Building a 31/2" Gauge Locomotive Engine

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NickG:
Stew, does this not tie up with the dimensions on the drawings?

I definitely feel confident it will work when this is sorted. It's a comlicated beast!

Nick

sbwhart:
Hi Nick

No it doesn't tie up with the drawing I measured and remeasured everything up and I've made it very close to drawing, I,ve taken an additional 1.1mm per side off the dummy valve, this wasn't quite enough so I've just taken another 0.25mm per side off this is a little too much I think 1.2 mm per side should just about do it.

At this the inlet port opens half way, I was under the impression that it was to open fully but I really can't see how to get it to open fully with this set up, it starts to close at bottom dead centre and it fully closes half way to back dead centre, giving the 75% lead Curly talked about it the write up.

Had a bit of excitement with the excentric tumblers the little slotted grub screws that locks it in position gave up on the job what with all the adjustment I was doing the slot strip I couldn't get it in and I couldn't get it out, so with a hand drill I drilled it out using the tapping drill size, cleaned it out with a tap with all the lead ground off it, worked a treat panic over :thumbup:

Stubborn and won't be beaten

Stew

Stilldrillin:

--- Quote from: sbwhart on September 01, 2009, 10:42:20 AM ---Stubborn and won't be beaten

Stew

--- End quote ---

By `ek Stew........ Yer not wrong! :thumbup:

I really admire your tenacity...... :bow:

David D

NickG:
Stew,

I will take the valve chest cover off mine and measure. Looking at the drawing, it does seem like there is too much meat on the valve though, it calls for X = A + 3/16" but as you say, I don't think those design dimensions you mention below are the whole picture. Surely the overall length has to be some sort of function of the maximum throw of the eccentric as well.

The port should open fully though, you need to be able to set the valves as per those instructions otherwise it will never work as well as it should. Do you have the screw reverser set to full forward or full reverse?

Nick

sbwhart:
Hi Nick if you could measure yours up it would be a great help.

Just to correct your post X = A + 1/16"

I've measured the valve travel and its about 7/16" I think you lose a bit with the lifting link not keeping a straight line. if you could measure your valve travel that would be useful.

I think I may take the linkage out again tomorrow and measure it up and check if I can get any more travel there may be something catching.

The screw reverser is set fully forward with no more travel available on the lifting link.

Thanks a Lot

Stew

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