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[tonyH]

Hi All,

Can anyone recommend suitable non-linear (logarithmic?) speed controllers suitable for driving 7.2-9.6 volts at a nominal max of 10 amps.  Motors are Buhler 7 pole geared down by approx 2.4/1 so the current is guessed on the high side. Low speed control is paramount.

Thanks

Tony

[Shipmate60]

Any ESC that advertises "Soft Start"

Bob

[tonyH]

Thanks for that Bob,

I'm looking for the soft start to extend to about 50% of stick movement. Is it likely that would be the remit of the soft start type?

I'm expecting problems because the hull form is very long and narrow with what we expect to be 'strange' handling (especially no brakes) and we're trying to find what the limits of control are at the 'docking' sorts of speed. The original vessel had reciprocating steam engines and we're trying to reproduce the sort of control that those would have.

Tony

[Mankster]

May be dialing in some negative exponential in the transmitter would work?

[Shipmate60]

Tony,
The No Brakes intrigues me as most marine ESC's have the reverse facility which would give you some "brakes".
A well selected ESC/Motor combination should give good slow running characteristics.
Naval Hulls are traditionally long and narrow with up to a 12:1 length to beam ratio. subs possibly more and can handle linear power well.
It will of course depend on your prop or propulsion system.
A few more facts would be helpful.

Bob

[stallspeed]

...(logarithmic?)...

Tony,you probably sussed you meant exponential but motor power increases almost by the square if the throttle is proportional.

A fully proportional electronic controller operating at a frequency of greater than 700 Hz,with two dozen or more discrete steps, should allow consistent low end response if you trim the controller's maximum power to the full stick travel.
That gives fine crisp throttle response with high speed 380,540 motors right up to golf cart motors where you should be able to throttle back or start an uncoupled motor at a few revs per second.

Additional soft starting would be a performance reducing gimmick.It is needed in some circumstances to prevent damage to gears and drive train.It is redundant with small permanent magnet motors,especially where you have a water immersed prop.

[FullLeatherJacket]

http://www.action-electronics.co.uk/pdfs/P80.pdf
P80S should do the job.
FLJ

[tonyH]

Thanks All,

FLJ, can you advise on the take up curve on the P80S?

I realise this may all be a bit on the twee side but the Arquebuse has the props behind the rudder (and the props overlap each other) and the handling is likely to be a bit strange so we're going for maximum low-speed control to see where the 'long, pointy thing' comes into it's own.

Tony

[FullLeatherJacket]

You'd need to check it against the motor, as the response can vary quite a bit with different motors. PM me and we can arrange a SOR deal if you like.
FLJ

[tonyH]

Thanks FLJ,

I'm just finishing the hull at the moment and I've got a beautiful, scale, running gear set from George Sitek and the motors so I've just got to get the reduction pulleys/belts to suit. Once I've got those I can try a full load test to see the draw and I'll be in touch.

Are the ESC stock items or what is the normal lead time?

Jimmy James and I are hoping to carry out trials at Eaton Park at the end of the month.

Regards

Tony

[FullLeatherJacket]

Are the ESC stock items or what is the normal lead time?

If we don't have one in stock then we make one there and then. One of the many benefits of not just importing crud from the ROC and sticking a pretty-coloured label on it.
As it happens we have three in stock, so there is no lead time.
FLJ