Paul Adams Posted September 3, 2013 Share Posted September 3, 2013 I calculated the torque required from each Servo using a Servo Torque Calculator (**LINK**) and taking the max air speed of 80 MPH and using the aerobatic flying throws calculates that you will require servo's with at least the following Torque values:- Elevator 2.6 Kg/cm Aileron 2.8 Kg/cm Rudder 5.5 Kg/cm If you set the throws greater than the aerobatic settings, the torque values will be even higher. Quote Link to comment Share on other sites More sharing options...
JimmyBH Posted September 3, 2013 Share Posted September 3, 2013 Thank you for the Servo stats.....the Rudder torque value is right at the upper limit of the servo used, thankfully the other stats are approximately half the load. I equipped the Yak with hitec hs-485hb deluxe all-round. I bought them a year and a half ago when I bought the model and engine. These servos would appear to have very mixed reviews! Some people swear by them, a lot of people have had multiple failures! Quote Link to comment Share on other sites More sharing options...
John Allen Posted March 7, 2014 Share Posted March 7, 2014 Well I've had the model for a while, and now I've got a choice of MVVS 26cc, or a new AGM 30cc (just bought it), I'm think the 26cc as the 30cc would be better for my 72" Giles. Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted March 7, 2014 Share Posted March 7, 2014 Posted by Paul Adams on 03/09/2013 18:59:21: I calculated the torque required from each Servo using a Servo Torque Calculator (**LINK**) and taking the max air speed of 80 MPH and using the aerobatic flying throws calculates that you will require servo's with at least the following Torque values:- Elevator 2.6 Kg/cm Aileron 2.8 Kg/cm Rudder 5.5 Kg/cm If you set the throws greater than the aerobatic settings, the torque values will be even higher. Your assumed airspeed may be a little conservative, Paul. I've fitted an ASI in mine and get a little over 80 mph in level flight at full throttle and have got it to 121 mph in a powered dive. A shallow dive will get it to 100 pretty quickly. That's since reverting to a 120 FS after some observations that the 180 was a bit loud for our site. Quote Link to comment Share on other sites More sharing options...
Paul Adams Posted March 9, 2014 Share Posted March 9, 2014 Hi Martin, I agree, but do you use full throws at full throttle in a dive? probably not. The maths show that If you use 72 % of the throw when at 120 mph, you would require the same servo torque (The maths behind the torque requirement shows that the torque is proportional to the speed but is a square of the amount of throw, so 100% throw at 80 mph gives the same torque requirement as 72% of the throw at 120 mph). There are other variables which also effect the torque. For example if you use less than 100% travel on your transmitter you need to increase the torque (70% travel requires more than double the torque). So best to keep the travels at 100% + and adjust the push rods to get the correct throw. As stated above, this is the minimum torque value and I would always use servo's with a bit of extra torque, just to be on the safe side. Quote Link to comment Share on other sites More sharing options...
Lee Smalley Posted March 10, 2014 Share Posted March 10, 2014 do not know where you get those figures from but if you fit servos to that model with them kg pulls you are gonna lose the model, in knife edge i had Hitec 5KG servos on each elevator and the elevators would wave at me on the way past, so i swapped them out for 12KG MG Alturns.....yes i had an ST 23 cc 2 stroke in mine, and i do throw her about but do not be such a tight bum, and fit servos to do her justice Quote Link to comment Share on other sites More sharing options...
John Allen Posted March 10, 2014 Share Posted March 10, 2014 I'm fitting http://www.hobbyking.com/hobbyking/store/__29505__Turnigy_1257TG_Digital_Titanium_Gear_Servo_57g_10_5kg_09sec_UK_Warehouse_.html on mine, with the 1256tg on the rudder. Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted March 11, 2014 Share Posted March 11, 2014 Posted by Lee Smalley on 10/03/2014 12:54:04: do not know where you get those figures from but if you fit servos to that model with them kg pulls you are gonna lose the model, in knife edge i had Hitec 5KG servos on each elevator and the elevators would wave at me on the way past, so i swapped them out for 12KG MG Alturns.....yes i had an ST 23 cc 2 stroke in mine, and i do throw her about but do not be such a tight bum, and fit servos to do her justice No problems noticed with 5kg digital elevator (and aileron) servos - and I was watching/listening very carefully when I was checking the maximum speed - but the rudder did benefit from upgrading to a 14kg one for knife edge manoeuvres. Quote Link to comment Share on other sites More sharing options...
John Allen Posted March 11, 2014 Share Posted March 11, 2014 The 1256tg are only 8.5kg, do you think thats enough Lee? Quote Link to comment Share on other sites More sharing options...
JimmyBH Posted March 11, 2014 Share Posted March 11, 2014 I too had servo failure on my second flight with this model last year, at the time I used Hitec HS-485HB and thankfully it was the rudder that failed and managed to get her back down safely. I am going to replace all the servos with Power HD High-Torque Servo 1501MG, very competitively priced and fingers crossed will now exceed the recommended torque requirements. Edited By JimmyBH on 11/03/2014 09:03:45 Quote Link to comment Share on other sites More sharing options...
Lee Smalley Posted March 11, 2014 Share Posted March 11, 2014 I do not know the servos Allen but 8.5kg will prob be ok, the rudder might need more but it depends what style of flying your doing, martin as you know digitals have better holding power than the analog units i was using, whilst i never suffered a failure it was obvious the servos were struggling during certain times so i swopped them out and my recommendation to everyone else is to do the same if you are giving it some rice Quote Link to comment Share on other sites More sharing options...
John Allen Posted March 11, 2014 Share Posted March 11, 2014 Ok, looks like I'll use the 8.5kg for the elevator, and 10.5kg for all other surfaces. Only .01 difference in the speed, and these are fast servos. Quote Link to comment Share on other sites More sharing options...
Steve Hargreaves - Moderator Posted March 11, 2014 Share Posted March 11, 2014 With all this servo torque being required then a pretty chunky power supply will be needed. I can't help thinking that 4 x AA cells wouldn't be much use here.... What sort of power sources are people using, or planning to use, in this model? Quote Link to comment Share on other sites More sharing options...
cymaz Posted March 11, 2014 Share Posted March 11, 2014 Got to be 6v, really Quote Link to comment Share on other sites More sharing options...
Lee Smalley Posted March 11, 2014 Share Posted March 11, 2014 keep in mind i was using analogue servos, i used a 6volt 2200mah eneloop pack with an Ar7000 rx and i never missed a beat throttle HS 301 ailerons HS 485HB rudder HS645mg elevators Alturn 750mg if i was using Digis i would have gone to a LiFe pack Quote Link to comment Share on other sites More sharing options...
John Allen Posted March 11, 2014 Share Posted March 11, 2014 I'm using **LINK** for everything (unless they don't fit, then I'll use a smaller one) Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted March 11, 2014 Share Posted March 11, 2014 Admittedly, I've only had one example as an EDF power pack but I'm afraid it's performed far worse than my cheap Hobby Store Dynamics - the cell voltages drop far more under load after roughly equal usage. My Yak uses paralleled 1100 maH LiFe packs. via individual switches/power leads. Edited By Martin Harris on 11/03/2014 19:17:05 Quote Link to comment Share on other sites More sharing options...
John Allen Posted June 4, 2014 Share Posted June 4, 2014 To everyone flying this bird on a DLE20, do you feel is has enough power, does it easily pull out of a hover, unlimited verticle etc... Would you opt for a 26/30cc given the choice? Quote Link to comment Share on other sites More sharing options...
Steve Hargreaves - Moderator Posted June 4, 2014 Share Posted June 4, 2014 Good question John.....I've wondered if a NGH38cc 4 stroke petrol might work in the Yak......might be a bit big & heavy though.... Quote Link to comment Share on other sites More sharing options...
John Allen Posted June 4, 2014 Share Posted June 4, 2014 Well I have an MVVS 26cc for it, but it seems rather large, also have a new AGM 30cc. There have been a few forum posts elsewhere suggesting you need at least a 26cc, and preferably a 30cc for good 3D, and then others suggesting it comes down like a brick with a 30cc motor, but needs a ton of lead upfront with a 20cc. Damned confusing if you ask me. The manual says 20cc petrol, but if a 26/30cc fits and reduces the need for nose weight, then why not have the extra power. Edited By John Allen on 04/06/2014 23:25:07 Quote Link to comment Share on other sites More sharing options...
john stones 1 - Moderator Posted June 5, 2014 Share Posted June 5, 2014 I flew mine on an O.S. 120 fs John, it flew great. It didn't have unlimited vertical nor power to pull out of hover easily. I don't think a 20 petrol will either. I don't know the weights for your engine choices, but moving the battery's back will help you balance without using lead. Fit a lite ply floor in rear of fuselage if needed to locate them. I used no lead in mine it balanced with the battery's fixed to engine box. John Quote Link to comment Share on other sites More sharing options...
John Allen Posted June 5, 2014 Share Posted June 5, 2014 Thats great info, I'll stick with the MMVS G26, or the AGM 30 so Quote Link to comment Share on other sites More sharing options...
Lee Smalley Posted June 5, 2014 Share Posted June 5, 2014 weight start to become your enemy now the MVVS is 1.1Kg the DLE 20 is 820g i am not sure the performance increase will make up for the extra weight and the wing loading will only get higher and mine with a 1kilo lump of super tigre up front would be as much weight as i think the airframe could cope with and still fly nice, i have had two and if i was going to have another i would put a cooking 120 or 150 2 stroke in .... moki 150 ooohhh! Quote Link to comment Share on other sites More sharing options...
iqon Posted June 5, 2014 Share Posted June 5, 2014 had a moki 135 (22.5cc )in mine flew ok, , with no lead.. Quote Link to comment Share on other sites More sharing options...
JimmyBH Posted June 5, 2014 Share Posted June 5, 2014 Got a DLE20 in mine, no additional ballast applied....I am not the type of Pilot who will be doing any sort of major aerobatics so for me there is plenty of power....and fun! Quote Link to comment Share on other sites More sharing options...
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