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Post by pkastagehand on Feb 24, 2008 15:47:00 GMT -5
I'm working on the tender for the A3 in 3/4" scale. I notice that the text for the the top and bottom "horseshoe" members says to use 5/16" square brass stock. The drawing for same is clearly labeled as 1/4" square stock. Which is it? Does it matter?
Paul
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Post by efbernardc on Mar 1, 2008 21:53:49 GMT -5
I don't think it matters. I used 1/4 inch material. I also added 1/4 inch material along the straight runs where the tank skins attached to the horseshoe to make skin attachment easier. Also, it really helps bending to anneal the brass in the corners.
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Post by efbernardc on Mar 1, 2008 21:59:23 GMT -5
When making retainers for O-rings, such as for the two water pumps and steam chests it is helpful to make a recessed land for the set screw. I recess the set screw land by .020 inches using the lathe while turning the part. This makes it easier to remove the retainer after tightening the set screw as any material shifted by the set screw is in the land and not at the loose fit surface.
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Post by efbernardc on Mar 1, 2008 22:10:02 GMT -5
Just finished the couplers, Section 35, page 195 and 196. I found that doing the second step in figure 35-5 first made it easier to do what is shown as the first step. Also I found that 24 degrees worked better than 23, but that may be due to inaccuracies in my protractor. It is also easier to machine the 3/64 inch top recess prior to doing the 23 degree angle machining.
Figure 35-3 shows the center for the 3mm hole to be on the same left to right line as for the 1-64 tapped hole - .051 inch from the vertical reference line (which is .192 inch from the right edge of part). A close inspection of figure 35-2 "Contour" shows that the 3mm hole should be located .045 inch to the left of the vertical reference line. I take a 3mm hole to be .059 radius.
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Post by pkastagehand on Jul 17, 2008 14:01:31 GMT -5
A3 in 3/4" scale: Trivial and probably just a typo, but the drawings show the frame material as being 1-1/4" x 1/4" but the text in paragraph 10.1 says 1-1/2" x 1/4". I suppose one could start with 1.5" stock and machine to 1.25" but it doesn't appear to be necessary and may cause additional warping issues. (that is to say: the extra work of starting with 1.5" isn't necessary. I see the need for it to be 1-1/4". )
You folks already past this point must have discovered this already and obviously just worked it out your own ways.
Paul
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Post by siggy on Jul 17, 2008 16:22:42 GMT -5
If you use the 1.5 inch material and don't machine down to 1.25" you'll need to be real careful because you have things mounted to both the top and bottom of the frame rails that will need adjustment to get alignment back. Things like the tie plate, condensation drain linkages, oil pump, ash pan catch, etc.
Robert
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Post by pkastagehand on Jul 18, 2008 9:21:59 GMT -5
yeah, I wasn't implying not machining it. I meant starting with 1.5" to get to 1.25" is not worth the waste of time and material, so one should probably just start with 1.25" material. I often don't speak (or write) what I really mean. But it was clear in my own head! Paul If you use the 1.5 inch material and don't machine down to 1.25" you'll need to be real careful because you have things mounted to both the top and bottom of the frame rails that will need adjustment to get alignment back. Things like the tie plate, condensation drain linkages, oil pump, ash pan catch, etc. Robert
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Post by peterl78940 on Jan 1, 2009 14:35:46 GMT -5
minor typo on page 168, part number 7 "LINK", the width of the slot on the left end of the link is dimensioned .785, but should be .0785.
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Post by GregMiller on Nov 26, 2009 13:32:23 GMT -5
Hello All, I am modeling the A3 as I go in Alibre. For me, it helps me think about how I will machine the parts as I draw them. In the below assembly of the Guide Yolk and the Link Brackets, there is a slight overlap. I have checked my dimensions of the Guide Yolk and brackets and they seem to be fine. Did anyone else have this overlap during construction. I realize that it is pretty slight, but if it is an indication that I may have the part modeled wrong, I'd like to address it now before I cut metal. Thanks, Greg
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Post by siggy on Nov 26, 2009 21:34:37 GMT -5
Hello All, I am modeling the A3 as I go in Alibre. For me, it helps me think about how I will machine the parts as I draw them. In the below assembly of the Guide Yolk and the Link Brackets, there is a slight overlap. I have checked my dimensions of the Guide Yolk and brackets and they seem to be fine. Did anyone else have this overlap during construction. I realize that it is pretty slight, but if it is an indication that I may have the part modeled wrong, I'd like to address it now before I cut metal. Thanks, Greg Yes - your drawing is correct. However, in practice, you will never see this very slight "overlap" in the finished engine - there is just no way to see down in there with all of the other linkages, etc in the way. I also found this via a CAD model before building but I built it per plan anyway. I just spent 10 minutes looking at my engine and the only way I could visually confirm this was with a dental mirror. You could always take a slight shaving off of the inside guide block but why waste your time worrying about it? Robert
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Post by GregMiller on Nov 27, 2009 8:58:52 GMT -5
Siggy,
Thanks for the reply and taking time to look at your engine. I'll likely take your suggestion and just shave off the inside bracket.
Thanks, Greg
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Post by pkastagehand on Nov 27, 2009 17:38:38 GMT -5
Thanks for the heads up! I'm working on valve rods, etc. in this area. Those link brackets are the next thing. Just about finished with the expansion link parts.
Paul
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Post by dickr on Jan 30, 2010 14:52:40 GMT -5
Mistakes, errata and changes in a Mr. Hiraoka book Really, my goodness. Well nobody's perfect ! Too bad a set of prints in 3/4" or 1 1/2" full scale prints aren't available. No I don't wanna do it, I'd rather save up and pay for them. Naturally at a real cheap price. It'll be fun to see all the different interpretations of this little note. The last time was really interesting. Dickr (Only the good die young)
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Post by dickr on May 5, 2010 19:12:42 GMT -5
Has anybody discovered the correct dimension for the 2 pin holes on the front of the ash pan (Pg 130) It shows 3 dimensions : 3/4" from the bottom, 5/32" from the 45*, and 1/4" from the front end. I believe that is impossible. I just moved it so it would fit. Although that's not following directions. Oh dear !!!
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Post by grege on May 6, 2010 10:51:09 GMT -5
Hi Dick, I'm getting close to that part myself. I read it that the 5/32" dimension is the distance to the 45 angle from the centerline of the hole. As the 45 angle milled section of the grate support is 3/16" from the hole, that gives 1/32" clearance.
Greg
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