David Wilson 25 Posted August 30, 2018 Share Posted August 30, 2018 Hi all,First post on here, but I've been flying for a couple of years and thankfully this won't be my first build...Anyway, I was handed 3 black sacks of UNOPENED bits for the maligned deagostini Spitfire... Thinking "what the heck, how bad can it be?" I'm going to build and fly it.Anyway, I'm not willing to trust the Code4 AS322 Deluxe servos, but I'm not sure what to use instead... The documents provided say a good rule of thumb for servo torque required is 0.75x control surface area.The aileron is 84cm², so that suggests 63kg.cm of torque... I can only assume they mean 63N.cm or 6.4kg.cm?The elevators are much bigger and come in around 160cm².Even googling the hitec servos that Code4 are purported to be a rebrand of show a torque value of only 3.0kg.cm...Can anyone provide guidance on what is a good method of determining torque requirements?The calculator at http://www.mnbigbirds.com/Servo%20Torque%20Caculator.htm suggests ~3kg.cm for 45° deflection at 100mph.I don't mind gross over-speccing the service, but definitely don't want to be caught short! Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted August 30, 2018 Share Posted August 30, 2018 Something like this should help - I bet you are surprised how little torque is actually required - the ubiquitous Futaba 3003/3004 or 148 if they are still available would be more than enough... Quote Link to comment Share on other sites More sharing options...
Alan Gorham_ Posted August 30, 2018 Share Posted August 30, 2018 I think the AS322 servo is just a rebadged Hitec HS322 servo. Nothing wrong with the Hitec servo as a budget choice in a simple model. First link on google for the Hitec servo: **LINK** Quote Link to comment Share on other sites More sharing options...
Don Fry Posted August 30, 2018 Share Posted August 30, 2018 Any servo with similar spec to the HS322 will work easily. If you are using two servos to move the ailerons, 30 gram standard jobs will do, with a good margin to spare. By the way, the airframe is OK, and it flies just fine. Try to keep it light. It just isn't worth what the magazine buyers paid for it. Your calculator says big servos, because you asked for 45° deflections at 100 mph. Flat out in a long vertical dive, you will get about 60 mph your airframe, and your control throws will be ITRO 10 to 15°. Big difference in servo needs. Edited By Don Fry on 30/08/2018 13:04:22 Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted August 30, 2018 Share Posted August 30, 2018 Posted by Martin Harris on 30/08/2018 12:01:33: Something like this should help - I bet you are surprised how little torque is actually required - the ubiquitous Futaba 3003/3004 or 148 if they are still available would be more than enough... Whoops! I missed your link when I replied but I very much agree with Don. A standard servo will be more than enough for this model. Most club speed merchants claim 200 mph for their models - very few will fly significantly faster than 100 mph and sports models such as the De'Agostini Spitfire will cruise at something like 55 mph with maybe 85 mph possible in a full power diving pass. I have fitted both pitot tube airspeed telemetry and GPS in various models so I think I have a realistic idea of model speeds. I would go for quality over claimed torque. Edited By Martin Harris on 30/08/2018 13:25:27 Quote Link to comment Share on other sites More sharing options...
David Wilson 25 Posted August 30, 2018 Author Share Posted August 30, 2018 Cheers guys! 100mph and 45? deflection was picked as absolute worst case demand. I knew the advice in the Spit paraphernalia had to be out by at least a factor of 10!I'm definitely going to do a servo per aileron and contemplating pull-pull rudder rather than the push-rod. Also going electric to fit with the rest of what I fly. Quote Link to comment Share on other sites More sharing options...
Engine Doctor Posted August 30, 2018 Share Posted August 30, 2018 They work fine for the Agostini Spitfire . It fly's quite well and have test flown quite a few in the past The main bug-bear was the aileron torque rods are useless and allow the ailerons to blow back really affecting roll performance . Either substitute the wire for stiffer thicker gauge or better still put a servo on each aileron . All the ones I flew were fitted with the supplied servos which were fine for the job . if you use two on the aileron then any standard servos like a Futaba 148 or whatever the number is now will be fine for throttle. The engine that came with it was a LEO which I believe is a generic ASP <SC etc engine and is fine for a bit of fun . Enjoy ! The best thing is you never paid the exorbitant price they cost when new !! I think it was nearly £400 at the time . Quote Link to comment Share on other sites More sharing options...
Denis Watkins Posted August 30, 2018 Share Posted August 30, 2018 These turn out a nice looking model David, and can be over engineered in places and come out heavy. Just build as instructions, using epoxy at the engine bay mount, and aliphatic for the rest. Have the motor run-in, fully ready to install, meaning, do not run the motor in, during flight, on the Spitfire. As always, don't glide in, fly in to the touchdown. We have two of these at the club, both flying on .46s and not the provided Leo, though the Leo is adequate if you want to stay true to the design. It was found most comfortable flying with the least recommended surface movements, especially the elevator. Keep us posted Quote Link to comment Share on other sites More sharing options...
David Wilson 25 Posted August 31, 2018 Author Share Posted August 31, 2018 I'll be converting to electric propulsion, mainly because the planes need to stay in the house and the missus wouldn't appreciate oil in the carpets!To do that, I'm considering the Hobbyking G46 motor, but still trying to understand how to select the correct setup. More googling required... Quote Link to comment Share on other sites More sharing options...
Former Member Posted August 31, 2018 Share Posted August 31, 2018 [This posting has been removed] Quote Link to comment Share on other sites More sharing options...
Denis Watkins Posted August 31, 2018 Share Posted August 31, 2018 Its all there on the Hobbyking spec David Battery: 4~5 Cell /14.4~18.5V RPM: 670kv Max current: 40A No load current: 10V/3.9A Current capacity: 55A/15sec Internal resistance: 0.04 ohm Weight: 303g (not including connectors) Diameter of shaft: 6mm Dimensions: 76x50mm Required; 60A ESC 4S~5S Li-Po / 12 ~ 16-cell Ni-MH/Ni-Cd 12x8 ~ 14x10 prop Suitable for sport and scale airplanes weighing 4 to 7 pounds (1.8–3.2 kg). Quote Link to comment Share on other sites More sharing options...
Engine Doctor Posted August 31, 2018 Share Posted August 31, 2018 Posted by supertigrefan on 31/08/2018 12:35:19: I reckon ?400 for one of these could be considered a bargain compared to the ?8.99 for 100 copies they retailed at! Wow £900 usually ! Im possibly thinking of the lower price they offer for the first edition or just out of touch. Probably the latter Quote Link to comment Share on other sites More sharing options...
David Wilson 25 Posted August 31, 2018 Author Share Posted August 31, 2018 Yes, but there are the 420, 550 & 670kV "flavours"...I understand that this is the RPM per volt of the unloaded motor, but how does it affects the flying characteristics of the plane?Does a lower kV rating mean bigger diameter props and/or more pitch? And conversely, higher kV needs a smaller prop and/or finer pitch?Up to now, it's been specified for me, so I just buy what's advised. This is a first... Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted August 31, 2018 Share Posted August 31, 2018 David, to save re-inventing the wheel, have a wade through this thread - there is some good information on the whys and wherefores of motor theory... Although electric motors are clean and efficient, without a reasonable understanding of the theory, most beginners find the subject pretty daunting. There is a free to download/try program called Motocalc which you may find very useful... Quote Link to comment Share on other sites More sharing options...
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