How to start Walschaerts Design as a beginner?

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Dor_Crank
Posts: 48
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Location: LA, CA

Re: How to start Walschaerts Design as a beginner?

Post by Dor_Crank » Thu Dec 04, 2014 12:26 am

Thanks for answering Steve and Jos.

As Jos wrote, the identification of those parameters I've listed disappears under the parameter display table.
So, I don't understand what those parameters represent geometrically. For those people using other than Window 7
or Vista, please hit that little square button on the left of my listed unknown parameter at the simulation and tell me
how I measure their values.

Dorian

JJG Koopmans
Posts: 335
Joined: Thu Oct 01, 2009 10:01 am
Location: Netherlands

Re: How to start Walschaerts Design as a beginner?

Post by JJG Koopmans » Thu Dec 04, 2014 6:48 am

I tried again. I did not enlarge to full screen. Then setup>set large icons,(to get the table in place)
EditDim>set graphic zoom, I changed the 7.5 to 15.
After this clicking the left buttons showed the parts. However, those with value 0.0 do not show!!!
Change 0.0 to anything reasonable and the part will show.
Kind regards
Jos Koopmans

Dor_Crank
Posts: 48
Joined: Tue Sep 10, 2013 1:08 pm
Location: LA, CA

Re: How to start Walschaerts Design as a beginner?

Post by Dor_Crank » Fri Dec 05, 2014 9:49 pm

JJG Koopmans wrote:I tried again. I did not enlarge to full screen. Then setup>set large icons,(to get the table in place)
EditDim>set graphic zoom, I changed the 7.5 to 15.
After this clicking the left buttons showed the parts. However, those with value 0.0 do not show!!!
Change 0.0 to anything reasonable and the part will show.
Kind regards
Jos Koopmans
Hi Jos,

OK. Now I know how to set the model's scale. But the scale is represented by the track gauge.
The default ga. = 7.5 inch or 1 1/2" = 1ft. In my case, it's 1/32th scale running on 45mm track or
1 3/4" ga track so I need to set the setGraphicZoom = 1.75. If it's for my 1/19th British 2ft ga
loco on correct 32mm ga. track, I need to calculate/think a bit. Some of the 1/19th (aka 16mm/ft or
SM32) can run on either 32 or 45mm track since the wheels are re-gaugable (outside framed).
This is kind of poor way to indicate the scale of a model for our simulation software*. It should be
based on the scale of the model itself, not the track gauge where in many instances, the scale to track
gauge is incorrect. Eg, 2 rail 0-scale for a mainline loco (runs on the world standard gauge of 4ft 8.5 inch)
is 1/48th scale but our American mode runs on a Russian ga. of 5ft (1 1/4" ga, aka 0-ga) unless you're
a Proto:48 0-scaler, which is 1/48th scaled body running on a slightly less 1.177 ga (exactly scaled
1/48 track of 4ft 8.5 inch). Ok, enough diversion.

*But the immense usefulness and ease of use of this software I'm discovering is noted.

Thanks for showing me the basic display keys, viz., SetLargeFonts/SetSmallFonts, setGraphicZoom, and
change the parameter values, make them bigger or smaller, especially if the default value is 0. We can also
set a value to negative or positive to see how the parameter is indicated. E.g., for the Combination
Lever Backset, I've changed the default of 0 to -0.5 and the upper portion of the lever bent forward
where as +0.5 bent it backward. Actually, it won't allow you to place the + sign so you need to enter
0.5. Unfortunately, when you set it to SetLargeFont, the parameter table gets offset so you bette
count the position of the parameter name you desire and to match it with the little button to push.
The font size under the 'SetUp' flip flops between the SetLargeFont and SetSmallFont.
But I still can't see the ComboLeverBackset since the entire graphic shifts to the left and 1/2 of it
disappears. However, you can left click the mouse on the screen to bring back the entire graphic
and see that the combo lever's top portion indeed bends backwards.

So I know all the parameters are graphically except the Reverse Arm to Center Norm and Reverse Arm to Center Max. Regardless of changing these values, the indicator doesn't help. So, if you or anyone know
what these are, please let me know. Clicking the little button in front of any of these values just either
shrinks the horizontal bar. I am guessing that the Arm to Center Norm means. E.g., set Norm = .2 and
set Max = 10. Get a very short horizontal line for Norm and get long horizontal line for Max. I wonder if
the Norm means minimum travel for the Reverse Arm (viz., a notch on the Cab Reverse Handle's sector)
and the Max means full Cab Reverse Handle movement from the rearmost notch to the forward most notch?
That maybe the reason these horizontal line segment indicators always center on the vertical step of the
reversing L-arm?

Dorian

JJG Koopmans
Posts: 335
Joined: Thu Oct 01, 2009 10:01 am
Location: Netherlands

Re: How to start Walschaerts Design as a beginner?

Post by JJG Koopmans » Sat Dec 06, 2014 6:11 am

Reverse Arm to Center Norm and Reverse Arm to Center Max.
This sets the movement of the arm and in the ends defines the swing within the link,
try switching to 1.8 and 2.
Kind regards
Jos Koopmans

Dor_Crank
Posts: 48
Joined: Tue Sep 10, 2013 1:08 pm
Location: LA, CA

Re: How to start Walschaerts Design as a beginner?

Post by Dor_Crank » Sat Dec 06, 2014 3:24 pm

Jos,

Thank you for your further suggestion. I gotten a little more understanding with it
against the Reverse parameter pair, ReversArm to Central Norm and ReverseArm to
Central Max. Yet, I still can't assign values to these parameters for my actual physical
Walschaerts (outside admission) valve scratch building for my 16mm/ft scale (1/19th
scale) 2ft gauge British live steam model.

Without changing the setGraphicZoom, I sat the Reverse Arm parameters to 1.8 and 2.
When I inquired to indicate these parameters, it just showed the horizontal line again,
one just shorter than the other. These indications still won't tell me what these para-
meters represent.

But, I did try setting the Die Block position to Fwd from the defaulted Cen with those parameter settings.
In the Run mode, the die block went downward further than the default settings of .800, 1.00 pair, and
the motion displayed ok.

But when I sat the die block to Rev, the die block jumped out of the Expansion Link's slot, high above and made
beep sounds. So, as you've suggested that ultimately, these parameter pair determines the die block swing within
the link was verified. Yet, physically, when I need to make these Reverse motion linkages, I won't know what/where
these parameters represent. And, even if I made the L-arm (boomerang) part, I won't know how to assign
numbers to these parameters for the simulation. The only thing I know is that these parameters allow me to offset the
die block swings from the cen(tral) position asymmetrically and must not be too big to jump out of the Expansion Link's
slot. At least, I can make temporary boomerangs and observe the die slot swings for actual physical trials(not simulation).
That would defeat the purpose of the software.

On my gauge 1 model, after several valve gear adjustments, I did want to have one more notch on the sector for the cab
reverse handle bar whereas for the forward gear, it was OK as is.

With so many of the audience here who've used the Dockstader's program, I can't understand the users had no
problem understanding these parameter pair.

Dorian

JJG Koopmans
Posts: 335
Joined: Thu Oct 01, 2009 10:01 am
Location: Netherlands

Re: How to start Walschaerts Design as a beginner?

Post by JJG Koopmans » Sat Dec 06, 2014 4:49 pm

Hi,
I suggested 1.8 and 2 to show the effect of the change, it was not meant to represent a physical value.
As for these values, the location of the die withing the link defines the stroke of the valve. Just try
changing the .8 value, let the simulation run and see what happens with the valve stroke.
With the largest stroke the port should be fully opened.
So far I am not aware of you using the inside or outside version, could you let us know?
Kind regards
Jos Koopmans

Dor_Crank
Posts: 48
Joined: Tue Sep 10, 2013 1:08 pm
Location: LA, CA

Re: How to start Walschaerts Design as a beginner?

Post by Dor_Crank » Sun Dec 07, 2014 5:20 pm

Jos,

I'm using the outside admission version, Wals_out. I don't know how true it is but I've read for a small scale of
1/32, it is hard to machine prototypical piston valves that are tight and workable.

Thank you for describing the die block to valve stroke relationship along the expansion link slot. But the
point is, without physically knowing how to measure these two parameters, it won't help me at all. Perhaps,
whatever these parameters represent, i think it'll be more useful if they are replaced by say, the arm lengths
of the L-bar? We could have equal length for the L-arms or not. Even the angles of the arms can be
changed, other than 90 degrees?

Dorian

Dor_Crank
Posts: 48
Joined: Tue Sep 10, 2013 1:08 pm
Location: LA, CA

Re: How to start Walschaerts Design as a beginner?

Post by Dor_Crank » Tue Dec 09, 2014 12:17 pm

Looks like it's an end of the street on these parameter interpretation. Just need to figure the geometry
and then to apply algebra on it to calculate the Reverse Arm Dimensions (L or Boomerang piece) to
physically make this Arm pair. But still won't know how to translate the calculated dimensions onto
the Dockstader's software. So, feed his simulation with my model drawing's valve parameter values
except fake the Reverse Arm to Center Norm and Reverse Arm to Center Max values somehow to
use his simulation to advantage. Or, forget the simulator software and just play with thin sheet metal
cut outs of the valve gears (adjustable parts where possible) till the valve motion to open the ports
are symmetrical for forward and reverse, then make the 'real' pieces - This method sure defeats the
convenience of the simulator let alone, to measure thermal parameters or fine tune for optimum steam usage.

I've looked ahead for the cylinder dimensions in his simulation and luckily, there is no parameter
that needs to be clarified. They're all explicit! Still, it's hard to accept no one else had problem
to interpret these Docstader's Reverse Arm parameters.

Thanks Jos and others for your support to carry me this far.

Dorian

JJG Koopmans
Posts: 335
Joined: Thu Oct 01, 2009 10:01 am
Location: Netherlands

Re: How to start Walschaerts Design as a beginner?

Post by JJG Koopmans » Wed Dec 10, 2014 7:29 am

Why don't you just play with the .8 figure, by systematically diminishing it?
Kind regards
Jos Koopmans

Dor_Crank
Posts: 48
Joined: Tue Sep 10, 2013 1:08 pm
Location: LA, CA

Re: How to start Walschaerts Design as a beginner?

Post by Dor_Crank » Wed Dec 10, 2014 10:04 pm

JJG Koopmans wrote:Why don't you just play with the .8 figure, by systematically diminishing it?
Kind regards
Jos Koopmans
Yes, I've diminished the ReverseArm to CentNorm parameter from .8 in increments of .2 to 0.
The distance of the die block within the expansion link slot got closer and closer to the center of
the link slot. When the value reached 0, setting the Rev/Cent/Fwd button to either Rev (reverse)
or Fwd kept the die block on the center and the wheel rotation direction stays counter clockwise.
I.e., the reverse arm cannot change the loco's direction to reverse when the CentNorm = 0.
This experiment was done with the ReverseArm to Max parameter being held constant at 1.000. Increasing
the latter from 1 to 4 didn't change any behavior of the die motion. But setting it to 0 would not stay. The Max parameter value changes to .400 automatically. n Actually, setting the Max par. to .2 cannot be done
either. It automatically get set to .400. This looks like a software bug.

So, I guess the ReverseArm to CentNorm parameter reflects die path within the slot away from the center
of the link slot below and above it. I won't know what the ReverseArm to Max stands for.

I guess the boomerang arm dimensions just need to be made to satisfy this top and bottom die travel
amount. The die's offset from the central position must be figured from the valve's travel requirement to
cover and uncover the steam ports correctly. I still don't know what is this ReverseArm to Max parameter
is. Did I get the ReverseArm to CentNorm being the die block offset amount from the Link slot center right?

Dorian

JJG Koopmans
Posts: 335
Joined: Thu Oct 01, 2009 10:01 am
Location: Netherlands

Re: How to start Walschaerts Design as a beginner?

Post by JJG Koopmans » Fri Dec 12, 2014 6:14 am

Hi,
If you look at a real slotted link, it is closed at the top and bottom. The value of reverse arm max. is meant to prevent surpassing the end of the link. I hope you do realize how this works, the eccentric on the wheel gives the link a fixed rotation and depending of the location of the die in the link this rotation is transferred in a controllable linear motion of the valve. So if you do not see proper motion of the valve, the error might be somewhere else.
Kind regards
Jos Koopmans

Dor_Crank
Posts: 48
Joined: Tue Sep 10, 2013 1:08 pm
Location: LA, CA

Re: How to start Walschaerts Design as a beginner?

Post by Dor_Crank » Tue Dec 16, 2014 8:52 am

Thank you Jos for the valve linear motion generation. Yes, I remember when I set
those Arm parameters very high, the simulation alarm (beep) comes on and the
die shoots out of the link slot. I'll just accept that these two parameters:

ReverseArm to CenNorm and
ReverseArm to Max

was ill illustrated parameters by the simulator author and forget exactly what
he meant to show. By looking at the default parameter values of .8 and 1 respectively,
.8 cannot be the cab Reverse Handle's notch distance value. It's too big if you try to
accept the ReverseArm Max to be the full swing value of the die within the Link's
slot. Since .8 and 1.0 is very close, Mr. Docstader is trying to say the die can swing
.8 away from the center of the link for the top portion of the link slot but 1.0 for the
bottom portion (or vise versa).

This asymmetric swing is actually handy because I had experienced recently that
on a Ga. 1 model, the reverse runs poorly since the ports do not open fully in that
direction vs. the forward direction. There are too much slack in the valve gear
connections. Why I can push the valve with my finger after the cab handle was
set in either direction.

I just wished that I had one more notch for the reverse on the cab handle's sector.
It was just too fiddly to optimize (adjust the Reverse arm, return crank, valve stem
length, etc) the valve opening for both forward and reverse for the symmetrical front
and rear valve ports!!!

When I think about the Link slot, I really don't need to concern about whatever
these parameters meant. Because I would already determined the radius rod length,
which in turn defines the radius of the Expansion Link. That radius is all I need to design
this component. The die travel within the slot can be derived from the valve's linear motion
itself to cover and uncover the front and rear ports correctly. The port separations and
width was pre-determined already by selecting the cutoff amount and the piston travel
you've wanted for the cylinders. All we then need to do is to cut out the Reverse Arms
(the L-shaped boomerang), Reach Rod, and the Cab Reverse Handle stand with notch
sector to obey this valve motion. If desired, we can plug all of the dimensions to the
simulation and see what Mr. Dockstader meant by these two parameters.

It's still hard for me to accept, knowing his simulation was, I guess, used by many people
and they didn't encounter with the interpretation of these parameters. That is my 2nd
mystery. I'll just go on with making the valve gear.

I'll then be more interested perhaps on interpretation of the simulation result.

Thank you again for your support,

Dorian

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