UKpatternflyer

Does anyone know the wiring convention for the Futaba S-Bus extensions, i.e. the wires that allow 2 - 3 servos to be controlled digitally via one Rx socket?

Keith

OhD

Just like a "Y" harness. Just wire red to red, etc.

Jim O

UKpatternflyer

Thanks Jim!

Keith

apereira

Hi Keith,

Please not, you can solder them toghether or use a Y harness, but if you use the S.Bus extension, they might miss the "positive" wire, this is for you to connect a battery there.

Best regards

Alejandro

UKpatternflyer

Hi Alejandro,
Thanks! Not sure if I'm going to go this route, just checking out potential weight savers if I need them in the future. In this case its a four wire- 2 servo extension 1m long vs the equivalent 3 wire S-Bus extension. So the weight saving is just the extra wire at 1m. So perhaps 5g saving at standard Futaba wire thickness's? The down side is an S-Bus controller to program the servos (I don't have an 18Mz), and extra complexity if I have to replace a servo in the future. Still I suppose its worth knowing about

Hope you're well

Keith

serious power

Hi Keith,
Don't mean to divert the thread (this may help anyway).

Question for the tech guys ;
How much current is there in the signal wire ??

I have sourced high quality wire that is only 1.2g per metre.
If the current in the signal is low one could replace the existing signal with this and run an extra one for the second servo - And be lighter than the original 3 wire length.

Keith, An other thing that I am looking at right now is servos.
Us EP users are over-spec'd at present. We are using the same servos as the GP users - no need !!
Us Contra users are even more over-spec'd. We are using the same servos as everybody else - absolutely no need !!
Typical servo load on a mono is from 225g to 250g. On a bipe it's from 225 to 325 - + cables to suit.
I have two seasons with a bipe and a 125g load of servos - both Pletty and contra powered - - And I'm looking at going lighter.

Brian

radioflyer9

I am also considering S. Bus vs "Lite" extensions (30-32 AWG) in a bipe to try to save some weight on wires. Does any body have any experience on using 30-32 gauge extension servo wires, as used on smaller electrics and foamies, for the mini servos on ail, and ele?

Thanks,

Caglia

serious power

Hi Rf9,
What do you mean by 'mini' in servos.

Brian

radioflyer9

I was considering either the Futaba 173HV's or JR 3711HV's for the wings and two elevator halves on a standard 2M bipe for F3A.

Here is a link of an example of the servo extensions: http://www3.towerhobbies.com/cgi-bin...?&I=LXKKT1&P=6

Thanks

serious power

Is this for EP or GP ??

Brian

radioflyer9

Its for an electric bipe

serious power

Hi,
Check out ;
http://www.mks-servo.com/

I think we go much lighter on servos.

Brian

UKpatternflyer

Hi,

I think these are the extensions I was going to use in my Citrin, rather than the 26swg wire it has at the moment. This has 173HV servos (6!) and an 9170SV servo for rudder

However tring to save 5g on an elevator 4 wire extension becomes a nonsense when I can change props to a moden carbon lightweight (e.g. Falcon) and save nearly 100g. As I mentioned I'm only looking at this in case the need arises in the future to save every gram!

Brian, I suppose with the minimal vibration present you could always look at using a few paralell strands of enamelled copper wire, such as the type they use in transformers / loudspeaker voice coils. They carry a surprising amount of current. I say use a few strands as an insurance in case they stress fracture. Or network cable strands (the super tough nylon coated cores) could be used also


Keith

apereira

Hi Keith,

I will be using the S.Bus on the Accuracy bipe, which uses the same setup as your Citrin, but S.Bus will go into Alilerons as I want one wire to come out of the wings, and they will go into a Futaba Y extension, so I will not care for making wrong connections on the four servos as it will be safer when assembly the airplane on windy days, the stabs I haven't decided yet, but rudder and throttle will be on regular channels, all HV, but with an Emcotec 7.2V dual batt 900mAh.

Probably you will not change a servo flying GP or EP, but I Understand your point. Buying a servo programmer will not make sense as it comes with the newer radios, but at the same time, you only need to "tell" the servo to wich channel to respond once, the rest of the programming I don't think is usefull for F3A, you can do all the relevant funtions with the Tx already, it is there if you want to try it but not necessary, so at the end you could borrow someone Tx or programmer just to tell the servo wich channel it is at and be done, the servos come with stickers to identify them to the channel they are programed to, but I also understand we don't like to rely on some elses equipment, I am that way.

I think the weight savings could be around 20grs total on a biplane, not much, but it is more about trying the new systems for me, and hope I will not need to save weight anyway.

best regards

Alejandro

UKpatternflyer

Hi Alejandro,

Yes its good to try new things though if I had an 18MZ, I'd be able to try a lot more. At least I'm giving HV a go now , which seems pretty good with the servos I've chosen.

Keith