Screw Switches

The Rocketry Forum

Help Support The Rocketry Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

AlnessW

Well-Known Member
Joined
Oct 6, 2013
Messages
1,221
Reaction score
3
Normally I use push-button switches exclusively in av-bays, but the problem I've been finding is that they just don't fit very well in a 54mm or 75mm coupler. (At least the ones I use.) I am looking to go back to screw switches for their size and reliability, but the problem seems to be sourcing them.

For my 75mm MD rebuild I'm using those Featherweight screw switches:
https://www.featherweightaltimeters.com/Av-Bay_Components.php

But I'd just rather not spend $5 per switch plus shipping if I don't have to, so does anyone know of any cheaper and/or local options? I can seem to find any name-brand hardware or electronics stores that carry anything like this.

I've also heard that those rotating 110V/220V switches work well, but I've never used them before. Any thoughts on those? (Again, mounted inside the airframe.)
 
Missileworks and Landru offer screw switches for $2.95 apiece. They are a bit larger than the Featherweight ones, but are very nicely made.

Some folks make their own - not terribly difficult to do.

Those rotary 110/220 switches are nice, but quite pricey to me. The also take up MUCH more space.


s6
 
Thanks for the link!

Adrian used to have the screw switches at 3 for $10. $5 each is kind of a poke in the eye.

Wildman still has them 3 for 10.

https://www.wildmanrocketry.com/ShowProducts.aspx?Class=534
A poke in the eye indeed - 3 for $10 seems like a much better deal.

Missileworks and Landru offer screw switches for $2.95 apiece. They are a bit larger than the Featherweight ones, but are very nicely made.

Some folks make their own - not terribly difficult to do.

Those rotary 110/220 switches are nice, but quite pricey to me. The also take up MUCH more space.


s6
Wow, I had no idea Missileworks even offered those. Thanks! That's probably my best bet so far. As for making them yourself - an idea I had was to mount a copper or brass strip to each side of my altimeter sled, drill a hole through the assembly, and just run a machine screw through that...

Good advice on the 110V/220V switches.
 
But I'd just rather not spend $5 per switch plus shipping if I don't have to, so does anyone know of any cheaper and/or local options? I can seem to find any name-brand hardware or electronics stores that carry anything like this.

$5 is cheap. Much cheaper than that and you'll be twisting wires together and will be more reliable. Don't cheap out on the switch, otherwise you are asking it to do a lot in an environment it was not designed for.
 
$5 is cheap. Much cheaper than that and you'll be twisting wires together and will be more reliable. Don't cheap out on the switch, otherwise you are asking it to do a lot in an environment it was not designed for.
True, I have seen some "less than robust" switches fail under flight conditions. Your screw switches seem to be very strong as well with the solder, heat-shrink tubing, etc.
 
True, I have seen some "less than robust" switches fail under flight conditions. Your screw switches seem to be very strong as well with the solder, heat-shrink tubing, etc.

Thanks. And the only ones I know of actually subjected to 300+ g's during boost. You get what you pay for.
 
I have never had a binder switch fail but I have had my soldering fail.

All are good switches. I would say Binders are a premium.
 
Note about featherweight switch. I couldn't get a good feel with the phillips head screw and destroyed one on the pad. Over torqued and it breaks. I replace the
screws with a socket head screw and have better luck. (That and a lighter touch with the driver.) Kurt
 
be careful how tight you tighten it - I could see it bend the lexan for me if I went too tight. something like this (you would have to tap and thread yourself) might be better as it has a 'leg' for the far side also: https://www.amazon.com/dp/B000H5VW8C/?tag=skimlinks_replacement-20

[...with edit...]

and I would say something "like that" as the amazon price is relatively expensive after shipping for 4 of them... and you still need to drill / tap...
 
Last edited by a moderator:
Tony,

Thanks for the clarification. It could be easy to make if you have the skill.
 
I made my own screw switches by soldering a brass nut on the back side of a double sided circuit board and use the brass screw to tighten down and contact the other side. You can get the double sided boards and etching materials at Radio Shack or on-line. Since the switch doesn't require any precise etching, just cutting the copper and peeling it off the board works in these cases. If you make your own, you can position the screw and mounting holes however you need.

If you tear down old electronics boards, you can find the double sided boars in some old VCRs, etc. The power supply boards usually have the most copper plate left for reuse. Just cut to size.
 
Interesting ideas here, folks!

Note about featherweight switch. I couldn't get a good feel with the phillips head screw and destroyed one on the pad. Over torqued and it breaks. I replace the
screws with a socket head screw and have better luck. (That and a lighter touch with the driver.) Kurt
What are you saying happened, exactly?

Anyways, I ordered 4 of the Missileworks switches plus some hardware to assist with mounting, etc from McMaster-Carr. That should keep me going for a little while!
 
Thanks. And the only ones I know of actually subjected to 300+ g's during boost. You get what you pay for.

I only see one switch on your site, the arming switch ($8.50). Is that the one that you recommend Mike? I might try it.
 
Note about featherweight switch. I couldn't get a good feel with the phillips head screw and destroyed one on the pad. Over torqued and it breaks. I replace the
screws with a socket head screw and have better luck. (That and a lighter touch with the driver.) Kurt


Strange, I sort of did the same thing but I didn't over torque the screw. I just pushed so hard on the screwdriver I cracked the circuit board. :blush:

I also replaced the screw with a socket head and I built a plastic tapered guide to direct the hex key into the screw.
Av bay back switches.WE.jpg

I attached the guide using the mounting screws for the switch.
Switch detail.WE.jpg
 
I have used the Featherweight screw switches but found them to be too small. Hard to find the tiny Philips head screw in the avbay and have had the soldered nut break away from the pcb foil from over-torqueing, and it doesn't take much. Have also lost screws in transport and had an altimeter self arm in the car. Forgot to remove the battery!

I just got a bunch of larger PCB switches from Landru for only $2.95 each and I think they will be easier to work with and they are more robust than Featherweights. I think I'll put a longer screw in and crimp the end of the threads so it can't back out in transport and can be jammed in the OFF position so it can't self arm. They can be found here: https://www.etsy.com/listing/200819067/pcb-screw-switch?ref=shop_home_active_6
 
I have made my own too, pretty easy- single sided PCB, sketched a semi-circular trace around a hole drilled for a #8 screw, with a matching semi-circle on the other side- slight gap keeping the traces separate. Etched in home brew etchant (muriatic acid and a little h2o2 since I was out of ferric chloride). Epoxied a nut to the back, so when the screw is tightened the head completes the circuit. Am in bed or would post a picture (of the screw switch!). Have only used it to power on an egg timer used to record alt, no deployment, but no issues thus far.
 
When I built my level one rocket a few years ago, I got ambitious and built my own screw type arming switch for under 2 bucks. Attached is the build info.

I built a couple of these and they are sturdy and relatively easy to make.
 
Back
Top