Shimano hollowtech crank cutaway

[staggerwing]

A re-direct, just because the enginerd in me thinks it is way cool.

From: http://fotos.mtb-news.de/p/1965358

[spartanKid]

Pretty cool. I wonder how they did it. Wire EDM perhaps?

[eddief]

and a thing of manufacturing beauty.

[bicycletricycle]

A lot of this new shimano cranks seem to be glued together?

[zank]

I believe only 9000 and M9000 (not M9020) cranks are two piece bonded.

[Mikej]

Originally Posted by bicycletricycle

A lot of this new shimano cranks seem to be glued together?

Press fit.

[soulspinner]

thats pretty sweet and with all the thicknesses must be expensive to make.

[JamesEsq]

Wow, there's a lot more going on in that crank than I ever imagined.

[oldpotatoe]

Originally Posted by JamesEsq

Wow, there's a lot more going on in that crank than I ever imagined.

shimano have been Zues' at aluminum forging and manufacture for a long time. They see the ability to make aluminum bits as light and durable as carbon, for less $. The 7700/7800/7900/9000 cranks are good examples.

Plus I always think it interesting in that they have never made a BB30 crank, nor adapters for their standard crank for BB30/PFBB30 frames. shimano has always been kinda unmoved by 'innovations' or others things they see as not a great or useful design. It sure isn't because they can't afford to make it.

[MikeD]

Originally Posted by bicycletricycle

A lot of this new shimano cranks seem to be glued together?

Yes, a cap is glued on. Saw it at the NAHBS. I wonder about the strength and stiffness if it's bonded though.

[Tony]

Talking to the rep at NAHBS, the chainring is three pieces, steel for the teeth, carbon in the middle, and aluminum outer.

[sandyrs]

Originally Posted by MikeD

Yes, a cap is glued on. Saw it at the NAHBS. I wonder about the strength and stiffness if it's bonded though.

I guess the counterpoint to this is, have you EVER seen a 9000 or M9000 crank fail at the bond point? I never have, and have never heard of a crank arm failing period except under extremely heavy riders who have sheared cranks from various manufacturers, including but not exclusively Shimano (not DA, a lower end MTB model). I can't imagine Shimano would hold their highest-end product to anything less than that standard.

[bicycletricycle]

Originally Posted by Mikej

Press fit.

nope, you can see the glue line. You can see it in the DA crank above if you look carefully but this section shows it more readily.



Hollowgram cranks have been glued for a long time, not sure if they ever come apart at the seem.


nothing wrong with glue But I would Imagine that the glue joint will be an eventual failure point on these, maybe not from a mechanical failure, possibly just from environmental degradation (UV, etc.) although these factors may be meaningless in comparison to the fatigue life of the aluminum itself.

anyways, I was disappointed, always thought the forged and hollow hollowtech cranks where super cool, how do they forge something and still have a gap? hollow blanks getting put in the forge I guess.

technically blanks are called "multiples" before they get forged.


there also seems to be plastic in the chainring.

[eddief]

in our lifetime. Although, when the coastal states are under water, who knows what effect the salt water will have on that glue.

Originally Posted by bicycletricycle

nope, you can see the glue line. You can see it in the DA crank above if you look carefully but this section shows it more readily.



Hollowgram cranks have been glued for a long time, not sure if they ever come apart at the seem.


nothing wrong with glue But I would Imagine that the glue joint will be an eventual failure point on these, maybe not from a mechanical failure, possibly just from environmental degradation (UV, etc.)

anyways, I was disappointed, always thought the forged and hollow hollowtech cranks where super cool, how do they forge something and still have a gap? hollow blanks getting put in the forge I guess.

technically blanks are called "multiples" before they get forged.


there also seems to be plastic in the chainring.

[Mr_Gimby]

Originally Posted by zank

I believe only 9000 and M9000 (not M9020) cranks are two piece bonded.

So are Ultegra 6800s. Perhaps M8000 also?

Yes, a cap is glued on. Saw it at the NAHBS. I wonder about the strength and stiffness if it's bonded though.

Probably stiffer than solid alu in most cases. DA driveside arm is one of the stiffest on the market, at least according to that recent Fairwheel Bikes test. The left arm/spindle interface is what dropped it down the ranks in the overall standings.

Similar setup with the Hollowgram SI[SL2] cranks, assembled from multiple pieces and bonded together. Seen many fail, but never at the bonding.

in our lifetime. Although, when the coastal states are under water, who knows what effect the salt water will have on that glue.

Cannondale has been using bonding techniques on the SI's for over a decade now, still no failures I'm aware of...