^ Fingertek, support your fellow Canadians.
I use nylon screws, either 2-56 or 4-40, depending on section mass. I always tap the holes as well, even cardboard. Use a little CA (thin) to strengthen the cardboard. I have 20+ flights on some carboard rockets with no shear pin hole distortion. By tapping the holes you can get a snugger fit, which will help with shear behavior. You want fast, brittle fracture, not deformation/stretching of the shear pin. Loose fits can lead to more viscoelastic deformation. I also strongly suggest using 3 to keep the sections straight and prevent off-axis twisting.Great! Just learned of a couple new styles there.
I am located in Canada, so ordering one switch comes to almost $30 USD from any of those sites (due to shipping). Would have to be from an electronics shop (mouser, etc), amazon, ebay.
Also, on a similar subject, would you recommend starting with shear screws or styrene rod to retain the rocket sections before deployment?
Thanks for the suggestions.
Of course, I'm partial to the pull-pin style, but these aren't for every person or every application.
https://www.labratrocketry.com/product-page/pull-pin-switch-kit
I would be more inclined if they made the pull pin where you could hang a "Remove Before Flight" flag on it. What's the point of the pull pin if you can't have the flag?
I use cotter keys because they are easy to put the flag on.
View attachment 417701
I've been making my own screw switches with double sided circuit board, but at that price, I may start buying them.For my next build I'm using these.
https://www.additiveaerospace.com/collections/accessories/products/pcb-screw-switch
Along with this.
https://www.additiveaerospace.com/collections/accessories/products/surface-mount-for-screw-switch
@Handeman I'll be mounting the switch inside my AV bay on the outside wall where the tube band is. The mount comes with different curvatures and gets glued to the AV tube.I've been making my own screw switches with double sided circuit board, but at that price, I may start buying them.
I won't have a use for the surface mount since I always mount my screw switches on the sled. I use a pull pin through the switch band and a screw switch in the lower part of the bay that will be hidden inside the booster BT during flight. The screw switches gives me a way to turn everything off while loading charges, but without the pull pins and flags dangling and getting in the way or getting damaged.
You just need to make sure you turn them on after you put the pull pins in. You tend to remember after you've gotten a large rocket on the pad, pull the pull pin and nothing happens.
@Greg Furtman@Handeman I'll be mounting the switch inside my AV bay on the outside wall where the tube band is. The mount comes with different curvatures and gets glued to the AV tube.
Those are the same switchs Missleworks sells, I love em. I have made a 3D printed screwdriver guide that mounts over them that keeps the screw from being able to unscrew far enough to fall out accidentally and once backed out to the off position friction captures the screw to stop it accidentally vibrating into the on position.I've been making my own screw switches with double sided circuit board, but at that price, I may start buying them.
I won't have a use for the surface mount since I always mount my screw switches on the sled. I use a pull pin through the switch band and a screw switch in the lower part of the bay that will be hidden inside the booster BT during flight. The screw switches gives me a way to turn everything off while loading charges, but without the pull pins and flags dangling and getting in the way or getting damaged.
You just need to make sure you turn them on after you put the pull pins in. You tend to remember after you've gotten a large rocket on the pad, pull the pull pin and nothing happens.
I only use fingertech switches, although I think pull pins are cool can’t wrap my head around how they couldn’t be turned off we g forces. fingertech switches are all but bullet proof.
I don't remember ever hearing about somebody complaining that pull pins failed, so I'm confident that their reliability is at least decent.
A minor drawback of RBF pins is that you usually need to remove them to assemble the e-bay. In this case, you need to be able to disconnect either the battery or the charges until the pin is reinserted to avoid handling live charges during prep.
Reinhard
LOLDoes anybody have reliability concerns with the PCB screw switches? Vibration/backing out while in flight? I'm thinking about using them but I have those concerns.
+1, I have been using the Missleworks type pcb screw switches and other than one where the screw fell out when I unscrewed it too far, no other issues. The fix for the one was just "staking" the end of the screw so it could not back out all the way. On my own 3d printed bays I have a screwdriver guide that fits over the switch so a screwdriver hits the screw first time every time, it also has a tapered lower section that would also keep the screw from possibly backing out and when the switch is open it keeps it from vibrating closed.LOL
(sorry, I realize that is not a helpful reply by itself. but after you get your hands on some and use them in real situations, you will LOL at the concern as well )
+1, I have been using the Missleworks type pcb screw switches and other than one where the screw fell out when I unscrewed it too far, no other issues. The fix for the one was just "staking" the end of the screw so it could not back out all the way. On my own 3d printed bays I have a screwdriver guide that fits over the switch so a screwdriver hits the screw first time every time, it also has a tapered lower section that would also keep the screw from possibly backing out and when the switch is open it keeps it from vibrating closed.
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