Building a 2.1" Avionics Bay for a PerfectFlight MAWD Altimeter

[Estimado]

Hello,
I am rebuilding a PML Io into a dual-deploy configuration. I am building an avionic bay using a four inch coupler. Obviously, room is tight. Does anyone have experience or pictures from a similar avionics bay project?

I am using a G10 sled. Do you have any recommendations for what size U-bolts to use on each bulkhead? The nuts and washers protruding inside will be an issue. Are there any appropriate small sized terminal blocks available for mounting to the outside of the bulkheads? Or, would it be ok to just run bare wires through the bulkheads for connection to BP charge ignitors?

Rich

 

[MattieShoes]

I just did this with the LOC 2.5" coupler which is 5" long, and it seemed awfully tight with THAT... But then again, I've no experience with getting a lot of electronics into a small space. I included a couple pics of what I did.

As for the protruding bolts, you can remove some of the bolt which extrudes past the nut with a dremel tool. It'll heat the whole thing up very hot, very quickly, so I suggest having the U portion sitting in some cool water to wick the heat away while you work.

 

[Pantherjon]

Hello,
I am rebuilding a PML Io into a dual-deploy configuration. I am building an avionic bay using a four inch coupler. Obviously, room is tight. Does anyone have experience or pictures from a similar avionics bay project?

Yes, as a matter of fact I do! This is from my NSL Thor..38mm main body tube..
Here is the 'coupler' used as the avbay:

Here is one end..The all thread had to be off center to free up some space to allow the Perfectflite HiAlt45k altimeter to fit..The 2 tubes was an unfulfilled idea I had of using copperhead tubes to hold the cells of a broken down 9v battery..Decided instead to use the battery intact(it just barely fit..

Another view of the end of the avbay

I am using a G10 sled. Do you have any recommendations for what size U-bolts to use on each bulkhead? The nuts and washers protruding inside will be an issue.

I would just use 1/4" eye bolts and not u-bolts..Use coupler nuts to attach the ends to all thread..

Are there any appropriate small sized terminal blocks available for mounting to the outside of the bulkheads? Or, would it be ok to just run bare wires through the bulkheads for connection to BP charge ignitors?

It will be just fine to do a 'direct' connection to your altimeter..Drill a small hole in the bulkhead, run the wire through directly to the output terminals on the altimeter..Use a strip of tape to cover the hole after you assemble the bay to minimize any gasses going into the bay..

 

[blackjack2564]

You really need a 6in coupler for this. I take it this is your first DD and this is really a bear if you start out with a handicap.

If you can't get one then the next best thing to do is make a 6in bay by doing this:
Cut a 3in section of airframe off rocket.
Cut coupler in half. Now glue 1/2inch of each coupler piece into each end of 3in airframe, leaving 1 1/2inch sticking out each end.
Now you have a 6inch Av-bay!

Now follow this link to building an av-bay for a small diameter rocket like yours.
https://www.rocketryplanet.com/forums/showthread.php?t=5373&page=5

Go and start there. It's all laid out with pictures. Size of vents, how to attach to payload with rivets and shear pinning the NC.

Read it. Read it again, then if any questions, just ask.

I'll be back! LOL

 

[rockie]

Nice ! I had missed that thread, now i got some more reading before completing my Blackhawk

 

[Robaust]

Hi Rich,

We have just finished and flown a 2.1" scratch-build with a 'blue tube' Av-bay utilising a MaWD, things are a little tight, although very achievable.

I made a build thread and a specific post regard wiring, with images of the sled. The links are on our home Forum and below;

https://www.ausrocketry.com/forum/viewtopic.php?f=32&t=2071

https://www.ausrocketry.com/forum/viewtopic.php?f=10&t=2142

Hope they help.

Regards,

RobW

 

[cbrarick]

if you want to be really slick, the "thru the wall switch" method works well on these sleds...just take a used Estes D motor and use it to hold a standard Radio Shack SPST rocker switch. Figure out where you want it, then drill a hole for the wires, then epoxy the tube (cut to the right size) to the sled, then route the wires and glue the switch to the top. I glue a couple pieces of 14 gauge wire to each side of the switch to prevent inadvertent operation in case your switch bumps the walls of the coupler when you launch that beast on the biggest motor you can put in the rocket! Worked great for my 38 mm setup!

 

[Larry Curcio]

Hello,
Does anyone have experience or pictures from a similar avionics bay project?

Rich

For tight configurations like this, I just bolt the altimeter to some flexible cutting board plastic, which is sized to be held in by the nose cone or bulkhead. The plastic is cut so that it covers and conforms to at least half of the inner circumference of the chamber. It's all held rigidly because the plastic is curved.

The plastic forms an effective sled, which can be pulled partially out, if required, when the rocket is on the launcher.

No muss. No fuss. Talk about tight, I've used the arrangement to loft the Parrot in a 1" OD Estes rocket on a B4. It worked nicely with an ARTS2 in a LOC Weasel, a Vulcanite, an Initiator...

No place to put the battery? Just Gorilla-tape it below the instrument on the same piece of plastic.

I do have pix, but... I... err... posted them twice before.

-LarryC