The Home Machinist!

Some one from this board told me....

Blue prints dont always jive with reality. It is often best when you get what ever drawing to do the math yourself. Then just use their drawing as a guide.

Funky I know.

sometimes if you don't tempt fate a solution is never found. now what we want to hear is positive track reports.

Hammermill, some of us dont want to hear about it, we want to see it How about a video ?

LOL! Well a positive track report isn't going to happen today!

Despite the promising start on the treadmill yesterday, when I got on the rails today the performance was nearly as dismal as previous attempts so I have resolved to 'scramble' the valve gear (put everything out of alignment) and start from scratch, assuming nothing, one step at a time, and verifying every step of the way.

I may have gotten one hint today. When I was doing the oiling-up before the run I noticed the two eccentric straps on the right have been rubbing hard against each other probably accounting for the squeaking I have heard from time to time and probably indicating one or both of the eccentrics have moved or come loose.

I will post again when I know more .......

Starting at the beginning- !, Disconnect steam lines from cylinders, make up temporary piping so you can put air pressure to either or both cylinders as you wish, jack up engine so wheels can turn without engine turning, remove drain cocks, remove front cylinder covers and see whether the pistons cover the draincock ports at the end of the stroke, ( If they do you are in trouble, remover rear covers as well to see if the same problem exists there, probably you will have half the motions on the bench by now!) get your Dremel out and grind grooves from the end of the cylinders to the drain cock ports, reassemble and continue. Set up and test each side independently with the drain cocks on the other side removed to avoid any compression or timing problems on the side you are not adjusting confusing you. Have fun work safe Ps you would have had a great time at Montreal this weekend Regards David Powell.

Ok Dianne, you will need to take the valve covers off to time the engine properly. With the cover off put the engine in full forward and roll or rotate one side into the top dead center position. Look where the slide valve is located, you should have the slide valve just bearly start to show the admission port. Next rotate the engine to bottom dead center and notice where the valve is it should be in roughly the same position but on the back side. Adjust the valve rod if one end shows more admission port then the other. Now repeat this on the other side. With Stepenson valve gear they either run great in forward or reverse but not both.
Hope this helps.
-Kevin S.

Hi again! There appears to be some confusion among the replies. The actual position of the valve on the spindle only determines the BALANCE of work done between the two ends of each cylinder. The basic TIMING is determined by the angular setting of the eccentrics. Unfortunately, often thanks to errors in the basic geometry of various valve gear layouts, then added to by wear and manufacturing errors, changing the timing by altering the angular setting of one or both eccentrics MAY make it necessary to change the position of the valve on the spindle to bring it back into balance. A further possibility with Stephensons ,While I fully admit is is a bodge, or fix and not a proper cure which an engineer in a drawing office would advise, it is possible to work around some errors by altering the length of one or both eccentric rods, but, the most important part of this action is to analyse what is needed first. Many years ago I was involved in the restoration of a full size compound steam roller with Stephenson's gear. A number of efforts at shifting the valves on the valve spindles brought reasonable but not really good results, her regular driver took her on a 20 mile trip and came back with her sounding wonderful, in all notches forward and reverse, he had shimmed the high pressure forward eccentric rod foot with two thicknesses of the pop can he had in his lunch pail, and shifted the valve a tiny bit towards the crank on its valve rod. IF that will drastically improve a full size one just think how near you must get a little one.If you want to see how mine go look at " Small wagon test run" on You tube.Regards David Powell.

Hi,

Dave knows more about valve setting, etc. than I ever will, but based on my experience with the Dart chassis (inside slide valve Stephensons) it is very important that all the eccentric strap center distances (and the rest of the valve gear components) be made identical to within a thousandth of an inch or less if possible. I did that with Dart and made the expansion link on the little CNC mill so that too is to tenths. I still have to play with the settings some more, but as is, it runs equally well in forward and reverse and notches up almost to center in both directions. I made # 10-32 threaded adjustment rods for valve position adjustments because what was there wasn't accurate enough. I found that turning the nuts 2 flats made a noticeable difference in the performance. From this you see that even in 7 1/4," valve setting has to be very precise and logically in 3 1/2 inch gauge, proper valve setting would have to be even closer.

I still have to advance the eccentric positions slightly so it will run in mid-gear, but that's a job for another day.

Fun & games.

Richard Trounce.

Here is one of the most accurate dissertations regarding valve setting:


http://books.google.com/books?id=wiMxAQ ... on&f=false

Best regards,
Dave