A few weeks ago Brett Binnekade put a catapult launch system http://diydrones.com/profiles/blogs/skwalker-x8-catapult on here for his X8 that worked pretty well. I value my fingers and arms and decided to make something along the same lines. I give full credit to the orginal design.to Brett.
I used the same general layout and tried several times to get a joint to work reliably to enable the ramp to brake down into 2 sections so it will fit in a normal car. The method I use now works very well.
The other problem was the stiffness of the trolley, the design I now use is much stiffer and reliable.
I used more elastic which is now over pulleys to get a longer pull and a stopping system for the trolley to avoid smashing the trolley into the end stops at the top of the ramp.
The final result can be seen in operation at http://youtu.be/Eobl_iSa_cs The ramp has operated more than 100 times with no failures and the launches are very repeatable and positive..The catapult and cradle can be modified for most aircraft up to 6-7kg.
That works really well, what a nice smooth action, especially the stopping system.
Any chance that you could post up some shots of the improved component parts for us please.
The main improvements were to the trolley which now uses a thin centre plate and box sections to support the pins for the bearings. This prevents the frame flexing and the bearings moving away from each other due to the launch stresses.
The bungee also goes over pulleys down to the bottom of the ramp . this gives a steady pull along the total ramp.
you can also see the attach points for the restraining cords used as a brake, This is stretchy polyester cord. with a spring at the bottom.
The trolley is shown at its resting position , the black marks on the masking tape show how the brake cords stretch during the launch before stopping the trolley before it hits the brackets at the top of the ramp. The ramp has a new bracket at the top for the mounting of the pulleys and a locking device for the legs, The leg angles are also reduced.
This other picture shows the attachpoints at the bottom of the ramp with the shock springs.
When the launch is set up the 2 springs hang down vertically with the cords loose on the ground, As the trolley gets near the top the cords tighten and lift the springs horozontal, this starts the plane to slide off the trolley a moment before the trolley stops as the springs stretch.
The Catapult produces approx a 3-4 G acceleration and the plane leaves at about 25mph in a good flying attitute , then I start the motor and climb out.
Main benefit. I can still count to 10 at the end of a flying day, I dont strain my shoulders trying to throw this plane and the model does not get damaged by a crappy launch, everything is MUCH more predictable and safer,
The Catapult will fold up and go in the back of a small car (ford Focus) very easily and takes about 5 minutes to set up.
You can also see more detailed pictures of my trolley on Brett's original posting at http://diydrones.com/profiles/blogs/skwalker-x8-catapult ,
They were the early pictures of the modified trolley. The current one has some minor improvements as you see in the test video at http://youtu.be/Eobl_iSa_cs
I also tested a much heavier aircraft on the same catapult with worked well with no problems, this plane was approx 1.5kg and launched with no motor running.. this system will launch a 5-6kg plane with the motor assisting takeoff., The bungee presently is 1/4inch but would be upgraded for a larger plane like a loaded X8
Thanks for the additional info, I am currently reading through it and the original posting, it's the best portable system that I've seen.
Thanks for that. it took a lot of work to get it to this stage.
This will soon be available after some more testing) as a complete item (ready to use) from our website OR as a short kit (everything made except the long sections of Aluminium .) All parts are being laser cut with jigs for drilling the long sections, this is to save on shipping costs.
This will feature the new joining system for relaibility and the carriage cradle can be made to suit your aircraft. Made to order. (2-3 weeks)
Thanks even more so considering that it's a commercial venture for you. Do you have a link to your website please.
Any website link yet?
Hi Martin / Dennis
Its coming. Sorry for the delay due to launch in 10 days .. New modifications being tested on the carraige to operate with the difficult planes (like the X5 ) where the motor cannot run because the pushing mechanism gets in the way. The people with the X8 will also like this.
i want to buy one
If you plan to sell you catapult, 'll be interested to buy one.
Please, could you let me know when your website will be ready.
Any news about this nice project ?
Do you have a link where we could order your catapult ?
Hi Arnaud and Kevin
The Catapult has progressed over the last few months and is now available in 2 forms.
The original that we designed is available and works very well but we decided to restrict it to UAV's below 2.5Kg (like X5 etc. )
The 2nd version we now make is for the larger UAV's such as the X8, it is a heavier duty unit and has interchangable cradles for different aircraft including some tractor aircraft with nose mounted motors.
They are available on www.air-vision-air.com or sales@air-vision-air will bring you more information.
The website is being updated later this week.