Kadee 880 Coupler Height Gauge

Kadee 880 Coupler Height Gauge Measurements Vignette
Ted Doskaris
REV GE-B October 23, 2010 - Added Appendix A for Kadee 980 vs 880 gauge

REV GE-B1 July 4, 2016 - fixed changed address for NMRA S2 standard

Coupler Height for 1/29 scale - Kadee 880 "G" gauge vs Prototype vs NMRA observations

(Note: In addition to the coupler height, it is to be appreciated that the Kadee 880 gauge also includes a track width gauge and wheel gauge. The focus of this vignette is only concerned with the coupler height.)


The first thing to check into is some authoritative reference material.

Prototype reference material indicates the following:

I located an example of actual prototype railroad authored material of the 1950s era from the former Western Pacific RR. This material includes measurements of standard gauge coupler centerline height from the rail head. There are two possibilities in the drawings with measurements of 34 inches or 34.5 inches.


Note the EMD GP7 road diesel shown below has a coupler height dimension of 34.5 inches.


The GE 44 ton switch engine shown below also has a coupler height dimension of 34.5 inches.


However, the EMD switch engine shown below has a coupler height dimension of 2 ft. 10 inches (or 34.0 inches).


So what should the coupler height be? See below:

More specifically, the U.S. government document, Code of the Federal Register, CFR 49 section 232.2, includes the following stated requirements (expressed in terms of a drawbar) for prototype 1/1 railroad freight car coupler heights for various track gauges:

"[Section] 232.2 Drawbars; standard height.
Except on cars specified in the proviso in section 6 of the Safety Appliance Act of March 2, 1893 (sec. 6, 27 Stat. 532, 45 U.S.C. 6) as the same was amended April 1, 1896 (29 Stat. 85; 45 heretofore designated in compliance with law is hereby modified and changed in the manner hereinafter prescribed,to wit:

The maximum height of drawbars for freight cars measured perpendicularly from the level of the tops of rails to the centers of drawbars
 
for standard-gauge railroads in the United States subject to said act shall be 34 1/2 inches, and the minimum height of drawbars for freight cars on such standard-gauge railroads measured in the same manner shall be 31 1/2 inches, and
 
on narrow-gauge railroads in the United States subject to said act the maximum height of drawbars for freight cars measured from the level of the tops of rails to the centers of drawbars shall be 26 inches, and the minimum height of drawbars for freight cars on such narrow-gauge railroads measured in the same manner shall be 23 inches, and
 
on 2-foot-gauge railroads in the United States subject to said act the maximum height of drawbars for freight cars measured from the level of the tops of rails to the centers of drawbars shall be 17 1/2 inches, and the minimum height of drawbars for freight cars on such 2-foot-gauge railroads measured in the same manner shall be 14 1/2 inches."

CFR 49, section 232.2 comment:
Each of the three U.S. gauge types (standard, narrow, and 2 foot) as specified  have the same 3 inch (respective nominal height + or - 1.5 inch) spread.

CFR 49 that includes section 232.2 can be viewed at the below link:
CFR 49 section 232.2 Drawbars; standard height


Model railroad reference material indicates the following:

The NMRA S-2 Coupler Standard for Couplers All Scales is at the below link:
NMRA S-2 Coupler Standards

When looking at the table shown in the above link, note the following:

"G" scale includes "Proportion" 1:20 - 1:32 for knuckle coupler with coupler height of 1.125 inch.
Thus, for "proportion" 1/24 scale that falls within this range, 24 x 1.125 inch = 27.0 inches if compared to prototype 1/1.
AND
Thus, for "proportion" 1/29 scale that falls within this range, 29 x 1.125 inch = 32.625 inches if prototype 1/1 for standard gauge.
AND for number 1 scale:
"#I" scale is only one "Proportion" value at 1:32 with coupler height of 1.063 inch.
Thus, 32 x 1.063 inch = 34.016 inches if prototype 1/1.


Now for the Kadee 880 gauge

Shown below is an excerpt from the Kadee spec. sheet:


The Kadee 880 coupler #1 scale spec. for what they identify as "B" for coupler centerline to rail head is 1.0625 inch. Thus, it looks virtually identical to the NMRA specification (that appears to be rounded up) for "#I" scale.

The Kadee 880 coupler "G" scale spec (again for what they identify as "B") is 1.125 inch. Thus, it looks to be identical to the NMRA spec. for "G" scale.

Shown below is the Kadee 880 gauge example I acquired:



What I measured on this example Kadee 880 gauge was 1.115 inches to the casting seam of the coupler that I believe to be its center.


Coupler height summary

1)  The coupler height for U.S. standard gauge as per CFR 49 section 232.2 when expressed in percentage has a spread of 4.5% (nominal + or - 2.25%).
2) The CFR 49 Standard gauge nominal of 33 inch height for prototype 1/1 scales down to 1.138 inches if 1/29 scale.
3) The NMRA S-2 Coupler Standard for "G" scale Knuckle coupler is specified only at one value, 1.125 inches for all "Proportions" (e.g. scales) ranging from 1/20 through 1/32 (specifically, 32.6 inches if scaled up from 1/29 to prototype 1/1) - thus, 1.1% lower if 1/29 with respect to the CFR.
4) The example Kadee 880 gauge coupler height measured 1.115 inches from the rail head surface (or 32.33 inches if scaled up to prototype 1/1) - thus, about 2% lower than prototype 1/1 with respect to the CFR.  Hence, the Kadee 880 example gauge is well enough within the prototype allowance with respect to CFR 49, section 232.2, to be deemed accurate. The inference here is that there should be an allowable + and - height tolerance with respect to what each Kadee 880 gauge actually measures at when using the gauge for determining what is an acceptable coupler alignment.

 

Appendix A -  Kadee 980 Gauge vs. Kadee 880 Gauge

The Kadee "New Generation" model # 980 Gauge is the newer version of the 880 Gauge with the apparent difference being limited to its housing containing the newer, more prototypical, AAR type "E" Kadee 900 coupler.  

The Kadee family of new "E" type couplers include draft gear box assembly models 906 and center set 907 that correspond to traditional respective models 830 and 789. They use the same respective gear boxes.

Shown below is the newer Kadee 980 Coupler Height Gauge on the left with the traditional Kadee 880 Gauge on the right.

As can be seen, either of the gauges could be convered to the other by just changing the couplers or the gear box assembiles.  


Shown below is a more direct view of the two gauges coupled together.


As can be seen, the alignment of horizontal casting seams of the two coupler types is virtually the same - so either gauge can be used with both newer and traditional Kadee couplers to check for proper coupler height if you focus on the couplers' horizontal casting seams to see that they line up.

End

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