Cutless Bearing, advice, if you please

[Jegs]

Good Morning,

A bright & sunny one on the north downs - I hope yours is the same.

I am planning to buy replacement bearings for our steel boat & would appreciate some guidance. Brass being forbidden, there appear to be phenolic or fibreglass versions available or are there others? On the basis that its phenolic or fibreglass, my thought was that grp should not be left in water for years at a time & even if the boat is ashore for some time every year the material could not dry out in such a location. Which appears to leave phenolic & that gives rise to a another query; the bearings are supplied in standard lengths & one would need to shortened, is this a simple matter using a hacksaw or is a more delicate method required?

The reason I am not simply asking the yard where the boat will be lifted is because it is in France & my French may be most kindly described as imperfect.

Hopeful thanks,

John G

 

[akyaka]

Do you know/have ascertained what your existing bearing is made of . Ours , admittedly on a GRP boat, are made from white metal poured into the casting .

 

[Tranona]

The convention is that the bearing length is 4 times shaft diameter. So 6" long for a 1 1/2" shaft. Bearings are made to standard lengths but no reason why they cannot be cut down. However before you order you need to know the exact diameter of the shaft and the diameter of the tube. Non metallic shell material is readily available as are composite bearings machined to suit your combination of tube and shaft.

 

[BabaYaga]

the bearings are supplied in standard lengths & one would need to shortened, is this a simple matter using a hacksaw or is a more delicate method required?

A hacksaw should be no problem, I have used one to get the old (phenolic) bearing out and to take 15mm off the (brass) replacement.

 

[Jegs]

Thank you for your interest. I do not know what the current bearings are made of but the boat builder has stated non-metallic & supplied the dimensions for two bearings, one 160mm long & the other 78mm - hence my query relating to cutting the phenolic cased type. I have found both grp & phenolic types on the net so my query related the suitability of either type & ease of cutting. I apologise for my lack of clarity.

Many thanks,

John G

 

[Neil_Y]

We supply marine shaft bearings any size, just tell us the shaft OD and the carrier ID and what length you want. There are no standard sizes, although we have mandrils for the common shaft sizes. These are phenolic composite bearings not rubber.

The bearings you are referring to are rubber bearings in a composite sleeve, the composite being grp or fibre reinforced phenolic. Both of these materials swell with moisture over time so an allowance is made on the clearance.

Bearings can be made to suit a press fit or bedding on epoxy, a press fit bearing will come with a larger ID, greater clearance as the bearing will see some bore closure if it is pressed in with an interference fit. We normally prefer a clearance fit (0.05 - 0.15mm) with the ID finished to the exact clearance on the shaft.

That's probably just confused you more now.

But we can supply any length (up to around a metre) and you only pay for what you buy so there is no wastage.