02GF74
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| posted on 18/3/08 at 11:59 AM |
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Pressed cranks
forgive for intruding into the BEC forum - donlt usaully come here, but are modern bike cranks one piece or built up cranks like in the Z1000 A1-4?
(the crank is made up of several pieces pressed together with one piece conrods and roller bearings).
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smart51
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| posted on 18/3/08 at 12:06 PM |
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My R1 crank is one big piece.
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MikeCapon
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| posted on 18/3/08 at 12:31 PM |
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Modern bike cranks are pretty much all one piece affairs these days. Reason being that the pressed up cranks twist with the power involved.
That's why one of the performance mods of the time was to weld the crank to stop it all twisting.
www.shock-factory.co.uk
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02GF74
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| posted on 18/3/08 at 01:03 PM |
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^^^^ that makes sense 85 bhp from a 1000 cc engine in 1975 compared to twice that in 2007.
.... but what if the cranks are splined? too expensive probably?
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Coose
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| posted on 18/3/08 at 01:15 PM |
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One of the strongest big-bore bike cranks ever made was from the mid-90s Suzuki GSX1100EF. It was a pressed crank (with big ends and mains on roller
bearings) but was welded as standard. A lot of drag bikes did and still do use this motor, finding that the crank would only need upgrading once they
reached the kind of horsepower that would push your eyeballs out of your feet! 
I would suspect that maunfacturers stopped making cranks like this for a few reasons: -
1, Cost
2, Progression in materials technology
3, Cost
Spin 'er off Well...
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Benonymous
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| posted on 19/3/08 at 06:05 AM |
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eh, you young kids....
Eeee, pressed oop cranks that were t' day... Pressed up cranks were only needed when roller bearing mains were fitted to a motor. All the old
school inline jap fours had 'em in t' day of the Z900/1000, GS1000, GSX1100 etc etc. There's no doubt that a one piece crank
running in plain bearings is cheaper but its not necessarily stronger. The GSX 1100 motors and other derivatives were the nuts for supercharged drag
bikes in the 80's.
Thats t' problem wi t' young tykes these days, no 'istory in 'em......
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