[roc-chat] Re: BP for Deployment of Main Question
- From: Geoff Huber <ghuber@xxxxxxxxxxxxx>
- To: "roc-chat@xxxxxxxxxxxxx" <roc-chat@xxxxxxxxxxxxx>
- Date: Fri, 9 Dec 2011 20:47:32 +0000
If you can find a can of 4f BP it is the easy way to go. It just works.
Pyrodex and the other BP alternatives can be made to work but require more
containment to function otherwise they will not burn completely. You will
find some people who use it and have found ways to make it work.
Geoffrey Huber
(530) 891-0853 ext 3030
Geoff.Huber@xxxxxxxxxxxxx
-----Original Message-----
From: roc-chat-bounce@xxxxxxxxxxxxx [mailto:roc-chat-bounce@xxxxxxxxxxxxx] On
Behalf Of Steve Battaglia
Sent: Friday, December 09, 2011 10:36 AM
To: roc-chat@xxxxxxxxxxxxx
Subject: [roc-chat] Re: BP for Deployment of Main Question
Any difference between pyrogen/pyrodex and BP?? tried using pyrogen for
ejection bu it seems to burn slower that BP... any truth to that??
S. Battaglia
310-339-2717
Sent from my Rotary iPhone...
On Dec 9, 2011, at 10:24 AM, Kenneth Brown <ken@xxxxxxxxxxxxx> wrote:
> Spectra
>
> Ken
>
>
> On Dec 9, 2011, at 9:45 AM, Kurt Gugisberg wrote:
>
>> According to Wedge, Bryan should use 75' of shock cord. With that much
>> you could use kite string and it should still be safe. ;-)
>>
>> The question is...should it be nylon or Kevlar kite string.
>>
>> Kurt
>> -----Original Message-----
>> From: Richard Dierking
>> Sent: Dec 9, 2011 9:30 AM
>> To: roc-chat@xxxxxxxxxxxxx
>> Subject: [roc-chat] Re: BP for Deployment of Main Question
>>
>> Bryan's currently in school otherwise he would answer this himself. Yes, he
>> used a parachute for the test and a shorter/lighter shock cord (10', 1000 lb
>> vs. 15', 2300 lb). The cord was attached to both parts. He might also be
>> extending the shock cord more than 15' for the flight. The ground test was
>> energetic and the parachute was deployed nicely.
>>
>> Richard
>> > Date: Fri, 9 Dec 2011 09:22:19 -0800
>> > From: dmccue@xxxxxxx
>> > To: roc-chat@xxxxxxxxxxxxx
>> > Subject: [roc-chat] Re: BP for Deployment of Main Question
>> >
>> > Yay! I hope you also try with the parachute in there as well - it
>> > would suck to have the sections separate, but no parachute
>> > ejection. (I don't know if the 'chute is attached to both parts, or
>> > only one. If attached to both airframe sections, the bridles will
>> > puil it out for sure...)
>> >
>> > -Dave McCue
>> >
>> > On Thu, 8 Dec 2011, Bryan Dierking wrote:
>> >
>> > > Richard and I just did a ground test with three 2-56 sheer pins and 3.5
>> > > grams in one of the canisters - worked like a charm.
>> > >
>> > > Bryan Dierking
>> > >
>> > >
>> > > Le Dec 8, 2011 à 16:07, David.P.Smith@xxxxxxx a écrit :
>> > >
>> > >> Using the table on the web page I listed it came out to 4 grams. His
>> > >> table has worked well for me in the past, but I haven't used it on a
>> > >> 7.5 inch tube.
>> > >>
>> > >> Using the bottom formula on that same page and shooting for 10 psid I
>> > >> came up with 5.87 grams. Intuitively this seems closer. Of course there
>> > >> are various assumptions made that can only be validated with testing.
>> > >>
>> > >> One assumption in all these equations is 100% conversion of the solid
>> > >> black powder into gas. That seems very optimistic. With tightly wrapped
>> > >> charges as described by Dave McCue used with shear pins to hold the
>> > >> parts together a bit longer, you can produce a pretty substantial
>> > >> pressure in the tube before things start to actually move apart.
>> > >>
>> > >> Ground testing seems like a very good idea to me...
>> > >>
>> > >> David P Smith
>> > >> NAR 78668 L2
>> > >> Amateur Extra, W6DPS
>> > >>
>> > >> The opinions expressed in this email are my own and do not necessarily
>> > >> represent the positions, strategies or opinions of Southern California
>> > >> Edison, its parent company Edison International, or any of their
>> > >> affiliates.
>> > >>
>> > >>
>> > >>
>> > >>
>> > >>
>> > >> From: Richard Dierking <redierking@xxxxxxxxxxx>
>> > >> To: "roc-chat@xxxxxxxxxxxxx" <roc-chat@xxxxxxxxxxxxx>
>> > >> Date: 12/08/2011 12:14 PM
>> > >> Subject: [roc-chat] Re: BP for Deployment of Main Question Sent
>> > >> by: roc-chat-bounce@xxxxxxxxxxxxx
>> > >>
>> > >>
>> > >>
>> > >> Let me ask this first: did you come up with 4 grams per cartridge or 4
>> > >> grams total?
>> > >>
>> > >> Sent from my iPhone
>> > >>
>> > >> On Dec 8, 2011, at 12:07 PM, David.P.Smith@xxxxxxx wrote:
>> > >>
>> > >> Large areas can generate very large force if you keep the pressure
>> > >> constant.
>> > >>
>> > >> Think of it this way. For the same length of tube, the diameter
>> > >> increases the area and volume by the square of the increase in diameter.
>> > >>
>> > >> Round off a 4 inch rocket tube to 12.5 square inches times 24 inches in
>> > >> length, the volume is 300 cubic inches.
>> > >>
>> > >> Round off an 8 inch rocket tube to 50 square inches times 24 inches,
>> > >> the volume is 1200 cubic inches. Four times the volume of the 4 inch.
>> > >>
>> > >> So, if a 4 inch diameter body tube 2 feet long is pressurized to 20
>> > >> psid with a given charge, then an 8 inch body tube 2 feet long would be
>> > >> pressurized to 5 psid.
>> > >>
>> > >> 12.5 times 20 psid comes out to 250 pounds of ejection force. 50 times
>> > >> 5 comes out to 250 pounds of ejection force.
>> > >>
>> > >> So for a given ejection charge, in a range of body tube diameters, you
>> > >> get the same ejection force.
>> > >>
>> > >> On the other hand, increasing the charge to four time the 4 inch
>> > >> charge, gives us 1000 pounds of ejection force in the 8 inch rocket.
>> > >> that may be a bit much...
>> > >>
>> > >> If you just stick to the formulae published on some sites, you just
>> > >> keep increasing the charge size proportional to the increase in volume,
>> > >> which may over stress your shock cord.
>> > >>
>> > >> So how much force do you need to make the rocket come apart?
>> > >>
>> > >> Do you plan to ground test at all?
>> > >>
>> > >> David P Smith
>> > >> NAR 78668 L2
>> > >> Amateur Extra, W6DPS
>> > >>
>> > >> The opinions expressed in this email are my own and do not necessarily
>> > >> represent the positions, strategies or opinions of Southern California
>> > >> Edison, its parent company Edison International, or any of their
>> > >> affiliates.
>> > >>
>> > >>
>> > >>
>> > >>
>> > >>
>> > >> From: Richard Dierking <redierking@xxxxxxxxxxx>
>> > >> To: "roc-chat@xxxxxxxxxxxxx" <roc-chat@xxxxxxxxxxxxx>
>> > >> Date: 12/08/2011 11:36 AM
>> > >> Subject: [roc-chat] Re: BP for Deployment of Main Question Sent
>> > >> by: roc-chat-bounce@xxxxxxxxxxxxx
>> > >>
>> > >>
>> > >>
>> > >> Wow, 4 grams BP is about one half what we were coming up using the web
>> > >> and a reference book I had.
>> > >> Richard
>> > >> Sent from my iPhone
>> > >>
>> > >> On Dec 8, 2011, at 11:26 AM, "Chris J Kobel" <Chris.J.Kobel@xxxxxxxx>
>> > >> wrote:
>> > >>
>> > >> I would second David's recommendation of 4 grams, which should give
>> > >> about 200 lbs of ejection force at 5000 AGL, with the 3 2-56 shear pins
>> > >> requiring about 100 lbf to overcome.
>> > >>
>> > >> Chris
>> > >>
>> > >>
>> > >>
>> > >> From: David.P.Smith@xxxxxxx
>> > >> To: roc-chat@xxxxxxxxxxxxx
>> > >> Date: 12/08/2011 11:10 AM
>> > >> Subject: [roc-chat] Re: BP for Deployment of Main Question Sent
>> > >> by: roc-chat-bounce@xxxxxxxxxxxxx
>> > >>
>> > >>
>> > >>
>> > >> I use the "rule of thumb" on this site.
>> > >>
>> > >> http://www.vernk.com/EjectionChargeSizing.htm
>> > >>
>> > >> So, by that site you would need 4 grams of ffffg black powder.
>> > >>
>> > >> Remember that you are looking at a lot of area to apply the ejection
>> > >> pressure to. A 7.5 inch circle had a bit over 23.5 square inches of
>> > >> are. So 10 psid will give you 235 pounds of ejection force.
>> > >>
>> > >> What is the shear force rating for your pins?
>> > >>
>> > >> David P Smith
>> > >> NAR 78668 L2
>> > >> Amateur Extra, W6DPS
>> > >> The opinions expressed in this email are my own and do not necessarily
>> > >> represent the positions, strategies or opinions of Southern California
>> > >> Edison, its parent company Edison International, or any of their
>> > >> affiliates.
>> > >>
>> > >>
>> > >>
>> > >>
>> > >>
>> > >> From: Richard Dierking <redierking@xxxxxxxxxxx>
>> > >> To: <roc-chat@xxxxxxxxxxxxx>
>> > >> Date: 12/08/2011 10:10 AM
>> > >> Subject: [roc-chat] BP for Deployment of Main Question Sent by:
>> > >> roc-chat-bounce@xxxxxxxxxxxxx
>> > >>
>> > >>
>> > >>
>> > >> Say your main deployment section is 7.5" diameter, 24" long and using
>> > >> three (3) 2-56 nylon shear pins. How much BP?
>> > >>
>> > >> Also, what's the advantage of using two or more deployment
>> > >> canisters instead of just one? For multiple canisters, would you
>> > >> wire in series or parallel? (One 9 volt battery and Perfectflite
>> > >> WD altimeter with main deployment at 1100'.)
>> > >>
>> > >> Richard Dierking
>> > >> BTW: Kurt, we're not intending to turn the nose into a second
>> > >> stage :-)
>> > >>
>> > >>
>> > >> -- ROC-Chat mailing list roc-chat@xxxxxxxxxxxxx
>> > >> //www.freelists.org/list/roc-chat
>> > >> -- ROC-Chat mailing list roc-chat@xxxxxxxxxxxxx
>> > >> //www.freelists.org/list/roc-chat
>> > >> -- ROC-Chat mailing list roc-chat@xxxxxxxxxxxxx
>> > >> //www.freelists.org/list/roc-chat
>> > >
>> -- ROC-Chat mailing list roc-chat@xxxxxxxxxxxxx
>> //www.freelists.org/list/roc-chat
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>
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