Whitlock Cobra 4 - Steering "Flutter"

[kacecar]

Hi

My boat, a Sigma 362, has developed a slight steering "flutter" when under motor. I've tracked the problem down to wear on the Feather Key that locates the steering quadrant (the steering "rack") on to the downshaft. Naturally, I wish to replace that key but, having looked at quite a few potential suppliers on-line, it seems that replacement isn't as straightforward as I anticipated, because the key is of a non-standard size. The old one measures 10 x 10 x 30 mm. (The closest equivalents I can find are 10 x 8 x 30 and 16 x 10 x 30 - a lot of filing to be done on that one).

I've put the question to "whitlocksteering.com" but no answer so far (not a criticism - early days) and, as I am keen to make progress, would like to know if anyone here knows of somewhere that can, or might be able to, supply a suitable replacement. If not I'll look for a local engineering / machining business that could make me one up - haven't come across one so far.

Thanks.

 

[Fr J Hackett]

Here you go

Kennedy 10mm x 10mm x 300mm SQUARE KEY STEEL SELF COLOUR 4210100K | Cromwell Tools

 

[Minerva]

Here you go

Kennedy 10mm x 10mm x 300mm SQUARE KEY STEEL SELF COLOUR 4210100K | Cromwell Tools

That's mild steel - surely that will rust and seize up within a sailing season...?

 

[sailorbenji]

Here you go

Kennedy 10mm x 10mm x 300mm SQUARE KEY STEEL SELF COLOUR 4210100K | Cromwell Tools

30mm not 300mm

OP - you can buy 10x10mm stainless square bar stock, in a relatively short length, and cut off 30mm to suit. The round ends are not critical to the function.

 

[Fr J Hackett]

30mm not 300mm

OP - you can buy 10x10mm stainless square bar stock, in a relatively short length, and cut off 30mm to suit. The round ends are not critical to the function.

It may seem like a waste but at £8.63 it's not a huge amount and you can cut the 300mm down in fact you could make several keys

But if he thinks the slop is down to a badly fitting key it's in all likelihood that the keyway is worn and simply replacing the key will not cure that.

 

[Fr J Hackett]

That's mild steel - surely that will rust and seize up within a sailing season...?

It's the correct material for a key the clue is in the name, why would it rust? it's not exposed and a film of grease will protect it anyway.

 

[Motor_Sailor]

Metric sized keys are available in stainless. Just double check it is 10mm and not 3/8th (9.6mm)

Alternatively, stainless steel 10x10mm bar is readily available. Half a metre for about £10 in 2-3 days. Might need a little bit a final fitting with an oil-stone.

 

[Supertramp]

Lewmar might be able to help. I have emailed their support team in the past and they were clued up about what fitted what. The point about keyway wear is a good one. I might try with some stainless steel bar and see if there is more of a problem.

 

[geem]

Are you sure it is only the key that is worn? Often the keyway suffers similar wear

 

[penfold]

Why is it wearing? The quadrant should be gripping the stock firmly, is there something wrong with the clamping arrangement?

 

[kacecar]

Thanks for all the replies - sorry not to have been able to look earlier (a busy day).

Getting some 10 x 10 bar is a great idea - don't know why I didn't think of it. It is definitely 10mm that's required, not 3/8".

And thanks for the heads-up about wear in the keyway. I had already considered this and attempted to measure the keyways accordingly. However:

• I only have a small Vernier caliper so measurements are, roughly, to the nearest 5th of a mm;
• access for measurement of the keyway on the downshaft is limited, so measurement there is compromised.

The width of each of the keyways came out at just about 10mm, more or less dead on.

I'm confident the old key is worn as it shows signs of having been exposed to water at some point in its life and the width along its length varies from 9.74 to 9.90 mm at various points (all measured with a micrometer). So, I've decided to replace that worn key first, before doing anything else, because: it's the quickest and easiest fix to try and, if it doesn't work, I won't have wasted a great deal of time and money on it.

Penfold asks a good question about the clamping arrangement. I have indeed found, on a previous occasion, that the single bolt that clamps the two pieces together can, and does, come loose, but I'm not sure whether that is cause or effect. I suspect what has happened (over two decades) is that early water damage allowed wear to develop in the key and probably the keyways thereby by allowing some movement and the forces of propwash while under motor have gradually added to the wear such that the single bolt must eventually work loose. I also think that at some point the key has been removed from its slot and then replaced without first having removed any loose dirt (rust) from the slot, making the key sit a little higher than it should, thereby possibly compromising the clamping effect. I might know more once I've fixed the problem - hope so.

Thanks again for all your input.

 

[penfold]

If it's coming loose then either a nyloc nut or thread locking compound(low strength so it can be undone readily at a later date) is needed.

 

[cagey]

Not doubting your interpretation of fault, on my 362 exactly the same set up I eventually traced the fault to lots of small problems Worst was slightly worn trackrod ends on trailing link, if you discover this fault don’t buy replacements from lewmar instead take originals to motor factors and get identical parts for a fraction of the price.
Another fault I found that gave similar symptoms was bearing in bottom of ‘steering column/tube “, best way to replace I found was to remove entire steering assembly handy if you’re replacing track rod ends, again replacement from bearing factor.
Final thought, again found in process of tightening up the wheel response, is the meshing of crown and pinion, altered by shims behind wheel brake boss, careful they are delicate, whilst you are there perhaps check fit of pinion locating/support pin in body.
There is a handy Whitlock Cobra installation/repair sheet on internet, on Westerly owner’s club I think, if you can’t find it ask me and I’ll look for it and send it to you.
Just googled parts list and found really useful article from YM\PBO August 2010 probably has all you need
I have a Gori folding prop and find when first applying ahead the wheel gives a hell of a rattle as rudder aligns itself.
Best of luck.
Keith

 

[cagey]

Another thought, to cheaply and quickly test your thought about worn key, with centre punch put 3 or 4 dimples in key, not too deep to temporarily take up wear if it works then you know you’re right

 

[kacecar]

Thanks guys, all good things to consider.

Re the clamping bolt, it will be some threadlocker and carefully applied torque - that's what I used when I discovered it loose and it seems to work. I'm going to leave out the non-standard soft washer/seal this time as it's now dry in there.

I've been through all the other bits in the steering and all, including those points you mention Cagey, are in fine fettle. Only this feather key seems problematic.

I did not know about the three dimple trick. That is very useful - I'll give it a go. It probably also explains why there are already three such dimples in one side of the old key, although not on a side that takes lateral loads.

Thanks again.