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One piece cranks.

Old 12-26-15, 11:47 AM
  #1  
elmore leonard
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One piece cranks.

I notice people seem top frown at one piece cranks.
One piece cranks are very strong and trouble free. You see them on less expensive bikes but I don't think that makes them inferior to 3 piece cranks (ie. Bottom bracket and separate crank arms.). Any tell me why people prefer the 3 piece rather then the one piece?
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Old 12-26-15, 11:54 AM
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I converted my old Columbia 3 speed to a modern 3 piece system to save weight, and have more flexibility in choosing chainrings. With the Sturmey Archer hub, the only way to change the low or high range is either changing cogs at the hub, or chainrings on the crank. I can do both. One might consider the effort I have put into the old Columbia akin to spraying perfume on a pig, but between alloy wheels, 3 piece crank and other modifications, I have reworked it into a very comfy and efficient commuter that is still, hopefully, not too attractive to thieves.

Old single piece cranks are very bomb resistant, and one can still get parts to overhaul them. They appear to still have a following in some BMX pursuits, too, but I cannot cite anything specific.

Last edited by dunelt_1954; 12-26-15 at 11:55 AM. Reason: spelling and grammar corrections
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Old 12-26-15, 12:01 PM
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One piece cranks are a very functional design, and work very well. They do have drawbacks, one of the main ones is bearings that are not as well shielded from the elements as other designs.
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Old 12-26-15, 12:35 PM
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I found a Tubular one piece crank* in the mid 80's, that was quite nice, but the forged types are more common.

* havent seen any since then .. a steel tube bent into shape threaded parts brazed on .. during forming..



Bullseye cranks were used in BMX racing .. 2 parts , the one piece .. the crank spider and arm and a tube spindle were Patented ,

the lapsing of that Patent let the opting in of designers of cranks using the tubular spindle as part of the right crank-arm Proliferate.

https://s250.photobucket.com/user/box...aug86.jpg.html

Last edited by fietsbob; 12-26-15 at 06:46 PM.
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Old 12-26-15, 01:19 PM
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One-piece cranks tend to use 1/2" pedals as opposed to the more common 9/16" found on 2-3 piece cranks.
This limits the choice of pedals somewhat.
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Old 12-26-15, 03:21 PM
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Originally Posted by dabac View Post
One-piece cranks tend to use 1/2" pedals as opposed to the more common 9/16" found on 2-3 piece cranks.
This limits the choice of pedals somewhat.
There are adapters available to use 9/16" pedals (Sunlite 41618) but they will space the pedals out by about 21mm or so. This could actually be an advantage to the large- or splay-footed among us.
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Old 12-26-15, 03:29 PM
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I don't have one to weigh for comparison purposes but I'm thinking a lower end 3-piece crank and bottom bracket will save you close to a pound in weight. That's a pretty big weight reduction for just one part.
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Old 12-26-15, 03:34 PM
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Depending on which 3 piece crank you're comparing with 1 piece cranks can be far weaker and flexible. Ask any 20" rider who jumps. Andy.
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Old 12-26-15, 04:09 PM
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I'd like to see a forged titanium version..
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Old 12-26-15, 04:35 PM
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Originally Posted by exmechanic89 View Post
I'd like to see a forged titanium version..
You want to pay for a forged Ti version?
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Old 12-26-15, 04:46 PM
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Originally Posted by exmechanic89 View Post
I'd like to see a forged titanium version..
How about a one piece carbon crank, with adjustments for chainring size and crank length? It's a Look Zed 2. (You'll need a new, compatible frame, too...)



~~~~

Here's a new Ashtabula crank for $25.00 Only 1086 grams.

Or the Look Zed 2 for for $1250.00 It's 320 grams without chainrings.

Last edited by rm -rf; 12-26-15 at 04:57 PM.
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Old 12-26-15, 06:01 PM
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Originally Posted by rm -rf View Post
How about a one piece carbon crank, with adjustments for chainring size and crank length? It's a Look Zed 2. (You'll need a new, compatible frame, too...)



~~~~

Here's a new Ashtabula crank for $25.00 Only 1086 grams.

Or the Look Zed 2 for for $1250.00 It's 320 grams without chainrings.
Approx 2 lbs lighter, quite a difference.
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Old 12-26-15, 07:28 PM
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I love my one-piece Ashtabula crank! Heavy duty and very easy to maintain. Will last the life of the bike unlike euro bottom bracket equipped bikes.
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Old 12-26-15, 08:03 PM
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Originally Posted by Johnny Mullet View Post
I love my one-piece Ashtabula crank! Heavy duty and very easy to maintain. Will last the life of the bike unlike euro bottom bracket equipped bikes.
Actually 3 piece cranks can very well last the life of the bike. All my bikes are from the 80's through the early 90's, all riding on their original BBs and crank sets. Many other members have similar experiences.
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Old 12-26-15, 09:15 PM
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One of the many contributing factors to the boat-anchor-heavy weight of my first 'adult' bike, a '70's Schwinn Continental, was the one-piece crank. A pound here, a pound there, and all of a sudden you have a heavy bike. (Still riding relatively heavy bikes.)
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Old 12-26-15, 09:32 PM
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Originally Posted by JanMM View Post
One of the many contributing factors to the boat-anchor-heavy weight of my first 'adult' bike, a '70's Schwinn Continental, was the one-piece crank. A pound here, a pound there, and all of a sudden you have a heavy bike. (Still riding relatively heavy bikes.)
In reality there's nothing wrong with riding 'relatively heavy bikes'. Personally I ride mainly for the workout, so when I hear someone call a bike a tank because it isnt made of carbon or aluminum I just figure they're too out of shape to ride it.
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Old 12-27-15, 07:39 AM
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Originally Posted by exmechanic89 View Post
Approx 2 lbs lighter, quite a difference.
Your wallet will be $1225.00 lighter, also quite a difference.
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Old 12-27-15, 07:42 AM
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Originally Posted by exmechanic89 View Post
In reality there's nothing wrong with riding 'relatively heavy bikes'. Personally I ride mainly for the workout, so when I hear someone call a bike a tank because it isnt made of carbon or aluminum I just figure they're too out of shape to ride it.
This is my theory as well. I also do not worry that my frame will collapse because it has a small dent or scratch.
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Old 12-27-15, 07:56 AM
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Originally Posted by dsbrantjr View Post
Your wallet will be $1225.00 lighter, also quite a difference.
Actually, quite a bit more than that. The ZED crank is proprietary, it will only fit a Look frame designed to accept it. You have to buy the frame as well
Add more for the chainrings on top of that
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Old 12-27-15, 04:12 PM
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I wonder how the bearing races in the middle portion of a one-piece crank are machined? Even if they lathe-turn it before the crank arms are bent into their final shape, how is the thing even chucked into a lathe? @Johnny Mullet, ever go on a factory tour at the Huffy plant?

Marginally off-topic item: I replaced a three-piece, cottered Nervar crank with a cotterless alloy one mainly because the chainring was pressed onto the crank arm and had developed some play in the connection. The alloy cranks with the spider forged onto the crank arm seem better for that reason, as well as the weight reduction. I'm guessing the chainring on a one-piece crank is also pressed on.

Last edited by habilis; 12-27-15 at 04:20 PM.
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Old 12-27-15, 04:15 PM
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There is no American Huffy plant in operation anymore.
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Old 12-27-15, 04:33 PM
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Originally Posted by habilis View Post
I wonder how the bearing races in the middle portion of a one-piece crank are machined? Even if they lathe-turn it before the crank arms are bent into their final shape, how is the thing even chucked into a lathe? @Johnny Mullet, ever go on a factory tour at the Huffy plant?

Marginally off-topic item: I replaced a three-piece, cottered Nervar crank with a cotterless alloy one mainly because the chainring was pressed onto the crank arm and had developed some play in the connection. The alloy cranks with the spider forged onto the crank arm seem better for that reason, as well as the weight reduction. I'm guessing the chainring on a one-piece crank is also pressed on.
The "fixed" bearing race is screwed onto the axle, holding the cainring in place, then the axle is inserted into the frame. Then the other bearing race is screwed on the other side, with a lockring.

The few I have worked on have a separate, loose chainring, held on by the "fixed" bearing race. Both can be removed and replaced.

I assume there are variations over the decades.

Search "ashtabula crankset" for pictures and info.

Back in my racing youth, I had a Huffy type bike I used for bad weather training, and replaced the crank with a BB adapter so I could use a nicer crankset and 9/16 pedals w/ toe clips
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Last edited by Homebrew01; 12-27-15 at 08:49 PM.
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Old 12-27-15, 08:09 PM
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It's interesting to read some of the comments in this thread. Sad that it seems that some have not worked on, or paid attention, to the 1 piece cranks they talk of. Andy.
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Old 12-28-15, 08:03 AM
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Originally Posted by Andrew R Stewart View Post
It's interesting to read some of the comments in this thread. Sad that it seems that some have not worked on, or paid attention, to the 1 piece cranks they talk of. Andy.
I'm always proud to display my ignorance.

Last edited by habilis; 12-28-15 at 08:55 AM.
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Old 12-28-15, 09:07 AM
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I spoke to a factory rep from Worksman bicycles, and asked why they use 1 peice cranks. His answer was that they are cheap to spec, last a longtime, and if one does go bad they are common and cheap to replace.
They still have their place in the cycling world.
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