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TOPIC: Rockers

Rockers 3 months 4 days ago #901

  • Dabney
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Paul, Giovanni, yes an excellent article that helped set the ABC in context. The description 'Steinway and Son with the flat-pack furniture' provided both a smile and a way to better consider this motorcycling paradox, thanks Ian
Last Edit: 3 months 4 days ago by Dabney.
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Rockers 3 months 2 days ago #903

  • MARTYN
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Hello all. Yes, I'm a new to the site and have found your discussions re valve gear, especially rockers, of interest.
My machine has always run with the standard Sopwith set-up. It's well worn and has quite a degree of "float". I've always run it with no clearance - or just sufficient to permit the push-rods to rotate with thumb and fore-finger. and in the thirty years Dad and I ran the bike I think he only lost one and learned early on that a nil clearance was the answer.
During those year we ran with Sopwith, Inglis, Jarvis and Taylor-Young set-ups. Having read some of the earlier posts I would agree that the Inglis and Jarvis product offer an improved longevity however the short valve operating arm puts an increased side load into the valve stem - not that the original is much better as when worn, it goes out of line/ off -centre. I haven't played with Taylor Young stuff since the mid seventies. It was probably only on one of the bikes for a couple of years and was a pain in the backside when all of the rollers dropped out when removing it on one occasion. After cleaning and reassembly but before it went back onto the cylinder head I remember turning the rocker through less than 180 degrees and found it terribly "notchy" which I believe is typical of a roller bearing used in a semi-rotational application. The Taylor-young stuff went back on but had to be replaced when the casting cracked! These days I still have Sopwith rockers, my brother runs Jarvis which he much prefers.
With regard to the Inglis set-up we too found examples of cracked aluminium casting and I believe my brother had a set of castings produced for Dad but they never got machined. Given their size and in particular the amount of metal around the spindle bush I would venture to suggest that any attempt to re-manufacture would start with a billet machined component.I wonder whether the severe nature of valve operation - which is almost snap-open snap-shut - contributes fatigue which, when coupled with worn or uneven support stanchions and a poor grade of cast aluminium, results in the failures noted.
Well, That's all for now. TTFN.
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Rockers 3 months 1 day ago #904

  • Paul
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Tiresome that my favourite after-market rocker system seem to be the most-likely to break! (Witness Wolfgang, Peter and Phil!)
To what extent Inglis contracted-out the actual supply and manufacture of their rocker components is unknown, but evidently some of their castings were not of good quality.
Although these castings were basically very simple, they needed extensive machining. Because of this, replacement blocks could just as well (no: far better!) be made from flat-bar Duraluminium stock.
Raised lettering was not featured on all original castings, and Dural blocks would not need bronze (or any other) bearing bushes.
Comments, please, Wolfgang! (Ref. #864)
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Rockers 3 months 1 day ago #905

  • Paul
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Uhhh...having just re-read Martyn's very comprehensive presentation, I see that my #904 echos some of his thoughts.
Well, Strength in numbers, then!
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Rockers 3 months 3 hours ago #906

  • Wolfgang
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Hello,

I have made my new bearing blocks, it was (for me as a layman) very time consuming, but I think it was worth it.
Maybe the drawing is useful for someone who has the same problem.
I would like to point out that the dimensions are perhaps not 100% the original, but the distances of the axle bearings and the mounting holes should be correct.
In any case they fit on my engine and she has already run with it.
I have machined the shafts so that they are without running tracks, accordingly I have adapted the guide bushings.

Greeting

Wolfgang

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Rockers 2 months 4 weeks ago #907

  • Wolfgang
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The material for the bearing block is AW 775
GBZ 12 for the bearing bushes
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Rockers 2 months 4 weeks ago #908

  • Paul
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Superb, Wolfgang, superb!
I've looked at Aluminium Warehouse's stock: a piece of high-grade plate 25 mm. x 100 mm. x 100 mm. would cost £6.50, but beware, Customers' Comments of this supplier are about the most poisonous I've ever read!
Below I've set a few pictures of my Inglis rockers, very similar in appearance to Wolfgang's.





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