Author Topic: Douglas Patents of Note 08  (Read 6237 times)

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Offline Doug

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Douglas Patents of Note 08
« on: 07 Dec 2007 at 04:18 »

Improvements in Spring Forks for the use on Cycles, Motor Cycles, and the like.

Patents of Note 08
Patent No.: 5434
Application: Apr. 10, 1915
Complete: Sep. 30, 1915
Accepted: Dec. 02, 1915

The propensity for breakage of coil springs in this era, allowing the front suspension to collapse, must have prompted this design.  A set of coil over damper units and they could have pre-empted Earls by several decades!  However superficially similar, this is not what I would call a true leading link design.  Nor despite claims in the patent, would it seem to have offered any practical advantage in providing a laterally stiff fork.  The upper links would provide the same lateral stiffness as with their application to a girder fork design, but the leaf springs at the bottom would not appear to offer any clear advantage over links. The stability may even be worse, due to the spring’s longer length and lack of lateral stability compared to a short swing link or a proper leading link front swingarm.

Mainly it seems to be a way to use a cantilevered leaf spring for front suspension without infringing on existing (and dare we say better) patents.  This design has not been seen implemented.  Note the rear anchorage for spring is just a hole punched through the leaf, secured by a bolt.  Is it just me, or does that shout ‘fatigue crack!’  One wonders trivially if the mudguard was to remain fixed or to move with the suspension.

© 2007 D. Kephart, Glen Mills, PA, USA