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Simplex

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Barneydog:
Hi Guys,

Looks like my entire Simplex topic got lost in the recent migration because I probably started it after the 10th.
So to recap.....I have bought a part built Simplex. Frame is completely built. Cylinders are complete though not fitted. Motion work and valve gear was almost complete and fitted. I have now made the last of the Walcherts rods and am trying to do a basic setup to check everything is ok.
Everything looks good.....EXCEPT.... the slide valve. They are the correct size according to the plans but I believe the plan size is too wide. My valve ports are roughly 4mm wide on the input, 10mm wide on the exhaust with 4mm land between them. From one end to the other there is almost 1mm of one port uncovered and none of the other. If I mess about adjusting it further I would have less that half a mm each side. Martin Evans article does not explain the valve setup very well so the question is:-
How much of the ports should be visible at each end of the valve travel? My guess is that the whole of the relevant port should be uncovered otherwise what is the point of it being that width? I have removed one valve and replaced it with clear plastic so I can see the ports as I move the wheels. I have some markings showing a centre gap the width of the exhaust port, one inlet port and one dividing land giving a gap of about 18mm. This represents the hollow in the base of the slider to exhaust each port in turn. I have then marked each side at 4mm to give land to seal down to the cylinder valve face but leave a port fully open at each extent of valve travel. Is this correct or am i missing something?

Thanks

Julian

Jo:

--- Quote from: Barneydog on January 21, 2017, 03:23:29 PM ---Martin Evans article does not explain the valve setup very well so the question is:-
How much of the ports should be visible at each end of the valve travel? My guess is that the whole of the relevant port should be uncovered otherwise what is the point of it being that width?
--- End quote ---

How much is uncovered depends on how far it is "notched back". You should look to set the valve so that the travel/amount uncovered is equal at either end.

Jo

Barneydog:
Thanks Jo,
I understand it needs to be equal but how much should be uncovered? It needs some lead but 1mm sounds about right not nearly 4mm which leaves the port's virtually blocked.


Julian

Barneydog:
Hi guys,
It's been a few weeks but had a beer moment............My simplex runs on air. It's slightly uneven because it has plenty of air leaks as roughly fitted together but it runs. I just wanted it to run so i can strip it back down and clean everything up. All rods,pins and linkages are now off and being cleaned, fettled and nickel plated. Axles have been dropped out the frames to be cleaned and painted. Frame is having the remaining balance bolts swapped for stainless metric ones and then frames
will be sprayed. Going to fit brakes as everything is refitted then it's boiler time!!

Video posted below. It's a bit jumpy to start with but improves....Photo bucket issue. Ignore the compressor in the background and you can hear the simplex.

sbwhart:
Well done Julian

That looks OK to me.

Stew

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