The BSA A7-A10 Forum

Technical => Frame => Topic started by: Greybeard on 02.04. 2017 17:42

Title: This is strange
Post by: Greybeard on 02.04. 2017 17:42
I've just been getting intimately close to my beloved.  *loveit* The A10 that is! I've just washed and polished the whole bike and she looks spiffing. While doing the front wheel I noticed one spoke with some brown marks along its length. The spokes and rims are supposed to be stainless steel. I tried scratching the crud off the spoke with my finger nail but had to resort to steel wool. The brown marks have gone but have left behind what looks and feels like pitting, Aha methinks the bloke that did the wheels must have picked up a chromed steel spoke by mistake, (though I wouldn't have expected rust this soon); however a super strong magnet is not interested in clinging to that spoke so I don't think it's chromed steel. Any thoughts on this?
Title: Re: This is strange
Post by: morris on 02.04. 2017 18:27
Once more proof of the fact that great minds think alike... I also just finished treating the plunger to a polish.  *woo*

Spokes are not 100% stainless.
100% stainless is very brittle so will easily break under tension or when bent.
I don't know the exact composition of the alloy that's used for spokes, but suspect a high percentage of plain steel in them.
The brown spot you noticed may be some rust where there's some more plain steel in the alloy?
Title: Re: This is strange
Post by: Greybeard on 02.04. 2017 22:44
The brown spot you noticed may be some rust where there's some more plain steel in the alloy?
Bugger!
Title: Re: This is strange
Post by: WozzA on 02.04. 2017 23:52
Do you own a cat? they love spraying bike wheels..   *rant*

CRAP... I mean, it may be poo..  have you run over any livestock lately?
One easy test is smell your fingernail...   *eek*
Title: Re: This is strange
Post by: KiwiGF on 03.04. 2017 05:37
I've experienced stainless a fair bit at work, there are actually many grades of stainless available, some are magnetic (austenitic type), some are not, some grades are more resistant to corrosion than others, some machine better than others, some work harden quicker, my guess is that the spokes were made in a very low grade of stainless and will therefore rust fairly quickly in the presence of ordinary water, let alone water that contains road salt!

As an aside a bit of an "Achilles heel" with stainless is that most grades suffer from "stress corrosion" in the presence of chlorides eg salt, invisible cracks develop in certain ciircumstances, so for this reason alone one has to be careful to always select the best grade of stainless for a given application.

 I don't know enough to say what the correct grade of stainless would be for spokes  *doubt* but high on the list of requirements would be strength.



Title: Re: This is strange
Post by: BSA_54A10 on 03.04. 2017 10:40
Repeat after me;-
Stainless is not rustless.
Now go & write it 100 times on the blackboard.
There are lots of things that will "Stain", Stainless
Generally urine of any kind wont but lots of tree saps will
Title: Re: This is strange
Post by: Greybeard on 03.04. 2017 12:31
Repeat after me;-
Stainless is not rustless.
Now go & write it 100 times on the blackboard.
There are lots of things that will "Stain", Stainless
Generally urine of any kind wont but lots of tree saps will

I did not know that SS can rust. Just Googled the subject and found this: http://products.geappliances.com/appliance/gea-support-search-content?contentId=16654

As I've seen this on only one spoke I feel it's either some persistent crud or a faulty spoke. I'll go out in a minute with my maginifying glass and have a really good look.
Title: Re: This is strange
Post by: Greybeard on 03.04. 2017 17:36
...I'll go out in a minute with my maginifying glass and have a really good look.
I had a squint with a watchmakers eyeglass. Definitaly pitting on that spoke but no others. Strange!