Alpine double

For discussions about bikes and equipment.
reohn2
Posts: 36792
Joined: 26 Jun 2009, 8:21pm

Alpine double

Postby reohn2 » 28 Oct 2018, 10:50am

For regulars about these parts,they'll know of my liking of a triple chainset as much as a shapely leg or pizza,however I've recently built a Genesis Vagabond and decided,due to it's intended use,to make up an Alpine double of 24/39t flavour from triple S/light Impact cranks and a chainguard in place of the outer ring made from an old biopace 46t c/ring I had(photos on the Vagabond thread)
This chainset with 9sp 14-34 custom cassette(a standard 11-34 cassette would give a much higher top gear if you can put up with the yawning gaps in the mid range),with 700C x 50mm(actual size 46mm high on a 19mm internal rim) is proving a very successful combo.
The drivetrain gives me a 20in to 78.5in range which for my ageing legs and limited cycling time currently available is great,I can climb a wall on the lowest gear and the high end spins out at over 20mph which as fast as want to pedal at these days.
So all round I'm a happy chappy.

The putting together of the chainset was a simple job once I'd removed the teeth from the old 46t Biopace outer ring concentricized it and sprayed it black(why did anyone think Boipace was a good idea?) ,which looks neat,but would've been easier made with a round ring.The inner ring is an ordinary 24t 74 BCD steel 'granny'.
The outer 39t ring 110BCD(in the middle ring position)was one of a pair of new tandem timing rings I had in stock,herein lies the 'spot the loonie' problem.
Everything ran OK changes were slick despite the 39t not having any ramps and pins.Then yesterday I got chain suck changing down to the inner which not only almost brought me to a complete stop climbing a 10% offroad leafy track but also took paint off the chainstay of my new bike :evil:
On returning home with the bike hung up I spotted the problem almost instantly,no recesses on the 39t ring because it was made for the outer position which left the chainring bolts proud of the ring,why didn't I spot this before :roll: ,I'm putting it down to senility :?
What's worse is that a quick rummage in 'the box' revealed an almost new middle position 39t ring :shock: :roll: :? ,no I don't know why I didn't either :? .
Anyway all's well that ends well and with the correct ring in place the problem is solved,and because those kind people at Genesis bikes provide idiots like me with a vial of touch up paint complete with brush,you'd never know an idiot was riding the bike,unless he told someone :?
So to sum up.
Alpine doubles rock.
Touch up paint is good.
Fitting outer rings in the middle position isn't so good

Confession over forgive me father for I have sinned and now feel much better for getting that off my chest :?
-----------------------------------------------------------
I cycle therefore I am.

pwa
Posts: 10654
Joined: 2 Oct 2011, 8:55pm

Re: Alpine double

Postby pwa » 28 Oct 2018, 11:19am

I made similar Alpine doubles for my daughter and my wife using Spa's amazingly affordable but nice XD cranks in triple form, and with a black metal chainguard in place of an outer ring. It worked really well, giving lower gears than a so-called "compact" chainset. It looks good, it works and it isn't expensive.

Bonefishblues
Posts: 6957
Joined: 7 Jul 2014, 9:45pm
Location: Near Bicester Oxon

Re: Alpine double

Postby Bonefishblues » 28 Oct 2018, 11:27am

I have one too, albeit fitted to the tandem at the moment, coupled to the kiddicranks at the rear, for which it has proved ideal. I'll probably stick it on the hybrid in place of the current SRAM urban chainset, whatever it's called.

User avatar
deliquium
Posts: 2099
Joined: 9 Mar 2007, 3:40pm
Location: Eryri

Re: Alpine double

Postby deliquium » 28 Oct 2018, 3:18pm

reohn2 wrote: 9sp 14-34 custom cassette


Don't be coy :wink: - we (of course I mean me) are/is/am wanting to know precise details, please :)

ps still haven't found the worn out 110 BCD 46 rings I know I have somewhere :roll:
Current pedalable joys

"you would be surprised at the number of people in these parts who nearly are half people and half bicycles"

reohn2
Posts: 36792
Joined: 26 Jun 2009, 8:21pm

Re: Alpine double

Postby reohn2 » 28 Oct 2018, 4:26pm

deliquium wrote:
reohn2 wrote: 9sp 14-34 custom cassette


Don't be coy :wink: - we (of course I mean me) are/is/am wanting to know precise details, please :)

ps still haven't found the worn out 110 BCD 46 rings I know I have somewhere :roll:


The cassette is made up from a 14,15,16,17,18,19,21,23,25 Tiagra 9sp,and an 11,13,15,17,20,23,26,30,34 Deore 9sp cassette
To make a 14,15,17,19,21,23,26,30,34 this gives me a close enough progression in the most used cruising ratios with bigger gaps at the lower end where I find I don't need the closer ratios.
I've been using this combination for quite a few years on the tandems with road STI's,and without the 15t cog as an 8sp cassette(with appropriate 8sp spacers)operated with Kelly Take Offs and d/tube levers.
Some ramps are out of sequence but with road STI's(it's the same story with MTB pods) this is never a problem as the shift to a bigger sprocket was easily slightly over shifted with the larger brake lever,shifting to a smaller sprocket is never an issue as the chain is falling.
The 8sp cassette worked fine even thought stone ramps were out of sequence.
However when I made up the 9sp cassette by adding the 15t cog with the 9sp shifting being more critical and the D/Tube levers lacking over shift and hard to feel so two ratios can be easily shifted,this was never a problem with the 8sp as the indents on the D/T levers are much further apart,so a little over shift was possible without shifting two cogs.
To counter this I set about the offending cogs with the Dremel grinding off one tooth and profiling the preceding one in the shifting sequence.
I've now got it shifting pretty slick on the Vagabond though the levers are bar ends in Kelly's and I prefer D/Tube ones as they're a bit longer and aren't cranked which makes them easier to use in the Kelly's.I have 9sp D/T levers on the Vaya and may buy a pair of 9sp D/T levers if the B/end levers annoy me enough though I think they're expensive for what they are.

BTW, if you do come across that chainring I'll have it off you but don't don't go turning over the bunkers for me as Gaz has one in the pipeline for me :)
-----------------------------------------------------------
I cycle therefore I am.

User avatar
531colin
Posts: 12536
Joined: 4 Dec 2009, 6:56pm
Location: North Yorkshire

Re: Alpine double

Postby 531colin » 28 Oct 2018, 5:07pm

The guys at Spa made up a prototype Elan for me with a 24/40 double (being the 16T gap which Shimano seem to want)
It worked really well, in fact I couldn't make it miss a shift, and I tried.
My usual triple is 24/34/46, and 24/34 doesn't sound very different to 24/40; but I found the jump up or down on the double quite difficult to deal with. Going up to the big ring I could change down at the back a couple of sprockets and it wasn't too bad, but going the other way I couldn't pump the STI quickly enough changing up at the back. There again, I'm not used to STIs anyway.

reohn2
Posts: 36792
Joined: 26 Jun 2009, 8:21pm

Re: Alpine double

Postby reohn2 » 28 Oct 2018, 7:16pm

531colin wrote:The guys at Spa made up a prototype Elan for me with a 24/40 double (being the 16T gap which Shimano seem to want)
It worked really well, in fact I couldn't make it miss a shift, and I tried.
My usual triple is 24/34/46, and 24/34 doesn't sound very different to 24/40; but I found the jump up or down on the double quite difficult to deal with. Going up to the big ring I could change down at the back a couple of sprockets and it wasn't too bad, but going the other way I couldn't pump the STI quickly enough changing up at the back. There again, I'm not used to STIs anyway.


Yes going down onto the 24 c/ring still needs a bit of thinking about where I need to be on the cassette,as you say the jump from 39t(in my case)to the 24t is a lot more of a jump than the 34t to 24t I'm used to,but it's not too steep a learning curve.
What I do like is that there's only the two stops to be concerned about on the friction front changer
-----------------------------------------------------------
I cycle therefore I am.

mattsccm
Posts: 2790
Joined: 28 Nov 2009, 9:44pm

Re: Alpine double

Postby mattsccm » 28 Oct 2018, 7:45pm

It may be cheating and not quite what people need but I just use a modern MTB double. 28/42. With a 32t biggest rear sprocket its pretty low. Mine's a SRAM and I am sure that other size chain rings are about. A 44t outer also works perfectly with SRAM Rival front mechs.

Valbrona
Posts: 2245
Joined: 7 Feb 2011, 4:49pm

Re: Alpine double

Postby Valbrona » 28 Oct 2018, 7:46pm

I just can't quite believe that a bike company is supplying touch-up paint. And with a brush!

You know it is not until you give a chainset a good test you find the faults/shortcomings, no matter how much testing you might do with it in a workstand.

I could see myself on an Alpine double if triples ever get phased out entirely.
I should coco.

Valbrona
Posts: 2245
Joined: 7 Feb 2011, 4:49pm

Re: Alpine double

Postby Valbrona » 28 Oct 2018, 7:49pm

mattsccm wrote:It may be cheating and not quite what people need but I just use a modern MTB double. 28/42. With a 32t biggest rear sprocket its pretty low. Mine's a SRAM and I am sure that other size chain rings are about. A 44t outer also works perfectly with SRAM Rival front mechs.


I think Q Factor would be too high for me, unless in the case of regular shoes/utility bike scenario.
I should coco.

reohn2
Posts: 36792
Joined: 26 Jun 2009, 8:21pm

Re: Alpine double

Postby reohn2 » 28 Oct 2018, 8:10pm

Valbrona wrote:I just can't quite believe that a bike company is supplying touch-up paint. And with a brush!......

Why?
-----------------------------------------------------------
I cycle therefore I am.

Bonefishblues
Posts: 6957
Joined: 7 Jul 2014, 9:45pm
Location: Near Bicester Oxon

Re: Alpine double

Postby Bonefishblues » 28 Oct 2018, 8:14pm

I've just ordered my daughter a Genesis Alpha 24, which arrives on Tuesday. Looks absolutely brilliant and expect not to be disappointed - sadly they've stopped producing junior bikes.

I suspect we'll need a tub of touch up paint :D

User avatar
RickH
Posts: 4582
Joined: 5 Mar 2012, 6:39pm
Location: Horwich, Lancs.

Re: Alpine double

Postby RickH » 28 Oct 2018, 8:31pm

Valbrona wrote:I just can't quite believe that a bike company is supplying touch-up paint. And with a brush!

My Kona Sutra came with a little pot of touch up paint, with a brush inside the cap, in the box of bits that came with it. :D

mattsccm
Posts: 2790
Joined: 28 Nov 2009, 9:44pm

Re: Alpine double

Postby mattsccm » 29 Oct 2018, 7:05am

Not measured the Q factor to be honest. Haven't got any rub in about 4 years, much of which has been wearing thick overshoes on gravel tracks. Being short of leg wide Q factors are noticed.
I suspect that its wider than many road cranks but less than a lot of MTB doubles.

1 thing in its favour is that it looks fairly tidy. Whilst the outer ring is inside the spider, as if a middle ring, it doesn't look as if anything is missing. The ledge that the outer ring might sit on isn't there.

If you use a square taper MTB chainset you can often get away with a very short BB as using a smaller inner ring tha many a road bike was designed for can allow the whole lot to sit closer to the frame without fouling.

Of course if you use nice polished alloy cranks any rubbing won't show.

ANTONISH
Posts: 1601
Joined: 26 Mar 2009, 9:49am

Re: Alpine double

Postby ANTONISH » 29 Oct 2018, 8:49am

I made an alpine double from a Stronglight impact. 44/26.
Hacked the teeth of a worn 48t to make a chainguard - rear cassette 9sp 12/36.
I like to have the chainset close to the BB and had trouble finding something suitable, finally ending up with an old Dura Ace double - drawback was that the chain rubbed the bottom of the changer in the small/small area- not a problem as I wasn't intending to use those ratios.
I used it on a recent ride from Narbonne to Dieppe (partly train assisted due to a back problem) and it changed very well.
I'm going to change the 26 to a 28 and use the bike for audax.
I've also had the odd problem with chain suck (not this bike) and I wonder if it's worse with a short wheelbase.