Metaler....metali........metalerg.......Who knows about metal?

[BarryH]

Bit of an issue with the 'ol volvo drive. First noticed it last sunday. Basically bush in the steering helmet has worn. Not a prob machining it out and replacing it. I'm not gonna pay dealer prices not that a dealer would have one!

So making one is not a prob. Dunno what the old bush was made of but it sat in allyminyum and had a stainless spigot running in it. What would be the best metal to make it out of. Got to be hard enough not to wear away, not make the drive dissolve. Was thinking of stainless but its a bit of a pig to work with.
What would you make it out of bearing in mind the metals around it, ally/stainless?

 

[tcm]

Not utter expert, but i would say you will be ok with some variant of bronze. This is often used as a bearing material and obv good in seawater. It should actually wear a bit more than the stainless - cos making a new bush is easy. I mean, the idea is that replaceable bearings go first, not the rest of the mechanicals.

 

[BarryH]

Bronze....seems fair enough. The original wasn't bronze, but I can see what your saying about the bush needing to wear rather than the spigot. Off to to stockholders then to rummage thru their scrap box.

 

[eyehavit]

Avoid stainless to stainless. Risk spalling/similar metal-to-metal pick-up.
Bronze OK. Composite bearing material OK
If rummaging through their scrap box doesn't work, check out www.maritexbearings.com

 

[TheoSr]

Don't use metal, use DELRIN or some other though plastic instead. Cheap, easy to machine, no electrolysis, no lubrication.
Keep smiling,
Theo

 

[VicS]

Re: Delrin

I think this is a sensible idea, although I have no experience of Delrin. But see here.
A tough plastic, I think you meant to say, sounds more sensible than bronze as surely bronze will cause severe corrosion of the aluminium, even worse than the effects of stainless steel. Copper based alloys are ok in contact with stainless steel but not mild steel or aluminium.

 

[tcm]

Re: Delrin

ok, then yep, some vair tough plastic/composite instead of bronze.

 

[halcyon]

Re: Delrin

Years ago we used Polypenco for a suspension bushes with very good results.
It is self lubricating and a resonable cost, Polypenco Nylon 66 - Nylatron GS
see www.farnellinone.co.uk, and do a search for above.
When machineing plastic remember it absorbs water so swells, make a allowence.

Brian

 

[cliff]

I believe the word you are looking for is METALLURGIST the definition of which is "a person who can tell a virgin blond from an old ore"
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[charles_reed]

Wot you\'re looking for is a metallurgist

who might be able to advise you as to what the material was.

However, as Volvo always make a deliberate design error to keep their customers on their toes, you might have found it and would be ill-advised to repeat the error.

A safe material out of which to make it is probably monel.

 

[cliff]

[ QUOTE ]
Bit of an issue with the 'ol volvo drive. First noticed it last sunday. Basically bush in the steering helmet has worn. Not a prob machining it out and replacing it. I'm not gonna pay dealer prices not that a dealer would have one!

So making one is not a prob. Dunno what the old bush was made of but it sat in allyminyum and had a stainless spigot running in it. What would be the best metal to make it out of. Got to be hard enough not to wear away, not make the drive dissolve. Was thinking of stainless but its a bit of a pig to work with.
What would you make it out of bearing in mind the metals around it, ally/stainless?

[/ QUOTE ]I would consider sintered Phospor-Bronze.
Stainless or monel could result in spalling and or wear on the spigot. Ideally you want the bush to wear first as it will be easier to replace.. Many outboards have P-bronze bushes in contact with aluminium alloy.

If concerned fit an anode to the housing / skeg /casing to protect not only the aluminium housing etc but also the bush.

All common engineering plastics absorb water and swell to some extent although if that is the route you choose I would contact your local Tufnol depot - NOT a Tufnol agent but Tufnol themselves for advice and possible an offcut of the most suitable material. Be careful when machining "Tufnol" type materials and keep dust onder control. Also make sure your tooling is correctly ground and sharp.
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[charles_reed]

Sintering

great if you've got the gear.

Tends to be a volume production technique

 

[TheoSr]

Re: Sintering

Sintered bronze bushing can be bougth off the shelf at least here in Holland. But I stick to my first suggestion to use an engineering plastic such as Delrin. I don't think it absorbs water but it is easy enough to cut a bushing lenghtwise to allow for some swelling. Tufnol is also good.
Keep smiling,
Theo

Oh, and never ever use stainless to run in stainless. I don't know the english word for it but it will seize.

 

[BarryH]

Its all a bit academic as I've now made a new one. I phoned volspec to have a chat with one of the spares chaps. Turns out it was a stainless sleeve/bush. Very helpful even tho they knew I wasn't going to buy anything. They said they'd find out and bell me back which they did.
Had some stainless tube knocking about the workshop. Half hour on the lathe and I'd knocked one up. Knackered a cutting tool in the process but they're 10 a penny anyway!

 

[roger]

limiting corrosion

Aluminium and other metals usually gives corrosion on boats.
You could try painting the bush before insertion with zinc chromate paste - minds gone blank - and recovered - Duralac is a convenient form of zinc Chromate.

 

[eyehavit]

Ultimately it is your call but conventional wisdom is not to allow a stainless steel shaft to slide against a stainless steel sleeve bearing, unless one of the parts has been specially surface treated. The reason why is simple enough and well known. Metal sliding against itself provides a mechanism to accelarate wear.

 

[BrendanS]

and which surface treatment would that be, and why is it simple enough and well known?

 

[eyehavit]

BrendanS
By simple enough and well known I was referring to untreated stainless steel sliding against itself in applications such as a sleeve bearing & shaft.
Surface treatment of stainless steel is neither simple nor well known outside of metallurgical circles, hence my use of the words specially treated. If you have a specific interest you are welcome to contact me.

 

[ongolo]

I dont know that volvo drive at all, but if in doubt, I would always make it from vesconite or somehing similar. Nylon swells a lot, but vesconite takes up almost no water , I seem to remember only 0.08% and thus does not swell much. Telfon I think, does not take up any moisture and does not swell at all.

Ongolo

 

[BarryH]

They way that I look at it is that Volvo spent enough on R&D and came up with the stainless bush. If they think its good enough then thats what I'll make a replacement from.
The bush and the spigot don't actually move aginst each other. The spigot comes off of the top gear housoing and the bush is in the steering helmet. Its there purely to transfer the turning forces from the steering helmet to the outdrive.
Yes there probably is better materials to make it from. Though from my point of view there is a ready supply of stainless to hand which costs me nothing. So I made it from stainless as that whats the original was made of. One more bit of stainless the size of an old 10p isn't going to make much difference as all the other fittings/fixings on the drive are stainless as well.