Pump for bow thruster – advice wanted.

[Colin BishopModerator @colinbishop34627]

A while back I bought the Revell Queen Mary 2 plastic kit with a view to motorising it. The late lamented Richard Webb wrote a review on doing this in Model Boats and said he used a Halfords windscreen washer pump Ref: HWP21 to use for the bow thruster. He didn’t make it clear just how he had fitted it though. I have bought the pump – photo below – and it has two washer tube connectors plus a big hole in the back where it is intended to mate to the car washer bottle. I’m not at all clear just how this is supposed to work in the boat!

 

My setup has a washer tube fitted to each side of the bow of the model and I had assumed that it would be possible to suck water from one side and push it out the other and vice versa but this pump doesn’t seem to lend itself to this configuration. Richard refers to sucking water from the underside of the hull and squirting it out of the bow thruster holes but I’m not at all clear how he did this if using this pump.

 

Any ideas anyone, or are there alternative pumps which could be used as this one seems a bit heavy for the model and is of course 12v.

 

Colin

 

[Colin BishopModerator @colinbishop34627]

[60wattParticipant @60watt]

I’ve just used a pump for a fire monitor so I am not sure which is best.I would have thought most suitable pump would be low pressure high flow rate used in caravan plumbing.Just a notion.

 

If you already use a servo+microswitch to engage the pump then use the servo to pinch silicone tubing,left or right.

 

Colin,you say bow thruster but if the battery and centre of gravity happens to be up front and you want steering -not docking,site the exit as far away from the COG

 

[Kevin Flack 2Participant @kevinflack2]

I was also wanting to fit a car type washer pump as a bow thruster but as I see that in your example the water is gravity in the back as fitted to the bottle and pumped out of the small pipes I wonder how I would use this type of pump.

I had thought by changing the motor polarity I would be able to pump the flow in either direction so as to get the side thrust effect?

Well back to the thinking stage again, will just fit the pipes to the hull and await a solution from you good experienced chaps then!

Kevin

[Phil Winks 1Participant @philwinks1]

Colin & Kevin that pump is reversable so changing polarity changes the nozzle that the water exits from giving (on a car) front and rear windsceen washers so one assumes that you would fit it with the washer bottle bit through the bottom of the boat and one nozzle exiting eitherside of the bow then power the motor with a reversable esc so one way pushes left and the other pushes right. you will need equal amounts of power in forward and reverse so an MTronics mirror esc springs to mind. although I’m sure DM has a suitable alternative and would advise accordingly. the gravity feed issue is overcome by ensuring the pump body is fitted below the waterline. as it must be if the inlet is placed through the hull bottom.

 

 

Hope this helps regards Phil

Edited By Phil Winks 1 on 08/06/2010 22:55:44

[60wattParticipant @60watt]

If the reversing valve has a high operating voltage then fully proportional operation will not be possible.

[Phil Winks 1Participant @philwinks1]

The valve is mechanical I believe  (a simple rubber flap) and dependant on the impeller rotational directionif you look closely at the pump it has 2 wires only and the motor simply works forward for one jet and reverse for the other and the flap moves to cover one port or the other dependant on which side the impeller is pushing water at. in the neutral state both ouputs are open as the valve self centres. not a problem on a car as the washer jets are higher than the bottle that this is usually fitted to.

 

Phil

[Colin BishopModerator @colinbishop34627]

Just got around to trying it in the kitchen sink and it does indeed operate as Phil has described. It gives a healthy stream on 12v but only a very weak one on 6v. I will have to rig up a 9v supply and see how that goes. It’s maybe a bit on the heavy side for the boat though at just under 100g.

 

Doubt if I will bother with an ESC if I do fit it, just use a servo and microswitches as it would just be used for quick blasts to push the bow one way or another.

 

As a windscreen washer pump I am assuming it isn’t rated for continous running so having it come on atomatically when full rudder is applied would probably not be a good idea!

 

Colin

[Phil Winks 1Participant @philwinks1]

Hi Colin sorry I’ve been so long in replying! Been on my hols .

 

On the question of the pump motors service cycle ie:continuous running ability, I reckon 30secs is definitely safe and prob a full minute could be possible I guess the only sure way to find out is to test to destruction . 

 

However holding it while running to see if it gets hot would give a good idea of a safe time limit.  One suggestion I would make, is do not run it dry for more than a few seconds. 

 

Also how often do you hold full rudder for more than 30 seconds.

 

Phil 

[Colin BishopModerator @colinbishop34627]

Yes, I don’t think that the operating time would be too much of a problem. It would only be used to give the bows a brief nudge rather than spin the model like a top[!

 

Colin

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