bear with me...

[Yorkman]

but I'm a 'heavy' and if I can't fix something with a hammer then I tend to struggle....

you may remember my 'nicad to lipo upgrade' thread from a few days ago, about the issues of running speed 400 motors on a 3s lipo pack-well. my cunning plan, having upgraded from my trusty JR Propo Core (1985 vintage!) to an all singing and dancing computer 2.4ghz spektrum-is to simply reduce the 'WOT' position by using the 'servo travel' adjustment on the transmitter, so that the static thrust measurement (I don't own a fancy wattmeter, but do have kitchen scales!) is the same as produced by the old nicad packs.

Well, it seems to work-winding down the throttle travel from 100% to 40% reduces the static thrust to previously seen levels, and the motors run correspondingly cooler.

Finally, to the question...

One of the suggestions for reducing current draw was to change to smaller dia/pitch props-but would I be correct in assuming that if I did that, I would simply have to compensate by increasing the volts and current draw would remain the same? In fact-are 'current draw' and 'static thrust' essentially measuring the same thing?

And....if running at this reduced power setting-does that also mean the speed controllers are handling less amps?

Cheers in advance

Martin

[winchweight]

Certainly running at a lower power setting reduces the amps drawn, as the work being done is less.

[Frank Skilbeck]

The reason the 400's struggle on a 3s lipo is that the volts are typically higher than a good old 6 or even 8 cell Nicad, so the 400 will spin a lot faster, the power drawn on a given prop is roughly the square of the speed, i.e. twice the speed 4 x the power, so if you doubled the voltage then the amps would also double.

If you put a smaller prop on then the motor will still spin faster but need less power to spin the prop at this speed so the amps will come down.

Beware of reducing the WOT setting in the travel adjust on the Tx, some ESC's autosense where full throttle is so dialing it down this way might result in the ESC setting 100% when throttle is at 40%.

You'd be far better just throttling back when in flight, you then have the option of overpower for brief durations if required.

I've got a twinstar running on the original 400's with a 3s lipo and use full power for take off on the UC I've fitted and then throttle back. The motors may burn out eventually and then I'll replace them with some the new brushed lipo specific 400's that Puffin Models are stocking.

 One thing to watch if you are running the Grunther push on props is that the extra power can cause them to come loose and fly off , I had to put some proper prop adaptors on mine.

Next I'm off to try my Twin Jet on 3s on it's 480 motors, should be fun. 

[Yorkman]

Thanks Frank.

I've got a u/c on my twinstar too.....

I'm aware of the possibility of the esc reverting to 'full' but I think as long as i don't switch the model on with throttle set to full (after 'teaching' the esc where 100% is) the esc will continue  to just think it's got 75% (or whatever) throttle on the stick-essentially, all one is doing with the 'throttle travel' adjustment is putting an electronic 'gate' on the stick movement-as i understand it?

[Yorkman]

 and then I'll replace them with some the new brushed lipo specific 400's that Puffin Models are stocking

or aren't, in fact....

[Frank Skilbeck]

or aren't, in fact....

That's surprising I thought there would be a good demand for these. Don't forget you might need to add some nose weight to your twin star, I'm using a 3250 mah 3S and needed some extra nose weight. 

[Yorkman]

actually not the twinstar being discussed here, Frank, but the York.

thanks for the heads-up tho