Combining servos

[EGB 953]

I am about to start an ARTF 25 IC trainer. It calls for four standard servos. i have a Futaba TX/RX and wondered if i should contemplate digital servos or if that is a waste. Do I need to get Futaba servos or would any standrad servo be ok, and finally, to save weight it seems logical to me to use a mini servo for the throttle as it shouldn't need much torque, but can you combine it with standrad on the same RX. Plus, recommended battery pack?

[J D 8]

   Servo sizes can be mixed. You do not need to use Futaba servos, however beware there are some rubbish servos on the Flebay [ Futaba copy's and others ] Go to reputable shop site like Steve Webb. Digitals not needed for trainer.

 I use Eneloop flight pack from Components shop UK, 4.8 and 6v available the former fine for a trainer.

[Martin Dance 1]

For the type of model you are building standard analogue servos will be fine. The manufacturer really doesn't matter they all are fitted with standard JR plugs and will run on 4.8v. Although you can use 6v on most servos your application doesn't need it. One word of warning be very wary of buying servos on ebay. Even Futaba servos may well be fake, buy from a reputable UK based seller. Good luck with the build and happy flying

[Martin Dance 1]

Looks like JD8 and I agree. Should have said although there is no technical reason for not mixing servo sizes. You may find fixing one odd sized servo in the fuselage is more difficult. It's usually easier to have the three servos you will use on a trainer all the same size.

[Nigel R]

I'd use Hitec 311 on that.

 

https://www.servoshop.co.uk/index.php?pid=HITHS311

 

£42 for 4 of them, reputable seller, etc. etc.

 

But you could use a micro for the throttle, if you wanted.

 

https://www.componentshop.co.uk/4-8v-2000mah-aa-eneloop-square-battery-pack.html

 

Eneloop is my choice for this sort of thing.

 

I'd avoid radio gear on ebay - unless you're sure of the seller being genuine.

 

 

[EGB 953]

15 hours ago, Nigel R said:

I'd use Hitec 311 on that.

 

https://www.servoshop.co.uk/index.php?pid=HITHS311

 

£42 for 4 of them, reputable seller, etc. etc.

 

But you could use a micro for the throttle, if you wanted.

 

https://www.componentshop.co.uk/4-8v-2000mah-aa-eneloop-square-battery-pack.html

 

Eneloop is my choice for this sort of thing.

 

I'd avoid radio gear on ebay - unless you're sure of the seller being genuine.

 

 

Thank you that is very helpful.

[Sheepish]

Vapextech are also great for flight batteries and also a good and cheap charger for the nimh chemistry flight battery too.

 I have used their batteries and chargers for several years in lots of different models with no problems.

[kc]

All the above is good advice.    What nobody mentioned is that Futaba brand servos  have a tab on the plug which means they can only go in the correct way, whilst other makes and also extension leads don't have this which means they can be plugged in the wrong way.   Doesn't do any harm the wrong way but it won't work so just insert the other way.   Several charts can be found online which shows various colour leads and how they compare to Futaba, typical one is here.

The same tab on Futaba servos might have to be removed to insert into other makes of Rx etc.

Edited March 31, 2022 by kc

[Nick Cripps]

Well, not entirely true, KC. The other servo brands which don't have the tab, have 2 of the plug corners chamfered and corresponding cut-outs on the receiver to ensure they are inserted the correct way around. It is possible to get it wrong but is usually obvious if you do.

Also note that if you use Futaba servos with other brands of receiver then not only do you have to cut off the tab but you also need to file a chamfer on the servo plug.

[john stones 1 - Moderator]

Or you could simply remove the Futaba plug, easy done, lift the tab and pull out the pin and replace with the correct one.

[flight1]

My RX's can fit Futaba or Jr style servo plugs, So i buy what ever I feel like at the time.

and as for a trainer standard analogue servos will do, no need to complicate things.

As above buy from a known shop as a lot about are poor copies.

Hitec 311 are fine and for a smaller budget try the K-Power P0600  .

As for the latest futaba they are going to the s-bus compatible new range see Futaba SU300 which work on standard pwm RX's and the s-bus ones. The servos proberly are all going that way in the future.

 

Edited March 31, 2022 by flight1
gramma

[Dale Bradly]

Re throttle servo, by all means use a mini, but this is not the place to skimp on a cheap or dodgy servo. For one, if the servo goes haywire with the engine running, there is a chance, however small, of serious consequences,  and I dont mean to the airframe. Secondly, you will never get a reliable idle if the servo has rubbish resolution/accuracy. 

[Martin Harris - Moderator]

On 31/03/2022 at 16:08, Nick Cripps said:

 

Also note that if you use Futaba servos with other brands of receiver then not only do you have to cut off the tab but you also need to file a chamfer on the servo plug.

That may be the case on extension leads (although despite the chamfers, in my experience it is easy to reverse them when fiddling in dark corners of a fuselage) but do many brands (other than those using Futaba plugs) key the connectors into their receivers  - I can’t say I’ve come across any…

 

I've always preferred the Futaba system but that may date back to my original choice of system in 35 MHz days. 

[Simon Clark]

5 hours ago, Martin Harris - Moderator said:

but do many brands (other than those using Futaba plugs) key the connectors into their receivers  - I can’t say I’ve come across any…

All my old JR receivers had a small chamfer so are keyed just like extension leads but as everyone says, very easy to put in the worng way round

[Matt Carlton]

I put a small dot of paint on the rx. A white spot on the side where the white (or yellow) strand of the lead goes, makes it very easy to see which way round to plug in the leads. 

 

That said, if there is space, I like to use a short extension lead anyway so that any unplugging puts less strain on the rx pins, especially if the rx is tucked away out of sight.

 

 

[GrumpyGnome]

As said, use of small extension leads stops the constant plugging and unplugging of leads into Rx, and reduces the chance of damaging the Rx, or putting leads in incorrectly.

 

Don't forget to use those little plastic 'lead locks' for any extension to servo lead joints......