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designed and printed sled for RRC3 and screw switches

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Most excellent. I'm taking it that you have additional holes in the coupler instead of going through the vent holes to get to the screw switches? I wish I had the skills, would be mega cool to have a sled that had the screw switch pads at 60 degree angles so that they lined up with 2 of the 3 vent holes of a 3 fin rocket in the switch band, probably placed about mid point on the sled.
 
Ya mean like this.
Slotted sled with hacksaw & slid vent band on from smaller airframe.
Placed into position, then reached trough vent holes, and marked for screw switch positions.

Mounted and done....no measuring etc. AND ya save space mounting under it!
This had Missleworks GPS & RRC3 alongside Strato CF 9v.battery on one side and 2 lipo's stacked on other in battery box

This from 4in Punisher using 3in. vent band cut from scrap tubing.

DSCN5501.jpg DSCN5509.jpg DSCN5511.jpg DSCN5527.jpg
 
Does anyone use DPDT switches? It seems like that might be an interesting way to simultaneously activate a charge and break a safety shunt.
 
Then the follow-up question...do you have a link to the switch that you used?
 
Like many of you, I have used most of the switches presented in this thread. My favorite (except for the cost!) is the Featherweight magnetic switch. But I've used dozens of the green screw switches like the ones that Aerocon sells. However I bought mine from a electronics surplus place (Electronics Goldmine) years ago for a few cents each. (I recall I bought 100 and now I wish I had bought 1000!) Bulletproof and take up very little room. Here's a couple that a friend embedded in a screw-in aluminum base. Almost always I use the altimeter vent hole to arm the switch.


Tony

with and without screw:
screw-switches.jpg
 
Then the follow-up question...do you have a link to the switch that you used?

I don’t. That was 14 or 15 years ago and I bought the switches from Radio Shack. Since then I’ve become picky about switches. Here’s what I would recommend now:
https://www.nkkswitches.com/pdf/cs.pdf

Added: Now, I don’t usually add switches on the charges. I just use one SPST power switch for each device. If I were staging, I probably would add a DPDT switch for the sustainer ignition.
 
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I bought a bunch of these mini switches when PML was selling them years ago. Very solid when slide to off or on.
I can reach both of them easily through the vent hole with an ink pen.
Never had one fail.1243.jpeg
 
I bought a bunch of these mini switches when PML was selling them years ago. Very solid when slide to off or on.
I can reach both of them easily through the vent hole with an ink pen.
Never had one fail.View attachment 382043

I’m still using some of those as well. According to PML they are rated at 50 gees. I’ve not had one fail either.
 
I’m still using some of those as well. According to PML they are rated at 50 gees. I’ve not had one fail either.
My last Patriot came down only on the small drogue. Every section came down horizontially on to some hard, packed ground. Every one badly damaged. Inside my GLR aluminum av bay, the g forces broke the printed sleds in half, batteries popped out and dented plus the rods were bent. The sleds were only hanging on by the Perfectflite screws. When I attempted to replay the stats, both switches and alts were NOT damaged, audio readouts were perfect for both.20190413_214804.jpeg
 
My last Patriot came down only on the small drogue. Every section came down horizontially on to some hard, packed ground. Every one badly damaged. Inside my GLR aluminum av bay, the g forces broke the printed sleds in half, batteries popped out and dented plus the rods were bent. The sleds were only hanging on by the Perfectflite screws. When I attempted to replay the stats, both switches and alts were NOT damaged, audio readouts were perfect for both.

I'm still using a Perfectflite HiALt45 that survived a lawn dart at 300 mph. The ply board broke at the battery which was on the opposite side of the board from the altimeter. The 9V battery was pour out of the remains in a dozen pieces.
 
I'm still using a Perfectflite HiALt45 that survived a lawn dart at 300 mph. The ply board broke at the battery which was on the opposite side of the board from the altimeter. The 9V battery was pour out of the remains in a dozen pieces.
After I saw both of mine were 100% I went out and bought 2 lotto tickets!
 
Wow, what a great thread! Got some really great ideas, especially using recessed charge wells to save space on a 4" rocket I am working on. I launch out of towers a lot and it never occurred to me that there could be a magnetized component on the tower that could kill the mag switch. My new tower is all aluminum but still, a very good point to know. Thanks to the OP for starting the thread.


Tony
 
Here is my version of the screw switch and ebay. It fits inside a 54mm coupler. It is made from a sandwich of single sided PCB and 3D printed PLA. It is made tall enough to place the switch just beneath the body of the rocket to make it easy to reach with a screw driver. I used copper foil for the connections from top to bottom of the stack. During assembly I can adjust the friction on the screw so that it turns easily with a screw driver but wont turn due to vibration.
upload_2019-5-7_9-27-41.png

The top view of the rest of the ebay. There is a cut out area underneath each altimeter to allow for the components on the bottom side of the PCB. The board are spaced off the surface of the sled by a flat washer to allow air flow.

upload_2019-5-7_9-32-23.png

The bottom of the ebay. I don't like the idea of putting tie wraps around LiPo batteries to hold them in place so I created a well with a cover to hold mine in place. The SL-100 is powered by two batteries wired in series. Each battery has a plug so I can just unplug them to recharge them.
upload_2019-5-7_9-35-8.png

The ebay has survived several hard landings with no ill effects. Not the lightest way to build it but it works for me.
 
"so is there a nut soldered to the bottom pcb and the screw contacts the top pcb when tightened?"

Yes. The copper foil just connects the bottom foil to the top side so that both wires come off the top side.
 
Should also point out that I don't use a switch band with this configuration. There is one switch hole in the upper body and one in the booster section. I use three vent holes arrayed around the upper section near the top of the ebay. For flight I place a small piece of electrical tape over the switch holes so the ebay can only breath through the vent holes. I have left the tape off a few times to see if it made a difference. If there was any difference it was so small that I didn't notice it.
 
"so is there a nut soldered to the bottom pcb and the screw contacts the top pcb when tightened?"

Yes. The copper foil just connects the bottom foil to the top side so that both wires come off the top side.

That’s pretty neat. Do you check the foil for cracks before flight? In the photo it looks like one may be starting. I would be tempted to use copper braid instead of foil.
 
I've used apogee push switches on mid power rockets well enough, but for my L2 I used these flat rocker switches
They're not tiny, but they're solid and don't have much unsupported mass susceptible to g-loading.

Only good view of them in use I have at hand is from laying out the ebay on Long Tom

61boyCMYegL._SL1000_.jpg
20180624_231209-jpg.356456
 
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