Avionics bay for HPV4PoC

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strud
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Avionics bay for HPV4PoC

Postby strud » Fri May 29, 2020 11:45 am

One of the key components within the HPV4PoC vehicle I'm working on is the Avionics bay.

This is placed at the top end of the vehicle ie coupled into the Nosecone since I am going with a dual deploy version of head end where the main chute is within the NC, while the drogue is placed below the AvBay and above the head end of the motor.

So since this is a PoC for a more serious vehicle, the main goals for this Avbay are:
- keep mass as low as practicable
- optimise density ie pack as much as I can in the space available
- provide structure to support tensile recovery loads - in many cases these will be directly transmitted through this component
- implement features to allow use of BP at high altitudes (aka ejection canon-tubes)
- provide suitable mounting points for antennae
- allow for recovery/ejection charge redundancy (both events)

Anyway, will all that being said, here are some images of the design and some of the components made to date.


End caps

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Ejection cannon tubes & end caps

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Board carrier structure

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Assembly thus far

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Next steps are:

- Turn steps into endcaps to allow outer tube to be inserted
- o-ring grooves in endcaps
- radial holes in endcaps for shear pins (top and bottom required)
- antennae RF connector mounting points
- mount boards & batteries
- create 'switch band' and mount onto outer tube
- decide upon harness attachment points/eyebolts or similar

Will post pics as I progress.

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SpaceManMat
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Re: Avionics bay for HPV4PoC

Postby SpaceManMat » Sat May 30, 2020 11:59 am

Pretty serious looking ave bay.
What’s the plan with the HPV project?
QRS: 124
AMRS: 32 L2 RSO
Highest Altitude: 13,647 feet
Fastest Flight: Mach 1.55
Largest Motor: CTI 1115J530 IM
Current Project: X Wing

strud
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Location: Central Tablelands, NSW

Re: Avionics bay for HPV4PoC

Postby strud » Sun May 31, 2020 4:25 am

Hi SpacemanMat,

the HPV4x vehicles are part of a project to get a 4" N2O hybrid powered rocket as high as I can and in doing so stretch my rocketry skills and techniques as much as possible.

The PoC (Proof of Concept) vehicle is to test as many of the concepts to be used in the later iterations as I can, albeit with much lower altitudes and velocities.

The rough progression as I see it now could be something like this:
- HPV4PoC : 4000m, <= M1.2, 1350N tune 4s burn time, 11.5kg launch mass half fill
- HPV4PoC : 7000m, <= M1.6, 1350N tune 7.5s burn time, 13.9kg launch mass, full tank
- HPV4.1 : 20000m, <= M2.5, 1500N tune, 15s burn time, approx 17kg launch mass (partial tank fill)
- HPV4.2 : >50000m, M3.3, 1500N/700N tune, 27s burn time, 21kg launch mass

So I need to get HPV4PoC off the ground and have some success before I push further. Those sort of flights are familiar territory but 4.1 and of course 4.2 will require some techniques and materials that are new to me, due to heating effects and resonances such as flutter...

strud
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Re: Avionics bay for HPV4PoC

Postby strud » Sun May 31, 2020 10:41 am

End caps with step and oring grooves done

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Bay inserted into Nose cone (no shear pins yet)

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Assembled into top of airframe tube (switch band and shear pins not implemented yet)

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SpaceManMat
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Re: Avionics bay for HPV4PoC

Postby SpaceManMat » Sun May 31, 2020 10:50 pm

Sounds like a great project 8) I shal watch with interest.
QRS: 124
AMRS: 32 L2 RSO
Highest Altitude: 13,647 feet
Fastest Flight: Mach 1.55
Largest Motor: CTI 1115J530 IM
Current Project: X Wing

strud
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Posts: 1058
Joined: Thu Oct 02, 2008 7:37 am
Location: Central Tablelands, NSW

Re: Avionics bay for HPV4PoC

Postby strud » Tue Jun 02, 2020 9:52 am

Made up some harness attachment points last night from 16mm Al bar, reason being is to keep mass down when compared to commercially available eye bolts etc.


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Had to make a radius cutter to debur the edge of the cross hole

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The bolt attaching these from the inside of the end caps will be an M8 titanium low profile cap screw OR and equivalent aluminium one, once again to keep mass down.

examples;

https://www.aliexpress.com/item/4000011301538.html?spm=a2g0s.9042311.0.0.64fc4c4d9wrFgO

strud
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Joined: Thu Oct 02, 2008 7:37 am
Location: Central Tablelands, NSW

Re: Avionics bay for HPV4PoC

Postby strud » Thu Jun 04, 2020 9:24 pm

Thinking about power switches that are not too miserable to turn on & off from the pad and remembered something I had used many years ago (about 18 actually)

Switched 3.5mm audio socket with a pull pin, previously being an audio plug with a ribbon on it :-)

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So these ones from RS are pretty decent and are 3 pole so can have 3 separate circuits and have a good current rating.

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https://docs.rs-online.com/acaa/0900766b815885de.pdf

If more circuits are needed, these could be put one behind the other.

Will make up a little PCB to make mounting and wiring easier.

They will be oriented such that the switching contacts will be in the horizontal plane ie accelerations in the Z axis will not act on them.

Will think up some ways to test for contacts opening on shock, but expect this to be at a very high acceleration given the very low mass of the sprung contact.

strud
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Re: Avionics bay for HPV4PoC

Postby strud » Fri Jun 19, 2020 8:53 am

A bit more progress.

- RF (SMA) connector mounting holes in place (1/4 x 36tpi)
- Attachment points started (made from 7075), eyelets still to be machined
- Switch band in place, shoulders and OD machined
- GPS helical and 70cm/430MHz Telemetry link antennae test fitted

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drew
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Re: Avionics bay for HPV4PoC

Postby drew » Mon Jul 20, 2020 2:16 pm

This AV bay is GORGEOUS. Well done d00d.
Andrew Hamilton
AMRS 28 L3
AMRS Records Committee Chairman
Max Alt AGL - 26,850ft - L935 - THUNDA 2019
Max V - 3,004 ft/s, ~Mach 2.67 - L935 - THUNDA 2019

strud
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Joined: Thu Oct 02, 2008 7:37 am
Location: Central Tablelands, NSW

Re: Avionics bay for HPV4PoC

Postby strud » Tue Sep 15, 2020 1:42 pm

Finally found some time to get back onto the avionics bay so mounted it up into my mill on the rotary axis so I could more easily hold it exactly as required and drill mounting holes accurately for the boards and batteries etc.

Overview of bay without cover tube in the rotary axis and smart power switch installed

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Planning to mount as many of the batteries in this quadrant as possible, at least the flat/prismatic type.

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I have bonded in a blank RocTrak board to act as a mounting platform for a RocTrak module. The centre was milled out to allow the housing of a 3800mAh 18650 cell.

Planning to put some aluminium filled epoxy on the backside of this behind the mounting holed and tapping this for the mounting screws to fasten into.

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Showing what the orientation of the RocTrak module will have

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strud
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Joined: Thu Oct 02, 2008 7:37 am
Location: Central Tablelands, NSW

Re: Avionics bay for HPV4PoC

Postby strud » Tue Sep 15, 2020 3:06 pm

and almost forgot, another sector allocated to a FarTrak module (digital modem link, baro + accelerometer + flash storage on-board with support for external IMU via I2C expansion port)

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This runs a UBLOX gps module and dsPIC uC and 1W digital modem hence a totally different beast to the RocTrak module. However, very similar functionality but not compatible with any 'stuff out there' ie totally bespoke protocols etc but much more energy efficient since packet transmission times are super short.

Want to allocate space to a camera somewhere, still working on where that will go. Have ordered one of the bare modular split units:

https://shop.runcam.com/runcam-split-3-micro-and-split-3-nano/


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