1 piece vs. 3 piece crank?

[Philphine]

is there any advantage either way?

i destroyed the 3 piece crank on one of mine trying to get it apart (i've since learned a pickle fork works great to do it. a little too late though)

i've got more one piece crank bb's around than three piece and i'm thinking i could find a front sprocket i like easier for them, but i'm wondering if i should hold out for a 3 piece. are they normaly lighter? that's a goal for this bike. i know better quality bikes have them, but what are the real advantages, if any? thanks.

 

[deorman]

I'll just assume you're welding something up, since 1-pc can't go on 3-pc bracket. Alloy axle/aluminum arm 3-pc is a little lighter, and 3-pc axles are less likely to twist from overloading( jumping or fat guys standing :wink: ).

 

[Chainsaw]

I like one piece because it gives you many cxhoices in sprocket designs. I know that some 3 piece cranks (mostly the expensive bmx stuff) offer sprocket interchanging but for the most part you're very limited.
Doerman, I resemble that! :lol:

When I was a kid I'd break that little retainer nub off my one piece cranks but never twisted a crank arm. Pedals will usually strip or crack the crank arm where the screw in.

 

[Slick Rick]

Geez Chainy, your showin our age with the whole "crank arm retainer thingy". This crank cotter retaining pin thang is so 70's! And hey, I resemble that "fat guys" remark as well! The one real advantage I see with a 3 piece BB set-up is virtually no maintenance! At least it's that way if you use a modern sealed bearing type. :wink: I just recently had to replace one on my 2000 Giant Simplex cruiser, considering I have more miles on this bike than the rest of all my bikes combined, and it lives outside, and my 240 lb chunky self demands it to put out hard, I am inclined to call this componant bullet proof! :mrgreen: Later & PEACE!!!

 

[Chainsaw]

240 ... Lightweight!
I was trying to describe that dewclaw stubby thing on a one piece that anchors the sprocket so it doesn't spin on it's own. Anyone got the technical name for that thing?
But yeah I've torn them retaining pins out a time or two!

 

[roadmaster]

1 pc cranks... heavier than 3pc but maybe a little easier to service without having to have crank pullers or if your dealing with a 3pc sealed cartridge. between 3pc cottered and cotterless, i pick cotterless anyday of the week as the cottered type can be prone to slipping and its just a dead technology.

3pc cranks... more durable than a 1pc and less prone to twisting under severe torque (twisted the oe ashtabula crankshaft of my 63' jch last year). if you got a crankarm puller and any other tools you'd need, 3pc cotterless are bullitproof, hold their adjustments better and easy to rebuild.

 

[Philphine]

ok thanks. from what i'm reading and seeing a three would be better, but it looks like i need to go further up the price scale to really get the weight advantage. as i build the bike it's getting heavier and heavier, so at some point i may not care anyway.

it's for my buildoff bike, so i think i'm going to maybe let it depend on what i find first that'll let me finish in time. but if it looks like i won't beat the deadline, i'll slow down and see what i can come up with on a nicer three piece. thanks everyone.

 

[Rodland]

240 ... Lightweight!
I was trying to describe that dewclaw stubby thing on a one piece that anchors the sprocket so it doesn't spin on it's own. Anyone got the technical name for that thing?
But yeah I've torn them retaining pins out a time or two!

Hey, I like "dewclaw stubby thing" sounds technical enough to me. Or maybe, "sprocket stopper thing" :wink:

 

[deorman]

I only admit to the superiority of MODERN 3-pc. :| Cotter cranks belong on museum pieces, undisturbed Ralieghs, or in the recycling bin! I'm quite fond of the 1-pc myself. I recently lucked into a free 3-pc fits 1-pc bracket crankset though (thanks bc!), and I will definitely be putting it to use when some other stuff comes together.

 

[Bigcam59]

2 advantages to 3 piece cranks. One is you can use sealed cartridge bottom brackets...no more adjusting and they're virtually bulletproof. The other is you can get adapters to use them in 1 piece crank frames.

 

[JoKeR63]

I only admit to the superiority of MODERN 3-pc. :| Cotter cranks belong on museum pieces, undisturbed Ralieghs, or in the recycling bin! I'm quite fond of the 1-pc myself. I recently lucked into a free 3-pc fits 1-pc bracket crankset though (thanks bc!), and I will definitely be putting it to use when some other stuff comes together.

Cottered cranks work great on these!

I've never had the typical CC problems with this bike even after 1000's of miles.

 

[deorman]

Some are definitely better than others, but... how often do you stand on those? Seriously though, I think the problems most often arise when they are mixed with coaster brakes. They work better with experienced wrenchers as well. :wink:

 

[JoKeR63]

Some are definitely better than others, but... how often do you stand those? Seriously though, I think the problems most often arise when they are mixed with coaster brakes. They work better with experienced wrenchers as well. :wink:

I've had/got uprights that aren't so lucky! You really need a good set of pins and the pin press is very important if you can find one, I'm still lookin'.
And standing on them kills them! I also agree with the coaster brake thing. There's just something about torque reversal on any driveline that loosens up parts.

 

[onelesspedestrian]

Ex shop mechanic ramblings:

Being that cottered cranks are indeed a 'dead technology' I don't have a ton of experience on them, however, I have ridden a few bikes with them. One thing that seems to be critical is that you use new pins when installing them, or at the bare minimum ones that are in very nearly new condition. the other issue that will come up is if they do come loose, and you continue to ride it, you'll probably destroy it. On a cottered setup if it is not too bad you might be able to just fix it with new pins. Once you round out the flats on the axle even a little bit, the axle and the pins are trash. If you feel any play, the correct course of action is to stop immediately and tighten things up. The square taper ones are often ruined this way, and bike shops deal with this all the time. If it is properly torqued down in the first place, it won't come loose, but that doesn't always get done. If you ride a square taper while loose, you can ruin it within a matter of blocks, even without standing. This ruins the arms but not the axle, as long as the arms are alloy. If the arms are steel, it will probably ruin both. Make 3 piece setups TIGHT. if you strip the bolt head, that's too tight. slightly less than that is about right.

The 3 piece BMX cranks with the 48tooth spline 19mm axle and tubular cromoly arms are pretty much indestructable, and (I think) will also accept your vintage chainring of choice. Last I checked they are about $200 though. the cheaper BMX versions with a pinch bolt can be hit or miss on quality, but likely ok for rat-rod purposes.

bending a 1 piece is fun... it's like having suspension ..... for 1 run. you can bend it back with a vise and a big pipe over the other end... and then don't hit any more jumps. 1 piece is the "correct look" for most of the bikes around here, and it's fine if you're not jumping. The bearings aren't the greatest, but they'll do.

As a mechanic, I would not hesitate to run any of the systems out there (on a rat anyways). Having said that, the 1 piece is probably the least hassle. If you have an english BB (aka threaded) a modern sealed bearing BB and a square taper crank is the least hassle/money. If you have some cash to throw around, a BMX crank is probably the highest performance, and is available for either BB type. 1 piece is not all that heavy (lighter than the good BMX stuff actually). Alloy armed 3 piece off a modern mountain or road bike is obviously the lightest.

By the way, the correct way to remove a 3 piece arm(square taper) is with a puller that threads into the arm.

my $.02....