Dome Calculations...

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Dome Calculations...

Postby total_loser » Sat Jun 30, 2012 2:29 pm

I'm about to drill the vertices on my 3V 5/8 dome but my OCD is acting up and I'm second guessing myself on whether I've done the math correctly. Would one of the experienced dome builders here mind running thru my numbers and see if I've made an error in my calculations?

Over All Length - Vertex to Vertex

A Strut - 51 4/16 - 49 11/16

B Strut - 59 3/16 - 57 9/16

C Strut - 60 4/16 - 58 13/16
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Re: Dome Calculations...

Postby BAK3R » Mon Jul 02, 2012 8:02 am

Your numbers are spot on, but I'd suggest you round them to 1/8s. There is no reason to be that accurate with a dome radius of 142.70. Mine was somewhere in the 108 range and my holes got off by up to 3/16 and never became critical. Your bends @ 10 and 12 degrees are not critical either, just get close and as you bolt the dome together every strut end will bend into place.
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Re: Dome Calculations...

Postby total_loser » Mon Jul 02, 2012 12:19 pm

Thanks! I've been trying to get up enough courage to start drilling for weeks now but I kept having this overwhelming feeling that I'd made an error somehow. I was becoming really antsy 'cause time is getting short and I needed to get it finished so I can do at least one practice set-up and complete my covering. As far as rounding my measurements to 8ths, it's just as easy to mark and drill using 16ths so I'm gonna stick with that. Thanks again.
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Re: Dome Calculations...

Postby some seeing eye » Mon Jul 02, 2012 12:53 pm

With that many to drill, assume you are making a jig, or four. One to drill all the first holes based on the end of the pipe. Then 3 with a locating pin your vertex distance from the drill bit. You might also want some jigs for center punching where you are going to drill. Imagine this is all covered on the various websites. Best -
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Re: Dome Calculations...

Postby Mule » Mon Jul 02, 2012 12:56 pm

desert domes website has a reverse dome calculator as well as a regular calculator. you can enter in any strut length on the reverse calc and it will give you you radius and the other strut lengths. I have used it before and can verify it is accurate. While 1/8 from 1/16 shouldn't be a prob, make sure your struts are as consistant as possible, or assembly can become interesting. I found that having a jig to keep things accurate was a MUST. Good luck
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Re: Dome Calculations...

Postby BAK3R » Tue Jul 03, 2012 8:25 am

The center punch is a good idea, I didn't have one and is the reason why mine were not completely accurate.
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Re: Dome Calculations...

Postby some seeing eye » Tue Jul 03, 2012 9:03 am

Get a spring loaded (automatic) center punch. You will wear out some drill bits too. And obviously use drilling oil.
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