Maritex prop shaft bearing? Any views?

[Philos63]

Hi
I need some advice and having searched the internet, thought somebody on this forum could maybe offer some.

I have a 36' steel hulled Koopmans, built in a small yard in Holland in 1991. I'm in the process of replacing a worn prop shaft and bearing. T Norris Marine in Isleworth are turning the new shaft but I'm struggling to find a supplier for the new bearing. I can't simply fit a new cutlass bearing as the design is slightly unusual. My vessel has a stern tube which is grease filled and the bearing is fitted to the outboard end - no water lubrication possible, so cutlass bearing not an option. The old bearing is a plain bronze bearing 70mm long with some channels milled into it for lubrication. It is press fitted into the end of the stern tube and held in with a 5mm setscrew. I'm looking at having an identical one made up. (Any suggestions as to who could do this would be welcome, as Im struggling to find an engineering shop locally, here in the wilds of Argyll.) Drawing attached.

Alternatively, I've come across Exalto (Maritex Composite Bearings | Exalto UK) who make and supply cutlass bearings. They also supply bearings in Maritex, a Lloyds approved material that claims to be longer lasting than other bearings and capable of being run dry and hot. Has anybody out there had any experience of Maritex and would be willing to share?

Thanks
Andy

 

[vyv_cox]

Hi
I need some advice and having searched the internet, thought somebody on this forum could maybe offer some.

I have a 36' steel hulled Koopmans, built in a small yard in Holland in 1991. I'm in the process of replacing a worn prop shaft and bearing. T Norris Marine in Isleworth are turning the new shaft but I'm struggling to find a supplier for the new bearing. I can't simply fit a new cutlass bearing as the design is slightly unusual. My vessel has a stern tube which is grease filled and the bearing is fitted to the outboard end - no water lubrication possible, so cutlass bearing not an option. The old bearing is a plain bronze bearing 70mm long with some channels milled into it for lubrication. It is press fitted into the end of the stern tube and held in with a 5mm setscrew. I'm looking at having an identical one made up. (Any suggestions as to who could do this would be welcome, as Im struggling to find an engineering shop locally, here in the wilds of Argyll.) Drawing attached.

Alternatively, I've come across Exalto (Maritex Composite Bearings | Exalto UK) who make and supply cutlass bearings. They also supply bearings in Maritex, a Lloyds approved material that claims to be longer lasting than other bearings and capable of being run dry and hot. Has anybody out there had any experience of Maritex and would be willing to share?

Thanks
Andy

Have a look at this page on my website Stern gear Next to bottom is a Maritex bearing in a similar application. The bottom one is mine that had a white metal bearing. It was replaced with Vesconite, similar to Maritex. Both successful modifications.

 

[scottie]

West of Scotland engineering Glasgow

 

[Norman_E]

Is that drawing correct? It seems to show a closed end.

 

[Philos63]

Is that drawing correct? It seems to show a closed end.

You're absolutely right! I was a bit too zealous in my 'hatching in'. Here's the modified drawing. Thanks for pointing it out - it might've been a bit problematic, trying to push a prop shaft through the first one.

 

[Philos63]

West of Scotland engineering Glasgow

Thanks. Will maybe give WOSE a try - although his quote to turn a new prop shaft (316 S/S, 1200mm x 35mm, 1 tapered end w/keyway and thread) was a bit steep, hence T Norris Marine.

 

[Philos63]

Have a look at this page on my website Stern gear Next to bottom is a Maritex bearing in a similar application. The bottom one is mine that had a white metal bearing. It was replaced with Vesconite, similar to Maritex. Both successful modifications.

Thanks for the pointer - I've actually seen your website but hadn't made it as far as the last few pics. Good to know Maritex is up to the job as I feel that's the way I'm going. Exalto have come back with a reply from Maritex, stating that I could use it if the stern tube was water filled. Up to now, I've pumped enough grease into the stern tube that a few spots appear at the back of the bearing, and had assumed that this lubricated the bearing. Maritex have said that this wouldn't work with their material as it would run too hot(!?) The attached is a schematic of what I have on Philos. Although I now think the grease nipple may actually be over the packing.

 

[jim.howes]

Hi from the schematic your log is not quite like any standard type stern tube and its confused me . There is no bearing in the forward end of the log meaning the shaft relies on the packing in the stuffing box to act as a bearing and that's not correct, there should be a bearing to support the forward end of the shaft. The aft bearing is immersed in water all the time and i feel a cutlass bearing would do the job and yes the grease nipple is just to lubricate the packing in the stuffing box and not to fill the whole stern tube.

 

[captainboo]

I have a identical set up in that the rear bearing material is white metal and the front 'bearing' is the bronze material of the stuffing box housing just behind where the stuffing is inserted.

I initially thought that the greaser was to provide lubrication to the white metal bearing but as the grease mixture floats on water and exentually gets pushed out by the water flow dripping through the stuffing it never gets down to the rear white metal bearing. If I did fill the stern tube with grease to get it to the white metal bearing then the stuffing box would run hotter due to no water flow.

Now that the stuffing is adjusted to the point that it only drips slightly when running and not when stopped I rarely touch the greaser and the rear white metal bearing has never worn. I did make sure that the shaft was correctly aligned to the gearbox to minimise and load on the front bearing.

There was a poster on this forum who worked for a company called H4 Marine who specialise in Maritex bearings and he advised me that if required the white metal bearing could be replaced by a thin Maritex shell epoxied in place if it ever wore out.

 

[Neil_Y]

A bit of an update as this thread popped up thanks to Google knowing what everyone is doing! Maritex is not similar to Vesconite, check the data on Vesconite. Maritex swells very little from moisture, expands very little with heat and does not melt or creep. It also remains hard even at failure. Grease used in tail shafts is not a great lubricant to choose as it does not conduct heat very well. Water is a great lubricant and also a great conductor of heat so water should be the preferred option. We have been working with Maritex on an even better composite for oil or grease that has metal in the matrix which will conduct heat better than the phenolic and fibre matrix used in Aquarius grade. We're doing testing now.