A3 3/4" Tee clearance on Side Frames

[phutcheson]

I was about to drill the mounting holes on the cylinders when I noticed that the Tee would not be centered in the provided cut out. I read a past post about this back in 2006 but solution was not complete.

It appears that when using the finished dimensions for the Cylinders they are too high about .015". So that the Tee may not fit into the cut out in Side Frames. In addition, the top of the Cylinder and the Side Frame top are not on the same plane. The drawings in several places show several centerlines indicating that they should be.

I'm not using the drill jig, I understand it if I was ... I would not have this issue.


Since my mounting holes for the cylinders and cut out for the Tee are already drilled/machined I think I will just move the 4 mounting holes on the Cylinders the .015" needed for centering. This will also keep the center of the piston in line with the rest of the drive assembly.


So what did you guys do about this issue??


Thanks

Pat H.

[pkastagehand]

I didn't realize there was an issue. I haven't yet fully assembled all the parts. Just made them according to drawing. If there is an error I built it right in I guess!

I may get a surprise later!

Paul

[GregMiller]

Hey Pat,

I have not modeled the cylinders yet in Alibre, but I do have the frame and the drilling jig complete, and there was no issue between those parts.

If you can be a little patient, I can try and model a portion of the cylinder tonight per-the-print and let you know how that fits together.

Greg

[phutcheson]

Thanks guys for the quick response....


Paul

You may not have an issue if you used the drilling jig for the Side Frames and the Cylinders. Have you built the Tee yet? If so you can easily test it out.

Greg

This should be interesting ... I found the issue only after I modeled
the three parts in Solidworks using only the dimensions provided.

I'm really in no hurry as I have a lot of other things to do. One of which will be modeling the Guide Yoke, the Guides with the Centerline of the cylinder. These should line up .... we will see.

Also I'm trying to figure out how to draw the steam passages ... somehow I must have to tilt plane at the correct angle, I guess.


Later

Pat H

[kenrinc]

Pat,

All I cared about was that the cylinders were square with the side frames and at the right height. The jig obviously does this for you. I drilled the tee using the given dimensions and the cylinder mounting holes and frame to cylinder mounting holes with the jig. Even so, my cylinders were tipped back by .006 or so. I just did my "fiddling" to make sure that the cylinders were square with the side frames and level.

My tee did not fit into the side frame cutouts at first. But I'm not sure if that was because of the mentioned dimension mismatch or my machining of the tee. I free handed the angles on the tee and found that I didn't take enough material off so that's why I figured they didn't fit. I was more concerned that the steam holes would line up and I believe they do.

Brings up another point in that the tee and cylinder bodies should actually be assembled and gasket compound applied as the last part of the frame build. If you wait and do it when Kozo's says you'll have to completely take apart the entire frame AGAIN so that you can seal it all up. I'm working in 1.5" scale so this is not a trivial issue. It may be insignificant in 3/4 scale.

Ken

[GregMiller]

Hi Pat,

I quickly modeled a portion of the right cylinder last night using the dimensions from the book. I assembled it to the frame with the 4 mounting holes and I had 0.0312 difference between the cylinder center line and the guide yolk center line. I did not have time to double check my model, so take this merely as a status update.

Greg

[pkastagehand]

I did make and use the jig. As Ken said if you don't put the parts in early it all has to come apart to get the tee in and I haven't done that yet. Remains to be seen. I didn't want anything "glued" together yet because I haven't done any painting of parts.

Paul

[kenrinc]

You guys got me scared now Dimensions say the piston CL is 7/8 down from top of frame and 2.5" over from CL of frame. It's easy to compute the stuff and then machine it but if it's already put together it's a bit more difficult. Your talking about the CL parallel to the frame correct? I know I can make up any differences when making up the other parts. I've just finished the guide yokes and have clamped and drilled them onto the tie plate. Getting ready to drill and tap the crosshead guides from the cylinder head boss to the yoke. Nothing looks out of the ordinary at this point. Let you know what I find .

Ken

[dickr]

Certainly couldn't be the drawings. As straight forward as they are. Bet you spend more time defining the drawings than making the parts. But then this book is for beginners.
Sorry but these drawings really leave a lot to assumption . Certainly keeps me out of the kitchen though.
dickr

[GregMiller]

All,

The 0.0312 difference, that I reported earlier, between the cylinder center line and the guide yolk center line was incorrect. Using the dimensions from the book, my model shows a shift of only 1/64 = 0.0156 (Which I think matches your error, Pat)

I have confirmed that if one uses the drilling jig, as instructed, that all will be okay. Said another way, using the jig to locate and drill the holes in the frame as well as the cylinders should result in no alignment issues.

Here is a visual explanation:

The Tee is aligned to the frame with the aid of the drilling jig.


Drilling Jig removed to show Tee alignment with Frame


Cylinder aligned to frame with 4 mounting holes.


Using the Cylinder dimensions in the book, and aligning the drilling Jig with the top and side edges of the cylinder, a slight misalignment in the 4 corner mounting holes can be seen.


Alignment after changing the dim in Fig 14-3 of the far right drawing from 9/64 to 1/8 (8/64).


Cylinder & Frame alignment after 1/64 shift in cylinder dim.


Hope this helps,
Greg

[phutcheson]

Well I think we can put that issue to bed!
Thanks for all the inputs.

Greg ...

Isn't nice to have CAD system that shows such great detail. I know that it helps me a lot.

Thanks for the extra effort.

I have adjusted my Cylinder drawing to reflect the change in the location of the 4 mounting holes. For me that was the easiest way to correct the position of the Cylinder ... others may have a better solution.


Now back to the issue at hand ... making parts!


Pat H

[kenrinc]

OK so there is an issue and the holes are off. Which means that the guide yoke mounts for the guides must be adjusted to compensate IF you did it the way the book shows.

Ken-

[phutcheson]

Ken,

Yes you will need to change the yoke mounts, but it doesn't stop there.

Some of the linkage to the drivers may also need adjustment. Reverse Gear and Cylinder Cocks linkage will need to be changed to name a few of the obvious ones. I don't know if all that linkage can absorb that much error in the Cylinder height. Maybe it will or maybe just a little change here and there will work. I chose not to test those waters. Even if you plugged the Side Frame holes and re-drilled them that may be easier then trying to figure out the necessary linkage adjustments.

Keep at it and good luck ...


Pat H.

[kenrinc]

Thanks Pat. I seriously doubt any huge issues, as a friend of mine always says, "we ain't building watches here".... and considering how many of these have been built, without the help of CAD/Solid modeling, that only drives the point home.

Ken

[peterl78940]

page 65: the screw holes in the frame for mounting the cylinder are symmetrical and centered,
1-1/4 - 7/32 - 13/16 = 7/32.

page 83: fig 14-1: missing dimensions: height of cylinder center relative to frame, height of Tee
center (horizontal steam passages) relative to frame. you can make an educated guess
that the cylinder center is 7/8" down from the top of the frame, but that isn't marked
in the way it should be for that to be certain (the extension line would have to be much
closer to the front bumper to conclude that), the only thing that seems for sure to be 7/8"
is the height of the cylinder valve face relative to the cylinder center. the only height
dimension between parts we have for certain is 9/32 between cylinder center and Tee
"center".

page 84: fig 14-1: section E-E: the Tee "center" seems to be at 21/32 up from the bottom of
the frame (which is 1-1/4 high, or 40/32) so the Tee is 1/32 too high to be "centered"
within the frame. ---> It is asymmetric. <---


page 85: fig 14-3: far right: all the screw holes to the frame on the side of the cylinder are
symmetrical and centered w.r.t. the center of the (5/16 + 25/32 =) 35/32" width
of the mounting surface 35/32 - 9/64 - 13/16 = 9/64.

and the screw holes for the Tee are clearly symmetrical (+/- 15/64 and +/- 9/32),
but they are NOT centered, they are up 9/32 from the center of the cylinder (see
"section A-A") or 19/32 up (5/16 + 9/32) from the edge of the mounting surface.

19/32 up from something that is 35/32 high makes them 3/64 up from being
centered. ---> It is asymmetrical. <---




page 90: fig 14-29: all the screw holes in the Tee are perfectly symmetrical (+/- 9/32 and
+/- 15/64)
but are they centered ? NO !!!!!, see the dimension "11/32" for the height
of the horizontal cross way hole, this would have to be 13/32 to be centered.
it is off by 1/16". ---> It is asymmetrical. <---


If I am correct, we have so far identified three asymmetrical dimensions, one off by 1/32",
one off by 3/64", and one off by 1/16",

I could be wrong, but I am pretty sure such a collection of different error values cannot be
fixed by moving any one single part or by changing any one singe dimension...



In My Humble Opinion this is a design "process" error on Kozo's part.
Gratuitous asymmetry is a big no-no.

If you don't agree with me consider this: look at the 5/16" thickness of the horizontal part of
the Tee, is that 5/16"ths centered around the through holes (steam and exhaust passages)
or is it centered with respect to the 13/16 width of the cylinder mounting face of the far ends
of the Tee ?

There is no way to tell from these drawings, this dimension is missing.!.
(or so it seems to me, hope I'm not fooling myself...)




Page 98: fig 16-1: far lower left: presumably it is the distance from the top of the frame to
the center of the cylinder that is marked as 7/8", at least it is consistent with the 7/8"
noted in "page 83: section A-A", and in this case there doesn't seem to be anything
else that it could be.



OK you CAD'ers, is my analysis of the mismatched offsets from centers correct or am _I_ "offset" ?




what bothers me about this book, in addition to gratuitous asymmetries, and in addition to
gratuitous odd-ball dimensions (32'nds and 64ths of an inch, and #3 screws which almost
don't exist), in addition to the odd-ball dimensioning of locations relative to randomly chosen
other locations rather than to fixed defined reference locations, is that it lacks "xray" drawings,
drawings where parts are shown together and reference lines are defined that parts are measured
relative to. Look at the drawing on pages 2,3,4, it is absolutely beautiful, but it doesn't resolve a
single inconsistency that has come up here (nor elsewhere in the errata if I guess correctly). This
drawing's beauty is deceiving. The boiler is up 5" from the rails, but what about the frame, the
cylinder, the valve, the trunnion plate pivot, ..., ? there aren't all that many critical dimensions
between relative parts in a locomotive, but they are all hidden in this book.



I did my A3 using all my own drawings (because I did it in "F scale") using "xray" drawings first,
and then individual parts detailed second (avoiding all the "gratuitous" errors noted above), and
everything matches up. YMMV.


don't get me wrong, I love this book and I love this engine, its the best out there
and the only one I recommend to new builders, but there is still room for improvement.

Pete Lawrence.