DIGGER Posted October 16, 2021 Share Posted October 16, 2021 I have a CESSNA O-1 BIRDDOG and I want to get an electric motor for it but not sure of size, kv, prop size,etc it's a high wing observation plane so want to fly scale speed. But I need the power to lift off on a short rough runway. It has flaps which will help getting airborne. Now measurements. WS 57.5 inch ( 1460.5 mm ) LENGTH 41 inch ( 1041.4mm ) WEIGHT 1 KG ( 2.20 lb ) this is compleat, servos, RX . included. Not worried about weight of motor and ecs as its a short nose plane and will no doubt need weight in the nose to get c g .I would like to use 3c or 4c battery. Any help please. Quote Link to comment Share on other sites More sharing options...
Shaun Walsh Posted October 16, 2021 Share Posted October 16, 2021 What size prop do you want to use? Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted October 16, 2021 Share Posted October 16, 2021 (edited) Digger Is the 1 kg with or without the IC engine? If without how much did the IC (what size was it) plus tank etc weigh? This would then give a target to compare the electric weight and performance assuming you flew it with the IC. I would be a pity if you use extra weight as the battery will be a fair lump. It is just a case of getting it in the right place. This may require a bit of ingenuity to make the best use of the electrical installation. In general a more powerful electric motor than the minimum necessary adds little extra weight so there is no real penalty in having 'power to spare'. Just use the throttle and in so doing proportionally increase the flight duration.? Edited October 16, 2021 by Simon Chaddock Quote Link to comment Share on other sites More sharing options...
MattyB Posted October 16, 2021 Share Posted October 16, 2021 (edited) There is lots of good guidance in this thread in the Electric Flight for Beginners forum…. Edited October 16, 2021 by MattyB Quote Link to comment Share on other sites More sharing options...
DIGGER Posted October 17, 2021 Author Share Posted October 17, 2021 16 hours ago, Shaun Walsh said: What size prop do you want to use? I have some Apprentice ones and they are 11inch I think Quote Link to comment Share on other sites More sharing options...
DIGGER Posted October 17, 2021 Author Share Posted October 17, 2021 Simon . I wouldn't know about the ic motor as its made for electric motor. It was some big old can with about 10 nicad batteries. No size on it. Thanks MattyB I'll have to go through it. Quote Link to comment Share on other sites More sharing options...
EarlyBird Posted October 17, 2021 Share Posted October 17, 2021 (edited) I would guess it's a speed 600 probably 150-200 watts. Obviously the replacement brushless has to fit the space. Is it 36mm x 60mm? If so I would be thinking of a 3536 1000kv on 3S. Do you have any motors to try? Edited October 17, 2021 by EarlyBird 1 Quote Link to comment Share on other sites More sharing options...
MattyB Posted October 17, 2021 Share Posted October 17, 2021 2 hours ago, EarlyBird said: I would guess it's a speed 600 probably 150-200 watts. Obviously the replacement brushless has to fit the space. Is it 36mm x 60mm? If so I would be thinking of a 3536 1000kv on 3S. Do you have any motors to try? This is a very decent estimate IMO. If you look at the Durafly Tundra it’s specs are not dissimilar in terms of span and AUW, and it uses a 3636 900Kv and 40A ESC on a 12x6 prop and 3S pack. I suspect your model mat be a bit overpowered on that, but that’s easily fixed by propping down a smidge. Quote Link to comment Share on other sites More sharing options...
DIGGER Posted October 17, 2021 Author Share Posted October 17, 2021 4 hours ago, EarlyBird said: I would guess it's a speed 600 probably 150-200 watts. Obviously the replacement brushless has to fit the space. Is it 36mm x 60mm? If so I would be thinking of a 3536 1000kv on 3S. Do you have any motors to try? I have tried a 1000kv and a 1100kv but it was very underpowered, couldn't lift off. Quote Link to comment Share on other sites More sharing options...
DIGGER Posted October 17, 2021 Author Share Posted October 17, 2021 1 hour ago, MattyB said: This is a very decent estimate IMO. If you look at the Durafly Tundra it’s specs are not dissimilar in terms of span and AUW, and it uses a 3636 900Kv and 40A ESC on a 12x6 prop and 3S pack. I suspect your model mat be a bit overpowered on that, but that’s easily fixed by propping down a smidge. That sounds interesting, two of my friend's fly Tundra's I'll ask them if they have a spare motor I could try. Thanks. Quote Link to comment Share on other sites More sharing options...
Dickw Posted October 17, 2021 Share Posted October 17, 2021 14 minutes ago, DIGGER said: I have tried a 1000kv and a 1100kv but it was very underpowered, couldn't lift off. What size prop was this with and what battery were you using? Both can make a considerable difference to power output. Dick Quote Link to comment Share on other sites More sharing options...
Shaun Walsh Posted October 17, 2021 Share Posted October 17, 2021 One of these running on a 3s battery should be OK https://www.4-max.co.uk/po-3541-1070.html or this one on 4s or one of these on 4s https://www.4-max.co.uk/po-3541-810.html Quote Link to comment Share on other sites More sharing options...
DIGGER Posted October 17, 2021 Author Share Posted October 17, 2021 Thanks Shaun 4s one sounds good. Quote Link to comment Share on other sites More sharing options...
Shaun Walsh Posted October 17, 2021 Share Posted October 17, 2021 1 hour ago, DIGGER said: Thanks Shaun 4s one sounds good. The 3s motor is in my 1.5Kg Riot and gives vertical take off capability, overpowered for the Bird Dog but it should fly in a scale like manner on low throttle, alternatively a 3535 with a kV of 750-850 would probably give adequate power without the get-you-out-of-trouble capability of the larger motor. The larger motor should also swing a more scale size prop if that's important to you. 1 Quote Link to comment Share on other sites More sharing options...
MattyB Posted October 18, 2021 Share Posted October 18, 2021 (edited) On 17/10/2021 at 14:19, DIGGER said: I have tried a 1000kv and a 1100kv but it was very underpowered, couldn't lift off. You need to give us the full details of that powertrain before we can diagnose the issue for you - it sounds like something was badly wrong somewhere as a 1000Kv motor should be in the sweet spot on 3S with the right prop (perhaps the battery was end of life, or you'd fitted the wrong prop). I agree with @Shaun Walsh that there should be no need to go to 4S for thatmodel if you choose the right combination of motor, prop, battery and ESC. If you do go 4S make sure you choose the other components to match that - slam on the same prop and use the same ESC you would on 3S and you may find magic smoke escaping... Edited October 18, 2021 by MattyB Quote Link to comment Share on other sites More sharing options...
PatMc Posted October 18, 2021 Share Posted October 18, 2021 Has the ESC been calibrated with the Tx ? Quote Link to comment Share on other sites More sharing options...
gangster Posted October 19, 2021 Share Posted October 19, 2021 Couple of thoughts 4 max and Robot birds are very helpful and will advise If you are going to experiment with battery voltage and prop size you will need a meter that measures power and current in order to present exceeding max current on either esc or motor Finally if you do over power the motor you can control with the transmitter in the same way you would a servo. Set to 100% and calibrate rhe esc Then reduce the max throw to give the required power at max. You will still need to keep the prop size within a sensible range Quote Link to comment Share on other sites More sharing options...
MattyB Posted October 19, 2021 Share Posted October 19, 2021 4 hours ago, gangster said: …Finally if you do over power the motor you can control with the transmitter in the same way you would a servo. Set to 100% and calibrate rhe esc Then reduce the max throw to give the required power at max. You will still need to keep the prop size within a sensible range Sorry, but that is not particularly good advice, not for anything other than an e-glider (where power runs are generally very short) anyway. You should always configure your power train with a suitable battery and prop for the motor so that full throttle is at 100%, otherwise the ESC is doing a lot of additional work and is likely to experience a shorter life. 2 Quote Link to comment Share on other sites More sharing options...
DIGGER Posted October 20, 2021 Author Share Posted October 20, 2021 Thanks to all of you for your help, but I'm still confused, so I have spoken to George at 4max and put it in his hands. Thanks again. Shaun it will be interesting to see if he comes up with the same motors. Thanks again. Chris Quote Link to comment Share on other sites More sharing options...
gangster Posted October 20, 2021 Share Posted October 20, 2021 On 19/10/2021 at 08:11, MattyB said: Sorry, but that is not particularly good advice, not for anything other than an e-glider (where power runs are generally very short) anyway. You should always configure your power train with a suitable battery and prop for the motor so that full throttle is at 100%, otherwise the ESC is doing a lot of additional work and is likely to experience a shorter life. I can see where you are coming from MattyB. But unless you were pushing things to the limit ie trying to drop a significant amount of power or your esc was on the limit I would not anticipate too much problem . I tend to over engineer my power trains as I suspect the quoted “ max current figures “ of esc and motors are a tad ambitious and allow little room for error. Quote Link to comment Share on other sites More sharing options...
DIGGER Posted November 27, 2021 Author Share Posted November 27, 2021 Sorry people for the long delay with this. ( health problems ) I gave George at 4 max all the information and left it in his hands, and he came back with the right motor setup for this model. Shaun you got it right ,it's the PO-3541-1070 with a 11x7 prop , 40a ESC. Which has now arrived and waiting to be fitted. Thanks again, sorry for delay in update. Chris Quote Link to comment Share on other sites More sharing options...
EarlyBird Posted November 27, 2021 Share Posted November 27, 2021 Sounds good to me Chris. Is that on 3S? Please let us know how it all works out for you, just to complete the story. There's no rush as there's plenty of patience on this forum. Quote Link to comment Share on other sites More sharing options...
DIGGER Posted November 27, 2021 Author Share Posted November 27, 2021 Yes that is 3s. 1 Quote Link to comment Share on other sites More sharing options...
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