Trammel plate repair on engine
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  1. #1
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    Default Trammel plate repair on engine

    I need to remove the trammel plate on this engine that drives the rods to control the valves. (I'm assuming that it is called a trammel plate, correct me if I am wrong). The reason to remove the plate is that it has started to wobble on the shaft. The problem is that I can't figure out how the plate is attached to the end of the shaft. The two fasteners are smooth and button headed. There is no access from the back side. It doesn't make sense to me that someone would have driven in tapered pins. Could they have used hot rivets? If so how would you buck them from the back?

    20180922_114302_1.jpg

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    Looks like a fairly simple Corliss valve engine. If you are refering to the big disk in the middle with the links to it, we would call that a wrist plate in the UK, and I am fairly sure that is what it is called in the original patent documentation. I can't help with dismantling methods for your wrist plate, but I would be very surprised if it was rivetted up in such a way that you could not remove it without cutting out the rivets. That would be a very poor design in my opinion. Engines such as this were usually designed so that assembly is simple and reversible without the need for special tools, although a crane and a lot of muscle may be required.

    In the museum where I work we have three mill engines with Corliss valves. All 20 odd of our mill engines are kept in full running condition and we run on steam periodically during the year. One of our Corliss valved engines(a tandem compound) had a lot of wear in the bores of its hp inlet valves, to the point that they passed so much steam that the governor could not reliably control the engine. As you will know this is not a good condition to operate the engine. We have no machine tools large enough to take the whole of the hp cylinder for valve re-boring, nor could we find anyone with (say) a really big horizonal borer to take on the job. In the end we built a line boring machine around the engine and rebored both the inlet valves in situ - a long job. Of course the valve diameter didn't match the bore diameter after this, so we had to correct this by offset turning the whole valve body. Fortunately we have lathes big enough for this job.

    The moral of the story - Corliss valve engines can suffer from wear which has to be corrected for safe operation, and if you have wobble on the wrist plate, I would also look at the valves themselves while you are at it.

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    I wonder if some mechanic hammered the rivets into holes for a face spanner so nobody could make adjustments. Try a strap wrench on the OD of the part with rivet heads.

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    Is there any evidence of a previous repair to the wrist plate shaft? It is possible that the shaft is not original and as part of the 'fix' a head was rivetted on the end of a new shaft. If so, the whole shaft, including the head which retains the wrist plate would need to come out with the wrist plate. Is there anything obvious behind the wrist plate to suggest how the shaft is retained in the cylinder casting itself?

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    First of all, thanks very much for you advice. I was able to remove the pins using a slide hammer and a little welding. Sure enough they are tapered pins that someone drove in to keep the spanner wrench holes open or to keep someone from taking it off???. Thanks so much.


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