How to get the right prop?

[ditchcrawler]

3 minutes ago, jennywren said:

All the good ideas have giving me the confidence to I have a go at a few options to try and fish prop out (will give local diving club a try, if no luck there thinking purchasing an inflatable dinghy and something to poke about with would do the trick at least to locate it). Having thought over my entrance to the lock and attempt to slow down, I can narrow down where it will be to a quarter of the lock so it's not a massive area to search over so fingers crossed will get lucky.

Will let you know how I get on...

As I said if you borrow a long shafted crome from CRT you can just rake the bottom until you find it and probably lift it to the surface as well.

[bargemast]

10 hours ago, Mike the Boilerman said:

 

So not so difficult after all to establish the clearance. I've also done it with a tape measure down the weed hatch.

Fundamentally I agree with you finding the old one is worth quite a lot of effort but if the OP is not inclined, there are two approaches. 

1) Tell us the engine and a few details of the boat and someone here will almost certainly have one approaching suitable lying around which will get the boat moving again, possibly even today. Prop specs are very uncritical if you just want to get on with your trip. As long as the prop is small enough actually rotate!

2) Specify it properly and order a new one the exact right size. Crowthers will take a few days to come up with one.

The taper is pretty must standard. 1:1- or 1:12. One is FAR more common than the other so a roughly correct second hand blade will almost certainly fit the shaft. The harder bit will be finding a nut to hold it on and inserting a locking pin. The boat will need docking for this in my opinion, regardless.

Hi Mike, I'm pretty sure that you wanted to write 1 : 10 or 1 : 12  for the taper, as 1 : 1  is what a reverse gearbox for a very slow revving engine may have, but never for a taper.

 

Peter.

Edited June 14, 2017 by bargemast

[MtB]

2 minutes ago, bargemast said:

Hi Mike, I'm pretty sure that you wanted to write 1 : 10 or 1 : 12 for the taper, as 1 : 1 what a reverse gearbox for a very slow revving engine may have, but never for a taper.

 

Peter.

 

Ah the perils of posting using a tiny phone screen. 

Yes I meant 1:10 or 1:12 taper. One is common in the UK, the other is common in the USA I gather. I can't remember which is which though.

[bargemast]

2 minutes ago, Mike the Boilerman said:

 

Ah the perils of posting using a tiny phone screen. 

Yes I meant 1:10 or 1:12 taper. One is common in the UK, the other is common in the USA I gather. I can't remember which is which though.

On my side of the Channel, the most common is 1 : 10.

Happy to be able to use the keyboard of my laptop again, after a good (bad)  week on my phone.

Peter.

[MtB]

Ok just measured the taper in one of the blades I have here, and its 1:12.

It was on my boat for a while so I know the taper on that prop shaft must be 1:12 !

Hmmmm just measured the taper on another blade I have and its 1:10...

[MtB]

Ok and the third one I have here is...

1:12!!!

[nicknorman]

1 minute ago, Mike the Boilerman said:

Ok and the third one I have here is...

1:12!!!

The problem is that if you don't know what you are doing, it would be all too easy to fit a prop with the wrong taper. It would work ... for a bit!

[David Mack]

1 hour ago, jennywren said:

Having thought over my entrance to the lock and attempt to slow down, I can narrow down where it will be to a quarter of the lock so it's not a massive area to search over so fingers crossed will get lucky.

Will let you know how I get on...

If the prop was spinning in reverse when it came off it will have propelled itself further back, so be prepared to extend your search area behind the point where it came off.

[Jess--]

4 minutes ago, David Mack said:

If the prop was spinning in reverse when it came off it will have propelled itself further back, so be prepared to extend your search area behind the point where it came off.

Having felt how close my prop is to the leading edge of the rudder I often wonder how (with the rudder straight) it is possible to totally lose a prop.

I can understand it slipping back on the taper and hitting the rudder (leaving the shaft turning nothing)

[rusty69]

On 14/06/2017 at 17:15, jennywren said:

Will let you know how I get on...

Did ya recover it? 

[Mikexx]

On 13/06/2017 at 16:55, jennywren said:

So, this is the brilliant thing that happened to me today; my propeller fell off. My guess would be the pin holding it on came loose somehow, allowing it to simply unscrew itself and drop off.

Coming out of a lock and realised suddenly I had no drive. Check prop shaft and gearbox coupling because that's what I've had problems with before and have been worrying about. Nope-all fine. Put my hand down weed hatch and tah-dah...propeller gone. As an afterthought, boat did not reverse when I tried to slow into the lock, so suspect I either lost it just before or actually in the lock. I can't imagine there's much hope of fishing it out again-water a good depth and really murky outside lock and can't exactly go fishing in a lock for it, and no idea of more precisely  may have lost it.

 

I know this was over a week ago but only just seen this thread.

Has anyone thought of an underwater camera? Something like:

  http://www.ebay.co.uk/itm/Pyle-PSCHD90SL-Hi-Res-Action-20-Mega-Pixel-Camera-Full-HD-Video-2-LCD-Wi-Fi-/351949917255

Just a thought!

[jennywren]

Update: Spent the last week trying various methods and unfortunately not recovered original propeller, so I guess it is onto trying to source a second hand prop (I cannot afford a new one currently).

I don't know if my engine is much help in finding a prop (I have a Perkins 400 series- 403C-11).

I've done a few rough measurements through the weed hatch for the clearance and think 12 inch span is what's needed. Need to check measurements for taper still, only really had a quick poke about (before accepting I was not likely to find my lost prop) so need to go back and do some more accurate measurements (and I'm not on boat today so it'll have to wait).

[MtB]

9 minutes ago, jennywren said:

Update: Spent the last week trying various methods and unfortunately not recovered original propeller, so I guess it is onto trying to source a second hand prop (I cannot afford a new one currently).

I don't know if my engine is much help in finding a prop (I have a Perkins 400 series- 403C-11).

I've done a few rough measurements through the weed hatch for the clearance and think 12 inch span is what's needed. Need to check measurements for taper still, only really had a quick poke about (before accepting I was not likely to find my lost prop) so need to go back and do some more accurate measurements (and I'm not on boat today so it'll have to wait).

 

I suspect by 'span' you mean radius measured from the prop shaft taper out to the nearest obstruction, probably the skep and/or the uxter plate. Both are probably about 12" away. 

Allowing a couple of inches for clearance this gives us a radius of 10", equal to a blade diameter of 20" max. Is it an 'ordinary' steel narrowboat? If so this is a reasonable diameter blade to have been fitted previously.

One on ebay nopw for £120 that would do to get you around...

http://www.ebay.co.uk/itm/Large-Boat-propeller-boat-prop-brass-bronze-propeller-19-x-16-5-for-1-5-Shaft-/382097170739?hash=item58f6c42133:g:fSsAAOSwsXFZJEfk

[Alan de Enfield]

3 minutes ago, Mike the Boilerman said:

One on ebay nopw for £120 that would do to get you around...

But without knowing the boats shaft size and taper - it could be £120 wasted.

Ideally the 'questions' need answering before any prop is purchased.

[MtB]

4 minutes ago, Alan de Enfield said:

But without knowing the boats shaft size and taper - it could be £120 wasted.

Ideally the 'questions' need answering before any prop is purchased.

 

Indeed. The OP knows about the need for the taper to match. And the propshaft diameter. The direction of rotation needs to be correct too, and this hasn't been mentioned yet.

Four things to be established:

Diameter
Pitch
Taper
Direction of rotation in ahead gear. RH blade (turning clockwise looking forward from behind the boat) or LH (anticlockwise) 

[bargemast]

50 minutes ago, Mike the Boilerman said:

 

Indeed. The OP knows about the need for the taper to match. And the propshaft diameter. The direction of rotation needs to be correct too, and this hasn't been mentioned yet.

Four things to be established:

Diameter
Pitch
Taper
Direction of rotation in ahead gear. RH blade (turning clockwise looking forward from behind the boat) or LH (anticlockwise) 

And how about the reduction of the gearbox, which can make the pitch requirements quite a bit different.

 

Peter.

[Alan de Enfield]

43 minutes ago, bargemast said:

And how about the reduction of the gearbox, which can make the pitch requirements quite a bit different.

 

Peter.

Just as an example my engine specification gives the following options :

1)

Min Shaft Diameter = 1 1/2"

Max Prop Diameter with a 1.5 : 1 Ratio gearbox = 20"

Speed for this gearbox ratio = 13-25 Knots

 

2)

Min Shaft Diameter = 1 3/4"

Max Prop Diameter with a 2 : 1 Ratio gearbox = 25"

Speed for this gearbox ratio = 9-20 Knots

 

3)

Min Shaft Diameter = 2"

Max Prop Diameter with a 3 : 1 Ratio gearbox = 33"

Speed for this gearbox ratio = 6-12 Knots

 

No mention made of prop pitch.

 

[bargemast]

10 minutes ago, Alan de Enfield said:

Just as an example my engine specification gives the following options :

1)

Min Shaft Diameter = 1 1/2"

Max Prop Diameter with a 1.5 : 1 Ratio gearbox = 20"

Speed for this gearbox ratio = 13-25 Knots

 

2)

Min Shaft Diameter = 1 3/4"

Max Prop Diameter with a 2 : 1 Ratio gearbox = 25"

Speed for this gearbox ratio = 9-20 Knots

 

3)

Min Shaft Diameter = 2"

Max Prop Diameter with a 3 : 1 Ratio gearbox = 33"

Speed for this gearbox ratio = 6-12 Knots

 

No mention made of prop pitch.

 

The pitch will be left to calculate with all the information you have, by the prop makers.

Who btw could never do that without all this info.

For your engine the different specifications are for completely different boats, that only have the same engine in common.

The first is for a pretty fast and surely fairly light boat, and the third for something more like a heavier displacement (possibly a work) boat.

 

Peter.

Edited June 22, 2017 by bargemast

[jennywren]

6 hours ago, Mike the Boilerman said:

 

I suspect by 'span' you mean radius measured from the prop shaft taper out to the nearest obstruction, probably the skep and/or the uxter plate. Both are probably about 12" away. 

Allowing a couple of inches for clearance this gives us a radius of 10", equal to a blade diameter of 20" max. Is it an 'ordinary' steel narrowboat? If so this is a reasonable diameter blade to have been fitted previously.

One on ebay nopw for £120 that would do to get you around...

12" diameter is what I meant. It's a GRP cruiser so not a very big prop.

I'm keeping an eye on ebay but will be doing all those measurements at least twice-and did already know I needed to check whether it was LH or RH so that also-before I spend any money.

[Alan de Enfield]

8 minutes ago, jennywren said:

It's a GRP cruiser so not a very big prop.

Is it 'on a shaft' an outdrive, a 'leg' or an outboard. ?

[Rose Narrowboats]

The shaft is 1" diameter. The standard taper for imperial shafts is 1:12 (except Lister who used 1:10 just to be awkward).

Put the boat in forward gear and see which way the shaft turns - that will tell you which hand you need - almost certainly r/h.

1 minute ago, Alan de Enfield said:

Is it 'on a shaft' an outdrive, a 'leg' or an outboard. ?

No, it's a got a long shaft from a centre cockpit engine/gearbox with the shaft sloping down and running out through a conventional stern gear bonded into a shallow keel.

[Alan de Enfield]

5 minutes ago, Rose Narrowboats said:

The shaft is 1" diameter. The standard taper for imperial shafts is 1:12 (except Lister who used 1:10 just to be awkward).

Put the boat in forward gear and see which way the shaft turns - that will tell you which hand you need - almost certainly r/h.

No, it's a got a long shaft from a centre cockpit engine/gearbox with the shaft sloping down and running out through a conventional stern gear bonded into a shallow keel.

I presume you know the boat.

 

All that had been mentioned in the thread was that it was a Perkins engine - we had all assumed that it was a shaft drive but it was not confirmed.

[john6767]

9 minutes ago, Rose Narrowboats said:

The shaft is 1" diameter. The standard taper for imperial shafts is 1:12 (except Lister who used 1:10 just to be awkward).

Put the boat in forward gear and see which way the shaft turns - that will tell you which hand you need - almost certainly r/h.

No, it's a got a long shaft from a centre cockpit engine/gearbox with the shaft sloping down and running out through a conventional stern gear bonded into a shallow keel.

Ah, is this the boat that was broken down at your place when we dropped Firefly off.  Double bad luck.

[Rose Narrowboats]

4 minutes ago, Alan de Enfield said:

I presume you know the boat.

 

All that had been mentioned in the thread was that it was a Perkins engine - we had all assumed that it was a shaft drive but it was not confirmed.

Yes, we repaired the previous drive problem the boat had a couple of months ago.

[blackrose]

On 2017-6-14 at 08:34, Alan de Enfield said:

It is of absolutely no help to the OP, but having 'lost a prop' myself (some years ago)I have made up  small 'prop rescue kit' which could also be used to clear props which cannot be cleared via the weedhatch.

It gives me roughly 5-10 minutes of air (depending on depth, stress and exertion levels)

(Yes - I used to dive as a hobby)

 

 

Prop rescue kit? Blimey Alan, you really have thought of everything! I assume you have a good underwater diving torch to go with that?