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

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

This is where the future of the bottom bracket lies:

Yes. The pack of clever marketing. Traditional ball bearings are not ideal, as the wear characteristics, and load bearing capacity is not class leading. All I can assume is that they are a holdover from times when bearings were expensive, and the ability to make up for wear by tightening "cups" was the accepted norm. With sealed bearings (that most BBs have these days), that has become a moot point, and I can for the life of me not understand why we still see them in bottom brackets. A far better approach would be to pursue the use of conical or cilindrical roller bearings. Even better would be needle rollers, as these have immense load bearing capacity, as well as very low rolling resistance, not to mention low weight and compact design.

In the case of modern aluminium heads, use is no longer always made of white metal, as the oxide layer that forms on exposed aluminium is crystalline in nature, and does exactly what Johann said about the crytals in white metal. The crankshaft and block is another matter altogether, and there you will still find many white metal bearings. In some high performance car engines (notably Porsche, who patented it) a material called Nikasil is plated onto aluminium wear parts to make them even more wear resitant. Not on your Alfa though...

I side with JB on this one. If you are sentimental, put the old frame in a picture frame and hang it on a wall! Sure you can weld it, but do so only if you don't value your own physical wellbeing. Bikes are typically made from 6000 or 7000 series aluminium, that has to be heat treated after any work has been done on it. Both welding and bending hardens the material making it brittle, and the only way to reverse this is to perform heat treatment on it. Incidentally, just riding the aluminium frame causes work hardening, and fatigue, which is why it is generally agreed that these frames have a finite lifespan, depending on how much abuse you throw at them of course! Case in point: Had a very nice custom built Principia frame a few years ago, which got dented in a crash. Against the advice of everyone in the know, the insurance guys on the advice of the bike shop decided that the frame could be repaired. Looked nice enough when I first got it back, but didn't last a year before the cracks started showing again. Very hard lesson to the insurance guys, as the initial repairs not only cost them a fortune, but also nullified any waranties, leading them to a very expensive replacement excercise!

When I was a laaitie we used whatever grease we could find in the garage, and never had any issues other than black marks down our legs or trousers. Any lube is better than no lube!

If the bearing isn't the culprit, then rather leave it in place, as you risk damaging it when you remove it - unless of course you were planning on replacing it in any case. If you do replace the bearing, tap it back into the hub with a light hammer and wooden block, using the latter to protect the bearing from the hammer. It does make things a bit easier if you apply a little oil or thin grease to the sliding surfaces before starting.

Sealed bearings cannot be serviced and must be replaced. Are you sure the issue with the hub lies with the bearing? The bearing is probably pressed into place. Best is to use a bearing puller, but if you don't have one you can lightly tap it out with a wooden block and a pin of sorts, working you way around the circumfence of the bearing. Heating the hub slightly with nothing more than a hairdryer could make this a bit easier, as the aluminium hub will expand more than the steel bearing, thus loosening it.

There is a chap on this board that goes by the name of Razzo. He does the most amazing fillet brazing I have ever seen in my life. He built a frame that was shown off on this board about two years ago, and that took its rider to I think 7th in the vets world triathlon champs. Not commercial stuff though, as he does it for the sense of achievement, so park that idea of getting him to build you one!

Hope it isn't a re-post! http://www.rouesartisanales.com/article-17212505.html

Jaaa Boet... I was wondering again the other day, how we got from no outages a year ago, to huge outages right now! My logic says if capacity was a problem, outages would have increased at a rate that is equal to our economic growth or thereabouts...

I had a double whammy of "Africa strikes back" today. Electricity was out (so what is new?), so earlier I had to drive all the way to Illovo from Rivonia just to get a take-away burger. Now that wouldn't have been so bad if it weren't for all the bl00dy "Code 10" drivers on the roads. What is a "Code 10" might you ask... Well they generally look and behave exactly like taxi drivers, but drive all sorts of regular cars. -They don't stop at intersections where the lights are out. -They don't keep to the right lanes. -The purpose of hazard lights on their vehicles is to warn you that they are in the process of doing the illogical. Phuck I'm frustrated!

I used to work in the polymers industry, and most (if not all) of these products are completely bogus. So much so, that du Pont (who own the trademark "Teflon") won't sell their product directly to any engine additive manufacturer, nor endorse it, nor allow the word "teflon" to be used on any such product.

In summary...

They didn't perhaps say anything to you about the chip that I paid for, oh about 4 years ago, but still haven't received?

Very good value for money. The hubs are especially well designed, and I believe a cheapened version of what you'll find in some of their high-end wheels.

Panda also used to have them on their site.

Thanks Lefty. I suppose however that, the moment sanity shone through, those who really needed to read it got all dyslexic and left!

I'm not laughing Ti... My "other" bike is a 1980's Peugeot Rapport with, wait for it... ...a mix of Suntour, Shimano 600 and Shimano 105, with downtube shifters, an original suede finish Anatomic saddle, and toeclips. Haven't ridden it in years, but it will break my heart to throw it away! I guess my age is starting to show, so from now on I too demand to be called "Oom"!R2S22007-03-20 09:09:06