5"g Simplex steam loco build (hopefully)

Very nice looking reverse set-up Bazmak. Looks a fair bit larger than the one I just did.---Brian

Thanks Brian,hats off to Stephenson to think it up.Now its all linked up i can
see how it all works.Just the right size for my eyes and sense of touch
anything smaller i would have struggled with. Good progress with only 3 months almost behind me,i am amazed at the progress i have made
Retired with a mill and DRO sure does make a diiference

Yes Bazmak--People always go nuts about how quickly I do my projects. Well, yes---If you don't have to get up and go to work somewhere every day, you can accomplish a great deal in a short time.

bazmak said:

Thanks Brian,hats off to Stephenson to think it up.

Click to expand...

Bazmak, I think this reversing system was invented by Mr, Walschaert. The Stephenson system uses two eccentrics, one for forward and the other for reverse with a slide block link between the two. The Walschaert system uses the expansion link and radius rod to set the slide valve.

Perhaps you meant something else.

In any case, yes, you are really moving along! Good work, you will be running on air in no time at all. I think all you need is a way to get air into both steam chests at the same time. It took me 9 months to get running on air, but, I am not retired.

David

Thanks David,just showing the extend of my ignorance.I am struggling at the moment to understand how to set the slide valves.I am waiting for some taper pins to arrive to pin any parts that require removal at times.I have pinned
the reversing arm to the weighshaft with a roll pin.The arm is vertical with the
reverser at midpoint.Can i now taper pin the the lifting arm at 90o and horizontal ? Can you ease me thru the valve setting and what i should and should not be doing. Regards barry

bazmak said:

Thanks David,just showing the extend of my ignorance.I am struggling at the moment to understand how to set the slide valves.I am waiting for some taper pins to arrive to pin any parts that require removal at times.I have pinned
the reversing arm to the weighshaft with a roll pin.The arm is vertical with the
reverser at midpoint.Can i now taper pin the the lifting arm at 90o and horizontal ? Can you ease me thru the valve setting and what i should and should not be doing. Regards barry

Click to expand...

Do a search for Keith Appleton. He has done a heap of videos that explain exactly what to do.
In a nutshell you need to adjust the slide valve so it uncovers the inlet ports equally at either end of the stroke, then adjust the linkage so it admits steam just before TDC of the piston.

Hi Bazmak,

I'm sure Mr. Walschaert won't mind, no problem!

Hmm...setting the valve gear by email. I will not be able to really do this via email, but, I can give you a few hints. It took me quite a while to get mine to where I was really satisfied. I ran the loco for months with the temporary eccentric rods as I fiddled with adjusting the valve gear.

The whole idea behind setting the valve gear, is to get 4 equal exhaust beats per revolution of the wheels. This is sort of the proof that things are set correctly. You want the valve to just start to crack open after the crank pin is at top dead center or bottom dead center. At least three things are adjustable and are all interactive.

1. position of the return crank on the crank pin. (mine is still not yet pinned, just clamped!)
2. length of the eccentric rod. This length is apt to be slightly different on each side.
3. position of the slide valve on the valve spindle

As you adjust these things, you must keep checking to see how far the valve is moving in forward and then reverse. You want the slide valve to move the same amount over the cylinder ports when in forward and reverse. This is hard to achieve, but, you can get very close. Every time I made more adjustments to my valve gear, it got better. It sounded better and ran smoother. Currently, it runs just a little better forward than reverse. If you must compromise, going forward is usually more important than reverse.

This is by no means the full treatment to setting the valve gear, this is only to get your mind set to do the job. If you have set a slide valve on a steam engine that only runs in one direction, that is easy. Locomotive valve gear, not so much!

As for the lifting arm and weigh shaft arm, when the reversing screw is in the center of it's travel, the radius rod should be in the center of the expansion link and the lifting arm should be centered on the radius rod. The weight shaft arm should be about 90 degrees from the lifting arm. This will give the weight shaft arm about the same travel forward and aft as it pivots on the weigh shaft.

Ultimately, the reverser screw will provide a little more travel than you really need. You will eventually need to limit the travel of the nut block by putting a sleeve on the screw at each end to stop the block from going all the way to each the end of the screw.

The attached photo shows the lifting arm and weigh shaft arm. You can see they are about 90 degrees to each other. The radius rod happens to be all the way at the bottom of the expansion link. This is an old photo, I don't yet have the temporary eccentric rods installed.

Traditionally, the radius rod will be towards the bottom of the expansion link going forward, and at the top for going reverse.

As I am typing I see someone has suggested Keith Appleton. Yes, his videos are very good and will probably help much more than I. Be careful about having the slide valve let steam into the cylinder before top dead center. If you try to start the locomotive from a dead stop in this position, it will try to go in the wrong direction.

Having a problem posting the photo. Will try later.

David

I've mentioned my old friend before but Don L Ashton has written and published extensively and has a web site.

Of course, Don is also a world authority on things like tugboats and full size steam locomotives .

Don writes from time to time on Model Engineering Clearing House forum.

Also is an accomplished musician and composed and arranged saxophone music.

Great man and will go out of his way to help.

N

goldstar31 said:

I've mentioned my old friend before but Don L Ashton has written and published extensively and has a web site.

Of course, Don is also a world authority on things like tugboats and full size steam locomotives .

Don writes from time to time on Model Engineering Clearing House forum.

Also is an accomplished musician and composed and arranged saxophone music.

Great man and will go out of his way to help.

N

Click to expand...

If you google Don L Ashton all you get is rubbish about Mormons

Try this URL Lads...
http://www.donashton.co.uk/html/profile.html
Dai.

Thank you all,i have printed out Davids post and also Don Ashtons input
will give some heavy reading.Will pin it up up in the shed and use as the bible
for trying to sort out the timing.Will post as i go so any comments /advice will be most welcome. Although i would class myself as a moderate model engineer
i am a complete newbie to this,so bear with me. Regards barry

Here's the photo I was trying to post earlier. It may, or may not, be helpful at this point.
David

Thanks David,it does help.I spent a few hours playing about trying to get
my head around everything.Your advise and the photo help to give me a starting point.I need to be confident that things are near before i start to fine tune.Tell me what determines the full F and R of the screw adjuster. I checked the valve travel which is about 1/2" in F and R and about 1/4" in the middle
My head started to spin after a while and i had a couple of stripdowns and rebuilds.Had a problem with 1 or 2 conns binding.It gave me a lot of problems
until i found them and rectified.Then to take a break i started on the smokebox saddle,the GM casting had arrived. Nothing like the drawing but i can make it fit Ok. The SBox dia is 5" and i will machine in the mill with a boring headHeilan lassie i did in the lathe with a inline boring bar.Not having studied the drgs fully yet i dont know if i am building a Simplex or a super Will post my progress or lack in the next few days

Initial setting is in mid-gear, ie, when the die block is positioned in line with the expansion link pivots so that radius rod does not move when you turn the engine over. In this position, set the valves for equal port opening at each end.

That is your basic position. You can tweak it a little bit by ear, on air and later under load on steam, to give whatever best compromise of running at different cut-offs and in forward and reverse that you like.

All the discussion we had recently about timing Stephenson's valve gear does not
apply to Walschearts, the designer did it for you already.

Hi Barry,

All the suggestions give so far are good. I think you mentioned you have the Simplex construction book. The book says full gear travel is 9/16". or .562". This is the maximum needed movement of the slide valve. The same goes for the Super Simplex. The full movement of the reverser may give you more than the 9/6", but, don't let the radius rod sit hard in the bottom or top of the expansion link. The Super simplex says there should be .020" of lead on the slide valve. But, I have minimized this on my loco to nearly zero. Lead is good on a full size loco, but, is not necessary on a miniature and can make starting from a dead stop sometimes difficult. My loco starts easily with the wheels in any position and once going, it notches up quite nicely.

To get full valve movement, I had to spend a bit of time with Swiss files on the radius rod and expansion link making adjustments to get enough clearance to ensure nothing would bind with the link and radius rod in any position. The die block must be able to get to the extreme ends of the link and not bind. The link, as it swings must not bump or bind in the radius rod. Also. while turning the wheels to witness everything, the axle blocks should be in the normal running position in the horn blocks. On the Simplex, you should shim the axle blocks up 3/32". Put the shim, or spacer, between the axle block and the hornstays. Of course the loco must be lifted up on blocks while turning the wheels gently by hand. Be sensitive to binding or tight spots anywhere.

As for the timing of the slide valves, they should start to uncover the admission port just after the crank pin has reached top dead center, or, exactly at top dead center. If opens before, this pre-admission of steam, will introduce lead. In a small locomotive, it is not necessary and can even be detrimental as described by Don Ashton. Others may disagree and you can do what you feel works best for you.

You will discover that the position of the return crank and the length of the eccentric rod are inter active. This can be very frustrating, but, with enough experimenting, you will see what effects what and in which direction. A good setting in forward, will usually disturb the setting in reverse. You will probably have to compromise a bit. As you get closer to good reverse and forward setting, the Simplex gear can be set so it is almost perfect.

David

Bazmak--welcome to my world. Now you can see why a week ago I was running round in circles and biting myself. Timing these reversing set-ups ain't for sissies.--Brian

coming from a person like yourself with far more experience of valve timing
to an old fart like me with no experience then i must concure.
They say that the human brain has a finite capacity for knowledge and when filled like a bucket of water overflows as you keep learning.It is dangerous
to try and learn too much when you get older.You learn something new and forget something you once knew.One day i will forget where i live.
I am receiving lots of good input and sifting thru it to try and pick out what i need.In the meantime to give my head a rest i machined and fitted the
smokebox saddle casting which has just arrived

Baz--Very nice work. As far as there being an age related limit to learning new stuff, I'm not sure I agree with that. I still learn new stuff every week. In ways I believe that learning new stuff enables you to learn more new stuff. Keep in mind, I only started machining as a hobby about seven years ago. Prior to that, the last time I ran a lathe or a mill was in the mid 1960's during my apprenticeship, and then only for a very brief period of time on one of my "shop rotations". My mother is 97 years old, and I can see that she is beginning to slow down a bit. However I think that is because she is in an "old folks home" where she is cared for totally and isn't required to do a lot of creative thinking.

Made a start on the timing.Of the info that i have received i downloaded\Don Ashtons write up on Walschaerts Gear. It is very interesting read unfortunately
my bucket is full so i will only keep it as reference.
David (builder 01) is being very helpful with lots of info and photos to help
me get to grips with everything,and the information will be invaluable when fine tuning the timing running under air or steam.Meanwhile my initial thoughts were
to just simply try and set everything near enough initial just for checking hand turnover.In my mind i thought to start with the screw adjuster in mid gear,set everything near enough and centralise the slide valve then repeat for forward and reverse. Glad to get the advise from Charles Lamont which i think is confirming my thoughts.Thank you Charles,that is the way i am heading
with a series of photos as i proceed.Anybody please stop me if i am going wrong

Hi Brian,i wasnt saying that age is detrimental to learning,only that when the bucket gets full at our age,when we learn something new then we have to forget something to make room. Learning something new like valve timing
and we may forget some thing important,like where we live.Its ok for the young uns like Charles and Dave.their buckets are not full yet