Hi I'm experimenting with a pair of 6s batteries and 40A esc's Question is this - Esc's come with short leads so is it best to solder the power inputs to the esc directly onto the PDP, then since my motor wires are short extend each motors 3 wires of equal length and also same length for the other motors too to reach the esc's OR place the esc's near the motors (since the motor wires are short) and run only the esc power wires through the booms to the PDB? Lol, I forgot the esc control wire (that goes to the FC) will also need extending... So which option is better? Least work is also better but not necessarily right. Looking to you experts to shed some light Best
You cannot have too long wires from the battery source to the esc. From the ESC to the motor is fine. You have to use this if you want to extend the power wires. http://www.castlecreations.com/products/cc-cap-pack.html Bill
I've wondered about this. It seems that you could take advantage of the prop wash on a MR to cool the ESCs if you placed them on the booms directly next to the motor under the props. Is there a reason (electrically-speaking) that this won't work?
Adding wire also adds inductance, which can increase the ripple voltage in a system. Ripple voltage peaks should always be less than 10% of the total pack voltage; the smaller the ripple voltage the better. CC Capacitors are useful in all brushless motor applications, where it serves to give just that little boost needed to overcome ripples in the battery voltage caused by hard acceleration or long battery wires. Remember, ripple voltage is hard on an ESC, Does this help? Bill
Well, I totally trust the EE types. I'm not questioning it at all. I figured there was a good reason. But I wonder if that can be overcome in some way, as there would be a huge benefit IMHO if the ESCs could be cooled by the prop wash.
Well I agree with you the ESC's will stay cooler under the prop wash, but, they have to be placed about 6" from the motor right under the tip of the prop. Bill
Is not much air flow next to the motor. The tip of the prop creates the lift. As the prop turns the air is directed towards the tip of the prop. Now I could be wrong, but that's my theory. the cylinder of air flowing through the prop doesn't go straight back, but rotates as well It cuts the air like ribbons. Propwash or spiraling slipstream is the white corkscrew-like vapor coming off the tip of a propeller of an airplane. Bill
That sounds interesting, and plausible. But the shape of my props (APC "MR" models) looks an awful lot like they're pushing a lot of air in close to the hubs...quite a bit different than the Herc’s props.
hehehehehe you are hard to convince. I'll say it again the air flow moves from the hub to the tip of the prop then out. The only prop design that pushes air from the center is the ones found on oscillating fans, but try to fly with those. Bill
Firstly I would like to thank you all for joining in and posting on here. 8" will not suffice therefore I guess I'll have to put the esc's closer to the PDB. It would have been nice however to have the esc's cool under the prop wash. Anyways, such is life. I'm thinking about removing the 3.5mm bullet connectors off of the motor wires and perhaps doing a combination of crimp and solder then shrink wrapping each wire individually. The other end of the extended motor extention wires I'm planning to use the same bullet connectors (that came off of the motor wires) to connect the now extended wires to the esc motor control end (which also have the 3.5mm connectors (but in the case of the esc end are female- which is great) this way I at least have one place I have to remove the booms (plug and play) to knock down for future transportation etc...watdya think? I however would have liked to again crimp and solder here as well, any suggestions on having both??? Hahah My next question is about the esc, themselves. One side of the esc is flat (this possibly being the heat sink as well as the circuit board.) It would be nice to have the flat side down onto the esc mounting plate with a strip of foam at both ends of the esc. This could serve 2 purposes, one being - minimising vibration on the esc and, two having some airflow between the flat side of the esc and it's mounting plate. What do you fellas think? Lol I'm being as clear in my questions so as to allow future readers or new members to follow in case they want to achieve something similar. My contribution here is in sharing the questions too, hahah, as without questions there will never be answers.
My understanding was that the most thrust comes from about 75% along the length of the blade from the hub. That's not to say that there is no thrust from close to the hub but it's not the maximum. From the point of view of cooling the ESC/BL-Ctrl, it might take some testing to see if there is *enough* airflow out by the prop tips (which would keep the motor wires a bit shorter), or out by the motors. The LiPo DC supply out to the ESCs would create some interesting magnetic fields.... Bill: Aren't those white helical lines caused by the rapid pressure drop caused by prop tip vortices suddenly causing moisture to condense of the air? The tips vortices being caused by the air from the front of the blade curling around to interact with the air behind the prop blade tip pretty much like wing-tip vortices? Andy.
I was wondering how long it will take before you post something. LOL Hello Andy. Well had you seen a tornado or a hurricane? The center of both of those events is quite but the outer edge is turbulence. The wingtip-vortices don't create lift they reduce drag. If you notice some props (like the Herc) are square at the tips and the props we use have a point the reason for that is because the Herc props have variable pitch and the multirotor props are fixed. Bring it on.... Bill
propellor twist and changes in chord length try to account for the variation in speed across the diameter of the prop, within the limitations of the angle of attack of the prop with the relative airflow. Ideally there would be a nice even distribution of lift/thrust across the prop, but because they spin is circles its not possible. Fixed pitch props are most efficient at one speed. Variable pitch props have better efficiency across a range of speeds ... Prop tips end in a feathered shape for efficiency reasons, and J model hercules have curved and tapered prop blades, once a prop tip approaches the speed of sound the drag increases significantly on the prop tip, then the maths all gets screwed up this all brings back nightmares from Uni days .....
I think Bill answered your question in his post #2 above. As for soldering directly to the board, most of us use small pigtails and bullet connectors. You can't solder and unsolder too many times before you might have issues with the PDP.
I read on DIY drones somewhere that lengthening the motor wires must be done with care and they must be exactly the same length. Otherwise the impedence of the windings is affected causing....Grief? By the way Steve, I just love your hat. I want one too!
No, The length of the wire has nothing to do with it. The difference is in the winding. The impedance will change IF the number of windings around the pole change, The number of poles and the thickness of the wire. Eg. the difference between a quad, a hexa and a octo the motor wires are different lengths. 3 motors one 420KV 14pole 33mohms resistance Motor 2 400KV 14pole 116mohms resistance. Motor 3 700kv 14pole 50mohms resistance. The difference is in the windings, how many turns and how thick the wire is. Bill