# Body mount vs truck mount Kadee question



## San Juan (Jan 3, 2008)

I know this topic has been posted and debated many many times. But I have a specific question that I do not think has been addressed before.

First some background info to help you out.

Our layout uses Kadee couplers exclusively. G scale, not #1 gauge. Form the start I went with truck mounted. Not sure why now that I think of it, but that's what I did. To keep things the same over the years, I've stayed with truck mounts. But with the new Kadee prototype looking knuckle head that has recently been announced and may already be out, I thought it might be time to look into the slow and expensive process of converting to body mounted couplers.


I have no clue what the minimum radius is on our layout. I do not use prefab curves and have hand bent and assembled all of our track (Llagas Creek). I had some old LGB track to use as a guide and I made sure our tracks were wider then an LGB R2. So whatever the R2 radius is, we are greater then that. And actually way over an R2 for the most of the layout. The only tight spot is a reverse loop. But it is still wider than an R2. And the loop is actually wider now then when I first laid it. An Accucraft C-16 sometimes would derail in the same spot on the loop. So I eased the curve and reduced what minor grade (less then 1%) there may have been. But if I have to ease the curves any more, I'll pretty much have to redesign the loop and will need a huge amount of fill dirt and a lot more expensive track to do it. The loop as it is now, required one dump truck load of fill dirt to complete. 


Th only time anything close to a body mounted coupler has been used on our line was on a Bachmann 2-8-0. The Kadee I installed was not mounted to the tender truck, but to the frame. So this is a body mount. And it worked fine throughout the layout. It even worked fine on the loop before I widened it for the Accucraft C-16. But it was always coupled to truck mounted cars. 




My question is; if one body mounted coupler connected to a truck mounted coupler works fine, is it likely two body mounts would work as well? I suppose the best thing to do would be to simply buy some and test it out. But I'd hate to have to install the body mount, which usually requires cutting and body modifications, and have them not work.


Any tips or information you can provide is appreciated. 

I just remembered, our little LGB #50 Davenport also has body mounted couplers. It works fine as well. I guess this also includes our twin LGB moguls with front couplers, and the removable mogul plow I have with a coupler. But again, the rolling stock that connects to these are all truck mounted.


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## Greg Elmassian (Jan 3, 2008)

The answer is yes, it is likely. 

If you were really just "on the edge" of body mounts working, then yes, you could maybe have a problem. 

I don't measure R2 curves, but under 8 foot (diameter) is where body mounts typically don't have enough swing. 8 foot is fine, 10 is great. 

Regards, Greg


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## chuck n (Jan 2, 2008)

Matt:

As I recall the LGB R2 (1500 series) curves have a diameter of 5'. This is just a little larger than the R1 (4'). I imagine that this was done to put a loop just outside of an R1 to get proper clearances. 

I used to have an R2 loop on my train in Denver, but I can't remember if I had any body mounts at the time. This was 16 years ago. 


It is much easier to back up a sting of cars, into and out of curves and switches, if you are using body mounts. 


You can measure your radius without too much difficulty. You need a piece of string and a nail. Tie the string to the nail and drive the nail into the ground about 3 feet from the inside rail. Take the loose end of the string and hold it against the rail. Holding the string slide it along the curve. If the string leaves the rail towards the outside rail the nail is too close. If you finger crosses the rail it is too far. Keep moving the nail until the string is at the same length through the section of curve that your are measuring. Measure that distance and you will have your approximate radius. I don't know if the radius manufacturers use is to the inside rail, outside rail or the midpoint.


Chuck


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## RimfireJim (Mar 25, 2009)

Here's an idea, Matt, borrowed from my engineering experience: 
Rather than modifying some actual cars, which you are loathe to do, make some quick, cheap and easy prototypes to body mount some couplers to. Should be as simple as a board with maybe a couple of bolsters for the trucks and maybe some shim blocks for the couplers. Make them as short as your shortest car, or slightly less for a "margin" test. Borrow some trucks from some of your cars. Weight them if needed. Test and evaluate. As Wernher von Braun said, "One test result is worth one thousand expert opinions."


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## San Juan (Jan 3, 2008)

Thanks for the info.


Jim, never thought to make a simple test car. That's easy to do. 


But make it as short as my shortest car? I would have though it would the opposite, as long as my longest car.


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## Nicholas Savatgy (Dec 17, 2008)

Matt, I can tell about Kadees is on 40ft cars the 789 will do a 5ft dia curve ok, the 830s get a little hairy going around but if you stick with the 789's you will be fine..


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## Mike O (Jan 2, 2008)

Matt, 
A while back I built a test track specifically to test body mounted couplers. The track had a 4' radius curve, a reverse curve of the same radius, and a crossover using number 4 switches (turnouts) with 7.5" between track centers. Number 4's have an effective radius of 4'. I model 1:20.3 and used 30' cars (about 19") for testing. The worse case scenario is the crossover - it creates a very tight reverse curve. The cars were able to negotiate test track with out derailing. When I reduced the radius to 3.5" the cars frequently derailed. The couplers were 830's in standard draft gear. 

Hope this helps. 

Mike


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## San Juan (Jan 3, 2008)

Nick, thanks for the info on the 830 and 789 differences.

And Mike, yes that is very helpful. I rum 1:22.5 D&RGW narrow gauge so pretty similar to your 1:20.3 and 30' cars. 

I actually never thought about the switches. Shoot, I think we have #4 switches, meaning a 4' radius? That might make things tight.


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## RimfireJim (Mar 25, 2009)

Posted By San Juan on 09 Dec 2009 03:23 PM 
Thanks for the info.


Jim, never thought to make a simple test car. That's easy to do. 


But make it as short as my shortest car? I would have though it would the opposite, as long as my longest car.

Oops, you're mostly correct. Actually, it would be the car type that had the most effective overhang. I say "effective" because I'd have to think about how the ratio of length between trucks and length between truck and coupler works out. You can probably picture that as the overhang gets less, there will still be an angle between couplers but the offset from the centerline of the track will be less.


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## East Broad Top (Dec 29, 2007)

When I reduced the radius to 3.5" the cars frequently derailed. 
At 3.5 inches, I would think so!  (Sorry, couldn't resist.) 

A quick test on my workbench with 2' radius track shows that on a typical* 1:22.5-sized car, a Kadee #830 (standard body mount) has sufficient side play to easily stay coupled to a truck-mounted coupler. (* LGB stock car used as test platform.) That's with around 3" between the bolster and the coupler face, and around 10" between bolsters. Performance in an actual train may vary from the test, but at least the geometry works out. Assuming that your minimum radius is actually wider than 2.5', you should be in the clear. 

As Mike illustrated, your bigger worry isn't so much the body-to-truck mounted couplers on curves, but the body-mounted couplers on reverse curves (passing sidings, crossovers). We run nominally the same equipment on my dad's railroad as you do on yours. We've been running body-mounted Kadee#1 couplers for 25 years over R3 (3.8' radius) switches and passing sidings. I can't imagine you'd have any issues with the larger G-scale couplers. If you start running the longer 1:20 equipment, then you're gonna have issues. I just tried two 1:20 passenger cars through a 5' radius crossover; they wanted no part of that. But with the shorter 1:22 equipment, you should be fine. 

Later, 

K


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## steam5 (Jun 22, 2008)

When I got my first couple of 1:20.3 AMS freight cars I ran them through R2 curves okay from memory. They have body mount couplers. 

Alan


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## San Juan (Jan 3, 2008)

Judging from all of your very helpful posts, I think I'll be OK.

I'll get a few 830s and see what happens. If they don't work out, at least I know truck mounts work fine


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## Greg Elmassian (Jan 3, 2008)

I prefer the 830's for the realistic slack action. By the way, there are the new couplers available, so you might want to look into them, they have an improved appearance, are even stronger, and the knuckle return spring is now pretty much hidden. 

The "casting" also looks a lot more realistic. 

Regards, Greg


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## San Juan (Jan 3, 2008)

I like the slack action of the 830 style box as well.


When I get some for testing, they will be the "new look" versions. The new more prototypical looking coupler is partly the reason why I thought about converting to body mounts.



If anyone is unfamiliar with the "new" Kadee couplers. Here is a link: New Generation Kadee G Couplers


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## Torby (Jan 2, 2008)

You use the 830 box with the "shank" style coupler?

















Or with the Centerset?










I like the slack action too. Saw it at Cozads with his 64 hoppers.


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## Mike O (Jan 2, 2008)

Matt, 

Number 4 switches have a closure radius of about 48". The radius through the points is actually a bit tighter. if you are using switches designed to replace a curve section of track, then it isn't an issue. Couplers with shanks are more forgiving than the centerset that Torby showed above. As Jim pointed out the length of the cars is an important variable, but the distance between the truck center and the coupler is just as important. Too much and the ends of the cars swing too far out. That said, most of your 1:22.5 cars should not have a problem. I can run two 25" long Hartford passenger cars through my number 4 crossover largely due to the small, but important, tangent track connecting the diverging legs of the switches. The parallel track is on 7.5" centers. 

Mike


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