OK. so in doing calculations on the phone with Eddie, I have determined some things for a ring spinner to work and be reasonable to build.
1) the raw materials and size
----------> McMaster Carr sells 1/4" chrome-moly steel in 6" x 36" pieces. This limits the construction of our ring to 6 inches tall, and the easiest circumference is 9 feet (3 strips) which gives us a diameter of 34.377 inches.
2) the weight
----------> The density of chrome-moly steel is 0.283 lbs/cu in. The ring is 0.25 x 6 x 108 = 162 cu in times .283 = 45.846 lbs.
3) the construction
----------> The ring would have a chrome-moly tube welded on the inside with a bearing running above and below it to support the ring. This tube would be 1 x 1/2 with a wall thickness of .065" giving us a .1781 sq in cross-sectional area, over 9 feet gives us an additional 5.44 lbs in the ring, totaling 52.286 lbs.
4) the speed
----------> The ring is powered by 3 short mags (at 120 degree angles) with right angle gearboxes and wheels pressed against the inside of the ring. The speed of the teeth has to be around 150 mph. This means that the ring needs to spin at least 1500 RPM to be effective. The short mags spin at 6000 RPM, which means that the ideal final ratio would be around 3:1. The best way we came up with to do this was to have a 1:2 gear ratio in the right angle gearbox, and then use a wheel. A 6 inch wheel gives a final ratio of 2.823:1 and a final RPM of 2125 and a linear velocity of 217 mph. If we were to use a 5 inch wheel it would give a ratio of 3.388:1 and an RPM of 1771 and a linear velocity of 177 mph.
5) the drive
----------> The drive system is just two Team Whyachi gearboxes with two short mags, and two eight inch wheels. It should be simple.
6) weight of everything else
----------> The weight of the five short mags is 19 lbs. The weight of the two Team Whyachi gearboxes is 9 lbs. 4 battery packs weigh about 10 lbs. This totals 38 lbs, plus 52.286 for the ring, totaling 90.286 lbs leaving about 30 lbs for everything else: supports, armor, frame, right angle gearboxes, wheels, electronics, etc. It is doable, but we are gonna have to drill holes in the ring.
I will have a rough CAD drawing hopefully by tuesday. I think this design is the best 120 lb design because it's original, and the design does require some real engineering to make it work.
Saturday, October 18, 2008
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5 comments:
Dan, I was working on a ring spinner tonight also but i have a different design. it's hard to explain most of it with out a picture (im working on that for tuesday), but i can tell you that it only uses 2 short mags to accelerate the ring, these currently dont need gear boxes, and if you make the ring out of titanium with a diameter of 36" and .1629 lbs./cubic in it would weigh 67.9 lb with a thickness of .625". the aforementioned short mags would have a rubber wheel (scooter?) on the axle. these wheels would ride on a circular track that would be attached to the frame/drive train. i haven't figured out what the frame and wheel placement will be but i'll have that done by tuesday. 8" drive wheels sound good and i'm planning on using the same shortmag/gearbox that copperhead3 used.
*Depending on my work ethic tonight and tomorrow, the design could be presentable by monday.
**i really don't think that 1/4" steel is going to be strong enough, i mean thats the same thickness of my pencil. remember copperhead's drum is roughly 3/4" thick and it received some gashes that were almost 1/4" thick last year. i dont think it would hold up as well. steel may be cheaper than titanium but what your proposing is probably more expensive in the long run (rust, repairs, etc.) any way those are just my thoughts on the subject we can talk about it more on tuesday.
I would be very interested in your design. It's about time someone actually put some effort into something! as for Copperhead's drum, it's actually 0.412" thick, so you're a little off there. And for titanium, 5/8" titanium is WAAYYYY overkill. we could get away with 3/8" and be fine. I promise, titanium is ridiculous. I agree, 1/4" steel is probably a little under what it should be but you have no idea (i think) how freaking expensive titanium is, and how hard it is to work with.
4130 chrome-moly steel in 6" x 36" sheets, 1/4" thick are $50.53 each on McMaster Carr (part #4459T62). We need 3.
A sheet of titanium, 6" x 50" x .020" thick costs $200.67. We would need 2.
The thickest titanium plate McMaster Carr has is .125" thick, and a 6" x 6" sheet of it is $166.66. This is the only size they sell. We would need 18 of these, and then we would need to bend them and weld them, which would be nearly impossible for us to do ourselves.
McMaster also sells 1/2" thick titanium, in 3" x 36" bars, so we would need to weld together 2 rings of 3, totaling six bars, at $862.01 EACH.
Titanium is freaking expensive.
It would be nice if we could find someone to donate it, but the likelihood of that is small. Granted, with enough money, we could probably do anything, so see what you can do about getting other people to help out. And let's see your design on tuesday! :]
oh, and if you're thinking of the Sweeney's Excellerator 3, which had a beastly titanium shell, the shell alone cost $10,000. They have a LOT of money.
I see your point and i think 3/8" steel is what we should do for this design. it's only an extra five pounds and as long as the frame isn't too heavy weight shouldn't be a problem.
Oh, i also found a website that might help people when calculating densities of materials and other stuff.
http://www.allmeasures.com/Formulae/
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