zero apples = zero pad

oh, you want to body mount the couplers?

I've always hated the Athearn

I've always hated the Athearn blue box engine coupler mount.  Even Life Like copied it on their early Proto 2000 diesels like the SD9's I have.  Ultimately I have sold off all of my blue box Athearn engines so that has "resolved" the coupler mounting problem for Athearn engines I had.  I do still have a few of the Proto 2000 engines so eventually I'll have to deal with them.

Thanks Scott, I will give

Thanks Scott, I will give that value a try. 

Sure, I could go grab a dial caliper myself as you just did. I just find it surprising and slightly infuriating that It isn't common information out on the internet. 

I mean this is something modellers did, and occasionally still do for years and years. 

The Athearn coupler mount is not ideal, but it functions. 

Couple I simply ditch the Athearns? Sure, if I wanted to decimate my fleet and start over. As I said, this particular unit has sentimental value to the club. It's not replaceable. 

As annoyed as I am by the lack of specific information on doing the conversion, it's not a particularly hard one to do. in either form, leaving them mounted to the frame, or to the shell. Worth it compared to the replacement cost at least.

FYI, .225 inches is 5.7mm.

FYI, .225 inches is 5.7mm. I'm going to try rounding that up to 6mm and see if that is acceptable. 

OMG!!!!

Coupler height

Joe, can you go through the

Joe, can you go through the math and examples on 5 thousandths of an inch being an issue? .3mm translates to less than a 64th of an inch (but more that 1/128th of an inch) We're talking a mismatch that approaches imprecitible to the human eye. As noted above, I have a hard time believing you could have any model that met that tolerance. I would not be surprised to learn that simply pulling out the slack on a train would deflect the couplers at least that much if not more.

You're right, sort of

Sorry, you're right, I wrote that in a hurry and I was thinking 0.010".

Attached is a photo of a coupler that's off between 0.010" and 0.015". I put a gray (0.010") Kadee fiber washer in and that solved this mismatch.

This is off enough to possibly start giving problems at the top or bottom of grades if the vertical curve is very sharp. Here is what this much coupler height difference can start to look like at the bottom of a grade ...

The differences add up and notice that on the start of the grade, the coupler jaw engagement is approaching just half the jaw. If there's a heavy train behind this coupler joint, the train may pull apart.

My 0.005" comment was off, but my main point that "close enough" doensn't work for coupler alignment is true. On the top photo, the coupler height test needs to be considered a failure. Circa ~10 thousandths is still off and needs fixed, although ~5 thousandths would be close enough to be considered a pass as to coupler height.

So yes, I mis-spoke on the measurement, but coupler height is one place where "close enough" is asking for trouble. Spot-on is more like it -- or to be more precise, +/- 0.005" is about the limit. (If you want to prevent operational problems, that is.)

In those 2, the couplers also

In those 2, the couplers also appear to be drooping which will exacerbate the mismatch, because the slack will straighten them out and/or the heads don't meet straight on. 

I tend to agree with your broader point about coupler height accuracy being a place where "Fudging" is not disired, within reasonable tolerances. 

Yep

Yep, that's the point. On couplers, fix ANY droops and height mismatches and don't fudge!

The one on the right looks

The one on the right looks like an E&C shops.  I can't place the one on the left - it looks like Athearn but the draft gear does look Athearn.

Body mount?

I don't like body mounting engine couplers, it seems like installing a trailer hitch on the tailgate of your truck instead of on the frame. It's not hard to thread the metal frame mounting pad  and screw mount Kadees. ....DaveB

Except that it is hard on the

Except that it is hard on the GP38-2/GP40-2/GP50, because you need to mount the couple from above and so the minute you fill in the front of the loco or even just put on a plow, it becomes a pain. You essentially need to cut off the metal pad anyway if you want to mount the coupler from below and at that point, any strength the assembly had is out the window.

I have a number of locos that are shell mount by design. They all seem to be reliable. 

As for the trailer hitch on the bumper. It works perfectly as long as you keep within the load limits. This is the same. The Athearn shell is plenty strong and the 4 clips holding it to the frame are also quite resiliant. 

coupler height variance is unavoidable AND prototypical

Fabricating styrene pads

Not difficult at all when you use a known dimension like .020 styrene.  Build it up even with the top of the coupler on the body then drill and tap for 2-56 screw, mount good 'ole #5 in it's own draft gear and then check the height. Add as needed.

" it is hard on the

When the coupler goes thru a plow I slide it in and insert the screw from the bottom, up thru the threaed metal and on thru the coupler box. .....DaveB 

Conviently, there are a bunch

Conviently, there are a bunch of Styrene strip products that are at 6mm wide.

NMRA Coupler Height Gauge

I'm surprised modelers don't have a coupler height gauge.  It has a nice little tang on the other end to measure the height of the mounting surface of the couple. Very easy to use, much easier than a caliber. The green circle is the tang on the gauge that'll give you the correct height to mount the coupler at.

Here's how it's used to determine the height mounting surface.

The one that is shown is for HOn3 but the idea is the same as a standard gauge coupler height gauge. I see Joe's dosen't have a tang on it unless it's out of the picture to the right.

Bernd

What from what was posted in

What from what was posted in this thread would lead you to believe I or anyone else in this thread doesn't have a coupler height guage? I mentioned using one.

That doesn't alter the fact that it's unnecessary to custom fit the pad for every loco as usually suggested. I don't think my normal height guage has that shelf on the back. In fact I'm positive it doesn't.

Proper mounting height

Alas, I've seen so many

Alas, I've seen so many people (our club included) mount the gauge at the end of a piece of track making it impossible to use the back.

The coupler gauge is not

The coupler gauge is not really mounted,  as it fits on the track, and you should be able to pick it up and put it where ever you want to use it, unless your club has figured out a way to permanently mount it.

The older Kadee HO scale gauge I have is all metel,  I'm not sure if newer versions are insulated,  so the power to the track your using it on needs to be off.  And yes, the backside of the Kadee HO gauge gives the height, as Joe has said.  There is enough room to roll the car slightly over it, and see what you need for shim thickness.

Mike.

mounting pad height gauge.

It's a simple job to glue up a stack of plastic and make a gauge to check the mounting pad height above the rails. I make the gauge in an X pattern with the top piece extending a bit under the car body and the lower piece sitting on the rail tops.....DaveB