Services for Brough Superior motorcycles and their contemporaries
Castle forks replica page last update: 10/2004
|This is the Castle fork...||...and this a 1918 J-type Harley one.
The front legs (spring shrouds) are a bit shorter, and it does not have the side dampers, but otherwise it is very much the same.
|I have got a set of J-type back legs. Maybe I will use them to build a
set of Castles, but I am not yet quite sure, as:
The problem in manufacturing these forks are the rear legs. These have an oval cross-section of about 25 x 40 mm near the triple plates underneath the headstock and are tapered down to about half these dimensions at the bottom end. The top stems are round at about 27mm diameter. To complicate things even more, they are double-walled in the region of highest bending stress, i.e. from the upper bridge casting to some 10" below the triple plates. And I consider this to be quite vital, especially if you fit an 8" brake into the front wheel!
I understand they were originally made from a long tapered tube, into which a shorter bit of taper tubing was inserted. Then the top of the tube was forged down to the 27mm diameter, the middle forged to the elliptical cross section, and finally the S-shape was formed in a die, using a big press or steam hammer.
There have been far-eastern replications with rear legs machined from solid. These were, of course, very heavy! But there must be someone in this world who is making decent replicas for the Harley restorers. I was told somewhere in Macedonia...
If you know about somebody who is replicating the J type Harley forks in a good quality I will certainly appreciate any hint!
OK. In the meantime I will try to do something about the front legs:
|I have not found a promising source of replica castles yet. But I have
been asked a few times if the front bridge casting is available somewhere.
Thus I decided to make that one. Do a drawing of it, make a pattern, have a few cast, and machine them. All of this can be seen here.
Simple as it looks, it proved to be a time-consuming job, but what else could I have expected ?
|Now, to make a set of front legs you need the bottom lugs as well. I thought I'd fabricate me a pair from solid, but then a friend talked me into making another set of patterns...|
|12/2003: I have now finally had a few of these cast and have machined them.|
|Meanwhile I have machined a few handlebar centres.|
|12/2003: And I have machined a pair of top clamps|
|A friendly Harley guy from the United States has now sent me some 4130
Chrome Moly tubing in 1" 18 swg for the spring shrouds. Thank you ever so
This has enabled me to produce a few front legs.
to be continued...
|Now I have given up any hope of sourcing a decent set of replica fork
legs, and have decided to use the old J-type Harley ones I have got.
Besides a lot of bending and straightening they needed replacing the stem and putting the little damper lugs on.
|And I have produced a pair of the so-called spring abutments (or spring plungers)|
|I have, in the meantime, more or less completed the forks, but they still want brazing up and making all the damper bits.|
|And I have had some laser cuttings made for the side dampers.|
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