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Author Topic: Mick Reeves Lightning build  (Read 60525 times)

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Offline JohnMac

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Re: Mick Reeves Lightning build
« Reply #80 on: September 26, 2010, 08:31:45 AM »
Hi Harry,
No experience of flite metal as yet but I have heard the same stories of it being delicate. As for the solartex hinging personally I wouldn't use it as I am not convinced it will stay in place permanently. Solartex always "moves" to some degree on my models in the past. Heat and cold will affect it I suspect.  Personally I will use chunky plastic flat hinges like the large Kavan type and put them in at an angle (in side profile) into balsa blocks.  Only the knuckle then will be at skin level and there is a bit more "meat" to take the strain on the hinges.

As for undercarriage sequencing, I have yet to discover the perfect system. There are a number of issue regarding using servos for doors and legs that I will mention. You may already be aware of these.
The first point is to use a separate battery for the gear system to your radio. The chances of a servo stalling are quite high and the result could be a fire. This happened to me a long time ago and it made a hell of a mess. I would fit a fuse!

Obviously UC systems take a lot of hammer on jets and things can move. They certainly wear. Getting the movements just right on the servos is usually critical, and if the system gets a knock or just wear, the linkages may need regular adjustment. An air ram on the other hand is far less critical; you can overdirive a gear door onto the stops with impunity, and if it does all snarl up, it won't mind a bit, nothing will burn out.

Not that I am a big fan of air systems, I just think that on balance they are the lesser of two evils.
Probably of no practicle value for your current project but at Jetpower there where a number of people selling electric retracts. Behotec had a large range and Jets Munt had some on there stand. There where others too. Nothing new here you say except the controllers are smart, progammable, current limiting devices. So if a leg gets jammed, it stops and will reverse direction when you select the opposite sense on the retract switch. The legs move at scale speed too.
Regards,
John


Offline HarryC

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Re: Mick Reeves Lightning build
« Reply #81 on: September 26, 2010, 09:19:20 AM »
Good points on the servo for doors John, I will stay with air rams, I have plenty of them looking for a home.
In this last week I have been thinking about electric retracts for the Lightning especially when I spotted Grumania now stocks Lado.  But I recall a recent thread from rcu which discussed electric retracts and some people gave good reasons for not using them.  Equally there are good reasons for not using air retracts, so for the moment I decided to stay with what we know on an expensive and prized model and let other people troubleshoot and prove electric retracts.  In 1986 I bought a pair of electric mains from MR himself at the Nats to go in a Royal Bearcat, I sold everything off before I got round to using them, but on the bench they were the best retracts I have ever seen - scale speed, staggered timing, adjustable endpoints, very powerful.  He doesn't make them now, but makes air retracts for his models, there has to be a reason why!

Offline Alex48

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Re: Mick Reeves Lightning build
« Reply #82 on: September 26, 2010, 10:28:10 AM »
Hi Harry

I use the Airpower Multi Function Valves on all my builds, the last 6 models I've built have had them.  Work very well as long as you use water traps on your compressor and don't leave the tanks full when in storage!  They do Brake, Gear, Doors, Failsafe and all timings are adjustable.  Not everyone's cup of tea but I really like them.  The failsafe saved one of my models from a belly landing on tarmac  :)


Offline HarryC

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Re: Mick Reeves Lightning build
« Reply #83 on: September 26, 2010, 17:50:47 PM »
I have considered them Alex, but the thing I don't like about them is so many items in one box, if one goes wrong you have the expense of replacing the entire box rather than the small cost of replacing just one small servo or valve.

Offline Alex48

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Re: Mick Reeves Lightning build
« Reply #84 on: September 26, 2010, 20:08:34 PM »
Sounds sensible...

The unit I had a few years ago that went funny Ali just replaced free of charge  :)


Offline JohnMac

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Re: Mick Reeves Lightning build
« Reply #85 on: September 27, 2010, 07:25:24 AM »
Interesting point about the water trap Alex, but where do you get them please? I have one in my current F14 build.
Harry I think people saw the benefits of electric retracts long ago. The problems where as I have already described with stalling them and drawing large unfettered currents. The second problem was the limit switches which back in the day used electro-mechnical micro switches. I have these on my BT Spitfire and they are the MR units you described. Setting up and maintaining these switches is a lot off work and a bumpy landing or engine vibration can cause them to go out of spec.
The electronic controller overcomes the stalling problem and they now use solid state switches (at least one of the companies who sold them told me this and they make the electric bits for the Behotec range). You are right about Ilya selling them too. He had them on his stand along with a new scale Eurofighter Typhoon.
« Last Edit: September 27, 2010, 08:04:02 AM by JohnMac »

Offline HarryC

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Re: Mick Reeves Lightning build
« Reply #86 on: September 27, 2010, 09:34:21 AM »
I got a water trap for my compressor from Ali, he has 2 brands though they look identical apart from colour.  Not sure how well it works, there seemed to be as much water coming out of the trap as was going in!

One criticism I read of electric retracts is that if any grit gets onto the screw, it jams when it reaches the nut.  Any grit on an air piston rod simply gets pushed along by the cylinder when the rod moves.  Presumably you have not suffered that in your use of them?

I looked at Behotec's website retracts but didn't see electric ones, have you a link?  I'm a bit iffy about Lado as they have a poor reputation on rcu for not delivering orders for months, though if Ilja has them in stock there is no risk but then the next problem is they don't have a noseleg of the correct retraction angle so it would probably still have to be air driven.  "Down and Locked" have started making electric retracts but not been going long enough to hear anything about them.

I will continue with the air system for now.  They can be incredibly reliable, like my F-86 retracts and doors which have never failed and had zero maintenance, in 6 years.
« Last Edit: September 27, 2010, 10:05:53 AM by Mpx »


Offline Pat Barnes

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Re: Mick Reeves Lightning build
« Reply #87 on: September 27, 2010, 18:24:44 PM »
Hi Harry

I see that gear doors are a hot topic for everyone! I've just spent ten days sorting the doors on my Raptor, and hopefully have a reliable setup now! Unbelievable the amount of fiddling that went into setting them up to work properly! My legs are air up spring down, and I have used servos on each of the doors through a jetronics sequencer, which works pretty well. My only concern is the pull pull steering cables - I hope they don't snag on any of the hinges or servo linkages now filling the tight nose leg bay!  Sadly there is no space for any of the nose steering methods discussed here, so I have to stick with the cables!

Personally, I like the air systems, so I think you are going the right way with yours. Good luck with the setting up - I hope you have more space to work in than I did!

PB

Offline HarryC

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Re: Mick Reeves Lightning build
« Reply #88 on: September 27, 2010, 19:39:17 PM »
Doors always seem to be a major source of trouble.  One thing to watch out for is that legs sometimes take longer to retract in the air than they do in the workshop so it is a good idea to program a longer delay time for the doors for the test flights.
Pat, my experience is that if the steering cables are loose enough to snag on anything, they will, and that prevents the leg from coming down properly and makes it turned off to one side.  On my Starfighter they would even snag on the rounded ball link covers on the door's air rams.  If you can, pull the cables out of the way with the cable tie/heatshrink method.

Something that would concern me about electric retracts is their power source.  Despite having current cut-out, I would not like them to be drawing from the radio battery.  Splicing in an external battery is easy isn't it.  But is it always possible, for example with my weatronics rx with the regulated output taken off 2S lipos, does the external battery have to match the Rx voltage output since they will be sharing the same negative lead to complete the circuit for the data signal?  Or will the two systems work independently, allowing a simple 4 cell nicad to power the retract while sharing the negative lead with whatever output the rx has?


Offline JohnMac

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Re: Mick Reeves Lightning build
« Reply #89 on: September 27, 2010, 22:38:00 PM »
Doors always seem to be a major source of trouble.  One thing to watch out for is that legs sometimes take longer to retract in the air than they do in the workshop so it is a good idea to program a longer delay time for the doors for the test flights.
Pat, my experience is that if the steering cables are loose enough to snag on anything, they will, and that prevents the leg from coming down properly and makes it turned off to one side.  On my Starfighter they would even snag on the rounded ball link covers on the door's air rams.  If you can, pull the cables out of the way with the cable tie/heatshrink method.

Something that would concern me about electric retracts is their power source.  Despite having current cut-out, I would not like them to be drawing from the radio battery.  Splicing in an external battery is easy isn't it.  But is it always possible, for example with my weatronics rx with the regulated output taken off 2S lipos, does the external battery have to match the Rx voltage output since they will be sharing the same negative lead to complete the circuit for the data signal?  Or will the two systems work independently, allowing a simple 4 cell nicad to power the retract while sharing the negative lead with whatever output the rx has?
Hi Harry. Using a separate battery is quite simple. The retract battery provides the power only to the retract system not to the Rx. The Rx supplies a negative and signal. I don't know for sure whether the retract battery need to be the same as Rx battery, and the answer could be system dependant. It may work with one and not another. The reason for this is that the signal as you know is a series of pulses. The pulse voltage needs to be over a certain threshold level, so it is possible that you end up with a pulse that the decoder see as indeteminate.  However, you can suck it and see. It will either work or not and should do no harm.  Personally I have only used matched battery voltages.
So far as dirt on the leadscrews is concerned, so far this has been no problem on the Spitfire. On the Lado retracts the whole system is enclosed so I don't see that dirt can enter easily.

Offline JohnMac

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Re: Mick Reeves Lightning build
« Reply #90 on: September 27, 2010, 22:55:40 PM »
Hi Harry,
Try this link: www.gz-retracts.com. These guys partner Behotec so far as I can see. The alsoo make linear electric drives, brakes controllers etc. BTW, how is you German? Babblefish translation from German to English is only recomended after abou the 3rd pint of beer, at which point it becmes hilarious. Without the beer It is impenatrable.
There where these guys as well but there is not much on the site: www.electron-retracts.com
Regards,

John

Offline Pat Barnes

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Re: Mick Reeves Lightning build
« Reply #91 on: October 04, 2010, 20:27:38 PM »
I like the look of those GZ retracts. If they are typical German quality, they look very promising!

Offline HarryC

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Re: Mick Reeves Lightning build
« Reply #92 on: October 12, 2010, 10:06:58 AM »
The flap construction is pictured below

The only pre cut parts are the riblets, the top and bottom sheet are cut from planks of 1/8" balsa using the plan as a reference.  It's nice to go back to the basics after so many moulded models!  The hinging is by piano wire in brass tubes.  4 brass tubes are supplied and in total there is plenty of length but none is long enough for the flap so I joined two sections with a short piece of the next size up of tube from my own stock.  Other sections of brass tube are glued into holes in the wing ribs at either end.  The piano wire is then passed through the whole affair from the root rib end.

With the flaps made and the ailerons carved to rough shape, the top sheeting can be finished off again to rough shape.  The flaps are not hinged off the false trailing edge but from well behind it so the sheeting doesn't simply stop at the false t/e but hangs out some distance behind.  The easiest way to do it is to sheet well beyond the false t/e and well beyond the ribs at the tip end and round the inner tip corner, then offer up the flaps and ailerons and mark their positions onto the sheeting and cut off the overhang.

I have been looking at the fuselage again, as the wings are close to the point where no more work can be done until they are fettled to the fuselage mounting points.  I have cut out part of the cockpit area using a diamond wheel so I can get good access to the front section.  The next tasks are to glue in the nose bullet and then the two front formers with the nose retract system.  To get that all aligned correctly the first thing I will do is cut out the noseleg doors.  These, along with many other panel lines and fasteners are actually moulded into the surface of the fuselage.  From a short distance the fuselage looks smooth but it does actually have quite a lot of fine detail in it.  This would survive a fine spray of primer and humbrol silver, but anything more or any sanding, will destroy it.  However at the moment it gives me a guide as to where to cut the doors, I am checking that the leg and wheels will actually fit, before I cut it.  I am also considering applying a light carbon fibre bandage to the area before cutting, to help it and the doors hold their shape when cut and any stresses become released.  It will depend on me being able to get thin enough c/f cloth, it doesn't need the usual very heavy thick cloth.

Looking at the wing mounting, I am thinking about what can be done there. The design is that the wing tube is bolted at its inner end to a ply plate, and the tube then passes through a hole cut into the fuselage side and this takes most of the flight and weight loads.  The area of the hole has been reinforced at manufacture by a very thin layer of unidirectional (i.e not woven at 90 degrees) carbon fibre mat.  I would never expect this to hold the flight loads for any length of time, not sure I would even taxi around with it, and I know many people have re-designed this aspect.  At the very least I think gluing a short tube to the fuselage for the wing tube to pass through, would be a great help, as the load of the fuselage weight will then be spread by that extra tube all around the hole, rather than taken on the tiny top edge in contact with the wing tube.  Perhaps plywood butresses to the tube/fuselage joint as well?  Another possibility is to make an entirely new ply plate that tubes bolt to, which extends all the way out to the fuselage holes, with an outer tube all the way, so that ply plate will take some of the bending loads off the fuselage.
« Last Edit: October 12, 2010, 10:15:07 AM by Mpx »

Offline STORM

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Re: Mick Reeves Lightning build
« Reply #93 on: October 12, 2010, 10:38:13 AM »
Hi Harry.
Regarding the wingfitting, it sounds as though it's exactly the same system employed on the Javelin.
My model has had many flights over time and shows no signs of even whittling away at the fuse root holes.
I suspect this is because when all is clamped the very fact that the wing root rib is such a good fit with the fuse nothing seems to move, strange but true.
I understand your concerns and if you are worried then a piece of carbon mat glued inside the holes would give you peace of mind.
In other words Mick's system works better than you would expect, no need to over engineer the wing tubes at all in my humble opinion,
Regards,
Gary.

Offline Alan Smithie

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Re: Mick Reeves Lightning build
« Reply #94 on: October 12, 2010, 10:47:08 AM »
there is plenty of length but none is long enough for the flap so I joined two sections with a short piece of the next size up of tube from my own stock.

I'm mopved to ask why - the tube is only a bearing bush and so won't be taking any bending or tensile loads. In fact you could probably get away with short pieces at each rib station if you were confident that they would maintain alignment for final assembly.

£0.03 supplied,

PDR
There are no shortcuts on the long, hard road to success. But if your dad's rich there could a limo service...

Offline HarryC

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Re: Mick Reeves Lightning build
« Reply #95 on: October 12, 2010, 10:49:13 AM »
the very fact that the wing root rib is such a good fit with the fuse
ha ha, not on the Lightning!  The root rib follows an S curve, the fuselage is flat.  Yeah, I think an extra layer of c/f and a short guide tube to spread the load all around the hole rather than just the top edge, should be fine for peace of mind.

Offline HarryC

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Re: Mick Reeves Lightning build
« Reply #96 on: October 12, 2010, 10:53:15 AM »
I'm mopved to ask why - the tube is only a bearing bush and so won't be taking any bending or tensile loads. In fact you could probably get away with short pieces at each rib station if you were confident that they would maintain alignment for final assembly.
I did think about that at the time, in fact it doesn't even need them at every rib just at the root and tip ribs but decided that when I come to install it and push the piano wire through, it only needs to misalign a tiny fraction at any one section of tube/hole in rib and it will be a pain trying to get the hinge wire all the way through.  Since there is more than enough brass pipe supplied, and the weight penalty is in grammes, having a contimuous bearing tube along the entire flap seemed the best idea.

Offline boeing247

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Re: Mick Reeves Lightning build
« Reply #97 on: October 27, 2010, 19:49:39 PM »
Hi Harry,
On the previous page you mentioned using a button air valve to control the doors.
What I've done is to control the valve from the servo and not rely on the struts to trigger it. By using an "overcenter" linkage from the servo to the retract valve, you can use the servo slow feature on the transmitter to slow the  retract servo so the gear has enough time to retract fully, then a cam cutout on the servo wheel will trip the valve. This system also has the advantage of not putting any loads on the gear strut or the servo.
You have to play around with the cam profile and timing, but once set up, it works great.
Jon

Offline HarryC

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Re: Mick Reeves Lightning build
« Reply #98 on: November 06, 2010, 11:44:54 AM »
I have been doing work on the wings which involves a lot of fitting flaps and ailerons, checking the fit, removing them, sanding and filling them and the wing sheeting, putting the parts back on and repeating several times.  From above I now have what look like Lightning wings, the underside is still not sheeted as that has to wait for other work.

The front intake bullet with the detachable nose cone is now glued into place and gives it the unmistakeable Lightning look

Behind that go the two formers carrying the noseleg mounting plate.  Although the hysol mixing nozzles are somewhat wasteful of this expensive glue, they are invaluable for this sort of situation for putting a bead of glue along both sides of the former to fuz joint, and then smoothing down with a gloved finger.

The fit of the formers to the fuz is poor vertically but that allowed wiggle room to get the noseleg plate to a suitable angle so that the wheel is just inside the fuz when it is retracted - the front former is as high as it can go in the fuz with a large gap at the bottom, and the rear former is as low as it will sit with a large gap at the top.  If both formers are pushed to the bottom or top then the wheel sits partially outside the fuz when retracted.


Offline STORM

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Re: Mick Reeves Lightning build
« Reply #99 on: November 06, 2010, 13:21:06 PM »
Starting to come together!

Offline marcs

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Re: Mick Reeves Lightning build
« Reply #100 on: November 12, 2010, 09:28:44 AM »
Harry,

Hi, just subscribed and great subject matter. I usually spend most of my time posting builds on RCU but time to broaden my scope!
I also use alot of Hysol in builds, never use those nozzles though, big waste. I buy 10ml and 5ml syringes from a medical supplier, the unit cost is very small, then if you need to extend the 'tip' to reach into difficult places I push a small piece of silicone fuel tube (IC model bore stuff) over the syringe end, take a cotton bud (Boots ones with plastic shafts - again very cheap) cut the buds of each end and you have a tube which you can cut to length to push into the other end of the silicone tube to get an application nozzle, you can even cut the tip at 45 degrees to give a good application.

It sounds a faf but if you cut up a 1m length of fuel tube into 2cm lengths and do the same with some cotton buds it takes seconds to make a nozzle. I mix the Hysol in small plastic cups first, again you can get these from a medical supplier.

marcs
GBRJET

Offline HarryC

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Re: Mick Reeves Lightning build
« Reply #101 on: November 12, 2010, 10:22:46 AM »
That's brilliant marc, thanks for that.  I have just one nozzle left and was pondering about getting more but I hate the waste of glue that they entail.  I already have box loads of syringes as I work in the medical world and sometimes they have to throw out time expired stuff (sterility guarantee runs out) so I shall be making nozzles tonight.  I mix my glues and fillers on post-it pads, medical reps give them out by the shed load.

Offline lozza

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Re: Mick Reeves Lightning build
« Reply #102 on: November 12, 2010, 10:59:46 AM »
Harry,

Hi, just subscribed and great subject matter. I usually spend most of my time posting builds on RCU but time to broaden my scope!
I also use alot of Hysol in builds, never use those nozzles though, big waste. I buy 10ml and 5ml syringes from a medical supplier, the unit cost is very small, then if you need to extend the 'tip' to reach into difficult places I push a small piece of silicone fuel tube (IC model bore stuff) over the syringe end, take a cotton bud (Boots ones with plastic shafts - again very cheap) cut the buds of each end and you have a tube which you can cut to length to push into the other end of the silicone tube to get an application nozzle, you can even cut the tip at 45 degrees to give a good application.

It sounds a faf but if you cut up a 1m length of fuel tube into 2cm lengths and do the same with some cotton buds it takes seconds to make a nozzle. I mix the Hysol in small plastic cups first, again you can get these from a medical supplier.

marcs
GBRJET

Now i like that allot

lozza

Offline marcs

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Re: Mick Reeves Lightning build
« Reply #103 on: November 12, 2010, 11:42:57 AM »
Lozza, cheers - have to say your pics are the best  ;)
Another use of cotton buds is for cyano applicators - info on my website.

marcs

Offline HarryC

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Re: Mick Reeves Lightning build
« Reply #104 on: November 23, 2010, 21:01:01 PM »
Here's a sight for Lightning lovers, the shape is coming together

The two formers that the wing tubes bolt to have been glued in with hysol beads around them, thanks to marcs's tip it was done quickly and consistently with a syringe to apply a good bead, then put on a latex glove and run a finger along the bead to make a a good concave bead with max area on the fuz and former.

While that hysol cures, move on to make a start on the tailplane mounting on the rear fuselage.  This piece comes ready assembled
The tailplane rods are a solid aluminium rod in a brass tube which is held down by copper straps.  There is an M3 threaded hole in the outer part to which the tailplane is bolted, the inner part has an M4 hole with a custom made brass fitting as a control arm.  The control arm passes through a slot in the plywood which acts as a sideways motion limiter, but it is quite a bit wider than the control arm so I will probably line it with thin plasticard once everything esle is in place, to prevent any sideways movement of the tailplanes.

The control arm bothers me a bit, see photo below.  It is a brass M4 bolt with a ball head, and aluminium spacers to keep it the correct arm length from the torque rod.  The pushrod attachment to the ball is one of those open circle links that just pops onto the ball, which to my mind could also pop off under stress or vibration.
I would far rather use a ball that bolts through so the bolt head/washer prevents the pushrod connection from coming off, but the ones I have are for M3 bolts.  Do you get M4 bolt through ball links?  I can't see a way of making something to work, I don't have a lathe or special metal working abilities to make anything.  Does anyone have any ideas?

Offline selleri

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Re: Mick Reeves Lightning build
« Reply #105 on: November 23, 2010, 22:39:59 PM »
Phil at Fighteraces sourced some heavy duty ball links he used for Ali's Skyraider, worth checking with him.

You could also try hobbystores that carry spare parts for cars IIRC I've seen 4mm ball links in that capacity.
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Offline Thorjet

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Re: Mick Reeves Lightning build
« Reply #106 on: November 23, 2010, 22:41:09 PM »
Looking good Harry

Offline Alan Smithie

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Re: Mick Reeves Lightning build
« Reply #107 on: November 23, 2010, 22:56:10 PM »
The control arm bothers me a bit

Is that all that bothers you? Personally I'd be more concerned abour the use of copper plumbing straps (at least that's what they look like to me) to restraing the tailplanes of a fast jet. Copper isn't exactly reknowned for its resistance to cracking under cyclic loads, and it age hardens to make it even worse. I'd be looking to find a better solution to this area before worrying about the ball links!

PDR
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Offline Norfolk'n'Good

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Re: Mick Reeves Lightning build
« Reply #108 on: November 23, 2010, 23:05:31 PM »
Is that all that bothers you? Personally I'd be more concerned abour the use of copper plumbing straps (at least that's what they look like to me) to restraing the tailplanes of a fast jet. Copper isn't exactly reknowned for its resistance to cracking under cyclic loads, and it age hardens to make it even worse. I'd be looking to find a better solution to this area before worrying about the ball links!

PDR


I have to agree that stuck out like a sore thumb to me although I may have mentioned it in a slightly alternate manner  ;)

Offline HarryC

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Re: Mick Reeves Lightning build
« Reply #109 on: November 24, 2010, 09:56:16 AM »
Thats easily dealt with.
Back to the ball link, am I being too worried?  I would not be keen on using that ball link on a .40 glow model let alone a large jet, but is there any data to support that?

Offline Davie Matthews

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Re: Mick Reeves Lightning build
« Reply #110 on: November 25, 2010, 18:59:07 PM »
Thats easily dealt with.
Back to the ball link, am I being too worried?  I would not be keen on using that ball link on a .40 glow model let alone a large jet, but is there any data to support that?

Well Harry,  If you have doubts in your own gut.  LISTEN to it.  I think you answered it in your post above. 

Nice work so far.  Best of luck with her.

Davie
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Offline HarryC

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Re: Mick Reeves Lightning build
« Reply #111 on: November 25, 2010, 19:41:37 PM »
I think I have an excellent solution, parts now on order from a tractor spares company of all things!  Will do photos when I have the parts and made the alternative control rod.

Offline nmacwarbirds

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Re: Mick Reeves Lightning build
« Reply #112 on: November 26, 2010, 14:14:17 PM »
Dear Harry
Looking on with interest, I take it you will be using phenolic tube
to support the wing tubes where they enter the fuselage and protrude through to a fore and aft former?

I hope that makes sense.

Regards Phil G.
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Offline HarryC

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Re: Mick Reeves Lightning build
« Reply #113 on: November 26, 2010, 17:45:20 PM »
Looking on with interest, I take it you will be using phenolic tube
to support the wing tubes where they enter the fuselage and protrude through to a fore and aft former?
Going to make my own tubes, as can't guarantee getting a good size match of phenolic tube by mail order other than from MR and I don't want to buy and pay postage on tubes many times longer than I need.

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Re: Mick Reeves Lightning build
« Reply #114 on: November 27, 2010, 09:07:20 AM »
I definitely think you are going the right way with the build Harry :af can't beat the old gut instinct as Davie puts it, the belt and braces attitude is better, and as you say, the parts are out there, you just need to look further modelling suppliers :af
"Jet flying is strictly on a shoestring"

Offline HarryC

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Re: Mick Reeves Lightning build
« Reply #115 on: December 22, 2010, 09:26:20 AM »
It's gone very quiet in this thread.....!
There has been a break whilst I assemble a float plane Beaver, a leccy one at that.  Shock horror, Harry flies things other than jets!  Also been waiting for some parts to arrive and having a major ponder over the tailplane system.

The Weatronic 12-22 Rx with 2 built in gyros has arrived so I have started programming up the Tx and Rx so that I can test different tailplane systems, and to check the operation of the gyros.  The Rx has to be built into the model in a particular orientation so that the gyros align with the required axes.  I have been getting them working and watching the servos react as I move the Rx.  Before now I would have said the Rx had a faulty connection if servos twitched when I moved the Rx!

Why gyros and why 2 of them, and why built in rather than external?  Highly swept models such as Lightning can wobble from side to side in roll and it looks poor, a gyro will stop that, so it is for cosmetic reasons.  The Weatronic rx has a choice of 2 or 3 but not of 1 gyro, and the 2 gyro rx costs £70 more than the normal rx, which is much cheaper than a single ACT Fuzzy Pro gyro so it makes sense to get the 2 gyro Rx.  But isn't the Fuzzy Pro very good, and much easier to mount its small sensor the correct way than mount the huge 12-22 rx the right way in a constricted space?  True, and I do have a Fuzzy Pro for the Lightning but I trialled it in my Typhoon which can rock noticeably, and it made such an improvement it is staying in the Typhoon.  With 2 gyros I can use one on ailerons, and if needs be one on the nosewheel steering and on the rudder.  Being built in and controlled by software, the same gyro can be independently assigned and managed for many different servos, so the one gyro can be assigned to steering and rudder but have independent gain on each, so it can do the job of two external gyros.  Only "rate" mode is available, they haven't got HH mode yet but it's rate mode that I want, and like many external gyros a Tx channel can be used to control the gain, even the gain curve has 5 points which can be adjusted in software.  So for example, on test flights I can take off with aileron and rudder gain at zero, and use the two sliders on the Tx to alter the gain as required for each of them independently.

Offline HarryC

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Re: Mick Reeves Lightning build
« Reply #116 on: December 22, 2010, 14:04:44 PM »
My plan to replace the brass ball-link with an M4 high-tensile bolt and M4 steel clevis with ball link is going well, and forms a very strong, bolted, slop free linkage at the tailplane horn end of the system.  The remaining problem is at the servo end.  One servo is mounted 1/4" higher than the other because the pushrods cross each other and however you try it, the clevis meets the servo arm at quite an angle, which doesn't work, clevises need to be parallel to the plane of the servo arm/disc.  Plan "A" was to get the servo arms that incorporate a ball link from fighteraces, I did and they are gorgeous, but the smallest size that has an M3 link is just a bit too big, the arms of the two servos clash into one another at up elevator.  Plan "B" Was to cut the ply plate to move the servos much further back and away but the different planes between the tailplane horn and the existing servo cut outs puts the servos even further out of kilter with the horns.  Plan "C" was to get metal servo discs and fit ball links at the servo end of the pushrod (metal because plastic servo arms with pushrod attached by ball link above or below the arm can cause the arm to twist and lose some motion and I guess eventually weaken it) but I think I am dropping that in favour of Plan "D" which has just occurred to me, which is to completely re-mount the servos on their sides so that the servo arm is in the same plane as the horn and in line wih it too, and maybe then be able to use the fighteraces servo arms too.  This will probably require me to cut a completely new 1/4" ply tailplane mount.

Offline rcfanuk

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Re: Mick Reeves Lightning build
« Reply #117 on: December 22, 2010, 15:22:36 PM »
Harry, plan D sounds the best option, you will be able to keep the servo geometry's the same.  :af

Good to see you back on this build

Steve
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Offline HarryC

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Re: Mick Reeves Lightning build
« Reply #118 on: December 23, 2010, 09:41:40 AM »
I did some trial fits last night but there is not space to mount the two servos on their side where they need to be in order to line up with the torque rod horns, so they must remain upright (actually it is inverted when the whole assembly is fitted into the fuz)

This shows the first problem, that of the angle that the pushrod arrives at the raised servo, using the pre-installed pushrods.
The clevis is clearly not going to work connected to the servo arm at that angle.  One servo is raised because the pushrods cross one another.  The other servo is not fitted at the moment, the camera view is pointing from the missing servo to the other torque rod horn.  Can you see the other horn?  No!  So the other pushrod has to pass through the servo that you can see, which will take a bit of magic.  Solution?  Use longer horns on the torque rod, that will raise the pushrod above the servo, and on the one that you can see will bring it in line with the servo arm.  But to compensate for the travel required, longer servo arms are needed which starts to bring the rods and servo bodies back into conflict.


The above photo and this photo show my concern about the ball link
I just donít feel that is meaty enough or secure enough to drive these large tailplanes in a fast model.  It would not be easy but it is conceivable that the plastic fitting could be popped off the ball.  I want something that doesnít have the option of coming apart.

This is my solution
On the left is the original brass M4 rod and ball top with its aluminium spacers and plastic coupler for M3 pushrod.  It was only long enough to screw half way down into the torque rod. I will replace the brass bolt/ball with an M4 high tensile bolt from the other side so it passes all the way through the torque rod and is locked into place.  Onto the bolt goes the fitting on the right.  This starts off as the M4 steel clevis shown in the middle.  Clevises are available in many sizes, the snag is that the pin matches the thread, so an M4 thread gets a 4mm pin which means 4mm holes through the arms.  Ball links have 2 or 3mm holes.  I was able to get this M4 clevis as normal arms or long arms so I got the long arm, cut off the bit with the hole and am still left with enough arm to make a 3mm hole and fit the ball link.  I had intended to drill a 3mm hole but unless the drills and bolts and my machining are really precise, there will be some slop in the fit of the the bolt passing through the clevis, so instead I drilled smaller and tapped the clevis arms for M3.  So a short M3 bolt screws through the clevis, firmly holding the ball link, finger tight means the threads nip up in the clevis arms so the bolt has zero slop in the clevis and the nut adds a final bit of security to keep the bolt in place.

Since the clevis arrangement screws down onto the bolt coming out from the torque rod, I can easily adjust the length of the arm to suit all the pushrod clearances and angles required.  Using the 17mm Futaba arms on the servo just manages to give the tailplane travel shown in the plans.
« Last Edit: December 23, 2010, 09:52:51 AM by Mpx »

Offline slippery

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Re: Mick Reeves Lightning build
« Reply #119 on: December 23, 2010, 10:28:26 AM »
Just a thought maybe use an aluminiun output arm bent to a suitable angle for the clevis to locate at a better angle.


 

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