Dave, Jan Heine did a test of fork flex in an issue of BQ (VBQ?) in which he placed a load on the handlebars and measured the flex. As I recall, he found that forks with more curve flexed more. Also, not surprisingly, that thinner diameter blades flexed more. And I also recall that the placement of the bend made a difference, the lower on the fork leg, the more the flex. The difference was quite significant. I'm too lazy to get up right now and search through my back issues, but I'm sure a more industrious Bob will chime in with the details.
John
On Tue, Mar 10, 2009 at 5:07 PM, Dave Porter <frogeye@porterscustom.com>wrote:
>
>
> Hmm,
>
> Regardless if the blade was bent or curved the axle ends up in the same
> place. The material, steel, is very rigid, even more so when the axle is
> installed. This results in a box like structure that has no movement that
> could be construed as a "suspension". If in fact the blades did move as the
> implied logic states then the steel would become brittle from work
> hardening
> and fail in short order. That simply has not occurred. Dampening, as such,
> is a result of mass, frame angles, wheel & spoke deflection, and a
> pneumatic
> tire primarily.
>
> The bend or curve is there to achieve a desired caster (trail) or to
> accommodate fenders, mud flaps and toe clip clearance. IMHO
>
> DaveP
>
>
>
> frogeye@porterscustom.com
>
>
>
> Porter Customs 2909 Arno NE
>
> Albuquerque, NM USA 87107
>
> 505-352-1378
>
> 1954 BN2 1959 AN5
>
> Porter Custom Bicycles
>
>
>
> cars:
>
> http://www.britishcarforum.com/
>
> gallery:
> http://picasaweb.google.com/
>
>
>
> blog: http://porterbikes.com/
>
>
>
>
>
> -----Original Message-----
> From: classicrendezvous-bounces@bikelist.org
> [mailto:classicrendezvous-bounces@bikelist.org] On Behalf Of donald
> gillies
> Sent: Tuesday, March 10, 2009 3:51 PM
> To: classicrendezvous@bikelist.org
> Subject: Re: [CR] Ralieg frame in Team Colours 0 Ebay 400032976224
>
>
>
> Harry,
>
>
>
> I think I know what Norris Lockley is referring to in the 'Competition
>
> Team Pro Bike' on Ebay (which, according to its serial number, is a
>
> 1979 comp gs model painted in red/yellow/black paint, with a yellow
>
> head-tube.) By the way, after 1974 raleigh (but not ilkeston)
>
> continued to produce bikes with yellow head-tubes; for example, the
>
> Raleigh-Record level bike ALWAYS had a yellow head-tube, it never had
>
> a black one.
>
>
>
> Reynolds produced 2 versions of pre-raked 531 fork blades. The
>
> earlier "curved" blades contained a smooth and continuous bend, all
>
> the way out to the dropout eyes. Example :
>
>
>
> http://img.auctiva.com/
>
>
>
> there was a latter type of fork blade, where the blades seem to have a
>
> 135 degree bend at 3/4 down the blade, from whence they go straight
>
> out to the dropout eyes. So these blades are "bent" at a single
>
> location, about 3/4 of the way down the blade :
>
>
>
> http://img.auctiva.com/
>
>
>
> Norris is complaining that these "bent" blades do not absorb shocks as
>
> well as the original "curved" reynolds blades. In my opinion, the
>
> reynolds blades are half the value of a reynolds 531 frame's ride, so
>
> he may well be correct. However, I'm not sure the bend is creating
>
> the problem, it may be that the bent blades are not "taper gauge"
>
> which was a process that produced uniform wall thickness throughout
>
> the earlier blades.
>
>
>
> In any event I have no firsthand knowledge about which blades produce
>
> a harsher ride, and why ...
>
>
>
> - Don Gillies
>
> San Diego, CA, USA
>
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>
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-- John Wood Missoula, Montana, USA
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