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[Buccaneer]

I am considering a rebuild of a scratch built Tug I acquired a few years ago and would like to include a Bow Thruster. I see that all the Raboesch models use a 7.2 volt motor, whereas all my electrics run off a 12V SLA Battery and an Action P92 Power Distribution Board. Is there a simple way to get 7.2V out of the P92 without shelling out another Ģ35 or so for an Action P93?

I do have a spare 6V 2.8Ahr SLA battery. Would this suffice if connected up through it's own circuit, ESC etc. The benefits are simple - it is paid for and I have a charger. Swapping to a 7.2V Battery of a different type would entail purchasing Battery and Charger and I am then back to the P93 dilemma.

John

[Time Bandit]

If you donīt want the second battery, change the motor to 12V 

http://www.componentshop.co.uk/385-dc-motor.html


The 6V batt will work and you need an ESC anyway to control the motor.

[inertia]

Looking at the data for the MFA 380 and 385, the 385 would only rev at 11000 on 12v c/w 26000 for the 380 as fitted (both figures no-load). That would make the bow thruster pretty slow to do much turning. The better option would be the 6v battery and another ESC. The only way to get 7.2v out of a P92 is to put 7.2v into it.
DM

[Buccaneer]

Hello Dave and Tobias

Thanks for the inputs. It confirms my thinking but with my level of knowledge it is always worth a check.

John

[KaMeWa]

Looking at the data for the MFA 380 and 385, the 385 would only rev at 11000 on 12v c/w 26000 for the 380 as fitted (both figures no-load). That would make the bow thruster pretty slow to do much turning.

Hi,

This depends completely on size of the boat, model/size of the thruster and performance/power which is wanted. I re-fitted my Berlinīs Robbe-thruster with a MFA 385 fed with 12V, and result is great: very realistic, not-too-powerful thruster which gives great precise manouvering ability. Earlier standard 380/400 was way too powerful, and as 3-pole motor, gave quite poor slow-speed control.  Also thrusters tend to cavitate heavily on high rpm.

BR,
- Mikko

[inertia]

Many thanks for this, Mikko - we learn something every day.
Dave M

[Buccaneer]

I have a spare 385 in the Bits box. I'll file all the info away and wait for decision day. Space and displacement might come into it as well with the extra battery.
Many Thanks.
John

[cos918]

If the thruster is of the flat blade type . You need to watch the RPM . If you replace the motor with one that has higher RPM you could  put to much load on the blade . The blade is made of plastic and is a tight push fit on the shaft . What can happen if to much load is put on the blade it will start to slip on the shaft . The slipping will only get worse until the thruster no longer works .


john

[derekwarner]

I am sure Mikko is correct........too many people think bow thrusters are for to be used as port & stdb ski boats.....

Really depends on the type of model....but if you want good control consider a quality reversible ESC...an investment in scale performance ......Derek

PS....have just spied in another thread here on MBM......an example of my thought .............

[inertia]

John
No need to worry, m'duck. A 385 is quite a bit slower than a 380, even on 12 volts.
DM

[Buccaneer]

At the end of the day it is being operated through an ESC, so move the stick a little bit and see what happens. If I like it I'll move the stick a little bit more. QED.
John