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Author Topic: Mick Reeves Lightning build  (Read 60503 times)

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Offline HarryC

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Re: Mick Reeves Lightning build
« Reply #120 on: December 23, 2010, 11:05:56 AM »
But then it is bent the wrong way when the arm rotates 45 degrees each way from centre.
With a longer horn on the torque rod the angle isn't quite so bad.  I think I will chamfer the raised mounts so that the servo sits at an angle with the pushrod.


Offline JimG

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Re: Mick Reeves Lightning build
« Reply #121 on: December 23, 2010, 11:13:37 AM »
Do you have room to raise one end of the servo so it is fitted at an angle? This will bring the servo arm in line with the pushrod.

Jim
Jim Gill
Dundee Model Aircraft Club

Offline HarryC

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Re: Mick Reeves Lightning build
« Reply #122 on: December 23, 2010, 11:23:06 AM »
Do you have room to raise one end of the servo so it is fitted at an angle? This will bring the servo arm in line with the pushrod.

Jim
See previous post!


Offline JimG

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Re: Mick Reeves Lightning build
« Reply #123 on: December 23, 2010, 11:38:31 AM »
Didn't see that before posting. ;D ;D

Jim
Jim Gill
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Offline zippo - is leaving the building

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Re: Mick Reeves Lightning build
« Reply #124 on: December 23, 2010, 11:57:19 AM »
Is there space to mount the servo upside down? If so, it would put the output arm more in line with the tailplane horn. Just a thought - though I'm sure you have already considered that option.
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Offline The Saint. (Owen)

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Re: Mick Reeves Lightning build
« Reply #125 on: December 23, 2010, 12:00:17 PM »
What about low profile servos.  :af
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Proper aeroplanes are powered by engines.

Offline HarryC

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Re: Mick Reeves Lightning build
« Reply #126 on: December 23, 2010, 13:41:08 PM »
Is there space to mount the servo upside down?
neat idea but no, the assembly is fairly close to the bottom of the fuselage so the amount of headroom is limited

Quote
What about low profile servos.
My experience of low profiles is that they are low below but not above the mounting line.  If there are any that are low above the mounting line, and are digital and of the required spec and made by Futaba or JR then they will be very expensive!  Multiplex don't make any, and I won't allow anything other than Mpx, JR or Futybut servos in my expensive models.


Offline Tiger

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Re: Mick Reeves Lightning build
« Reply #127 on: December 23, 2010, 14:17:08 PM »
I don't like any of it..................

It all looks like a bodge to me..............

Sorry to be so negative, but there are so many bad things here. I don't like the long brass ball ended screw, Have you thought what the dia of the solid rod might be that runs up the centre of the threads ? If it's an M3 thread then the O/D is going to be about 2.8/2.9 the thread depth is 0.3 mm, both sides. So, the solid bit of BRASS wire up the middle is at best 2.3 dia but could be 2.2 or even 2.1. The point that it enters the torque tube is the point of highest stress.
I wouldn't have it ........................chuck most of it in the bin ! !
Redesign the method of attaching the horns to the torque tube in such a way that it improves the geometry with the servos.

You need an engineer with some machines ................... sorry I'm busy just now.

All, just my opinion, of course  :D  

Watching with interest. :af

Tally Hooooooooooooooooooooooooo  :uk:

Andrew

  
« Last Edit: December 23, 2010, 14:24:43 PM by Tiger »
I do have my failings................... fortunately, making mistakes is not one of them.

Offline HarryC

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Re: Mick Reeves Lightning build
« Reply #128 on: December 23, 2010, 14:30:15 PM »
I don't like the long brass ball ended screw, .....................................

I wouldn't have it ........................chuck most of it in the bin ! !
As you've probably gathered Andy, it is on its way to the bin!   ;D And check it again, it is M4 not M3, and has been replaced by M4 high tensile steel bolts.
How's the Rafale coming along?
« Last Edit: December 23, 2010, 14:39:16 PM by Mpx »


Offline Tiger

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Re: Mick Reeves Lightning build
« Reply #129 on: December 23, 2010, 15:03:19 PM »
OK....................M4 is a bit better, steel is better than brass, the core dia of M4 is 3.14 mm.
An accurately machined fitted ally collar incorporating the horn, pinned and 'Loctited/Hysoled" to the torque tube would be much better.

The Rafale has gone back home to France, waiting for me.  :D

Tally Hoooooooooooooooooooooooooooo  :uk:

Andrew
I do have my failings................... fortunately, making mistakes is not one of them.

Offline Tiger

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Re: Mick Reeves Lightning build
« Reply #130 on: December 23, 2010, 15:07:59 PM »
Or............. has the torque tube sufficient wall thickness to machine a tread on it. The collars could be 'screwed on' and Loctited then...............

T. H.  :uk:

Andrew
I do have my failings................... fortunately, making mistakes is not one of them.

Offline HarryC

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Re: Mick Reeves Lightning build
« Reply #131 on: December 23, 2010, 15:25:00 PM »
Not sure what you are meaning Andy, it's a rod not a tube, solid aluminium about 10mm in diameter with an M4 threaded hole right through it for the bolt that forms the horn.

Offline Gordon W

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Re: Mick Reeves Lightning build
« Reply #132 on: December 23, 2010, 21:32:03 PM »
Hereís Keith Whiddettís solution for operating the all-moving tail on his Gnat.  Itís a modified JR aluminium servo arm bored out to fit the shaft.  The pinch bolt allows adjustment of the armís position, and it looks as if thereís a grub screw for final locking.  The shaft is 6mm dia, so this actual solution isnít usable on your 10mm shaft.  But a larger pair of horns could easily be knocked up from a bit of ally plate using a hacksaw, file, pillar drill and taps.

This brings back memories of making replacement conrods for my Elfin 2.49 back in the early Ď60s.

Gordon

Offline Tiger

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Re: Mick Reeves Lightning build
« Reply #133 on: December 24, 2010, 00:44:49 AM »
Not sure what you are meaning Andy, it's a rod not a tube, solid aluminium about 10mm in diameter with an M4 threaded hole right through it for the bolt that forms the horn.

OK..............that's even better then, you've got something really solid to fix to. The idea shown in Gordon's post is the sort of thing I'm thinking of.

Tally H  :uk:

Andrew
I do have my failings................... fortunately, making mistakes is not one of them.

Offline wayne the iceman

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Re: Mick Reeves Lightning build
« Reply #134 on: December 27, 2010, 14:34:36 PM »
hi guys
 been following the thread with interest ,dont want too be the profit off doom here, but my mate built well it got 3/4 built before he scrapped it if im honest, problem after problem ,and i also had the same problem with his 1/4 scale spit nothing fits or plans wrong , you may as well get your money and put a match too it  :banghead:,   unless you have nothing better too do with your time than  solve problems that should have been tryed and tested you will need a whole lot of time and nerves of steel not too mention a cement mixer too fill the fuselage :'', anyway best of luck you will need it ,
          regards and happy landings  :uk:

Offline HarryC

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Re: Mick Reeves Lightning build
« Reply #135 on: December 27, 2010, 17:04:38 PM »
Here's the completed tailplane assembly.  I stayed with clevises at the servo end, the raised servo has had its mountings angled so that the plane of the servo arm is in line with the pushrod.  The pushrod from the raised servo will not be at right angle to the horn from the torque rod but any tiny differential can be taken out in software during the final setting up.  You can see my new attachments to the torque rod are very substantial - M4 high tensile bolt screwed all the way through from below the supplied solid aluminium rod, double safety from the nyloc nut then on top which also acts to soak up the large lateral slack in the slot in the plywood, then the steel M4 clevis with ball link bolted through with M3 through the arms and ball, thread tapped into the clevis arms and double safety from M3 nut.  I don't see that lot coming apart!  It is all very solid and slop free, the only movement is the servo gear lash.


Offline Gordon W

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Re: Mick Reeves Lightning build
« Reply #136 on: December 27, 2010, 20:27:20 PM »
It does look plenty strong enough, though I always aim for a far longer horn than servo arm to give the servo more mechanical advantage, and also to use up as much of the available pot movement as possible for best resolution.  I've had pots wear a bad spot in the middle through using too little of the available movement.  I guess that the space available above the linkage is restricted, and in any case I'm sure that you'll have used your spreadsheet to check that what you have is OK in terms of torque.  The swept hinge line is presumably close to the 25% chord line of the tailplane for minimum effort in moving it.

FWIW, I googled your S3050 servo to find the specs, and discovered this rather good database which appears to have the specs of all servos ever made, which I've now bookmarked   http://www.servodatabase.com/servo/futaba/s3050

Gordon

Offline HarryC

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Re: Mick Reeves Lightning build
« Reply #137 on: December 27, 2010, 22:36:46 PM »
It does look plenty strong enough, though I always aim for a far longer horn than servo arm
The lengths are dictated by the tailplane travel required, I am already running the servo travel at equivalent to a JR tx turned up to 110% and am only just getting the required travel.  Can't make the tailplane horns any longer.  They are a lot longer than they look in the photos, bear in mind the mid point is 5mm inside the torque rod, and the rod is below 6mm ply, so total horn length is something like 20 - 25mm

Offline lozza

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Re: Mick Reeves Lightning build
« Reply #138 on: December 28, 2010, 10:24:53 AM »
I'd like too comment but im not a modeller   :'' :''

Offline HarryC

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Re: Mick Reeves Lightning build
« Reply #139 on: December 29, 2010, 11:03:08 AM »
It does look plenty strong enough, though I always aim for a far longer horn than servo arm to give the servo more mechanical advantage, and also to use up as much of the available pot movement as possible for best resolution. 

I measured it last night Gordon, my control horn is 28mm compared to the MR brass one which is 24mm, and servo arm is 17mm.
There will now be another break in progress while I finish off another two models that have been hanging around part-done for a while (prop jobs, hush, keep it quiet!)

Offline Gordon W

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Re: Mick Reeves Lightning build
« Reply #140 on: December 30, 2010, 23:33:47 PM »
The angle at which you've taken the pics masks the relative lengths very well, Harry.

My li'l scratchbuilt EDF Lightning had the same elevator horn length as yours, but the servo arm was only 14mm long.  I note from an old RCGroups thread I ran about mine that it did need more elevator movement than I expected, though I didn't note down the figures, possibly up to 15deg each way, and also that following first flights I zeroed the expo as the elevator response was too soft with 20% expo.

There are plenty of MR Lightnings flying around successfully though, so obviously you'll use the recommended elevator movements.  The MR Ltg did help me in one important respect ...  I learned from one forum discussion on it the CG as % of root chord.  I'd set my model's CG too far forward, and when I moved it back to the Reeves location its handling was much improved.

I've never seen a MR Lightning flying in the flesh, so hope you get yours to CJ, Merryfield or Westonzoyland  (if Westonz..  does begin holding jet fly-ins) in the future!

Hurry up with those prop jobs (I'm in the middle of building one too).

Gordon  

Offline HarryC

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Re: Mick Reeves Lightning build
« Reply #141 on: December 31, 2010, 09:32:24 AM »
There are plenty of MR Lightnings flying around successfully though, so obviously you'll use the recommended elevator movements.
I am hoping it is enough Gordon, because I can't get any more.  Although I could wind the clevis further down the horn, the lower pushrod would conflict with the raised servo.  Why not lower that servo?  Any lower and its pushrod that goes over the top of the lower pushrod, will come into conflict with the lower rod!  The only solution would be to put aside the ply plate and cut a new one with the raised servo moved further back so that it is no longer under the lower pushrod.  Then the clevises could be wound down and more travel obtained.  But since I have, just, got the travel specified I have to wonder if it is worth it.

Offline Gordon W

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Re: Mick Reeves Lightning build
« Reply #142 on: December 31, 2010, 22:33:54 PM »
Whilst what you have there looks strange, Harry, I guess that it must work.

While he was still building it, I asked Shane Harding how he actuated the elevators on his 1/6th scale scratch-built all-balsa Lightning.  I seem to remember that his two servos were located aft of the tail bearings, as were the actuators on the full size - pic attached.  That way the pushrods didn't have to cross.

However, I too wonder if changing the installation in your model would be worth the effort if everyone else is getting it to work successfully.

Edit.  I've just looked at your pics again and your servos are aft of the bearings!  ::)   Possibly repositioning the horns further outboard (eg inside the long elliptical cutouts) and re-orienting the servos would let the servo pushrods connect without crossing.  Also, maybe Shane's model's pushrods did cross after all!

I give up  $%&  :banghead:

Gordon
« Last Edit: December 31, 2010, 22:43:58 PM by Gordon W »

Offline HarryC

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Re: Mick Reeves Lightning build
« Reply #143 on: February 08, 2011, 09:21:30 AM »
I have finished only 1 of the 2 other models taking up space in the workshop but couldn't wait to get back to the Lightning so I have been working on the tailplane assembly again.  The tailplanes' neutral position is leading edge down, and since I can't get any more travel from them than the required amount, it is important to mount the assembly into the fuz at the neutral angle as there is no spare travel to use to adjust the neutral point.  After much fiddling to adjust the bearing rod exit holes in the fuz, and needing 3 arms, I have tacked an end of the ply plate into place in the fuz with 5 minute epoxy.  In the next session I will bolt on the front fuz and the wings to check that the tailplane assembly is correctly aligned, and if it is I can squirt hysol around the joint. 

Offline HarryC

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Re: Mick Reeves Lightning build
« Reply #144 on: February 10, 2011, 10:15:45 AM »
I have encountered an unexpected problem with the tailplane pushing into the fuselage at down elevator.  My other jets with swept tails have the pivot straight across the fuz, but the Lightningís pivots are highly swept as seen in the photos above.  This means that any tailplane ahead of the pivot rotates inwards as well as up or down.  When the leading edge goes down it swings in but so does the curve of the bottom of the fuz so they donít meet, however when the l/e goes up for down elevator the l/e root swings in and hits the fuz.  Spoke to Jim at MR. who mentioned the gap between fuz and tailplane is not scale, itís about 3/16Ē and looks massive, and still the tailplane hits the fuz.  Jim suggested either re-aligning the pivot mounts to sweep the tails back another degree thus bringing the l/e root even further away from the fuz, or sanding material off the l/e root of the tails.   I wonder how the full-size does it, because there isnít some big gap between the fuz and tails.  Maybe it had hardly any down elevator travel?  Or is the full-size fuz pinched in a bit above the tails l/e root and the MR model isnít?  It explains why the root of the tailplanes have a stagger at the pivot, the root ahead of the pivot being further out than the root behind the pivot.  That gives the tail ahead of the pivot a clearance to allow for down elevator, the fuz at that point is built out to fill the gap.  Perhaps the MR model doesnít have the same amount of stagger in the root that the full-size does?  That would give me an option to solve it and make it look better, remove some tail root ahead of the pivot and build up the fuz at that point to reduce the large gap.

Offline JohnMac

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Re: Mick Reeves Lightning build
« Reply #145 on: February 11, 2011, 07:26:54 AM »
Hi Harry, A photo of the problem might help. I have the as yet unstarted Airworld kit. Since the pivot is not yet in place I am unable to be sure but it looks as if the bulge in the mounting, and the sweep angle will ensure that the tailpllane never hits the fuselage. I had a look on the web for photos of this area but did not find anything that shows the area well enough.
Regards,

John

Offline HarryC

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Re: Mick Reeves Lightning build
« Reply #146 on: February 11, 2011, 09:36:54 AM »
I had a good look at everything last night and worked out how it is all supposed to work on the full size.

Because of the swept pivot, the tailplane ahead of the pivot moves inwards.  That's why E.E. designed a big step in the root at the pivot, so the root ahead of the pivot is stepped out away from the fuz to allow for its inward movement.  To fill the gap at neutral, the fuz has a bulge along the chord of the tailplane root ahead of the pivot, the curve matches the path that the root takes.  Behind the pivot the root swings outward, and the fuz has a raised scallop to match it.

On examining my tailplanes, the root behind the pivot is well away from the fuz at all points of travel, the root ahead of the pivot is well away from the fuz at neutral but rapidly swings into the fuz at down elevator.  The fuz does have the raised bit and scalloped bit.  Part of the problem is that the roots of the tailplanes are not parallel to the fuz but are slightly biased in at the l/e and out at the t/e, so the l/e root is even further biased to swing into the fuz.  What is needed is a change to the pivot alignment, just a degree or two more sweep back.  Rather than try and fudge the mounting holes in the existing ply plate it would be much better to make a new one.

Playing with it all exposed another problem.  By holding the tailplane tips, it takes little force to bend the entire tail back and fore.  The reason turns out to be a combination of two things.  The solid aluminium rods pass through brass tube which are secured to the ply plate by copper plumbing straps - see previous photos.  The play in the aluminium rod to brass tube is tiny but when magnified all the way out to the tips of the tailplane it is become noticeable.  The major part of the motion though is simply the copper plumbing strips flexing very slightly, and once again the distance out to the tailplane tips greatly magnifies the travel.  Is this a problem?  With perhaps 150mph airflow and a lot of tailplane travel presenting a large area to the airlfow, I should think it is a problem!  So that really has to be replaced.

Given all these items that need dealt with I am going to make a completely new ply plate, and this time fit two ball-races (ex-F100 tailplanes) per tailplane.  That will allow me to adjust the pivot sweep and give a solid, slop free mounting.  I will also adjust the positions of the servos so that the pushrod of the lower servo isn't crossing the higher servo and limiting the travel, so I get more scope for adjustment later on.  Work is already under way, the plate has been cut and shaped, and has been marked for the new alignments and necessary slots and holes to be cut at the next session.

Offline HarryC

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Re: Mick Reeves Lightning build
« Reply #147 on: February 19, 2011, 18:59:00 PM »
Here's my revised tailplane mounting.  The brass tubes are a nice fit in the ballraces I have, so I have cyanoed the aluminium rod into the brass tubes.    As you can see I have staggered the servo cut-outs, so the raised servo is moved away from the pushrod of the lower servo and there is no conflict any more, so if needed I can screw the horn further down to the torque rod to get more travel.  It all weighs more than the original since there is more metal and wood, but the result is a solid mounting not relying on copper plumbing straps, less friction of the ball races compared to the aluminium rod on the brass tube, no slop of the brass tube in the ballraces compared to the aluminium rod floating in the brass tube, no conflict of the pushrod and servo so better adjustment of the travels, and slightly increased angle of sweep back to make the tailplane roots a better match against the fuselage

« Last Edit: February 19, 2011, 21:02:04 PM by Mpx »

Offline selleri

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Re: Mick Reeves Lightning build
« Reply #148 on: February 19, 2011, 19:25:43 PM »
Looks ace!    :af
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Offline HarryC

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Re: Mick Reeves Lightning build
« Reply #149 on: September 06, 2011, 17:00:11 PM »
Progress has been slow as I have not had much time with the model, and some of the time has been used trying to solve things I have eventually abandoned.

I spent a lot of time trying to install a brake parachute.  The chute housing doors on the Lightning don't hinge outward but are sliding doors that run upwards on curved rails inside the fuselage and trying to recreate that and fit a release servo was taking a lot of time, plus there is not really any room in the top of the fuz for a cable release mechanism.  In time I may come back to it and try again but for now that idea is abandoned.

I did not like the design of the rudder pushrod, it is hidden and so is "scale" but I did not have much faith in it and have cut into the fin to fit a servo under a hatch with an external pushrod to the rudder, choosing a fast servo to make the most of the gyro.
The aileron pushrod connects in a hidden way to the aileron, but the small horn distance and amount of travel required means either the pushrod connects to the servo almost against the centre post which isn't going to work, or the servo travel is cut to a fraction of the normal range which wastes torque and loses resolution or precision.  So once again i have changed to an external visible horn, each aileron having a pair of carbon fibre horns with an M3 ball link bolted in between them, the length of the horn designed to make perfect use of the servo travel, and once again fast servos to make best use of the gyro.  I continue to use Olivier Nicolas's spreadsheet to determine min torque requirement's and design the control and servo arm lengths.
Finally I did not like the flap horn, same reason as aileron and rudder, also its position is where a normal size servo will not fit into the wing as the box around it formed by ribs, false t/e and wing joiner tube is too small.  the horn is right at the inner end of the flap so I have made a new longer horn half way along the flap where there is room for a servo.
Aileron and flap servos have been mounted on 1/8" ply hatches and I am now sheeting the wing around them.

Wing utlities have to be installed prior to adding the bottom sheeting, as all cables and tubes have to be fed down the wing joiner tubes and can't be easily got at the inner ends of those tubes once the sheeting is done.  I intended fitting the large doors over the main wheels but the wheel and the cranked leg over the wheel are deeper than the wing by quite a bit, so the only way to have a door is for it to be very curved or have a large blister and it would look as bad as having no door, so I have opted for no door, which is a real pity.  I did a final test of the main retratcs with air pipe installed before sheeting over and one had developed a massive leak around the piston outlet so both units came out to be stripped and cleaned yet again.  I have had a serious think about getting the e-retract (formerly LADO) conversion for them but the nosewheel can't be converted as far as I can tell.  I have the main wheel brake optional set but the legs are very long and the added weight of the brake units and their steel disc would be quite a load on the lever arm so for the moment I will try the nosewheel brake.

The main leg oleo scissor links have no limiter, so the open fully when there is no load on the leg, and that locks them open so the leg can't compress on landing.  To solve that I cut a short length of 4mm piano wire, cut a groove in each end with a diamond wheel and soldered it to the inside of the scissor link so it prevents the link closing completely against the leg and locking fully open.  Then I measured the leg spring, determined it was far too soft and calculated the spring rate required and the pre-compression, removed the MR springs and installed new springs of approx the correct rate (vastly stiffer) with a dowel cut to give the correct pre-compression.

I got tube from MR and added it to the inside of the fuselage where the wing joiner tubes come in and bonded them to a large area with glass cloth, so the load from the wing no longer applies itself to a tiny edge of fibreglass but should hopefully be spread well around.

The canopy internal frame is from routed 1/8" liteply, few of whose parts seemed to fit one another and needed a  lot of sanding or adding to, to make fit,  the canopy was then bonded on, and filler applied to make a good seat to the fuselage.

All fuz formers and engine mount are in place now, the reheat rings from Wendler Modellbau have arrived and the next task when wing sheeting is done is to fit the jet pipe and reheat rings.

Offline Lee Wilson

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Re: Mick Reeves Lightning build
« Reply #150 on: September 06, 2011, 18:01:36 PM »
great to see an update. Still watching :af
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Offline HarryC

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Re: Mick Reeves Lightning build
« Reply #151 on: September 15, 2011, 18:54:24 PM »
First photo shows the 4mm piano wire bar soldered across the inside of the scissors (is that the correct name?) to prevent them going completely flat and locking.

Second photo shows an adaptation inside the fuz.  The aluminium wing tubes seem to rest only on the very thin edge of the f/g fuz so I added these phenolic stubs with hysol and since the photo was taken they have been backed up with galss cloth to spread the load.  Then I routed a tiny sliver off the hole in the fuz edge so that the tube really does take the primary load and spread it around, rather than the load all appearing at one tiny bit of edge of the f/g skin of the fuz

Offline nmacwarbirds

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Re: Mick Reeves Lightning build
« Reply #152 on: September 15, 2011, 20:35:34 PM »
Charlie,
It looks as if you are making progress (slowly), we have the phenolic tube on our Lightning
tied into the formers also, plus we have 1/4 ply plates attached to the inside of the fuz with carbon
the phenolic tube runs through that. Your system does not look quite robust enough, IMHO.

I hope to see your Lightning fly soon.

Regards Phil G.
Never in the field of human conflict was so much owed by so many to so few.
Coltishall Memorial Flight. 242 Sqn.

Offline HarryC

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Re: Mick Reeves Lightning build
« Reply #153 on: September 15, 2011, 21:48:07 PM »
Charlie,
It looks as if you are making progress (slowly), we have the phenolic tube on our Lightning
tied into the formers also, plus we have 1/4 ply plates attached to the inside of the fuz with carbon
the phenolic tube runs through that. Your system does not look quite robust enough, IMHO.

(It's Harry!)
That's interesting Phil because I have been wondering about a single 1/4" ply plate along the fuz going past both the tubes, the F-100 had them and it would be a good load spreader.  What I have done is put a thick coating of g/f wound around the tubes and then spreading out over the fuz to spread the load, but I will have another think about the ply plates.

Offline HarryC

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Re: Mick Reeves Lightning build
« Reply #154 on: October 04, 2011, 22:12:38 PM »
I suddenly had a new idea about how to mount and operate the doors for the brake parachute so I have gone ahead and built it and it works.  I had been trying to emulate the full size where the doors are on runners along the inside of the fuselage skin, and though I believe I had worked out a method to do it, it was not easy as it had to be built accurately and built in place which made it difficult to do accurately.  Instead what I designed is doors that are fixed to a pivot point, pulled up by 0.06N/mm springs and held closed by a hatch latch which will be operated by a small servo.  The whole thing can be built outside the model and slides in through the rear lower pipe opening.  The photos should pretty much explain it.  Inside and out is lined with extremely thin plasticard as its shiny side is very low friction.  The box is just big enough, and lined with the low friction plasticard, so the chute drops out under its own weight and doesn't need a spring-loaded ejector mechanism.

The reheat LED rings are larger diameter than the MR scale jet nozzles so I had to make new nozzles a bit bigger and lacking the scale slight taper at the rear end.  I made the new nozzles from MR Proskin.  I started by wrapping 3 layers of 1/16" balsa strips around a lemonade bottle to make 2 rings which gave the correct diameter to then wrap proskin around them and make a nice tight fit for the reheat rings.  See last photo.

Offline HarryC

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Re: Mick Reeves Lightning build
« Reply #155 on: November 11, 2011, 18:59:30 PM »
The tailplanes are fixed to the aluminium pivot rod by sliding their brass tube over the pivot rod, and then putting in an M3 bolt through a hole in the brass tube into a threaded hole in the pivot rod.  I did not feel that a mere hole in the brass tube was firm enough to resist any turning on the rod due to slight oversize in the hole, or to prevent slowly eroding the hole to become bigger over time.  I also did not like just one bolt holding the tailplane on.  The first job was to improve the existing hole in the brass tube, by making a deep collar.  I did this with a brass tube of 3mm i/d and a cone of epoxy around it.  Photo shows it before cutting back to almost flush with the surface of the tailplane.  This means that the bolt is in a tube rather than just through a hole in the thickness of the wall of the main brass tube.  Not shown in the photo is the second one I have since installed in a gap between the tailplane and fuselage, having drilled and tapped a second hole in the aluminium pivot rod.  So I have gone from a hole in a brass tube with one bolt, two two bolts in deep tight fitting collars.


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Re: Mick Reeves Lightning build
« Reply #156 on: November 11, 2011, 19:15:59 PM »
This shows the catch for the brake parachute doors, looking forward from the jet pipes.  It's a standard hatch catch, but mounted on two 1/8" beams to keep it off the fuz.  In the gap, a bit of wire is connected to the finger toggle.  A small amount of the finger toggle sticks out of a slot in the fuz.  The wire connects to a mini servo in the tailplane servo bay.  The system is that the servo only needs to pull, not push on the spring loaded catch so it only needs a wire not a rod.  By having a bit of the finger toggle stick out of the fuz, and being only connected by wire to the servo, the catch can be manually operated such as for closing up the doors when loading the 'chute, without having to have the radio on or operate the servo.

I have two servos to be operated by one switch - the door opening, and the cable release.  Both need to do different things which used to need two channels but by having programmable (Weatronic) rx I can use one Tx channel and put the curves in the rx.  So the door servo has a top hat curve so that when I operate the chute opening switch, the servo pulls the door catch open for a second, then to save it continuing to hold against the powerful spring it goes back to the closed position and by then the doors have sprung wide open and are out of the way.  For those who like such things, photo of the servo rx program shown (I know about screen printing but the rx software is on another pc and i can't be bothered emailing it to myself!)

Offline HarryC

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Re: Mick Reeves Lightning build
« Reply #157 on: November 11, 2011, 19:37:40 PM »
The other end of the brake chute is the cable catch, which is above the fuz behind the rudder, in a tube raised slightly out of the fuz.  I made the tube from brass tube, at the back end reinforced by soldering 2 more layers of smaller tube into it.  Two holes were drilled below centre and a piece of piano wire is soldered across the inside.  Further forward, a balsa insert carries a concentric brass tube of much smaller diameter which carries and guides a piano wire driven by a servo.  It's a copy of this idea, which will let you understand how it works http://www.modelmaniacsonline.co.uk/products.php?CatID=430&SubCatID=450&ProductID=5788&Title=Multiplex+Aero-tow+coupling&ManCode=723470.

The fuz at this point has to take the considerable strain of the force from the chute so I have laid up a large mat of carbon cloth inside.

The programming gets more complicated here.  It is vital not to accidentally knock the switch and open the parachute in flight.  I also need to guard against the chute doors breaking open, servo going nuts etc and opening the chute in flight.  Having a switch that allows cable release is fine but by the time you realise what has gone wrong, try and remember which switch it is and fumble for it while trying to control a Lightning that is coming to a halt in the air is not good.  I am going to copy the concept and program that I used on the F-100 and which worked well.  The cable does not need to be attached during the flight, the only time the cable catch needs to close is when I command the chute to open.  So instead of the cable being attached before flight, it is simply held in place in the catch opening.  When I give the command to open the chute doors, the cable servo moves to close the catch and capture the cable.  So if the chute gets out uncommanded in flight, it is not actually attached to the model and falls harmlessly away.  To prevent accidental knocking of the switch, I use the Tx logic commands to require that 4 controls are in the right place in order for the door and cable servos to operate.  The wheels must be down, the throttle at idle, another switch nominated as the chute arming switch put into the ON position, and finally the chute switch moved to ON.  Should I manage somehow to get all 4 like that on finals and thus accidentally open the chute, all I have to do is cancel one of them, such as opening the throttle, and the cable servo immediately releases the cable.

Offline HarryC

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Re: Mick Reeves Lightning build
« Reply #158 on: November 11, 2011, 19:42:38 PM »
This shows 1/4" ply reinforcement added to the fuz at each of the wing tube entry points.  The phenolic tube captures the wing tube and spreads the load around itself, it is then bonded into the hole in the ply reinforcement which spreads it out over a big area.  The ply plate is about a foot long and about 4" wide.

Offline HarryC

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Re: Mick Reeves Lightning build
« Reply #159 on: November 11, 2011, 19:56:17 PM »
The fin is removeable.  It has a tube installed into the fin moulding which is supposed to go into a brass tube inside the fuz which is held to a former by two copper plumbing straps.  A vertical plate sticks out of the fuz into a slot in the fin and has a screw through the fin into the plate.  A small wire stub at the front of the fin prevents turning.  I felt it would be right to add some more to this plan.  So I installed an aluminium right angle channel piece sticking out of the fuz, tapped for two bolts to hold the fin in place.  At the front rather than the anti-turning stub I installed a second tube right up inside the fin and a mount for it inside the fuz.  Way down at the back of the fin I installed a wire stub to prevent the rear of the fin, where the rudder is applying its force, from twisting.  Photo shows the former with brass pipe and copper straps, and in foreground the pipe I installed to take the additional pipe from the fin.

The second photo shows an additional idea of mine that, starting with the Lightning, will be installed on all my jets.  Its a ply plate high in the spine, with an M3 blind nut in it.  There is a corresponding 3mm hole in the top of the spine.  Why?  It is a video camera mount.  I have had a lot of fun with on-board videos from the key-fob cameras velcroed to my jets, but the velcro has to stay on the model otherwise pulling it off pulls the paint etc, and you can't always velcro in the best spot e.g. as far back in the centre as possible, due to the rounded spine etc.  So I will make a small ply plate with the camera on one side and an M3 bolt on the other, and the bolt just pops through the discrete 3mm hole in the top of the spine and winds into the mount inside.


 

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