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Gibson's Valve Gear

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nickf

Posts: 781

Gibson's Valve Gear Feb 18, 2015 21:06:22 GMT

Post by nickf on Feb 18, 2015 21:06:22 GMT

I have discovered a patent (No. 12561, 1888) granted to Thomas John Gibson which I think must be identical or very close to the Gibson and Lilley valve gear adopted by the Metropolitan Railway for its 4-4-0 tank locomotives after the Allan gear with which they had been built proved to be less than ideal.

Gibson Valve Gear

The technicalities are a little too abstruse for me, but if any knowledgeable member of the forum can shed some light, I'd be most grateful.

nickf

Posts: 781

Gibson's Valve Gear Feb 19, 2015 8:51:54 GMT

Post by nickf on Feb 19, 2015 8:51:54 GMT

Having fought my way through the patent details (my brain still hurts), I think that this is a device by which a Stephenson type valve gear or its derivatives can be adjusted. The idea as far as I can see is to give the possibility of effectively lengthening or shortening the eccentric rods thus adjusting, among other things, the 'lead'.

Comparing the drawings in the patent with photographs very kindly sent me by mrfs42, taken of the valve gear of No. 23 in Covent Garden museum by himself. Angelislington and Tomcakes, it seems to me that this modification is no longer there and it is an unmodified Stephenson motion there now.

Last Edit: Feb 19, 2015 8:53:04 GMT by nickf: Spelling correction