Four servo wiring harness

[Vaughn Entwistle]

Can anyone tell me it’s possible to buy a pre-made wiring for an f3f ship. I’m talking about the typical three piece wing with two flaps and two ailerons that plugs into a harness in the fuselage. I need to replace the existing wiring harness that uses Multiplex plugs but has loose wires and my soldering skills aren’t up to making the repairs.

When I lived in the US, I was always able to buy pre-made harnesses. Are these available over here?

Thanks, Vaughn

[satinet]

I think hyperflight sells them but I don't think they are available in custom lengths

 

[wookman]

Soldering is such a fundamental skill to have for building and refurbishing large gliders. I would seriously suggest you practice until you get good at it. It is a skill you will never regret acquiring. 

Three piece wings are often done with D connectors for the fuz/wing interface. Now they will test you soldering skills a bit more than a greenie.

[oipigface]

I agree with Graeme. It took me a while to get reasonably good at soldering, but now I have even managed successfully to wire up a small PCB. You can practice as Graeme suggests, but you can also choose only to tackle relatively simple tasks. I first started by shortening wires that already had plugs and sockets fitted. So get your pre-made harness, cut a length out, and solder the wires back together. This is simple compared to a greeny because the wires can be manipulated so they aren’t close to each other. 

I use a Weller soldering gun for this, and a cheap set of helping hands. Stripping wires can be done with a knife, but it’s better with wire strippers. I strip about 1/2” of sheathing from the cable ends, twist each separately, then bend them into 1/4” hooks. Use the helping hands to fit them together. Make sure they are neat and tidy so that the joint is no fatter than the original wire. Get gun up to temperature (takes about 10 secs). Hold tip against joint and apply solder until it runs. 
The next thing I do usually is remember that I haven’t fitted the heat shrink!

Done like this a joint takes up about 1/2” of wire.

I think the key thing is to be sure that the iron is sufficiently hot to enable the solder to flow. If you are doing a repair you also need to make sure that whatever it is you are trying to solder is scrupulously clean.

 

[MikeE]

Lots of videos on the net, but as my dad always used to say to me,

Quick and clean.

[Vaughn Entwistle]

Thanks guys for all the good advice. It looks like I am going to have to bite the bullet and attempt the repair myself (although I'm tempted to just sell the glider on at this point.)

I didn't go into detail in my first post, which I see now was not a good idea. First, let me tell you about the glider. It had obviously been through the wars. At some point the fuselage was broken in two behind the wing saddle, but I can now tell that the glider had accrued a lot battle damage. The previous owner had repainted the fuselage and wing (no doubt the hide the repairs.)

As I said, the left flap and aileron were dead when I got it home. The MPX connectors (one set in the fuselage and one on the bottom of the wing both looked t be in rough shape. Plus the wing saddle was not a good fit for the wing. Someone has ground away on the bottom of the wing, exposing the carbon, presumably to make them a better fit (but they're not).Things would work and then stop working as I tightened down the wing bolts, so the MPX connector was obviously not making proper contact. I decided to Dremel loose the top (wing) connecter to see what was going on. As I eased the connector out of the wing, several wires came loose. Something had been applied to the wires (hot glue?) to provide strain relief, but it turned to dust in my hands. 

A twisted pair of brown wires had come loose. I soldered them back on as it was pretty obvious which pin they had been attached to. But then a red wire came loose and I have no idea which pin that came from. I have looked on the Internet to find a wiring diagram show an MPX plug and how to wire it but I cannot find one. (Anyone know where to look?)

Another concern is that the wiring is really beaten up. There are cuts and slashed through the insulation of many wires. I have no idea how that can happen to wires inside a wing. 

Any suggestions?

[oipigface]

1 hour ago, Vaughn Entwistle said:

Any suggestions?

My suggestion after looking at the photos would immediately be to ditch that wiring, and do the whole lot from scratch. (I’m assuming in saying this that the airframe itself can be put to rights.)  The fact that the wiring internally is damaged as well makes it even more the way to go. It might have got that way if a heavy-handed installer or repairer had tried to pull the wires through a gap too small for them. 

I take it that both halves of the MPX connector were fixed in their places? I would consider making at least one of them a fly lead, especially since it looks as you have problems with an ill-fitting wing-seat. Secondly, I would definitely fit two - one for each wing. It sounds as if it has been wired with the power for all four servos running through two pins which is OK, but especially since you aren’t experienced in this kind of thing, you need to keep it simple.

You don’t say much about the state of the fus wiring. I would be inclined to think that it probably has had a hard life as well, and ditch it too. 

Tom was right about hyperflight. They do sell something that will probably do the job as a replacement: https://www.hyperflight.co.uk/products.asp?code=HS-4119-34-80&name=large-lightweight-4-servo-wing-wiring-harness-80-cm-2. You don’t say what your plane is, or how big. If you need to adjust lengths of anything then do what I suggested above. Leave the terminals on and chop a bit out of the middle of whatever part is oversize.

But I do agree with Graeme. Better for your soul, and probably your pocket, would be to have a go at doing it yourself…… but then this is quite a big job. Maybe better not to jump in the deep end.

Finally, it doesn’t really matter how you wire MPX connectors as long as the halves match. I always do mine like this, where the red, black and white (or whatever the colours the +ve, -ve and signal are) on each side all belong to one servo:

 

:

 

[Vaughn Entwistle]

Hi Oipigface,

The dodgy state of the wiring and the wonky wing saddle was originally why I was trying to buy a ready-made wiring harness. However, I called Hyperflight today and they can no longer get the premade harnesses. So now I face a real dilemma.

I think you're right about switching to two separate harnesses, one for each wing. There is an MPX female connector set flush into the top of the wing saddle (and that looks in rough shape). The fuselage harness coming from that is extremely short, so much so that plugging the servo leads into the receiver is a soul-crushing experience. If I replace the upper wiring I will have to Dremel the connector out of the fuselage wing saddle, which obviously means I now need a lower harness too. (Can you see why I was hoping to be able to buy a premade harness?) The irony is that I bought this plane because I don't have time to build models because of my work, and already this thing is sucking down the hours with nothing to show for it. 

The plane, by the way, is a Stork II (127 inch wingspan) In some ways it is a nice plane. It has KST digital servos all around. But the wiring thing is giving me fits. I've built out a number of molded gliders, but I've always been able to buy a wiring harness.

The other complication is that there are Deans four pin connectors going to the outboard panels, so I would need to Dremel them out and replace the wires. Sigh. This all seemed so simple, but has turned into a nightmare. I really want to fly this glider, but it would probably make sense to sell it cheap and move on. 

Thanks for all your help and advice.

[oipigface]

You could always import one - at a cost! 
https://alofthobbies.com/mix-and-match-glider-harnesses.html

Best of luck!

[wookman]

You have got some seriously skanky wiring there Vaughn. That's bit the lot and start again territory for sure. 

There is no easy way to a nicely sorted mouldy. 

I try to buy cheap and just accept there will be work to do. 

But it is quite possible to buy expensive and still end up with a pile of work. 

Buy new. Very expensive with a load of work to do. 

Are you spotting a common theme emerging here yet?

[Vaughn Entwistle]

Hi Oipigface,

The state of the wiring and the wonky wing saddle was originally why I was trying to buy a ready-made wiring harness. However, I called Hyperflight today and they can no longer get the remade harnesses. So now I face a real dilemma.

I think you're right about switching to two separate harnesses, one for each wing. There is a MPX female connector set flush into the top of the wing saddle. The harness coming from that is extremely short, so much so that plugging the servo leads into the receiver is a soul-crushing experience. If I replace the upper wiring I will have to Dremel the connector out of the fuselage wing saddle, which mean I now need a lower harness too. (Can you see why I was hoping to be able to buy a premade harness. The irony is that I bought this plane because I don't have time to build models because of my work, and already this thing is sucking down the hours. 

The plane, by the way, is a Stork II (

[Vaughn Entwistle]

I hear you, Wookman. Over the years I've gone both ways. I've purchased brand new gliders and fitted them out myself (surprisingly time consuming when you consider the bloody thing is built, all you have to do is install the servos, balance the beast, and program the radio. I've also purchased a number of used gliders and have had good luck for the most part. 

I have been out of flying for the past five years as I am trying to build a new career as a novelist. I recently finished my latest book and decided to "reward" myself by buying a used plane. I didn't know I was buying a massive headache and a time suck. Since buying the Stork II a fellow club member decided he was done flying and started selling all his models. I picked up a Whisper and a Starlight 3000 from him. They are not brand new showpieces, but they are now ready for service and I look forward the getting them out on the slope soon. 

I should probably give up on the Stork II, reduce the price, and move on. I really can't afford the time to fix it, but I've always wanted a Stork II, so I might keep trying to find a ready-made wiring harness, even if I have to import it from the states. 

[Vaughn Entwistle]

Oipigface, thanks for the link. I think I'd rather pay the customs duty on one of these ready made harness than faff about trying to make my own.

It might be checkbook modelling, but my time is precious!

[Mikeb52]

1 hour ago, Vaughn Entwistle said:

I hear you, Wookman. Over the years I've gone both ways. I've purchased brand new gliders and fitted them out myself (surprisingly time consuming when you consider the bloody thing is built, all you have to do is install the servos, balance the beast, and program the radio. I've also purchased a number of used gliders and have had good luck for the most part. 

I have been out of flying for the past five years as I am trying to build a new career as a novelist. I recently finished my latest book and decided to "reward" myself by buying a used plane. I didn't know I was buying a massive headache and a time suck. Since buying the Stork II a fellow club member decided he was done flying and started selling all his models. I picked up a Whisper and a Starlight 3000 from him. They are not brand new showpieces, but they are now ready for service and I look forward the getting them out on the slope soon. 

I should probably give up on the Stork II, reduce the price, and move on. I really can't afford the time to fix it, but I've always wanted a Stork II, so I might keep trying to find a ready-made wiring harness, even if I have to import it from the states. 

Vaughn,

If you send me the plugs and wire, and the exact lengths needed, I’ll make them up for you. No charge, but a donation to

blood cancer uk, would be appreciated. 
Email me through here, and I will give you my address. 
Mike. 

[wookman]

Good offer that Vaughn. Mike knows what he is doing. 

[Ned]

I know it’s a nuisance but the best thing to do here really is to knuckle down and learn how to solder. A couple of hours practice will see you ready to do your own plugs. If you’re soldering multiplex plugs there’s a couple of things that can help.
Firstly, make sure the other half of the connector is plugged in, this will help hold the pins straight if the green plastic gets a little heat softened. 

Secondly, tin both the plug pins and the wire end, that means to apply soldering iron and the solder to the bare connections so they have a thin coat of solder on them. Then all you have to do is place the wire end in contact with the pin and apply the iron for just a second to melt the solder. Don’t forget to slip the heat shrink tube over the wire first! It will also help if you can get hold of a plug heat sink, there’s a variety available and you should be able to clamp your plug assembly into it to help keep it cool. I bought mine to solder XT60 plugs but lots of things fit into it.

Finally, the other skill worth acquiring is being able to crimp up your own JR/Futaba servo plugs. This requires a small investment in the correct crimping tool as well as shells and pins: you can often get it as a kit from the likes of eBay. I’ve found it one of the most useful skills I’ve learnt, and it saves money in the long run as you can make up your own connections or extension leads as required. There’s some good YouTube videos on how to do it too which are well worth watching.

I’ve included a coupled snaps of a heatsink and a newly made wiring harness showing both types of plug: this will have the multiplex plugs potted with hot glue once everything is installed and all connections have been tested.
 

[oipigface]

23 minutes ago, Ned said:

Finally, the other skill worth acquiring is being able to crimp up your own JR/Futaba servo plugs. This requires a small investment in the correct crimping tool…

I agree with the point about being able to crimp your own plugs but not about the crimping tool. I’ve only ever had success with a pair of needle nosed pliers.

The heatsink might be worth a try as well.

[satinet]

2 hours ago, oipigface said:

I agree with the point about being able to crimp your own plugs but not about the crimping tool. I’ve only ever had success with a pair of needle nosed pliers.

The heatsink might be worth a try as well.

They do work. I've been crimping for baby years. I've recently been crimping just plugs as well.

I think a lot of down to the the tool. Jst and servo plugs crimp tools look virtually identical but completely mess up the wrong connector. Fine tolerances.

[f3fman]

I gave up crimping when I found that either I, or the crimper I was using, wasn't up to the job.

I buy relatively inexpensive plug, socket, and extension leads and extend as necessary with servo cable  

 

[cirrusRC]

ENGINEER PA-09  well with the expense over cheap versions.