams in leg weight. Bass wood is very good in compression and very consistent thru out the length. Haven't tried to plot the BS, but worth looking into...

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Re: Towers B/C

Post by Random Human » November 15th, 2016, 4:15 pm

baker wrote:Bass Wood - a 3/32 x 3/32 x 24 inch (60.96cm) weighs in the 1.5 gram range. That's about 6 grams in leg weight. Bass wood is very good in compression and very consistent thru out the length. Haven't tried to plot the BS, but worth looking into...
I think the trade off between bass is not worth it, simply bass is way to heavy, even if it is strong. Balsa on the other hand has a more flexibility and more light weight. Anyways, your choice though even though I would say balsa is much better than bass.

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Re: Towers B/C

Post by HandsFreeCookieDunk » November 15th, 2016, 5:41 pm

baker wrote:Bass Wood - a 3/32 x 3/32 x 24 inch (60.96cm) weighs in the 1.5 gram range. That's about 6 grams in leg weight. Bass wood is very good in compression and very consistent thru out the length. Haven't tried to plot the BS, but worth looking into...
Bass does have its uses, but most of them are in tension applications, where I believe it has a higher strength to weight ratio than balsa. However, as Random Human pointed out, it is substantially heavier than balsa and the trade off is just not worth it in the columns, which are under compression. It might be worth looking at using some really thin stuff for the bracing, but honestly balsa of the same weight will almost certainly be good enough and not ridiculously thin. Towers are not bass-friendly.

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Re: Towers B/C

Post by Random Human » November 15th, 2016, 8:01 pm

HandsFreeCookieDunk wrote:
baker wrote:Bass Wood - a 3/32 x 3/32 x 24 inch (60.96cm) weighs in the 1.5 gram range. That's about 6 grams in leg weight. Bass wood is very good in compression and very consistent thru out the length. Haven't tried to plot the BS, but worth looking into...
Bass does have its uses, but most of them are in tension applications, where I believe it has a higher strength to weight ratio than balsa. However, as Random Human pointed out, it is substantially heavier than balsa and the trade off is just not worth it in the columns, which are under compression. It might be worth looking at using some really thin stuff for the bracing, but honestly balsa of the same weight will almost certainly be good enough and not ridiculously thin. Towers are not bass-friendly.
Yes bass wood does have it's advantages, but in the scenario given where every gram counts, bass is not a good option, for bracing balsa in my opinion is definitely the way to go. Having 1.5 gram weight for a 3/32x3/32x24 inch stick is crazy, where as a 3/32x3/32x36 balsa stick weighs about 0.7, a better weight, where you save weight to add to the braces. So maybe shift over to balsa since bass would isn't necessary in this situation.

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