SMALL - espritmodel.com SMALL - Telemetry SMALL - Radio
Reply
Thread Tools
Old Feb 18, 2013, 02:20 PM
Registered User
THESANDMAN's Avatar
United States, NY, New York
Joined Oct 2010
1,680 Posts
Quote:
Originally Posted by tty044 View Post
I think I will make such device too. Do you have any licensing policy?
My main problem is getting latex 10mm tube. Is there any internet shop with it? I have found something here but the prices are insane...
Regards
Michal
check Hobby king they sell bungee cord .

its not the same but it wil work
THESANDMAN is offline Find More Posts by THESANDMAN
Reply With Quote
Sign up now
to remove ads between posts
Old Feb 19, 2013, 12:30 AM
An Aussie in Chicago
Joined Apr 2012
1,319 Posts
Quote:
Originally Posted by tty044 View Post
I think I will make such device too. Do you have any licensing policy?
My main problem is getting latex 10mm tube. Is there any internet shop with it? I have found something here but the prices are insane...
Regards
Michal
http://www.hobbyking.com/hobbyking/s...tart_Cord.html
hendrnk is offline Find More Posts by hendrnk
Reply With Quote
Old Feb 19, 2013, 12:38 AM
Un Registered User
Doodie's Avatar
Canada, BC, Chilliwack
Joined Feb 2013
176 Posts
That looks awesome! I am going to have to build myself one of these :P
Doodie is offline Find More Posts by Doodie
Reply With Quote
Old Feb 26, 2013, 02:50 AM
Registered User
Joined Jan 2010
47 Posts
Quote:
Originally Posted by emacs View Post
It's the simplicity which makes it so genious. A very convincing concept and build!

Question: You've made kind of 'clamps' around the wing. Is this to prevent the wing from pitching up upon launch? Or would a 90 degree upwards pointing pusher at the lower end suffice as well?
.
Yes its stops the wing from pitching up or possibly even flipping over backwards because its getting pushed from way behind its CG.

Quote:
Originally Posted by kist2001 View Post
With increasing tension your gantry is going to always slam into the end of your launcher. May I suggest you lengthen the launcher and put the attachment point for the bands about 1.5 foot back and looped underneath. Thus when the plane launches the bands will self brake the gantry,
Thanks for the idea. Simplicity was key in this build and it had to be short enough to fit in my car. Yes it does hit the end with knock but there is sufficient rubber damping. The sudden stop also helps dislodge the plane from carriage.

Quote:
Originally Posted by tty044 View Post
I think I will make such device too. Do you have any licensing policy?
My main problem is getting latex 10mm tube. Is there any internet shop with it? I have found something here but the prices are insane...
Regards
Michal
Go ahead and build as many as you want. I get my Latex tubing from a local supplier. The stuff they sell on HK should work fine.
brettbb is offline Find More Posts by brettbb
Reply With Quote
Old Feb 26, 2013, 12:42 PM
Registered User
United States, TN, Nashville
Joined Oct 2012
17 Posts
Very cool....thank you..
sloper10 is offline Find More Posts by sloper10
Reply With Quote
Old Mar 01, 2013, 10:33 AM
Registered User
richie967's Avatar
Cardiff, UK
Joined Aug 2008
285 Posts
Some q's regarding materials...

Hi, This catapult is great, I am going to build one for my 60" Zagi type wing (AUW 2kg). I have a few questions around the materials used,

- 50mm x 50mm Aluminium square Tube, what thickness wall? 1.6mm, 2mm?
- Aluminium plate, what thickness is it?
- are they m8 bolts?
- Standard skateboard bearings?
- Would 8mm silicone chord work?
- How is the tension put onto the bungees? do you simply connect them to the cart and physically pull the cart back?

I have made some guesses and posted my shopping list below, If anyone has time I wonder if anyone could look at the items and ensure they are good enough for the job? The one piece i have left off is the bent aluminium cradle that the plane sits in.....Thanks, rich

Here is my shopping list... Total cost - 68.12!!

Nuts and Bolts

50mm square tube, and 20mm square tube

Aluminium plate 150mm x 50mm x 5mm

Silicon Rubber Bungee Launch Chord

Toggle Clips

Skateboard bearings
richie967 is offline Find More Posts by richie967
Last edited by richie967; Mar 01, 2013 at 10:40 AM.
Reply With Quote
Old Mar 05, 2013, 09:20 AM
Registered User
Wilson, NC
Joined Aug 2009
219 Posts
Hi brettbb
Your catapult is an excellent design. Bet you really enjoyed designing and building it. Looks like it works great.
villapilote is offline Find More Posts by villapilote
Reply With Quote
Old Mar 07, 2013, 10:48 AM
Registered User
Germany
Joined Jun 2009
24 Posts
Hello everybody,

I'm also interested in this project, but we are looking for more details

@brettbb
I took one of your pictures and tried to get the correct measurements. I used a 50 x 50 mm quadrat as reference. If I'm correct, you use:
- Screws M8
- aluminium plate 7 mm, 130 mm wide
- bearings with outside diameter 23 mm

The bearing diameter seems to me very strange. Is it possible to verify this measurements, please?

@richie967
If I'm right, your selected aluminium plate is to small

Sorry for my english, but it's not my native language

regards
Robert
Robert77 is offline Find More Posts by Robert77
Reply With Quote
Old Mar 07, 2013, 11:34 AM
Registered User
emax's Avatar
Germany, HE, Darmstadt
Joined Feb 2013
154 Posts
Quote:
Originally Posted by Robert77 View Post
- bearings with outside diameter 23 mm

The bearing diameter seems to me very strange. Is it possible to verify this measurements, please?
Forget about the exact diameter. Depending on the screw-positions there should be some room for somewhat other types.
emax is offline Find More Posts by emax
RCG Plus Member
Old Mar 08, 2013, 10:40 AM
Night flier
United Kingdom, England, Bromyard
Joined Mar 2008
831 Posts
Great launcher I can't hand launch my wing it has no hand holes. Would love a list of parts needed then IDE build one.
austin.laws is offline Find More Posts by austin.laws
Reply With Quote
Old Mar 11, 2013, 03:30 AM
Registered User
Russian Federation
Joined May 2012
13 Posts
How long is the truck?
itim is offline Find More Posts by itim
Reply With Quote
Old Mar 11, 2013, 05:30 AM
Registered User
Germany
Joined Jun 2009
24 Posts
Quote:
Originally Posted by itim View Post
How long is the truck?
I "think" it's about 19 - 20 cm long

regards Robert
Robert77 is offline Find More Posts by Robert77
Reply With Quote
Old Mar 12, 2013, 02:52 PM
Registered User
Joined Jan 2010
47 Posts
Quote:
Originally Posted by richie967 View Post
Hi, This catapult is great, I am going to build one for my 60" Zagi type wing (AUW 2kg). I have a few questions around the materials used,

- 50mm x 50mm Aluminium square Tube, what thickness wall? 1.6mm, 2mm?
- Aluminium plate, what thickness is it?
- are they m8 bolts?
- Standard skateboard bearings?
- Would 8mm silicone chord work?
- How is the tension put onto the bungees? do you simply connect them to the cart and physically pull the cart back?

I have made some guesses and posted my shopping list below, If anyone has time I wonder if anyone could look at the items and ensure they are good enough for the job? The one piece i have left off is the bent aluminium cradle that the plane sits in.....Thanks, rich

Here is my shopping list... Total cost - 68.12!!

Nuts and Bolts

50mm square tube, and 20mm square tube

Aluminium plate 150mm x 50mm x 5mm

Silicon Rubber Bungee Launch Chord

Toggle Clips

Skateboard bearings
Quote:
Originally Posted by Robert77 View Post
Hello everybody,

I'm also interested in this project, but we are looking for more details

@brettbb
I took one of your pictures and tried to get the correct measurements. I used a 50 x 50 mm quadrat as reference. If I'm correct, you use:
- Screws M8
- aluminium plate 7 mm, 130 mm wide
- bearings with outside diameter 23 mm

The bearing diameter seems to me very strange. Is it possible to verify this measurements, please?

@richie967
If I'm right, your selected aluminium plate is to small

Sorry for my english, but it's not my native language

regards
Robert
Sorry for the delayed reply guys.

The 50 x 50 tube is 1.6mm wall thickness.
bolts are 8mm.

Robert your dimensions are very close.
The plate is 120mm x 200mm and 6mm thick.
The bearings are 8mm inside diameter and 22mm outside diameter.
brettbb is offline Find More Posts by brettbb
Reply With Quote
Old Mar 20, 2013, 02:42 PM
Registered User
richie967's Avatar
Cardiff, UK
Joined Aug 2008
285 Posts
Progress on catapult

Hi Bret, cheers for confirming my questions, unfortunately I didnt get any updates from the website to say that anyone had replied! so ordered all the parts above in my shopping list. I am not having much luck with the catapult at the moment. And have made a series of modifications.

1. The toggle clips and the small bits of 20mm alloy riveted to make the joiner didn't work very well for me. So i used a 1 meter piece of wood that fits 500mm inside each half of the boxed alloy. However it is 1mm smaller and the rail doesn't line up nicely, the bearings dont run smoothly over the join, and have begun cutting into the rail :-(. May need to rethink how to do the joiner.

2. the rear bearings kept coming off the rail. Possibly to the holes in the plate not being drilled as accurately as I would have liked. So i have added a second plate underneath to ensure the bolts don't bent outwards causing the carrier to come off the rail. This works well.

3. Due to the fact that i had to add a piece of wood inside the rail, i had to remove the release tube that flxes to release the pin. I halved the length of this and put a bolt

4. I initially thought a pulley system would work well with HobbyKing 8mm Silicon Rubber Bungee Hi-Start Cord. So started with 2 lengths 1m long, tied to base of catapult, then moved up and around the pulleys, and fixed onto the carriage, this didn't provide anywhere near enough pull. So replaced it with hardware store bungee chord. Which has more pull, but still didn't provide enough power. As seen in the first launch.

I then ditched the pulley system, and simply used two loops of bungee, this gave enough power to just about launch the plane, however in the video below, the plane does launch, but you see the carrier slow down considerably about half way along the rails. I think it's important for it to keep pulling all the way to the end.

Here are two videos of my attemps...

This one shows all three launches

Testing the catapult on the flying wing (0 min 16 sec)


This one shows just the last launch in slow motion - The prop clipped something as it left the rail and cracked 10mm of either end of it! It still flew okay to do a circuit and land.

Catapult launch - Slow motion (0 min 11 sec)


On the third launch i applied full throttle as i stepped on the release pin. I'd rather not apply throttle until the plane has left the launcher to avoid prop strikes, certainly for the next few tests anyway.

I'm not sure which bungees to use to get enough pull to launch the plane off properly. I have drawn a picture showing my thoughts, using two pulleys, and two loops of bungee chord - My question is why do you think i need so much extra chord to launch a plane that is half the weight of the x8?

Rich

Also taking on any helpful pointers!!!
richie967 is offline Find More Posts by richie967
Reply With Quote
Old Mar 21, 2013, 04:17 AM
Registered User
Germany
Joined Jun 2009
24 Posts
Quote:
Originally Posted by richie967 View Post
4. I initially thought a pulley system would work well with HobbyKing 8mm Silicon Rubber Bungee Hi-Start Cord. So started with 2 lengths 1m long, tied to base of catapult, then moved up and around the pulleys, and fixed onto the carriage, this didn't provide anywhere near enough pull.
Im shocked . I ordered the same 8mm Silicon Rubber Bungee Hi-Start Cord (its still on the way).
Do you mean, your "unstretched" cord is 1m long (one way, the half way of your launcher)???
Bretts cords seem to be around 25% of the launcher lenght, see the picture below (I love to cut scenes from clips and add measurements ). The cord will streched about 4 times of its original lenght.
Brett, please correct me if I'm wrong.

regards
Robert
Robert77 is offline Find More Posts by Robert77
Reply With Quote
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Discussion Best FPV Platform : Skywalker V5 vs Skywalker X8 Wing asaak FPV Talk 14 Feb 16, 2013 03:56 AM
Sold Skywalker X8 Flying Wing keithskye FPV Equipment (FS/W) 16 Sep 06, 2012 06:16 AM
Sold Skywalker X8 flying wing keithskye Aircraft - Electric - Airplanes (FS/W) 12 Sep 06, 2012 06:09 AM
Discussion skywalker x8 gravity center nocomp Flying Wings 4 Jul 29, 2012 11:51 PM