Altimeter Switch Mount Question(s)

I have not finished building an avionics bay in a long time. I am close to finishing one, and I have a question regarding some methods I have seen from other fliers; If you mount the switch to the sled, so that the switch comes out when the sled is removed, does the switch access hole become the vent hole for the avionics?

I have always mounted my switches to the airframe, and drilled addition hole for the baro-altimeters. But the wiring is so long, abd has to be stuffed into the bar when the sled is slid in... does this make sense? What I am ultimately getting at, is cutting down on the excess wires that I have to stuff when closing up the avionics.

DRAGON64 said:

I have not finished building an avionics bay in a long time. I am close to finishing one, and I have a question regarding some methods I have seen from other fliers; If you mount the switch to the sled, so that the switch comes out when the sled is removed, does the switch access hole become the vent hole for the avionics?

I have always mounted my switches to the airframe, and drilled addition hole for the baro-altimeters. But the wiring is so long, abd has to be stuffed into the bar when the sled is slid in... does this make sense? What I am ultimately getting at, is cutting down on the excess wires that I have to stuff when closing up the avionics.

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I have used this with good success several times. Kenrico taught me a trick, using a spent 18mm motor cut down and epoxied on the board to move a Schurter switch closer to the inside of the body tube. Keep the hole small enuff and you don't have to root around with your (small) screwdriver to find the slot in the switch. Solder leads to the switch beforehand and file a slot in the bottom of the standoff before you mount it. Add a couple of smaller holes around the circumference to minimize wind effects. Hope this makes sense. There are other options to include a mag switch and the new remote switch from Eggtimer. I'm currently working on one of those.

DRAGON64 said:

I have not finished building an avionics bay in a long time. I am close to finishing one, and I have a question regarding some methods I have seen from other fliers; If you mount the switch to the sled, so that the switch comes out when the sled is removed, does the switch access hole become the vent hole for the avionics?

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Yes. This is the way I like to do it.

Screw switches are mounted on the edge of the board, so that they are only 1-2mm from the vent holes. That way they are very easy to arm, no searching required - holes are small enough that I don't even need to see what I am doing. A bit tough to see in the photo, but they are on the top and bottom edges of the 2 ebays shown. Bonus is these ebays are modular built into 54mm coupler tubes (both a Raven 3 and an RRC2+ in each), and are used in many different rockets by slipping them into 54mm tubes mounted in the couplers of rockets from 54mm - 7.5" diameter.

DRAGON64 said:

I have not finished building an avionics bay in a long time. I am close to finishing one, and I have a question regarding some methods I have seen from other fliers; If you mount the switch to the sled, so that the switch comes out when the sled is removed, does the switch access hole become the vent hole for the avionics?

I have always mounted my switches to the airframe, and drilled addition hole for the baro-altimeters. But the wiring is so long, abd has to be stuffed into the bar when the sled is slid in... does this make sense? What I am ultimately getting at, is cutting down on the excess wires that I have to stuff when closing up the avionics.

Click to expand...

I like the method fyrwyrx mentions with the 18mm motor case, I do something similar by building a wood stand off over the board the get the switch directly below a static port. The switch hole is just a oversized static port at 3/16" and the others are 1/8", it also makes it easy to tell which one has the switch behind it. So the answer to your first question is yes I just use one of the static ports for my switch hole. I wire my igniters directly to the altimeter using a hole drilled in the bulkhead, once the wire is passed thru I seal the hole with a Well Nut which is visible in the third picture just to the right of the Ubolt and all thread nut on the right side. The screw between the legs of the Ubolt is to seal the pilot hole for my circle cutter. As you will notice all wires or items are wired directly to the board so there a no failure points between the igniter and another terminal block. I also cut a slot in the side of the pass thru hole for the wire, which makes getting the well nut out easier. The well nut shown is on its 5th or so flight/ground test.

Interesting switch mount concepts. I could make that work for my switches I guess...

Remember the old Gateway 2000 computers? The towers and desktops all had the lock out switch in the front cover... well, during and after the Y2K scare, I managed to extract all of the switches from the computers that were getting scrapped at my company. I built myself a little stash of the little buggers...



I generally mount these through the airframe, or in my latest build, through the switch band. Here is one of the Gateway 2000 switches in my Excalibur rocket (thru the airframe)...



As you can imagine, wiring gets pretty 'hairy'.

I used a LOC av-bay kit here. It is the 5.5" version, with the coupler stiffy installed. 1/2" holes are drilled through the airframe and coupler. The switches are countersunk into the av-bay. This permits easy switch access from outside the rocket.

rharshberger said:

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Those are great designs. I usually do not use a switch. I may have to try this.

cwbullet said:

Those are great designs. I usually do not use a switch. I may have to try this.

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Thanks Chuck, its a combination of techniques I have gleaned from several well know individuals here on TRF. Reliability, Safety, and Simplicity are foremost to me. There is a variation on the wellnut pass through using a piece of metal with a screw on one end to tighten the strip of metal over the hole, a piece of poster tack adhesive is placed over the wire and pass thru hole then the metal strip is laid over the top and the single screw on the other end is tightened down. As soon as I build one I will post it, its even easier to use than the well nut pass thru.

rharshberger said:

I like the method fyrwyrx mentions with the 18mm motor case, I do something similar by building a wood stand off over the board the get the switch directly below a static port. The switch hole is just a oversized static port at 3/16" and the others are 1/8", it also makes it easy to tell which one has the switch behind it. So the answer to your first question is yes I just use one of the static ports for my switch hole. I wire my igniters directly to the altimeter using a hole drilled in the bulkhead, once the wire is passed thru I seal the hole with a Well Nut which is visible in the third picture just to the right of the Ubolt and all thread nut on the right side. The screw between the legs of the Ubolt is to seal the pilot hole for my circle cutter. As you will notice all wires or items are wired directly to the board so there a no failure points between the igniter and another terminal block. I also cut a slot in the side of the pass thru hole for the wire, which makes getting the well nut out easier. The well nut shown is on its 5th or so flight/ground test.

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Nice clean, neat build....
Really nice work...
This was to be my next evolutionary step with my av bays
but I tried and like the Eggtimer electronic switch,, so this won't be necessary...
Great work though...

Teddy

onebadhawk said:

Nice clean, neat build....
Really nice work...
This was to be my next evolutionary step with my av bays
but I tried and like the Eggtimer electronic switch,, so this won't be necessary...
Great work though...

Teddy

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Thanks Teddy, looking forward to the day I acquire a couple of your works of art, your recovery harnesses are a form of art.

That's awfully nice of you to say Rich...
I see from those pic's we're similar with working on something...
I'm not saying it's good or bad,, right or wrong...
Some folks may say we take too long,,
That's fine,, to each his own,, nobody's right or wrong,, just different...
I like working slowly and being meticulous...
I find satisfaction in that...
I think you do too..

Teddy

This thread was originally started because of a current dilemma with a 4" avionics that I am putting the finishing touches on:

https://www.rocketryforum.com/showt...ecting-The-Black-Dahlia&p=1474736#post1474736

But much of what I glean from everyone's input will help with next project, which will utilize the 76mm sleds from Additive Aerospace (Landru). Here you can see that the switch mount is already printed onto the sled... On this project I will probably go away from the old Gateway 2000 switch, and pick up some switches from Dog House Rocketry.

The Landru sleds are cool. He sells a screw switch for them- check it out.

A probably dumb question - with the switch fixed to the sled, what method do you use to set the "clocking" of the sled when you're buttoning everything up to make sure the switch ends up under the hole? Just eyeball it? Some sort of key slot? You could permanently affix one alt bay cap, but that would make it hard to service anything on that end, especially in small diameter bays. Or am I overthinking this and it's not really an issue?

Mark is right..
The wedge shape on Andrew's sleds isn't just for a rotary switch in the center hole..
It is also printed to accept a screw type switch on the angled face..
Either way you use it the switch will be closer to the coupler wall then
if it was just mounted flat on a ply sled like I've always done in the past...
Either of these methods should be a fairly easy and effective solution...

Oberon,,
You're not overthinking at all...
You'll have greater success because your thinking things through before constructing..
One of the vent holes is perfectly over the switch and is large enough to get the screwdriver into to work the switch...
I use the corner of a file to make witness marks on the av bay bulkhead that the sled is mounted on...
A silver sharpie and a Estes fin guide makes witness marks on the outside of the coupler,, line those up when you assemble them in the field..
The file makes witness marks on the cap / av bay bulkhead,, so you know which way to put that on...
And the corner of the file again to make witness marks on the insde edge of the booster and the inside edge of the payload section
so you know which way the coupler / av bay goes into the booster and then which way the payload section slides onto the coupler...

Teddy

Oberon said:

A probably dumb question - with the switch fixed to the sled, what method do you use to set the "clocking" of the sled when you're buttoning everything up to make sure the switch ends up under the hole? Just eyeball it? Some sort of key slot? You could permanently affix one alt bay cap, but that would make it hard to service anything on that end, especially in small diameter bays. Or am I overthinking this and it's not really an issue?

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The sled is adjustable along the lenghth of the aluminum rods usually via a shim glued to the botton of the sled that indexes it to one end, then the sled is locked in place by two nuts at the top.
For making sure the switch is lined up circumference wise I draw a black line with a sharpie down the exterior of the AvBay and both bulkheads.

rharshberger said:

Thanks Chuck, its a combination of techniques I have gleaned from several well know individuals here on TRF. Reliability, Safety, and Simplicity are foremost to me. There is a variation on the wellnut pass through using a piece of metal with a screw on one end to tighten the strip of metal over the hole, a piece of poster tack adhesive is placed over the wire and pass thru hole then the metal strip is laid over the top and the single screw on the other end is tightened down. As soon as I build one I will post it, its even easier to use than the well nut pass thru.

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Can you post a picture of the parts when you do a build thread?

cwbullet said:

Can you post a picture of the parts when you do a build thread?

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Will do.

I always mount my switch so that it's under a vent hole. Sometimes I have to line up more than one. That's always fun.

Man is that beautiful Chris....
That's not fair,, you're a machinist....lol...
Lemme see some pic's of that sled...

Teddy

ChrisAttebery said:

I always mount my switch so that it's under a vent hole. Sometimes I have to line up more than one. That's always fun.

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I saw this in one of your threads previously. This is a great space saving idea for two switches. Any plans to sell something to fit into a minimum diameter 54 mm sled?

markkoelsch said:

The Landru sleds are cool. He sells a screw switch for them- check it out.

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The Landru sleds are great. But the ones for smaller diameter rockets only hold one altimeter and switch. It would be niice to see something that holds two. Or possibly some stand alone switch only options for mounting into sleds. The sleds are nice enough that I have thought about putting one alt. and switch in a high performance rocket, but I am a bit nervous about that.

cwbullet said:

Those are great designs. I usually do not use a switch. I may have to try this.

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That is a nice design. Certainly makes a person go hmmmm....

ChrisAttebery said:

I always mount my switch so that it's under a vent hole. Sometimes I have to line up more than one. That's always fun.

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Ather great method. Are you planning to make these?

Thanks Teddy. Believe it or not I'm not a machinist. It's just another hobby.

There are more pictures in the relevant threads. Let me know if there is something else you'd like to see.

https://www.rocketryforum.com/showthread.php?122968-The-City-Slicker-was-The-Space-Cowboy-rides-again&p=1472339#post1472339

https://www.rocketryforum.com/showthread.php?123926-Wildman-3-quot-Saab-RB-05A&p=1469396#post1469396

onebadhawk said:

Man is that beautiful Chris....
That's not fair,, you're a machinist....lol...
Lemme see some pic's of that sled...

Teddy

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ChrisAttebery said:

Thanks Teddy. Believe it or not I'm not a machinist. It's just another hobby.

There are more pictures in the relevant threads. Let me know if there is something else you'd like to see.

https://www.rocketryforum.com/showthread.php?122968-The-City-Slicker-was-The-Space-Cowboy-rides-again&p=1472339#post1472339

https://www.rocketryforum.com/showthread.php?123926-Wildman-3-quot-Saab-RB-05A&p=1469396#post1469396

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Hey,, hey,, hey,,,
Rod coups as standoffs so you can get a board up off the sled then sneak something else / another board under it.......
Wwwoooohhhhhh......
How slick is that........

Chris I'm sorry man...
You're just too good of a man to lie too...
That is getting soooo stolen it's just ridiculous......
I'm gonna remember that one fer sure.....
Talk about art,,, that's art right there....
Really nice work Chris...
A hobbyist huh...

Teddy

This is what I did on my Fletch Rocket (Darkstar Jr.):

I used a Featherweight screw switch and attached it directly to the switch band on the coupler with two 2-56 screws. I then drilled a hole in the middle for access the screw and for venting. When I fly the rocket it is incredibly quick and easy when the rocket is on the rail.

Johnnie, I just got an RRC2+, and the 38mm sled from Jim, which I believe is printed by Landru. I'll definitely be buying more of his sleds if/when the need comes.

David

astrowolf67 said:

Johnnie, I just got an RRC2+, and the 38mm sled from Jim, which I believe is printed by Landru. I'll definitely be buying more of his sleds if/when the need comes.

David

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I have two of Landru's sleds; a 76mm and a 54mm, neither of which I have pressed into service yet, I have plans for them though.

To keep from drilling my airframe with large switch mount holes, I am going to see about adding 2 screw switches to my current design, and access them through vent holes.