Prop Guru needed please!

[Toledodave]

  Ok I am having some trouble with my Scorpion Y-720 (Formaly y-650). Im using 6x Turnigy Aerodrive SK3 - 3530-1150kv and Mystery 40a controllers powered by 5300Mah 4s. I first used CF 11x5 props and notice everything getting hot (motors, wires, escs,  osd, and battery. After a short flight we could smell bandades and learned i burned up a motor. So after changing motors i spun the motors up to find it heating up again. After doing lil research I read the motors were good with 10x4.5 and so I tryed them to find they wouldnt lift the copter untill full throttle and FC couldnt spool fast enough at full throttle to maintain stable mode. So I sat back down and start checking for heat again and found two motors still warm and everything else good. I didnt think I made that drastic of change with props. Do you think I have another issue then props and what would you reccommend I try for props?   Or maybe im too heavy for some reason?

[steve fh]

Hi.

What does it weigh at take off ? 

Not sure what others think but your motors seem to be a very high KVA for 4S lipo

Might be you need to come down to lower pitch props as with 4S and 1150kva you are going to be spinning the props pretty fast

[guest325]

At that kv I think you should probably be running 8 x 4.5';s really you would have been much better off having 750-850kv then on 4S you could have run 10';s or 11';s. In this situation you really need to use a watt meter to findthe optimum prop size, tthen if you don';t get the performance you want you will have to change your motors!
I would be looking for motors rated at least 300W.

[Toledodave]

I tryed 10x4.5 and they wouldnt lift it. My 11x5.0 would but everything would get warm. 

If I order 6 new motors could I use these I have for just a tri-3 or just paper weights?

Also I dont know correct means to weight this thing but Im sure its on heavy side with Osd and fpv equipment on it. I was hoping the 6 motors could carry without too much trouble. I overwhelmed myself choosing motors and more or less made the best to my knowledge uneducated guess lol.   As far as going for payload and 40amp esc 4s battery could you suggest a motor that would best suit my needs by chance ? Theres so many lol Multistar 16 pole?  Heck...I really dont know what I need thought I had a grip on this lol

  If you think the motors I have would work, I have a Talon v1 tri frame waiting for escs and motors. Havnt odered them yet.

[guest325]

They would probably be OK for that model but you only really need 30A esc';s but if you do use the 40A';s you should never have an overheat problem - try them with 8 x 4.5';s first then you might be able to go up to 9';s OK - what you need to consider when choosing motors for this sort of thing is the power to weight ratio you need; on fixed wing I go for 150 Watts/Pound weight to give a reasonable sporty performance - anything more needed as regards performance 200 Watts per pound should give you unlimited vertical. With Quads I think it looks like you need AT LEAST 200 Watts per pound because if you look at it logically you are asking for unlimited vertical!

[Toledodave]

Hmm... good call. Clearly I didnt order the right Esc';s. Not sure how that happened.  Im sorry im still not clear on this. You reccomend 8x4.5 or 9x.4.5 props. But my 11x5.0 would lift but the 10x4.5 did not lift.  But you think 8x4.5 or 9x4.5 will?  The motors I have are rated for 330w (power)  im starting to worry its just a weight problem.   I do appreciate your help. You guys are my only resources. Im not far away from hanging this thing on the wall! Lol  were lacking coat racks anyway! Lol

[Toledodave]

Just a quick pic for ya so you can see what im dealing with. :)  thank you again for the help.

[barneyg]

Just stick it on your kitchen scales with the battery in place.  That is,you All Up Weight.  You need that before anything else will make sense.

Goto http://www.ecalc.ch/indexcalc.htm it will help work out what you need

[guest325]

Your batteries are a sizeable chunk at 500gm (approx.) each - there';s your first 1.1 pounds, as Barneyg says check your total weight and all will be clear!
I wouldn';t expect smaller props to lift your model if the bigger ones struggle, this seems to suggest that you are well under powered for the weight of your model.

[Toledodave]

Ok I used the bathroom scale. It states after several attempts it weighs in at 6. Lbs (U.S Pounds) 2721.55 grams.  Am I in trouble?

[Balders]

Have you throttle calibrated your esc';s out of interested?

Just for what it';s worth, I run 4S on my big hexa with multistar 690kv motors swinging 11x4.7 gemfan props, that flies around at 6.5kg';s without a problem (about 14lb) Motors are 16amps bursting to 22amps which is around 320W.

I would certainly think about lower KV motors if you have the budget, or shed a load of weight.

[Toledodave]

I never new I could use the term budget in this hobbie lol.

Yes I have throttle calibrated all the escs manualy not with a programming card. Had no problems other then the time it takes :)
  I have no problem getting new motors if thats my best option. Just dont know what I want or need. I understand the low Kv now but where should I draw the line? I see a large range of Kv motors. From 600-2500 kv.  Also I have 40a escs. I would have put money on a bet that the motors at time of ordering stated they pulled 32 or 34 amps. So I chose 40a esc';s. Multistars look nice and low profile. Is that something I should consisder and how many poles?

[Toledodave]

    ok What about these? Would this be more like what i need?
http://www.hobbyking.com/hobbyking/store/__41485__Turnigy_5017_620kv_Brushless_Multi_Rotor_Motor.html

So i can still utilize my 40a Esc';s?

[Balders]

They don';t look too bad, but the ones I bought are only $6 more per unit and have more power and personally I can vouch for them...done over 90 flights documented (and a lot more undocumented) with no issues, although when I got them I did re-make all the bullet connectors trying to trace a problem (that I eventually traced to a sliced wire and failing esc).

Also, just to check, I assume your esc';s can take 4S ok?  A lot of esc';s I looked at were 3S only, although as you';ve already run 4S on them I';m sure you are ok.

[Toledodave]

Balders first off thankyou for the info. I will be odering those exact motors you have and do you think new Esc';s are needed?  Mine are stock flashed Mysterys 40a sbec 2-6 cell lipo. Overkill I think but already installed and mounted :/   I will need to recalibrate esc';s to new motors anyway wont I?

[Balders]

no, esc calibration is totally seperate from motor, so no need for that. My esc';s are flashed 40amp opto';s from rctimer, so effectively you have the same power plant as me :)

I';ve run mine on cheap 12" props from hobbyking and it was fine with those, although at high weight lifting, I think they were just a little too "soft". I now run much stiffer gemfans, although they are not carbon.

[Toledodave]

Sounds good. I odered those 6 motors you have and a set of Cf 12x4.5s. Hopefully that will fix me.

[flybywire]

Just checking, you';re using cw& ccw props yeah?

[Toledodave]

Yep I sure am. I did notice an error on my part. My lower props were upside down putting the blade cup facing up. I had pitch and rotation correct but not the cup. I did get my new props and motors but waiting for some mounts to be here anyday and hopefully get this thing back in the air soon :)

[Toledodave]

Balders, you are the best!  Got in the air tonight. I have lift off at 3/8 the throttle. Sounds good and motor temps were all about 80f-100F.  I was a nervous wreck lol. Just remained in stablized while tuning trims and got brave and was hovering around the yard until....I panicked and managed to bring it back on my side of the house lol couldn';t wait to land and catch my breathe and forgot to save the trims lol.  Charging now and going to try to get another flight before dark. Thanks again for all your help and advise. Works like a champ!