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VTO free flight model gets airborne

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Re: VTO free flight model gets airborne

Post  Oldenginerod on Mon Jun 06, 2016 5:22 am

Ah, yet another one of those fake twins Eyebrows lol!
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Re: VTO free flight model gets airborne

Post  jmcalata on Mon Jun 06, 2016 5:28 am

Oh yeah, thanks oldenginerod it´s really fake, but add simetry and weight balanced lol!
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Re: VTO free flight model gets airborne

Post  OVERLORD on Mon Jun 06, 2016 5:43 am

...and it would be an out of balance 0.10 as the added cylinder is a 0.049!! Huh... Huh... Rolling Eyes Rolling Eyes
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Re: VTO free flight model gets airborne

Post  Oldenginerod on Mon Jun 06, 2016 7:17 am

OVERLORD wrote:...and it would be an out of balance 0.10 as the added cylinder is a 0.049!! Huh... Huh... Rolling Eyes Rolling Eyes
Add more head shims Thumbs Up
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Re: VTO free flight model gets airborne

Post  crankbndr on Mon Jun 06, 2016 9:13 am

Heres one that just went off on eBay, though its not free flight. Fetched a nice piece of money too.

http://www.ebay.com/itm/THE-HOLY-GRAIL-Extremely-rare-Atheann-POGO-New-in-box-/272255753311?_trksid=p2047675.l2557&ssPageName=STRK%3AMEBIDX%3AIT&nma=true&si=%252BrtmICRPMU8dWeGeQP%252B92nc4bKU%253D&orig_cvip=true&rt=nc


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Re: VTO free flight model gets airborne

Post  roddie on Mon Jun 06, 2016 10:08 am

I'm at a loss.. reading these last flight details.. Huh... but will ask; will the model run-out a tank static? If so.. can you fashion a test stand that allows the model to rotate as it would in flight? I'm not sure if this could help prove my suspicions.. but I'm now wondering if there's a possibility that the plug is getting wet and fouling-out?

Things to try.. alternate temp. plug(s).. +/- nitro fuel-blends.. Huh...

I'm also trying to think-up a system that deploys dive-brakes.. or a parachute in the tail-cone when the model pitches nose-down. It would be terrific if it glided-down.. but I don't really think it will, where it's so small.. and you cannot adjust any airfoil-surfaces in-flight. It would be a shame to achieve a high-altitude flight.. only to have the model suffer serious damage when and "where" it lands.



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Re: VTO free flight model gets airborne

Post  OVERLORD on Thu Jun 09, 2016 2:40 am

I made some further tests yesterday afternoon. Getting there!! I will put a video together and upload today. Here are some stills







Lieven
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Re: VTO free flight model gets airborne

Post  getback on Thu Jun 09, 2016 6:22 am

Clapping Clapping Clapping Over the Hedge/Trees ? Looking Good !! getback sunny
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Re: VTO free flight model gets airborne

Post  OVERLORD on Thu Jun 09, 2016 11:08 am

getback wrote:Clapping Clapping Clapping Over the Hedge/Trees ? Looking Good !! getback  sunny

No, not over the trees!!

I tried the plane yesterday with the new set up. I first tried the engine statically. I set the needle on the rich side and let it spin but the engine stopped immediately. The revs didn't go up so the engine didn't go lean. It must have something to do with what Roddie said, maybe the fuel is hitting the glow thread.



https://www.youtube.com/watch?v=JJkaJw44PXI

For the first flights I gradually leaned out the engine to get the most revs possible. That's needed for a good take off! The first few times, I launched and tossed the plane but that seemed not to be the proper way. By tossing, you give the plane a certain direction which is in most cases not vertical. The plane itself doesn't correct its track and continues flying the given path. The trick is to hold the plane as vertical as can be and let it slide out of your hands. That was almost achieved in the last launch on the video.

I started with a 20g weight on the tail but that didn't make any difference so I took that off. The plane came down nose first all the time.

Although I set the engine as lean as possible, it doesn't run very long. Maybe better that way because of the "steep" landings. I still don't know why it stops though.



https://www.youtube.com/watch?v=inDHIXsnG9w

To make sure the plane will take off vertically, i'm thinking of making what the model rocket guys have and that is a tube along side the fuselage and a vertical steel wire fixed on a platform as a guide.

Lieven
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Re: VTO free flight model gets airborne

Post  ian1954 on Thu Jun 09, 2016 12:41 pm

Lieven,

This is a really nice model and you have an incredible amount of patience. I like the Tin Tin pilot as well.

I was watching the glide after the engine stopped and it seemed nose heavy to me. This is going to take a lot of trial and error.

Keep it up!
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Re: VTO free flight model gets airborne

Post  1/2A Nut on Thu Jun 09, 2016 2:56 pm

You need reflex on the trailing edge and you need to establish a true CG all the same.
Its nose heavy without the reflex much needed on all flying wings. Up reflex read up on
it if you haven't before.

I recall one launch it flipped inverted as it nosed down and crashed.
Pretty much arching crashes but will work with CG 30 to 35% off the leading edge and the
all important must have reflex. Should level off and glide then.. Small Cox Logo Small Cox Logo Small Cox Logo

Should fly verted then ..

Thank you for sharing!
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Re: VTO free flight model gets airborne

Post  gcb on Fri Jun 10, 2016 6:08 pm

OVERLORD,
If you ever try the Bee engine setup again, check the seal between the venturi tube on the tank and the backplate. A leak here will normally cause the engine to quit lean when the fuel level drops below the venturi. Reason = you adjust the needle using fuel from the needle plus whatever is leaking in. When it starts sucking air, it goes too lean. Spinning might cause it to suck air... Just a thought.

George
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New engine set up

Post  OVERLORD on Sun Dec 04, 2016 5:26 am

Thanks for your comments and tips.

I tried a new engine set up this week end. With a heli tank from Bernie, I mounted a product engine onto a plywood motor mount to do some testing and hoping for an improvement. It is a configuration as found on the Sky Jumper and that heli works well!!

Although estetically not so nice, it has plenty of advantages compared to the TeeDee and tank:

1) The total assembly with extra plywood motormount is about 25g lighter.
2) Mounted out of centre, there is no counter weight, so more simple and less parts.
3) the engine is closer to the fuse being better for the CG.







I fired up the engine yesterday and the engine ran well. As soon as it started to rotate, it stopped just as with the Babe Bee I tried. I tried richer or leaner settings but that didn't make any difference.

The only difference I can think of with the Cox helicopters is the rotating speed of the engine. The helicopters have 4 long blades that give more resistance than the aluminium prop on the VTO. The engine must turn too fast to be able to draw fuel to the centre.

I understand now why the TeeDee with tank ran for a small period before stopping. Although the engine could draw fuel while rotating, the square shape of the tank created turbulences and the little fuel that was in there was thoroughly mixed with air. A similar but round tank would be an improvement.


Lieven
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Re: VTO free flight model gets airborne

Post  pkrankow on Sun Dec 04, 2016 7:54 am

So clone that tank in brass and tin, but make it a different shape. I would think that making it more tall than bulbous would provide less fuel head to draw against.

Phil
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Re: VTO free flight model gets airborne

Post  roddie on Sun Dec 04, 2016 9:54 am

Huh... Huh...  There must be a way to get this model to work reliably. Every failed attempt makes my heart ache for you. Another suggestion.. Rolling Eyes  What if you were to add a 2nd aluminum prop rigidly mounted to the nose? That would theoretically slow the rotation.. wouldn't it? It would also catch more air for a slower descent. You have 2gr. less weight to work with.. although less power with the reed-valve.

The engine-torque is causing this model to rotate with little resistance. The wing may act as a paddle.. but it doesn't counteract the force in any way. A rigid reverse pitch propeller would.. maybe even trim-tabs on the T/E?? Huh...

With the reedy.. you could even try a L/H prop. Your aluminum blade-pitches can be adjusted to suit. It might be a good idea to note and record the pitch (twist) settings on those, before each flight. If you have a successful flight, you'll know how they should be set before the next flight. They're likely to get bent when the model lands.

Just more of my Two Cents (am I up to a dollar yet? Embarassed )
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Re: VTO free flight model gets airborne

Post  Marleysky on Sun Dec 04, 2016 1:08 pm

Ok! Here' my Two Cents Two Cents worh a plugged nickel.  I've searched VTOL craft on google and wiki.  None of them I saw had the rotation of the engine as part of the design. You should be able to achieve vertical take off, transition to level flight and glide to earth when properly balanced with out the problem of centrifugal force messing up the fuel flow to the engine. Gosh, even those who video cox engines as "flyin rags" get plenty of run time with out fuel starvation.  I'd suggest you try one more iteration using the engine and flight assembly off a cox helicopter with the large slow turning blades. They all mount on a 2 1/2 or 3 inch long "pin" with a little c clip to retain it to the aircraft body. As long as the weight does not exceed that of a Air wolf, Rescue Copter, or Air Cobra and is balanced it should rise vertical and float back down on the slow rotation of the heli blades. .....watch some of Kim's video from SMALL hillarious Heli action. lol!
Or, even more fun, re mount the 051 on a rigid attached motor mount and let her rip!
( Send Tin tin to pilot school .....he's not holding the control stick correctly) lol!
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Re: VTO free flight model gets airborne

Post  KariFS on Sun Dec 04, 2016 1:54 pm

I too believe that the engine just spins too fast. The Cox helicopter models have a four-blade rotor with about 30cm (12") diameter, so they must spin slower. I have never seen one in real life though. Maybe you should try a larger rotor Huh... Maybe not quite as large as the Cox ones if you want to see some horizontal flight too. Maybe attach some 3mm balsa or plastic blades to your existing aluminum rotor for testing first?

Just my Two Cents (those cents are probably piled up to your chin already...)
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Re: VTO free flight model gets airborne

Post  GallopingGhostler on Sun Dec 04, 2016 2:33 pm

Interesting video, Overlord, just wonder how far in orbit it would have achieved if engine did not cut out when it transitioned to horizontal.  Paranoid

Deviating a little from current discussion, but accorded to VTO's, found this interesting free flight profile plan from jetex.org:



Front lends itself to a small Cox engine with spinner as a prop jet if scaled accordingly. Of course, with the tail in an "X", and if one wanted to make as RC or CL instead of FF, it would be interesting how one would control it via RC. CL would be more straight forward. Launch would be interesting.
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Re: VTO free flight model gets airborne

Post  MauricioB on Sun Dec 04, 2016 3:16 pm

OVERLORD wrote:Thanks for your comments and tips.

I tried a new engine set up this week end. With a heli tank from Bernie, I mounted a product engine onto a plywood motor mount to do some testing and hoping for an improvement. It is a configuration as found on the Sky Jumper and that heli works well!!

Although estetically not so nice, it has plenty of advantages compared to the TeeDee and tank:

1) The total assembly with extra plywood motormount is about 25g lighter.
2) Mounted out of centre, there is no counter weight, so more simple and less parts.
3) the engine is closer to the fuse being better for the CG.







I fired up the engine yesterday and the engine ran well. As soon as it started to rotate, it stopped just as with the Babe Bee I tried. I tried richer or leaner settings but that didn't make any difference.

The only difference I can think of with the Cox helicopters is the rotating speed of the engine. The helicopters have 4 long blades that give more resistance than the aluminium prop on the VTO. The engine must turn too fast to be able to draw fuel to the centre.

I understand now why the TeeDee with tank ran for a small period before stopping. Although the engine could draw fuel while rotating, the square shape of the tank created turbulences and the little fuel that was in there was thoroughly mixed with air. A similar but round tank would be an improvement.


Lieven

Hi, how are you? I wanted to ask you how it was with this project, now I find this thread and I see that you are doing different tests. Look, have you thought of placing as a fuel tank: a balloon or bladder ?, I do not know what you call this accessory, but a bladder has no weight and will always send fuel pressure, even if the engine turns very fast, will always count With a healthy supply of fuel. It does not need to be very large, only lasts a few minutes the model climbs quickly. What do you think??

You can even build a cage for the bladder with something simple like a hair tube, which will not generate extra weight or resistance when turning, since it is a mesh with many holes and that does not generate turbulence with the speed of rotation. I only think of you high!
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Re: VTO free flight model gets airborne

Post  batjac on Sun Dec 04, 2016 4:51 pm

Lieven, awesome plane!

For my two cents worth, I'd try two things to get some more data.  First, I'd rotate the fuel tank around counter-clockwise so that the fuel pickup is horizontal to the fill nipple.  That way the fuel gets slung to the outlet instead of the side of the tank.  You could start the engine while holding the plane horizontal, then turn the plane back vertical while the engine spins up.  A little fuel would weep out when you first tilted it back upright, but if you get a longer engine run this'd give you some more data to work off of.  

Second, I can't tell what prop you're using.  Maybe try a Cox 4.5x4, 5x4, or 5.5x4 prop to load down the engine.  I don't know if you have Master Airscrew props easily available there, but a 6x4 might be worth a try.

The Shotgun Mark


Last edited by batjac on Sun Dec 04, 2016 4:57 pm; edited 1 time in total
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Re: VTO free flight model gets airborne

Post  batjac on Sun Dec 04, 2016 4:54 pm

MauricioB wrote:You can even build a cage for the bladder with something simple like a hair tube, which will not generate extra weight or resistance when turning, since it is a mesh with many holes and that does not generate turbulence with the speed of rotation. I only think of you high!

Wow! When looking for things to hold balloon tanks, hair curlers never even occurred to me. Great idea! I'll have to head over to the Dollar Store and see what they have for testing.

The Amazed Mark
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Re: VTO free flight model gets airborne

Post  MauricioB on Sun Dec 04, 2016 9:07 pm

batjac wrote:
MauricioB wrote:You can even build a cage for the bladder with something simple like a hair tube, which will not generate extra weight or resistance when turning, since it is a mesh with many holes and that does not generate turbulence with the speed of rotation. I only think of you high!

Wow!  When looking for things to hold balloon tanks, hair curlers never even occurred to me.  Great idea!  I'll have to head over to the Dollar Store and see what they have for testing.

The Amazed Mark

Thank you, it is a pleasure to be able to contribute some idea I think it has to work very well!

Look, here's an example of bladder, 0:48 minute !!!:
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Re: VTO free flight model gets airborne

Post  OVERLORD on Mon Dec 05, 2016 5:57 am

Thanks for your posts rich of info, suggestions and ideas. Initially, I was thinking of making a pancake-like fuel tank with the fuel outlet pipe on the side and on top of the tank, mount the TeeDee out of centre. The prop I used is a Thimble Drome 6x3. I don't know what différences other props would give. A smaller prop creates less torque but will turn faster? The LH prop is 200 mm long and a pitch of 30°. At what blade angle, a prop becomes a brake?
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Re: VTO free flight model gets airborne

Post  rsv1cox on Mon Dec 05, 2016 6:56 am

Wow, how this thread has grown thanks to all the thinkers and innovators here.

Enjoying it.

Bob
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Re: VTO free flight model gets airborne

Post  gcb on Mon Dec 05, 2016 8:43 am

KariFS wrote:I too believe that the engine just spins too fast. The Cox helicopter models have a four-blade rotor with about 30cm (12") diameter, so they must spin slower. I have never seen one in real life though. Maybe you should try a larger rotor Huh... Maybe not quite as large as the Cox ones if you want to see some horizontal flight too. Maybe attach some 3mm balsa or plastic blades to your existing aluminum rotor for testing first?

Just my Two Cents (those cents are probably piled up to your chin already...)
 

Kari, I think you have the solution. Either longer blades or more of them to slow rotation should help.

As engines became more powerful, intakes became larger and fuel draw became smaller. It is entirely possible that as rotation increases it exceeds fuel draw.

Another possibility is to use pressure, or perhaps a combination of both.

CRANKBNDR, you are making me feel old. I remember when the POGO was in the hobby shops. Sad

George
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