Fixed cup -bottom bracket advice

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MTruscott
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Joined: 8 Apr 2012, 4:22pm

Fixed cup -bottom bracket advice

Postby MTruscott » 8 Apr 2012, 4:35pm

I have a ten(?) year old Autralian Raleigh off which i am trying to remove the fixed cup. It is a bit odd as it looks on the outside to be a cartridge type as it needs a 20 spline tool in the same way as a shimano cartridge type.

So far I have broken my bottom bracket removal tool (which sheared off after I bolted it to the cup), and sheared a bolt after trying the Sheldon Brown method.

Does anyone with knowledge of this type of bottom bracket know if it could be threaded the other way and is there any way of telling? Are there any other suggestions for getting this off? I have of course used industrial quantities of penetrating oil....

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531colin
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Location: North Yorkshire

Re: Fixed cup -bottom bracket advice

Postby 531colin » 8 Apr 2012, 7:17pm

I would think if theres no lockring then it must be a left hand thread, or it would unscrew in use....but I have no experience of Australian bikes.

Actually, if its 10 years old it will be left thread anyway, the tooling will be the same as for frames fitted with unit BBs from new.....and this cheap BB is disguised (with splines) to look like a unit.

If you have broken a BB tool and sheared a bolt, it must be proper stuck.
An old-fashioned bike shop will have one of these

Image

which might get it out.

I have got them out by MIG welding a HUGE nut to the BB cup, gripping the nut in the bench vise and turning the frame....the heat probably helps!
An old friend used to give them a good crack with a cold chisel and about pound and a half hammer....if they are proper hard, they shatter.....good spectator sport!

Brucey
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Joined: 4 Jan 2012, 6:25pm

Re: Fixed cup -bottom bracket advice

Postby Brucey » 8 Apr 2012, 8:25pm

the few Aussie bikes I have seen have had left-hand threaded fixed cups just like British ones. Again like in the UK there were (I gather) a few Italianophiles in Australia who used Italian bike kit complete with their crummy self-undoing BB thread design, but my impression was that this accounted for one in a hundred racing bikes or something.

IIRC VP and others made loose ball BBKTs which used the splined tool of Shimano UNxx BBs to remove and install. The VP BBs in question mostly had a black finish to them and they rust in pretty well.

I would second Colin's suggestion of welding a big nut -or some other random lump of steel- to it and swinging like a chimp.

In one local bike shop to me they used to keep a MIG welder in the workshop which was used exclusively for this purpose.

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

MTruscott
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Joined: 8 Apr 2012, 4:22pm

Re: Fixed cup -bottom bracket advice

Postby MTruscott » 8 Apr 2012, 8:49pm

Thanks for the replies - I think you're right and I will need to come up with a smart way of inflicting violence on the thing. As I say, it's broken everything else...

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MLJ
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Joined: 15 Jan 2007, 11:48am
Location: Rugby

Re: Fixed cup -bottom bracket advice

Postby MLJ » 9 Apr 2012, 9:21am

Assuming it is a LH thread, all you need to free it is a large nut & bolt. Put this through the cup and then tighten it: doing so will loosen the LH thread.

MTruscott
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Joined: 8 Apr 2012, 4:22pm

Re: Fixed cup -bottom bracket advice

Postby MTruscott » 9 Apr 2012, 9:46am

MLJ wrote:Assuming it is a LH thread, all you need to free it is a large nut & bolt. Put this through the cup and then tighten it: doing so will loosen the LH thread.


I've tried this once - maybe a bigger bolt?

ANTONISH
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Re: Fixed cup -bottom bracket advice

Postby ANTONISH » 9 Apr 2012, 9:54am

Brucey wrote:
the few Aussie bikes I have seen have had left-hand threaded fixed cups just like British ones. Again like in the UK there were (I gather) a few Italianophiles in Australia who used Italian bike kit complete with their crummy self-undoing BB thread design, but my impression was that this accounted for one in a hundred racing bikes or something.

I have two Italian frames with Italian (36x24) bb's. I've never experienced a problem with them unscrewing.( I know you have more experience than myself). What I don't understand is why the Italians chose a mix of metric and imperial dimensions for their thread unlike the French thread which is consistently metric.

Brucey
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Re: Fixed cup -bottom bracket advice

Postby Brucey » 9 Apr 2012, 10:49am

ANTONISH wrote: I have two Italian frames with Italian (36x24) bb's. I've never experienced a problem with them unscrewing. What I don't understand is why the Italians chose a mix of metric and imperial dimensions for their thread unlike the French thread which is consistently metric.


its not guaranteed that the fixed cup will come loose but it is much more likely. Loctite normally sorts it out OK. ( 'Left-side drive' enthusiasts use loctite on their 'wrong way round' pedal threads and it seems to work OK for them too....)

The thread dimensions are an oddity indeed...

History probably provides an explanation; to this day there are all kinds of products that are made with a mixture of imperial and metric dimensions; car tyres for example.
When I go visit the local metals stockists, most of the stock there is in inch sizes to this day...

I think the explanation may lie in machine tools; all early machine tools cut threads in TPI and wouldn't do metric. Metric threading standards simply didn't exist in a useful form for a long time. I happen to own a good exemplar of this; I have a working lathe which was manufactured in Germany in 1892, a 'Pittler'. It is a treadle powered machine (although now it has an electric motor as well), and I gather that at one time these were so common that any machine-tool sweat shop might be dubbed a 'Pittlerie'. It has the novel feature that it can easily be used to machine cut tapered screw threads, something most modern lathes struggle to do. I was surprised to discover that it is entirely manufactured using inch dimensions and Whitworth screw threads. I later discovered that there was no DIN standard for screw threads until ~1915 and the one that was then ratified (at the height of WW1) was in essence a copy of the Whitworth standard, inches and all.

The Italian thread standard for freewheels and headsets is also an oddity in that it has a 55 degree flank angle where British threads have a 60 degree angle (the diameter and pitch are the same, and most people don't even notice and mix parts OK willy-nilly). The 55 degree angle is a straight hangover from the Whitworth thread standard...

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

ANTONISH
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Re: Fixed cup -bottom bracket advice

Postby ANTONISH » 11 Apr 2012, 11:36am

That's very informative Brucey. I used to work with an Italian engineer who waxed lyrical about the whitworth thread. Sad to see it go. :cry:

Brucey
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Joined: 4 Jan 2012, 6:25pm

Re: Fixed cup -bottom bracket advice

Postby Brucey » 11 Apr 2012, 12:35pm

ANTONISH wrote:That's very informative Brucey. I used to work with an Italian engineer who waxed lyrical about the whitworth thread. Sad to see it go. :cry:


me too. In theory the metric standards support a wide variey of thread pitches so can be tailored to suit nicely.... however this counts for little if you can't actually buy the bolts!

Eg... in my local fastener stockists I can still buy a wide range of whitworth, BSF, UNC, UNF,ANF, ANC etc etc nuts and bolts but I can't buy (say) M7x1 bolts at all easily and in stainless, not at any price....

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

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Steve Kish
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Re: Fixed cup -bottom bracket advice

Postby Steve Kish » 11 Apr 2012, 8:50pm

I did have a really nasty one a year or so ago. I have a 3/4-inch breaker bar and had to resort to Dremelling out a 3/4-inch square hole into the cup and then giving it some Schwarzenegger. I did get it out but such was the force needed that when trying to fit a new one, I found that I had bent the bottom bracket shell, thus knadgering the frame .... GRRRR! :evil:
Old enough to know better but too young to care.