Rockers

Hi Peter

Can you please let me know how long are the spacers that sit between your Inglis rockers and the cylinder heads? Mine are currently of various lengths which I need to do something about.

Thanks

Phil

Hi Phil
I have two groups , the older ones are 21.4mm 27/32" and the newer ones that came with the ABC NOS parts that have never been used are 22.7mm. This 22.7 does not appear to be an Imperial size that is standard and they are all very close to each other ( a few hundreths of a mm). I do not think it is that important as long as they are all the same size. The unequal length may have contributed to the cracking?
Regards Peter

Thanks Peter, much appreciated.

I did wonder if the unequal lengths of the supports had something to do with the cracking of the rocker blocks and I would imagine that the alloy casting is quite brittle.

I am going to try supports of about 19.5mm to allow me to put a steel support plate beneath rockers to prevent any further warping. Well it's a plan.

Phil

Hallo Phil,
The distance between the spot-faces on my cylinder heads to the cast aluminium of my Inglis rocker-blocks is 23.2 mm. This space is filled by four-off aluminium spacer-tubes and four-off steel washers. But, as Peter writes, the important aspect of all this is, that the spaces are exactly identical for each rocker block: the actual distance is not critical.
Your idea of fitting a steel plate is entirely pointless! Its rigidity could never approach that of the cast iron cylinder head, upon which each rocker block depends. As a precaution, you could check the coplanarity of the head's spot-faces, using a surface-plate (a largish glass mirror would serve) and height gauge (alternatively, a marking-block and set of feeler gauges) Any deviation would then need to be treated with compensatory shim-washers.
You may regard all this as a Rolls-Royce treatment of a mundane situation, but - don't we all own the Rolls Royce of motorcycles?

A footnote to my #893:- This assumes coplanarity of the relevant surfaces of the Inglis rocker blocks. But, looking at some of the photos of these stricken blocks, I'm not so sure! The casting quality often looks poor, too.
I think Wolfgang got it right: don't even attempt repairs, simply make new! Wolfgang, please advise on rocker block manufacture!
P.S., Scruff Inferior owners may think of their steeds as Rolls-Royces, but really, with just a few exceptions, they were/are the ultimate pick-'n-mixes of motorcycles! George assembled most of his bikes up from a list of about six engines, three gearboxes, two front forks, and so on, to customers' choices. However, not even Rolls had as many Parts and Assembly Inspectors as Sopwith!

Triggered by Peter's lofty ambition (ref. #841) of a fleet of Sopwiths embodying the full range of alternative rocker gear:-
Bradshaw's original rocker gear was closely-derived from that of his flat-twin light-aircraft engines. Such engines, each with a fan firmly fixed in front, rarely oversped: in this application, the rocker gear was entirely acceptable. Motorcycle engines, however, are less-governed.
Back in the early 'twenties, if there were stroboscopes at all, they would have employed mechanical light-shutters, and would have been difficult to synchronise to engines. These days, an interesting little research project could be to examine wayward motions of rocker components of the various types, at elevated engine speeds.
I've always maintained that the Inglis offering was the best of the bunch, because of its sturdiness, and four-point attachment to the cylinder head. But - who knows? - resonant torsional vibrations could have occurred in its rather long shafts, leading perhaps to degraded valve-operation and performance.
I've never inspected original, or other, valve-gear for motion-magnification (or reduction): scope here for another dissertation?