Allchin slide valve help please

[Robert DoddsParticipant @robertdodds43397]

Hi all,

I'm not at all into TEs but am intrigued with mechanical motions. I've just been looking at a simulation of Stevenson (not crossed) that shows the eccentric pins at 80 degrees either side of the crankpin. Am I mis-reading Nigel's pictures because to me the eccentric pins look as though they are at 100 degees or more eitherside of the crankpin.
Nigel, Where is your 82 degrees referencing to and from?
Is this something to do with the crossed eccentric links that is not yet apparent in Nigel's setup?
As previously noted by others, What can be seen in the photos looks exceptional

Bob D

[GoCreateParticipant @gocreate]

Hi everyone

Thanks for all the interesting replies.

I am not sure what you mean by normal or crossed eccentric links but I hazard a guess that these are normal and crossed would have the eccentric arms connection to the reversing link swapped over.

For your reference I have attached some info from the Allchin book which I hope answers your questions.

For now I have to leave it a few days. I feel confident it's OK and will run it on air a a couple of weeks.

Thanks

Nigel

[JasonBModerator @jasonb]

As I said at the beginning the eccentric should lead the crank by 90deg plus 7-8deg , Hughes says 7.5.

So the angle between crank and eccentric is 90+7.5 = 97.5

The angle of the template is 82.5deg being the complementary angle of 97.5

This is the drawing I have given several people on how to get the initial timing of a TE, which is basically the same. based on a 4 shaft engine where the flywheel turns clockwise in forward gear. The template is held against the horizontal boiler top.

Edited By JasonB on 12/08/2013 07:50:18

[GoCreateParticipant @gocreate]

Hi Jason

Thanks again for your info.

Something must be wrong on my engine, set at the 82.5 deg (97.5 deg the other way round) Hugh says that the slide valve should reciprocate with the reversing link in mid gear such that as the crank is rotated the inlet ports should just become visible via a thin black line appearing.

However, on my engine, in mid gear the reciprocation of the slide valve was only 1mm, significantly less than indicated by Hugh's book. Also in full gear the inlet ports did not open until the crank turned through about 40 deg.

So then I must have made some error somewhere, hopefully something I can identify and fix easily.

Thanks again

Nigel

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