Author Topic: changing sprocket,uses for the old one?  (Read 895 times)

ledburner

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changing sprocket,uses for the old one?
« on: January 17, 2018, 01:54:06 PM »
For anyone changing to a new sprocket, I neeed an old one.
Please see my post in wanted if you dont have a use for it (posted16/1/1).
Thx
Ledburner...
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Danneaux

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Re: changing sprocket,uses for the old one?
« Reply #1 on: January 17, 2018, 08:22:57 PM »
None available from me at the moment, Ledburner, but I'm surely interested in your plans for same.

Best,

Dan. (...who saw your call on the "Wanted" board and is by now burning with curiosity)

ledburner

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Re: changing sprocket,uses for the old one?
« Reply #2 on: January 18, 2018, 12:45:12 AM »
The plan is to make a dual rear sprocket.  half step between ratios. Replace the chain tensioner with a  short cage deraileur,
I believe this is possible by carefully selecting 2 close sprockets.
I tried this with double chain rings. It worked but changes were too slow.
(The chain ring didn't have ramps etc to speed up the shifts.)
 Note, A eighth to quarter turn at the front will change the dual rear faster than a half turn Of the cranks, with a double-chainset set at the front.

I am currently on a triple chain set on the front, the inner ring is a chain catcher for poor shifts.
I dont really have 42 usable gears.28 will be enough!
.
« Last Edit: January 18, 2018, 12:52:53 AM by ledburner »
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Danneaux

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Re: changing sprocket,uses for the old one?
« Reply #3 on: January 18, 2018, 02:47:11 AM »
Thanks! I figured!  ;)

When I first considered a Rohloff, I also pondered a half-step setup, but one using a single sprocket and dual chainrings (I prefer half-step gearing on my randonneur bikes). The steps and progression came out pretty nicely with a 2-tooth difference between the 'rings, but it would require both a front derailleur and a chain tensioner, where your scheme would eschew the front mech in favor of a rear derailleur instead of a tensioner.

In practice, I have found the single 'ring and cog on my Nomad to be "enough" for my needs primarily because my most-used gears are the same (in gear-inches) as my most-preferred half-step derailleur combos on my rando bikes. :)

Looking forward to seeing the result and all good wishes on sourcing the cogs you need.

Best,

Dan.

martinf

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Re: changing sprocket,uses for the old one?
« Reply #4 on: January 18, 2018, 07:11:18 AM »
The plan is to make a dual rear sprocket.  half step between ratios. Replace the chain tensioner with a  short cage deraileur,
I believe this is possible by carefully selecting 2 close sprockets.
I tried this with double chain rings. It worked but changes were too slow.

My aim was to extend a limited gear range, not to get finer gear steps, but I came to the same conclusion with my "touring" Brompton.

First I fitted double chainrings and 5-speed hub. Later I fitted two sprockets (13 and 19) on the 5-speed hub and dispensed with the double chainrings. I needed to grind the raised tabs of the 19T sprocket, after that it fitted OK on the driver of the 5 speed hub with a standard Brompton 13T sprocket and slim spacer.

Two rear sprockets shift much quicker, and this setup is substantially lighter (weight counts, because I carry the folded Brompton). Downside is that the small 13T sprocket clogs sometimes in mud or snow, and the special pulleys on the Brompton rear derailleur are more hassle to clean than a front derailleur.


ledburner

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Re: changing sprocket,uses for the old one?
« Reply #5 on: January 18, 2018, 04:31:45 PM »
Thanks for you input guys.
MartinF, mud wont be an issue, being a practical sort of guy read, anti-fashionista' I believe in guards tokeep thecrap off in.the first places, main sources, front chain ring from front wheel and back wheels as primeary chain-crap interfaces. It is tried and tested on another bike.
Mainenace regime simplified👍😀
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mickeg

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Re: changing sprocket,uses for the old one?
« Reply #6 on: January 18, 2018, 05:21:39 PM »
When I first built up my Nomad, I was a bit frustrated with the 525 percent range of the Rohloff, my derailleur touring bikes had a wider range.

And I was unhappy with the 13 percent change in gearing with each shift.  My dérailleur touring bike with half step plus granny triple and an eight speed cassette in back gave me much tighter gear ratios in the range of gears where I spent the most time.  Gear ratios were wider spaced when I was using the granny gear, but I could accept that since those lower gears were rarely used.

But, I eventually got used to the Rohloff gearing.  On my deraileur bikes I usually had a cadence in a fairly tight range of about 72 to 78, with the Rohloff I eventually got used to a wider cadence range of about 71 to 81 to compensate for the wider gear steps.

Since a larger sprocket with a corresponding larger chainring puts less wear on the chain and probably less wear on the sprocket too, if I could have bought a 20T sprocket for my Nomad I probably would have.  I spent a little bit of time trying to figure out how hard it would be to use the threaded on sprocket as a means to bolt a larger sprocket on to it.  But I still have not had to take my sprocket off to reverse it, so I no longer worry about that, as wear has not been a big deal on my bike.  I have several bikes, no individual bike is used the majority of the time which has reduced wear on each bike.

Bottom line, I have gotten used to the setup that I built up in early 2013, it is coming up on five years now.  I anticipate no changes.

Good luck with your planned changes, but you might eventually conclude that the simplicity of settling for 14 gears is not worth the additional effort.



ledburner

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Re: changing sprocket,uses for the old one?
« Reply #7 on: January 18, 2018, 06:16:55 PM »
Thanks mickeg, my old (soon to be retired 26" mtb has triple chain set , set up with the outer Rings as  ½ step or is it 1½ step gearing. originally No inner chaing, Just a double After loosing the chain, it was  jamming between the crank and axle. A Real Paiñ in the @®$€. So I re install the inner ring so the chain  couldn't go between the Bottom bracket axle and inner chain ring  threaded bosses. Inner ring effectively a chain catcher.
I once cycle with a 22 front 16.  It was going nowhere fast!
I think I still want the half gears.
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martinf

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Re: changing sprocket,uses for the old one?
« Reply #8 on: January 18, 2018, 11:53:55 PM »
MartinF, mud wont be an issue, being a practical sort of guy read, anti-fashionista' I believe in guards tokeep thecrap off in.the first places, main sources, front chain ring from front wheel and back wheels as primeary chain-crap interfaces. It is tried and tested on another bike.
Mainenace regime simplified👍😀

Can't do much about mud/snow on the Brompton, the only worthwhile modification I have found possible is an extended, stiffer and wider front mudflap that reduces muck coming from the front wheel.

Even on my large-wheel bikes, a surprising amount of stuff finds its way onto the drivechain, despite having front and rear mudflaps and long, wide mudguards that cover more than the width of the tyres. Rim brakes also spread the dirt around (drum brakes reduce this on one bike).

3 of my bikes have Chaingliders, these pretty much solve the problem of crud on the drivechain under most conditions. Not possible with a double sprocket of course.

Tigerbiten

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Re: changing sprocket,uses for the old one?
« Reply #9 on: January 19, 2018, 05:23:05 PM »
I did think about something like that in the past.
But more like a 17/22 double sprocket which would have given me exactly 2 more gears.

As it is I've ended up with 38/54 double chainrings for almost 3 more gears.
This makes the shifts up/down the Schlumpf HSD 3-4-3, which is easier that just a one off 7 shift.
A 56 would be better big ring as it's a true 3 gear shift, but it won't work with my chainguard.

Danneaux

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Re: changing sprocket,uses for the old one?
« Reply #10 on: January 20, 2018, 09:46:54 PM »
Ledburner's recent posts about half-step Rohloff gearing and some PMs/queries caused me to dig out my old gear charts. Though likely too esoteric for all but the hardcore gearheads, they might still be helpful to others thinking about their gearing needs so...Thoughts Ahead:

On my derailleur bikes, I generally prefer half-step-and-granny gearing because it is easy to find and shift sequential gear combinations and to fine-tune cruising gearing for riding against winds or in gently rolling countryside while accommodating hill-climbing needs. Low gearing is still readily available via pairings of the smallest (3rd) chainring paired with the 3 or 4 largest freewheel/cassette cogs. I've arranged my most-used crusiing gears to run with minimal chainline deflection and enjoy quiet pedaling and long component life as a result.

Half-step gearing works best with 7 or fewer cogs to a) minimize chainline deflection and b) ensure the half-steps are still noticeable; if they get too small, they don't make "enough" difference to be worthwhile;I found ~7% to be the minimum practical difference between front shifts for my needs. It is for that reason I largely abandoned my own plans for a half-step Rohloff onmy Nomad (and because the chain tensioner -- depending on type -- counters some of the long-life benefits of the Rohloff I so value). It might yet be practical on one of my rando bikes because a chain tensioner would be required anyway and that bike is unlikely to be used for expedition touring.

My first goal in setting up my Nomad's Rohloff gearing was to ensure I had gears low enough to carry expedition loads up really steep terrain. The second goal was to ensure the cruising gears I value most in my randonneur bikes were also available (or very closely so) in the Rohloff drivetrain. To ensure comparable comparisons despite differences in wheel/tire size, I standardized on gear-inches as my unit of measure across all drivetrains and wheel/tire sizes.

There's several reasons why my gearing is so low on all my bikes and why I prefer half-step gearing on my randonneur bikes. It starts with bad knees, the result of a car crash when I was in high school. I started cycling "with intent" as physiotherapy and this required I use care to avoid setbacks while everything healed. My knees are still kind of fragile and I find I cannot pull gears over the mid-70 gear-inches and then only briefly; any gears above that are mostly just place-holders so the rest of the progression is where I want it. This means I must pedal with a higher cadence in lower gears to ease the strain. The cadence I generally fall into is 110-120rpm and never below about 80-85 going uphill. I make up for low gearing by pedaling faster and with less pressure.

I live in a town surrounded by steep hills on three sides, opening to flat farmlands to the north. This means on my longer 300-400km day rides, I need to not only accommodate climbing on hills but also smaller changes on flat or rolling terrain or due to unbroken winds. Half-step derailleur gearing does this most ably for me. For comparison, I've included a chart showing the crossover gearing used on my past Sherpa. The yellow combinations are the ones with minimal chainline deflection and so were most used by me to minimize wear and noise. A 9-sp half-step with the same cassette makes a very nice progression but is largely impractical because of difficulty finding a suitable front derailleur for the <5t gap and because of the larger width and greater chainline deflection of a 9-sp cassette compared to a 5-, 6-, or 7-sp cogset.

After I got my Rohloff gearing dialed-in my biggest physical adaptation was the even gaps between gears. Most derailleur setups are logarithmic in their progression: Bigger gaps between the lower gears "feels" like smaller gaps between the higher gears. I soon learned when I wanted "big" differences between lower gears on my Rohloff, I could get there by shifting two or three gears at a time. Works great, especially where I have the shifter placed handy on my Nomad. See: https://www.youtube.com/watch?v=lVh3qb4F0sQ 

In the first attachment below, I offset my gear charts to show how and where the individual combinations compare across my four most-used bikes. All my preferred crusing gears are marked with a ©. The half-step gearing is all on the middle and large chainrings except for the lowest 3 or 4 gears marked "L", which use the innermost (3rd) chainring [I have offset my BB spindles so the inner chainring is aligned with these lower cogs and the middle and high rings are considered like a double for chainline]. The leftmost chart shows what I thought would be the best "half-step" Rohloff setup for my needs. In the end, I didn't find it offered enough advantages to be worth it on my Nomad.

The individual derailleur charts in the second attachment show the progression of double shifts to get sequential half-step gears. In practice, I shift at the rear (full steps) to accommodate large needs and at the front (half steps, equivalent of half a rear shift) to accommodate small needs/fine-tune my gearing. Cruising along, I use the combinations marked with a © almost exclusively.

A last note: As my Rohloff chart shows, I use it as a two-stage gearset. I use the upper range (Gears 8-14) for most needs and the lower range (Gears 1-7) are what I use for hill work. Most riding is done in my Gear 11 direct-drive or in the gear just above or below it (Gear 10 or Gear 12).

And yes, each of my bikes has a gear chart taped to the handlebars. ;D They add pleasure to my rides along with my constant mental time-speed-distance calculations. ;)

Best,

Dan.
« Last Edit: January 22, 2018, 07:15:51 AM by Danneaux »

ledburner

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Re: changing sprocket,uses for the old one?
« Reply #11 on: February 06, 2018, 12:37:16 PM »
Thanks for all the feedback.  :)
This has changed to a medium term project. The R'off is being rebuild and upgraded to a 29er. The mate with the Lathe is on holiday. So coming together slowly. I still believe dual sprocket ,(I have done this with  chainrings),will be a neater job and less chain slack involved.
Wheel building 2 cross no dish probably the easiest way to start. Rohloff guide appears clear. A mate will assist/mentor me.
This may be unnecessary with oval chain rings, that's a nother topic!
I'll keep you posted ,
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Andre Jute

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Re: changing sprocket,uses for the old one?
« Reply #12 on: February 06, 2018, 11:45:17 PM »
This may be unnecessary with oval chain rings, that's a nother topic!

Yo, Ledburner, have you actually ridden with oval chain rings? Back in about 1990 I bought a top of the range Peugeot which, aside from having its tubes in some fancy alloy so badly specified that the thing constantly wrecked my back by rattling me around, came outfitted with Sachs-Huret oval rings which then were quite the vogue. Besides being the fashion, and besides offering an egregious MBTF of about 1000 miles, they also didn't work as advertised. They made changing gears a very hit and miss affair, throwing the chain off at optimum changeover orientation, refusing to change because it tightened the chain too much when turned 90 degrees from there. The only way to make it work, unsatisfactorily at that, was to set the chain too slack, and just grind your teeth every time it threw the chain off.

Admittedly, a Rohloff likes a slack chain, but a single speeder (the misnomer of the generic class the Rohloff setup -- and all hub gearboxes -- belong to) should never, ever, throw off the chain.

i suspect that after a lot of work, you will return the bike to 14-speeder configuration. (Not a reason to stop you experimenting and reporting here!) The equal 13.6 percent gear intervals are not ideal, but you soon cease to notice.

ledburner

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Re: changing sprocket,uses for the old one?
« Reply #13 on: February 07, 2018, 07:48:58 AM »
Hi Andre, thanks for sharing your experience. The chain ring are not biopace copys, and in theory the same number of teeth are engage on the chain wheel.  A chain tensioner will accomodate, 1-2 links of slack. I have since heard people say if using a fast cadence. The change of cadence can be felt in the knees. It is not fitted yes and I may use 2 ring, gear changer at front we will have to see. Rohloff at the rear-always.

 Should I admit I am still skint after buying the Rohloff (19 years ago), the frame is an old Merlin malt , I can't afford a Thorn as yet! 
« Last Edit: February 08, 2018, 08:30:46 AM by ledburner »
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ledburner

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Re: changing sprocket,uses for the old one?
« Reply #14 on: February 08, 2018, 08:31:02 AM »
I am moving to a 29er so the guards issue starts again. Full guards with staysare a no-no
So SKS blades a best compromise. Though the Zefal Defender was very good for 26" wheels, poor reviews for larger sizes , if available
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