BB30 - next bottom bracket standard?

[Guest Big H]

It won't work. In the Aheadset system you need something to tension the bearings to eliminate play and there won't be space on the sides of the BB to do so' date=' even if you could put the tensioning bolt inside the BB spindle tube. 

 

[/quote']

 

Lay a fork on it's side and rotate it. That is the way the BB will work. The crank axle can be any length you like and it gets trimmed to your specifications. It can have all the grooves to make sure you line it up properly. And just like you would tighten the headset with the top cap bolt, you would tighten the BB.

 

 

 

Nogal interressant jou idee.... wacky and weird maar interressant. Net so paar vrae????? Waar op die handlebars gaan jy die trappe vasmaak, watse soort trappe gaan jy geberuik en is dit drop handles of reguit soos MTB handles???????

[bob_the_builder]

 

The standard BB we have today is due for a dramatic overhaul and a move like this is one in the right direction. We need to get the BB shell much' date=' much bigger so that a far tube can replace the current small tube and solid BB spindles. The right reason for doing this shouldn'd be as this press release suggests, but to increase bearing life.

 

The bearing life in today's BBs is pathetic and for one reason only: They're too small to do what they're asked to do. Wee need to increase the diameter and the size of the balls not, as the external BB did, increase the diameter and REDUCE the size of the balls.

 

Unfortunately I'm not convinced yet, it seems as if it's all done for the sake of saving weight. I hope I'm wrong.

 

Phrase from the press release: "All other things being equal, it?s lighter and stiffer than current external-type bottom bracket systems. It also reduces pedal stance width and increases bearing life thanks to the narrower, but larger diameter, bottom bracket shell.

 

Stiffer is nonsense, we don't need stiffer and reduced pedal stance is nonsense, we don't walk with our ankles touching. The last phrase in the last sentense is a non-sequitur. Hopefully there is some real engineering in here after all.

[/quote']

 

Johan - i honestly believe the pathetic BB life has more to do with how we maintain our BB than in the design.

 

Bearings are selected based on load capacity and speed at which they will operate, if we check out the spec in a bearing cataloge of the size normally used in BB's then one can see that they operate far below the load spec as well as the RPM they were originally designed for when used in a BB, so by rights they should last longer BUT!

 

BB's are generally never maintained and only looked at when there is a problem, which by then is to late as the damaged is usually done, so they need to be replaced.

 

The BB has to tolerate a lot of dirt and water. The Bottom tube is not sealed so without cleaning and regreasing the bearings will wear and rust. I have rebuilt many BB's and whereever i can i replace OEM bearings with sealed for life bearings and then packk the tube with lots of grease during reassembly, this has increased the life 10 fold. Bearings are consumables and will need replacement at some point, manufacturers design BB's to fail so they can make money in aftermarket sales, so we ned to live with it, but make sure we extend the lifetime by stripping cleaning BB's at least once a month in the rainy season and once every 2 months in winter.

 

Good point madmarc. I am sure you can use that thinking on a few other parts of the bike as well.

 

[R2S2]

OK I'm back!

Taking a look at my trusty SKF design guide, and it shows the following:

 

Lets assume a cup diameter of 40mm (I don't actually have a BB handy to measure!).  A angular contact ball bearing that fits the BB, will have a maximum crankshaft diameter of 17mm.

 

It will have a fatigue rating of 25kg.  In ther words, it will last forever if you never subject it to forces in excess of 25kg.  In the average bike, you can therefore see that it will last as long or short as they do.  Oh yes, and it weighs 70g!

 

If you however have a look at a needle roller with an outer diameter of 40mm (the cup issue that Johan has brought up), you will see that it has an inner diameter of 32mm, which allows for a really nice, beefy hollow crankshaft to begin with.

 

It has a fatigue rating of 1039kg (I kid you not!), which means that, as long as you dont exert more than a tonne of force to it, it will last forever.  It weighs 49g.

 

So why do we still bother with ball bearings?  Cost.  Everybody knows that there is a sucker born every minute.  If you can sell him something for R1000, that only cost you R0.10 to make (ball bearings are much cheaper than needle rollers), you are in sound business!

R2S22008-04-23 05:34:13

[madmarc]

OK I'm back!

Taking a look at my trusty SKF design guide' date=' and it shows the following:

 

Lets assume a cup diameter of 40mm (I don't actually have a BB handy to measure!).  A angular contact ball bearing that fits the BB, will have a maximum crankshaft diameter of 17mm.

 

It will have a fatigue rating of 25kg.  In ther words, it will last forever if you never subject it to forces in excess of 25kg.  In the average bike, you can therefore see that it will last as long or short as they do.  Oh yes, and it weighs 70g!

 

If you however have a look at a needle roller with an outer diameter of 40mm (the cup issue that Johan has brought up), you will see that it has an inner diameter of 32mm, which allows for a really nice, beefy hollow crankshaft to begin with.

 

It has a fatigue rating of 1039kg (I kid you not!), which means that, as long as you dont exert more than a tonne of force to it, it will last forever.  It weighs 49g.

 

So why do we still bother with ball bearings?  Cost.  Everybody knows that there is a sucker born every minute.  If you can sell him something for R1000, that only cost you R0.10 to make (ball bearings are much cheaper than needle rollers), you are in sound business!

[/quote']

 

this is my point, a bearing is selected (in the design world) on load capacity. But, if my memory serves correctly (I been out of engineering for 20 years) don't needle rollers need oil as lubrication, because as i remember they are not design for grease packing??????

[R2S2]

 

Here an interesting article on electronic gruppos. I think the problems revolve more around the battery life (imagine a pro leading a race and his battery dies on him) and wet weather. the major problem is there is no back up' date=' if it fails, it fails, your race is over!!!!!!

 

http://www.pezcyclingnews.com/?pg=fullstory&id=4772

 

sorry forgot to include the link

 

[/quote']

Test-rode a TT bike with a Mavic electronic gruppo years ago.  I really failed at the time to see any benefit, as it still required you to change gears, albeit with a electronic switch.  It also came with all the risks associated with battery failure and wet electronics (this was in the UK!).  At the time solenoid technology was not advanced enough to exert the type of force required to shift the front gears, so it was really backward, as you tll had a traditional shifter for the front!

 

I believe the new stuff to be more slick and dependable, but I still would question why you'd want to get rid of a simple efficient mechanical device such as a derailleur, and replace it with some gizmo, prone to getting you stuck in a gear when it gets "load shedded", and where you in any case still have to initiate the gearchange by hand.

[R2S2]

Hi Marc,

 

You actually get sealed needles these days, so lubrication is no longer an issue!  Link below:

 

http://www.skf.com/portal/skf/home/products?maincatalogue=1&lang=en&newlink=1_5_0

[101%]

I just don't know whay the same system for headsets is not used fot BBs. Looks like the BB30 is close to being that.

 

Johan' date=' what do you think of that?

 

 

 

[/quote']

 

The 2008 Trek Madones use this system, And its IS very similar to they way an "A" headset works.

Trek not so old school after all!

 

 

[GoLefty!!]

BB30 has been a Cannondale std on their MTB's for many many years. The larger bearings required less servicing than smaller bearings thanks to more space for grease  and more space for dirt to circulate instead of pack between the balls. Dirt packing between the rollers is the number 1 cause of bearing failure. If you can circulate oil through them and filter it then the bearings will last forever, well almost.

 

cannondale'  SI Headshok system uses larger bearings for the headset also. These are not even all that well sealed but are servicable and can outlast the frame. One set lasted me 4yrs. I've never replaced the SI HEadshok Headset bearings except after the Sain2C 2006 where the biek was jet washed daily. Jet washing is murder to bearigns being exposed to corrosive material such as mud and sweat.

 

BB is not actually lighter than a std BB. Its the associated assemblies that are lighter due to reduced number of parts and bigger thinner axles etc.

[Johan Bornman]

 

cut cut cut cut cut

 

 

ngs' date=' so as to ensure the biggest contact surface possible between the journal and the engine block.  The downside is friction.  This has been solved in the past by substituting needle rollers for solid bearings in some high-revving engines, as needle rollers provide a very good comparative ratio between shaft and cage size, as well as to provide for load bearing capacity that nears that of solid bearings.

 

Need to dash, but would love to continue this discussion later today!

[/quote']

 

I am not sure what you mean by high-revving. but most car engines nowadays have no ball bearings on major load-bearing areas anymore, that being cams, cranks and the like. They rely on plain bearings with pressurised oil. I can't vouch for really high-revving parts such as turbo chargers and indeed, the gearboxes in turboprop aeroplane engines where revs apparently go into the tens of thousands, if not hundreds.

 

 

[Johan Bornman]

Johan - i honestly believe the pathetic BB life has more to do with how we maintain our BB than in the design.

 

Bearings are selected based on load capacity and speed at which they will operate' date=' if we check out the spec in a bearing cataloge of the size normally used in BB's then one can see that they operate far below the load spec as well as the RPM they were originally designed for when used in a BB, so by rights they should last longer BUT!

 

BB's are generally never maintained and only looked at when there is a problem, which by then is to late as the damaged is usually done, so they need to be replaced.

 

The BB has to tolerate a lot of dirt and water. The Bottom tube is not sealed so without cleaning and regreasing the bearings will wear and rust. I have r

 

 

Cut cut cut

 

[/quote']

I agree with you. Unfortunately these things are nowadays BBs are made to not be serviceable. Unless you really get ingenious, the only way to service them is to toss and replace.

 

The last serviceable BBs were the old cup and cone ones, which have sadly disappeared. I still have one set on my exercise bike which was made by Suntour. It has outlasted at least one bike.

 

 

[Johan Bornman]

 

Lay a fork on it's side and rotate it. That is the way the BB will work. The crank axle can be any length you like and it gets trimmed to your specifications. It can have all the grooves to make sure you line it up properly. And just like you would tighten the headset with the top cap bolt' date=' you would tighten the BB.

 

 

[/quote']

 

I dismissed your idea without proper explanation. The reason for the threadless steerer and Aheadset system was to improve the very poor quill attachment and, to get the steerer bigger for better stiffness as required by the advent of mountain biking and jumping off buildings.

 

In a way we have the same problem with the BB. We want to get the spindle bigger to save weight (ironically) but, we also want to get the bearings bigger. These are two contradicting trends. 

 

What I don't believe we have in the BB is the problem of pre-loading the bearings. We already have (or should I say, had, since it disappeared one generation of BB ago) a very successful cup system that makes it easy to carefully pre-load the bearings for just the right preload.

 

Therefore, the idea of a clamped, slotted and keyed shaft doesn't give us what we really need and doesn't solve an existing problem of crank attachment.

 

What the BB30 systems gives us is a set of cartridge bearings that don't require lateral preload and, gives us bigger bearings. The essential method of attaching the cranks to the spindle remain the same - via splines or, via a clamp and fixed press-fit as per the modern method.

 

In other words, I don't think this method will solve a problem that we have.

 

[Johan Bornman]

cut cut cut cut  

It will have a fatigue rating of 25kg.  In ther words' date=' it will last forever if you never subject it to forces in excess of 25kg.  In the average bike, you can therefore see that it will last as long or short as they do.  Oh yes, and it weighs 70g!

 

If you however have a look at a needle roller with an outer diameter of 40mm (the cup issue that Johan has brought up), you will see that it has an inner diameter of 32mm, which allows for a really nice, beefy hollow crankshaft to begin with.

 

It has a fatigue rating of 1039kg (I kid you not!), which means that, as long as you dont exert more than a tonne of force to it, it will last forever.  It weighs 49g.

 

So why do we still bother with ball bearings?  Cost.  Everybody knows that there is a sucker born every minute.  If you can sell him something for R1000, that only cost you R0.10 to make (ball bearings are much cheaper than needle rollers), you are in sound business!

[/quote']

 

Most BBs I've inspected failed because of lubrication failure combined with water/dirt ingression.  Very few - perhaps in the cup and cone days, failed from overload. Overload is easy to spot on bearings, it presents as flaky surfaces on both the races and balls.

 

Having said that, I have not looked at many of the new external bearings and the ones I saw failed because of rust and mud. However, those bearings are awfully small and if you could keep them clean, they'll break in anyway.

 

I think serviceability should come back.

[R2S2]

 

I am not sure what you mean by high-revving. but most car engines nowadays have no ball bearings on major load-bearing areas anymore' date=' that being cams, cranks and the like. They rely on plain bearings with pressurised oil. I can't vouch for really high-revving parts such as turbo chargers and indeed, the gearboxes in turboprop aeroplane engines where revs apparently go into the tens of thousands, if not hundreds.

 

[/quote']

 

First example that springs to mind is the qad cam 356 Carrera engine developed by Porsche.  Other examples include mostly race and performance engines, as the cost and complexity added by needle rollers makes it prohibitive for mass market development and manufacture.

 

In a traditional solid bearing instantaneous high loads can cause breakdown of the film of oil between the shaft and the bearing, leading to friction problems, and bearing ovalisation.

 

This in itself though is obviously not relevant to BB's, the point I was making is that from a wear and fatigue resistance point of view, as well as low friction, a needle roller is very nearly as good as a solid bearing, thus vastly superior to a spherical roller bearing.

[R2S2]

[

Most BBs I've inspected failed because of lubrication failure combined with water/dirt ingression.  Very few - perhaps in the cup and cone days' date= failed from overload. Overload is easy to spot on bearings, it presents as flaky surfaces on both the races and balls.

 

Having said that, I have not looked at many of the new external bearings and the ones I saw failed because of rust and mud. However, those bearings are awfully small and if you could keep them clean, they'll break in anyway.

 

I think serviceability should come back.

[/quote]

The issue with dirt is true, however the lad induced wear and tear aspect cannot be ignored.

 

It is very possible to manufacture a BB, using sealed needle roller bearings, that will be impervious to dirt and grime (that's what sealed bearings do best), as well as make it serviceable to the extent that, if your sealed bearing does fail for whatever reason, you can remove it from your BB and replace it with an off the shelf item.

 

This is where the manufacturers get us every time though.  Why make something that is obviously vastly superior, when you can just take old-school technology, refresh it mildly from time to time, but sell a complete new one every time the old one wears out, because you make damned sure not to use serviceable items.

[madmarc]

[

Most BBs I've inspected failed because of lubrication failure combined with water/dirt ingression.  Very few - perhaps in the cup and cone days' date= failed from overload. Overload is easy to spot on bearings, it presents as flaky surfaces on both the races and balls.

 

Having said that, I have not looked at many of the new external bearings and the ones I saw failed because of rust and mud. However, those bearings are awfully small and if you could keep them clean, they'll break in anyway.

 

I think serviceability should come back.

[/quote]

The issue with dirt is true, however the lad induced wear and tear aspect cannot be ignored.

 

It is very possible to manufacture a BB, using sealed needle roller bearings, that will be impervious to dirt and grime (that's what sealed bearings do best), as well as make it serviceable to the extent that, if your sealed bearing does fail for whatever reason, you can remove it from your BB and replace it with an off the shelf item.

 

This is where the manufacturers get us every time though.  Why make something that is obviously vastly superior, when you can just take old-school technology, refresh it mildly from time to time, but sell a complete new one every time the old one wears out, because you make damned sure not to use serviceable items.

 

 

mmmmmm i'm seeing a possible aftermarket business here, design and manufacture a BB shaft that has needle rollers which are replaceable. This is very doable in SA with our foundries and machine shops even initially on a smallscale - I must look into this!!!!!!!!

 

But then again if we want to increase the diameter of the bearing why not just go external and increase the size of the cup to accomodate a bigger bearing???

madmarc2008-04-23 09:24:35

[Johan Bornman]

 

It is very possible to manufacture a BB' date=' using sealed needle roller bearings, that will be impervious to dirt and grime (that's what sealed bearings do best), as well as make it serviceable to the extent that, if your sealed bearing does fail for whatever reason, you can remove it from your BB and replace it with an off the shelf item.

 

This is where the manufacturers get us every time though.  Why

[/quote']

 

It might be possible, but not with the current BB30 spec. You cannot separate two liquids (in this case grease and water) via a single seal, you need two, with a neutral chamber inbetween. This is the way all good hubs are designed - one labyrinth seal (known as a dust cap by some), a chamber and, a rubber wiper seal.

 

In the BB30 design there is no room for a labyrinth seal. It will need a threaded cup design of sorts and in this design the cartridge bearings are exposed to the outside.

 

Unless that problem is solved, they will not last long, no matter how good the load spec of those bearings.