380 dc Motor

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26 July 2016 at 19:44 #66769
KEVIN DUGUID
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@kevinduguid52417
will a 380 dc motor working off a 6v 3.2amp battery be able to power a 35mm prop?
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26 July 2016 at 19:44 #5432
KEVIN DUGUID
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@kevinduguid52417
26 July 2016 at 20:52 #66770
Dave Milbourn
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@davemilbourn48782
What type of 35mm prop and what model?

DM
27 July 2016 at 09:57 #66781
Malcolm Frary
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@malcolmfrary95515
Depends on the voltage rating of the 380 and how much current it wants with the type of prop and whether the prop is right for the boat.
27 July 2016 at 11:38 #66784
KEVIN DUGUID
Participant
@kevinduguid52417
35mm brass d type 4 blade LH and RH on the billings coast guard 1/20
27 July 2016 at 13:20 #66785
Dave Milbourn
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@davemilbourn48782
You might get away with two 380's on 6v but the props look a bit large for 380 motors. Give it a shot anyway; if you have to change to 385s then they will fit directly with no modification and you won't break the bank doing it, but you will need a higher voltage.

Dave M
27 July 2016 at 16:46 #66798
ashley needham
Participant
@ashleyneedham69188
I would go a bit further than DM and say that 4 blade 35`s are definitely a bit much for a 380.

I would go with twin blade plastic 35mm (S pitch, not X pitch types), or 3 blade plastic 35`s, but not brass 4 blade, and even brass 3 blade ones at 35mm are a bit strong.

The 380 or 400 motor is a nice small high speed unit and I think the fitting of a pair of them, with the 35mm plastic props or even 30mm 3-blade brass would give your boat a bit of go. A 480 motor from J perkins would be a direct substitute for even more oomph (but they are a bit longer.

Ashley
27 July 2016 at 19:57 #66801
KEVIN DUGUID
Participant
@kevinduguid52417
the 380 heading for the bin burnt them out, plastic blades not great in salt water, have put the 550 back in for the time being but means only 1 battery
28 July 2016 at 08:15 #66804
ashley needham
Participant
@ashleyneedham69188
Kevin. What is currently fitted? there is a massive difference between a 550 and a 380. If 500 can size motors are currently fitted then an MFA 540/1 type motor (the low power one) would be most suitable for a 4 blade 35mm prop.

What is not great about the plastic props?? The 3 blade ones have a small pitch and will not give as much thrust, size for size compared to a brass one, but work reasonably well at higher speeds. Two blade plastic props will drive anything and are suitable for all boats (as a rule) other than obviously not looking so good.

If the motor/prop is mismatched then this is another issue and not necessarily the fault of the prop in question.

Ashley
28 July 2016 at 10:32 #66810
KEVIN DUGUID
Participant
@kevinduguid52417
when I built back 20years ago it was 550 motors that I fitted, but just refurb it. and thought smaller motors would be better and have it working off 2 speed controller and 2 batteries, as there would be more room.
28 July 2016 at 11:10 #66811
Malcolm Frary
Participant
@malcolmfrary95515
Repeating the rule of thumb for direct drive and brushed motors, the prop should be of less diameter than the motor can, and should have fewer blades than the motor has poles. The 380 fails both criteria and leaves a fast motor overloaded being unable to provide the torque required, and just producing heat.

Having sailed in nothing but salt water, I have noted that plastic props never suffer corrosion.
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