MADCOW 4" FRENZY CARDBOARD ROCKET... A BUILD THREAD #1

watermelonman said:

Get an I405; they are amazing.

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Loki I405 works well on the simulation, for my DX3. Comfortable altitude, not too awfully high, within the specified impulse limits for L1. Not a bad choice! "Thanks!"

Redundant/Backup deployment systems...???
This might sound like a silly question, but I have to ask it.
Should I use one ejection igniter wired to both altimeters in a single cannon, or use 'two' igniters wired parallel to both altimeters... 'or'...
should I use 'two' cannons, each one hooked up to its own altimeter (single, or dual igniter question still stands) for 100% isolation of the two systems?
I'm afraid of a 'chain-fire' with two cannons, where both cannons will possibly fire when one cannon goes off. Twice the recommended 'charge' for deployment.
What's the best way to approach this redundancy thing in deployment operations?

I have always used 2 complete systems. The odds of a chain fire is very small. Even the same brand altimeters will not fire at the same time. It just my thoughts if you want redundancy than 2 altimeters 2 charges is needed. 2 for each event. You can also just go with 1 altimeter and use motor ejection for 1st event back up.

TMJ said:

Redundant/Backup deployment systems...???
This might sound like a silly question, but I have to ask it.
Should I use one ejection igniter wired to both altimeters in a single cannon, or use 'two' igniters wired parallel to both altimeters... 'or'...
should I use 'two' cannons, each one hooked up to its own altimeter (single, or dual igniter question still stands) for 100% isolation of the two systems?
I'm afraid of a 'chain-fire' with two cannons, where both cannons will possibly fire when one cannon goes off. Twice the recommended 'charge' for deployment.
What's the best way to approach this redundancy thing in deployment operations?

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The most common solution is to use slightly different settings for deployment. Say, 800 feet for main, and 750 feet main for the second computer. Most allow for an apogee delay as well.

Be careful in that certain brands build in an apogee delay while others do not. The ones I have seen call that "nose-over" instead of apogee. So if I set an Eggtimer to +0 and an SCF to +1, they would both be set the same.

Of course as crossfire says it is extremely unlikely to get simultaneous firings even out of the same brands and settings.

Thanks guys. I know to set the altimeters at different altitudes. That's not my question. Perhaps I phrased it wrong. I was wondering if using 'two' BP cannons, each cannon hooked up to its own, separate altimeter would cause problems. For example...Primary altimeter fires as advertised, no problem. Would the hot gasses produced from the primary charge possibly set off the 'backup' charge as well? Much like an old black powder revolver that has not been well sealed, or sloppily reloaded. Fire one shot and three other chambers go off all at the same time... 'Chain Fire'! I've never had a chain fire in any of my BP revolvers, but there is always the chance. I guess I 'could' seal the ejection cannons like I seal my revolvers, with tight fitting wads and a wax cap to seal to help insure that only 'one' chamber fires, not two... but don't know. Being curious here.

Real tough and unlikely for that to happen if you have any reasonable gap between the charges.

...

The primary certainly can fire the backup, happened to me in my testing. I didn't use enough tape / dog barf covering the backup. So I decided to "pack" dog barf on top of the charges and tape with electrical tape - unfortunately the charge wells were plastic, so I created so much resistance that the next time the primary charge well turned into shrapnel, not good.
So yes, keep the primary and backup on opposite sides, don't "pack" the dog barf, just lightly push it in and use sufficient masking tape so none of those burning gases can't get to the backup charge and test a couple times.

I don't use 2 igniters per charge, I just measure the resistance of the igniter prior to installing them, but I may use 2 igniters on my L3 project just to make me feel better (the laundry MUST come out)!

I use a male plug on my primary and female on backup so I can't plug then in wrong during assembly since the backup charge may be 10-25% more BP. Also different colored wires.

The only time I use 2 matches for one charge....when there is only 1 altimeter.

8 grams bp , 2 on same bulk plate in finger tips, never had one charge concussion or sparks fire the other. Never in hundreds of sizes & flights. If made like shown so many times.

Just make charge that way and drop in your canisters.

Whatever you decide, be consistent every time till you perfect your style.

'Dog Barf'?.. Hmm...??? I don't have a dog, however. I do have a cat, but 'her' barf looks a bit sloppy to pack on top of a BP charge! Okay guys, just what is 'dog-barf'? LOL

Dog Barf as used in rocketry is cellulose insulation made from recycled paper(treated to be fire resistant), it breaks down rapidly when exposed to the elements so it doesn't leave an unsightly mess of things. can usually be found at Home despot, while a bale isn't over expensive...you may be able to get a deal on a broken bale.
Rex

Rex R said:

Dog Barf as used in rocketry is cellulose insulation made from recycled paper(treated to be fire resistant), it breaks down rapidly when exposed to the elements so it doesn't leave an unsightly mess of things. can usually be found at Home despot, while a bale isn't over expensive...you may be able to get a deal on a broken bale.
Rex

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Thank you, sir! Gotta go to home depot for loctite and primer this weekend. I'll put some dog barf on my shopping list too!

blackjack2564 said:

The only time I use 2 matches for one charge....when there is only 1 altimeter.

8 grams bp , 2 on same bulk plate in finger tips, never had one charge concussion or sparks fire the other. Never in hundreds of sizes & flights. If made like shown so many times.

Just make charge that way and drop in your canisters.

Whatever you decide, be consistent every time till you perfect your style.

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Thanks, Jim. I have the gloves, ready to cut the tips!

Nick@JET said:

The primary certainly can fire the backup, happened to me in my testing. I didn't use enough tape / dog barf covering the backup. So I decided to "pack" dog barf on top of the charges and tape with electrical tape - unfortunately the charge wells were plastic, so I created so much resistance that the next time the primary charge well turned into shrapnel, not good.
So yes, keep the primary and backup on opposite sides, don't "pack" the dog barf, just lightly push it in and use sufficient masking tape so none of those burning gases can't get to the backup charge and test a couple times.

I don't use 2 igniters per charge, I just measure the resistance of the igniter prior to installing them, but I may use 2 igniters on my L3 project just to make me feel better (the laundry MUST come out)!

I use a male plug on my primary and female on backup so I can't plug then in wrong during assembly since the backup charge may be 10-25% more BP. Also different colored wires.

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Educate me, please. Why would your backup charges be 10%-25% more BP than your 'primary' charges?

TMJ said:

Educate me, please. Why would your backup charges be 10%-25% more BP than your 'primary' charges?

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Just in case you accidentally packed the chute too tightly in the tube or whatever, you have a second chance of blow it out or blow it up!

rharshberger said:

Just in case you accidentally packed the chute too tightly in the tube or whatever, you have a second chance of blow it out or blow it up!

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"Ahhhh, okay!" That actually makes a lot of sense! Not only redundant systems, but also a second harder 'kick'... just in case the first 'belch' wasn't strong enough to properly 'hang out the laundry'! I never thought of that. Nice little bit of 'great' info!

I'm trying to get two rockets ready for L1 and L2 certifications at Airfest. I'm running low on time, so I need to get 'down and dirty' on the completion of my L1 Super DX3 and the L2 Frenzy attached to this thread. I'm not wanting to cut any corners, but I do need to save as much time/work as possible. I've asked about nose cone retention before, and have received numerous good responses involving shear pins, tape to tighten things up, metal to cleanly shear the pins, etc. I'm now thinking about simply having my nose fit tightly, without shear pins. I'm being told that if I can pick the rocket up, by the nose, and the nose cone stays on 'I'm good to go'. What about the weight of the rocket(s). Does weight really matter, or is this just a good 'rule of thumb' to 'safely' gauge by?

how about this to make things easier, tape the nose on. when I did my ground test I used two strips of blue painters tape for delicate surfaces(4" x 0.5", 2" on each section) to hold the av-bay & booster sections together, booster section weighs 3.75 pounds...and could lift it with the av-bay, when I fired the drogue charge the tape sheered nicely. the rule of thumb is, tight enough to lift the weight of the rocket(below the nose) without separating, if it takes more than twice the weight of the rocket it is probably to tight.
Rex

The stock Madcow sleds are too small for redundant systems. Not enough room to cram everything needed where it needs to go. I was planning on building a new 'larger' sled, from scratch, but wouldn't you know it? My local Home Depot had nothing in 1/4" plywood, except for 'finish' plywood in 4'X8' sheets. High dollar stuff and I only need a few square inches. "No, no, no!" Not going 'that' route! I bought some 1/4" thick 'paint mixing sticks', instead... and decided to expand upon my small lot of sled with those paint sticks. As it turns out, I think that this might be a blessing in disguise. I cannot mount both altimeters and both batteries on the face of the sled. Best I can do is mount the two altimeters and 'one' battery on the face. The second battery must be mounted on the underside of the sled. This is where the 'blessing' comes in. I'll now be somewhat evenly distributing the weight of the batteries on opposite sides of the centerline of the rocket rather than having 'ALL' of the weight/mass on one side of that centerline. Equal/opposite weight distribution = centerline 'balance'!
I'm sure that there are better ways to pack a bunch of stuff on a small sled, but I'm out of time. Airfest is just 'round the corner and I need to simply "Git 'er Done!"
This battery setup is as strong as a tank and was actually quite easy to do via paint mixing sticks and epoxy. "Them batteries ain't going nowhere, nor will the connections come loose!"

This is the 'business' side of the sled:


This is the 'underside' of the sled housing the second battery:


Side View of Sled Arrangement:

sled looks fairly neat...which way is aft? most folks like to orient the batteries so that on take off the mass of the battery pushes against the battery electrical connector.
Rex

Rex R said:

sled looks fairly neat...which way is aft? most folks like to orient the batteries so that on take off the mass of the battery pushes against the battery electrical connector.
Rex

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Rex, that's exactly how I have the 'primary' battery oriented. The backup battery, on the underside of the sled, is facing the opposite direction. That's why I 'trapped' the backup system battery and its connector the way that I did. It will not come loose. Neither one of the connections, primary or backup, will be able to lose their connections via positive G's, negative G's, nor hard jolts either way! :wink:

The battery leads will be cut rather short, just long enough to allow battery replacement without pulling any leads out from the altimeter terminals. The altimeters, themselves, are reversed from each other, on the sled. Battery connections are on opposite ends of each altimeter. This allows minimal wire length to each altimeter, from each battery. My previous post showing the layout of the sled and the battery positions shows why I orientated the altimeters and batteries as I did. The quick disconnects will be for the rotary power switches needed to breathe electrical life into the altimeters. My 'next' step will be to install my deployment BP cannons and then wire 'those' components up, also...

Power switches soldered, for two separate 'redundant' av-bays (two rockets). I'll add heat shrink material to the solder connections tomorrow. For now... gotta whip up some grub for supper!

Everything is hooked up and both altimeters are working as advertised!



Electronics stuffed inside the av-bay. Everything fits nicely. Altimeters can easily be heard 'beeping' with the av-bay closed. Now I need to trim the sleds' all thread rails to a shorter length to prevent snagging the recovery gear, remove the altimeters/power switches and get ready for paint...

Looking good! I love to hear the beeps in the AV Bay, means the flight is getting closer

Loki Cases just arrived. "WooHoo!" One is a 38/480 for my L1 DX3, the other is a 54/1200 for this L2 Frenzy.


Now... "How can I get a good balance on these two rockets with just empty cases?" Hmmm???

Nick@JET said:

Looking good! I love to hear the beeps in the AV Bay, means the flight is getting closer

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I really like hearing those beeps, too. It means that I hooked everything up correctly, the 'first' time!

When I first started this Frenzy build, as well as the DX3.. I was not aware of retaining rings, etc.. I simply saw a few images of how folks were holding their motors in place, and the below photo shows what I went with. I know how to make some really good retention clips that will work 'great' with this 3 bolt system, however. Before I fire up the ol' milling machine and start whittling away at some aluminum... do any of you guys have a simpler solution that will work with what I've got going on here?

Back to post #296 on this thread. Is it possible for me to balance these two rockets with nothing but empty cases, if I know what loads will be used in them? I'd like to do this now, rather than be pouring epoxy and lead into their noses while at the field, in Kansas. Maybe Scott, from Loki, could tell me the weight of each Bates grain and the length. I could make dummy grain weights to distribute the same weight along the inside of the cases, just as it would be with a real load? :confused2: Any suggestions?

A seriously cluttered and messy work area including two certification rockets ready for paint, motor retention and balance. I'll clean up later. No time for 'house-keeping' right now. Gotta 'GO,GO,GO'!