Sturmey Archer internals puzzle

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fenmanctc
Posts: 39
Joined: 15 Dec 2013, 10:10am

Sturmey Archer internals puzzle

Postby fenmanctc » 20 Dec 2020, 4:33pm

Hello, you knowledgeable people!
My question is this.I have rebuilt a Pashley Princess cycle which had been abandoned outside a flat in London for several years , but the only bits to have deteriorated beyond rescue were the basket and saddle. It’s only a 17.5 inch frame, but with a new overlong seat post I can happily ride it, although I’m over 6ft. The only thing I would like to change is the gearing. It has a Sturmey Archer X-RD3 rear hub and the ratios are rather wide, although the hub works faultlessly. On browsing eBay, I have found that Edinburgh Bike Co-op have new 5-speed internals for £90. My question is, will this block fit inside the X-RD3 casing or will I have to fork out £150 for a new hub and build it in? In your opinion, will this be worth doing, and is the 5 speed as reliable as the century old 3? Your advice will be valued. Thanks. PS did you know that the wheelbase of the Princess range is the same whatever the downtube length
Explains why Pashley have bolt-on seat stays!

Brucey
Posts: 42978
Joined: 4 Jan 2012, 6:25pm

Re: Sturmey Archer internals puzzle

Postby Brucey » 20 Dec 2020, 11:47pm

IIRC the only thing that is different between the Princess frame sizes is the length of the seat tube and the (bolt-on) seat stays; same wheelbase like you say.

The XRD3 hub uses the so-called 'NIG' 3s internals, so it isn't the 1936-on AW design inside that hub, but it does have the same ratios (3/4, 1.0, 4/3), i.e. +33% steps

5s internals are probably not going to help you because

a) none will fit in an X-RD3 hubshell (it is too short inside)
b) there are some older 5s versions which have the middle 3 gears closer together than a 3s, but this isn't all the hubs and the difference isn't huge; +33% increase in the 3s and about +27% in the 'sprinter' 5s models.
c) The X-RD5(W) hub was used in pashleys from 2009 to 2017, and this has the middle three gears spaced the same as the 3s hub.
d) 5s hubs are less reliable than 3s hubs, in most people's use.

The current (rotary shifting) 5s hub (RX-RD5) with 70mm drum brake has slightly closer-spaced ratios (+25% IIRC) but it also weighs an absolute ton. It is however what Pashley use in the current 5s models.

FWIW one of the things I really don't like about the Pashley Princess is the way the basket is supported at the front; the bracket will practically destroy the head tube if you give it a chance. I have rebuilt several basket supports of this type and made them much better; stronger and won't damage the head tube.

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

fenmanctc
Posts: 39
Joined: 15 Dec 2013, 10:10am

Re: Sturmey Archer internals puzzle

Postby fenmanctc » 21 Dec 2020, 7:54am

Hi Brucey
Thank you so much for this comprehensive reply. Having noticed your posts on IHGs in the past, I was hoping you’d pick this up.
Based on your advice, I’m going to stick with the sweet-running 3speeder and accept that I’ll have to spin at times in 2nd.
I found your observations on the basket interesting. I did attach an after-market wire basket for a while, but found the extra weight made the steering twitchy, so I fitted a non- standard rack after enlarging it’s bracket holes to allow me to use the seat stay bolts as anchorage points and found the resulting handling much more balanced. I’ve now removed the basket support. In any case I reckon the wind resistance of the standard Pashley huge basket must be off the scale. I live on the Fens, and this is important! Thanks again and have a good Christmas.

Brucey
Posts: 42978
Joined: 4 Jan 2012, 6:25pm

Re: Sturmey Archer internals puzzle

Postby Brucey » 21 Dec 2020, 10:15am

if you find you are spinning out in second gear then maybe a different rear sprocket could make the gears suit you better?

IIRC the rear sprocket on a princess is often around 21T. This means you can raise all the gears by fitting a smaller sprocket 20, 19, 18 etc.

The other option is to fit a much larger rear sprocket (which will need a longer chain too). This can turn gear 3 into a cruising gear which you will use more often, and is a good way of getting lower gears for hills (not that this should be a concern where you are). However there is problem with the latter route, being that a princess has a chaincase which can restrict the maximum sprocket size which can be fitted. But if you can fit a 24T sprocket (and I don't know if you can or not BTW) this will give you a gear three that is about half way between your current gear 3 and gear 2.

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

Stradageek
Posts: 855
Joined: 17 Jan 2011, 1:07pm

Re: Sturmey Archer internals puzzle

Postby Stradageek » 21 Dec 2020, 10:34am

I essentially went the Brucey route with my Pashley postie by fitting a 33T alloy chainset to bring all the gears down.

Gear three is now for cruising and I freewheel down hills. Getting rid of the old steel chainset also removed a fair bit of weight, however as the bike is hardly a lightweight this improvement is probably all psychological :D

SA_SA_SA
Posts: 2037
Joined: 31 Oct 2009, 1:46pm

Re: Sturmey Archer internals puzzle

Postby SA_SA_SA » 21 Dec 2020, 11:50am

I found toe clips mitigate the 33% jumps a bit.
------------You may not use this post in Cycle or other magazine ------ 8)

Carlton green
Posts: 1006
Joined: 22 Jun 2019, 12:27pm

Re: Sturmey Archer internals puzzle

Postby Carlton green » 21 Dec 2020, 2:20pm

It wasn’t always the case but I’m a three speed hub fan. I used to run a Sach 5 speed, which I very much liked, but they are no longer made. Decades ago I had a SA five speed, it wasn’t a positive experience so before discovering the Sach I reverted to derailleur gears for some time.

As has been said ‘the trick’ with the SA three speed is to gear it down such that 3rd is your normal cruising along gear - say 66” or maybe whatever you’d pick on a single speed bike. Coast down the hills, have a slightly lower gear for climbing and embrace the limitations together with the pluses of a three speed hub gear. My top speed is now obviously capped but I could ride my three speed all day (bar occasionally walking up some hills) and whilst my average speed is reduced a little (compared to a bike with more gears) it’s really not a major issue to me and doesn’t take away from the pleasure of the ride. Well that’s my take and experience but others might have happily found another course too.

fenmanctc
Posts: 39
Joined: 15 Dec 2013, 10:10am

Re: Sturmey Archer internals puzzle

Postby fenmanctc » 22 Dec 2020, 8:21am

Thank you all- it’s like having a panel of wise men permanently in your living room without the necessity of feeding them! I was about to bid on eBay for a Princess 5 speeder with a larger frame, but am going to follow your advice because a) An extra-long strong seat post replicates the bigger frame, as all the wheelbases are the same ie 44”, and b) The 3 speeder is as sweet as a nut and reminds me of my first bike, a used 1950s Triumph, I’m now 76, 6’2” and the Princess is a cracking town bike for me, very comfortable and roomy, clean and with good drum brakes.
My only question now is how much bigger can the rear sprocket go without fouling the chain case? I’ll have to do some careful measurements. I may even have to truncate the back of the chain case as per some Dutch bikes. I’d have trouble matching the cranks if I went small at the front.
Cheers John (fenmanbctc)

Brucey
Posts: 42978
Joined: 4 Jan 2012, 6:25pm

Re: Sturmey Archer internals puzzle

Postby Brucey » 22 Dec 2020, 2:42pm

FWIW if you want to do something clever, and have more closely spaced gears, you could think of fitting a BWR type driver in the 3s hub, with two sprockets, and running a 2s derailleur, so as to half-step the gears (much as Brompton do in their 6s setups). However this would involve fitting a derailleur of some kind; even if carefully chosen, and the chaincase is relieved at the rear (or replaced with a simpler chainguard instead), this wouldn't be that easy. You would probably end up running 3/32" chain and that would probably require a new chainring too.

FWIW with your hub, sprockets with 19 and 22T give almost perfect gear intervals;

http://ritzelrechner.de/?GR=SAAW&KB=46&RZ=22,19&UF=2111&TF=90&SL=2.6&UN=MPH&DV=gearInches

or 20 and 23T

http://ritzelrechner.de/?GR=SAAW&KB=46&RZ=23,20&UF=2111&TF=90&SL=2.6&UN=MPH&DV=gearInches

a 3T interval between sprockets is about right in the 18-24T sprocket range, but both 18-21 and 21-24 combinations give noticeably less even spacing.

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