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Vulture 2 autopilot reports for duty
As you can imagine, it's all go here at the Special Projects Bureau's mountaintop headquarters ahead of the imminent arrival of the Low Orbit Helium Assisted Navigator (LOHAN) team. Click here for a bigger version of the LOHAN graphic Blokes in white vans have been bowling up to the door for the past month, their couriers' …
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Monday 9th September 2013 12:02 GMT Charles E
Reprogramming
We have been discussing your flight systems elsewhere on the web, and I propose that you program your flight a bit differently and equip it with a payload other than the Vulturenaut.
Instead of launching the rocket at the highest balloon altitude, you should just drop it. Then let the autopilot systems glide it to the ground target. When the aircraft is within visual range of the target, fire the rocket, and detonate the C4 explosive payload with a proximity fuse when it hits the target. This would be like an Exocet cruise missile, it would speed up as it approached the target so it could not be shot down.
Then maybe you'll realize this isn't a toy and you are building a prototype cruise missile weapon.
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Monday 9th September 2013 12:17 GMT squigbobble
Re: Reprogramming
It's only cruise missile if it's got a warhead, otherwise every autopiloted plane would breach the Missile Technology Control Regime. Also, there would be aerodynamic issues with trying to get a glider airframe to go at missile speeds which aren't such a problem when you're using the rocket to thrust the aircraft upwards in which case much of the energy is going into increasing its altitude and not its speed.
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Tuesday 10th September 2013 11:42 GMT Charles E
Re: Reprogramming
The speed issue is trivial when it is dropped from above. You can name the aircraft after a bimbo and carry a toy as a payload, but it's still a standoff missile, and far more sophisticated than the guided glider bomb that sank HMS Egret.
Did anyone check with the MoD to see what they think of this project?
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Tuesday 10th September 2013 13:30 GMT M Gale
Re: Reprogramming
What have the MoD got to do with it?
Not sure, but this is the same person that suggested turning LOHAN into a conventional rocket. Uhm, while completely forgetting the "autopilot itself back to base" part of the mission.
I guess building missiles is okay, but sticking wings on them isn't.
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Tuesday 10th September 2013 16:00 GMT Sir Sham Cad
Re: Reprogramming
"Did anyone check with the MoD to see what they think of this project?"
Given that this has been fully registered with the relevant authorities in Spain where it will be assembled and launched and landed and, given that this project has been slathered all over El-Reg for a couple of years now with full disclosure of the contents of the payload on the Truss and Vulture 2 aircraft as well as details of the rocket motor, anticipated launch altitude and respective motor control and cut-down mechanisms all combined with the fact that no black helicopters or blokes with sharp suits and regulation sunglasses have appeared at either Lester's gaff or any of the well advertised co-conspirator organisations I'd say the MoD don't give a flying fuck in a high wind about it.
Next!
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Monday 9th September 2013 12:43 GMT M Gale
Re: Reprogramming
Then maybe you'll realize this isn't a toy and you are building a prototype cruise missile weapon.
And it should be banned, am I right?
Congratulations. Now law abiding people can't make automated toys. The sort of people interested in building explosive UAVs on the other hand, can continue to do so as they have been able to for years.
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Monday 9th September 2013 12:28 GMT Don Jefe
Pushrods!
One of the guys in my R/C club has an APM system in his 'park drone', it's nice kit.
About the threaded pushrods and control horns: Behind loss of signal or running out of fuel/battery power having the pushrod come loose from the connector on the control horn is one of, if not the, most common failure in high stress R/C aircraft.
Before final assembly slide two pieces (assuming the pushrod is threaded at both ends. If one end not threaded you only need one) of heat shrink tubing onto the pushrod.
After assembly and fine tuning put just a drop of CA glue where the pushrod threads into the control horn connector (don't use too much or it will be impossible to make last minute or emergency adjustment).
Afterward slide heat shrink over the base of the connector and shrink it. As simple as that and you've effectively eliminated control rod connector failures and now have redundant linkage systems with no real weight penalty.
Also: If the Rx or your version of the APM has removable components (crystal or freq module) cover them with electrical tape if you aren't already. You can CA them in as well if you've got concerns about cold temps or violent flight making the tape ineffective. That's what I do on my turbine models and helicopters and I haven't lost one yet to connection failure. Seen it happen though, never ends well.
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Monday 9th September 2013 12:59 GMT M Gale
Re: Pushrods!
Also: If the Rx or your version of the APM has removable components
They're using a 2.4ghz setup. These things tend to hop around the band hunting for empty frequencies, which removes one of the other killers of 35Mhz gear: Interference on your chosen frequency (you also remove the loose-crystal risk for free).
Though personally I prefer Spektrum over Futaba for that stuff. Something about using two frequencies and having dual linked redundant receivers appeals to the geek in me.
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Monday 9th September 2013 14:47 GMT imanidiot
Re: Pushrods!
Fortunately, when it comes to range there is already quite a lot of experimentation from the FPV flyers out there. Most still use a beefed up 35 MHz system, but AFAIK some have started using 2,4 GHz systems. The advantage is because 2,4 GHz is already a widely used frequency, there is a lot of amplifier and directional antenna stuff readily available. I'm pretty sure an off the shelf Yagi is already available to connect directly to the transmitter.
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Monday 9th September 2013 15:30 GMT PC Paul
Re: Pushrods!
One thing to watch out for is that the failsafe which kicks in when the 2.4GHz kit is out of range doesn't do anything nasty to the autopilot, like turn it off. DAMHIKT.
For servo arms and pushrods I favour making an L bend and threading the bent bit, then tapping the rod into a too-small hole in the arm. Because the arm only moves over less than 180 degrees it cant come unthreaded, but there is very little slop and a lot of resistance to the end pulling out sideways. I've tested this on a lot of combat wings - it can take a beating and stay attached.
With a bit of your low temp grease it should be immune to freezing too, which a ball joint might not be.
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Tuesday 10th September 2013 14:52 GMT Jess--
Re: Pushrods!
Most 2.4 ghz systems I have come across react to loss of signal by setting the throttle below 0 (ensuring that any engine / motor is shut down) and if set the receiver puts all other controls to a pre-programmed failsafe position, on my aircraft its set to bank slightly to the left and trimmed to glide as slowly as possible (it worked perfectly when I fell in a lake complete with tx)
the apm system that el-reg has gone for uses this signal to trigger whatever its programmed to do (Return to Base, circle over position etc)
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Tuesday 10th September 2013 16:04 GMT Rob Crawford
Re: Pushrods!
If using a spektrum receiver you would want to use Preset Failsafe rather than the default Hold Last Command failsafe mode.
With my APM 2.5 RTL (return to launch) is triggered on signal loss providing Preset Failsafe is used (otherwise the bugger simply lands wherever it happens to be)
Can't speak for Futaba kit as it's too expensive for me
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Monday 9th September 2013 13:05 GMT Ottman001
Re: Pushrods!
All good points. The radio shown doesn't have crystals so need to worry about that. I would use thread locker rather than CA on ball links because a mistake is a permanent mistake with CA.
To add to Don Jefes list of common problems, do not mix the arms for Futaba and Spektrum servos. I can't remember off hand if Futaba and Spektrum are actually close enough not to notice when fitting but where the wrong type of arm is used, it can appear fine in preflight checks but jump splines under load.
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Monday 9th September 2013 13:44 GMT Don Jefe
Re: Pushrods!
Mistakes with the CA?? This is a Space Mission man! There's no room for error!
Seriously though, I always use CA, as a holdover from when all my models were nitro or gasoline. Nitro fuel and exhaust destabilizes most non-permanent thread locker and most of the permanent thread lockers are 100% CA anyway (some brands may coloring agent added). But you are correct, thread locker should be fine above -65•F.
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Monday 9th September 2013 15:04 GMT Don Jefe
Re: Pushrods! @graeme
The pushrod isn't turning. The connector on the end of the pushrod is often made from nylon or soft metal with very fine threads that allow the pushrod to pull out under stress or if it becomes bound. Sort of like unzipping a zipper. Even moving out a few threads completely changes the throw of the control surfaces. They are also prone to splitting under high load and/or cold temperatures. There are stronger metallic options but they're a whole different ball of wax.
A locknut would not prevent the connector itself from failing. You'd just have a pushrod flailing about with a locknut on the end :)
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Tuesday 10th September 2013 15:56 GMT Rob Crawford
Re: Pushrods!
Threadlocker isn't CA
Although they are from the same family they are not one and the same.
BTW one of the reasons that threadlock tubes are deliberately almost empty is because it will spontaneously harden if there is no air in the bottle, in the case of CA it's water that will cause curing.) Electrochemical reactions also causes threadlock to cure (also unlike CA)
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Monday 9th September 2013 13:32 GMT Don Jefe
Re: Ready made module???
You can call it leveraging the inherent advantages of a horizontally integrated critical systems supply chain with a focus on fiscal responsibility and technical excellence while addressing the needs of the flight management team, ground crew and operators. If it makes you feel better.
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Monday 9th September 2013 13:19 GMT Neil 38
Do you really need the APM 2.6 vs the APM 2.5? The 2.6 has an external magnetometer typically needed for multi rotor aircraft so that the amount of motors and ESCs they have don't interfere with the sensitive compass. The APM 2.5 has the magnetometer inside the main case and would give you a better option to use an alternate GPS unit if the need arose.
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