RPM from Hacker 14XL
Gents,
I have found myself a little disappointed with the powered delivered from my setup and am interested in understanding any thoughts on improvement. Let me explain where I am at:
Setup: Integral with Hacker C50 14XL Comp (4 degrees), Spin 99, APC 20x15e, Hyperion 16C 5350mah
Reading on ground (max throttle, fresh charge): 34.7V, 59A, 2050W, 5600RPM
Reading in air (max throttle, average of top 30 amp draw in 3 flights): 34.8V, 57.6A, 2000W, 5683RPM
I tried serveral other packs to check out battery performance as I thought ~3.5 V/cell was low and found that Zippy and Thunder Power gave approximately the same readings, ie. 3.4-3.5 V/cell. I looked back at other packs that I use in a TRex 600, (Flight Power and Hyperion) finding that ~3.4 V/cell was the result achieved here as well. My conclusion from this is that, under load, I can expect to achieve around 34-35 Volts from a 10S pack.
Extrapolating this out from this voltage I concluded that the maximum RPM I would expect would be 34.5 (Volts) x 1100 (KV) / 6.7 (gearing) = 5664 RPM (regardless of the prop used). So that fact that I am getting 5600 RPM means that this is as good as it gets in terms of RPM from the motor (ie. it won't draw more current) and the only way I can draw more amps is to put on a heavier prop.
So, I'm currently using a 20x15, will a 21x14 put more load on the 14XL motor? Are there any other options to deliver more watts overall with these components? Any thoughts? I would like to be able to pull an extra 500watts or so as this would oversome some weakness towards the ends of a couple of a couple of manouvres.
Simon
PS. As a comparison, the other guys with electrics I was with over the weekend had outrunners which were drawing up to 80amps at full noise (at around 34.5V) and a much higher RPM with a similar prop, this makes sense because their KV's were (approx) 230KV and therefore their max theoretical RPM is around 8000 at this voltage, hence their motor will draw more current on the same prop. To be honest, I hadn't thought about this much before and it did surprise me somewhat. I'm thinking that I would be better off with a higher KV motor in the inrunner style which would allow me to draw more power.