Thursday, 24 March 2011

About those Lambert / Viscount Death Forks

The amount I have written on this blog so far without mentioning ‘death fork’ and Viscount or Lambert in the same sentence is probably a record.  Now I will say a bit about it.  Despite dire warnings about ‘death forks’ on the Internet, there are very few facts to back them up.  

To begin at the beginning, even the earliest Lamberts (like my 1972 gold plated Professional Grand Prix) had a cast aluminium alloy front fork (the part that holds the front wheel).  As with most traditionally constructed bikes, this was attached to a steel ‘steerer’ - the part that turns in the headset bearings and into which the stem holding the handlebars fits.  In the early 1970s aluminium forks were extremely innovative if not unique.  The idea was (of course) to reduce the weight of the bike.  Incidentally the feel of the bike was changed, because aluminium behaves differently to steel under stress.  (The modulus of elasticity is different.)  Some people don’t like the ‘feel’ of ally forks.

Unfortunately, there were accidents resulting from sudden catastrophic failure of Lambert forks.  If you are travelling at any speed, the failure of anything at the front of the bike - fork, wheel, stem or bars - is frightening and potentially very serious.  I know of a friend of a friend who experienced Lambert fork failure and was scarred as a result.  So I don’t doubt the reality of an ‘injury fork’; even if no-one was killed.  The number of forks that broke has been reported as less than 1% of the 30,000 or so bikes made with the ‘death forks’.  Unacceptable, but not as bad as some would have you believe.

Failure seems to have been associated with the method of attaching the fork to the steerer.  The first picture shows this.  The crown of the forks had an integral extension that fitted into the steel steerer tube.  To make this joint as firm as possible, the steerer tube was heated, making it expand, before fitting it over the crown extension.  When it cooled, it contracted and gripped the alloy part firmly. A couple of dowel pins (probably spiral pins like these) were inserted in holes running front to back.  This is the first version of the alloy fork.  The second version was similar but had the pin put through from side-to-side.  This might have been an attempt to reduce stress concentration in the part.  However, both these versions were known to fail, usually as the result of an impact of the front wheel with a kerb or other immovable object.  Breakage occurred near the base of the fork extension.  The article accompanying these diagrams calls these two types the Lambert forks and the third version the Viscount one.  The article is by Yamaha so this may just be a device to distance Viscount from the Lambert failures.  My other Lambert bike has a type three fork, although a replacement - perhaps a partial product recall - cannot be ruled out.
The third version of the forks, presumably introduced because of continuing failures of the earlier versions, brought in a separate steel crown extension.  This screws into the crown of the forks and is secured with Loctite™.  The mounting bolt for the front brake passes through the whole assembly and gives further security.  The upper part of the steel insert fits into the steerer and is secured with a pin.  Information on the Internet is that the third type is very reliable.  They are still found on Viscounts that come up for sale, (they were only fitted to the top of the range Aerospace Pro), which have notched up considerable mileages. They were used on the works team bikes in road racing and by others for cyclocross.  See this Cycling Touring Club (CTC) forum for more details.  Nevertheless, at some point in the late seventies, the new owners of the marque, Yamaha, decided to mount a full-scale product recall of all alloy forks and free replacement with steel (Tange?) ones.  I think this must have been a response to continuing bad publicity / bad mouthing about the Lambert forks and the difficulty of telling one type from the other.  It is clear that Lambert did not handle the fork problem well and, despite the efforts of Trusty/Viscount to sort out this and the early quality problems, its shadow was still hanging over the bike into Yamaha times.

It is actually quite easy to tell if your bike has a third version fork or one of the earlier ones.  First check with a magnet or by inspection that you have alloy (non-magnetic) rather than steel forks.  If the latter, you need worry no further.  Most Viscount steel forks have traditional square shoulders with lugs.  Some have sloping shoulders and look superficially like the alloy forks.  Alloy forks were always supplied unpainted; steel ones were painted and often (depending on the model) half chromed.

To check alloy forks, remove the front wheel and the front mudguard (fender) if fitted.  Ideally, turn the bike over to get a good look.  If the underside of the fork crown - i.e. between the ‘legs’ - is smooth alloy; then you have an early version.  I would not suggest that anyone rides a bike with one of these, other than for a sedate Sunday afternoon turn around the park.  If you can see a circular indentation in the centre of this part of the forks that you can’t clean away (!), test it with a small magnet, such as a round fridge magnet.  You should be able to detect that in the centre there is a magnetic steel part, whereas the rest of the fork is non-magnetic.  I am quite happy to ride a bike with an alloy fork of the third kind on a daily basis, as I might with any other twenty-five year old component, but I cannot advise readers what to do.

Finally, in case people think that Lambert and Viscount are the only bikes that have ever had problems, see this recall notice for forks used on a Cervelo bike.  As it says ‘The forks steerer can break during normal use.  In some circumstances this can cause the rider to lose control, fall and suffer serious injuries’.  Might have been written about the Lambert ‘death fork’.

Thanks to the careful reader who pointed out that the Trusty factory was in Bilston, a former steel-making town about 4 miles south-east of Wolverhampton, not in Birmingham as I said.  At least I got the region right (West Midlands).

Friday, 11 March 2011

Design Magazine May 1976 - details of Viscount bike

A friend (thanks Steve) has pointed out to me an interesting article on Picasa, reproducing part of the May 1976 Design Magazine.  This has an ad. showing a Viscount Aerospace Pro (GB£115 - about US$188 at today's rate of exchange).  It mentions the Aerospace range starting with a bike for just under GB£80 (US$131).  What model would that have been?  Sounds like incredibly good value, even in 1976.  At this time the Viscount brand was being produced by 'Viscount-Trusty Ltd.' of Potters Bar, Hertfordshire, UK.  (Potters Bar is on the outskirts of London.)

Also from the magazine is a one page article on the Viscount Aerospace bikes that has interesting photographs of a Viscount bottom bracket, pedal and hub that have been sectionalized to show how they were made.  The article quotes Cycling magazine as saying that the Aerospace Pro could be used for 'road-racing, time trialling, cyclo-cross, training and touring'.  It also mentions a competition model made by Trusty, 'slightly lighter' but twice the price.  Does anyone know what bike that was?   Any pictures or descriptions?

Many thanks to 'ichibyoshi', who posted this very interesting document.  His (could be 'her' I know) other pictures and name suggest a home in Japan.   My thoughts are with you and other citizens of Japan and countries of the Pacific whose lives, homes and livelihoods are threatened by the earthquake and tsunami that happened today.