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Thank you Crowthers


Jamboat

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Just thought our little tale about our prop was worth telling....

In May 2015 we went into the dry dock at  Portland Basin, Ashton -under-Lyne for blacking & to sort our badly bent (vetus) propeller. The prop was sent off to Crowthers to be straightened & came back a few days later looking like new though we were warned that it “ wouldn’t take another straightening” but we weren’t overly concerned as we sailed off with newly blacked bottom & refurbished shiny prop.

Fast forward to December 2017, we are in Uplands Marina for the winter & are booked in for blacking with PIW narrowboat services for blacking in March but once again we have a bent prop :( & this time we need a new one.  We don’t really want another vetus prop given the problems we have had but as we have vetus stern gear we really need one made to measure.

I know I should but I don’t know what size prop we need, it’s one of those things that I have never known about our boat, normally I save invoices/receipts, religiously...but somehow don’t have the paperwork from Portland Basin/Crowthers where it may have been noted down.

So this morning I rang Crowthers to see if they could help & work out what we needed,  the lady who answered (Amanda?) said give me 10 minutes ....then rang me back with all the information needed as they had the original details of the work done on our prop in 2015 !                                           They evidently have records of jobs going back 30 years, all on a card system, not computerised, so if you have ever used Crowthers you’ll likely be in there somewhere !

A new prop is now on order which will be ready in January at a cost of £426 inc vat & delivery, which I think is very reasonable. 

 

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12 minutes ago, zenataomm said:

How do you keep bending your prop?

1st time was  in Stretford, a length of blue c&rt rope that wrapped itself round the prop,  it had  2’ of 2”x2” on the other end that bashed the into prop, bending 2 blades.

2nd time just a lump of wood that we picked up nr Calverly :( 

it has been said that vetus props are not the sturdiest......

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I have a feeling that you will find that your Crowthers prop will turn out to be rather heavier than the Vetus one. I get the impression that many salty water boat props (and Vetus seem to have their expertise in that area) are rather thinner than those made specifically for inland boats and canal boats in particular.

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6 minutes ago, Tony Brooks said:

I have a feeling that you will find that your Crowthers prop will turn out to be rather heavier than the Vetus one. I get the impression that many salty water boat props (and Vetus seem to have their expertise in that area) are rather thinner than those made specifically for inland boats and canal boats in particular.

That’s more or less what we’ve been told so are hoping that the Crowthers prop will be sturdier than the vetus. 

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1 hour ago, nb Innisfree said:

I wanged our Crowther prop really hard on a rock, when we eventually docked for blacking there was just a slight chip on the edge of one blade. Very sturdy casting. 

That's why I asked the question, in fifty years of boating I've only heavily whacked a proper prop properly, probably. An angle grinder put that to rights two years later at docking.

I did smash an aluminium one on an Enfield Z leg, which was nice.

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We have a Crowther which is now 26 years old or so, many miles and its fair share of abuse, and its still spot on.

 - Very happy to be on a t-card system of theirs! 26x32" ordered by a T Mason, my grandfather! I still have the graphs he drew out when selecting the pitch.

 

Daniel

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13 hours ago, Jamboat said:

1st time was  in Stretford, a length of blue c&rt rope that wrapped itself round the prop,  it had  2’ of 2”x2” on the other end that bashed the into prop, bending 2 blades.

2nd time just a lump of wood that we picked up nr Calverly :( 

it has been said that vetus props are not the sturdiest......

 

Did either of these two prop foulings stop the engine dead? There is a lot to be said for having at least one friction-only coupling in the driveshaft, designed to slip a bit in the event of a prop jam to save it getting bent. 

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4 hours ago, Mike the Boilerman said:

 

Did either of these two prop foulings stop the engine dead? There is a lot to be said for having at least one friction-only coupling in the driveshaft, designed to slip a bit in the event of a prop jam to save it getting bent. 

The first one stopped the engine dead, making one hell of a racket as it clattered round the prop, we do have a flexible coupling “thing “ - not sure correct terminology - on the propshaft. The second time it didn’t , but obviously it wasn’t going to take much to bend it again 

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I think it has in the past been established that the Vetus props are not really the most substantial think for use on our rubbish infested canals.

I wouldn't get too hung up on why they bend, as I think any more suitable replacement (whether Crowthers or not), might be far less likely to, hit with the same object.

What I can say thought is that when we were trying to find a new (big) prop for Flamingo, before we found we could modify the existing one, Crowthers were hugely more expensive, and a far longer lead time than other suppliers.

There was no evidence it would actually have been a heavier duty prop, than forexample one we were quoted by a Scottish based propeller supplier.

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17 hours ago, Tony Brooks said:

I have a feeling that you will find that your Crowthers prop will turn out to be rather heavier than the Vetus one. I get the impression that many salty water boat props (and Vetus seem to have their expertise in that area) are rather thinner than those made specifically for inland boats and canal boats in particular.

Some salty water props are made of different materials. Ours are an aluminium alloy which tend to suffer if they get knocked about.

Although having said that since changing to the J Series props from Volvo Penta a few years ago now we have not had a single bend in them despite them taking some pretty hefty knocks. They are a different aluminium alloy again to our old A Series props.

15 hours ago, zenataomm said:

That's why I asked the question, in fifty years of boating I've only heavily whacked a proper prop properly, probably. An angle grinder put that to rights two years later at docking.

I did smash an aluminium one on an Enfield Z leg, which was nice.

Only one? We have smashed several sets of duo props in the past. One set in spectacular style when 4 of the 7 blades sheared from the hub completely. They were beyond refurbishment!

Luckily we always carry a spare set. However as I said above since swapping to J Series props we have not picked up a ding yet. Still carry a spare set though just in case.

25 minutes ago, Jamboat said:

The first one stopped the engine dead, making one hell of a racket as it clattered round the prop, we do have a flexible coupling “thing “ - not sure correct terminology - on the propshaft. The second time it didn’t , but obviously it wasn’t going to take much to bend it again 

Once they have been refurbished they are never as good as a new set. 

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On 13/12/2017 at 07:55, Jamboat said:

The first one stopped the engine dead, making one hell of a racket as it clattered round the prop, we do have a flexible coupling “thing “ - not sure correct terminology - on the propshaft. The second time it didn’t , but obviously it wasn’t going to take much to bend it again 

 

A flexible coupling is a lot better than none but not quite what I meant.

If a prop jam occurs stopping the engine dead, the energy that bends the prop is the kinetic energy present in the rotating engine flywheel, crankshaft etc, rather than the basic engine power which just pushes the boat along. 

Consequently, a truly massive instantaneous force gets transmitted along the prop shaft at the instant of the jam and a coupling which can slip under this extreme stress is a Very Good Thing and might well save the prop from getting bent. Think of it as is the mechanical equivalent of a fuse in an electrical circuit. 

A 'slip joint' in a propshaft in its simplest form would be a plain shaft clamp coupling with the woodruffe key taken out and the clamp bolt tightened sufficiently to grip during normal operation but not tightly enough to continue to rigidly grip in the event of a prop jam. 

Edit to add:

A 'friction joint' might be a better term for what I'm suggesting.

Edited by Mike the Boilerman
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1 hour ago, alan_fincher said:

What I can say thought is that when we were trying to find a new (big) prop for Flamingo, before we found we could modify the existing one, Crowthers were hugely more expensive, and a far longer lead time than other suppliers.

Fortunately for us this is not our experience, it will be ready in January & at a cost comparable with buying on off the shelf, also Crowthers having the paperwork from our last prop incident was very helpful.

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30 minutes ago, Mike the Boilerman said:

 

A flexible coupling is a lot better than none but not quite what I meant.

If a prop jam occurs stopping the engine dead, the energy that bends the prop is the kinetic energy present in the rotating engine flywheel, crankshaft etc, rather than the basic engine power which just pushes the boat along. 

Consequently, a truly massive instantaneous force gets transmitted along the prop shaft at the instant of the jam and a coupling which can slip under this extreme stress is a Very Good Thing and might well save the prop from getting bent. Think of it as is the mechanical equivalent of a fuse in an electrical circuit. 

A 'slip joint' in a propshaft in its simplest form would be a plain shaft clamp coupling with the woodruffe key taken out and the clamp bolt tightened sufficiently to grip during normal operation but not tightly enough to continue to rigidly grip in the event of a prop jam. 

Edit to add:

A 'friction joint' might be a better term for what I'm suggesting.

Or Torque Limiter?they do exist ,often get Binned as they lose their Grip after a while.Volvo Penta have had them on their Turbo Diesel Inboards for Decades.

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My experience of Crowthers was a very positive one. Following cracking our prop on something very solid on the Ashton Canal, (we were on our way to take it out for blacking at Ashton Packet Boat), we took the boat out onto the slipway on the Saturday and Rang Crowthers on the Monday morning. As I had been thinking that the boat was under propped I asked the Lady on the phone what they would recommend and gave them all the engine, boat details. They specified a prop, and after a hour or so rang back and said they had a casting available that just required machining, and it would be ready for Thursday.

My wife went round on the Thursday with the short end of the prop shaft which I had taken off and slipped out of the back of the boat. Mrs Crowther looked after our six month old baby girl whilst my wife took the shaft down to Mr Crowther who fitted the new prop to the shaft and carried it out to the car. After work I slid the shaft with prop fitted back in the boat and connected it. We put our boat back in the water the next Saturday. So a week to clean, fettle and black the hull, and obtain and fit a new prop. It worked well, better than the one we removed and is still doing so. my Daughter is now twelve!.

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1 hour ago, Mike the Boilerman said:

 

A flexible coupling is a lot better than none but not quite what I meant.

If a prop jam occurs stopping the engine dead, the energy that bends the prop is the kinetic energy present in the rotating engine flywheel, crankshaft etc, rather than the basic engine power which just pushes the boat along. 

Consequently, a truly massive instantaneous force gets transmitted along the prop shaft at the instant of the jam and a coupling which can slip under this extreme stress is a Very Good Thing and might well save the prop from getting bent. Think of it as is the mechanical equivalent of a fuse in an electrical circuit. 

A 'slip joint' in a propshaft in its simplest form would be a plain shaft clamp coupling with the woodruffe key taken out and the clamp bolt tightened sufficiently to grip during normal operation but not tightly enough to continue to rigidly grip in the event of a prop jam. 

Edit to add:

A 'friction joint' might be a better term for what I'm suggesting.

It may also save gearbox problems and engine mounts

 

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When I collected our prop from Crowther Keith showed me an auto lube device and told me I could have it as a gift. The lady in the office, a proper northern lass I recall, took the fag out of her mouth and said "Bloody 'ell Keith, givin' summat away, are you feelin' alright?"

Priceless.

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On 13/12/2017 at 08:08, alan_fincher said:

I think it has in the past been established that the Vetus props are not really the most substantial think for use on our rubbish infested canals.

Has it? I'm sure it's been said, but less convinced it's been established.

My Vetus prop is still unbent after 13 years and I used to regularly take my boat on the southern GU and Paddington arm which are full of rubbish. I don't know how many Vetus props are fitted to canal boats compared to others, but I wonder if it's another of those cases where we hear more negative reports simply because there are more of them in use?

Edited by blackrose
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Any sort of coupling that could slip could just wear the end of the shaft or the clamp thingy, a few revolutions and it might never grip properly again, I,ve known two taperlock bushes slip and even with new bushes I was never quite happy with the grip, mind you that is two over about 40 years and one was my fault for re using an unknown old one and the other was in a terrible old springer with an awful installation.

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On 13/12/2017 at 09:59, Mike the Boilerman said:

 

A flexible coupling is a lot better than none but not quite what I meant.

If a prop jam occurs stopping the engine dead, the energy that bends the prop is the kinetic energy present in the rotating engine flywheel, crankshaft etc, rather than the basic engine power which just pushes the boat along. 

Consequently, a truly massive instantaneous force gets transmitted along the prop shaft at the instant of the jam and a coupling which can slip under this extreme stress is a Very Good Thing and might well save the prop from getting bent. Think of it as is the mechanical equivalent of a fuse in an electrical circuit. 

A 'slip joint' in a propshaft in its simplest form would be a plain shaft clamp coupling with the woodruffe key taken out and the clamp bolt tightened sufficiently to grip during normal operation but not tightly enough to continue to rigidly grip in the event of a prop jam. 

Edit to add:

A 'friction joint' might be a better term for what I'm suggesting.

I seem to remember an outboard engine I had years ago had a shear pin, which was designed to break under a shock load and so isolate the prop from the gearbox/engine if the prop was fouled. Such an arrangement inboard of the stuffing box would provide the same service in a narrow boat, and the drive could be reinstated without having to get wet. I imagine it would be quite difficult to set it up so as to avoid false alarms every other bridgehole and I don't think I've ever seen one on the cut. Has anybody else?

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