HED setup and moving AV bay from rocket to rocket - how to do?

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Sep 1, 2011
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I am building several rockets right now and i have two issues that I need some help with. Hope to purchase AV components this week. I already have an RTX system that I have yet to fly but it is together and tested.

1. a 3" punisher - how to do 2 altimeters and an RTX in an HED system?

- What are you guys running with your HED setups? I can go 1 altimeter and RTX but if I go 2 altimeters where would you put the RTX? I could borrow a Comspec and tape to harness (which I do not own a comspec style - so I don't think I want to purchase for just one rocket.

2. I've wanted to make a sled or AV bay that moves from rocket to rocket. I already have many rockets with dedicated altimeters and just seams like a waste. Several rockets are set to exactly the same settings and even use similar charge amounts wouldn't it be nice to have a BAY - not just a sled to move between 3~5 rockets. I would keep the existing dedicated bays for my other rockets but from here going forward? I would even go as far as saying those 3 or 4 rockets would even use the same recovery components - so in theory - undue 2 quicklinks - add the charges and put the whole system in another rocket shell. why reinvent the wheel? maybe even an adapter bay to fit in 54, 3 and 4"

anyone else doing this?
1. a 3" punisher - how to do 2 altimeters and an RTX in an HED system?
I use a single altimeter and a 900 MHz GPS tracker, both in the avbay, in my Punisher 3.

As for interchangable sleds, there are many ways to do it. I haven't found it works well in practice because of lack of standardization in where switches and wiring go, etc. Also, it's easier to prep multiple rockets for a launch if you have multiple altimeters, and they've gotten so cheap it's not unreasonable to have several. YMMV.
Punisher sled.

No trouble getting RRC3 & Strato [or RRC2] on one side of sled.

Batteries & gps/RTx on other side.

DSCN5258.jpg DSCN5260.jpg

Don't have pics of latest version. I put the GPS on it own sled [same size as GPS} this allows me to tape battery on other side.
Now I just wrap in bubble wrap, and stick under side of sled that has just 1 battery on it.

I now move the GPS easily between rockets...will fit in 54mm av-bay under sled. In some nose cones....just about anywhere.

you soon find out, you need more than one sled......I have 2 with 2 alters for 3 in rockets and up. They will fit in anything over 3in.

2 sleds with only 1 altimeter for 38 and 54 airframes..... these can both be put in larger av-abay. Put 1 sled on each tie rod!

All in all if flying more than just "a Couple" of rockets, you soon find out that at least 6 altimeters are needed. At the price you can buy them now it's a no brainer. Heck 150.00 get you 3 altimeters these days.
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thanks guys - holy smokes CJ you can pack 5 gallons of S** in a 3 gallon bucket.

yes Alts are very reasonable - and I do prep rockets prior to arrival. My Problem is that everyone of my 13 altimeters are dedicated to the rocket mainly cuz I'm too busy /lazy to take them out. Just trying to think of standardizing from switches to charge connectors so all AV bays are the same that I can plug and play.
According to Wildman's site, the 3" Punisher is setup for HED. I am not familiar with it's design. As in what holds the aluminum bulkplates to the nose cone? Can you run threaded rod from the tip? Does it have a defined shoulder in the nose cone (for a ring to rest against)?

I have a design for a nose cone bay in a 4 inch rocket that is designed to use a tracker in the nose cone and the altimeter in the shoulder. The tracker will be completely isolated in the nose cone. It should easily scale down to 3 inch. Though some mods will have to be made for it all to fit in a 3 inch it shouldn't be too difficult. I didn't design it for two altimeters but a little spacial awareness and modifying will get it there.

I also had some ideas for easily moved sleds. Plan was to use quick connect cable such as USB (or mini/micro) or 6 pin JST type connectors. Ended up going with the JST type for the wiring but gave up on the sled itself. I have more electronics that I do rockets ATM so I can just prep before launch. But using quick connectors and a standard spacing on your threaded rod or even one center mounted, a "modular" sled, or entire bay, will be doable. If you use Eggtimer Quarks, it will be much easier.

I am bad about losing track of threads and posts on here. Feel free to PM me if you would like to know more about my nose cone bay setup and I'll try to get it assembled and send you some pictures for ideas.

Mikey D
You guys are showing electronic sleds in the NC........ that is not HED.

HED is "head end deploy" or nose cone dual deploy, the main parachute is in NC electronics & gps/tracker are in the shoulder/av-bay. No payload....drogue is in fincan and NC is shear pinned to shoulder/av-bay and deploys main.

The idea is to get a short & compact a rocket as possible for performance....it also opens doors for scale rockets where no payload or short stature prevent DD. Being able to utilize the NC for that changes the game dramatically.

Here is the build thread for Punisher H.E.D. https://www.rocketryforum.com/showthread.php?120615-CJ-s-quot-PUNISHER-quot-build!

Shortcut to the NC part of it:
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Correct CJ, I can't use the NC for the tracker - but can put the tracker in the AV bay with 1 altimeter or 2 altimeters and no tracker - yuck. Maybe I'll do 2 Alts and, like mentioned above , attach the RTx to the drogue cord with a bay or protection of some sort
I buy G10 in sheet and do a CJ type sled for each of my rockets - meaning the sled 'fills up' the coupler and may notch for eyebolt clearance . The Punisher has a 6 inch coupler ..my Dark Star has a 8 inch coupler ect.. Sleds work out to be the cheaper part of the bay.

Now my technique differs because I add the all thread runner tubes on the sled ..not because I need them ..but because they allow me to route the wires and batts ..and tie them down or bury in epoxy without the all thread dislodging or binding .

Started off with std hobby store 1/4 inch brass tubing , but now using Aerotech 1/4 inch igniter packing tubes as it glues on better with 5 min epoxy . I think you can buy longer 1/4 inch launch lugs from Balsa Machining too .

I tend to leave the sled and lids with the rocket , but may unmount the altimeter or battery as needed . To do this without having to rewire every time I run my wires underneath the sled and drill a corresponding hole to the altimeter terminal block . The wire comes through the hole from underneath where it is secured . When the altimeter is removed the wiring stays in place ., making it easy to remount when needed.

Have gone all lipo and starting to leave them on the sled .. I bring the sled to the charger and top off before packing for a launch. The lipos vary in size and what fits perfectly for one may not work for a bigger loose lipo in the field .. so have been trying to acquire a few more lipos that are flat and square like the HobbyPeople brand (RIP) , Rhino or Zippy Compact -- than more altimeters .

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Thx everyone - I'll go back to the drawing board on this. I typically leave the lipo on the sleds as well. Maybe I can get all three to fit be changing the type of sled or go to a modular sled.
What I wanted was 2 lipo, 2 RRC2 or SLCF and an RTX, with the antenna sticking out of bay and I'll retry this or rethink it. Was hoping to fly at MWB and definitely Argonia.

I also think that an interchangeable AV bay assembly is possible for the future but not sure if I'm the guy to do it. Kinda like a NC bay but more to it. Maybe one day.

Over the Top, you are over the top. I have read a few builds from down under on your site and you all have some amazing craftsmanship, makes me feel like a winnie with my little sled dilemma when I see what you did, lol.