Stuart 5a hybrid?

[Mike Rometer]

Hi Mike, these two mains have good sized wick-feed oil cups already fitted. I could of course easily remove them and cap the inlets, but that really would only work for the right-hand end as the c/shaft isn't drilled the other (Left) side.

My leaning ATM is to drill the journal at the top in the normal 'engine stop' position i.e. against a compression, so that remaining oil in the cup will be gathered in the hole, and hope that the 'wedge effect' will feed the oil whilst running, especially if I 'lead' the hole, but that too may not work entirely if it should stop on the other compression.

[Mike Rometer]

Progress is still being made, but I have come across what I think is a drawing error for the 5a, which the top end of this engine undoubtedly is. I have got as far as trying to set up the valve timing. I had previously made the valve-slide to the dimensions given on the 5a drawing, without reference to the port drawing. The dimension across the outsides of the inlet ports is 1- 1/4", but the dimension for the valve length is given as 1-9/32", quite plain and easily readable. Should that not be more like 1-9/64", i.e. just bigger than the ports so that still only one is uncovered at a time??? It just seems an awful lot of lead (inlet ports are 1/4").

A Google for known errors has not been forthcoming.

[Lopez Mike]

All of my 5A information is at home and I'm down in Baja 2000 miles away. Anyone else with some info?
Mike

[Mike Rometer]

Hi Mike, I've been puzzling all afternoon on this one, it may be that it is correct, and the lead is adjusted by the eccentric position (30 degs). It just seems a lot to my 'loco' trained brain. I've started to re-assemble it, as is, to try rotating the eccentrics to see if I can get it to a working position. Any further thoughts would be much appreciated.

Hope you're enjoying your trip away.

[artemis]

Progress is still being made, but I have come across what I think is a drawing error for the 5a, which the top end of this engine undoubtedly is. I have got as far as trying to set up the valve timing. I had previously made the valve-slide to the dimensions given on the 5a drawing, without reference to the port drawing. The dimension across the outsides of the inlet ports is 1- 1/4", but the dimension for the valve length is given as 1-9/32", quite plain and easily readable. Should that not be more like 1-9/64", i.e. just bigger than the ports so that still only one is uncovered at a time??? It just seems an awful lot of lead (inlet ports are 1/4").

A Google for known errors has not been forthcoming.

Put your dimensions in decimals, not fractions and:
1-1/4" = 1.25"
1-9/32" = 1.28125"
1-9/64" = 1.140625"
1-9/64" is smaller than outside distance (1-1/4") between the steam ports; you want 1-9/32" which will give just 0.03125" total overlap.

[Mike Rometer]

Progress is still being made, but I have come across what I think is a drawing error for the 5a, which the top end of this engine undoubtedly is. I have got as far as trying to set up the valve timing. I had previously made the valve-slide to the dimensions given on the 5a drawing, without reference to the port drawing. The dimension across the outsides of the inlet ports is 1- 1/4", but the dimension for the valve length is given as 1-9/32", quite plain and easily readable. Should that not be more like 1-9/64", i.e. just bigger than the ports so that still only one is uncovered at a time??? It just seems an awful lot of lead (inlet ports are 1/4").

A Google for known errors has not been forthcoming.

Put your dimensions in decimals, not fractions and:
1-1/4" = 1.25"
1-9/32" = 1.28125"
1-9/64" = 1.140625"
1-9/64" is smaller than outside distance (1-1/4") between the steam ports; you want 1-9/32" which will give just 0.03125" total overlap.

Ron, you are absolutely right I should have stuck with decimals, then I might have seen my error in the data I presented, the figures should have been,

1-1/8" = 1.125"
1-9/32" = 1.28125"
1-9/64" = 1.140625"


Making the total overlap 0.15625 which seems a lot.

with 1.140625 it would be just 0.015625. Perhaps not enough?

[Mike Rometer]

Well today the proof was supposed to be in the pudding. Unfortunately only 50% of it was. Having got the last of the pieces back on I HAD to try it on air. The 50% bit is that it runs fairly well forwards but doesn't run properly in reverse, there must still be a bit of valve tweaking to do. I left the slide length 'as was' and tried for the best setting I could get. I managed to get it to open and close in more or less the right places, but it never sees a full inlet port, in fact not much more than about half.

S.Turner 5a (27) (450 x 677).jpg (73.57 KiB) Viewed 10475 times

No laughing at its plinth, it had to have something to keep the flywheel off the deck. Well that's my excuse anyway.

Late Edit

Gave it a rest for a while and then added some steam oil to the valve chest. Now it runs both ways and has run for about half an hour. It is getting noticeably more powerful and smoother running, and using less air. I think the valves will still need a small tweak, but only a touch.

[Mike Rometer]

The detail of what has been done is that, there were no proper cylinder cover, or steam-chest, studs. Obvious from first glance.

On removing the steam-chest cover there was no valve-slide or locking nuts.

On removing the cylinder there were no rings.

On checking the eccentric straps they were loose, and when tightened they bound up solid.

On checking the big-end, it too was loose, and when tightened bound up. On further checking the shells weren't round, but stepped. (either orientation).

On checking the small-end, the gudgeon (wrist) pin was too tight and the bush had to be reamed.

On checking the crank shaft there were various drillings for oil-ways left open ended, and no continuous oil feed gallery for the big-end.

On checking the main bearings they too needed a touch or two with a reamer to allow free rotation.

On re-assembly the cross-head guide needed re-aligning and adjusting, The eccentrics and valve rod were miss-aligned, and there was no method of locking the eccentric settings. The valve rod was too long. There was no suitable gland on the valve rod (now "O" ringed) and none at all on the piston rod (now, good old, graphite yarn).

It has to be said, it wouldn't have been too much more trouble to have started afresh, when all the cleaning up and re-painting is taken into account; but a quite enjoyable project all the same.

The next one could be a building a twin, for which I happen to have the cylinder block for already!

[DetroiTug]

Mike,

That's a nice looking engine. Yes, any partial build always has it's maladies.

On the eccentric strap, I've found they need to be "ran in". If one machines them with no clearance, they may spin freely but will soon become loose when the high spots wear down. That is how mine were. After I ran it for 40-50 hours, I pulled the caps and drug their faces on a file and kept checking for clearance. I've gotten them too tight doing that. Put some thread locker on the bolts and adjust them up where they will spin and keep them oiled. They will eventually wear in and the strap can be tightened fully. It seems after this initial run in if they are kept lubricated they stay tight and do not readily develop clearance again - mine haven't anyway. Apparently all surfaces are now contacting.

On steam engines one shouldn't be too hypersensitive about fit. Comparing them to IC engines (which is where most of us cut teeth on engine mechanics) which are a totally different animal, the steam engine will be quite happy with tolerances for years that would render an IC engine inoperable in seconds. Tightening your components and them being too tight may have been for the purpose of "running in", by the original builder. Of course the "stepped" bores were probably not intentional and probably the result of a dull or too long - too much cut on a boring bar.

-Ron

[Mike Rometer]

Them's good thoughts Ron! The straps are still inclined to run a touch hot after the initial hour or so of running, so I don't think I got 'em too loose. It's running even better and with much less air today.

I got the impression that it had never got as far as having been got ready to run, merely 'made' with the 'fettling' left and never attempted. I'll run it some more and then re-adjust the valves, see if I can get it to run near even both ways.