Options for ebay arming mechanism?

Steve Shannon said:

You only need one switch per altimeter. I recommend putting that one switch between the battery and the altimeter because some altimeters include a continuity check on startup which would be fooled by having a switch between the altimeter and the ejection charge.
You must disarm all charges before lowering your rocket in case you have to remove it from the pad without launching it. That’s in NFPA 1127 which is central to the Safety Codes for both Tripoli and NAR. Be sure your design allows for that. Basically you just need to be able to turn the altimeter off (or in your current design interrupt the current that might flow to the ejection charge).


Steve Shannon

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Sheeeeeeeeoooooot!!! Make doubly danged sure you switch off a Galejs MAD unit and let it sit 5 minutes (which I never do) 'cause I turn mine off and gently lift the nosecone and pull the ematch wire. Then it's safe. https://www.aeroconsystems.com/electronics/mad.htm

The Zeptomag unit ( I got a couple of 'em and can vouch for them) are safer https://www.tindie.com/products/ZeptoBit/zeptomag/ and I believe is the only commercially available one as Aerocon stopped selling the kits.
I killed one of mine with a homemade ematch and I'll be danged I found Dr. Galejs from the internet and he himself fixed mine when I sent it to him. Didn't ask for compensation but I dropped a 10 spot in the box.

I was funkily captivated testing the Galejs with an LED and watching it go on by tipping it over. The zeptomag has an onboard LED that will do that and it doesn't need any ematches wired in nor does power go to the terminals for testing. I checked it with
a meter. It activates by acclerometer. If you have a relatively low flier rocket that has the room a MAD unit is great for zipperless deployments. I do try to keep mine pointed straight up or just a hair downwind so if it weathercocks a bit the rocket flies a gentle curve to apogee (well that's what you try to do) for a low velocity deployment. I won't use a MAD with an RF tracker cause I don't want to be stuck testing like crazy to see if Rf dinks with the MAD device but I've flown 'em with the Jolly Logic chute release with no problems. The ASP large WAC Corporal comes with all the parts to make a forward ebay for a MAD unit: https://www.asp-rocketry.com/ecomme...ge-29-38-mm-Version-.cfm?item_id=631&parent=8
I love a two grain 38mm research H "ish" 160 motor I make and use a spring steel clip for retention. Hint: I don't "glue the coupler to the nosecone. I simply use flathead screws and mount the MAD on a piece 'o plywood all press fit. No worries about proper delay and if the rocket has a little more velocity than is desired, using the JLCR cuts down on deployment stress even if it's a bit fast with a nice lower main chute unfurling down lower.



This is an old picture after a chute tangle and the rocket took a hard hit. I did a coupler repair, repaint (nice job) and this was before the Jolly Logic Chute release was even on the scene. I had already removed the noscone off the
coupler assembly. Yes the ASP large WAC comes with that coupler and bulkhead for a "forward" stuffer tube. I thought it was ashame to have that wasted space in there glued to the nosecone and decided to stuff a MAD unit in there. The NC shoulder fits in the coupler tube and the coupler fits in the sustainer hence it can be secured with screws. I did a new harness and different chute protector and have more reliable flights with it now. I use only
one motor in it. My two grain research H160ish motor in an AT case. Gotta mix more of 'em up. Goes out of sight for a brief period if I don't use the longest delay grain (for smoke only) I can find. Kurt

OverTheTop said:

I like pull-pins with RBF tags. Mostly difficult to forget to arm the electronics.

I have tried a lot of things on the way and these I find the most convenient on the launch field.

A couple of other threads have discussed them here:
https://www.rocketryforum.com/showthread.php?143967
https://www.rocketryforum.com/showthread.php?144367

Unless you have super-sized batteries the wifi options are generally too power thirsty for any decent amount of storage or pad time. This could be improved by another switch in series, but I see little point in that for most rockets I build.

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OTT: do you have local Australian source and part numbers for what you use for your pull switches?

I purchase from digikey.com, which are local if you are in Thief River Falls, Minnesota

This is the usual part I get:
https://www.digikey.com/products/en?keywords=sw727-nd


Two 3mm mounting holes are all that's required. I usually make a structure to support the actuation pin using fiberglass G10 sheet. That keeps any stress off the switch. I should do some 3D printed housings one day...

There is another version if you need the one with the leads exiting at right angles to this one. Make sure you order the ones with the contacts NORMALLY CLOSED if you are using them in this pull-pin situation

The advantage of using the switches with the wire leads is that they are sealed against ingress of anything, much better than the terminal versions. We use similar ones to these at work in highly acidic environments and they have proven quite reliable. I have not been let down by one of these yet.

I'm late to this thread with a blatant advertisement, but I offer pull pin switch kits with everything you need (except wire) to add a single or double pull pin switch to your electronics bay. You can read moreand/or order them here: Lab Rat Rocketry Shop

These have proven popular enough to justify larger quantity parts ordering, so I was able to bring the price down a bit.

I was just asked if I knew anything about the switch in the link below. I have never seen this product before. Has anyone looked at it in regards to how relevant it is for rocketry? Thoughts?

https://www.boomarc.com/en/hidden-balance-switch-with-pin-flag

mpitfield said:

I was just asked if I knew anything about the switch in the link below. I have never seen this product before. Has anyone looked at it in regards to how relevant it is for rocketry? Thoughts?

https://www.boomarc.com/en/hidden-balance-switch-with-pin-flag

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For any switch, look at the manufacturer’s data sheet to see if there are shock and vibration ratings. If not, find a different switch.

Electronic switches should have G ratings easily in the hundreds, especially if you solder the wires to the board instead of using screw terminal blocks. The SMT components themselves are typically rated to thousands of G's, it's the solder joints that are most likely to fail. Oversized SMT pads (if hand-soldering) and securing all wires to the sled goes a long way towards preventing that from happening. Conformal coatings for very high-G flights can't hurt, either.

Conformal coatings for very high-G flights can't hurt, either.

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Definitely!

Also securing things like electrolytic capacitors and other large components like terminal blocks to the PCB using something like Loctite 401, with appropriate primer, really adds to the robustness.