|
Post by dickr on May 6, 2010 12:13:15 GMT -5
Thanx Greg I would agree with you. I would guess the 1/4" dim. is just ref. to the 3 19/32" dim. to the other hole???
|
|
|
Post by grege on May 6, 2010 15:41:18 GMT -5
The 3 19/32" dimension gets you the corresponding spacing of the pin hole in the grate support over to the latch, but it is noted to locate from your actual latch. The 1/4" from the front less the front panel thickness corresponds with clearance pivoting around the curved lower front corner of the grate support. Make sense?
|
|
|
Post by dickr on May 7, 2010 13:02:08 GMT -5
Yes I see what you mean. The 1/4" dim. in my book shows it coming from the front of the tray. Subtracting the .078 from the .25 makes the diff. Thanx again .
|
|
|
Post by kvom on Nov 23, 2010 8:16:08 GMT -5
Page 206: frame width should be 5.25", not 5-9/16
|
|
|
Post by phutcheson on Nov 23, 2010 13:42:00 GMT -5
kvom,
Although I'm not making my A3 in 1 1/2" scale I believe the dimension given on page 206 is correct as stated (5-9/16"). Note that it is repeated on page 207 (top left corner), page 208 (Section B-B), and page 227 (fig 7-1 left view, also note that the ash pan has a width of 5.25"); there may be other examples.
But the big one is .... on Page 205 paragraph 1 Kozo states that " ... , the main frame and the tender trucks must be wider than double those in 3/4" scale".
I guess building the tender also requires some adjustments, but he doesn't go into any details. Leaves it to the builder!
Hope this helps ...
Pat H.
|
|
|
Post by kenrinc on Nov 23, 2010 17:44:04 GMT -5
Pat is correct. Re-read note 1) on page 205. It's a common mistake to "assume" that you can double the frame dimensions when going from 3/4 to 1.5" scale, you don't. You are bound by track gauge.
56.5" in 1.5" scale is 7-1/16" Why we use 7.5" gauge is a long story that has been beaten to death. Were basically bound by history. The "gotchas" in the 1.5" scale section are further along especially in the valve gear area where he leaves no info. Guide yoke needs to be widened and such.
My frames are 5 - 9/16" wide.
Ken
|
|
|
Post by kvom on Nov 24, 2010 21:44:54 GMT -5
Given that 5-9/16" is correct, then the width of the Tee needs to be wider than double as well. In the 3/4 scale, the outside of the frame would be 3-1/8, and the width of the Tee is shown as 3-3/16. I assume the extra 1/16 is needed to adjust so that the Tee-cylinder assumbly mounts flush to the frame.
For the same allowance in 1.5 scale, the Tee would need to be 6-5/8 wide rather than 6-3/8. Also, the width of the tie plate (p 99) and the separation of its mounting "feet" need to be adjusted (as opposed to the guide yoke, which I assume can be doubled)
What else? Given th
|
|
|
Post by kvom on Dec 1, 2010 8:44:04 GMT -5
Not really an "errata", but the top-view drawing of the foot plate on p.206 is deceptive. The two holes for the support brackets on the right side are not drawn "properly" and appear further to the center than is correct. The holes shown on the left side are better, and both sets are supposed to be symmetric.
|
|
|
Post by kvom on Dec 8, 2010 15:32:16 GMT -5
On p. 227, fig 7-1, the side view of the supports shows the centerline of the grate slot as higher than the centerline of the tapped holes. However, the centerline of the slot is 7/32+17/64 = .484, while the centerline of the tapped holes is .500 from the bottom of the support.
|
|
|
Post by kvom on Dec 13, 2010 13:04:28 GMT -5
Having started to machine the driver castings for the 1.5 scale, I wanted to determine the thickness of the driver. If you double the 3/4 scale driver to 7/8", it will be too thick to fit the rods. The main reason for this is that the 1.5 scale axle box protrudes further from the outside of the side frame than does the bushing flange on the 3/4 scale.
For the 1.5 scale, the cylinder centerline is 1.875" outside the frame. Of this, the side rod needs .400, the main rod .200, the axle box .234, the spacer .15, and the bushing flange .08 (refer to drawing on p78). These total 1.064, leaving .811 for the wheel and any clearance between the wheel and the axle box. With the IBLS minimum wheel width spec at .750, the clearance would be .061".
The width of the wheel+clearance determines the length of the axles. Assuming an axle that's 8.625" and an outer frame width as per plan, there is 1.031 of axle beyond the frame. Subtract .234 for the axle box and you have .797. With a .750 wheel, there's .047 clearance from the frame, not far from the .061 max calculated above.
In summary, it seems that a 3/4" driver thickness and a 8-5/8" axle length results in a reasonable fit to the frame/cylinder dimensions with "wiggle room" for adjustment.
|
|
|
Post by kvom on Jan 20, 2011 16:55:52 GMT -5
In drawing the front coupler for the loco in 2x scale from 10-22 on p70, I discovered that the pocket will be 15/16 x 3/4. This is the same as the shank dimensions on the Tom Bee couplers, so to use these (and possibly others), the coupler shank would need to be machined to give some vertical clearance. The shank would need to be shortened and narrowed to allow the requisite swing from side to side.
I also wanted to verify that the coupler height would be correct. Using the axle centerline height shown on p207 and the nominal driver tread diameter shown on p211, the top of the frame would be 4.9375" above the track. The centerline of the coupler pocket is .5625 below the frame top, giving the coupler centerline as 4.375 above the track. Since the 7.5 standard is 4.38, it seems that the plans are in accordance with the standards.
So if the drivers are significantly larger or smaller than 6.375 tread diameter, the coupler pocket location would need to be adjusted up or down. I was interested in this at this time as I plan to have my rolling frame towed around our track once it's to that stage of completion. So I'll need a coupler on the front bumper.
|
|
|
Post by kenrinc on Jan 21, 2011 22:15:58 GMT -5
Kozo fabricates his own coupler so I would expect no commercial coupler to fit. Your on your own there. And I would expect most to do whatever they want. I don't feel it should be mentioned here as there is no error.
The driver tread is 6.5" in diameter, not 6.375. The driver diameter shown on pg 211 is incorrect as was pointed out earlier in this thread. Given that, the frame top should be 5" from railhead.
Ken-
|
|
|
Post by kvom on Jan 23, 2011 7:42:02 GMT -5
While the earlier post refers to the fact that the plan's dimensions for the wheels leave the flange too short, the fact is that a 5" frame height coupled with Kozo's coupler pocket leaves the centerline of the coupler slightly higher than the standard. In any case, the difference is only 1/16", which is unlikely to be significant.
Since I used a form tool for the flange and tread, my wheel config ought to be OK regardless of the tread diameter. It will be interesting to see what the frame height will be with and without the boiler weight compressing the springs.
|
|
|
Post by kenrinc on Jan 24, 2011 14:14:58 GMT -5
Your spot on about the frame height. I decided to not worry about the coupler pocket until the boiler is on because I'm not sure where the frame will "sit" at that point. Currently I'm at about 100lbs just with frame and cylinders.
What tool did you use to form the flange? Is it a full form tool? I think I'll go with a tool with just the tread to flange radius as a full form tool on my 10" lathe in steel is not going to cut it. The first time I cut the flanges in iron I did well but all the flanges came out too thin. It was my first time. After seeing a couple well machined wheels I understood what I did wrong. I didn't want to junk them because my castings are slightly unique in that they are prototypical A3 with square counterweights.. I didn't want to junk them so I went with steel tires shrunk on and need to now recut the tread.
Ken-
|
|
|
Post by kvom on Jan 24, 2011 22:34:17 GMT -5
The form tool I purchased cuts only the flange. I turned the treads first, then fed in the form tool until the inner radius met the tread.
|
|