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Old Sep 03, 2012, 03:35 PM
Just call me crash for short
Quick61's Avatar
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OK Stuart, I rubbed a few numbers together and this is what I come up with so far. With a input shaft speed of 62.4 RPM, doubling that - from 32 tooth to 16 tooth gives idler shaft and 48 tooth pulley speed of 124.8. That, back to the 16 tooth on the output pulley(48 tooth to 16 tooth) gives us 374.4 RPM. Working at 374.4 RPM, the .7 pitch of the drive nut should produce ~262.08 mm / min. or 4.3 mm / sec. That's a lot better than the (according to my calc) ~43.68 mm / min - .728 mm / sec that the 1:1 is giving now.

I thought that you had posted somewhere just how far you needed the slide to travel, but I couldn't find it, so I can't tell you just how fast the proposed step up will make it from end to end.

Let me know if this sounds alright, and to everyone else out there, check my math, cause there is always that first time I could get something wrong.

Mark
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Old Sep 03, 2012, 03:44 PM
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Quote:
Originally Posted by Stupot46 View Post
http://vimeo.com/48737825
I am a dinosaur!Unable to contact my guru(granddaughter)I've opened a Vimeo account but can't find how to get the vid on here.Hope the link works
Stuart
Splendid stuff Stuart!
Very impressive. And your videos play too . Looking forward to seeing how the flying article works.
I'm sure you are thinking that the speed of actuation will increase with the new designs, 4 min seems a bit long (but of course you know that).
Regards,
-Eric
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Old Sep 03, 2012, 04:01 PM
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Mark,I am WELL out of my zone of knowledge now!
The present set up with an approx.travel of 200mm is giving 70* on the disc.As to what the sweep range should be we need some input from more experienced(than me)pilots.15*-45*maybe?I think if you work on a 40* max it should cover it.
Does anybody have any info on the maximum practical sweep?#
I am sure that what I have done is the easy bit-it's now that the hard work starts!
Stuart

#just been doing some re-reading.The HoXIII flew with 60*
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Old Sep 03, 2012, 04:14 PM
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Originally Posted by ohmite View Post
Splendid stuff Stuart!
Very impressive. And your videos play too . Looking forward to seeing how the flying article works.
I'm sure you are thinking that the speed of actuation will increase with the new designs, 4 min seems a bit long (but of course you know that).
Regards,
-Eric
Thanks Eric.Personally I think the speed needs to be quick enough to say be fully swept in a steep dive and be opening as the wing pulls up into the glide.This presumes the cog adjusting also.Any thoughts you have on this would be most welcome.
Regards Stuart
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Old Sep 03, 2012, 05:24 PM
Just call me crash for short
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Originally Posted by Stupot46 View Post
Thanks Eric.Personally I think the speed needs to be quick enough to say be fully swept in a steep dive and be opening as the wing pulls up into the glide.This presumes the cog adjusting also.Any thoughts you have on this would be most welcome.
Regards Stuart
OK, so that breaks down to 2.8 mm / deg. - .65 sec / deg movement on the wing. This looks to come out to ~ 29.25 seconds to move the wings 45*. Maybe still not quite fast enough? Thinking about that and the simplest way to move the wings faster, reducing the radius of the wing pulley by half would give you a 45* movement time of ~14.6 seconds. Splitting the difference and going with 30* sweep would give you a transition time of 19.5 seconds at current radius and 9.75 seconds at half radius. All this of course makes a crazy assumption that all my math is correct. Again, this should be double checked before anything gets carved into stone.

Now all these numbers could be cut in half again if there is a doubling of the drive nut speed, but at that point we are starting to look at some real torque loading on the servo shaft. and maybe a further reduction in the swing radius, moving the torque load on to the back side of the screw drive would be far more practical. cutting that radius in half again should give a 30* transition time under 5 seconds. That's starting to sound reasonable to me.

Using Kent's idea of push rods coupled to the drive nut, several radius points on the wing pivot could be set up and easily tested, for both sweep speed and available torque at the wings.... Back to you.

Mark
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Old Sep 04, 2012, 03:21 AM
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Mark,thanks for doing all the math,plenty options to mull over.
I'm not going to mod.the motion until I've fitted the faster drive(just cos I want a one minute vid instead of four)
Some questions re electrics etc.
In Kents sketch,with a motor driving the screw instead of a servo,could one of those planetary geared motors in the previous post be used?Possibly direct to the screw.
In the same sketch at the driven nut-would adverse wing loading in a turn cause the nut to bind?Would it need a slide to keep it square?
Also as Kent points out some sort of limit switch will be needed;judging max/min from the ground won't be easy.
Any thoughts on how to control the sweep from the transmitter,could a three position switch be used?
Mark,could you work out the the dimensions of Gs centre section please, at what do think?2 m span? I'll see if I can size the next mock up to suit.

And finally in this ramble of mine an idea that may be totally unworkable but here goesneed to do a sketch,I'll have to go to T/T
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Old Sep 04, 2012, 03:52 AM
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Is this feasible?
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Old Sep 04, 2012, 11:40 AM
Just call me crash for short
Quick61's Avatar
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Originally Posted by Stupot46 View Post
Is this feasible?
Sure, but now were talking mitered gears, or as they call them here, bevel gears. Doing that, and using the motor you point up, (I'd suspect the 350 RPM @ 3V one?) both the 3:1 and 4:1 sizes look quite manageable.

To further toss out m 2 cents on what you ask -
"In Kents sketch,with a motor driving the screw instead of a servo,could one of those planetary geared motors in the previous post be used?Possibly direct to the screw."

Again, sure. either with the shaft & pulley like in your sketch or beveled gear drive with whatever ratio you would want. In fact, it would make things simpler.

"In the same sketch at the driven nut-would adverse wing loading in a turn cause the nut to bind?Would it need a slide to keep it square?"

Could be a bit of a problem, but easily addressed by switching from a nut to a threaded coupling nut, which should be ~ 3x longer than a standard nut. As long as you have a good screw and your threading is in tolerance, side force binding is greatly reduced. The only real binding I have ever had with a coupling nut was with varying pitch on a cheaply made threaded rod. Spent more than a few minuets lapping the threads to get it straight.

"Also as Kent points out some sort of limit switch will be needed;judging max/min from the ground won't be easy.
Any thoughts on how to control the sweep from the transmitter,could a three position switch be used?'


The limit switches should be a straight forward affair, Just think 2 way light switch in the parlor on opposite sides of the room. As for the transmitter, your 3 way switch would be what I would use. a couple of micro relays, maybe transistor switches on the coil and a few diodes for safty to insure there is no unwanted polarity reversal. I'll have to put on my thinking cap and recall my past education in this area to do up the schematic and traces for the circuit board so don't be expecting me to toss out something in the next 15 minuets.

"Mark,could you work out the the dimensions of Gs centre section please, at what do think?2 m span? I'll see if I can size the next mock up to suit."

Yes, I can. What would be helpful would be to know what the airfoil is and the root chord. I can't really tell from the pictures of the plan. Also, which drive setup would you want to see in there?

You know it was stated in the recent past that at some point you just have to shoot the engineer and get to building... Well I'm here to tel ya, this one has put on this flack jacket and is ready for a battle. This is one of my most favorite parts of modeling. When it's time for the engineer to go away, I always feel like David Tennant as The Doctor in his last scene, "but I don't want to go."

Mark
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Last edited by Quick61; Sep 04, 2012 at 11:54 AM.
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Old Sep 04, 2012, 03:52 PM
I don't like your altitude
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Mark that's brilliant info,thanks a lot.I know little or nothing about electronics,heck I've only had a couple of powered planes,mostly slope stuff.
You've certainly opened the door to some more sophisticated ideas than the bailing machine we have at the moment
Favourite in my mind at the moment is a direct drive onto Kents shaft and nut.I'm already using an 18mm long threaded insert on a 4mm screw,if I can get some heavy enough ball joints connected half way along that should do it.
The reason I asked about the Gulliver dimensions are mainly to do with the pivot points.From what I've read on swing wings previously,having the pivots as far as practically possible from the airframe centre line lessens the degree of cog movement(this may be from a link Norm posted)
I'm thinking that it will also reduce the amount that the wing"cuts into"the centre section at max and min sweep.
As I said previous I'll speed mk1 up first and then build mk2 utilising the same components
I managed to make the half span of the plan fill the 200mm iPad screen.taking measurements from this I came up with at 2m span-
Centre section-400 mm width
Centre rib- 550 mm
Root rib- 300 mm
Centre sweep- 30*
Wing sweep- 20*
The suggested 2m span is just that- would something smaller be more practical?I'm thinking at 1.5m or so it could be built in one piece,or could the wing be made to detach at the pivot?
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Old Sep 04, 2012, 04:06 PM
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I don't know what happened there,I couldn't display the last part on the edit screen.
Anyway I was looking at the first rib position inboard of the sweep change as a possible pivot point.
Regards Stuart.
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Old Sep 05, 2012, 12:10 AM
Just call me crash for short
Quick61's Avatar
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OK here is the schematic that I cobbled together for the motor reversing with limit switches. OK, basically i found the general circuit on the net and added i the limit switched and safety diodes but hey, why try to invent the wheel when someone is handing you a set of tires and rims. Don't pay much mind to the exact type of transistor labeled there as those were just thrown in based on the Maximum Efficiency listed for the motor and I'm thinking that something in a TO-126 or TO-220 case would serve as a good safety margin as opposed to the little TO-92 case those are in.

If your not getting it at first glance, the inputs "Forward" and "Reverse" come from the receiver. A high (voltage) on one or the other input pins will make the motor run. When a high is put on the Forward, Q1 and Q4 will conduct and when a high is on the Reverse input, Q2 and Q3 will conduct. If both are high or both are low, the motor will not get power. When the limit switch is hit in forward or reverse, the circuit can only take an input for the opposite direction. Simple enough. Now to get this (new to me) software to do the routes for the PCB...

Mark
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Old Sep 05, 2012, 02:46 AM
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Mark,you are an electronic wizard! I understand what you're doing here,the how is completely beyond me.
Couple of pics of the airfoils from the plan;looks a bit slim.I'm wondering about using CDs as the sliding surfaces,maybe onto Teflon.I need to research that a bit.If they work,and we can get a low profile drive,things may start to come together.A crucial part of the design will be linking the wing pivots,along the lines of the chuck glider.Something really rigid will be needed to stop the wings flexing.
Regards Stuart
Ps- regarding airfoils in an earlier post you mentioned mh45/mh60 as being possible candidates?
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Old Sep 05, 2012, 06:48 AM
Herk
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Virginia USA
Joined Jun 2007
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Hi Stuart - I'm wondering what has become of the test glider version of this project? It looked quite promising as a way to explore the concept before you went too far with the big one.

I like Kent's idea of driving the jack-screw directly. Seems simpler and offers the possibility of a more horizontal layout. One could anchor the nut to the static structure and move the whole mechanism, or as Kent detailed it - tie the wing sweep directly to a moving nut. In the latter case the nut would need tabs to run in the tracks - preventing rotation.

In any case, and however you manage to get this working - I'm lurking here - very interested.
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Old Sep 05, 2012, 06:49 AM
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Untitled (1 min 38 sec)

Last fling.I'm going to dismantle this now and have a go at mk2
Stuart
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Old Sep 05, 2012, 07:02 AM
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Quote:
Originally Posted by HerkS View Post
Hi Stuart - I'm wondering what has become of the test glider version of this project? It looked quite promising as a way to explore the concept before you went too far with the big one.

I like Kent's idea of driving the jack-screw directly. Seems simpler and offers the possibility of a more horizontal layout. One could anchor the nut to the static structure and move the whole mechanism, or as Kent detailed it - tie the wing sweep directly to a moving nut. In the latter case the nut would need tabs to run in the tracks - preventing rotation.

In any case, and however you manage to get this working - I'm lurking here - very interested.
Hi Herks,the test glider has left the building!We've had a couple of sunny(ish) days but a bit windy.Today is good,still a breeze but should be ok.I'll report
later.
What you mentioned about the mechanism is the next step.I need to fabricate the central nut/pivot and give it a try with the existing drive set up.I'll get hold of a suitable motor when we decide exactly what is needed.
Regards Stuart
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