Martin McIntosh
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Posts posted by Martin McIntosh
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Problem solved thanks, neither of us recognised it.
Its huge weight (2lb 2oz) would make it ideal for a warbird.
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A clubmate gave me an engine to look at and if possible run. He bought it as part of a job lot. It says 91 on the rocker cover, Hi-Max and made in England on the side and has an Irvine carb, the crankcase being die cast and has a very thick backplate/mount. The exhaust stub looks similar to SC (Just Engines?) and it has rear pushrods. Trouble getting photos from my cameras at the moment but will try. Any ideas please since it is new to me?
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Glad that someone else has observed this Andy, it could well be the cause of many issues.
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That reminds me of a problem I came across concerning the Rx signal wire voltage level. I bought some more of the HK MCA series retracts but when connected to any Orange Rx they did not work, earlier ones having been fine, but were OK on JR/Spektrum.
I checked the signal levels on a `scope and JR`s were at 5V but Orange only 3V which was now not enough. The retract amps must have had a component change for some reason. I do not have any Futaba gear so cannot comment on it but there may be a similar problem with that and some servos.
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M.H.,
Strangely not JR in this case. They are HiTec 82 mg`s. Never had any problems with them in the past on other models.
I also use a lot of Corona 939`s both analogue and digi. Due to availability at the time my Super Aeromaster wings have two each of normal digi and HV. The speed is the same in each case on 6.6V so I think that the HV ones are just regulated down.
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Happened to one of my models more than once, with electric power to start with, overvoltage from the BEC being the cause. When the voltage stabilised after a minute or two it was OK.
Changed to i/c power but retained a UBEC to stabilise the 6.6V from the LiFe pack and the problem returned. Lowering the UBEC output from 5.5 to 5V did the trick. Some servos do not like even a tad over 5V.
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I fear that yours is going to gain a lot of weight if you mean to sheet the whole wing in 1/8th, double the weight of the skin shown on the plan and there will be an awful lot of it.
That massive front tube will certainly not need ply either side of the ribs. One piece at the centre and outer followed by 1/8th balsa on one side only for the rest since the loading will be quite low. The inner ribs against the fus. take most of it.
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What do you intend to sheet the wing with? I seem to remember that the plan states 1/16th (original electric version) but it needs 3/32nd otherwise your fingers will keep going through. I once met a guy who did his in 1/16th then regretted it.
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No soldering involved. The shells can have the crimped connectors pushed back in.
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Depending on how long the servo leads are that could end up with very long wiring unnecessarily and reduce the voltage so not a great idea. If the ribs are deep enough then just make large holes in them, tie a small weight to some thread and rattle it through for a draw cord. If the ribs are shallow then simply remove the plug shell from the wires then pull them through. A `dog leg` round wheel wells may require pre wiring.
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I have not used clevises for many years now, just mini ball links to get round that problem amongst others such as overly tight fits. The Aeromaster wings are quite thin so standard servos would protrude a fair bit. Very much simpler to fit thin wing ones, a simple mount with three screws. No need to add weight by fitting covers.
Taped and glued may be OK on foamies but that thing is going to be quick and heavy so that is a no no.
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I have a Super Aeromaster and use 4 Corona DMG aileron servos, simple to fit but I did once get a couple of duff ones out of the many in use. If you are prepared to spend a little more on, say, metal cased ones then you would do well to go down that route.
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CA by itself does not stick to carbon and easily scrapes off. I do use it on rods at times but firstly spray all parts with Polyolefin Primer (from CPC). This allows you to glue almost anything to anything else, even polythene fuel tanks. So called 2mm rods can have a shallow thread put on which aids adhesion. JB Weld works quite well.
That is a large motor and will cause much vibration; similarly the model will be large and will require rather more robust rods than you would put on a trainer. The suggestion above to use 5x3 tube with a 3mm threaded rod inside is bullet proof and simple so in your case I would recommend that.
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Rather than using the Tx differential function I start by setting all four servo arms forward to give mechanical diff. as you should do. Each can then be tweaked as needed,
2:1 diff. is a good starting point.
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Those detailed pics from Cymaz show the tail to be at a +ve incidence. Unfortunately mine was built from an original Precedent kit with the 1/4sq. spruce longerons level all the way to the fin post, resulting in the tail being at 0 deg. This meant that it will only fly with a huge amount of down elevator, although that does not detract from the performance, just looks weird on the ground. Because there is 1/16th ply from the fin through the tail it was not possible to correct this.
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A classic aero on electric power? Sheer sacrilege. Go to the naughty step.
Tried my 48" Dalotel on it once and despite more power it flew like a pig compared with an OS 25 FX in it. I have tried this swap on several other models including The Ohmen and a Limbo dancer with the same result, just don`t ask me why but they seem to get rather reluctant to change heading, possibly due to the gyroscopic effect of the fast spinning outer rotor.
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Since you are fitting ailerons I would suggest coupled ail/rud with about a 30-50% mix. This makes turning much easier. I make this switchable with either the mix sw. or mixed on low rate rudder only so that full throw is available for stall turns.
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I did the same quite a few years ago using the plan from a Mercury kit. Had to guess at some of the formers which were not shown.
Originally fitted a Mills but the comp. screw was rather inaccessible and insisted on unscrewing in flight, resulting in `engine still running` landings; it was tricky to start being inverted. Eventually electrified it (sorry). With a 3s 1000 and a tiny Orange caseless Rx + esc there was very little room left inside.
Yours is obviously rud/ele which will be fine because they refuse to turn with ailerons alone. With all that wing area you need not worry about a little extra weight.
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Glad to hear that you sorted it. Once one of these is set there should never be a need to touch it again (on the same fuel).
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I used these successfully some years ago then later obtained a box full of them in various states. They must have been made in different bike sheds because although they all came from 60`s the parts like sliders were not all the same thickness. Once the spraybar has been removed it is very difficult to re assemble in the right place. I thought I knew the things quite well but gave up trying to get one to work properly on an identical motor to that used previously.
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I was about to suggest a 4-Max battery but was beaten to it, they really are a better option to the ones you are using.
I have a Hawk, 90mm 12s fan, as yet unflown and despite some mods the static thrust is very disappointing indeed.
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Thanks Phil but the channels on the Interlink DX are totally different to a normal Tx and the ones quoted for rates are correct. When I edit it they are set correctly and `saved as` for that model, but despite that they end up on the default elevator rate switch controlling all three at once.
When I buddy up a JR Tx I can do what I wish but it would mean a different memory for every model.
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Thanks for that info.
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From what I remember of mine and from the results of testing I would say that the motor position as shown on the plan was pushing the nose down. I have a HK FPV powered glider which is similar and the thrust line is considerably up at the rear.
Nijhuis Lancaster 1/9 scale
in Build Blogs and Kit Reviews
Posted
If you arrange the o/p arm to be in line with the servo body there will be zero force on it when the lights are deployed. I always set up flaps like that, having learned by burning out four retract servos on the bomb doors on my version of the model.