TallRider

Didn't see any discussion on this yet, so thought I'd start one. Velo Orange, claiming (probably correctly) that they have too much time on their hands, has introduced a quad crank. Four rings, kind of a "dual half step" setup (two largest are close to each other, two smallest are also close to each other, big gap in between).
I understand the value of half-step gearing but it seems like most of that value has disappeared with 9/10 speed cassettes (I doubt many folks will be running 11-speed cassettes on touring bikes anytime soon). Thoughts?


Here's a link to a full-sized image for those who really want a closer look.

fietsbob

Have a Mountain Tamer Quad adapter, tried it and set it aside 20 years ago
will sell .. had a 46,36,26,16t setup.

realistically below a certain ratio only a trike can take advantage of like a 10" gear
because you fall over on just 2 wheels..

or cannot get the 2nd foot on the pedal because all the momentum goes away, restarting on a hill

HillRider

I remember seeing ads for those too but I never had one. I agree that super low gears reach the point of diminishing returns when the bike is too slow to remain stable ( probably about 2 mph) and you can't start on any uphill because you can't get your second foot on the pedals before the bike comes to a complete stop. Trikes can, of course, be geared down to nearly zero speed but not bikes.

TallRider

I suppose there would be some value in an evenly-spaced quad crank (as fiestbob set up) for touring, if you wanted to be able to go 4-5mph on climbs while rocking the downhills and have a flat+headwind gear and a flat+tailwind gear.

I guess Velo Orange can defend the value of their quad crank a bit more since they have double half-step gearing. However, my sense is that half-step gearing was used to solve a problem that no longer exists. The problem was the large increments (steps) between gears on a wide-range 5- or 6-speed freewheel, for touring use. The increments between cogs on a 9- or 10-speed cassette are smaller, and closer to the "half-step" gearing already, thereby kinda defeating the purpose of half-step gearing nowadays.

Still, I definitely see the value of a really low granny gear for loaded touring, where there are occasions when it is convenient to be able to pedal efficient RPM's at 4 or 5 mph.

(For reference, half-step triples usually had the middle and large chainring very close in size, as pictured here on my mom's Fuji which originally had a 6-speed freewheel).

fietsbob

Recently I got a Schlumpf Mountain drive , for my Brompton ..

the low range is as if the crank which has a 54t chainring also has a 21.6t chainring too .

50 / 20 is even numbers .

they use a 3 speed hub twice, but the % differences between a 58" gear and a 23" gear ,
being the N or 2nd gear in each range, at 75% and 133% are smaller in low range ..

no indication if the VO setup even works , as shown, since the half step gear
wont shift out of the smaller of those 2 higher chainrings to the upper/ outer ,
with that, a MTB FD that needs a 12T difference just to clear that chainring.

Those half steps used a shallower back plate FD to clear something with only a 4 or 5t difference.

Cyclone road even offered a lower stirrup accessory to clear the chain
when it would drag on the usual Bolt and spacer at the Bottom tail of their standard FD cage.

But as a Conversation piece, see what it started.. ? that part worked..



LBS has a 59cm Specialized Expedition from the Mid 80s, on consignment FS, here,

it still has the original parts on it including the 48-44 half step + a granny crank
and 7 speed 13-32t freewheel.

LesterOfPuppets

When will we see compact triple?

Just get on olde 28/38/48 MTB crank and put a 50T big ring on there

BAM

compact triple.

davidad

I like my seven speed half-step with a 20t grandpa gear. I have 18 distinct gears that you don't get with the modern 9,10,11 or shimano's 14speed patent for a cassette.

Barrettscv 

It's not hard to attain a huge range with a 110 bcd MTB triple and a 11-32 rear cassette. This bike has a 48, 36 & 22t chainrings and a nine-speed 11-32 cassette;

HillRider

Getting a "huge range" is not the problem. Getting a huge range without huge gaps in the intermediate gears is a lot more difficult.

Barrettscv 

Actually, I can stay in the 85 to 100 rpm cadence range with this gearing from 4.6 mph to 33 mph. The largest change in cadence from cog-to-cog is less than 17%.

rdtompki

What's a "Compact Triple"? If a triple, why would you need something other than 52-39-30 unless you wanted a smaller granny for either lower gearing or a tighter cassette. I've found my 12-30 cassette to be adequate and 30-30 will get me up some pretty big climbs. Since I'm 68 y/o and 200 lbs I'm not sure anyone younger would need lower unless they're either touring or going up sustained grades >15%. Having said that I'd go lower if doing a 100K with 100'/mi of climbing.

ThermionicScott 

I'm all for thinking outside the box, but when I'm grinding up a hill, the last thing I want to do is add front-shifting to the mix.

Kimmo

This is a damn cool idea.

There's no making the value of half-step disappear - unless you can imagine a painless switch to 1/4" chain pitch!

The half-step is an answer to the inherent problem of ratio spacing on a derailer drivetrain; consider a corncob. Every time you shift to higher gear, the gap between gears gets bigger, and this is precisely the opposite of what's desirable. So you see 3 and 2 tooth gaps between the lower gears, which approximates something optimal, but the only two ways of allowing smaller gaps below say 17t, is to make the pitch shorter, allowing 3 and 2 tooth gaps to make their way further down the cassette for a given ratio gap, which is obviously pretty impractical, or to have another chainring almost the same size.

Problem is, front shifting is a PITA. I'd be very interested in an electronic version of this that does away with separate control of each derailer and just shifts to the next highest or lowest ratio automatically...

And come to think of it, a quad probably isn't necessary... with a careful selection of ratios I think a single small ring and two big rings would be optimal.

Hmm, I have compact Rival crank... no messing with chainline on an external BB crankset really, but I was thinking an extra big ring hanging off the front, combined with a 135mm OLD should work okay...

Kimmo

Hah, reminds me of this: https://boingboing.net/2009/09/15/mot...hed-to-se.html

Kimmo

Your FD seems a bit high there; looks like you could lower it about 5mm... good chance it'd improve the shifting.

fietsbob

mountain bike stuff ..44t 32t 22t most common..

Altbark

Triple cranksets made a lot of sense when when 5 and 6 speed cassettes were the norm. You had the two big rings for normal road work and a small ring for granny gears. But that really isn't the case anymore. The advent of 9, 10 and now 11 speed cassettes now gives us the range needed using a double crankset for most applications from pure road and touring through to MTBing.

I have a triple setup on my tourer that I had upgraded from the factory drivetrain and can tell you that I would be running a 2 X 10 MTB setup if making the change today. Al

jim p

Problem is, front shifting is a PITA. I'd be very interested in an electronic version of this that does away with separate control of each derailer and just shifts to the next highest or lowest ratio automatically...

I think that you just came up with the next upgrade for shifting. It might need some manual over rides so that you don't have to go through all the gears when you want to shift up or down by several cogs.

Barrettscv 

It shifts well and wouldn't shift at all if I lowered the FD 5mm. You trust the images on the internet a little too much.

cyccommute 

It's not that difficult to balance on a 2 wheel bike with zero forward speed. I track stand all the time at stopsigns and stoplights. I also owned one of the Mountain Tamers with a very similar gear ratio and had zero problems using it while mountain biking. Starting on a hill and on loose ground is always a problem for mountain bikers but it's not impossible.

There were a couple of problems with the Mountain Tamer that don't have anything to do with staying upright while pedaling. It just wasn't up to the torque requirements and tended to break where it was bolted to the crank and it required cranksets that didn't have posts for the third ring. And fitting one to a crank wasn't that easy. Modern cranks don't usually have forged posts for the 3rd ring but in the heyday of the Quad Tamer, this wasn't the case. The advent of indexed front shifters has further eroded the market.

The quad was further killed by the advent of chainrings below 24 teeth. Suntour made the MicroDrive which could be used with an 18 tooth inner. Most modern mountain bike cranks can be fitted with a 20 tooth ring. Most people think it's limited to a 22 but it isn't. It's just hard to find 20 tooth inners for the 64mm BCD cranks.

cyccommute 

Sorry but that's not a 110mm BCD. It's a 104mm BCD.

cyccommute 

They still make sense. The problem with compact doubles is the shift pattern. Using this gear calculator you can easily compare gearing combinations, like this one.



There are more intermediate gears with the triple without the huge jumps between the rings. You basically have 2 separate drivetrains with the doubles and getting from one drivetrain to the other isn't a smooth transition.

I find it funny that the main driver behind the 10 and 11 speed cassette is to have more gear choices on the cassette, yet the drive is to get rid of the front gears which reduces the gear choices.

Kimmo

...

HillRider

Trackstands are something of a trick and certainly not what you want to have to do while climbing a steep hill. The question is how slow can you go and still maintain adequate stability and steerage?

fietsbob

Pretty close:
Here is a push button electronic shifter for shifting a Rohloff Hub..
the Rohloff design, engineers the sequential line up of the gear ratios in the hub, through a rotary selector..

https://www.edsanautomation.com.au/EdsanProducts.htm