[Discuss] Near-space balloon: Foam ball located and purchased

James Hukill EMAIL HIDDEN
Tue Nov 1 09:09:20 PDT 2011


I might... MIGHT.. have an antenna for it.. So I will go digging..

On Tue, Nov 1, 2011 at 9:01 AM, Laura Harris <EMAIL HIDDEN> wrote:

> Thanks for all the input, everyone. Ben and I will go over the various
> approaches and make some design decisions.
>
> We'll need a pair of simple cradles to hold the halves on the workbench
> during construction and assembly- these can be as simple as a pair of
> sturdy cardboard boxes with 8" dia holes cut in one side, and edging the
> openings of the holes with something cushy like thin craft foam. If someone
> wants to fab those up and have them at the shop no later than next Sunday,
> that would be great. Otherwise, we'll throw something together on Sunday. I
> expect the ball to arrive in the next couple days so construction will be
> able to start this next weekend.
>
> I'll build a little enclosure to test the impact that gold mylar has on
> GPS performance- will have it at the shop next Sunday.
>
> Does anyone have any epoxy resin- not the glue, but the stuff used for
> fiberglassing? West Systems 105 is the material of choice but it's spendy-
> $45 for a quart of resin and the fast hardener + whatever shipping costs.
>
>
> L
>
> ------------------------------
> *From:* Thomas A Ramsey <EMAIL HIDDEN>
> *To:* EMAIL HIDDEN
> *Sent:* Monday, October 31, 2011 7:11 PM
>
> *Subject:* Re: [Discuss] Near-space balloon: Foam ball located and
> purchased
>
> I'm liking the nylon all-thread idea but I am a little concerned with it's
> strength. If we only have the one all-thread and it breaks our strips we
> lose the bottom half on the rig. I also don't trust velcro AT ALL. If it
> becomes wet or consistently stressed it will disconnect. Zip ties are great
> but difficult to reuse (they can in fact be reused). If we decide against
> zip ties I propose using multiple all-threads. Perhaps three or four; one
> down the center then the others at 45 degrees from the top center straight
> (nearly so to avoid each other) through. Nylon to keep weight down. I know
> it may make for more supports to work around but we should be able to
> handle it.
>
> I really like the strobe ideas as well. If we do have a separate strobe
> rig I think it may need to be insulated as well. I've read temperatures as
> low as -60 to -70 Celsius at the altitude we expect to go and most consumer
> grade electronics like leds are only rated about -20.
>
> -Tom
>
> On Mon, 31 Oct 2011 14:35:59 -0700 (PDT), Laura Harris wrote:
> > We can use nylon all-thread for the central support rod, if we go that
> > route. Long velcro-enabled straps would be reusable and strong though
> > a bit heavier that zipties (but not by much). If we used a net, we'd
> > still want to secure the halves together (unless you were thinking of
> > drawing the net up into a tight neck at the top . . .). I'm leaning
> > towards the nylon all thread center support rod approach, personally.
> >
> > As for the interior construction, the interior walls, floors, and
> > ribbing are 5mm foam-core. I was thinking of using gold mylar film for
> > the reflective insulation, but we can go without it and fill dead
> > areas with extra foam.
> >
> > Reasoning behind a partial hard-shell was assuming the ball will land
> > bottom down so a full shell could be avoided to save weight. Still, it
> > would definitely make it a tougher rig- more likely to survive for
> > reuse. I was thinking of using fiberglass with epoxy resin for the
> > hard shell.
> >
> > Idea for paint scheme: paint the bottom 3rd black and the rest red.
> > Black so it is easier to see on the way up (against the sky) and red
> > so it stands out on the ground. Also, a fluorescent colored parachute.
> >
> >
> > We can use 1-watt LEDs for strobes. With the short duty cycle a strobe
> > requires, we won't need heat-sinks for the LEDs and they are bright
> > enough to be easily seen in daylight. A simple 555 timer driving a FET
> > switch is all we'd need for a driver. Another thing we can do is hang
> > a strobe from the tether. That way its weight is not considered part
> > of the 6lb payload limit (if I understand the FAA regs correctly). One
> > of those little waterproof xenon strobes doesn't weigh much, either.
> >
> > -------------------------
> > FROM: Rick Osgood
> > TO: Laura Harris
> > CC: Ben Hallert ; "EMAIL HIDDEN"
> > SENT: Monday, October 31, 2011 1:58 PM
> > SUBJECT: Re: [Discuss] Near-space balloon: Foam ball located and
> > purchased
> >
> > I just had another thought about the design of the chassis that we
> > didn't bring up at our meeting yesterday. We need to be careful about
> > the material the payload is made of as well as the GPS placement. The
> > eTrex doesn't have an external antenna so we need to make sure it can
> > get an accurate GPS lock from inside the payload. So any metal above
> > it would be a bad idea. So the chassis needs to be insulated but with
> > material that the GPS radio signals can get through.
> >
> > On Mon, Oct 31, 2011 at 1:51 PM, Rick Osgood  wrote:
> >
> >> Ben, so your idea would be to have the cord come through the sphere
> >> via a hole in the top and then attach to the inside of the bottom
> >> half? I want to make sure I understand your idea correctly. That
> >> sounds like it could definitely work and I like that it would remove
> >> the requirement for extra reinforcement on the top half. Only
> >> downside would be having the rope going through the payload where it
> >> could get in the way of the electronics.
> >>
> >> Laura, I think the zip ties idea could be cheap, simple, and
> >> effective. It would be nice to have something that didn't require
> >> cutting and replacing the zip ties every time we open and close it
> >> though.
> >>
> >> The last balloon I did, we just had a threaded rod going all the way
> >> through the center of the payload vertically. There was a washer and
> >> a nut on each side to hold the two pieces tightly together. Then a
> >> small horizontal hole was drilled through the threaded rod at the
> >> top so we could stick a sort of hook through it where the line was
> >> attached. The threaded rod was nice and strong but it will add more
> >> weight and then you have a metal rod going all the way through the
> >> center of the payload which can make the inside electronics layout
> >> more difficult. You can see it in some of the photos from this site:
> >> http://www.toddfun.com/2011/02/20/high-altitude-balloon-launch-2/
> >> [17] . Here is one example photo:
> >>
> >> On Mon, Oct 31, 2011 at 1:29 PM, Laura Harris wrote:
> >>
> >>> Ohh- that looks good, Ben.
> >>>
> >>> One idea for holding the halves together is to use a pair of
> >>> extra-long nylon zip ties running longitudinally at 90 degrees to
> >>> each other- grooves formed in the surface would keep them from
> >>> sliding off. They're strong and light and they avoid the need for
> >>> any hardware.
> >>>
> >>> -------------------------
> >>> FROM: Ben Hallert
> >>> TO: Laura Harris
> >>> CC: Rick Osgood ;
> >>> "EMAIL HIDDEN [4]"
> >>> SENT: Monday, October 31, 2011 1:12 PM
> >>>
> >>> SUBJECT: Re: [Discuss] Near-space balloon: Foam ball located and
> >>> purchased
> >>>
> >>> May I suggest that instead of attaching the cord to the top, we
> >>> run it
> >>> down and attach it to where the battery bay is? This way the whole
> >>> thing is 'sitting' on the cord and we can cut any weight created
> >>> by
> >>> reinforcements that would reach to the top of the sphere. Namely,
> >>> the
> >>> only 'strength' needed would be at the bottom where it's already
> >>> planned to exist. This also reduces risk of retrieving just the
> >>> top
> >>> of the sphere. :) I've attached a modified version of the
> >>> drawing.
> >>>
> >>> - Ben
> >>>
> >>> On Mon, Oct 31, 2011 at 12:51 P.M, Laura Harris wrote:
> >>> > The ball comes split in half so it's just a matter of holding
> >>> it together in
> >>>> flight. I've attached a pic of a sketch showing a preliminary
> >>> idea for
> >>>> construction.
> >>>>
> >>>> ________________________________
> >>> > From: Rick Osgood
> >>>> To: Laura Harris
> >>>> Cc: "EMAIL HIDDEN [9]"
> >>> >
> >>>> Sent: Monday, October 31, 2011 10:54 AM
> >>>> Subject: Re: [Discuss] Near-space balloon: Foam ball located and
> >>> purchased
> >>> >
> >>>> Sweet! Do you plan to mold something around the sphere? I'm
> >>> curious to see
> >>>> your final design and how we will be able to open it up and
> >>> mount
> >>>> everything.
> >>>>
> >>>> On Mon, Oct 31, 2011 at 9:53 AM, Laura Harris wrote:
> >>>>
> >>>> I found a 12" dia hollow polystyrene foam ball and purchased
> >>> one. Should be
> >>> > here in a few days. This is it:
> >>>> http://www.plasteelcorp.com/mm5/merchant.mvc [12]?
> >>>> This dramatically accelerates the build progress. :)
> >>> > L
> >>>>
> >>>>
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> >
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