Bottom brackets

[Smokin Joe]

So was it simply about saving a few grams of weight or are there performance benefits . ?

The weight saving is the performance benefit.

 

[woodbutcher]

The weight saving is the performance benefit.

I appreciate what you saying it makes sense but hell its tough if the rider is a kilo. overweight

 

[midlife]

The weight saving is the performance benefit.

Until they break..... I think this is the right pic.?

 

[chriscross1966]

Ok that is an older higher end Stronglight. Might even be ISO taper

 

[rogerzilla]

Poor old Larry. He wasn't the luckiest TdF champion.

 

[woodbutcher]

Poor old Larry. He wasn't the luckiest TdF champion.

I am a bit confused by the photo. The bike that two guys are struggling with has got both cranks on it . I suppose they think the dejected looking bloke sitting on the deck with a detached crank would like another go. Looking at him l doubt it

 

[Smokin Joe]

I am a bit confused by the photo. The bike that two guys are struggling with has got both cranks on it . I suppose they think the dejected looking bloke sitting on the deck with a detached crank would like another go. Looking at him l doubt it

The "Dejected looking bloke" was Laurent Fignon, and you don't get to win a couple of Tours de France unless you are prepared to carry on after a spill.

 

[midlife]

I am a bit confused by the photo. The bike that two guys are struggling with has got both cranks on it . I suppose they think the dejected looking bloke sitting on the deck with a detached crank would like another go. Looking at him l doubt it

His Campag SR Titanium bottom bracket axle just broke dumping him on the floor! the spare bike is the one with both cranks. After that episode there was some reflection on the use of titanium for a BB axle and I think OMAS / Campagnolo changed the desig.

 

[Ajax Bay]

@Yellow Saddle view on the use of titanium for a BB spindle?

 

[Yellow Saddle]

@Yellow Saddle view on the use of titanium for a BB spindle?

I never knew they even existed, so I definitely don't have experience.
Straight from material science then.... I don't know if that titanium BB axle was fitted into a cartridge bearing or whether the balls ran directly on a race made into the axle. If the latter, it is a super stupid idea since titanium is not a bearing material. The race will quickly gall, causing stress risers and the axle will break off.

If the axle was fitted to cartridge bearings, it is merely a stupid idea. Steel axles are solid. They have to be, because the diameter is so small. Hollowtech axles are thin-walled steel tubing but that works because of the larger OD, which works well in resisting torsion.

 

[woodbutcher]

I never knew they even existed, so I definitely don't have experience.
Straight from material science then.... I don't know if that titanium BB axle was fitted into a cartridge bearing or whether the balls ran directly on a race made into the axle. If the latter, it is a super stupid idea since titanium is not a bearing material. The race will quickly gall, causing stress risers and the axle will break off.

If the axle was fitted to cartridge bearings, it is merely a stupid idea. Steel axles are solid. They have to be, because the diameter is so small. Hollowtech axles are thin-walled steel tubing but that works because of the larger OD, which works well in resisting torsion.

How l wish l understood engineering

 

[12boy]

If your threads are not English check out Velo Orange. They have a universal BB and a french thread BB also.

 

[Yellow Saddle]

How l wish l understood engineering

Sorry, I try not to do that too much.

Basically, it is the wrong material for the application for two reasons.

1) Titanium isn't good for using as a bearing. If you look at the other recent BB thread there's a picture of a BB axle by either @midlife or @fossyant which is of the old type, where the bearing balls run directly on the axle. If this were titanium, the axle would smear under pressure, causing cracks.

2) If it wasn't the case above and the bearings were cartridge bearings (erraoneously called sealed bearings), then the balls would not run on the axle. However, this requires the axle to be thinner (because the cartridge bearings need space inside the space-restricted and standard-size BB shell). This thin, the titanium is not strong enough to put up with forces from the crank. The crank applies two forces into the axle a) a rotational force and b) a bending force. The latter force is not obvious but it comes from the pedal that twists the crank sideways. This twists the crank (not rotate it, but twist it) and the twist also goes into the BB axle as a bend.

Perhaps this is less confusing, perhaps not.

Edit: The photos just posted my @midlife below shows a third option - steel bearing race pressed onto a titanium axle. The potential weak point here is the shape of the area behind/inside the race.

 

[midlife]

First gen campag titanium axle was hollow with the steel races pressed on. That was the one that broke for Fignol

Second gen was solid but again with pressed on steel bearing surfaces.. The treads stick out of the axle like the old sugino maxy. Being solid they were more resistant to breakage (or so we were told) . Both made by OMAS of "Big Sliding" BB fame I believe.

 

[Yellow Saddle]

First gen campag titanium axle was hollow with the steel races pressed on. That was the one that broke for Fignol

View attachment 445305

Second gen was solid but again with pressed on steel bearing surfaces.. The treads stick out of the axle like the old sugino maxy. Being solid they were more resistant to breakage (or so we were told) . Both made by OMAS of "Big Sliding" BB fame I believe.

View attachment 445306

Thanks, that's some nice insight.

My guess is that there's a massive stress riser just behind that steel race i.e. a sharp, square step.

Do you know what it looks like behind there?

Finally, the Campy cups were just there 'cause the manufacturer didn't make its own cups?