what I could have dont different

[karmicavenger]

If you felt the earth shake a little bit on the 4 July it was my beautiful red, white and blue mini magg impacting the ground with incredible force here in the Northeast. First flight on an H242 blue thunder was great. Perfect boost and motor deployment was exactly at apogee. Second flight on a J350 white lightening was excellent as well. Super boost that kept on going. Not so good on the descent, however. This second flight was the maiden voyage with my dual deployment setup. I was using a Perfectflite MAWD that was switched with a push on-push off switch which was accessible via a vent hole in the airframe. I checked and verified 3 times on the rail that all was good. Well, it wasn't and thankfully the ballistic entry didn't harm person or property (except my own). I was told by a fellow rocketeer that more than likely the switch malfunctioned and reset the altimeter. In an effort to learn from this, I ask "what could I have done differently?" I'll start:

1. I could have stayed home and worked on the honey-do list. That would have made my wife happy instead of coming home from the launch to see her there waiting to hear how my beautiful mini-magg that I had been obsessing over flew. :bang:

I'll let you guys come up with the rest.................

You know you are in deep with a streak of bad luck when you're thinking about carrying around your own air horn when you fly.

 

[DAllen]

I hate switches...All of them. Of course, there are going to be a lot of people who disagree but I think I have the fool-proof method that will simplify your life. First, I drill 2 holes - one above the other - that are large enough to fit the switch wire through on the separator ring on the e-bay. Then once everything is wired up I run the switch wire from the alt through the upper of the 2 holes with 2 bare ends. Once the rocket is upright and looks good on the pad and the alt is ready to arm I twist the two bare wire ends and then shove them through the bottom hole. A little tape over the tiny hump o' wire and it ain't goin' anywhere.

Think "twist and tuck" but tucking the loose end of the wire in the second hole. The advantage is that this maintains the simplicity of the twist and tuck method but enables you to easily disarm the alt without taking anything apart. Just pull the little hump of wire out of the 2nd hole and untwist.

[hides behind flame-proof wall]

-Dave

 

[cjl]

Dallen: that method will work, and it does solve my chief complaint about the twist and tuck method (namely, the lack of ability to externally disarm). Some switches work great though. I like the rotary ones from Missile Works. I've been using them for years with perfect success so far.

 

[DAllen]

Dallen: that method will work,

It does work. I've used it successfully on I think about 6 or 7 flights so far including my L2 cert.

 

[Handeman]

I've used twist and tuck on my L2 also. I'm going to go and drill a second hole right now. Great Idea :y:

Why didn't I think of that?

 

[blackjack2564]

I also twist and TAPE.

After twisting wires together I just tape them to the airframe so I can disarm if need be.

The only time I tuck them in, is the occasional mach flight. This is how we did it on the Mega DarkStar also. All electronics were twisted and taped on the O motor rocket, just as in all rockets we fly large or small.

Say what you want it works for me. No connections to reset or solder joints to fail!

I have seen way to many switches cause the death of a rocket. The only one that seem to be immune are the screw and nut switches. But I will still wait and see.

The Missleworks are some of the best, but still depend on the installers soldering skills and correct wire choice.

 

[Rocketman248]

I've used twist and tuck on my L2 also. I'm going to go and drill a second hole right now. Great Idea :y:

Why didn't I think of that?

Same here.

 

[karmicavenger]

Well I guess that settles it...Twist & Tuck is my new mantra. Thanks for the advice.

 

[sylvie369]

Like Jim, I've dropped the "tuck" part. Some of my rockets have a lot of long wires taped to the outside anyway (pull-pins and the like), and other than adding drag, no problem. Being able to easily disarm the altimeter seems worth the additional drag.

I've had switches that treated me well over a lot of launches, and I've had switches that turned up defective the morning of the launch in my last minute tests. I'm getting happier and happier just doing the twist. :roll:
==========
Dave B. - I was in Three Oaks yesterday, by accident. I had no idea it was so close. What a great area.

 

[jderimig]

Well I guess that settles it...Twist & Tuck is my new mantra. Thanks for the advice.

I was told by a fellow rocketeer that more than likely the switch malfunctioned and reset the altimeter. = Wild assed guess...

Hi Pat,

Problem is you might continue to destroy rockets if the switch wasn't your problem....which you have no evidence that it was.

Most altimeters have sufficient power supply capacitance to survive relatively long periods of power 'bounce' interruptions from the switch.

There wasn't probably enough left in the wreckage to determine what the root cause of the failure actually was. But statistically switch failures are not THAT common. Many rocket use all sorts of switches and last time I checked there hasn't been a history of 'rain of destruction' going on at our launches.

Power interruption is a prime source of electronic failure.

Connection failure is much more likely than a component failure (switch, board etc). Examples would be a wire not securely mated to terminal, or a wire breakage because of a nick. Good practice to avoid this is to use stranded wire and NOT to solder tin the wires. That's a common mistake. And give a slight tug on all your wires to make sure that are in grip of your terminals.

Battery connection failure would be next on the list of suspects. Was the battery secure? How was it oriented with respect to the g forces of the rocket? Were there any short hazards (uninsulated wires close to each other)?

The point of this long post is that you had a deployment failure with an unknown cause (unfortunately). Unless you can duplicate this failure on the bench with the switch (if it wasn't destroyed) and the same model altimeter, you are no safer next time by jumping to alternative switch method.

PS. It was a nice flight on the way up anyways.

Edit: My method is a screw down switch. 100% reliable, impossible to open during flight.

 

[5x7]

I used a Featherweight screw switch at NERRF for the first time. I have done in excess of 100 dual deploy flights and this is the best switch I have used so far. I arm it with a small screwdriver through the av bay vent hole.

https://www.featherweightaltimeters.com/Av-Bay_Components.php

 

[Rocketjunkie]

Hi Pat,

Problem is you might continue to destroy rockets if the switch wasn't your problem....which you have no evidence that it was.

Most altimeters have sufficient power supply capacitance to survive relatively long periods of power 'bounce' interruptions from the switch.

He said in the first post that he used a push on push off switch. Only a fairly weak spring is holding the contacts. I feel it is the most likely failure point.

Some altimeters use a capacitor to augment the current to the deployment charge. A momentary (milliseconds) interruption of power will reset them. Others use the capacitor to keep the electronics powered while the battery voltage drops during the ejection event. The MAWD is the former type, a Raven is an example of the latter.

 

[karmicavenger]

He said in the first post that he used a push on push off switch. Only a fairly weak spring is holding the contacts. I feel it is the most likely failure point.

Some altimeters use a capacitor to augment the current to the deployment charge. A momentary (milliseconds) interruption of power will reset them. Others use the capacitor to keep the electronics powered while the battery voltage drops during the ejection event. The MAWD is the former type, a Raven is an example of the latter.

That featherweight screw switch looks great. As John stated in his post it sounds like he uses the same thing or similar and it is "100% reliable". I have learned that "twist and tuck" and "screw switches" are fail-safe. This is good. Now if I can only get the rest of the variables in the equation to be 100% reliable I will be in good shape. BTW I'm particular how I position my batteries in relation to g-forces. Terminals face upward always. Admittedly, there was one more weekness in the system....I used solid wire instead of stranded. I know, I know....BAD. Won't make that mistake again. All is not lost since I am learning and improving. PLUS a new Perfecflite HiAlt is in the mail. Decided not to spend the extra $$ for the MAWD. I'll put that into the 'kitty' for the release of the smaller MARSA4.
It was a great launch and it was really great to meet Rocketjunkie. Maybe we will see you up here in New York again. NYPOWER is right around the corner.

 

[WillMarchant]

You might want to consider using the motor as backup for your apogee event. Set a motor delay that is a few seconds longer than the optimum. If your electronics fail then at least you'll have an apogee event. This may make the difference between a repairable rocket and a complete disaster.

This is also a safety issue as people on the ground will have more time to get out of the way of the descent. A ballistic rocket will come down *fast*.

And there is no shame in putting out a big parachute at the apogee while you're testing (or getting familiar with) new electronics. Just pick a smaller motor (and use the motor ejection as a backup.)

 

[jderimig]

It was a great launch and it was really great to meet Rocketjunkie. Maybe we will see you up here in New York again. NYPOWER is right around the corner.

He said in the first post that he used a push on push off switch. Only a fairly weak spring is holding the contacts. I feel it is the most likely failure point.

I missed the point on push-on-off switches. Rocketjunkie I apologize about the WAG comment, you are correct that is a likely weakness.

The main point I was trying to make it unless you know for sure what the root cause of the failure was, the entire system should be scrutinized. I know Pat will do that.

On battery orientation. If there is a connection defect in the battery g-forces will tend to pull the internal cells away from the terminal in the terminal up configuration. If there is any slop in the internal construction of the battery that could be a bad thing.

Batteries with internally welded tabs and tightly secured against the terminals with a tie-wrap is a good way to go. Batteries secured against the terminals but perpendicular to the g-forces is even better.

 

[sylvie369]

Batteries with internally welded tabs and tightly secured against the terminals with a tie-wrap is a good way to go. Batteries secured against the terminals but perpendicular to the g-forces is even better.

Questions:

1 - By "batteries with internally welded tabs", do you mean "Duracell" (at least when talking about 9V batteries)? Are there other good brands? Am I deluding myself that Duracells are among the internally-welded?

2 - What do you think about mounting the battery securely to the sled, with terminals that move with the battery? That is, rather than having the terminals separately attached to the sled, you have a clip-on terminal that is only firmly attached to the battery?

3 - (Entirely different question) With the featherweight screw switch, you mount that on the sled somehow? And have a vent hole large enough to fit a small screwdriver into? You don't seal over that hole - you just use it as one of the vent holes?

P.S. - I also agree with Will about the motor backup for apogee. I rarely fly motor deploy for HPR, but I also rarely remove or omit the ejection charge. I also second the "use a big chute at apogee" advice for learning a new system. Oh, and I also used solid wire for my first altimeter bay, before I knew better. Open eyebolts, too (doh!). I got very lucky - 35 or so flights on it without any problems. I eventually lost the rocket, but never had a problem with deployment. Done correctly, dual deployment is quite reliable.

 

[jderimig]

Questions:

1 - By "batteries with internally welded tabs", do you mean "Duracell" (at least when talking about 9V batteries)? Are there other good brands? Am I deluding myself that Duracells are among the internally-welded?

I understand Duracell's are welded, I don't use them. I use MAHA 9v rechargeables which I have taken apart to check.

2 - What do you think about mounting the battery securely to the sled, with terminals that move with the battery? That is, rather than having the terminals separately attached to the sled, you have a clip-on terminal that is only firmly attached to the battery?

That should be good also. Examination of what the forces due to acceleration are trying to do will go a long way to getting confidence in the connections. Simply avoid forces that are attempting to disconnect things.

- (Entirely different question) With the featherweight screw switch, you mount that on the sled somehow? And have a vent hole large enough to fit a small screwdriver into? You don't seal over that hole - you just use it as one of the vent holes?

You can do it that way. I like to flush mount a screw switch to the inside of the airframe or coupler tube so that the screw is right at or near the surface of the rocket. Avoids fishing around with a screw driver find the screw.

 

[WillMarchant]

Invest in a decent Voltmeter that will let you test the current sourcing capability of your battery choice. Radio Shack is selling a "29-Range Digital Multimeter Model: 22-813" for $30 that will handle 10 Amps. That is enough to let you perform the MissileWorks recommended test of (very briefly) shorting the 9V disposable battery through the meter to see how much current it will source.

A brand new Duracell will source 6 Amps.

A cheaper battery I tried a couple of years ago would only source 2Amps straight out of the wrapper. This is not enough to pass the MissileWorks test of about 2 Amps.

Check on the web and mail order 20 or 30 Duracells at a time. You can get them for about $1 each that way. Then you have plenty for launches and plenty to use in your household smoke detectors.

 

[karmicavenger]

This was a brand new battery and probably the 15th or so time I have used the MAWD. First time with a push on push off switch. I didn't like the switch but it seemed to be the easiest thing I could access inside the airframe. This was a 4" av bay inside a 5.5" nosecone.

I am considering motor ejection as a backup in future flights. Just seems timing could be difficult to work out.

I'm more thinking about using a 2nd altimeter and going redundant. Perhaps when the smaller MARSA4 comes out. hint That will cause me a lot more questions when the time comes and will have to start a new thread.

After "scrutinizing" the garbage bag of parts, I noticed that all the connections on the broken MAWD were still tight in the terminals. Granted the terminals were about the only thing left on the board. Also, at the crime scene I had quickly noticed that neither charge had gone off. This leads me to believe that the altimeter was reset to off.

In the end it's all about the karma!

 

[mIcahel]

I'm a fan of the switches from newtons 3rd and use a screwdriver through
sampling hole to arm/disarm PF MAWD. 9V holder is also from N3 Rocketry
and gets a zip tie lengthwise.

 

[5x7]

I'm a fan of the switches from newtons 3rd and use a screwdriver through
sampling hole to arm/disarm PF MAWD. 9V holder is also from N3 Rocketry
and gets a zip tie lengthwise.

The disadvantage with the N3 switch is it can break when overtightened, where the featherweight switches tighten down hard. I bought N3 switches and tried them out, I could not really tell when they were tight enough. I did not like them enough to include in an alt bay.

 

[tomar]

Think "twist and tuck" but tucking the loose end of the wire in the second hole. The advantage is that this maintains the simplicity of the twist and tuck method but enables you to easily disarm the alt without taking anything apart. Just pull the little hump of wire out of the 2nd hole and untwist.

Thats' how I operated for years except for my L3 and that's only because I could not get away with it. I embrace screw switches now.

Deployment failures suck. I've never had a deployment failure with electronics.

 

[Adrian A]

3 - (Entirely different question) With the featherweight screw switch, you mount that on the sled somehow? And have a vent hole large enough to fit a small screwdriver into? You don't seal over that hole - you just use it as one of the vent holes?

Yes, you can use the static port hole for arming. The closer you get the switch to the hole, the more you will enjoy using it. It's best if it's right near the surface so you can see it. A good way to do this is to rotate it 90 degrees and mount it along the edge of your sled.

 

[jderimig]

​

Thats' how I operated for years except for my L3 and that's only because I could not get away with it. I embrace screw switches now.

And they are EXTREMELY easy to make if you are on a budget..

1. Get a scrap of a double sided pcb board.
2. Drill a hole.
3. Solder a brass nut to one side.
4. Chamfer the other side of the hole with a drill bit.
5. Solder a wire to each side of the pcb.
6. Insert wide head screw from non-nut side.

Voila.