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[ChrisH1981]

Good morning all, as above title suggests im trying to choose a suitable motor for the AL KHUBAR. Ive decided id like direct drive due to the terrible noise a gearbox makes (made that mistake in a slipway IRISHMAN tug).
Planning to run the tug on a 12v battery.


Do any of you own or have experience of the AL KHUBAR? Thanks :)

[Tug Fanatic]

The Al Khubar is available as both a kit and plans. They are different sizes.

What size are you building?

I have a 42in Al Khubar and it is powered direct drive by 2 Smiths car heater motors - around 60 watts each and 3000rpm unloaded.

[ChrisH1981]

The Al Khubar is available as both a kit and plans. They are different sizes.

What size are you building?

I have a 42in Al Khubar and it is powered direct drive by 2 Smiths car heater motors - around 60 watts each and 3000rpm unloaded.

Hi! Many thanks for your reply! Its the model slipway kit version of the AL Khubar. 1:32nd scale at 31 inches long

[Colin Bishop]

The late Dave Milbourn published an Action Electronics wiring diagram for Al Khubar which featured Torpedo 500 6:1 geared motors.

http://vp-airsoft.co.uk/pdfs/Slipway%20Dutch%20Courage.pdf

Should be easy to get such as from Component Shop and others:

https://www.componentshop.co.uk/motor-540-gearbox-ratio-100-2.html

Colin

[chas]

If you want to avoid a gearbox as you say, look at the Mfa LN 540 motor, ( not any other 540 type) or possibly a 555 motor from many other vendors.
  I prefer the LN 540, low drain, high torque, correct rev range.I

[Colin Bishop]

 I have the  MFA geared motors (385 type 11:1 reduction) in my paddler and the noise isn't obtrusive at all. Some gearboxes are indeed noisy, especially open ones.

I think you are stuck with the prop size due to the Kort. The setup in Dave's diagram was recommended by Model Slipway they ought to know.

Alternatively you could use a toothed belt drive to gear the motor down.

Obviously direct drive is an option but, as Chas implies, you need to match the motor to the prop carefully to avoid excessive current consumption.

Colin

[chas]

Chris, you don't say what type of geared motor you used before that was so noisy. Like Colin I like the Mfa geared motors, I'm installing the geared 385 in my current build next week, they are really nice motors, not as quiet as direct drive, but not noisy. We'll worth considering, and with different ratios available.

[NickelBelter]

What size are the propellers on the Slipway kit?  This is the most crucial piece of info. 

[ChrisH1981]

Good evening all. sorry for the late reply to the comments, which are all very informative. Im not 100% sure on prop diameter as the model is in storage and not easy to access. I would guess at about 40mm prop diameter.


As for the motor choices. the 540LN's were on the radar for me as a suitable candidate, however, i am also leaning towards the  6:1 ratio motors. What would I expect the output shaft RPM to be?
Id like to have a bit over scale speed to get out of trouble so to speak!

[Colin Bishop]

If you look on the Component Shop website you will find the technical information you are looking for with RPM at various input voltages.

Colin

[ChrisH1981]

If you look on the Component Shop website you will find the technical information you are looking for with RPM at various input voltages.

Colin

Thanks Colin

[NickelBelter]

All the 540 motors I see on Component shop have an RPM that's a bit too high for 40mm props on a 12v battery.  I would recommend the 555s instead.

[Tug Fanatic]

.................I'm not 100% sure on prop diameter as the model is in storage and not easy to access. I would guess at about 40mm prop diameter.......................

This is very important as the load factor of the prop (the load on the motor) is effectively approximately going up 50% with each 5mm added at these sizes.

[chas]

https://www.mfacomodrills.com/motors/540ln.html

This is the 540 LN  as suggested.

[Colin Bishop]

Is there a particular reason for a 12v setup?

Colin