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Old Jan 10, 2013, 12:57 PM
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Skywalker X8 catapult

With the amount of equipment in my X8 is on the increase, so is the weight. Its becoming very difficult and somewhat dangerous to hand launch.

Iv decided to build a catapult. I dont like the idea of a bungee launcher because of the amount of flat space required. some places I fly dont have this.(eg: off a cliff =) ) I really wanted something self-contained and foldable.

a fellow RC groups member deTonaTor_NZ designed an amazing catapult for his X8. His catapult gave me the inspiration to build mine and the proof that its actually possible. See his video here

I only have basic tools at home and the whole build only required a drill, grinder, hacksaw and some hand tools.

The main beam is 50mm x 50mm aluminum 2m long.
The smaller square tube is 19mm x 19mm
The bearings are standard scateboard bearings.
I used 10mm latex tube for the bungee
The 2 loops together have a tension of 18KG and my X8 weighs 3.4KG.
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Old Jan 11, 2013, 11:16 AM
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FireFlyer451's Avatar
United States, CO, Denver
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brettbb,

Looks like a great design. I've seen CMS video and thought the same thing. An outstanding unit/design.

Will you post more photos, and build details for others to replicate? And do you have any launch videos yet?

Thanks!
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Old Jan 11, 2013, 01:57 PM
I don't do Normal
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What are you using to move the plate?
I just had some ideas and thought I would share them see attached sketch
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Old Jan 13, 2013, 05:01 AM
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I manged to finish my launcher over the weekend so I have uploaded the rest of the pics.

I am first going to try 2 Latex tube loops as shown in the pics. Im getting about 20 kg of pull. I think that should be enough as the motor will be running aswell. If not, Il add more loops and maybe stretch it over the front pulleys and back down down again like Pinky_d_brain's sketch.

I would have tested already but the weather is no good. Just waiting it out now... Will add videos as soon as I have them.

If you want a specific picture of something or more detail then just shout
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Old Jan 13, 2013, 03:44 PM
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brett,

Looks great, thanks for more photos. Looking forward to the videos.
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Old Jan 13, 2013, 04:30 PM
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The weather finally gave me a chance to test my catapult.

X8 catapult (1 min 45 sec)
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Old Jan 13, 2013, 06:20 PM
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how does your release work?
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Old Jan 14, 2013, 01:35 AM
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Quote:
Originally Posted by brettbb View Post
The weather finally gave me a chance to test my catapult.

http://youtu.be/asOPtRD_xgc
Perfect!

Just perfect......!
Pls get into more details.
I must make one.
Thanks for sharing

Sakis
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Old Jan 14, 2013, 03:59 PM
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I have added more details into the first post.

Quote:
Originally Posted by rotccapt View Post
how does your release work?
See attached images of the trigger release.
I basically riveted a 12mm x 12mm aluminum square inside the rail. The12x12 tube has a 6mm bolt through it which you can see exits through a hole in the rail.
The images should be self explanatory.

.
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Old Jan 16, 2013, 10:00 AM
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Can I make a suggestion that you add more tension to the bungee? The first launch looked ok, but on the other ones, it looked like the plane was on the edge of stalling based on how it sank just after leaving the rail. It would only take a small drop in the wind for the plane to fully stall.

I use a similar bungee stretched to 14 meters. The launches the plane, no matter were the wind is coming from.
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Old Jan 18, 2013, 02:24 AM
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Thanks for sharing this Brett!! I had a nasty accident in August when the prop hit my hand as I was launching my X8. I cut six tendons in my right hand and almost bled to death before I got to the hospital. After two surgeries I have permanent loss of partial movement to 3 of my fingers (I can no longer make a fist or close my hand all the way). Hand launching this plane is more dangerous than people think.

Anyway, I haven't touched my X8 since but have one of my employees building a catapult from your photos & notes. Thanks so much for sharing!
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Old Jan 18, 2013, 02:57 AM
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Awesome. It goes to show what you can do with simple hand tools. A very clean and simple.
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Old Jan 18, 2013, 04:35 PM
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Quote:
Originally Posted by DJEncore View Post
Thanks for sharing this Brett!! I had a nasty accident in August when the prop hit my hand as I was launching my X8. I cut six tendons in my right hand and almost bled to death before I got to the hospital. After two surgeries I have permanent loss of partial movement to 3 of my fingers (I can no longer make a fist or close my hand all the way).
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Old Jan 21, 2013, 08:51 AM
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Quote:
Originally Posted by ashdec87 View Post
Can I make a suggestion that you add more tension to the bungee? The first launch looked ok, but on the other ones, it looked like the plane was on the edge of stalling based on how it sank just after leaving the rail. It would only take a small drop in the wind for the plane to fully stall.

I use a similar bungee stretched to 14 meters. The launches the plane, no matter were the wind is coming from.
After watching the videos at home I also noticed how it dropped just after launch. I have since put the tension up to 22KG and it seems better. there is still alot stretch left in the bungee's though.

The tension will be different for everyone though depending on your X8 weight and power setup.

Mine weighs 3.4KG and is running on 4S at about 800W at WOT.

Quote:
Originally Posted by DJEncore View Post
Thanks for sharing this Brett!! I had a nasty accident in August when the prop hit my hand as I was launching my X8. I cut six tendons in my right hand and almost bled to death before I got to the hospital. After two surgeries I have permanent loss of partial movement to 3 of my fingers (I can no longer make a fist or close my hand all the way). Hand launching this plane is more dangerous than people think.

Anyway, I haven't touched my X8 since but have one of my employees building a catapult from your photos & notes. Thanks so much for sharing!
Sho! very sorry to hear that. Thats one of the main reasons I built the catapult. I once tried to launch the X8 myself on a windy day and its very difficult to balance the X8 on your finger tips with 13" prop spinning behind you were all it takes is a bit of a cross wind for it to go bad. Iv had guys launch it for me which is better but imagine your own X8 cutting your mates hand... not cool.

All the best with your recovery. Dont hesitate to ask questions during your build and please post pics when you are done =)

Quote:
Originally Posted by n-2-stuff View Post
Awesome. It goes to show what you can do with simple hand tools. A very clean and simple.
Thanks
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Old Jan 21, 2013, 11:25 AM
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United States, CO, Denver
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Brettbb,

Just a clarification question on the trigger release. Referring to your photos in #9, Is the release pin simply held in place by the tension of the pin against the launcher tray/plate? And when you push down on the extension sticking out of the end with your foot, it releases the launcher plate?

How is that foot release tube attached inside the larger, longer rail?

Thank you,
M
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