Kadee 714 compatible coupler of the MTB SW1200

Kadee 714 compatible coupler of the MTB SW1200

Postby rdikken » Thu Oct 10, 2013 2:03 pm

Dear TT-Nut members,

Currently the height of the mounted Kadee 714 compatible coupler on the SW1200 is being discussed. It seems to be too low according to the Kadee guidelines, which state that the distance from the centre line of the coupler to the tracks should be 7,1 mm, in the case of the SW1200 it is 6,6 mm (see picture).

Why a height of 6,6mm? Because it resulted in an acceptable difference of +0,3mm from Gold Coast Boxcars which were the reference for the US TT market and an acceptable difference of -0,5mm from the Kadee standard . A Tillig compatible coupler can be used as well.

Why a Kadee compatible coupler and not the Micro Trains Line 1015 coupler? Because the MTL coupler is too small to adapt itself to the difference in height and the movements in the curves and switches. That is why MTB decided to supply the SW1200 with the Kadee compatible coupler.

Please be aware of the fact that MTB will introduce more US models with this coupler in TT gauge in the near future.

Rob Dikken
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SW1200couplHeigth.jpg
The steel rod in the picture is
an original Kadee part.
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Re: Kadee 714 compatible coupler of the MTB SW1200

Postby MacG » Thu Oct 10, 2013 3:59 pm

The MTL 1015 works very well, also by 310mm radius. The height is only a problem, if it is not installed at the same height at all cars and locomotives.
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Re: Kadee 714 compatible coupler of the MTB SW1200

Postby j p » Thu Oct 10, 2013 4:10 pm

Thank you for the explanation, although it is bad news. I will try to explain it to MTB too. Obviously, he has got wrong information. Your statement about the Gold Coast boxcars is purely wrong. That is why standards were introduced in model railroading many years ago. NEM in Europe and NMRA is North America. If you want to make sure that the model can run also at other people's layout and with other manufacturers' rolling stock, just follow the standard, don't expect that others would adjust their products according to you.
If you tried to measure the same with MTL 1025 coupler, you'd find the difference in height smaller and it is adjustable for the Gold Coast (or any other) cars! MTL 1025 couplers mounted without any adjustments on GoldCoast boxcar are around 0.5 mm under the TT coupler height gauge. MTL 1025 couplers mounted with adjustments (bolster shims) match exactly the TT coupler gauge. That is why PVM made the coupler gauge, to make it easy for everyone to get their coupler height correct.
Your point about the height is simply not true. No matter whether using MTL 1025 or Kadee 714, it is always up to the modeller to decide for the coupler height when mounting the couplers on Gold Coast, HP, Gandy Dancer, Star Line, Jewel, or any other cars. Both of the couplers can be adjusted in height. The 7.1 mm you refer to is not a standard. The Gold Coast cars are not standard either when not having their couplers mounted according to the standard (you can use them as a standard if you have the couplers mounted on them according to the standard, of course). The standard (NMRA S-2) says 7.14 mm from rail top to knuckle center, tolerance is 0.33 mm. http://www.nmra.org/standards/sandrp/pdf/S-2_2010.07.pdf

I have no idea where you got the point about the curves from? I test my models even on streetcar radii of old Zeuke track (R286 mm). No problem with MTL 1025, MTL 1015, MTL 1016, or Kadee 714.

It is easy to adjust the coupler height up or down for the cars - but it is not easy to do the same for the engines. For the engines it is only easy to lower the coupler. With a design based on wrong information, MTB made it difficult to get the coupler height correct and I hope that this mistake will be corrected on his future models.

edit:
here is a solution of the problem: try MTL 2001 coupler + shim instead. (The picture is for N scale)
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MTL2001.jpg
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Re: Kadee 714 compatible coupler of the MTB SW1200

Postby milwrd1 » Thu Oct 10, 2013 6:58 pm

I agree with Mr. jp completely :thumbup: :thumbup: .

As previously noted (in the other MTB SW1200 thread), to promote interchange (the ability to operate your models on another layout without any problems), couplers are mounted in accordance with a standard (in my case NMRA standard S-2, which states the coupler height is 0.281 inches or 7.14 mm from the top of the railhead to the coupler centerline).

Specifically for the SW1200, I test fit the MT 1025 and found it to long....possible interference with the truck. This is in addition to the 1025 coupler being to low. I have also mounted MT 1025 couplers on the Gold Coast cars......I have found slight differences in the height of the floor / underframe. Some cars required a thin shim and some did not.

I (similar to jp) have not experienced any problems with operation of the MT 1025, 1015, 1016 or 1021 couplers. I don't have any operating experience with the Kadee 713/ 714 couplers. My operating experience, however, only includes curves down to 12 inch radius.

Coupler height comments above about the Gold Coast cars and the MTB SW1200 are not meant to be negative!! I believe the underframe height was provided to address the needs of the majority of TT modelers. Not all TT modelers use the N scale couplers. We can figure it out. This is TT scale after all....isn't TT called "The Builders Scale"? :wink: :smile:
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Re: Kadee 714 compatible coupler of the MTB SW1200

Postby railtwister » Thu Oct 10, 2013 11:08 pm

Actually, the National Model Railroad Association does publish the standard for TT scale coupler height as being .281" (or 7.14mm) from the center of the knuckle to the top of the rail, with a tolerance of .013" (.33mm).

As for any documentation from MTL or Kadee concerning the mounting dimensions of their respective products, keep in mind that these dimensions refer to N or HOn3 installations, not TT. The N scale couplers from MTL are the closest to being the prototypically correct knuckle size for TT scale, while the HOn3 knuckle scales out to be oversize. However, the two sizes of couplers will couple up together, if they are both mounted at the same height. The trip pins for both couplers will require some re-bending to acheive proper height for TT scale applications, but this shouldn't be a great problem, since many modelers in all scales have been known to cut the pins off altogether, and use a manual uncoupling skewer rather than the typical uncoupler magnets buried in the roadbed.

As for the manufacturer getting the mounting pad at the right height, it's better if the pad is slightly too high than too low, especially in the case of a locomotive, since it's usually easier to add a shim between the coupler and frame to lower it to the correct height, than it would be to raise the coupler if it's mounting pad is too low.

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Re: Kadee 714 compatible coupler of the MTB SW1200

Postby ConducTTor » Fri Oct 11, 2013 12:16 pm

I believe coupling to European models with NEM standards was also a consideration in MTB's design. I don't think requiring a bit of modification from us is a big deal given that he had to meet 4 different coupling heights (NEM, Kadee, MTL, and correct or not, Gold Coast has set the standard on height therefore that is another requirement).

Isn't it nice for TT to now have 1st world problems?
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Re: Kadee 714 compatible coupler of the MTB SW1200

Postby j p » Fri Oct 11, 2013 12:43 pm

It seems to be misunderstood. Gold Coast boxcars do not have wrong coupler height by design.
They are delivered without couplers and it is up to us if we want to have them according to NMRA standard or not.
If wrong coupler height is measured on a Gold Coast boxcar, it is not Gold Coast's fault.
I have one of each of the Gold Coast boxcars and they all have their couplers around 7.1 mm above the railtop.

And of course, I don't see any problem in modification at all. But I see a problem in supplying wrong information to MTB. He would be happy to avoid this small problem if he got the correct info - even without any changes in the coupler base. He could just leave the coupler as it was and move only the knuckle up. (as MTL did in case of their 2001 coupler)
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Re: Kadee 714 compatible coupler of the MTB SW1200

Postby railtwister » Fri Oct 11, 2013 4:05 pm

ConducTTor wrote:I believe coupling to European models with NEM standards was also a consideration in MTB's design. I don't think requiring a bit of modification from us is a big deal given that he had to meet 4 different coupling heights (NEM, Kadee, MTL, and correct or not, Gold Coast has set the standard on height therefore that is another requirement).

Isn't it nice for TT to now have 1st world problems?


Hi Alex,

While the European NEM may be different due to different coupler design, there is only one American TT coupling height standard, and that is what's specified by the NMRA. None of the dimensions shown in the instructions for MTL couplers are for TT scale, they only apply to N scale installations. Similarly, any dimensions in the Kadee instructions are only for HOn3 and are not for TT scale. Neither MTL nor Kadee intend their couplers be used for TT scale. The information on the MTL & Kadee instruction sheets can be used only as a general guide as to how the couplers are assembled, but pay no attention to the dimensions, they are correct only for N or HOn3, but not TT!

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Re: Kadee 714 compatible coupler of the MTB SW1200

Postby ConducTTor » Fri Oct 11, 2013 6:08 pm

Bill I realize that. What I'm saying is that for the NMRA TT standard, there need to be different coupler mounting "area" heights to accomodate both Kadee and MTL. Then there also needs to be a different height for NEM couplers. And yet another one if Gold Coast's default height is considered a standard. I would argue that it can be since for many years they were the one and only real producer of NA TT. If there's a single manufacturer they by default become the standard.

So what I'm saying is that MTB likely made a few compromises in order to accommodate all of the above.
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Re: Kadee 714 compatible coupler of the MTB SW1200

Postby Tom Dempsey » Fri Oct 11, 2013 6:54 pm

Gee Alex, during the time that Gold Coast was the "single manufacturer", I purchased kits from Possum Valley. I'm reasonably sure they were manufactured in Virginia. In addition, our hobby is replete with manufacturers putting out equipment that didn't meet one standard or another (or sometimes any as near as I can tell). If you just screw a MTL coupler to a Gold Coast car, and it isn't 31.5-33.5 scale inches from the rail head to the middle of the coupler, you need to get it there. Same with any other RTR, scratch-built or kit car in any scale. If a Gold Coast car is the standard for your model railroad, so be it, but for the sake of interoperability, I'd say set to the NMRA standard in North America. Yes, it does mean you'll have to shim and keep more than 1015's on hand, hey, just like the real railroad.
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