Author Topic: Brompton Rear 3 Speed Hub Replacement  (Read 2154 times)

Brompton Rear 3 Speed Hub Replacement
« on: January 09, 2012, 01:36:24 PM »
Afternoon All

Re: Brompton Rear 3 Speed Hub Replacement
« Reply #1 on: January 09, 2012, 01:39:12 PM »
Lets start again......

I need to repalce my rear 3 speed hub on my Brompton. I don't really want to replace the whole wheel, just the hub.

Does anyone know where I can get a replacement Sturmey Archer S-RF3 rear hub with 28h as I'm not having a lot of luck with t'internet?

Many Thanks
Chris
 

rogerzilla

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Re: Brompton Rear 3 Speed Hub Replacement
« Reply #2 on: January 09, 2012, 06:01:46 PM »
What's wrong with it?  Personally I'd buy a lightly-used AW from eBay and transfer it into the SRF3 shell.
Never tell me the odds.

Biggsy

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Re: Brompton Rear 3 Speed Hub Replacement
« Reply #3 on: January 09, 2012, 06:14:20 PM »
Ask for a quote from any good Brompton dealer.  They should be able and willing to order any part from Brompton.

http://www.google.co.uk/search?q=Sturmey+Archer+S-RF3&hl=en&tbm=shop&aq=f&oq=&aq=f - Enquire to the dealers about the number of holes, or fit the innards of a differently-holed version to your existing shell if compatible.

293 goodies on eBay.  Will only take about 10 of your minutes to look through.  (Deliberately not a very specific search, because not all sellers write a precise or correct title and description).
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rogerzilla

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Re: Brompton Rear 3 Speed Hub Replacement
« Reply #4 on: January 09, 2012, 06:25:29 PM »
I wouldn't buy a new hub unless the rim was also worn out, in which case you might as well buy a complete rear wheel.  Too much effort to rebuild the wheel just for a malfunctioning hub.

The SRF3, although it is immune to slipping between normal and high gears, isn't as simple and reliable as an AW, and s/h AW hubs are far easier to find, many of them very lightly used*.  No need to change anything else as the SRF3 uses the same shifter, cable, adjuster, sprocket etc.  Older AWs were designed to run in oil, with an oiling point in the shell, but you can equally well smear the mechanism with SA internal hub grease (the brown runny stuff) and forget about it.

*a worn one is fine if you change the clutch and planet pinion pins for about £5.
Never tell me the odds.

Biggsy

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Re: Brompton Rear 3 Speed Hub Replacement
« Reply #5 on: January 09, 2012, 06:35:46 PM »
Perhaps it's unfair to base the judgement on how bad AWs can be, on poorly maintained bikes, but my memories of slipping AWs are so vivid that I'll be sticking to SRF3s and recent AWs, myself.

(Purple text added after reading Roger's info below).
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rogerzilla

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Re: Brompton Rear 3 Speed Hub Replacement
« Reply #6 on: January 09, 2012, 09:21:20 PM »
The "N.I.G." AW made from some time in  the 1990s onwards can't slip, and is basically the same design as the SRF3 inside.  In order to achieve this, though, SA added a third set of pawls and a Heath Robinson metal shroud to trip them out when not required.  This tends to come loose and rattle, plus an SRF3 in an alloy shell is actually heavier than an old AW in a steel shell.

There are three rules to avoid old (non- N.I.G.) AW slippage:

1. Make sure the cable is adjusted properly (and that you have the correct length indicator spindle)

2. Don't stand on the pedals in high gear.  This is no problem on AMs and FWs, but don't trust an AW.

3. At high mileage, or if there are any hints of slippage with a correctly adjusted cable, change the clutch and planet pinion pins to eliminate the wear which facilitates slippage.

The problem is a combination of a "neutral" between normal and high gear and the way that the clutch engages the planet cage in high gear - through extended planet pinion pins.  This probably seemed like a good idea in the 1930s because it was cheap to replace these as service items when they got worn (other hubs use trapezoid dogs on the face of the planet cage) but the load-bearing surfaces are very small and the pins can also lean a bit (they're a fairly loose fit in their holes), helping the clutch to squirm off.  With new parts it takes a gorilla to achieve slippage, but with worn parts your gran could do it.
Never tell me the odds.

Re: Brompton Rear 3 Speed Hub Replacement
« Reply #7 on: January 11, 2012, 05:06:43 PM »
Thans very mcuh for your replies. I've no idea how long these hubs should last so am looking for a few pointers

I guess whats wrong witht he hub is that it's a little tired. Done probably about 10,000 miles. I've been told by two different shops that it would be easier to buy another complete wheel but am loathed to do so because of both the cost and seemingly a bit wasteful just to chuck the whole lot out and start again. I know the axle is bent and when riding you can feel the internals grinding even though the cable seems to be adjusted correctly.

Looking at SJS earlier I see you can buy the internals as a unit which is possibly the most straightforward way to go for me. Alternatively I guess I could have a go at taking it to bits to have a look and try to asses what may need replacing. How easy is it to take to bits and reassemble? I'm not the most technically minded but looking at the diagrams on the Sturmey Archer website I reckon I could follow them.

Thanks for any tips.

Chris

rogerzilla

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Re: Brompton Rear 3 Speed Hub Replacement
« Reply #8 on: January 11, 2012, 06:43:56 PM »
What are the symptoms?  I can probably tell you what's wrong.  They never wear out totally unless they get full of water; certain parts wear and are designed to be serviceable.
Never tell me the odds.

Re: Brompton Rear 3 Speed Hub Replacement
« Reply #9 on: January 11, 2012, 08:40:06 PM »
There's play in the rear wheel as though the bearings are loose

First Gear - works ok but the hub really feels like it's grinding

Second Gear - again feels a bit rough. Freewheeling isn't smooth - alot of clciking and won't back pedal when you turn the pedals by hand.

Third Gear - works ok but doesn't feel smooth.

Gear cable is adjusted correctly.

Hope this helps

rogerzilla

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Re: Brompton Rear 3 Speed Hub Replacement
« Reply #10 on: January 11, 2012, 10:02:33 PM »
It sounds as if it has some sort of contaminants in there so yes, a new mechanism is the way to go.
Never tell me the odds.

Re: Brompton Rear 3 Speed Hub Replacement
« Reply #11 on: January 12, 2012, 12:56:06 AM »
Got to make sure the axle length is correct, whatever the brompton version uses.

rogerzilla

  • l33t h4X0r
Re: Brompton Rear 3 Speed Hub Replacement
« Reply #12 on: January 12, 2012, 07:16:31 AM »
Any SA hub with a 5 3/4" axle is correct.  That's the shortest and most common length.
Never tell me the odds.

Re: Brompton Rear 3 Speed Hub Replacement
« Reply #13 on: January 12, 2012, 11:07:19 AM »
Thanks for your help

I think I'll go for the complete mechanism and have a play around with the old one to work out how to maintain it in the future.

Thanks again.