Ben B

David and Tim- thank you for the suggestion, a very good idea, I will give Mr Puffin a ring and ask. I also do usually over-spec my motors, ESCs and batteries but it does appear that when people are heading into the upper limits of performance the ratings get ignored when it comes to the motor. I should imagine anyone over-rating a motor would keep an eye on the amps to make sure their ESC is up to it, ditto the batteries. There's no real reason to push an ESC when you can easily get ones which will handle 100s of amps. With motors it's a bit trickier.Presumably the rating of brushless motors is mostly to do with heat production so a motor with heatsinks and good cooling (and a cooler ambient temperature) will tolerate an over-current better than a "bare" can with poor cooling. Perhaps it's time to invest in some motor temperature telemetry equipment so I can keep an eye on it (seems a sensible precaution perhaps given the price of a good motor). From what I've read up on the subject, as the heat gets hotter, the magnets become weaker. This decreases efficiency and increases current draw etc etc. You get a viscous cycle after a certain point resulting in thermal runaway. What I'm also interested in researching is the various efficiencies of different ESCs- I believe some of this is just down to some ESCs having crude timing adjustments but clearly there's more to it than that (FET resistance for example). Thanks for all the input. I'll give John a ring as part of my research.

Do Mega motors give very conservative ampages? They don't seem to be rated very high yet I know that people run them at crazily high ampages without undue effect.... On my Turnigy inrunner I worry that even getting near the max ampage is pushing it, people seem to run mega motors at 2-3 times the max rating.  Alternatively, does anyone know of a short(ish) high kV 28mm inrunner? At the moment I'm running a 2700kv 2835 inrunner at 35A (ish). But I want more power!       

Here are my choices 1) Stringbag Swordfish2) Bristol Beaufighter3) Mosquito 

Yes, I am worried that I'm flogging the preverbial trying to get my Zagi to go faster because it has quite a thick wing section so I'm not sure really how fast it's going to go. But it went a lot quicker when I went from 80W to 240W so it should go a bit faster when I give it more like 400W (my current aim). If I had known when I built the plane that it was going to go as fast as I now want it to I would have sanded off the moulding bumps and put a CF spar in it... Oh well! Nothing like a little destruction testing!

sorry meant "and therefore lower wattage" in the last post

I've tried looking up the specs and can't find a wattage.....It does say max amps 32A and max voltage 12v but it doesn't say whether you can both at the same time ie the max amps might be at a lower voltage (and therefore lower ampage).   Good point re using a partially empty pack. Once I've got my new collets I'll try again on a partially empty pack and try again and see if it gives a difference.

Doh! Got the readings with the new prop on saved on the digicam and went to swap props and my only 3.2mm collet adaptor jammed on the shaft and trying to get it off I recked the soft ali collet looks like it's no readings on the smaller prop until Monday now when I can get a new one..... 22.6A 10.93v 247.0W on a fresh pack on the 6.5 * 5.5  btw....

Thanks for the info, I'll try swapping back to the old ESC and see if it makes any difference and have a look at the programming card and see what seeings the two are on....

Dear all, I wonder if I can get the collective's opinion on my dilema. Last year I finally moved into the 21st century and ripped out the old speed 400 and NiMh packs in my Zagi and fitted a Turnigy 2200kv 2835 inrunner on a 5.5*4.5 APC E prop, running 3S 2200maH 20C turnigy lipos. My watt meter shows the setup pulling 22-23A static. It transformed the plane- really great.  But time moves on and I wanted more speed and more thrust so I swapped the turnigy basic 25A ESC (which I must admit handled the 23A impressively- not even warm after flying) for a plush 40A ESC and swapped the prop for a 6.5*5.5 APC E prop again on the 3S battery. I was foolishly thinking going up one size on the pitch and also one on the diameter would push up the watts quite a bit.  I've just test run it and static testing shows it's still pulling 23A and the wattage is about the same . It's blowing a gale so I haven't had time to fly it but I was expecting a big an increase in ampage after hearing how sensitive motors can be to prop changes. I can only assume that the motor is seriously under-propped so it's reaching its 2200*11 rpm limit on both props?? How does that sounds as a hypothesis? Or maybe my 20C 2200mah cells don't want to "give" more than 23A. I'm not sure whether the best option is to just fit a much higher kV motor, this prop is about as big as cut-out at the rear of the 480si will handle and the battery bay doesn't really have space for 4S. Opinions appreciated