Hi guys, just a quick thread for my X8 bungee launcher.................
I got motivated thanks to Skipperbilly and a few failed attempt at launching last weekend due to lack of airspeed mixed with torque roll s decided I better make a launcher and save a whole world o pain :)
I made it from :
4x 32mm solvent type drain pipe
4x 32mm solvent type elbows
4x 32mm solvent type T`s
2m length 3x1 PSE wood
Pack of ten M5 x 50mm bolts
Pack of ten M5 Nylon nuts
6x 100mm x 10mm bolts ( for staking launcher to the ground )
T brackets from B&Q
3x 6" nails
4x Keyring rings
2x 10m length on 10mm ( blue ) Silicon Bungee tube
14.6m Nylon rope
Pets at Home dog screw in dog stake
Digital luggage scales
I dry fitted the launcher first to gauge the angle I wanted, you can see below how basic the design is, I used T`s for each corner for added stabability. Elbows on the top with the front two elbows cut down and glued in place so the wings do not catch on the launch
(http://i108.photobucket.com/albums/n39/cayote64/th_launcherlarge.jpg) (http://s108.photobucket.com/albums/n39/cayote64/?action=view¤t=launcherlarge.jpg)
I experimented with the width with the X8 on until I was happy with how it sat, how it was supported and a natural travel up the ramp
(http://i108.photobucket.com/albums/n39/cayote64/DSC_0189-1.jpg)
Once I was happy I cut the legs down to a more practical height and the shorter length makes the legs stiffer too
(http://i108.photobucket.com/albums/n39/cayote64/choppeddown.jpg)
Next I added the trigger for the bungee release, very simple I was after.
It comprises of two T brackets bolted to either side of the pipe, a bolt locked from the inside and outside of the brackets to strengthen and keep the gap for the wood constant. I drilled a cut piece of the 3x1 and it will pivot on the bracket.
A 6" nail will be what holds the ring in place, curved backwards so it wont accidentally fall off. The wood when pressed down on will raise, push the ring over the nail and release the plane.
I added rubber bands to hold the wood down so it can not be accidentally triggered. It also keeps the wood square when using it.
(http://i108.photobucket.com/albums/n39/cayote64/DSC_0196-1.jpg)
(http://i108.photobucket.com/albums/n39/cayote64/triggerhinge.jpg)
The bungee tube should arrive tomorrow, so until then all I could do was make up the nylon end.
One ring, the release ring go to the trigger, the second rig goes to the plane. Both rings were connected to the rope by using fishing knots. I used the tucked blood knot, works very well.
(http://i108.photobucket.com/albums/n39/cayote64/Tuckedbloodknot.jpg)
Very neat knot, which I left a tail hanging from, the heatshrink ed the tail to neaten it up a bit more as above.
To connect the two lines to each other I used the 5 turn water knot, again very strong but with rope, also very neat too
(http://i108.photobucket.com/albums/n39/cayote64/5turnwaterknot.jpg)
The idea being that with both hooks on, both the release ring and the plane ring will both be under tension so no nasty shock load goes to the plane when I trigger the release. It was pretty easy to do by using the water knot.
So the plane end looks like this :
(http://i108.photobucket.com/albums/n39/cayote64/Planehooks.jpg)
Ill update with bungee end when it turns up, then either some awesome or totally hilarious launch videos :)
Really nice build mate, should be a good one. Cant wait to see your 1st launch.
Nice piece of engineering mate, look forward to the test vids
hope you pressure tested it coyote, those joints look a bit sus to me, what with all the regs these days, do i see knicker elastic or what there ;D
0 to 60 in 0.5 secs :o looking brill :)
dizzy ;)
Nice launcher, that's going to work like a dream...... hardly seems worth doing a video of the first launches :D
Hope the bungee arrives soon !
Nice. Looking forward to seeing this one in action!
@Coyote
If you PM me your address I will post you two stainless steel welded rings (FOC) - those key ring type split rings will open up with 12 kgs of pull and the bungee will do its best to castrate you - it doesn't matter how I know but I am typing in a high pitched voice!
Lol thanks Billy, I will do.
I went to Boyes today to find some more heavier duty ones but no joy.
Ok.............. bungee tube came today :)
I came up with my own version of making the ends off of the bungee tube. So far 1 tried, I pulled and pulled and it would not come away
I got some Wilko screw eyes, very strong.
(http://i108.photobucket.com/albums/n39/cayote64/DSC_0203-1.jpg)
The bungee of course, then I sized up some prop shaft adapter rings
I put the rings on the tube, 2 per piece, then glue on the shaft of the screw eye.
(http://i108.photobucket.com/albums/n39/cayote64/DSC_0206.jpg)
Screwed it in, slid the rings up so the rubber was very tight against the shaft
I let it dry and then pulled as hard as I could. So far a pass, but when the scales turn up I can properly test under load :)
(http://i108.photobucket.com/albums/n39/cayote64/DSC_0207.jpg)
I think using carabenas between the ings might be an idea.
Also I noticed the plane has quite high friction against the ramp. Not too clever, the poly tunnel tape does not like it. But with the wings off I could hardly keep the fuse on the ramp, the carbon rods were acting like the ramp was oiled :)
Next mod, to install some short carbon rods on the underside of the wings to keep the pull required down :)
Thanks for the comments lads n lasses :)
I forgot to put a pic up of the ground screw I`m using to hold the far end of the bungee in :
(http://i108.photobucket.com/albums/n39/cayote64/DSC_0231.jpg)
Ok, a bit changed, first big thanks to Skipper Billy for sending me up two steel welded rings. Much much stronger than my keyring efforts and as I have now found out essential really.
Next thanks goes to Shay :) Shay is one of the two children Donna and I have in our care. Why ? Because I hunted high n low for a parachute for the bungee cord. Apart from paying 20 quid for one online I was out of options. Shay came down with his action man, said " you can have his parachute " and " I don`t like him anyway " lol Never been so happy to buy the child a toy he didnt like lol
(http://i108.photobucket.com/albums/n39/cayote64/DSC_0230.jpg)
There is the result with new rings and chute :)
Ok so today its pouring down, didnt want to take to X8 out on a soaking wet muddy field, but initial launcher / bungee tests ? Hell yeah :)
First attempt did not go well to be honest. One of the glued eyed bolts didnt stay on, all I heard as I was walking away was a weird sort of buzz notice, then followed the bungee ( minus the bolt ) wrapped me across the back of my leg and finger ........................... Then followed ( in this order ) pain, jumping, profanity, screaming and then calm :)
I packed up, went back, swapped out the eyed bolts for just knots and went for round two ...................
Round two went great, I wanted to prove :
Bungee was fine at 15kg of load ( I only need 12kg max )
Fixing on the cord held
Pets at home dog spike held at 15kg
Launcher trigger could hold 15kg load
Launcher stayed in place under load
Release mechanism worked
Parachute worked
How many paces needed for required load
All the above completed including sat in the car for 20 mins with bungee on the launcher at 15kg to make sure nothing would come away if it was left for any time :)
so far I think ( if my scales are correct ) that 12kg is way too much load needed to launch the X8, Ill start at 9KG of pull tomorrow and I bet that has more than enough tbh
Looking good Ian, love the corkscrew, I don't think you should drink and fly tho.
:laugh: G
:pint: Lol cheers G
Put a tin of beans next to it for scale heh
I dunno, some people are never happy :)
(http://i108.photobucket.com/albums/n39/cayote64/DSC_0232.jpg)
Better ? :)
I was on about the corkscrew, G man reckons you're gonna open a bottle of wine - some bottle of wine!!!!
Nice you got it finished!
You fired anything off it yet?
We want video! ;)
Quote from: Steve W on November 12, 2012, 09:00:57 PM
I was on about the corkscrew, G man reckons you're gonna open a bottle of wine - some bottle of wine!!!!
I knew that :)
(http://i108.photobucket.com/albums/n39/cayote64/DSC_0233-1.jpg)
Quote from: Flyn on November 12, 2012, 09:03:06 PM
Nice you got it finished!
You fired anything off it yet?
We want video! ;)
No was peeing down and waterlogged field so no way was a spanky shiny new looking WHITE X8 getting chucked into that slop lol
But I will tomorrow if the fields dried out a bit and its not pouring :)
Quote from: Coyote on November 12, 2012, 09:09:47 PM
Quote from: Steve W on November 12, 2012, 09:00:57 PM
I was on about the corkscrew, G man reckons you're gonna open a bottle of wine - some bottle of wine!!!!
I knew that :)
(http://i108.photobucket.com/albums/n39/cayote64/DSC_0233-1.jpg)
That's the exact same one I use on mine, works a treat!
You use a tin of beans on your launcher ? :)
Quote from: Coyote on November 12, 2012, 09:11:36 PM
Quote from: Flyn on November 12, 2012, 09:03:06 PM
Nice you got it finished!
You fired anything off it yet?
We want video! ;)
No was peeing down and waterlogged field so no way was a spanky shiny new looking WHITE X8 getting chucked into that slop lol
But I will tomorrow if the fields dried out a bit and its not pouring :)
Cool mate, yeah has been pretty horrid today, don't blame you I wouldn't fire my zed into a mud puddle either!
Quote from: Coyote on November 12, 2012, 09:14:32 PM
You use a tin of beans on your launcher ? :)
Yeah but the low salt version - need to watch my blood pressure.
Lol ;)
You really think 9kg is going to be enough?
Seems on the low end to me...
Yeah I think so, now I added the carbon rods to the underside of the wings the X8 goes up the ramp like its covered in oil lol. But only one way to find out :)
Skipperbilly`s tests with his launcher showed he could launch his on just 3x the models weight
it's only 3kg? Call me a skeptic but I prefer to go with too much and then dial down than too little and then cry.
Just pick a nice area so if it skids along on it's belly you can try again lol.
Good luck!
Yeah its only 3.2kg with 2x lipo`s in it. I have a massive cut field to try tomorrow, the plan is to start at 9 and work up until I have plenty. I`m just worried how hard it might snatch at it at 12kg lol
Also for your first launch, put a soft cover over the handle of the ground anchor or it could cleave you X8 in twain!
How do you mean Flyn ?
nowt wrong with a bit of snatch...
I'm amazed at the weight - that's a big aircraft for such little weight! With the wing area it should be able to slow to a crawl which will help your launch of course!
Good luck - and get video ;)
Quote from: Coyote on November 12, 2012, 11:32:20 PM
How do you mean Flyn ?
If you don't get a good launch the second thing the plane will hit after the ground could be the triangular metal handle of your bungee stake (ground anchor) as the x8 will be pulled directly toward it.
I nearly (& I'm taking missing by a nat's whisker) hit mine on one of my 1st few launches.
With the zed when I launch I hold 1/3-1/2 up elevator depending on wind speed, & it gets off every time without fail, as long as I have the bungee tension right.
Lol I will do, I think Paul and Stu will be praying for rain so they can join me for it at the weekend though for the launchers maiden so many video will be recording :)
Quote from: Flyn on November 12, 2012, 11:38:38 PM
Quote from: Coyote on November 12, 2012, 11:32:20 PM
How do you mean Flyn ?
If you don't get a good launch the second thing the plane will hit after the ground could be the triangular metal handle of your bungee stake (ground anchor) as the x8 will pulled directly toward it!
I nearly (& I'm taking nat's whisker) hit mine on one of my 1st launches, with the zed when I launch I hold 1/3-1/2 up elevator & it gets off every time without fail, as long as I have the bungee tension right.
Ah ha ! Got you, very good point, I will do this :)
watching with interest as I need a way to launch my x8 as well :)
After reading what Flyn and Zeeflyboy said I think it might be wise to start at 12kg and work down in load after all
Just hold a bit of up on launch to prevent a X8 & ground anchor meeting, a little more up for lower wind speeds, wouldn't hold more than half thou - might be too much at near stall speeds.
Roger dodger :)
Quote from: Coyote on November 13, 2012, 01:15:06 AM
After reading what Flyn and Zeeflyboy said I think it might be wise to start at 12kg and work down in load after all
from my previous calculations
http://www.fpvhub.com/index.php/topic,6556.15.html (http://www.fpvhub.com/index.php/topic,6556.15.html)
with a mass of plane of 3.2 Kg
takeoff speed of 8 m.s-1 (18 m.p.h)
launch ramp length of 2m
angle of 5 degrees
should need an average force of 55 N ( 5.5 kgf). (With a long bungee thats about the same as the initial stretch force)
so if the above values are about right and your scales show 5.5 kg + of force it should go OK!
All the above assumes no wind and not much friction against the rails. Obviously any wind helps so you dont need as much stretch!
regards
Andy
5.5kg does seem to be way too low tbh, the load would instantly drop right off after release. Only when I got to around 7kg did I think there was at least a decent amount of energy stored, 9kg I figured was plenty.
But Ill keep trying lower and lower until it still launches but starts to struggle or takes more distance than I`m happy with to get up. Ill let you know what value that is ( if testing gets that far ) and see if it helps any with your calculations
Quote from: Coyote on November 13, 2012, 08:46:20 AM
5.5kg does seem to be way too low tbh, the load would instantly drop right off after release. Only when I got to around 7kg did I think there was at least a decent amount of energy stored, 9kg I figured was plenty.
But Ill keep trying lower and lower until it still launches but starts to struggle or takes more distance than I`m happy with to get up. Ill let you know what value that is ( if testing gets that far ) and see if it helps any with your calculations
It would be useful to know if the calcs do stand up, then they could be generally useful (might even do a Java App if I get around to it!), though they are currently based on the values I have guessed.
Do you know the minimum takeoff speed of the X8?
And also how long is the takeoff run on the launcher?
regards
Andy
I dont know the minimum speed ( yet :) )
The launcher ramp is 1.65m
Quote from: Coyote on November 13, 2012, 09:10:42 AM
I dont know the minimum speed ( yet :) )
The launcher ramp is 1.65m
Changing the launcher length to 1.65 m in the calculation, then the required force goes up to 65 N, which means 6.5 kg + on the scales, so sounds like your instinct of 7 kg is pretty much bang on!
regards
Andy
and 12kg is almost double the required pull...... ;D birds gonna fly! ;D
Some real world info that might be useful.
Depending on the amount of stiction - these figures are with the foam wing touching the rails.
12kg of pull = good launch
9kg of pull = passable but bordering stall speed off the ramp if there is little wind
anything less = short walk of shame
With carbon fibre tape under wings where rails touch and a waft of furniture polish on the rails -
12kg = great launch
9kg = good launch
7kg = passable
anything less = short walk of shame
These are all from a 1.8 metre ramp with 2 x 10m x 10mm lengths of bungee side by side. 10 degree ramp angle.
This is with 9kg of pull - no stiction reduction and a fair headwind.
https://www.youtube.com/watch?v=RTf_qWHf-jc&feature=plcp (https://www.youtube.com/watch?v=RTf_qWHf-jc&feature=plcp)
Ok, I finally did it :)
Here are the first 3 launches attempted, I love this launcher !!!!!
bungee (http://www.youtube.com/watch?v=tCbazC6Y4io#)
Point to address though I think is less of an angle on the tow hook to help with an earlier release, apart from that pretty happy.
The chute worked to pull the ring off, but I think a chute that isnt open from the start would increase speed and work better
Result!
Nice one mate, glad it worked!
Well done Coyote.
Wahey congrats!
Looked like the hook wasn't going to release for a moment there on the first launch!
Yeah I wondered lol It went to the left on launch, I compensated too much tbh so it stayed on for a bit longer than I thought it would.
Ill try again tomorrow without the chute as well. To see if I can get a higher pull speed ( 47kph was max on OSD ) without all the drag of the chute.
Stunning ;D
Well done mate
Yep I reckon a better result without the chute tbh
Weh--Hey!
The parachute is useful to stop hitting people on the head. I just used to use a bit of rag though, when I used to make free flight gliders. I seem to remember that tieing something heavy ( such as a 12 mm nut) a couple of inches in front of the rag helps to pop the ring off the hook.
Glad it worked!
regards
Andy
Cheers guys :)
In front or behind the rag Andy ? And should the rag be on the extension to the plane of the flying lead to the launchers trigger bud ?
Quote from: Coyote on November 15, 2012, 06:53:19 PM
Cheers guys :)
In front or behind the rag Andy ? And should the rag be on the extension to the plane of the flying lead to the launchers trigger bud ?
Put the nut the other side of the rag from the ring. The nut hangs down. The rag is sideways to the wind and the ring is at a better angle to slip off.
So goes the theory anyway!
regards
Andy
Quote from: Coyote on November 15, 2012, 06:53:19 PM
Cheers guys :)
In front or behind the rag Andy ? And should the rag be on the extension to the plane of the flying lead to the launchers trigger bud ?
Oh yeah... Rag should be on the bit with the ring for the plane hook I think
regards
Andy
Ok Ill try that next cheers :)
Nice launcher Coyote, but isn't it just typical that as one thing works (launcher) something else (motor/prop) fails !!
If you put the ring at the top off the parachute it will stay furled until the hook releases, you only really need it with long towlines to stream the line back downwind.
Nice one Ian, works a treat, you can call it buddy pips, or billy no mats launcher.
:laugh: G
Lol G,
Well I wish it went a easily as the tests went .................... If only :)
After about 5 failed attempts finally got it :)
http://youtu.be/n5mqrpKLp4Y (http://youtu.be/n5mqrpKLp4Y)
Only two factors changed
1) Control throws reduced
2) Parachute put back on
When looking back at the previous tests / video the control throws seemed fine. So that left the parachute. Once the parachute was back on, the next two launches were OK. I had much better results pre new motor , but it was windy so the results I had to be happy with.
* Best viewed in HD *
Lovely Ian, lovely :-*
Lovely!
Glad it worked in the end!
Interesting about the chute though. You got any theories about whats going on without it?
regards
Andy
great going Ian, I suppose the shoot slowed the bungee down to release the plane nicely.
:) G
Quote from: skyscraper on November 19, 2012, 10:44:36 AM
Glad it worked in the end!
Interesting about the chute though. You got any theories about whats going on without it?
regards
Andy
I`m really not sure Andy. The control throws were lowered also but on the previous video it was fine with those throws every time so to me it must have been the chute stabilizing it imo
Quote from: g.collins on November 19, 2012, 10:54:00 AM
great going Ian, I suppose the shoot slowed the bungee down to release the plane nicely.
:) G
Yes I think so G, or gave it some downward pressure ( directly below the hook ) maybe ?
Hi Ian, looking good there mate, glad it works for you!
Just a thought, have you tried moving the mounting hook forward a little, the spin without the chute could it be because the hook is too far back, allowing the nose to raise above & away from the direction of the bungee pull causing the spin out?
The chute could be effecting the high pressure side of the wing lowering it a little -providing slightly less lift under the centre section, just enough to slow it & keep it level?
Hi Flyn, no I`ve not tried moving the hook, but I see your point, you could be onto something there. I could then move the hook, but I`ll just save the trial and error and just leave the chute on, if it aint broke n all that :)
Quote from: Flyn on November 19, 2012, 12:00:45 PM
Just a thought, have you tried moving the mounting hook forward a little, the spin without the chute could it be because the hook is too far back, allowing the nose to raise above & away from the direction of the bungee pull causing the spin out?
Thats my hunch too. Same thing happens to a kite if you put the ring on the bridle too far back.
regards
Andy
Fair play mate - if you got it working...
crazy that the chute is the only thing stopping a failed launch, if for any reason the chute fails so will your launch, that's a lot of trust in a tiny parachute!
If it were me I'd move the hook so I wouldn't be relying on the chute to keep the plane on track, but hey your toys mate, you get to play with them how you like ;)
Here's a pic of the hook position on my zed, launches great every time straight & level. Note the two cg pen marks either side of the large black decal
Ill have a look, but moving the hook might be a lot of work
ah ok, fair point. Should be ok I'm sure. ;)
Coyote - two things I have found (and I think you are using the same bungee as me) are -
1. The outside temperature makes a big difference to the pull on the bungee - recently its been hovering about 3 - 4 degrees here and 30 paces of stretch = 9kgs pull but a few weeks back when it was 10 - 12 degrees 32 paces gave 8kgs pull
2. This is probably the most relevant having seen your video - after 10 - 12 launches from new - the bungee needs more paces of stretch to deliver the same punch - its worth checking with your luggage scale that the expected pull is actually there. Now mine has been used maybe 25 times it needs an extra 10 paces of stretch to deliver the same pull. When measured relaxed the bungee is now 12m long not 10!! It is now run in now I think!! From your video it looks like a simple stall to me - the sort of result you get from a half *rsed hand launch. More speed off the ramp should cure it - the parachute will only slow it down off the ramp. If you want it to release earlier just bend the hook down a little. To make it climb faster move the hook backwards towards CofG to keep it level but faster move the hook forwards - away from the CofG.
Hiya
1) I didn`t know that
2) I have so far used scales for each launch, 50 paces +/- a few but I will use them on every launch now just to make double sure. Looks like Ill have to bite the big one and open it all up again and move the hook forward then :( Oh joy lol
Ive moved the hook 3cm further forward from its previous 50% between nose and CG. Without pulling the whole thing apart its about the only place I could have put it. So Ill try again soon without chute
Quote from: Coyote on November 21, 2012, 01:43:33 AM
Ive moved the hook 3cm further forward from its previous 50% between nose and CG. Without pulling the whole thing apart its about the only place I could have put it. So Ill try again soon without chute
Just wondering... Did this mod work out? Does it work now without the chute?
regrads
Andy
Due to the rubbish weather, I`ve not been back out with it to try it out
Hi, I stumbled across this thread and it seems to answer my prayers! I have a non FPV (so far anyway!?) Habu 32 Foam Ducty and it is awkward to launch. I wondered what the practicalities of a catapult launch would be?
Any thoughts welcome.
The bungee launcher will have you airborne consistently and reliable every time.
If you need any help just shout. It was my launcher that inspired Coyote.
X8 Maiden Flight - Alba Aviation (http://www.youtube.com/watch?v=RTf_qWHf-jc#)
I really need one building :)
My x8 has been sat around for way to long and its next onto the work top sort to fly
its the mechanism I need building I can buy the launch tubes etc etc
I just used a nail and a piece of wood hinged with a hole in it, simplez :)
Thanks Billy,
I get the general drift of the plastic pipe frame, the 'dark art' details I guess are length and strength and stretch of Bungee, shape and position of hook, is the 'chute critical? and how to fasten/release the model at launch. What I could really do with is seeing it in action in the plastic ?
No dark art or smoke and mirrors - just a little experimentation tainted with initial failure ;) ;)
The bungee is easily available from here - http://www.hobbyking.com/hobbyking/store/__10609__HobbyKing_8mm_Silicon_Rubber_Bungee_Hi_Start_Cord.html (http://www.hobbyking.com/hobbyking/store/__10609__HobbyKing_8mm_Silicon_Rubber_Bungee_Hi_Start_Cord.html) 1 length for planes up to 2kg - two lengths side by side for up to 4kg
Get a luggage scale for weighing suitcases and attach it to the end - you want pull of about 3 - 4 times the weight of the plane - count how many paces that is then you can easily replicate it without the scales.
The hook on the plane wants to be about 50% from nose to CofG - its not that critical.
The hook needs to be capable of suspending 3 - 4 times the weight of the plane (metal coat hanger) and angled down about 45 degrees to the ring can slip off easily. I don't bother with para - just a bit of coloured cord so I can see when its released.
I posted a load of detail photos somewhere on here - have a search for bungee or launcher you should be able to find it - if not I will repost the photos when I get home tonight. My release mechanism is quite sophisticated - Coyotes works just as well and is much simpler to make.
Ok, that all makes perfect sense, I found your previous thread. My 'plane is 1.5 Kgs so a single length should suffice. Pace it out to 6 ish kilos of pull, stand well back and press the pedal?
Being a ducted fan I guess full throttle before release?
Thanks again.
6kg is more than enough - 4 - 5 would do it - with a ducted fan not only full throttle but wait until it comes on the pipe before pressing the pedal!!
Good luck.
Gathering up all the bits to build. One thing strikes me, the rope splits close to the 'plane end and one half goes to the release mechanism, the other goes to the hook on the 'plane. Would there me any merit in including a short length of bungee in the rope going to the model to reduce te sudden shock/snatch when the bungee is released?
Not really, you want the full power straight away to get the plane to come off the ramp and get its speed up. As soon as the plane is off the ramp the bungees stored power drops off very quickly so you want to utilize all the stored energy straight away.