Altimeter mounting to sled

[Ccolvin968]

I have got my sled all ready to go and the altimeter is mounted using standoffs.
The sled is a composite one from Madcow. The screws go all the way through the bottom with about 1/8" extending from the bottom with a dab of epoxy since I couldn't get nuts to fit securely with that little amount of thread available. The batteries are double zip tied onto the board along with the switch. This should be fine for a L2 cert flight right? The closer I'm getting the more nervous I'm getting. Thanks!

 

[soopirV]

I have got my sled all ready to go and the altimeter is mounted using standoffs.
The sled is a composite one from Madcow. The screws go all the way through the bottom with about 1/8" extending from the bottom with a dab of epoxy since I couldn't get nuts to fit securely with that little amount of thread available. The batteries are double zip tied onto the board along with the switch. This should be fine for a L2 cert flight right? The closer I'm getting the more nervous I'm getting. Thanks!

I'm far from an expert, but the only thing that I would suggest you add (if not already) are additional zip ties to secure the wiring. Minimizing motion on the sled seems like a good idea in general, and not just the traditionally 'heavy' stuff.

 

[Bat-mite]

Turn it upside down and shake it. If nothing falls off, you're probably good to go.

 

[Ccolvin968]

SoopirV, I have minimal wiring going from the batteries and elsewhere. Not enough to zip tie in place.
I'll give it a good shake test. Thanks Bat-Mite!

 

[rharshberger]

Posting a photo would help.

 

[MikeyDSlagle]

If you are using 9volt with standard 9volt clips double and triple check that they fit securely to the battery. Zip tie if necessary. On one of my nose cone bays I had a pretty solid sled, everything fit just right. Under boost the battery moved just a tad, no big deal, but the clip got caught on a piece of the battery box, preventing it from sliding with the battery. It caused it lose power which resulted in a lawn dart and busted Altimeter 3. I just dug out that sled to replace the battery clip and cut the box to prevent that from happening again. Just a thought.

 

[Ccolvin968]

I'm not at home to take a photo right now. I'm using 3.7v LiPo batteries with an Eggtimer Classic.
The connectors clip together and I use electrical tape to ensure they don't just slip apart. They're hard to pry apart to begin with.
Crossing my fingers for no lawn dart and practicing my setup and take-down just like I would before launch.

 

[cerving]

Zip tie all your wires, especially if you're using screw terminals. Also, tape your battery connectors together, enough so that it wraps around the wires themselves so any motion can't pull a pin out of the connector. Don't ask me how I know about this...

 

[Ccolvin968]

Noted Cerving. Thanks for that. I won't ask how you know. I feel like it might be a touchy subject.

 

[Handeman]

Zip tie all your wires, especially if you're using screw terminals. Also, tape your battery connectors together, enough so that it wraps around the wires themselves so any motion can't pull a pin out of the connector. Don't ask me how I know about this...

The other option is to use generous amount of hot glue to glue the wires to the board.

 

[rocketsam2016]

Zip tie all your wires, especially if you're using screw terminals. Also, tape your battery connectors together, enough so that it wraps around the wires themselves so any motion can't pull a pin out of the connector. Don't ask me how I know about this...

So I have to ask - is this jst connectors and how snug are they? My lipo connections with jst are so tight it is a royal pain to pull them apart, and its really hard to imagine them doing so on their own... i often wish they were looser actually. On te other hand I know you know a lot about altimeter wiring.....

 

[Q-Aero]

So I have to ask - is this jst connectors and how snug are they? My lipo connections with jst are so tight it is a royal pain to pull them apart, and its really hard to imagine them doing so on their own...

You find JST hard to pull, wait to fall on those one , you need to pry them with a screw driver ( on the side of course to not hit both connectors at same time. )m

 

[cerving]

So I have to ask - is this jst connectors and how snug are they? My lipo connections with jst are so tight it is a royal pain to pull them apart, and its really hard to imagine them doing so on their own... i often wish they were looser actually. On te other hand I know you know a lot about altimeter wiring.....

The plastic connectors tend to be tighter than the pins... I've seen the pins come loose from the connectors, especially with the 10-for-$1 eBay stuff. Taping them in keeps that from happening.

 

[markkoelsch]

SoopirV, I have minimal wiring going from the batteries and elsewhere. Not enough to zip tie in place.
I'll give it a good shake test. Thanks Bat-Mite!

If not zip ties consider taping wires down to sled. Simple.

 

[rocketsam2016]

The plastic connectors tend to be tighter than the pins... I've seen the pins come loose from the connectors, especially with the 10-for-$1 eBay stuff. Taping them in keeps that from happening.

Huh good to know. So you've seen the connectors stay tight together but inside them the pins have come apart? That's sort of scary. I got mine from HobbyKing. More impactful than tape holding the two ends together might be fixing the connection so that it is oriented perpendicular to the long axis of the rocket? Or do you think that vibration is the biggest problem and this wouldn't help much? It's too bad, taping all the wires for a pair of quantums each with two batteries adds yet more process to setup.... If the connectors are strong enough and the pins are the problem, what about just taping the wire to the connector on each side? You could do that once with strong tape, or even use glue for it.

 

[Ccolvin968]

Good info everyone! I appreciate the advice!

 

[new2hpr]

Not quite clear, but were you saying that the mounting screws weren't long enough to put nuts on, so they're epoxied?

If that's the case, I wouldn't trust it. Just get some slightly longer screws and some blue loctite to keep it all from vibrating loose. Also easier to remove blue than epoxy if/when you need to pull the altimeter to move to another rocket, etc.

-Ken

 

[Ccolvin968]

I actually don't plan on swapping this altimeter between rockets. It'll be specifically for this rocket for a long time coming. My other ones as of right now are not dd and I just use the JLCR or JLA3 for recovery. My next rocket will be an Eggtimer quark or something like that. We'll see. No major plans at the moment. I'll add some Loctite for good measure. Thanks!

 

[NateLowrie]

A few things not mentioned here:
- you can hot glue the connection pins on the backside to give some additional holding power.
- you can also hot glue the wires down for strain relief instead of zip-ties.
- I don't use JST connections. I cut them off my altimeter batteries and replace them with Minifit Jr connectors, which are positive locking connectors that have a latch on them that clicks close. If you go this route be sure to only clip, strip and crimp one battery connection at a time so you don't inadvertently create a short across the terminal.

 

[Ccolvin968]

Good stuff Nate! I'll keep those in mind.

 

[soopirV]

Noted Cerving. Thanks for that. I won't ask how you know. I feel like it might be a touchy subject.

I like how when I say it you don't need to...but the head of Eggtimer pipes up... :wink:

 

[OverTheTop]

I put Velcro between the batteries and sled, then cable ties around that. The Velcro takes the shear loading, the ties just stop the Velcro peeling under severe acceleration. Ties do not need to be too tight that way, possibly putting a bit less strain on the LiPos mechanically.

If your LiPOs puff up, ditch them and fit new ones.

You can tack the wires down with hotmelt, or cyanoacrylate. CA is a little more permanent and does a great job stopping them flapping around, hotmelt a bit easier to rework. Remember, you probably don't need to stick the entire wire down, just stitch it in places .

I put a dob of hotmelt on the sled to baluk the movable part of the connector coming out (I generally use right-angle connectors on the sled. Easy to remove after flight.