Daniel Cardona Posted May 8, 2011 Share Posted May 8, 2011 hello to everyone, i need some good advice about what servos are best for my current project, a sig 1/4 scale piper cub. i think i would need at least 2 high torque servos for rudder and elevator. the ailerons i think with a 5 kg stantard servo's will do good, but any advice will be welcome. i looking for ANALOG type not digitals, the problem is i dont know where to start. anyone maybe has a nice list in mind so i can choose? kind regards Daniel Quote Link to comment Share on other sites More sharing options...
Phil 9 Posted May 8, 2011 Share Posted May 8, 2011 why would you want to avoid digital servos? Quote Link to comment Share on other sites More sharing options...
Lindsay Todd Posted May 8, 2011 Share Posted May 8, 2011 Hitec HS645 Utra Torque seem very popular Quote Link to comment Share on other sites More sharing options...
Phil 9 Posted May 8, 2011 Share Posted May 8, 2011 hEdited By Phil B on 08/05/2011 21:08:59 Quote Link to comment Share on other sites More sharing options...
Daniel Cardona Posted May 8, 2011 Author Share Posted May 8, 2011 phil what i think is that digitals tend to drain the batterys more than analogs. and since that the piper cub have to balance tabs on the elevator and its quite big at 1/4 scale i think analog type are best. i dont need power for a 3D type model. but ....any advice will be welcome and interesting to see what people thinks regards Daniel Quote Link to comment Share on other sites More sharing options...
Phil 9 Posted May 8, 2011 Share Posted May 8, 2011 I would think for a 1/4 scale large capacity rx battery is required (even for analog servos ) and also a second battery as a back up. Quote Link to comment Share on other sites More sharing options...
Daniel Cardona Posted May 8, 2011 Author Share Posted May 8, 2011 i agree in fact i already had in my to use a battery backup , 2 batterys of a least 1200mah the hitec HS-755 and HS-645 are analog type? there's nothing mention in the specs cheers Daniel Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted May 8, 2011 Share Posted May 8, 2011 I believe some of us are seeing the words "quarter scale" and visualising big 3D models. If my figures are correct, a quarter scale Cub with an 18 x 6 running at 9000 rpm would have a theoretical top speed in level flight of no more than 50 MPH. Putting the assumed deflections (and not forgetting to set up your servo linkages to give output arm deflections of around 100% for efficiency) into an on-line servo calculator gives the following torque requirements (assuming worst case scenario of a single elevator servo): Ailerons (30 degrees each way ignoring differential) = 1.8 kg-cm Elevator (30 degrees each way) = 2.0 kg-cm Rudder (45 degrees each way) = 3.0 kg-cm ...all of which are comfortably within the range of a humble Futaba S148 standard servo! On top of this is the fact that these are figures for maximum deflection at 50 MPH and in practice you're unlikely to be flick rolling a Cub at VNE...and I hope you'd be throttling back in a dive. So I think that rather than getting obsessed with torque figures, just go for decent quality ballraced standard servos and leave the big money high torque and digitals to the large scale 3D merchants! Having said that, please don't forget that even a lightly built 1/4 scale Cub is a large model so you do need to satisfy yourself that any advice is well founded and I hope others may comment on my "heretical" opinions! Hopefully, the Hangar 9 Cub has linkages and control surfaces which are properly designed but don't forget that flutter can be exarcerbated by any play or flexibility and make sure that everything is as well set up as possible.Edited By Martin Harris on 08/05/2011 22:03:20 Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted May 8, 2011 Share Posted May 8, 2011 Try HERE. Quote Link to comment Share on other sites More sharing options...
David Ashby - Moderator Posted May 9, 2011 Share Posted May 9, 2011 I think that's good advice Martin. My gut feeling was that std servos would be fine but you're got the slide rule out Quote Link to comment Share on other sites More sharing options...
Daniel Cardona Posted May 9, 2011 Author Share Posted May 9, 2011 yeah personally i didn't expected to have an advice like this. the theory makes sense, for me it's better because obviously i will pay much less for good 5kg standard servos. but why then i'm still afraid to make such a guts move. maybe because i'm speding a lot of hours in building the model? sould be nice to hear someone experience with a same size of model cheers Daniel Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted May 9, 2011 Share Posted May 9, 2011 My 1/4 scale Cub (ASP160 twin, 18 x 6 G-Sonic) at @ 7.5kg seems fine on JR 591 standard servos... Quote Link to comment Share on other sites More sharing options...
Chris Channon Posted May 18, 2011 Share Posted May 18, 2011 Hi Daniel, i use futaba and s303 std servo's on my 1/4 scale Stampe's, no problems what so ever. I have one Stampe powered by a Saito 120 f/s and the other is powered by a S C 180, very much overkill on the engine front but you don't need full throttle all the time !!!!! So, yes std Futaba servo's will be more than capable in the Cub. One Rx battery of a reasonable capacity will be fine ( galaxy do a 4 or 5 cell rx pack of 3,300mah which will be fine.) Hope this helps a bit regards Chris. Quote Link to comment Share on other sites More sharing options...
Daniel Cardona Posted May 20, 2011 Author Share Posted May 20, 2011 well thats its impressive futaba s3003 on a 1/4 scale stampe! definatly more aerobatic than my cub.still i'm a bit confused and worried. i'm thinking of the elevator still hard to believe for that large elevator, on ailerons i think i will have a go Quote Link to comment Share on other sites More sharing options...
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