All in one altimeter/recovery unit with a Blue Jay altimeter

[manixFan]

I have a fair number of Ellis Mountain 29mm H50 and H101 single use motors I want to fly. I also have a several lengths of green fiberglass 29mm body tube I got from him that I want to turn into rockets rather than use as a motor mount. To fly a 29mm MD rocket with either of those motors I need to use an altimeter, which is a bit daunting given the small size. I've flown many 38mm MD rockets and those are bad enough. When @Adrian A introduced the Blue Jay altimeter with an integrated magnetic switch, I got inspired to make a simple all-in-one AV/Recovery bay.

The CAD was done in OpenSCAD and I was able to reuse quite a bit of code from previous projects. My goal was to design an easy to prep bay that I could then slide into the rocket without any further work. I wanted to do as much as possible with 3D printed structures so I could make up several units in advance and have them prepped and ready. The fin can and nose cone will also be 3D printed.

My final design uses a recovery bulkhead with an embedded 1/4" stainless steel rod as an anchor for the recovery harness. Two 4-40 brass inserts set into the side of the bulkhead anchor it to the fiberglass body tube. The opening for the recovery harness also acts as a pass-through for the e-match wires. The actual altimeter compartment is pretty standard, except there is no need for an opening for a switch. Aluminum 4-40 all thread holds everything together but does not carry any of the recovery system load – that's done by the steel rod and 4-40 screws into the brass inserts. Due to the light weight and especially if I use a streamer, I'm not concerned about the shock loads on the brass screw inserts.

I can prep the entire thing, including the streamer or parachute, and then just slide it into the rocket and secure it in place with two 4-40 steel screws. I use a 3D printed drill guide to make sure the holes match the bulkhead.

There are other very small altimeters available, but the built in magnetic switch of the Blue Jay is what makes this installation so simple relative to needing some kind of external switch. An on-board screw switch could also work – I'm pretty sure I could get an Eggtimer Apogee to work by moving supports around and clipping the programming pins, but I really like all the extra data I get from the Blue Jay, as well as the bluetooth connectivity.


Tony

here's the complete bay assembled externally, with one ejection charge for apogee recovery using a large streamer:


this is an 'exploded' view of the assembly, showing the brass inserts and steel anchor rod (the empty hole on the mount is for a battery retaining screw):


the business end of the recovery anchor:



finally, the entire bay installed in the rocket (I may use set screws instead of regular screws):

 

[311stylie]

Loving it Tony. Great thread. BTW, that's one sexy ruler you have there.

 

[Buckeye]

Good design. Is there a tracker in the nose?

 

[manixFan]

Good design. Is there a tracker in the nose?

Yes, one of @Brainstormz123 RDF beacons to start, but if I can get an Eggtimer unit in there, eventually one of those.


Tony

 

[kjhambrick]

Tony --

What a beautiful av-bay capsule !

Q: What caliber brass is that for your ejection charge ?

Q: Do you plan to fasten it to the head-end of your av-bay ?

Q: How much BP are you thinking about using for your 29mm airframe ?

I would be definitely be interested in your ground testing, especially if you use the Blue Jay video feature

Thanks for the ideas and good luck with your flights !

-- kjh

 

[cwbullet]

I have a fair number of Ellis Mountain 29mm H50 and H101 single use motors I want to fly. I also have a several lengths of green fiberglass 29mm body tube I got from him that I want to turn into rockets rather than use as a motor mount. To fly a 29mm MD rocket with either of those motors I need to use an altimeter, which is a bit daunting given the small size. I've flown many 38mm MD rockets and those are bad enough. When @Adrian A introduced the Blue Jay altimeter with an integrated magnetic switch, I got inspired to make a simple all-in-one AV/Recovery bay.

The CAD was done in OpenSCAD and I was able to reuse quite a bit of code from previous projects. My goal was to design an easy to prep bay that I could then slide into the rocket without any further work. I wanted to do as much as possible with 3D printed structures so I could make up several units in advance and have them prepped and ready. The fin can and nose cone will also be 3D printed.

My final design uses a recovery bulkhead with an embedded 1/4" stainless steel rod as an anchor for the recovery harness. Two 4-40 brass inserts set into the side of the bulkhead anchor it to the fiberglass body tube. The opening for the recovery harness also acts as a pass-through for the e-match wires. The actual altimeter compartment is pretty standard, except there is no need for an opening for a switch. Aluminum 4-40 all thread holds everything together but does not carry any of the recovery system load – that's done by the steel rod and 4-40 screws into the brass inserts. Due to the light weight and especially if I use a streamer, I'm not concerned about the shock loads on the brass screw inserts.

I can prep the entire thing, including the streamer or parachute, and then just slide it into the rocket and secure it in place with two 4-40 steel screws. I use a 3D printed drill guide to make sure the holes match the bulkhead.

There are other very small altimeters available, but the built in magnetic switch of the Blue Jay is what makes this installation so simple relative to needing some kind of external switch. An on-board screw switch could also work – I'm pretty sure I could get an Eggtimer Apogee to work by moving supports around and clipping the programming pins, but I really like all the extra data I get from the Blue Jay, as well as the bluetooth connectivity.


Tony

here's the complete bay assembled externally, with one ejection charge for apogee recovery using a large streamer:
View attachment 676780

this is an 'exploded' view of the assembly, showing the brass inserts and steel anchor rod (the empty hole on the mount is for a battery retaining screw):
View attachment 676814

the business end of the recovery anchor:

View attachment 676786

finally, the entire bay installed in the rocket (I may use set screws instead of regular screws):
View attachment 676790

Great design. Any chance you might upload the STL files?

 

[manixFan]

Tony --

What a beautiful av-bay capsule !

Q: What caliber brass is that for your ejection charge ?

Q: Do you plan to fasten it to the head-end of your av-bay ?

Q: How much BP are you thinking about using for your 29mm airframe ?

I would be definitely be interested in your ground testing, especially if you use the Blue Jay video feature

Thanks for the ideas and good luck with your flights !

-- kjh

I appreciate the kind words!

Q1: I use .38 special nickel-plated brass (with spent primers) for my smaller ejection charges. The nickel plating is far less reactive than brass to fouling from black power, although I have started using Triple7 BP substitute after some testing showed it works just as well. For larger MD rockets I use .45 Long Colt brass

Q2: I have other ejection charge holders for the brass that allows me to just slide the cartridge in sideways so it's retained by the case rim. But in this rocket there really isn't room for that, so I'll just tape the charges to the shock cord. I do cover the lower part of the cord with heat shrink to protect it

Q3: I haven't done tests yet, but I suspect that even with Triple7 about .5 grams will be plenty. On my 38mm MD with a shear pin I only use .8 grams as my primary. I'll report back with numbers once I do the tests. I'm still finalizing the nose cone design – I'm going to put an RDF beacon in it and was trying to get fancy, but now I think I'll just use some stuffing to hold it in place rather than a mount.

Great design. Any chance you might upload the STL files?

Thank you, and yes, I can upload the files – I'll write up some brief notes and post them. The only thing I don't like is for clearance I don't use standoffs, so the Blue Jay sits right on the mount. But as long as the screws aren't over-torqued, it should be fine. I do use heat-set brass inserts for the 4-40 screws.


Tony

 

[kjhambrick]

Tony --

Looking at your pic:


Your Altimeter / Recovery Unit is sitting down by the motor.

And an Ellis Mt H50 should be capable of sending a 29mm rocket 10k feet or so ...

Are you going to use a line cutter for your main or are you flying single deploy mode ?

Thanks !

-- kjh

 

[David_Stack]

Tony --

Looking at your pic:
View attachment 680663

Your Altimeter / Recovery Unit is sitting down by the motor.

And an Ellis Mt H50 should be capable of sending a 29mm rocket 10k feet or so ...

Are you going to use a line cutter for your main or are you flying single deploy mode ?

Thanks !

-- kjh

kjh;

Tony added a 'post script' on his initial post: "here's the complete bay assembled externally, with one ejection charge for apogee recovery using a large streamer:"

 

[kjhambrick]

kjh;

Tony added a 'post script' on his initial post: "here's the complete bay assembled externally, with one ejection charge for apogee recovery using a large streamer:"

Thanks, Dave !

I missed that note !

-- kjh

 

[manixFan]

Tony --

Looking at your pic:
View attachment 680663

Your Altimeter / Recovery Unit is sitting down by the motor.

And an Ellis Mt H50 should be capable of sending a 29mm rocket 10k feet or so ...

Are you going to use a line cutter for your main or are you flying single deploy mode ?

Thanks !

-- kjh

I haven’t forgotten about posting the stl files, I’ll do that soon.

The AV bay does sit right on top of the motor for ease of setup. I wanted to avoid a traditional two–break recovery airframe for simplifying construction. For the first flights I’ll use a big streamer, but I am thinking about using a cable cutter eventually, as long as it doesn’t get too complicated.

There are a lot of 3D printed parts to make assembly easy which hopefully will survive flirting with Mach each flight (on the H101at least). My sims end up at about 8,000 feet using the motor file for the H101 I made using my test stand. It will be interesting to see how close I get but I won’t know for a couple of months.


Tony

 

[bad_idea]

It will be interesting to see how close I get but I won’t know for a couple of months.

@kjhambrick : as the saying goes, we'll see more in Seymour!

 

[manixFan]

Ok, here are the STL files for the complete setup. These are sized for the filament–wound translucent green fiberglass tubing that I got from Bob Ellis, you may need to scale slightly depending on your tubing. The threaded rod and mounting screws are all 4-40, and I do use brass heat-set inserts for the recovery anchor. A 1/4" stainless steel rod cut to the appropriate length is placed through the hole in the recovery anchor, and the vertical hole is size to allow both a Kevlar bridle and an e-match to pass though. The top cover of the AV bay has holes for the e-match leads to pass through.

All the parts are very easily modeled in any CAD software so it should be very easy to use reproduce new parts if you need to alter the geometry.


Tony

The drill guide is a slightly modified version of the one posted by @vcp in his thread. The other parts are all done in OpenSCAD. PNG images of each part:


STL files:

 

[kjhambrick]

Very Nice, Tony !

One more Q: Do you think the cylindrical tube is stout enough to serve as a coupler for a pair of 29mm glass tubes ?

-- kjh

 

[manixFan]

Very Nice, Tony !

One more Q: Do you think the cylindrical tube is stout enough to serve as a coupler for a pair of 29mm glass tubes ?

-- kjh

Ahh, you've come across one of the big reasons I decided to go with a 'no break' recovery bay! Since these rockets will tickle Mach with the H101, I figure I need a pretty robust coupler. I don't have any fiberglass on hand, and what I do have is very heavy cardboard tube that I didn't really want to use. As is, I don't think the 3D printed coupler would hold up except under the most ideal conditions, and since it has an altimeter inside it, I did not want to take a chance with one breaking in half and either losing or damaging the altimeter.

@bad_idea and I were discussing ways in strengthening 3D printed coupler tubes. I am thinking of printing 2 thin walled tubes that fit inside each other but at different layer heights, and then gluing them together. He suggested annealing the tubes together, or using ABS or ASA filament and welding the tubes together with acetone. I suppose I could just buy some fiberglass coupling but that takes all the fun out of it!


Tony

 

[kjhambrick]

... <<snip>> ... I suppose I could just buy some fiberglass coupling but that takes all the fun out of it!

Yes, indeed it would

And besides, I've had no luck finding 29mm fiberglass couplers ...

Maybe I've been lookin' for stuff in all the wrong places ?

-- kjh

 

[bad_idea]

And besides, I've had no luck finding 29mm fiberglass couplers ...

Wildman lists them. I think that may be a new addition since acquiring Curtis' equipment. Curtis listed 29mm coupler, but I was never brave enough to place an order with him before he sold to Wildman.

 

[manixFan]

Wildman lists them. I think that may be a new addition since acquiring Curtis' equipment. Curtis listed 29mm coupler, but I was never brave enough to place an order with him before he sold to Wildman.

I was surprised to see them listed when I checked there for tubing. If I was smart I would have tagged along with someone's Black Friday order and tried out a sample. I suppose someday I'll have to order some so I can do proper 2-break AV bays if I decide that's the way to go.


Tony

 

[kjhambrick]

Wildman lists them. I think that may be a new addition since acquiring Curtis' equipment. Curtis listed 29mm coupler, but I was never brave enough to place an order with him before he sold to Wildman.

Dang !

I was never even brave enough to look for them there !

That does it ... I need to replace my cardboard coupler in my mini-MAUDE 29 !

Thanks for the tip, Stephen !

I was surprised to see them listed when I checked there for tubing. If I was smart I would have tagged along with someone's Black Friday order and tried out a sample. I suppose someday I'll have to order some so I can do proper 2-break AV bays if I decide that's the way to go.

Tony --

Do you want me to add a little extra for when I see you next month or so at the TNT Seymour site ?

-- kjh

 

[bad_idea]

As is, I don't think the 3D printed coupler would hold up except under the most ideal conditions

I keep four short PETG-printed tube sections on my desk - one each of 1 through 4 perimeters - to remind me of the relative toughness of each thickness as I'm designing printed parts. Four perimeters is getting stout, especially in bending, which I'd think would be what you'd want to watch out for with a coupler.

I don't see why upping the perimeters further, or printing two layers of multiple perimeters separated by good infill, wouldn't hold up.* Trouble would be making room for electronics and any longitudinal elements (all-thread etc.) running through it.

* Admittedly my supersonic experience is limited as yet.

I was surprised to see them listed when I checked there for tubing. If I was smart I would have tagged along with someone's Black Friday order and tried out a sample. I suppose someday I'll have to order some so I can do proper 2-break AV bays if I decide that's the way to go.

BF order wouldn't come in for quite a while anyway.

 

[manixFan]

I keep four short PETG-printed tube sections on my desk - one each of 1 through 4 perimeters - to remind me of the relative toughness of each thickness as I'm designing printed parts. Four perimeters is getting stout, especially in bending, which I'd think would be what you'd want to watch out for with a coupler.

I don't see why upping the perimeters further, or printing two layers of multiple perimeters separated by good infill, wouldn't hold up.* Trouble would be making room for electronics and any longitudinal elements (all-thread etc.) running through it.

* Admittedly my supersonic experience is limited as yet.

BF order wouldn't come in for quite a while anyway.

That's a good point about using enough perimeters to increase stiffness/toughness. But you're exactly right – with a 29mm body tube, it's very easy to get to a thickness that makes it hard to fit electronics, batteries, etc. into the AV bay. 3D printed parts are great in many aspects, but small diameter body tubes/couplers is probably not one of them.


Tony

Edit: Also a great idea to keep samples on hand to judge relative strength as a starting point when modeling, I'll have to print some up.

 

[manixFan]

....

Tony --

Do you want me to add a little extra for when I see you next month or so at the TNT Seymour site ?

-- kjh

Yes, that would be fantastic! I'll trade you another couple of radio beacon holders for your efforts, as well as pay the cost of the materials.


Tony

 

[kjhambrick]

That is a deal, Tony !

I am looking at 3-inches ( or so ) each or my av-bay couplers and I am thinking I want four or so couplers to play with ...

That means that I 'need' 12 inches of 29mm coupler so I will order 18 inches for 'mistakes' and tests and such.

How much do you need ?

I'll keep yours in my rocket box in case I see any local TNT members ( ??? like maybe Harry ??? ) before I can get to Seymour.

There is a TH XMas Party on Dec 14 at Hearne and if I have it by the Hearne Launch and if Harry is there I can send it north with Harry.

-- kjh

 

[miket6000]

That's a really tidy little av bay. I'm currently designing one for my 29mm minimum diameter rocket based off a 6" (but will probably cut down to 4") length of 29x1mm carbon fiber round tube I got from AliExpress. I'm building a more traditional dual split arrangement but will absolutely steal your over/under arrangement for the all thread, though probably not 3d printed.

I think I will however, print your drill guide (or copy it at least). It looks like a great way to get consistently spaced holes.

 

[manixFan]

That is a deal, Tony !

I am looking at 3-inches ( or so ) each or my av-bay couplers and I am thinking I want four or so couplers to play with ...

That means that I 'need' 12 inches of 29mm coupler so I will order 18 inches for 'mistakes' and tests and such.

How much do you need ?

I'll keep yours in my rocket box in case I see any local TNT members ( ??? like maybe Harry ??? ) before I can get to Seymour.

There is a TH XMas Party on Dec 14 at Hearne and if I have it by the Hearne Launch and if Harry is there I can send it north with Harry.

-- kjh

I’d like to have several AV bays like you, so 18” should be fine for me as well. Thanks again for doing this.


Tony

 

[manixFan]

That's a really tidy little av bay. I'm currently designing one for my 29mm minimum diameter rocket based off a 6" (but will probably cut down to 4") length of 29x1mm carbon fiber round tube I got from AliExpress. I'm building a more traditional dual split arrangement but will absolutely steal your over/under arrangement for the all thread, though probably not 3d printed.

I think I will however, print your drill guide though (of copy it at least). It looks like a great way to get consistently spaced holes.

Thanks for that. The drill guide is based on this file: ( done by @vcp)

https://www.rocketryforum.com/threads/3d-printable-component-generators.148308/#post-1827595

It's done in OpenSCAD which is free and does not take a lot of space. You may have to scale the model a bit to get a good fit. If it's too big, you can just wrap tape around where you are going to drill the holes to get a good fit, or I use blue tape on the inside of the drill guide if needed.

Good luck!


Tony