SUSPENSION FORK
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larger version.
After taking into considerations all the details discussed on
the lowracer list about making a suspension fork, I went ahead and made one. The stanchion
or slider tube, which slides up into the steering tube, is a chromed 7/8" BMX seat
post. The stanchion tube slides on 2 bronze bushings, which are pressed into the lower
half of the threadless 1 1/8" steering tube.
The fork is a cut down 27" fork that I cut the steering
tube off and then reamed the crown to accept the 7/8" stanchion tube. The spring is 3
1/4" long and is retained by a sleeve in the top of the steering tube which is held
in place by a pin that slides through a hole in the steering tube and sleeve. The top of
the sleeve is used to hold the star-fangled nut for the threadless headset.
The scissor linkage is composed of 4 by 1/8" thick
chromed plates which came from a rear rack. Each linkage point has small nylon washers,
and are held in place by M5 bolts and nylock nuts. The linkage has been designed so that
all slop can be eliminated even after long use.
The fork is 335mm from axle center to fork crown seat, a
Ballistic fork is 345mm. The steering tube is 175mm long. The axle center to top of the
fork crown dimension is 267mm (10.5"), the maximum tire size on a 406 rim is
1.5". Maximum allowable travel is 38mm, the expected travel is 25mm, Ballistic claims
40mm. The fork crown is half the width of a Ballistic fork. A Ballistic fork weighs with a
160mm steering tube 4lb., this fork weighs 2lb.12 oz. The most important feature of this
fork is the crown width, especially on a SWB lowracer.
I plan to fit this fork to my Bike Friday to test it, since I
haven't even started the bike it's meant for yet. Using the suspension seat post spring
I'll build one of these forks for a 1" steering tube so Alan's bike will then be
fully suspended.
