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AV bays in small rockets

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snrkl

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ok: so I am planning an Apogee Aspire for supersonic flight - now a 29mm MD rocket going to 1300m means I will definitely need a tracker.. I also want to jam my JLA3 in, there is no point going fast and high without getting the data to know how high/fast we went..

So the payload I am looking to carry is a JLA3 and an eggfinder mini..

Initial planning is for a G76G or a G77R - I am simming with both for the time being, but haven't made a hard choice and am open to other G class motors.. if I get to H that I see are available through my local purveyor, suddenly I am exceeding altitude ceilings and getting into places I don't feel I am ready for yet... While I am open to suggestions of other motors, my main focus here is on understanding and gaining the skills to design/construct the AVbay elements..

So, to my question: How do people build / attach AV bays on to small diameter rockets that are using motor ejection charges? I can certainly build an AV bay that slots onto the top of my airframe under the NC, but I am not really certain how people actually attach the top end with the nose cone in a way that allows access to the actual AVbay...

(an aside with the additional BT based AV bay, as soon as I add it to the sim, I'm losing my mach breaking capabilities on the 29mm G motors I can get my hands on... which kinda sucks..)

I have also been pondering installing the EggFinderMini in the nose cone - I am certainly able to take the end off the nose cone, but then I am a little uncertain of how the whole thing is capped off at the blunt end to keep it all together and still allow for NC retention and access to the AV package. I note that HPR folks often have an allthread running between the NC tip and the back NC bulkhead and replace NC shoulders with a coupler and a bulkhead, but in such a small package, this doesn't seem feasible..

I am interested on peoples thoughts here...
 

sl98

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2017-04-03 18.29.53.jpg
This is an Estes BT-60 nosecone with an Eggfinder. I don't have it in front of me so I'm going by memory. There is a 2" length of body tube (silver) that is glued 1/2 onto a 2" piece of coupler. I have a bulkhead glued inside the body tube and on top of the coupler. I drilled two holes in the bulkhead and tied a length of 1/8 kevlar for retention point. Sled is glued to bulkhead and along inside of body tube. Nose cone is attached with 2 plastic push rivets.
 

Sooner Boomer

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You can use plastic push rivets, or you can drill holes through nosecone and body tube (so they're aligned) and epoxy nuts to the inside of the nosecone. Re-enforce the body tube around the holes with CA. I've got some short 8-32 mushroom-head torx machine screws I use for this (but regular square-sided ones would work, too).
 

soopirV

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instead of removing the base of the nosecone, cut a "window" in the shoulder big enough to admit the tracker and battery. Squish in some foam pieces to keep things from jostling around, and cover the window with some tape. I've had luck tapping the Polypropylene material to accept a 4-40 screw or two as a retainer- would recommend that if you're going to increase the mass of the cone. Sooner.boomers advice to epoxy nuts in is solid, but probably not required...YMMV.
 

Tinker

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Have you thought about using the Altus Metrum Telemini? It would save you weight I think and provide for all the systems you need +

Tinker
 

snrkl

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Have you thought about using the Altus Metrum Telemini? It would save you weight I think and provide for all the systems you need +

Tinker
Interesting... I just took a look. My initial thoughts are that the ham based transmission makes things more complex for me.
 

Tinker

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Basic Ham radio is a pretty simple test here. (Not that I have gotten off my ass and done it yet, but in the very near future). I hadn't thought of that it might be more laborious there. That being said, weren't you looking for an easy PC connection and gps plotting of the flight? That would be bread and butter for this family of products, if not this one.

But I get the impression that AM is like Apple, you buy into the family or you don't.

Tinker
 

Buckeye

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(an aside with the additional BT based AV bay, as soon as I add it to the sim, I'm losing my mach breaking capabilities on the 29mm G motors I can get my hands on... which kinda sucks..)
Yes, this is the reality of the Aspire. Apogee claims 1 mile (and maybe Mach) on an F10. However, if you want to actually measure data and find the rocket afterwards, then an F10 isn't gonna cut it with all the extra mass for electronics. Nor is a G motor, as you are finding out.

Lots of threads in the forum to give you ideas. I have done ebays in 38mm (Wildman Blackhawk), but not 29mm.

All that said, I trust the simulation over the altimeter when it comes to speed determination, anyway!
 

snrkl

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I've managed to sim the aspire to Mach 1.02 with the added weight of an eggfinder mini and LiPO plus the JLA3 using an aerotech g80...

I'll be postulating on that in a new thread later in the week.

For now, the suggestions here have me better understanding ebay construction techniques - I might look at starting a generic small BT60 ebay and / or nosecone mod while I have some time off work this week...
 

Tonimus

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You can pare the weight of the electronics down by using a small lipo (100mAh) for the Eggfinder and pulling the case off of the JLA3. Stuff all of it and foam into the nosecone. Probably the lightest way to get everything with what you've got already. Then a couple of dabs of hotglue to hold the last bit of foam in. That should hold it all in and still allow air through the foam so the JLA can do its thing.
 

LithosphereRocketry

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Yes, this is the reality of the Aspire. Apogee claims 1 mile (and maybe Mach) on an F10. However, if you want to actually measure data and find the rocket afterwards, then an F10 isn't gonna cut it with all the extra mass for electronics. Nor is a G motor, as you are finding out.

Lots of threads in the forum to give you ideas. I have done ebays in 38mm (Wildman Blackhawk), but not 29mm.

All that said, I trust the simulation over the altimeter when it comes to speed determination, anyway!
Are there any AT 29-180 G motors that would fit the bill? I know CTI has the G54 Red Lightning longburn in their 3G case but it ships HAZMAT.

Sent from my LGL44VL using Rocketry Forum mobile app
 

dhbarr

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g75j comes closest, I think. Of course there's several H motors in that same case to do a Mach Mile.
 

ksaves2

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View attachment 327891
This is an Estes BT-60 nosecone with an Eggfinder. I don't have it in front of me so I'm going by memory. There is a 2" length of body tube (silver) that is glued 1/2 onto a 2" piece of coupler. I have a bulkhead glued inside the body tube and on top of the coupler. I drilled two holes in the bulkhead and tied a length of 1/8 kevlar for retention point. Sled is glued to bulkhead and along inside of body tube. Nose cone is attached with 2 plastic push rivets.
Yup, Nosecone payload bay just like sl98 shows. You use a coupler and a short body tube length. Or long bodytube length as the case may be.

IMG_20170113_063231.jpg

That long upper bay holds an EggTimer TRS with a Linx antenna projecting up into the nosecone with the shoulder cut off like sl98 shows. Two terminals on the aft bulkhead for apogee and a Prairietwister Rocketry cutter to unfurl the
main. Single break deployment. Nice high flights on the venerable J350. Pricey glass nosecone, LOC tubes and 5 ply plywood for fins with 1/3rd, 2/3rds and full span 'glass cloth lamination on the fin can. 12 pieces of glass cloth that
were a pain to apply but worth it.

IMG_20170113_063212.jpg

This is the result above when stupidhead used the mayhem rail guides on a dirty rod that bound up. Rocket blasted through and destroyed one half of the guide and still went 8500', Mach 1. I asked Bill if I could buy a replacement half
and God bless 'em he sent me a new guide of the stronger material gratis. It was my fault and I woulda' paid but that's the kind of guy he is...... Plus it showed me how strong that laminated fincan is! Just a few paint chips.

Kurt
 
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