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[mbm999]

Hi,
Can anyone tell me what the difference is between the various flavours of Flysky receivers?

I guess its really just the fs-ia6 and fs-ia6b (I'm assuming that the ones with fs10 are the 10 channel versions and the one with no case is a lightweight version).
Is it just telemetry that is added in the ia6b (and what is IBUS and PPM related to) - why would i need/not need them?

I'm also curious where people buy their servos from for example the Futaba s3003 (the s148 which i presume is the metal geared equivalent) and how they choose one to fit the application (eg. a rudder = standard servo assuming space allows).

Oh, and probably the daftest question - what is the aplication of the servo used for eg. circular, star shape, single arm

Thanks,
Mark

[Andyn]

Addressing the servo question- you choose your servo to fit the application you are putting it in. For example, I'm about to start the build on a Seaducer 90, the current world mono speed record holder. On rudder I'm going to use a Savox SB-2292SG. Fitting a servo that has 31 kilos of torque at .07 of a second to 60 degrees and costs £120 in my application makes perfect sense, whereas for a small scale destroyer would be downright silly. In the same model, I'm fitting a Hitec HSG-8315BH on throttle. This thing has 5.3 kilos of torque at .04 seconds to 60 and if I fitted it on rudder it'd be about as much use as a chocolate teapot - and would last about 5 minutes.

Servos also come in different sizes, most easily suited by their weight - Micro, mini, standard and quarter scale are the most common. Again you suit the size to the model you're building.

Also note, the S148 is NOT metal geared. It's actually a very old servo which I believe predates the S3003. They're both very average servos and better options are out there.

[JimG]

i-Bus is the FlySky version of S-Bus used by Futaba and FrSky. Spectrum and others also have their own version. This is a serial bus for servos and other controls. Instead of using separate to each servo they are all linked with a single lead. This needs either dedicated S-bus servos or a convertor between the serial bus and the servo. FlySky uses a convertor box which allows the use of 4 servos per box, the box can be programmed to determine which channel each servo uses. A serial bus can be used to provide more channels than the receiver has servo connectors. (I use a FrSky transmitter which can provide 16 channels but the receiver has only 8 servo connections. By using 2 S-Bus convertors I can connect 8 more servos. ) Another advantage is if the servos are some distance from the receiver (e.g. a multi servo wing on a large model aircraft. Only one lead is needed to drive them and they often have a separate battery per set of servos reducing voltage drop on a long wire.  Some multirotor flight controllers use the serial bus as input, needing only 1 lead instead of at least 4.PPM is another form of output signal, basically taking the receiver input and sending it straight out instead of passing it through the decoder to split it up into seperate servo signals. Again mainly used for multirotor flight controllers to reduce the number of connectiong leads.i-Bus and PPM are unlikely to be needed in the average boat.
Jim

[derekwarner]

Andy....these SB-2292SG with 31kg of torque @ 10mm is a pretty big number......the manufacturers mounting shows the usual rubber bushes+ brass eyelets + the option of the wood screws or ~~M2? metal thread bolts


So we understand the choice of one servo over another due the in essence thermal capacity, but the question then is, do you design & in-build the weakest link in the rudder system to save the servo of gross mechanical seizure?


1. rudder blade
2. rudder blade mounting
3. rudder pintal
4, 5 & 6...or
7. the four x M2 metal thread screws?

Derek

[Andyn]

You chuck the plastic arms in the bin, fit high quality ally arms, then mount it with the rubber inserts and M3 screws onto a decent CNC ally servo mount... On my models the rudders have an M4/M5 pivot pin and an M3 brass shear pin, if you hit something substantial it kicks the rudder up by shearing the brass pin. In my submerged drive boats if you're unlucky enough to damage something underneath it'll be the shaft outer and inner, skeg, prop and (hopefully not) the engine bearings.

Having done a little reading I am correct about the S148, it's a lower torque, slower S3003. Both are single bushed with plastic gears.

[derekwarner]

Thanks for that...it certainly appears to be a logical mechanically sound approach with the last link being the M3 brass shear pin etc......Derek

[mbm999]

Hi,
Thanks for the replies, just a few follow ups please ....

Servos:
So, is there any recommendations for how you spec a servo - I have no idea how much force will be needed to move the rudder (Aeronaut Diva) - clearly not in the same league as you application - are there rules of thumb or is it just experience (or clever calculations).
If those servos i mentioned are just average and a bit long in the tooth - what would you say are the more current crop.

Receiver:
Got it thanks - hopefully you can ignore these functions by transmitter options and use normal servos. I guess then there is no need for the Ibus/ppm receiver (assuming no telemetry required) and the IA6 is perfectly adequate for boat use.

Thanks,
Mark

[coch y bonddu]

I Would use a futaba 3003 for your application no need for anything stronger,I use them in all my boats from a 18ins one to a 48ins sea queen




Dave

[derekwarner]

Mark......I would also be interested to understand Andy's thoughts on the mechanical strength requirement in driving & holding a rudder against the forces of the water


When we think of a slower vessel.....we simply adjust the rudder servo set points by the arc of movement via the Tx...lets say +35 degrees to - 35 degrees of ~~ 70 degrees port to stdb ....so then set & forget


When Andy talks about 'frying' a servo I assume that the brushed servo motor is arcing on the communicator.....drawing extra current due to the mechanical load/force on the rudder blade relative to the effective weight [not displacement] of the vessel in a turning movement ....acceleration/de-celeration, inertia, G forces? etc

So when I mention the 'SB-2292SG with 31kg of torque @ 10mm is a pretty big number'........the only way my mind can visulize this is  a 30% oversize 25kg bag of cement [ouch] tethered 10mm from the servo drive axis

How many of our members would be capable if lifting and holding a 31 kg bag of cement? [count me out for a start]

Derek

[barriew]

The FS-i6 receiver has telemetry, the FS-R6B doesn't. If you don't need telemetry go for the cheapest, which is not always the one without!! There is a 4 channel version (FS-2A?) also which is sold as a park flyer but is still suitable for boats assuming you don't sail your boats out of sight.


Barrie

[mbm999]

On the subject of sizing servos i found this write up which usefully has a table of boat length to torque (clearly just a guide and i have no idea what it's based on).
http://www.radiocontrolinfo.com/radio-gear/servo-selection/

Thanks for the receiver info too.

Cheers,
Mark