Pinion for extended flight times

[Cralis]

I'm trying to work out which pinion would be used for someone with a stock (1100 engine) EP550, who wanted extended flight times, and the most exciting moves they were doing was maybe a stall turn? The more teeth, the longer the flight?

[kgfly]

More teeth = higher headspeed = more power = shorter flight

Not sure which pinion you need but ReadyHeli have a useful headspeed calculator for H550 here: http://www.readyheli.com/Online_Headspeed_Calculator_s/81.htm

Around 1800rpm will give you tame performance and longer flights.

[erbrou]

Around 1800rpm will give you tame performance and longer flights. One thing I would like to know... When you suggest 1800rpm, is that headspeed at 100% (full throttle) or, I dunno, 90%? Because a lot of people do not run the motor at 100%.

I received a 15T pinion with my kit, I was also wondering which pinion to use for long flight time with stock gears and the Z20 980kV motor.

[kgfly]

Many factors contribute to the headspeed outcome including:

* gear ratio
* motor KV (actual for your motor which will vary from the nominal value)
* battery spec and performance (voltage under load)
* throttle setting
* blade and paddle airfoils
* temperature

Your choice of gear ratio, motor and battery are the primary factors. You can tune your headpseed by adjusting your throttle curve to suit. Brushless ESCs and motors are inefficient at low throttle settings and the guideline is to generally operate above 85% most of the time. Of course many folk run lower curves than that but it is sub-optimal.

My own choice for estimating headspeed is to assume:

100% throttle
10% losses
3.5V/cell for lipo, 2.8V/cell for A123

[Mikej]

This is really usefull stuff guys - I am still learning (lazy eights plus early FF), currently running a 14 tooth pinion on standard motor (890 KV ??) using 500mm blades. My throttle curve is 0, 41, 82, 82, 82, 82 and my heli hovers very nicely at half stick, but the motor does get pretty hot after a 6 minute flight.

However if possible I'd like to tame it down ever further - would I get longer flights with a 13 tooth pinion (I have just ordered one from Readyheli) ?? - from what I have read the motor would run cooler and longer if I raised the revs - hence the new pinion - is this reasonable thinking or have I mis-understood ??.

Thanks,

Mike.

[bstock]

Mike - you are on the right track.

Ken KNOWS what he talking about... and his advise is straight on. Brushless motors prefer (are more efficent) to run at 85% or more... so by lowering your pinion... you can increase the motor to 85% or more... and it should run more efficently and cooler.

You are going to lower your HS with the 13t... and many sport flyers like a HS of 1800... but I'll bet you like the 13t over a 14t... with the higher throttle curve and a better running motor.

You should have longer flight times with the 13t... and even if you are slightly lower in the HS... it sounds like it will be OK with your style of flying. (check out readyheli's HS calculator to see what HS you will get. Use the 90% drag figure... that is more realistic to the real world)

Let us know what you think after trying it!! I for one would like to know.

[Mikej]

Thanks bstock - I'll give it a try when it arrives