Nobels Bowthuster mystery setup/chain disconnected - help!

[Odana]

We bought our boat with a non-working Nobels bowthruster which we are now trying to get working - there are some mysteries I need to solve. Apologies for length of description here

 

I recall vaguely that the previous owner said the charging was rubbish (2 x battery at front charged via 60ft of cable from back) and they had not bothered replacing batteries when they died. But he said he turned the motor manually every now and again to check it wasn't seized (no idea if this was true). When we viewed the boat he took a domestic battery and tried to operate the bowthruster. It grunted a bit but wouldn't do much - sounded like the battery was being flattened trying. So we agreed we'd buy the boat as having no bowthruster - it wasn't a priority. He removed the old dead batteries before we took the boat - presumably for scrap. We've not investigated anything since - 2.5 years. We can't contact the previous owner.

 

We have the boat in dock this week and have decided to see if we can get the bowthruster working. (if the unit is working then we'll improve the charging system with a charging unit near the front of boat, and invest in new batteries)

 

With the help of a friendly local electrics-savvy chap at Hawne Basin we have managed to discover the following:

• Motor turns as does impeller - nothing seems seized. Good news, as we should be able to do any repair work while back in the water so no rush this week.
• 
  
• From the control panel with ignition on, the motor will operate left but not right. I suspect a dodgy connection. Next step is to go through and check/improve all contacts, as some of the 'chocolate block' connections are decidedly iffy. Is there any other reason this might be happening ? Anything specific I should be looking for?
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• Big mystery - the chain is disconnected (see pic below). It has two bits of wire tied round it to stop it dropping completely into the oil bath. Why would someone have done this? Would it be to stop it seizing up dry when not in use? Is there any other reason? I am very confused. When we pull on the chain in either direction the impeller turns, but we've not done full rotations because of the wire. Also not connected chain to motor yet.
• 
  

All thoughts gratefully received!

 

[RLWP]

It looks like someone got as far into the investigation as you have. They took the chain off for diagnostic purposes and drew a blank, so they shoved the lid back on and left it

 

Richard

[Bee]

I think I would start by getting a link for the chain, any bearing or power transmission place will be able to help, re-assemble the whole thing and rotate things by hand to see what happens, perhaps the old link has dropped inside the works .If it is all aligned and the tension on the chain is ok then I would try a battery on it., If it struggles the motor might need a specialist to look it over, when it all works nicely sort out the rest of the switchgear and wiring. I'm sure it can be made to work.

[Stormbringer]

Last thruster I know of that stopped working one way had a sticky Albright relay...

Cheap and easy fix (strip and clean ).... worth a look ...

[Odana]

Thanks all. Chain intact - will refit and see if all turns. Will do what I can on the switch - I suspect summat simple.

 

Then I may call Uncle Richard - if he's willing to tinker with it.

 

Big relief is that we don't have to rush and get it all done by Thursday while out of the water. As it's there it'd be nice to be able to use the bowthruster if it doesn't get too complicated and expensive, but we aren't desperate.

[RLWP]

As long as Unkle Richard doesn't have to get involved with complimicated electrical chargering things. He believes 12V electrics more complicated than an alternator, battery, switches and incandescent lights is too hard for human beings to comprehend

 

Richard

[bizzard]

That jump lead clamp at the back of the motor would be a bit iffy if its clamped on and acting as the motors neg- connection.

[Timleech]

Could easily be a seized contactor. They look similar to the ones on my 'swing-lift' crane, which don't like the damp, I have to dismantle and derust them every couple of years.

 

Tim

Edited May 4, 2015 by Timleech

[Dinz]

Chain disconnected . Straight out of a Haynes manual!

Would think that motor has been checked over away from prop so as to confirm which part has been causing issue.

The motor would take far less current disconnected and allow more 'playtime' fault finding.

Of course this would then not show up any cabling size/connection issues as less current being demanded on circuits.

Bit of a catch 22 event.

If drive prop and motor spin up ok then re-assemble and wiring time.

Good luck.

[Odana]

That jump lead clamp at the back of the motor would be a bit iffy if its clamped on and acting as the motors neg- connection.

Don't worry - jump leads were just to attach to borrowed battery yesterday to test stuff.

Could easily be a seized contactor. They look similar to the ones on my 'swing-lift' crane, which don't like the damp, I have to dismantle and derust them every couple of years.

 

Tim

Which bit, Tim? The unit on the side? I was hoping to avoid messing with that bit!

 

 

OK Unkle Richard. We promise not to ask you anything wot isn't motor-related. I hate electrics too. I can't SEE electrickery.

[Timleech]

Which bit, Tim? The unit on the side? I was hoping to avoid messing with that bit!

Yes, the two lumps on the side with wires and copper links going in & out.

 

It shouldn't be hard to test their operation without taking them apart.

 

Tim

[Murflynn]

Last thruster I know of that stopped working one way had a sticky Albright relay...

Cheap and easy fix (strip and clean ).... worth a look ...

+1

 

if the contacts look burnt you can get replacements cheap from Albright International in London. the contacts are silver buttons brazed onto copper flat bar strips.

 

other contacts on the motor, battery, etc. should be checked - poor contacts are the most common culprit and once they start burning (sparking) they deteriorate very quickly.

[Arnot]

Another possibility given the comment about it seeming to flatten the battery is that the field windings have internally short circuited to the casing of the motor. The symptoms of this are much as you describe in terms of the power drain and lack of drive. This probably won't explain the one direction thing though...

 

The way to find out is to dismantle the motor and test the insulation of the field coils. The good news is that this is usually easy to sort out given the skill and equipment. It doesn't involve hard to get parts, just some paint, cotton tape and varnish.

 

It is however one of those old fashioned skills that seem to be dying out, it's probably best to find an old fashioned auto electrician to have a look at it.

 

Hope this helps

 

Arnot

[RLWP]

Another possibility given the comment about it seeming to flatten the battery is that the field windings have internally short circuited to the casing of the motor. The symptoms of this are much as you describe in terms of the power drain and lack of drive. This probably won't explain the one direction thing though...

 

The way to find out is to dismantle the motor and test the insulation of the field coils. The good news is that this is usually easy to sort out given the skill and equipment. It doesn't involve hard to get parts, just some paint, cotton tape and varnish.

 

It is however one of those old fashioned skills that seem to be dying out, it's probably best to find an old fashioned auto electrician to have a look at it.

 

Hope this helps

 

Arnot

 

Clever! I have just had a starter motor reconditioned because the field windings had shorted. It does, as you say, flatten the battery PDQ.

 

Not as spectacular as the one where the field windings had shorted to the case in a couple of places. A dead short across the batteries doesn't half make the flexible cables jump about

 

Richard

[MoominPapa]

As long as Unkle Richard doesn't have to get involved with complimicated electrical chargering things. He believes 12V electrics more complicated than an alternator, battery, switches and incandescent lights is too hard for human beings to comprehend

 

Richard

The Moomin, on the other hand, defers to Unkle Richard on all maters of chains, sprockets, gears and bearings, but positively delights in circuits and wires and multimeters. I'm happy to come and give it a whirl if you can come and collect me from my lair, somewhere around Preston Baggot.

 

MP.

[RLWP]

The Moomin, on the other hand, defers to Unkle Richard on all maters of chains, sprockets, gears and bearings, but positively delights in circuits and wires and multimeters. I'm happy to come and give it a whirl if you can come and collect me from my lair, somewhere around Preston Baggot.

 

MP.

 

Aaiiii - an Alchemist! He must Burn!*

 

Richard

 

*Probably will if he gets it wrong and The Smoke gets out of the wires

[MoominPapa]

 

Aaiiii - an Alchemist! He must Burn!*

 

Richard

 

*Probably will if he gets it wrong and The Smoke gets out of the wires

I'll bring some spare.

 

MP.

 

 

[bizzard]

Similar to my bottled 'darkness' which I collected to make the electric dark bulb.

[smileypete]

Thing on the side of the motor looks like a reversing contactor.

 

If the thruster always spins the same way it may just be the coil connections, otherwise as said burnt contacts.

 

I hate electrics too. I can't SEE electrickery.

 

Dat iz wot voltmeters, clamp ammeters and test bubls are for!

 

ETA A good local motor rewind place may be able to test the motor and sort the contactors.

 

cheers, Pete.

~smpt~

Edited May 4, 2015 by smileypete

[Odana]

Mr Moomin - you're on!

Blacking today and tomorrow then we can focus on bow thrusters, so text at your convenience. Can fetch you. Or if you are in the area for the BCN challenge do feel free to stay at HP as long as you like....

[blackrose]

On the subject of charging the BT batteries: if the boat has an AC generator such as a Travelpower you could put a small dedicated 3 stage charger at the bow, if not then you could run the charger from the inverter. This is essentially using your domestic batteries/alternator to charge your BT batteries, so I'm not sure how this would affect your domestic batteries - I guess it depends on the alternator output and how much you use the BT.

 

My boat has 2 alternators and the charge to the BT is taken from the start battery alternator. I have one of these, which splits the charge between the start and BT batteries at the bow.

 

The cable that runs from the VSR to the BT batteries is only 16mm2 so there's obviously a lot of voltage drop, but as I don't over-use the BT it has plenty of time to charge and I've never flattened the BT batteries (2 x 110a/h). The cables from the BT batteries to the BT motor are short and about 70mm2 diameter to deal with the instant demand.

 

Most boats I see with BTs with split charging, split the charge between the domestic batteries and BT batteries and this makes no sense to me. Since the start battery will generally get topped up much quicker then the domestics, the charge will go to the BT batteries quicker if it's split between start and BT. Once the start battery is fully charged it won't need any additional charge so the charge can all be directed to the BT batteries. That's not necessarily the case with the domestic batteries.

Edited May 4, 2015 by blackrose

[Odana]

Blackrose - this was our plan if/when we repaired it. No point in trying to charge from 60ft away. We have a Victron inverter which is on most of the time so we plan to charge from a unit plugged in at the front under the steps.

[blackrose]

Blackrose - this was our plan if/when we repaired it. No point in trying to charge from 60ft away. We have a Victron inverter which is on most of the time so we plan to charge from a unit plugged in at the front under the steps.

 

Well in a sense you are charging from 60ft away because ultimately that charge comes from your domestic batteries/alternator, but it's probably a lot more efficient to convert from DC to AC and convert it back to 12v up at the bow. If I had a problem with my BT battery charging system then that's what I'd do.

 

I think you'll only need a small charger - about 10 - 20 amp output. If your BT batteries are sealed then any 3 stage charger with a maximum 14.4v charge will be fine. If the charger has no battery type settings then it will likely be 14.4v. If your batteries are open wet/lead acid then you'd be better off with a 14.8v max, but small chargers with different battery type settings are more difficult to find.

Edited May 4, 2015 by blackrose

[by'eck]

On the subject of BT battery charging a few extra options:

 

Use external engine alternator sensing to offset voltage drop on long charge cables.

 

Use of of the new Sterling battery chemistry modules that control charge voltage to a pre-set at source. They even offer 12-24 volt modules.

 

Or as I do, use 35mm2 charge cables to benefit both alternator and mains charging. I have a dedicated monitor directly on BT batts which proves volt drop is not an issue. Indeed have seen over 100 amps charge current into the pair of BT batteries I have.Had to increase cable fuse to 200 amps!

[Plonk]

Similar to my bottled 'darkness' which I collected to make the electric dark bulb.

 

Similar to my bottled 'darkness' which I collected to make the electric dark bulb.

I was thinking of painting some light bulbs black, so that when i switch them on it gets dark.