Vertical Trajectory System (with some 3D printed parts)

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SpaceManMat
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Re: Vertical Trajectory System (with some 3D printed parts)

Postby SpaceManMat » Wed Oct 25, 2017 5:25 pm

OverTheTop wrote:
You planning to have cameras setup so you can monitor actual movements?


Not at this stage, but it would not be too difficult to tape a couple of 808 keychain cameras to the airframe. I will see what happens between now and launch.


My though is that video appears to be a very good tool for analyzing performance, especially when things go wrong.
QRS: 124
AMRS: 32 L2 RSO
Highest Altitude: 10,849 feet
Largest Motor: CTI 1115J530 IM
Current Project: X Wing

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OverTheTop
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Re: Vertical Trajectory System (with some 3D printed parts)

Postby OverTheTop » Thu Nov 16, 2017 6:58 am

Airframe Integration
With the completion (sort of) of the main assembly, time to integrate it into some fiberglass airframe.
I had some 4” airframe sitting around so I pressed that into service for this module. It was just about the perfect length to start with!
A bit of measuring and thinking and CADing, then the 3D (FDM) printed drilling guide was slid over the tube. The 35mm holes were drilled using a hole saw, and the pilot holes for the mounting screws drilled. The mounting holes were drilled out to final size and countersunk after the drill guide was removed.
DrillGuideresize.JPG

DrillGuideDrilledresize.JPG


The edges of the holes in the filament-wound fiberglass ended up with some loose filaments of f/g around the edges so they were glued with the usual Loctite 401 and then taken to the final size and dressed lightly with emery cloth.
The airframe was a bit longer than needed and had a test hole I had drilled in earlier that had to be amputated. I dropped it into the lathe and attempted to use my dental drill as a toolpost grinder. Progress was a little slow so I switched to using the cordless angle-grinder and made a nice clean cut.
Shorteningresize.JPG


A length of coupler was inserted in to the correct depth and glued in with the usual West Systems 105/206.
Holes were drilled at the top to accept the NC and at the bottom to mate to the Velociraptor I am using as the test-bed for this project.
A coat of plastic primer and white paint tarts it up a bit. I will add some decals as a roll pattern sometime before launch.

To close out the bottom of the assembly to the parachute compartment from the ejection gases I took to SolidWorks and sketched up a bulkhead incorporating an O-ring, connectors for battery charging, eMatch connections, charge canisters, and breakwire for switching off the VTS when ejection occurs. This was printed in “flexible” material on the SLA printer.
BulkheadCAD1resize.png
BulkheadCAD1resize.png (235.42 KiB) Viewed 188 times

BulkheadCAD2.png
BulkheadCAD2.png (124.58 KiB) Viewed 188 times


Charge canisters were machined up to suit and the wiring connections to extend the interface to the VTS module were fitted.
BulkheadAssembled1resize.JPG

BulkheadAssembled2resize.JPG


The bulkhead was fitted to the coupler on the airframe. There was a bit of shrinkage on this 3D printed part (the flexible material seems to suffer from this problem) so the diameter was boosted a little with some Kapton taped wrapped around the boss. Also, the holes were drilled in the fiberglass airframe and the bosses in the bulkhead were drilled, tapped, and fitted with Recoil thread inserts to hold the bulkhead in place
BulkheadInAirframe.JPG

AirframeWholeresize.JPG

So that is the completed airframe, sans VTS module, and also yet to be fitted with an M6 eyebolt to tie everything to the recovery harness.
TRA #13430
L3
"Everybody's simulation model is guilty until proven innocent" (Thomas H. Lawrence 1994)

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SpaceManMat
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Re: Vertical Trajectory System (with some 3D printed parts)

Postby SpaceManMat » Thu Nov 16, 2017 7:36 am

Looking very nice, I do like the use of that drill guide. Can’t wait to see the final result.
QRS: 124
AMRS: 32 L2 RSO
Highest Altitude: 10,849 feet
Largest Motor: CTI 1115J530 IM
Current Project: X Wing

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OverTheTop
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It's only money...
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Location: Melbourne, Australia

Roll Pattern

Postby OverTheTop » Sun Nov 26, 2017 10:00 am

I have added a roll pattern to the airframe section. This will help determine roll attitude if anyone gets sufficiently good pics during operation. Two rectangles of 3M vinyl decal material were cut to size and applied to the airframe. I decided to use a two-bit Gray binary code to encode the rotation in images. Simple and effective.
https://en.wikipedia.org/wiki/Gray_code

I thought about higher resolution (more bits) but I think it would be superfluous. Bigger squares are more easily resolved in photographs anyway
RollPattern.JPG


I suspect the pattern is purely cosmetic at this stage. I will let you know after the flights if I got any value from it.

The airframe in this pic has been fitted with a dummy servo hub (3D printed) and non-flight fins printed on the SLA printer. This allows this section to show what flight configuration looks like, and still lets me work on the internal module on my bench.


I am now looking at making two (four?) housings to hold keychain cameras to record the fins during flight. Stay tuned...
TRA #13430
L3
"Everybody's simulation model is guilty until proven innocent" (Thomas H. Lawrence 1994)

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SpaceManMat
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Re: Vertical Trajectory System (with some 3D printed parts)

Postby SpaceManMat » Mon Nov 27, 2017 9:12 am

Are those one piece printed fins? It looks like you have a rod up the middle.
QRS: 124
AMRS: 32 L2 RSO
Highest Altitude: 10,849 feet
Largest Motor: CTI 1115J530 IM
Current Project: X Wing

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OverTheTop
It's only money...
It's only money...
Posts: 2457
Joined: Sat Jul 21, 2007 2:20 pm
Location: Melbourne, Australia

Re: Vertical Trajectory System (with some 3D printed parts)

Postby OverTheTop » Mon Nov 27, 2017 11:43 am

They are SLA printed fins. There is provision for a rod up the center to hold it onto the servo spline and flange, but I will likely not make the required bespoke screws for this. Mechanical strength testing in the next few months will tell me if strength is sufficient. I expect it to be. A screw rod up the center will increase the resonant frequency a little but I don't expect flutter with the design as it stands in relation to the expected flight envelope.

The fins above are not expected to be flight fins.
TRA #13430
L3
"Everybody's simulation model is guilty until proven innocent" (Thomas H. Lawrence 1994)

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SpaceManMat
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Posts: 1889
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Location: Brisbane

Re: Vertical Trajectory System (with some 3D printed parts)

Postby SpaceManMat » Mon Nov 27, 2017 12:14 pm

Snapping a fin on landing may be preferable to damaging the servo.
QRS: 124
AMRS: 32 L2 RSO
Highest Altitude: 10,849 feet
Largest Motor: CTI 1115J530 IM
Current Project: X Wing


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