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Melliandra
2nd Feb 2006, 14:28
Hey all, not sure where this thread should go so feel free to move it if you're not happy with the positioning.

As a design project at uni my group and I are supposed to design and build a launcher for an "unmanned air vehicle". The vehicles, JP Bullet II, wingspan 1.16m, wing section RG15, of masses 0.6kg, 1.0kg and 1.4kg have to be launched at 5m/s, 6.5m/s and 7.5m/s respectively at angles of 10, 20 and 30 degrees to the horizontal. We have 30min to complete 6 launches (combinations drawn from a hat) with only one person opperating at a time.

We're not allowed chemical propulsion or "glider" launching designs but everthing else, to a certain extent is fair game.

We've come up with cross bow designs, pneumatically propelled designs and a few more that have been discounted.

Just wondered if the brains on here could come up with anything? I'm not looking for anyone to do my project for me, just though people might like to bounce around ideas.

For instance on researching rail gun techniques it was found we'd need a capacitor with plates the size of a football pitch to produce enough current. (as you may have guessed we only looked at that one for a bit of a laugh, which is what I hope you guys will do)

UniFoxOs
2nd Feb 2006, 15:31
How about a slope and ramp arrangement like the ski-jumpers use?

Jerricho
2nd Feb 2006, 15:41
Why not make it look like a helicopter............they're so ugly the earth repels them.

GearDown&Locked
2nd Feb 2006, 15:55
Try a catapult system, something similar to the ones used on aircraft carriers... or something like a crossbow conected to a guiding rail. Lots of instant mechanical energy for your lightweight UAV.


GD&L

Onan the Clumsy
2nd Feb 2006, 16:04
Just use a catapult like they do with RC sailplanes and maybe real ones too for that matter. Search for Hi(gh) Start I think.

Failing that they do winch launches and auto(mobile) tows in the sailplane world. You could look into those.

We're not allowed ... "glider" launching designs but everthing else, to a certain extent is fair game. Ah! :(

Does an X15 type launch count?



...sounds like way more fun than my useless university :yuk:

G-CPTN
2nd Feb 2006, 16:17
Bungee elastic?

Melliandra
2nd Feb 2006, 16:17
Haha, I like the helicopter comment Jerricho, you know... it just might work!!

Unfortunately if you're thinking of an X15 air launch, our budget is 300, though it'd be fun to try to make some form of scrap heap challenge B-52!

Do you mean the electromagentic catapult system used on air craft carriers? Isn't that fairly similar to a rail gun?

By glider I meant any kind of zip wire/winch launch, since the unit has to be self contained, so it ruins the idea of running out a wire infront had to be dismissed. Damn it.

G-CPTN
2nd Feb 2006, 16:20
Do you mean the electromagentic catapult system used on air craft carriers? Isn't that fairly similar to a rail gun?

Earlier (American) Carrier Launch-catapults were steam powered.

Gainesy
2nd Feb 2006, 16:34
They still are.

How about booster rockets?


.

Melliandra
2nd Feb 2006, 16:44
Ok... may have been getting a little ahead of myself with the ol' eletromagnetic catapult systems...

Rockets burn fuel and thus use a "chemical" reaction. They muttered something about "health and saftey" when we queried that one.

G-CPTN
2nd Feb 2006, 16:44
How about booster rockets?

Non-chemical booster rockets . . .


Bloody big springs?

Melliandra
2nd Feb 2006, 16:52
I've been thinking.... how about one of those wind up toy car designs... you know, you pull it back and it shoots off up a ramp?

G-CPTN
2nd Feb 2006, 16:53
Ah! A clockwork UAV?

Melliandra
2nd Feb 2006, 16:56
Sounds like a plan, those little cars go blooming fast, wonder if they'll reach the neccessary velocities!

Solid Rust Twotter
2nd Feb 2006, 17:27
Boiler and piston. Regulate with a restricting valve and Bob's yer Aunt Mavis after the accident.

RiskyRossco
2nd Feb 2006, 17:29
A thought springs ( heh-heh. . . that wasn't a pun, bluey) from my clay pigeon/grousing days.
How much would a clay target launcher go for these days? Should be simple enough to rig a slotted rail to facilitate linear vectors. If memory serves yers can adjust spring output, for variable launch trajectory.
Thoughts from the Armaments and Design Bureau, Antip-sur-Lac.

tony draper
2nd Feb 2006, 17:36
Potassium Permaganate and Conc Nitric Acid,good enough to propel a UAV London wards from Peenamunde.
:)

Solid Rust Twotter
2nd Feb 2006, 18:01
That would be chemical, Herr D.

Container with small aperture as propellant nozzle. Half fill with water then pressurise with nitrogen or compressed air. Reaction of water being expelled should drive the launcher up a rail and speed can be regulated by pressure of gas in container.

Onan the Clumsy
2nd Feb 2006, 18:17
Yeah, check the JB archives. Someone posted a link to a video not too long back regarding someone who pumped air into a two litre coke bottle and then let it rip. It went a very respectable distance too.

Jerricho
2nd Feb 2006, 19:02
=Onan the Clumsy regarding someone who pumped air into a two litre coke bottle and then let it rip.

:uhoh: :ooh:

airship
2nd Feb 2006, 19:13
Hmmm, I think I'd go for a compressed air system too. Tank, regulator, precision needle valve, single-acting spring-return cylinder etc. Head for yer nearest pneumatic equipment supplier for a chat. The whole launcher could be quite compact. And the budget might go further in exchange for some sponsorship? :O

RatherBeFlying
2nd Feb 2006, 21:26
Scientific American ran an article some years ago by a gent who erected a trebuchet on the back forty -- and used it to launch junkyard cars into the air.

Should be in the library, but you may want to scale it down;)

av8boy
2nd Feb 2006, 23:00
Trebuchet! That's what I was going to suggest! How very French or British or something...

Or a potato cannon (not very French or British I'd think). I've built a couple of those with my son. Not the sort that involves fire, mind you, but rather, the sort that uses compressed air. For the trigger we used 9 volt batteries wired to electric sprinkler valves. (The bit on the left is the anti-siphon valve. You don't need that part)

http://www.toro.com/sprinklers/images/v_53764_lg.jpg

We used a bunch of these valves because they don't open instantly, and they have only a 1 inch diameter. We stored the pressurized air in larger "schedule 40" PVC (we used schedule 40 for everything), and then came out of those pipes with a manifold made up of several 1" pipes. When we pushed the button, the valves opened and the large storage pipes emptied very quickly. The valves were on sale at the local home improvement warehouse for less than US$10 each, so it wasn't a bad deal.

We also made note of the component with the lowest safe PSI rating (one of the larger-diameter PVC pipes) and installed appropriately-sized pressure relief valves on the manifolds, on the high-pressure side of the trigger valves. If you do this, don't just tap into the pipe and try to thread the safety valve into the side of it. Rather, use in-line reducers to bring the size of the pipe down to the size of the release valve to ensure a snug fit.

Also make certain that you install pressure gages on the manifolds so you can keep an eye on the pressure as you fill the device.

Above all, set it up so that you don't have to be near it when you're filling and firing it, in the event it blows up. We set it up in the back of my truck in an enclosure and then ran several hoses to a safe location where we could operate the compressor. The hoses held the pressure gages and also were the means by which the thing was filled (separate hoses for each pressure gage and each filling location). That way, if the thing blew up, we'd be no where near shattered PVC. In your case, I'd suggest you set the aircraft in the mechanism, then back away to pressurize and fire the device.

Personally, I like this solution because you can vary the amount of energy by varying the amount of pressure you introduce into the system, and further by firing a different number of trigger valves. And building the cannon in a "T" shape (with the storage pipes at a right angle to, and at the base of the barrel) will lend itself nicely to changing the elevation.

Just a thought. I'd be happy to contribute a drawing...

Dave

PS The schedule 40 spec is here (http://www.harvel.com/downloads/spec-pvc-pipe-sch-40.pdf)

airship
2nd Feb 2006, 23:32
My apologies, I omitted to fully address all the requirements, especially the 10 to 30 'inclination to the horizontal' issue. And you didn't specify whether the firing would be from a static or moving platform. Looking at the exercise from a 'real World' standpoint, it would be interesting nevertheless to incorporate the moving platform element. What I'd suggest is getting hold of a Challenger main battle tank and adapting the turret to suit. The only difficulty I forsee is that you'd still only have a platform which stabilises 360 horizontal but only -10 to +20 in the vertical. A few solid wedges could come in useful... ;)

kms901
3rd Feb 2006, 00:53
Awful thing to say to a modern student, but how about thinking for yourself and coming up with an original idea ?

broadreach
3rd Feb 2006, 01:39
Melliandra,

Am I confused or have you neglected to say what the UAV is supposed to achieve? Longest time airborne? Highest altitude?

Re the launchers, they're called bottle rockets. Made out of PET coke bottles with glued-on fins. Google "bottle rocket" for all the latest gen, clubs you can join etc. Trouble is, the acceleration of anything like that is likely to rip the wings off your glider (if in fact that's what the UAV is), if it doesn't just loop ten feet off the launch pad and come crashing down in a balsa blizzard. But maybe the pressure could be regulated just right....

Hope you post the clips on Pprune.

Melliandra
3rd Feb 2006, 09:58
Awful thing to say to a modern student, but how about thinking for yourself and coming up with an original idea ?

You'll be suprised to hear that after weeks of research we had already come up with most of those proposed. We have already narrowed down our options to two designs. I was hoping that people would enjoy looking at the challenge I was facing and in that I might pick up a few ideas that we maybe hadn't thought of.

I'm sorry if you thought I was loafing but I actually do work at uni, I'm on the toughest engineering course at a red brick uni, so please, get off my back (not really elequent enough for pprune but don't have another way of saying it) and while you're at it you can design a sustainable refrigerator for another project I've got?

tony draper
3rd Feb 2006, 10:50
When you solve the Vehicle laucher problem you still have to figure out another launcher system on the UAV itself, for err Hellfires and such, a couple Mk 84 might be a tad heavy for your platform.
:E

cyclicmicky
3rd Feb 2006, 10:58
[QUOTE][Why not make it look like a helicopter............they're so ugly the earth repels them./QUOTE]
Not all of them...

http://i8.photobucket.com/albums/a30/Mickpeake/helipicsjosh005.jpg
This ones a serious good looker:ok:

Jerricho
3rd Feb 2006, 11:34
Sorry Micky, but if it looks like crap, smells like crap or is even remotely related to crap............you get the idea. :E

(Apart from the helicopter from Airwolf. Airwolf was cool with them big rockets and stuff that it blew up and machine guns and stuff. Stringfellow Hawke wasn't cool, he was a [email protected] in a David Caruso kinda way.)

ExSimGuy
3rd Feb 2006, 11:58
Elli- Really surprised at the "quality" of responses that you got! When I first saw your post I thought "on JB? - the guy must be joking!"

Cyclic Mick - what's the "launch ramp" under the chopper for? Or is it an autogyro ;)

Elli - got me thinking, 'specially when I saw "bottle rockets" mentioned. As today is "Sunday" in my part of the world, I did some surfing, got diverted (as usual) and ended up reading about "chem-powered" bottle-rockets.

Wasted half of my day off reading abouit bottle-rockets and decided to try one out. Plastic "pop-bottle" with kitchen roll soaked in petrol inside, cardboard fins, took it to the top of the "Wadi" above the golf course 3rdhole, set a "fuse" of petrol-soaked kitchen roll, and lit - ran!

Total Failure! Probably too rich a mixture inside the bottle. Burned okay - first the fins, then the bottle itself, and finally the "fuel". Neverleft the "launch pad" except to fall over when the bottle melted!

Okay - gonna be "MK2" next weekend!

Kms901 - Isn't it called "research"? I'm sure he wasn't looking for detailed drawings and formulae - just some ideas to start with! The fact that the liniear motor idea had already been investigated shows that.

Elli - Hopefully you wil be able to post the results. Successful or not, they will add to "man's store of knowledge"! Good luck;)

Taildragger55
3rd Feb 2006, 12:05
I remember reading that the first Israeli UAV was deployed from a VW minibus using bungee cords.

cyclicmicky
3rd Feb 2006, 12:07
ExSimGuy We built a platform on some steel runners...similar to a trains rail system, so we can land on it and then push the helo into the hangar nice and easy. And then we don't have to have those horrible ground handling wheels on.
:ok:

Melliandra
29th Apr 2006, 16:08
Reviving a forgotten thread to follow up how our project went...

Our launcher used two bungees extended approximately 100% to pull a cradle holding the UAV up a launch ramp. The release and cradle stopping system was a fishing reel threaded with 4 40lb lines.

Yesterday was launch day. Our launcher came in at a weight of 140N (extra credit given for being under 245N), a compacted volume of 0.20m^3 (extra credit given for being under 1m^3). It cost just under 200GBP to build (extra credit given for being under 300).

It took two people 8min47sec to put it together from it's compacted state and the 6 launches took 14min to complete, each within the 10% tolerance.

Here are some pictures of our and other group's efforts:
http://www.geocities.com/zulu300_2000/designpics.htmlhttp://www.geocities.com/zulu300_2000/P3200006a.JPG
Building stages
http://www.geocities.com/zulu300_2000/ourdesign.htmlhttp://www.geocities.com/zulu300_2000/P4280005a.JPG
Our design
http://www.geocities.com/zulu300_2000/launch.htmlhttp://www.geocities.com/zulu300_2000/P4280006a.JPG
Launch
http://www.geocities.com/zulu300_2000/group1.htmlhttp://www.geocities.com/zulu300_2000/P4280043a.JPG
Group 1 design (weight dropping pulls cart up)
http://www.geocities.com/zulu300_2000/group2.htmlhttp://www.geocities.com/zulu300_2000/P4280011a.JPG
Group 2 design (4-pulley system winched from underneath) Group 3 in background
http://www.geocities.com/zulu300_2000/group3.htmlhttp://www.geocities.com/zulu300_2000/group3.htmlhttp://www.geocities.com/zulu300_2000/P4280063a.JPG
Group 3 design (2-pulley system winched from top as with our design)

Both lecturers and students were pleasantly suprised with the results and as an un-marked exercise at the end we had a competition to see which could launch the lowest weighted aircraft furthest. It was best out of 3 and though our launcher went the furthest on the first of the 3 launches it was far exceeded by group 2's launcher when they added a further 6 lengths of bungee to their original 4!

Jerricho
29th Apr 2006, 16:40
So, what did you name it?

Maybe Jerricho............huge expectations but fails to deliver?

Melliandra
29th Apr 2006, 16:46
Well we were quite unimaginative... Our group reduced from 6 to 4 in the first few weeks... So our group was called "The Foursome". As the only female in the group the sexual connotations weren't all that appealling.

However I think Group 2 called theirs "Rape and Pillage"... No, I don't get it either, I think it stems from their original trebuche idea.

G-CPTN
29th Apr 2006, 16:46
Congratulations, Melliandra, and thanks for the update.
Sounds like, not only did you have fun, but you did well too! :ok:

Jerricho
29th Apr 2006, 16:54
You could have named it G-CPTN..........dunno if you could get it up!! ;)

(Good on ya Mel :ok: )

G-CPTN
29th Apr 2006, 16:56
You could have named it G-CPTN..........dunno if you could get it up!! ;)
I've HAD my 'moments' . . .

ExSimGuy
29th Apr 2006, 18:26
And congratulations from me too - thanks for coming back and telling us all about it.

My "bottle-rocket", well the project got sorta forgotten. But now I'm fired-up (pun intended!) and the next weekend I'm at home, I'll be back up above the 3rd tee on the golf course, trying to get "MKII" to actually leave the "pad";)