Roughly speaking it seems that one horsepower per inch of dredge diameter is required when using gasoline engines to run the pump.
Since a horsepower is 750 watts, that's the same as 750 watts per inch.
but that's the power we put in, not the amount of work done.
So if that gas pump were to be, eg 60% efficient, (the rest being lost as heat out the exhaust and off the cooling fins on the engine)
then for say a 3 inch dredge, 3 x 1hp = 3 x 750W = 2250 watts, or 2 1/4 kilowatts.
But if a brushless pump were 85% efficient, which is no problem, 90% is available off the shelf (in BL motors)
then we get
2250W with a 60% gas engine implies the actual work done is 1350 watts of work for the 3" dredge. We can call this 1350 watts out,
and if we have an 85% efficiency power unit we need "only" have 1350 / .85 which is 1588 Watts in with the brushless pump.
.. and that leccie version would do the exact same work at the 3hp gasser.
So 1588 watts in using a 10 cell lipoly battery of 37V would run at 1588/37 = 42.9 amps which is a reasonable current.
The reason to step up to 37V is to keep amps down and cost down.
But if we leave it as a 12 volt system, then 1588/12 = 132 amps which is extremely high for constant running.
So for an hour 43 amps is required to match the gasoline.
For 4 hours that would be 4 x 43 = 172 Amp hours at 37 volts
and that's where the electric comes a cropper, because that's an big expensive battery - a 200 Amp 12V battery in lithium would be $2000 plus.
I don't know what a 200 amp hour 37Volt battery would cost!
So it's clear that where we waste excess gas power without being unduly concerned, electric must exploit all power reduction tricks, like shortening the suction tubes, bringing the dredge down to the material rather than lifting the material to the dredge, aiming primarily at the smaller diameter dredges in the first place, short duration sessions, and so on.
If you do that you get into rechargeable low cost operation with electric and stop buying gasoline.
The first thing I would mention is that electric brushless is amazing at delivering torque, something which two stroke engines only do when revved right up high. Four strokes are more torquey at medium range rpm, so brushless compares better with 4-stroke than with 2-stroke in operation.
The next thing is that as engines reduce in capacity, gasoline engines tend to hit a minimum design weight and then stop getting lighter. It takes metal to contain the vibration and distribute the heat. But electric gets smaller as the size reduces in a much more linear way, so small equals light and compact in EP but not so much in GP.
This might be a long winded way of saying that (based on the way I look at these things) the Goldsnare could be the beginning of a new niche retail dredge market (small size) which was previously only available to DIY builders. Also the smaller the diameter of the dredge, the more future versions will be electric due to weight advantages. So for sniping, definitely.
And if Tesla and the European electric car makers get their acts together, we should see 2 1/2" become viable for electric within a reasonable time period. Until then 2" appears to be a practical limit based on cost of power.
But that doesn't mean it can't be done right now already. A gas powered generator can easily provide a couple of KW which can be sent by cable to an electric dredge. No expensive batteries required!
That would put the dredge on a power tether (power cable) with the pump located at point of use. That would be far more flexible than the current arrangement with the gas pump tethered to the dredge by water bearing hose pipes. So electric, in gas generator electric pump hybrid style, is a lot closer (in bigger diameters) than folks might think.
