Some friends would like to build a down-sized model of a two-stage sounding rocket. I'm trying to come up with a design for a timer to ignite the second stage. The timer should be triggered by a "g" switch which marks first stage ignition, and time out after (an adjustable) 1.5-2 seconds, just after the first stage burns out. Commercial designs are available for around $90. I only need to build ONE of these andd don't have the programmer so a pic or BASIC STAMP are out. Any ideas or schematics for an analog or simple digital timer for this application?
Depending what you have for a "g" switch, it could be as simple as one that detects the first instance of "0 g" after arming. That's the time of first-stage burnout, and time to light the second stage. No delay required, and no problem if the first stage burns a little bit longer or shorter than expected.
Looks like that's going to fire the second stage at liftoff or immediately when g-switch drops out depending whether is it NO or NC. That circuit produces a pulsewidth of 1.4RC.
When I was a kid, Estes rocket motors were available with an "after-charge", which is basically a hole at the top of the motor that shoots hot gas into the nozzle of the second stage right at burn-out. So, no electronics, batteries, squibs, none of that schtuff was needed.
The idea of a 1.5-2 second timer with batteries and squib and all of that just seems ludicrous on a rocket where the first stage only lasts 1.5-2 seconds.
Long ago I made a 3 stage rocket with those types of motors. Never found the rocket afterward. :( There was a note inside..'If found please call......' Never got a call :(
And that was the last of my rocketery... Electronics looked better as a hobby. Breadboards don't take off and disappear. :P
This brings back memories. I built a crappy home-made two stage rocket with Estes engines and built a simple electronic stager. It was so heavy the first stage only lifted to maybe 40-50 feet on a D engine. It consisted of a 9V battery IIRC, a mechanical microswitch and a simple monostable and SCR firing circuit. The key was to isolate the monostable with a diode-capacitor power supply so the voltage wouldn't drop when the SCR shorted the igniter across the battery. It worked. I'm sure I could get it much lighter nowadays.
Rich Grise wrote in news: snipped-for-privacy@example.net:
And you are no longer a kid. Black powder motors Estes sells are no longer a "kid". G-H-I (or bigger) composite motors having up to a hundred pounds of thrust or more for those few seconds are not "ludicrous". There are no methods to direct-stage a composite motor. The lower stage motor(s) will not have a delay/ejection like black powder motors do. BTW, they are not ignited with a "squib", they are ignited with either an ijniter or an electrical match. In fact, your entire post shows you have no concept whatsoever about the subject.
D from BC wrote in news: snipped-for-privacy@4ax.com:
called "ejection charge". On today's AP-composite motors,such hot gasses will not ignite a second stage,thus you need electronics and better igniters that use more current. also,hybrid motors using Nitrous oxide as the oxidizer must use electronic- actuated chute deployment.
"Model rocketry" has come a long way from the simple Estes motors of the
60's.
People now install loud beepers or RDF xmtrs in them to aid in finding a lost rocket.
Jim Yanik wrote in news:Xns9A9157A6F52DCjyanikkuanet@
64.209.0.84:
I'm not certified either. I have only slightly more than zero money. I'm flying my fleet of re-built rockets until they're broken beyond repair* or lost. Only occasionally do I spring for a pack of black powder motors: mostly I fly with a saved-up selection of 24 and 29mm RMS reloads. Additionally, there is really no location we can fly anything very big in easy driving distance (central Oklahoma). Some folks drive about 100 miles to Sayre,OK to fly "big" stuff. People *have* flown G/H/I (and bigger) stuff on local fields, but it's really a bad idea.
Not right now. The little boy pumping out the sporgeries has decided to give it a break (or got filtered/shut down by his ISP). There is a lot of nonsense bickering and name calling though.
One of my biggest rockets is called "Fat Bastard". It started out as an Estes "Fat Boy". That crashed, and was rebuilt using plywood centering rings. *That* crashed and was rebuilt using ply centering rings punched out to 24mm and ply fins. THAT crashed and was rebuilt using a full-length
24" BT-60 body tube and a 24" "payload" section and fiberglass re-enforcing around aft end of body tube. The next crash/rebuild should be iinteresting...hmmm...carbon fiber?
snipped-for-privacy@ip-64-139-1-69.sjc.megapath.net (Hal Murray) wrote in news:YaGdnYyQXPE7VIfVnZ2dnUVZ snipped-for-privacy@megapath.net:
The problem is that a commercial timer is about the same cost as buying a programmer plus a few chips to play with (I found commercial timers for about $40). Come to think of it, I've got an old, new-in-box 68HC11EVBU I've never used. I suppose the thing to do (were I so inclined) would be to sell this on Ebay and buy the stuff to get started on pic programming.
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