MRMels Head Speed Calc

[PorscheBoy]

Guys,

Looking at MRMels headspeed calculator it reckons my Stock 550e DFC would have a head speed at hover of 2824rpm! So when I go idle up this figure will increase!! This seems a high figure for a 550e DFC?

I have inputted my battery type as 40c with 6 cells (I use Align 5200mAh 40c Flight packs), stock maingear as 112 and stock pinion as 11, my stock motor is 1220KV and I have estimated 90% efficiency. A while back I ran my Helitac app I got 2180rpm at hover, although I have increased this to what I reckon is closer to 2300rpm.

What should be the target (I guess I could work it out if I knew motor RPM) and which do you think is correct?

Cheers

[tomatwalden]

Yeah, I get confused with Mr Mels calculator too. My Goblin 6S, 30C, 165main gear, 18T pinion, 90% efficiency, 1200Kv motor gives ....

(calculated for 100% throttle curve)
Hover RPM at beginning of flight: 3085
Hover RPM at middle of flight: 2841
Hover RPM at end of flight: 2742

I'm pretty certain that's not right either ... ????

[milly0812]

MRMels Head Speed Calc

But you are not going to be flying @ 100 % throttle irl . Most use gov in IU and have throttle curve between say 65 and 70%

[tomatwalden]

I'm not using a governor at mo, but my IU1 is set to 85%. So, that would mean that my HS = 85% of Hover RPM at middle of flight: 2841 = 2414 ?

[PorscheBoy]

But you are not going to be flying @ 100 % throttle irl . Most use gov in IU and have throttle curve between say 65 and 70%

Yeah, but the bit that confused me is that it says at hover these are the speeds. I run idle up at 98% flatline, surely it doesn't think that hover is done at 90% of 100% therefore my idle up would be another 8% up?

[milly0812]

MRMels Head Speed Calc

So reduce your flatline mate and the headspeed will be lower

[bulnose]

I'm not using a governor at mo, but my IU1 is set to 85%. So, that would mean that my HS = 85% of Hover RPM at middle of flight: 2841 = 2414 ?

the spartan doesnt have an electric gov .?

[milly0812]

MRMels Head Speed Calc

Yeah, but the bit that confused me is that it says at hover these are the speeds. I run idle up at 98% flatline, surely it doesn't think that hover is done at 90% of 100% therefore my idle up would be another 8% up?

Your making my brain hurt lmao

[RcRotaryMadness]

I do HS calculations manually... I work out what the maximum RPM of the setup could be at 100% throttle with a given main gear/pinion/motor/lipo/90% effic etc. I then take 85% of that as my governor setting... if that number isnt the HS i want at 85% throttle then I increase or decrease the pinion size until I get my HS at 85% throttle. This allows the governor 15% of headroom which has never let me down yet.

Personally i think this method is better than using pure throttle control to manage HS, I've seen helis setup at like 60% throttle because the pinion they'd got on it was way out. This overworks the ESC and then they wonder why it goes up in smoke.

Edit: Similar theory applies to throttle curves too.. get the Mid stick/hover throttle curve to 85%, then the rest of the curve to compensate for the load fluctuation.

Also I prefer my hovering setup so that HS stays constant even at bottom stick... I only have it set to change the pitch curve and the throttle curve stays CONSTANT. with only the pitch curve making adjustments to the rotor disk the heli is much more controllable imo.