Replace bottom bracket on O’Brien -Sapphire

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Philip Benstead
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Replace bottom bracket on O’Brien -Sapphire

Postby Philip Benstead » 29 Jul 2020, 6:31pm

O’Brien -Sapphire

This bike as a steels 2 pieces chain set, it requires a what appears a push fit bearing insert on the non-drive side; see photographs
is it possible to replace the steel chainset and 2 pieces bottom bracket with an alternative modern set up?

The BB shell dimensions are:
70mm wide and
35mm internal diameter on the non-insert side.

BTW
Does anybody have any knowledge of this frame builder?
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Philip Benstead | Life Member Former CTC Councillor/Trustee
Organizing events and representing cyclist in southeast since 1988
Bikeability Instructor/Mechanic

alexnharvey
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Re: Replace bottom bracket on O’Brien -Sapphire

Postby alexnharvey » 29 Jul 2020, 8:57pm

I think that's a Thun Thompson BB.

Valbrona
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Re: Replace bottom bracket on O’Brien -Sapphire

Postby Valbrona » 29 Jul 2020, 9:06pm

Now you know why it ended up in the skip.
I should coco.

Brucey
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Re: Replace bottom bracket on O’Brien -Sapphire

Postby Brucey » 29 Jul 2020, 9:12pm

yep. To modernise, a SunRace ST BB might work for you, provided you can use a 127mm length spindle; it appears to be the only ST spindle length which is readily available in this fitting

https://www.dutchbikebits.com/sunrace-cartridge-bottom-bracket

BBs of this type are standard fodder on zillions of cheaply made bikes as found on the continent. Little more than a PITA in the UK, because you can't easily buy the parts.

BTW the frame does look short on redeeming qualities...

cheers
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Philip Benstead
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Re: Replace bottom bracket on O’Brien -Sapphire

Postby Philip Benstead » 29 Jul 2020, 10:01pm

Brucey wrote:. . . . <snip> . . . . BTW the frame does look short on redeeming qualities..

WHY DO YOU SAY THAT?
I was given this bike for free , the reason I need it , is for my friend who as problems with her hip, she is unable to get her leg over the saddle, crossbar.

This bike has low step though.

My idea if she it suitable for her use I would I replace as much of the steel parts with modern alloy bits including an alloy cotterless chainset.
So, my question is any cotterless bottom brackets available that would fit.
Last edited by Graham on 30 Jul 2020, 5:36pm, edited 1 time in total.
Reason: Bad form to mash up a quote
Philip Benstead | Life Member Former CTC Councillor/Trustee
Organizing events and representing cyclist in southeast since 1988
Bikeability Instructor/Mechanic

Brucey
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Re: Replace bottom bracket on O’Brien -Sapphire

Postby Brucey » 29 Jul 2020, 10:06pm

why do I say that? Because it looks very cheaply made and will probably ride like it has a hinge in the middle.

By the time you have built that you could probably have bought a better bike with a lower step through...?

cheers
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bgnukem
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Re: Replace bottom bracket on O’Brien -Sapphire

Postby bgnukem » 30 Jul 2020, 5:25pm

Looks like a fatigue failure waiting to happen, no bracing of the down tube where it contacts the seat tube/bottom bracket at all!

Even for a step-through, that looks to be an appalling design.

Looks like the BB question has been answered though :D

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Philip Benstead
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Re: Replace bottom bracket on O’Brien -Sapphire

Postby Philip Benstead » 30 Jul 2020, 5:53pm

bgnukem wrote:Looks like a fatigue failure waiting to happen, no bracing of the down tube where it contacts the seat tube/bottom bracket at all!

Even for a step-through, that looks to be an appalling design.

Looks like the BB question has been answered though :D


There is the reinforcing bit on the top of the down tube/seat tube . I asume you may think it should be position underneath.

All this bike will be used forsome gentral ride on the flat to see if the ride can cope with a step though. It will only me some new cables and elbow grease,

Then I may pass it on for people to learn to balance.
Philip Benstead | Life Member Former CTC Councillor/Trustee
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Bikeability Instructor/Mechanic

tatanab
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Re: Replace bottom bracket on O’Brien -Sapphire

Postby tatanab » 30 Jul 2020, 6:17pm

Philip Benstead wrote:Does anybody have any knowledge of this frame builder?
Not a frame builder as such, just a brand of cheap bikes sold through mail order catalogues in the 1970s. Catalogues that your mum probably had such as Kay's and Littlewoods.

Brucey
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Re: Replace bottom bracket on O’Brien -Sapphire

Postby Brucey » 31 Jul 2020, 2:25pm

Philip Benstead wrote:I was given this bike for free....

…..My idea if she it suitable for her use I would I replace as much of the steel parts with modern alloy bits including an alloy cotterless chainset....


Philip Benstead wrote: ….All this bike will be used forsome gentral ride on the flat to see if the ride can cope with a step though. It will only me some new cables and elbow grease....


change of plan then...?

I think that not spending money on this before the intended user tries it out makes most sense. In fact I probably wouldn't have bothered to take the bike apart, I'd have just made it rideable for a test ride and only bothered doing more if it was deemed suitable.

Although the frame is cheaply made (with the most flimsy-looking chainstays I have seen in a long time...) it might be adequate for the intended user. However the step through isn't that low (it wouldn't be difficult to find one lower, I would have said). IME once a need for a low step through is identified, it is most often an ongoing requirement that the step through is made lower and lower. If that might be the case I would suggest that a much lower step-through would make most sense if the bike is to be a long-term purchase; one that is only just low enough now will very likely prove 'not low enough' sooner rather than later.

cheers
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Philip Benstead
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Re: Replace bottom bracket on O’Brien -Sapphire

Postby Philip Benstead » 31 Jul 2020, 2:35pm

Brucey wrote:
Philip Benstead wrote:I was given this bike for free....

…..My idea if she it suitable for her use I would I replace as much of the steel parts with modern alloy bits including an alloy cotterless chainset....


Philip Benstead wrote: ….All this bike will be used forsome gentral ride on the flat to see if the ride can cope with a step though. It will only me some new cables and elbow grease....


change of plan then...?

I think that not spending money on this before the intended user tries it out makes most sense. In fact I probably wouldn't have bothered to take the bike apart, I'd have just made it rideable for a test ride and only bothered doing more if it was deemed suitable.

Although the frame is cheaply made (with the most flimsy-looking chainstays I have seen in a long time...) it might be adequate for the intended user. However the step through isn't that low (it wouldn't be difficult to find one lower, I would have said). IME once a need for a low step through is identified, it is most often an ongoing requirement that the step through is made lower and lower. If that might be the case I would suggest that a much lower step-through would make most sense if the bike is to be a long-term purchase; one that is only just low enough now will very likely prove 'not low enough' sooner rather than later.

cheers


I was not rideable and now I find the SA is freewheeling both ways .

I always want to service a SA now my chance.

I take your points , the user need a hip operation
Philip Benstead | Life Member Former CTC Councillor/Trustee
Organizing events and representing cyclist in southeast since 1988
Bikeability Instructor/Mechanic

Brucey
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Re: Replace bottom bracket on O’Brien -Sapphire

Postby Brucey » 31 Jul 2020, 2:47pm

FWIW one of my neighbours was riding their bike a year ago, in some difficulty with the step through because they really need a knee operation. They pretty much gave up using their bike pending getting another (lower) one, which has taken longer than anticipated.

The net result is that between further deterioration (which would have happened anyway I expect) and the 'if you don't use it you tend to lose it' syndrome, a year later they now need a step-through which is about 1/3 the height of the one that was only just too tall before. It can slip away in a blink of an eye, more or less.

cheers
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kangaroo
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Re: Replace bottom bracket on O’Brien -Sapphire

Postby kangaroo » 31 Jul 2020, 3:43pm

I can't be the only one who finds this quite alarming. The idea of popping someone (possibly elderly, with mobility issues and maybe with little cycling experience) on a bike with an iffy frame and a faulty transmission sounds like a recipe for disaster. She may well end up needing more than a hip replacement. Can't you simply borrow a bike with a frame similar to one she may be able to buy either to use now or for post-surgery (she may well still need a step-through frame) and assess its suitability?

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Philip Benstead
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Re: Replace bottom bracket on O’Brien -Sapphire

Postby Philip Benstead » 31 Jul 2020, 9:44pm

kangaroo wrote:I can't be the only one who finds this quite alarming. The idea of popping someone (possibly elderly, with mobility issues and maybe with little cycling experience) on a bike with an iffy frame and a faulty transmission sounds like a recipe for disaster. She may well end up needing more than a hip replacement. Can't you simply borrow a bike with a frame similar to one she may be able to buy either to use now or for post-surgery (she may well still need a step-through frame) and assess its suitability?


The person with the hip problem is my female friend who is 72. She been riding a bike since a child and has done 100 miles on a bike.

The bikewas obtain from a ex long standing CTC Councillor.

Before my friend rides it I will test it out, and we will be riding slowly on the flat.
Philip Benstead | Life Member Former CTC Councillor/Trustee
Organizing events and representing cyclist in southeast since 1988
Bikeability Instructor/Mechanic

Ugly
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Re: Replace bottom bracket on O’Brien -Sapphire

Postby Ugly » 6 Aug 2020, 6:26pm

I have done a search for Thompson bottom bracket parts and there are a few out there that would take cottered cranks, or you could just use the missing bits. I have recently picked up a bike fitted with a Shimano Thompson style double chainset.