How do you mount your altimeter?

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Ccolvin968

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I'm just curious if there are different ways?
Do I have to mount them directly to the sled?
Or can I build little posts to mount them on?
The way mine was built, it won't sit flat on the sled without posts.
Also, how do you attach your deployment wires to your charge?
Clips or just twist them up with a little tape?
I'm working on my first DD rocket right now, so I have lots of questions.
Any ideas or help is appreciated.
 

markkoelsch

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I use broaching nuts on the underside of the sled. Then nylon spacers between the altimeter and the sled.
 

ttabbal

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Most of the altimeters need standoffs. New ones often come with them, but it's pretty easy to get them online and even locally in some cases. #4 is usually a good size for most altimeters. Maybe 3mm if you prefer metric.

Deployment charges are usually triggered by e-matches. I usually run the wire inside the av-bay and screw it to the terminals. I often see people put terminal blocks on the outside bulkhead, permanently wired to the altimeter, and connect the charges that way. That's nice as it's easier to seal the av-bay when you do that. It also leads to cleaner wiring in most cases.

Twist and tape will work, till it doesn't. I have done it, but I don't recommend it.
 

Ccolvin968

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Good to know.
It's crazy. I didn't even think about screwing them straight into the board. Haha.
I'm making this way more complicated than it needs to be.
 

jcamhale

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I use the standoffs available from Perfectflite (Link). For all of my DD wiring I use terminal blocks on the bulkheads. I originally bought mine from Doghouse Rocketry, but they've been bought out by another company.
 

rharshberger

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I'm just curious if there are different ways? Lots


Do I have to mount them directly to the sled? Yes, usually with T-nuts epoxied on the back side of the sled then screws with nylon washers (under screw heads) and nylon standoffs between board and sled (nylon washers may work here too. Some like the Quark in small rockets I attach with double stick mounting tape.

Or can I build little posts to mount them on? Sure, you could if you want to.

The way mine was built, it won't sit flat on the sled without posts. This is not unusual, but if there are no components on the back of the board servo/mounting tape combined with a zip tie can do the job or you can use the aforementioned stand-offs.

Also, how do you attach your deployment wires to your charge? I wire ALL my deployment igniters directly to the altimeter whether its via terminal blocks on the altimeter or wire wrapping posts on the kit built altimeters, I also buy the deployment igniters with wires long enough to reach usually that mean 36" leads or for smaller rockets 12" leads. I don't use terminal blocks on the bulkheads as they add one more point of failure IMO by creating yet another connection. The wires pass through a hole in the bulkhead that is either sealed with a rubber well nut or poster tack putty, see pictures below, both work equally well. Yes I do have to take my Av-Bay completely apart to prepare it for a second flight but thats okay, I have to change batteries anyways.

Clips or just twist them up with a little tape? Deployment igniters or ON/OFF? If its on/off then I have used twist and tape but I prefer screw switches. If its for the deployment ematches nothing but solid connections and twisting together the wires doesn't count to me as a solid connection.

I'm working on my first DD rocket right now, so I have lots of questions.
Any ideas or help is appreciated. Keep asking questions!


The rubber well nuts are visible on each bulkhead (a black ring around a button head screw, I cut a small notch in the side of the hole for the well nut for the wire to pass through once the well nut is compressed by the screw everything is tightly sealed. The gray charge wells were a failed experiment, they are made of 1" pulltruded FG rod (used in electrical work), they came apart under the force of a 4.5 gram charge of BP (thank goodness for the test flight since it was my L3 rocket).


EggtimerQuarkWireWrap.jpg


EggtimerQuarkWireWrap4.jpg


L3Build119.jpg


L3Build117.jpg


L3Build133.jpg


AvBay2.jpg


FrenzyXLAvBayLid.jpg
 

KenRico

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I use the standoffs available from Perfectflite (Link). For all of my DD wiring I use terminal blocks on the bulkheads. I originally bought mine from Doghouse Rocketry, but they've been bought out by another company.
The terminal blocks from doghouse are phenomenal compared to the normal ones sold .. when opening the terminals there almost feels to be a stop..the others dont and i often lost the screws in those. Also the other were phillips and can be stripped .. the doghouse ones are slot driver .

I hope the new doghouse peeps continue to source the better product .

Anyhow have gone through my own progressions on altimeter mounting. 1st mounted raven with round nylon spacer , screw threw sled and #2 nut on back with little washer. Although retained well had many leetle parts drop when removing altimeter.

So on next sleds with RRC3 took some scrap luan plywood and pressed in some tNutz 4/40 and glued to bottom of sled while mounting. When screw removed no dropped leetle washer or nut... only round nylon spacers.

Wayco had been using the metal standoffs that looked like motherboard standoffs ..and was going to use that with a paper washer under the altimeter on sled 3.0 but noticed there were nylon 4/40 1/4 inch standoffs male / female. They actually flex a bit if the mounting hole is off a bit and still allow the screw to drive in and seat without cross threading .

Now using the nylon standoffs were mainly to eliminate the loose bits in the field .. but has simplified the mounting process.

Kenny

20160328_091122.jpg


20170101_175950.jpg
 
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Ccolvin968

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What are the wire wrap posts made from?
Is it something I buy or something I have laying around?
My altimeter is an Eggtimer Classic.
 

Lowpuller

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I mount mine on little short pieces of rubber tubing, this provides vibration isolation and a little shock absorption.

You can kind of see it here.

ImageUploadedByRocketry Forum1483312436.255539.jpg
 

rharshberger

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What are the wire wrap posts made from?
Is it something I buy or something I have laying around?
My altimeter is an Eggtimer Classic.
I make my wire wrap posts from old PC board connectors, real wire wrap posts are available via electronics parts vendors, but the square posts from old computer board ribbon cable connectors seem to work as well and I have yet to have one come loose. I just snip them off the board under the plastic, you can also use the header pins like what Cris sends with his altimeters they are the same thing. Some wire wrap tools won't fit the heavier 24gauge wire on ematches, some will.
The altimeter with wire wrap posts was modded to make it as short as possible for a 24mm DD project, no part is taller than the buzzer or the transistors.
 
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Ccolvin968

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There's s tool for wire wrapping too??
Lowpuller, that's a great idea!
Dixon, I'll probably pick those up. Thanks!
 

OverTheTop

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I always use spacers on the screws. If I can't find the supplied ones, and can't be bothered turning some up on the lathe, I just cut short lengths of plastic pneumatic tubing with a scalpel to the right length.
 

rharshberger

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There's s tool for wire wrapping too??
Lowpuller, that's a great idea!
Dixon, I'll probably pick those up. Thanks!
Yep it looks like this, the hole in the center of the tip goes over the post, and there is another hole inline with the slot just above the center hole. Inside the handle is a wire stripper (at least on my tool, which is like the one on the left). Literally a wire wrap creates tons of force on the post, wire wrapping was used on early Mercury, Gemini, and Apollo missions its that secure.
2150361.jpg42178.jpgta_wirewrapconnection.gif
 

Ccolvin968

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All of this advice has been great.
Rich, I appreciate all of your advice as well. Thanks for the history lesson as well!
I just found the blue wire wrapper in your post. Ordering shortly!
 
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Lowpuller

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I borrowed the idea from Chris Erving after doing a LCD build.
 

Lowpuller

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Where do you order the wire wrapper from? I want one as well.
 

OverTheTop

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Wire wrapping is really well engineered for connecting wires. In the early days when speed of electronics was about 3-4 orders of magnitude slower than it is now it worked well. The square post gets seven wraps of wire (standard wrap). That makes for 28 contact points that due to the applied pressure are actually cold-welded for low contact resistance and gas-tight! Add two turns (modified wrap) with the insulation to get improved strain relief and vibration resistance.
 

OverTheTop

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Here are some pics of using a pin header to mount an altimeter. The advantage is that when you swap altimeters around you don't have to remember which wires to put where, so there is one less chance of making a mistake.

AltimetersSideView.JPG AltsCompleted.JPG

The other end is supported by a standoff.

Further details here if you need them: forum.ausrocketry.com/viewtopic.php?f=6&t=5019&start=60
 
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rharshberger

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Ccolvin968

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I have the Chinese matches.
Two people that are in my club use them exclusively and have never had a misfire due to a bad igniter.
 

bobby_hamill

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one rule of thumb I use if mounting electronics vertically ALWAYS mount the batterys
on the OPPOSITE side of the electronic components .

That way if your payload section ever comes in ballistic the battery wont strip off the electronic components from the circuit board.

Also I try to use a MAD as back up with my altimeters . The MAD also adds in a safety factor if the rocket decides to
go horizontal after takeoff . The MAD will then separate the rocket into 2 halves and least slow it down some.
The MAD will prevent a ballistic rocket flying horizontally.
 

Handeman

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one rule of thumb I use if mounting electronics vertically ALWAYS mount the batterys
on the OPPOSITE side of the electronic components .

That way if your payload section ever comes in ballistic the battery wont strip off the electronic components from the circuit board.
+1 on that.

I have over a dozen flights on a HiAlt45 altimeter after it was in a rocket that lawndarted. The sled actually broke, but not where the altimeter was mounted, fortunately. The battery was zip tied in two directions on the opposite side of the sled and was poured out of the remains of the av-bay in about a dozen pieces.
 
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