Why did the orientation of the square taper change from diagonal to parallel?
02-01-13, 09:59 PM
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Why did the orientation of the square taper change from diagonal to parallel?
Most modern cranks (new bmx cranks) new TA (Carmina) cranks all have their square taper parallel in their cranks, the older types all had it diagonal. Does anybody know why?
Makes it impossible to mix and match.
Makes it impossible to mix and match.
02-01-13, 10:16 PM
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Being the cynic I would first think of the need to source from the manufacture that started it (like Schwinn did with it's slightly different dimensional standards way back when). The second thought is a work around to some patent. Third is an engineering thought.
Maybe people smarter then I can chime in. Andy.
Maybe people smarter then I can chime in. Andy.
02-01-13, 11:04 PM
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02-02-13, 12:28 AM
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From a design standpoint it doesn't matter on the right crank because there's plenty of meat. But on the left where there's lot's less the orientation can affect the strength and whether it'll crack. Most forged cranks are diamond, but many lower end cranks are square. As pointed out earlier, this isn't so much a matter of a change, as of a design difference of opinion.
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02-02-13, 01:25 AM
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just 2 ways to do the task.
Manufacturer discression.. it was their choice, ask them.
Manufacturer discression.. it was their choice, ask them.
Last edited by fietsbob; 02-15-13 at 01:15 AM.
02-02-13, 04:06 AM
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Last edited by saturnhr; 02-02-13 at 04:37 AM. Reason: typo
02-02-13, 08:37 AM
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02-02-13, 09:52 AM
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I respect the fact that the spindle manufacturers held their ground and stayed with diamonds rather than jumping on the square bandwagon.
02-02-13, 10:23 AM
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Some cranks are square, some cranks are diamond. There is no standard and what a manufacturer uses is entirely up to them.
Which part are you having trouble understanding? We'll type it more slowly.
02-02-13, 10:45 AM
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I don't know the answer to the question, but the ability of BF posters to take even the simplest questions and turn them into snarky contentious arguments is a constant source of wonder and entertainment for me. So thanks for that everyone (although I will add that mechanics seem slightly less prone to this, in my observation, than, for example, the roadie forum where threads degrade into gibes and snark pretty much as a matter of course -- quite entertaining) .
02-02-13, 01:28 PM
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The question nobody has addressed is whether a square crankset can be used on a diamond spindle, or vice versa.
02-02-13, 02:30 PM
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The answer to that is yes, assuming the cranks and spindle are both the same taper - ISO or JIS. Of course you have to replace both cranks at the same time.
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Just because I'm tired of arguing, doesn't mean you're right.
“One accurate measurement is worth a thousand expert opinions” - Adm Grace Murray Hopper - USN
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02-02-13, 02:53 PM
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02-02-13, 04:12 PM
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(It was supposed to be a joke!) 
02-02-13, 06:57 PM
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The manufacturers of aftermarket left crank arms have a very powerful lobbying group in DC. They force crank manufacturers to make both styles and alternate years when diamond and square tapers are spec'd on new bikes. That way I have to stock six different left arms (12 if I want to have black and silver. Even more if we want to stock the oddball road sizes) instead of three in my parts bins at the shop. It's all a big conspiracy fueled by dollars from big left crank and their Washington cronies...
02-03-13, 12:11 PM
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The manufacturers of aftermarket left crank arms have a very powerful lobbying group in DC. They force crank manufacturers to make both styles and alternate years when diamond and square tapers are spec'd on new bikes. That way I have to stock six different left arms (12 if I want to have black and silver. Even more if we want to stock the oddball road sizes) instead of three in my parts bins at the shop. It's all a big conspiracy fueled by dollars from big left crank and their Washington cronies...
02-03-13, 02:02 PM
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The manufacturers of aftermarket left crank arms have a very powerful lobbying group in DC. They force crank manufacturers to make both styles and alternate years when diamond and square tapers are spec'd on new bikes. That way I have to stock six different left arms (12 if I want to have black and silver. Even more if we want to stock the oddball road sizes) instead of three in my parts bins at the shop. It's all a big conspiracy fueled by dollars from big left crank and their Washington cronies...
02-03-13, 02:17 PM
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Actually the Congress is split with different parties in control of the House and Senate. They cannot pass a bill mandating either Diamond or Square orientation. This happened before, which lead to a compromise solution in the form of the spline drive system. However with square and diamond cranks grandfathered, the problem remains, so the current proposed solution is to orient the hole so the corner is exactly in between both, or pointing 22.5° off the axis of the crank.
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An ounce of diagnosis is worth a pound of cure.
Just because I'm tired of arguing, doesn't mean you're right.
“One accurate measurement is worth a thousand expert opinions” - Adm Grace Murray Hopper - USN
WARNING, I'm from New York. Thin skinned people should maintain safe distance.
02-03-13, 05:04 PM
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Just looking at these two examples, it seems that the diamond makes a stronger 5-bolt crank, and the square makes more sense for a 4-bolt crank. A change for either would leave less "meat" at some of the corners.
02-03-13, 06:51 PM
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So there's no one always correct answer, and either is fine assuming the rest of the design is consistent.
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An ounce of diagnosis is worth a pound of cure.
Just because I'm tired of arguing, doesn't mean you're right.
“One accurate measurement is worth a thousand expert opinions” - Adm Grace Murray Hopper - USN
WARNING, I'm from New York. Thin skinned people should maintain safe distance.
FB
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An ounce of diagnosis is worth a pound of cure.
Just because I'm tired of arguing, doesn't mean you're right.
“One accurate measurement is worth a thousand expert opinions” - Adm Grace Murray Hopper - USN
WARNING, I'm from New York. Thin skinned people should maintain safe distance.
02-03-13, 06:51 PM
#25
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Yeah, wish I'd gotten the memo before I ordered the new left arm for my old Suntour crank. A real wtf moment.