The Blatt - another year on

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cycle tramp
Posts: 3531
Joined: 5 Aug 2009, 7:22pm

Re: The Blatt - another year on

Post by cycle tramp »

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Valbrona
Posts: 2694
Joined: 7 Feb 2011, 4:49pm

Re: The Blatt - another year on

Post by Valbrona »

Thanks.

And what brake levers are you using?

I almost switched to hub brake on my utility bike a couple of years ago, but was put of by the expense and the fact that I was told my current brake levers (that operate full sized V brakes), and which are integrated with the shifters, are not a satisfactory match for hub brakes.
I should coco.
iandusud
Posts: 1577
Joined: 26 Mar 2018, 1:35pm

Re: The Blatt - another year on

Post by iandusud »

cycle tramp wrote:
iandusud wrote:
Cycletramp, I do like your utilitarian bike. What gear range do you have?

Ian


Thank you :-) the current gear range is best described as narrow, (however the 5 speed gear did replace a 3 speed hub so perhaps it's all down to prospective) I currently am using another IRD freewheel (which I found in the shed, which has teeth; 13, 16, 20, 24, 28) with a 34 tooth chain ring it currently gives me 68, 55, 44, 36, 31.5 inches. If I ride with a group then I get left behind when the group uses larger gears to make the best of a headwind.
When I first built the bike I used a 38 tooth chain ring which gave me 76, 62, 49, 41, 35 inches. It suited group riding better, but it also meant with a 18 kg load I had to walk the bike up the hill where I live...
...Blatt 2(diet blatt? Son of blatt?) will not be a dedicated load carrier which means I can use a larger chain ring again


Out of interest as you are using derailleur gears rather than IHG why not fit say a 7 speed freewheel say 11-34 giving you an 80" top gear (ample in my books) and a 26 bottom gear?

Ian
Brucey
Posts: 44517
Joined: 4 Jan 2012, 6:25pm

Re: The Blatt - another year on

Post by Brucey »

cycle tramp wrote:... The rear wheel was spaced for a 7 or 8 speed freewheel, (rather than a freehub cassette) but was re-spaced for a 5 or 6 speed freewheel - although it meant I lost a couple of gears, it allowed for the rear hub to be more centrally placed along the axle, and allowed for a more equal spoke tension to be used, building a stronger wheel.
Hope this helps :-)


The spacing for a 7s freewheel would be different from the spacing for an 8s freewheel. The correct spacing for a 7s freewheel is very similar to that of a 6s freewheel, because 7s sprockets are spaced more closely than 6s. As Ian points out above a 7s freewheel could give you more range etc; the reasons a 6s one was used in the Supercommuter included that more gears/range were not required and that 6s indexing should go longer between being fiddled with.

The scope for redishing the wheel whilst retaining the same axle is limited by the fact that the X-RD axle is shouldered (where the cartridge hearings fit to it) so it cannot be shuffled sideways as you would be able to do in (say) a typical hub with cup and cone bearings. In the 'Supercommuter' build the hub was redished to a narrower OLN by taking spacers out on the RHS and adding a smaller amount on the LHS. The latter wouldn't really have been possible had the frame had thicker aluminium dropouts. SA make different axles but IIRC the alternatives are not as long, so at 135mm OLN there isn't that much wriggle room.

IME when building one of these wheels there is nearly always more dish than you would like to have; this means the tension balance is worse than you would choose. The options here are to use higher than normal (probably excessive) DS tension or to use threadlock on the NDS spokes. I've seen one of these hubs break on the DS, presumably through excessive tension. In the Supercommuter the rear wheel was built with normal tension but without threadlock on the NDS, in the anticipation that it might have to be added later. It soon became evident that it wasn't optional; the NDS nipples started to back out in use so threadlock had to be added retrospectively; the wheel has been fine since then.

Re brake levers; SA recommend their S80 model levers for their drum brakes. These are optionally available with a parking button etc. These levers have the correct pull/MA for drum brakes, cantis, roller brakes, and older caliper brakes. A while back I refurbished a couple of pashleys and at some point they had both been fitted with the wrong brake levers; the brakes were absolutely feeble as a consequence. On one machine the (Dia Compe) levers were convertible between V and canti pull, so it was just a matter of reconfiguring them. On the other machine I had to pony up for replacement levers.

If you have V-brake compatible combined brake levers/shifters I suppose you could use travel agents but the brake will be spongier. Some V-levers are made so that the cable shackle could be put in one of two places in manufacture. This means that you can sometimes convert the levers, but this requires drilling holes and re-riveting the shackles; there are fairly obvious dangers if your workmanship isn't perfect here, so I don't recommend this route unless you are 100% confident about it.

One of my mad ideas is to make longer versions of the brake arms on the brake plate, thus making the drum brakes compatible with V-levers. The same dangers exist of course, but the brakes should also be improved because the cable tension is reduced.

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~
iandusud
Posts: 1577
Joined: 26 Mar 2018, 1:35pm

Re: The Blatt - another year on

Post by iandusud »

Sorry I hadn't spotted the post explaining the respacing of the rear hub. However as you say Brucey a 7 speed freewheel would probably fit, with possibly a tad more spacing. Brucey are you suggesting that the hub flanges on these hubs are not strong enough? If not then I can't see why a suitably strong wheel couldn't be built for this bike, particularly as it sports big tyres, maybe with the use of single butted spokes if necessary.

Ian
Brucey
Posts: 44517
Joined: 4 Jan 2012, 6:25pm

Re: The Blatt - another year on

Post by Brucey »

iandusud wrote:….. Brucey are you suggesting that the hub flanges on these hubs are not strong enough? ….


strong enough for bad wheelbuilding and salt spray in service?

No...!

The problem is the tension balance in the rear wheel.

SA's own documentation for the X-RD

http://www.sturmey-archer.com/files/catalog/files/327/SPECIFICATIONS%20-%20REAR%20DRUM%20BRAKE%20HUBS.pdf

says 7s freewheels fit the X-RD 135mm OLN hub as standard, and the RH flange is 20.7mm from the centreline and the LH flange is 43.5mm from the centreline.

If you feed these numbers into a wheelbuilding calculator it predicts a 47% tension balance. This is a worse tension balance than is achieved in an 11s 'road' wheel.

Why so 'bad'? Well the RH flange is in a more or less 'normal' location but flanges are further apart than in many rear hubs. This normally makes for an inherently stronger wheel but the problem is that the NDS spokes have low absolute tension values in them.

If you have well-lubricated nipples then depending on the service conditions and other build details, you might need between 65kgf and 90kgf in the NDS spokes to make them reasonably proof against the nipples unscrewing. This means that you might end up with tensions NDS/DS of 65/138kgf or 90/191kgf if you rely on tension alone to hold the NDS nipples. ~140kgf is possible with some rims, but ~190kgf is enough to break nearly everything; rims, hubs, you name it. Many rims are limited to about 100kgf maximum tension before they are likely to crack in service.

This effectively means you need to use lower spoke tension and threadlock on the NDS nipples in most cases.

If you can shuffle both flanges just 2mm rightwards, this improves the tension balance by 7%. Every mickle makes muckle...

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~
cycle tramp
Posts: 3531
Joined: 5 Aug 2009, 7:22pm

Re: The Blatt - another year on

Post by cycle tramp »

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cycle tramp
Posts: 3531
Joined: 5 Aug 2009, 7:22pm

Re: The Blatt - another year on

Post by cycle tramp »

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cycle tramp
Posts: 3531
Joined: 5 Aug 2009, 7:22pm

Re: The Blatt - another year on

Post by cycle tramp »

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Brucey
Posts: 44517
Joined: 4 Jan 2012, 6:25pm

Re: The Blatt - another year on

Post by Brucey »

one of the issues with X-RD (and in fact any hub which uses a screw-on freewheel, pretty much) is if/when the axle is likely to break. I know of three or four SA X-RD axles which have broken; one was in a bike with an ill-advised singlespeed conversion (the chain unsurprisingly derailed off the HG sprocket and this bent the axle) and the others were fatigue failures on bikes that were regularly loaded. IIRC one forum member here has reported that his X-RD axle lasted only 10000 miles on his (loaded) touring bike. Another I know of was used for ~60000 commuting miles before the axle broke, and toted rear panniers every single day.

Even if the life is not exactly predictable, clearly these axles don't last forever, and being solid, if the axle breaks it is a show-stopper; you are walking home.

So the plan for the Supercommuter is to fit an 'outrigger bearing'; all the parts are ready and when the transmission has its next renewal it will be installed. My chum has become stronger since the bike was built, and very rarely uses the lowest gear (even though it is not that low) and also 'taps along' about one gear higher than he used to. The gearing is to be revised to reflect this; it'll be upped by 10% courtesy of a larger chainring.

I also have plans to install outrigger bearings on other similar hubs. A snag which I anticipate may crop up is that the outrigger bearing may not want to come out of the freewheel (even when strong magnets are used on it); if this happens then there are other options; e.g. the freewheel body can stay (just renewing the sprockets) or the freewheel body will have to be dismantled so that it can be gripped by other means, or the axle may be driven out rightwards (it should move a small distance at least), taking the outrigger bearing with it.

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~
cycle tramp
Posts: 3531
Joined: 5 Aug 2009, 7:22pm

Re: The Blatt - another year on

Post by cycle tramp »

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Jdsk
Posts: 24636
Joined: 5 Mar 2019, 5:42pm

Re: The Blatt - another year on

Post by Jdsk »

20211031_111659.jpg
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Jamesh
Posts: 2963
Joined: 2 Jan 2017, 5:56pm

Re: The Blatt - another year on

Post by Jamesh »

Great bike everyone needs a blatt

Steel frame, 26" wheels, deore gears, leather saddle.

Cheers James
iandusud
Posts: 1577
Joined: 26 Mar 2018, 1:35pm

Re: The Blatt - another year on

Post by iandusud »

Jdsk wrote: 31 Oct 2021, 11:52am 20211031_111659.jpg
Indeed a great utilitarian bike. I'm surprised that you needed to change the front rack to use full size rear paniers. We use large rear paniers with a lowrider front rack on our 26" wheel tandem with no problems. They are low but the bike is very stable. If fact on our last camping trip a couple of weeks ago I rearranged our packing which resulted in the front paniers being heavier than the rears and if anything the bike felt more stable!
Jamesh
Posts: 2963
Joined: 2 Jan 2017, 5:56pm

Re: The Blatt - another year on

Post by Jamesh »

My blatt!

https://photos.app.goo.gl/c4NVU9i22tGdtCvA8

Needs new groupset rear rack.

1.5" tyres for rough Devon roads.

Cheers James
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