Avionics Sled with TeleMega

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OverTheTop
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Avionics Sled with TeleMega

Postby OverTheTop » Tue Jul 23, 2019 10:43 pm



Here is a few pics of a sled I put together, to replace the one that is still MIA after Thunda earlier in the year.

1.6mm G10 is the chosen material. It is long and skinny to make it suitable for use in 54mm airframes or larger. Holes were accurately drilled by putting the G10 in the mill and using the DRO to put holes in the correct coordinates. The TeleMega mounts using 4-40 hardware and threads tapped into the sled.
Top2resize.jpg

Aluminium pieces were turned and milled for the top and bottom allow for attachment hardware.

Two brackets are 3D printed in "rigid" resin. This is a glass-reinforced material that is quite stiff and dimensionally stable. The thickness on those webs is 2mm. M2.5 screws hold the brackets to the sled (tapped into the G10), and an M3 screw holds each microswitch in place, with rotation being prevented by a boss on each switch locating in the bracket.
bracketresize.jpg


Normally-closed snap action switches turn on the altimeter and also apply power to the pyro. RBF pins hold them off when inserted in the NC base. Switches are mounted orthogonal to the main axis to reduce the chance of bouncing a switch with flight or deployment events.
switchesresize.jpg

Wires go from the altimeter to two Molex Microfit 3.0 connectors. A 4way connector provides connection to the two deployment charges. A 6way connector provides access to the four additional pyro channels. These can be used to monitor voltages on other electronics further down in the rocket, reporting them back via telemetry.

Here it all is fitted into the 3D printed 4" NC base
InNCresize.jpg

The antenna is held off the PCB to maintain the electrical length of the antenna correctly by keeping mainly air around the wire. This is probably a minimal effect and probably overkill on my part. The change in length, whether close or removed from the G10, is likely insignificant.
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SpaceManMat
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Re: Avionics Sled with TeleMega

Postby SpaceManMat » Wed Jul 24, 2019 6:28 pm

Very neat, I take it the second switch is a shunt?

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OverTheTop
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Re: Avionics Sled with TeleMega

Postby OverTheTop » Wed Jul 24, 2019 7:47 pm

TRA #13430
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Voyager
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Re: Avionics Sled with TeleMega

Postby Voyager » Thu Aug 08, 2019 4:29 am

Very nice OTT! I might steal your design for my TeleMega. As you suggest, I doubt whether having the G10 dielectric plate will have much effect on the antenna efficiency. You’ll benefit more from the support it provides.
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OverTheTop
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Re: Avionics Sled with TeleMega

Postby OverTheTop » Thu Aug 08, 2019 12:16 pm

The entire length is under tension when assembled, so I could, theoretically, make the antenna end much skinnier.
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"Everybody's simulation model is guilty until proven innocent" (Thomas H. Lawrence 1994)


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