Martin Whybrow Posted December 1, 2013 Share Posted December 1, 2013 Wouldn't it have been easier to use a 9 way and wire up the 5 signal lines, 2 positive lines and 2 negative lines and common all the servos pos and neg lines? That's certainly how I would do it. Quote Link to comment Share on other sites More sharing options...
Biggles' Elder Brother - Moderator Posted December 2, 2013 Author Share Posted December 2, 2013 Well Martin, its funny you should say that, I did actually consider doing exactly that, but rejected it for three reasons: Complexity: I felt it would unecessarily add to the complexity of the wiring. I would have to ensure that there was a different +ve and -ve feed to each aileron for example to alleviate the risk of loosing both ailerons from a single connection break. More telling, I would have to make up additional connections, either inside the socket or externally, to distribute the +ve and -ve feeds. These additional connections seemed to me to remove any advantage of fewer connections to pins - ie I'd have to make them anyway. At least this way they are all in one place! Overall I felt that this added complexity nullified any advantage of smaller connector and introduced new possibilities for failure. Redundancy: the nine pin solution effectively puts all your eggs in just two baskets - everything swings on those two +ve and -ve connections. If you lose one of them you lose not one servo - but possibly three of the five. I could assist this by double ganging the +ve and -ve feeds - ie every servo is connected to both. But then I just get back to point 1 - even more complexity and complexity breeds the potential for failure was my feeling! Current Handling: this was the clincher for me. These D-connectors are really designed to handle small currents - 2amps is the specified maximum. Now for standard servo operation that's no problem. But, we have to at least consider the possibility of non-standard events. These bomb release mechanisms from SLEC are very cute - but they are hardly precision engineering. In reality the servo momentarily stalls at the end of the travel. It's also quite within the bounds of possibility that the mechanism could jam. And who hasn't ever had a retract mechanism jam at some time? Its happened to us all - right? What if the two happened together on the same power feed? We could end up pulling an awful lot of current through a single pin of this D-connector. These pins are gold plated - but as I say they are not designed to carry high currents. So, while 1 and 2 are marginal and 3 is maybe not very likely, I decided that all of them taken together constituted enough of an increased risk that the relatively small benefit of using a 9-way instead of a 15-way didn't seem justifiable to me. In the way I've done it every channel of every servo wire has its own pin and its own joint and all the joints are together where I can get at them if they do need maintenance. Of course its "horses for courses" and there is no "right" answer where this is concerned - each man to his own as they say and every builder must decide for himself where his particular balance of risk lies. BEB Quote Link to comment Share on other sites More sharing options...
Biggles' Elder Brother - Moderator Posted December 2, 2013 Author Share Posted December 2, 2013 Hi Danny, not quite sure quite what you mean by "align" - but I'm assuming you mean how are the servo leads distributed around the pins? If so then each servo is allocated a "column" of three pins across the depth of the connector with -ve and signal alternating along the connector. Just read that - its as clear as mud isn't it! I think a diagram would help - I'll put one together and post it tomorrow - bit late now! Thanks for the heads up on the photos. Along with the ones Monique has given me they should provide a very valuable source of information. BEB Quote Link to comment Share on other sites More sharing options...
Vecchio Austriaco Posted December 2, 2013 Share Posted December 2, 2013 About redundancy and current handling: As you have done it a failure will only affect one servo / retract or whatever consuming device you connect. Would have been better to use the "common" system, but to use several pins for plus and minus. Just an idea. What is more interesting is how you will fix the connectors together. Normally they can be locked by using a screw - but you fixed the female connector to the wing by screws -- so you cannot use the holes for a locking screw. If - as the devil never sleeps - and possibly because of vibrations - the connector comes apart you will be in huge trouble as you are loosing all servos in the wing. So I would rather replace the screws by bolts and nuts - leaving the bolts long enough to allow locking the male connector to the female one. VA Quote Link to comment Share on other sites More sharing options...
Martyn K Posted December 2, 2013 Share Posted December 2, 2013 Hi BEB I am inclined to agree with VA on this. These connectors NEED to be screw locked. They will come adrift with very little effort. Splendid and informative build though Martyn P.s. Some nice sharp photos as well Edited By Martyn K on 02/12/2013 11:03:49 Quote Link to comment Share on other sites More sharing options...
Biggles' Elder Brother - Moderator Posted December 2, 2013 Author Share Posted December 2, 2013 Hi Guys, Thanks for the comments. I totally agree about bolts - these do need to be screwed together. Those things that look like screws holding the connector body in are in fact 3mm bolts with nuts on the other end. They are in that way round just because it was simplier at the time - when the plug arrives (when I solder it up, after I have recovered and am detraumatised from doing the socket! ) I will reverse them and we will then have a screw together connector. On the point of ganging VA - you are of course right - the absolutely optimum arrangement would be to use 15 pins with 5 ganged +ves and 5 ganged -ves. That way if I lost a single connection then - provided it was not a signal connection - all servos would still work. (The way I've done it if I lose one connection I lose one servo - whichever connection goes). So why didn't I do that? Well the simple truth is I don't belive my "miniature" soldering is up to it mate! The way I've done it took me over two hours and much cursing! It leaves me with a situation in which if I lose one connection I would still be able to land the model safely - whatever connection it was and that will have to be enough for me! Unless you want to volunteer to solder the connector,.... OK the pin-out I've used on the connector as promised last night: Why did I alternate the leads instead of putting all the signals along one row? It looked prettier! Seriously, given that I am not ganging the supply, I think it just makes it a little bit easier to wire trace than if all the same colours go to adjacent pins. BEB Quote Link to comment Share on other sites More sharing options...
Vecchio Austriaco Posted December 2, 2013 Share Posted December 2, 2013 Volunteer - I have a good excuse as I have packed up my soldering equipment for my never - ending removal story and I think the best thing is to buy a decent magnifying lens for the soldering job looks all very nice, and I look forward to see this plane in the air! VA Quote Link to comment Share on other sites More sharing options...
Steve Hargreaves - Moderator Posted December 2, 2013 Share Posted December 2, 2013 Posted by Biggles' Elder Brother - Moderator on 02/12/2013 11:50:16: Hi Guys, Thanks for the comments. I totally agree about bolts - these do need to be screwed together. Those things that look like screws holding the connector body in are in fact 3mm bolts with nuts on the other end. They are in that way round just because it was simplier at the time - when the plug arrives (when I solder it up, after I have recovered and am detraumatised from doing the socket! ) I will reverse them and we will then have a screw together connector. Is the way forward to fit captive M3 Tee nuts on the other side of the plywood mounting plate so you can join the two D connectors then bolt through them both, through the ply plate & thread them into the captive nuts?? Great soldering by the way....most impressive......doing a similar job on a 9 way D-sub drove me to distraction... Being a bad workman I blamed my soldering iron..... What did depress me was how hard I found it to see the pins & wire.....& I'm not THAT old..... Quote Link to comment Share on other sites More sharing options...
Danny Fenton Posted December 2, 2013 Share Posted December 2, 2013 Hi BEB, sorry mate didn't explain myself very well. The D connectors have to obviously line up when you fit the wing, I was guessing that one would be fixed solidly, then the other half losely attached until the wing was fitted and then somehow locked in position. I think I saw Matt use epoxy to lock his D connector in place on his Vixen? I have also seen one fixed solidly and the other connector fitted so that it can slide up/down/side to side to allign as the wing is fitted. I don't see why you would need to bolt through them if they are secure, the wing bolts will hold it all in contact? Cheers Danny Quote Link to comment Share on other sites More sharing options...
Biggles' Elder Brother - Moderator Posted December 3, 2013 Author Share Posted December 3, 2013 Hi Danny, ah, I understand. I hadn't intended it to be a "plug in" system like that. My intention is to have the plug on an umbilical cable in the fuselage - hence why I do need the screws, because the plug could disconnect if only friction is holding it in. So I'll run the servo leads from the Rx, via some sort of strain relief (probably a couple of simple cable ties to the aircraft structure) form them into a cable in a heat shrink sleeve, then run that to the plug. But now you mention "locating" it in a sliding mount and using the wing fixing - mmmm, new possibilities and food for thought! BEB Quote Link to comment Share on other sites More sharing options...
Matt Jones Posted December 6, 2013 Share Posted December 6, 2013 Just to add to the discussion on using D-sub connectors, I've been using them for years and never screwed them together. They're such a tight fir I'm not worried about them coming adrift. One caveat though, this is on gliders. No idea how the vibrations of i.c. / electric would affect things. Quote Link to comment Share on other sites More sharing options...
Biggles' Elder Brother - Moderator Posted December 20, 2013 Author Share Posted December 20, 2013 Part One: Well, first day of the Christmas Hols! Work has been busy so I've slipped behind, but I'm hoping to make a lot of progress over the next 2 weeks or so. I started this morning by girding my loins (can be painful if you don't have a proper girder!) and facing upto the fact that the partner plug for this D-connector was not going to solder itself. So, having mainly recovered from the trauma of doing the socket I embarked on the plug. Was it easier second time round? No! If anything this became even more of challenge. I just kept saying to myself "You'll really appreciate it down at the field when you don't have to plug all those separate servo leads in"! Anyway, here's the finished job,... Next up I pushed the two connectors together and rung then out with a multimeter to check all the joints and for an absence of any nasty shorts! So, having spent all morning on that, it was time to get out the crimping tool and install some connectors on the ends of these servo leads. Crimping servo connectors is not a difficult job - provided you have the right tools - but it is a bit fiddly and there is a "knack" to doing it. Everyone has a slightly different way of doing this I've noticed, for what its worth here's mine! Quote Link to comment Share on other sites More sharing options...
Biggles' Elder Brother - Moderator Posted December 20, 2013 Author Share Posted December 20, 2013 Part Two: First cut the wires to length - cut across all three together so as to get them all the same length. Then pull them apart - about 1/2 an inch or so is enough,... Next I strip the insulation off the ends. Don't strip too far back - you only need about 3-4mm of wire showing. Do use a proper wire stripper set to the correct spacing - don't do it with a scalpel! Take a connector now. Its important to understand the "anatomy" of these things if you are to use them correctly. There are two sets of lugs, one will clamp around the insulation (as a strain reliever) and the second will clamp around the bare wires or conductor. These are shown in the picture below,... Finally notice that there is a latching spring bit that will engage with the plastic body of the connector to hold the pin (in this case) in place. Every person I know does this next bit a different way - I think you just have to figure out what works for you; I place the stripped wire end in the connector so its lined up OK with the insulation over the back lugs and the stripped wire over the front lugs. Holding this in place with the forefinger and thumb of my left hand I then give the back lugs a very gentle squeeze with some long-nose pliers - just enough so they will hold the connector in place without it slipping off. Now I take the crimping tool, line it up so the front edge of the front lugs are flush with the side of the tool - then squeeze. And the result should look like these,... Note that the insulation lug is indeed around the insulation whilst the front lugs have been sort of "folded inward" onto the wire. This is how it should be. If the front lugs wrap around the wire you are using the crimping tool back to front! Once crimped give each connector a firm tug to be absolutely sure its "done" properly. Some people lightly hold the connector in the crimpling tool and then insert the wire - I've never been able to make that method work! But it obviously works for them. Some people solder the connectors on - but I've been told (can't remember who by!) that a good crimp is actually mechanically stronger and usually has a lower resistance than a solder joint! Next we insert the pins into the plastic housing - its important here that you insert them the right way up - with the locking spring facing up into the holes in the face of the plastic casing. If you get this wrong they will simply pull out again! Quote Link to comment Share on other sites More sharing options...
Biggles' Elder Brother - Moderator Posted December 20, 2013 Author Share Posted December 20, 2013 Part Three: Its easy to say "insert them into the plastic housing", in reality I find this the most difficult step - there isn't much clearance and the connector/wire can be a very tight fit and it needs to be shoved in quite a way - at least until you hear the latch clicking into place. Trying to "shove cooked spaghetti up a cat's bum" springs to mind! But they all go in eventually. Sometimes you need to "revisit" the insulation lug as this is often the tightest fit, a little extra squeeze with a some pliers usually sorts things. All that's left now is to slide on the protective shroud and et viola, one servo connector... All five from the socket were done first and then labelled up, giving us this,... PA - port aileron, PB - port bomb release, U/C - undercarriage, SB - starboard bomb release, SA - starboard aileron. Turning our attention to the plug which will be on an umbillical cable from the Rx in the fuselage, I labelled up the wires and slid over a length of heat shrink,... Then fitted the servo connectors (sockets this time but the basic process is the same, but no protective shroud is needed of course) and then fitted the hood onto the socket. And so we end up with this for the Rx side,... If you never made your own servo leads its certainly worth it. First, in the long run it is cheaper - you have the initial outlay for the crimping tool (about £10) but that will last a lifetime. But most important of course you have custom length servo leads and the satisfaction of knowing you did them yourself. The next job is to test all this by connecting it up and checking that all the wing servos work as they should. But that's a job for tomorrow - as I'm too cold now! BEB Quote Link to comment Share on other sites More sharing options...
Tony Bennett Posted December 20, 2013 Share Posted December 20, 2013 blinking do dads, that looks complicated. that must be one of the reasons i hate the fitting out stage. glad you are back on this one sir. i have missed it Quote Link to comment Share on other sites More sharing options...
Danny Fenton Posted December 20, 2013 Share Posted December 20, 2013 Never thought I would say this, nice pics Great explanation btwCheersDanny Quote Link to comment Share on other sites More sharing options...
Chuck Plains Posted December 20, 2013 Share Posted December 20, 2013 I'll have to have a word with my veterinary about the spaghetti issue. Quote Link to comment Share on other sites More sharing options...
Concorde Speedbird Posted December 20, 2013 Share Posted December 20, 2013 What is that grey thing? All seems quite complicated, I am just using Y-leads! CS Quote Link to comment Share on other sites More sharing options...
Bandit Posted December 20, 2013 Share Posted December 20, 2013 Sweet, one plug sorts the lot I like it Quote Link to comment Share on other sites More sharing options...
Martin Whybrow Posted December 21, 2013 Share Posted December 21, 2013 Beb, it might be easier next time to use a D connector with crimped pins; does mean another crimp tool though. With regard to the correct way to do the crimps, the correct tool should have a stop between the conductor crimp and the mating part of the pin; this can either be fixed or sprung depending on the tool manufacturer (and price of the tool). The correct usage is to put the terminal into the crimp tool, close the tool to the first click (almost all quality tools are of the ratchet design), then insert the wire until the conductor butts up to the stop; if the wire has been correctly stripped, the insulation will then be in the insualtion part of the crimp; cycle the tool until it releases and voila, a perfect crimp. Crimps are stronger than soldering; the standard test for a crimp tool is to crimp the terminals onto the wire, then pulll the crimped assembly until failure; the wire should fail, outside of the terminal, and no strands should pull out of the crimp. Solder tends to weaken the wire because there is a stress concentration where the solder ends. Crimping probably does give a lower resistance joint than solder because you're not introducing an extra metal into the joint. Quote Link to comment Share on other sites More sharing options...
Biggles' Elder Brother - Moderator Posted December 21, 2013 Author Share Posted December 21, 2013 Thanks for all the comments and feedback folks - always welcome and encouraging! @Tony - yes mate - good to be back. When work is really busy its hard to get the motivation to go into the cold workshop at 9:00 at night! @Danny - well thank you Mr Fenton, praise indeed from the master! But if the photos are good its all thanks to you getting me to set the camera up better! @Chuck - that particular exercise is not a case of speaking from experience! The original expression I must credit to a Vulcan pilot who was triying to master air-to-air refueling prior to the attack on the Stanley Airport runway! @CSB - agreed, Y-leads are simplier, but you can't easily adjust individual aileron centres or trims, nor can you programme in aileron differential! Also the bomb releases are not exactly "precission engineering"! So I need to be able to individually adjust them - can't do that on a Y-lead. The "grey thing" is the hood for the plug, but I'm thinking of losing it and replacing it with something a little less extravagant on space - probably just a little homemade enclosure from micro-baloons and resin. @Martin - ah mate - I don't possess a posh rachet crimper - just a basic "plain vanilla" type. As I said above there are lots of ways of doing this - I just showed mine. OK, I have been on family "pre-Christmas duties" today, so not a lot of time in the workshop - but what there was was productive. I did the wing servo tests via the connector. Everying was connected up in the wing and the socket fixed in place, then the umbillical cable connected to the wing and then attached to an Rx powered by a NMh 4 cell. First I tested the ailerons - all OK, although reversed. Not a problem, but not fixed now because this is not the Rx the model will end up with - I'll explain later. Next I checked the bomb releases. Now a small problemette raised its head. As far as I can remember I have not removed the servo arms on these or adjusted the push rods since I tested them way back. But they seemed to be well out of adjustment and required a load of sub-trim on each to fettle them? But I did get them working fine - and of course had to check them by dropping the bombs about 20 times with a big grin on my face! Just to be sure you understand Next up, the undercarriage. I had to trim the wheel-well back a tad to allow for the forward swing of the canted undercarriage mountings. That done - flick the switch,.....nothing! Oh dear!. Flick it again,....nothing. Mmmm? But a quick fettle around revealled that the lead wasn't quite "home" in the Rx - recheck,.....bingo! So, that's it - all the servos in the wing fully functional! That means I can now finish sheeting the wing with the last two upper central sheets, brilliant! The reason I haven't fully adjusted everything is that this testing was all done with a 7-channel Rx - ailerons on CH1 & CH6; U/C on CH5. The bomb release is currently set up on CH7 and the rudder channel CH4. Obviously this can't stay this way - but I don't have a spare 8-channel Rx at the moment. So this 7 channel was pressed into service for testing, but its not worth finalising anything on it in the way of set-up. I'll be purchasing a new 8-channel Rx in the new year specifically for this model. BEB Quote Link to comment Share on other sites More sharing options...
Concorde Speedbird Posted December 21, 2013 Share Posted December 21, 2013 I use Y-leads with differential on the Domino, you can do it mechanically by adjusting the position of the servo head when the stick is centred, so because it is a rotating arm you will get more up or down depending on where you put it. You can adjust all those other things you mentioned mechanically too, am I old fashioned?! Keep up the good work, this is an interesting build. My Spitfire with one servo in the wing and only two leads from the wing (retracts and aileron) is looking rather bear in comparison! CS Quote Link to comment Share on other sites More sharing options...
Biggles' Elder Brother - Moderator Posted December 21, 2013 Author Share Posted December 21, 2013 Yes I agree CSB they can be done mechanically - but as I say its not as easy as via programming this way. Both methods work - and both probably end up with the same amount of work to be truthful - here the work is in the build, for yours it in the installation. Swings and roundabouts. I don't think you're old fashioned at all. I think its good that modellers know how to set these things up mechanically as well as by programming their Tx. BEB Quote Link to comment Share on other sites More sharing options...
Monz Posted December 22, 2013 Share Posted December 22, 2013 Posted by Biggles' Elder Brother - Moderator on 21/12/2013 23:37:26: Next I checked the bomb releases. Now a small problemette raised its head. As far as I can remember I have not removed the servo arms on these or adjusted the push rods since I tested them way back. But they seemed to be well out of adjustment and required a load of sub-trim on each to fettle them? BEB Ah, this is probably because the wires from the D connector weren't the same length, a slightly longer bit of wire, like three or four mm will do this. The current has to travel just that bit further so puts things out of alignment... Quote Link to comment Share on other sites More sharing options...
Biggles' Elder Brother - Moderator Posted December 22, 2013 Author Share Posted December 22, 2013 LOL! You know - I never thought of that - it must be true! Onward and upward, time to finish sheeting the upper surface of the wing. First up though I need to protect that socket - I definitely don't want any balsa dust or globs of glue going in there, so some masking tape applied to the connector,... Next we have to get it out of the way - the only real option is to unscrew it and stuff it inside the wing,... I hope we can get it out again! With that done its on with the port upper centre sheeting panel and weigh it down with one or two copies of our favourite model aeroplane publication,... Obviously you can't be absolutely certain that the skin is in contact everywhere under there, but you can get a crafty glimpse at the sides,... Opps! Slightly out of focus - reverting to my old ways! Well at least you know its me! This revealed a small gap - and so even more magazines were heaped on - now I'm pretty sure its fully down! I'll leave that to dry over night and do the starboard inner top sheet (which will be the last) tomorrow. This wing is finally nearing completion - well as far as building it is concerned anyway! BEB Edited By Biggles' Elder Brother - Moderator on 22/12/2013 20:06:11 Quote Link to comment Share on other sites More sharing options...
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