What some people do is to make a drawbar out of a piece of plastic and semi-permanently couple them together. It's unlikely that you would want to run the B unit by itself and if you feel like running the A unit by itself, replace the drawbar with the coupler of your choice.
-George
"And the sons of Pullman porters and the sons of engineers ride their father's magic carpet made of steel..."
Just a shot in the dark here...but you know in the 'real' F7's, there were diaphragms sticking out from the door at the A unit and both ends of the B unit?? The diaphragms should meet when the units are running together, so the crew can safely go from one unit to the other. The bodies aren't supposed to be right on top of each other, or touching each other. The diaphragms occupy several scale feet between the units.
On mine F7A/B set, I made a plastic drawbar and added American Ltd. diaphragms.
American Limited makes a close coupling kit for the Athearn F-7s.....
http://www.walthers.com/exec/productinfo/147-6100
I had an ABBA set of Athearn RTR Warbonnet F-7s (which I quickly got rid of after I got my first Genesis Warbonnet F-7), and they worked out really well. They brought the units closer to where they should be, and were relatively easy to install. The only "major" part of the installation was trimming the part of the frame that holds the coupler pocket.
Santa Fe all the way wrote:I suppose you would round the ends of a rectangler piece of plastic or metal and drill holes at each end.
What the !@#^ was Athearn thinking when that designed these engines?
I always found the hardest part of the F7 upgrade was filling in those gaping windshields. And then came Stewart & the Highliners and all my Athearn F7 upgrade projects went into the trash.
Despite my new found hate for the Genesis Line (or is that the new owners of Athearn?), I still admire these old Blue Box units as they were the main stay of the hobby for almost 30 years.
Here are some photos of how I close coupled my Athearn F7 dummy by relocating the couplers...
First cut the monting pad flush with the ends of the frame and plan to use Kadee couplers. I used 30 series because they don't have as much material at the rear of the coupler to interfere with the trucks. (A good option now is to use the new #153 short "Whisker" Kadee's and trim the back of the box to allow for a tighter fit.)
At the rear I used square styrene stock and drilled and tapped it for 2-56 screws. I think the photos are self explanatory. (click on the photo to enlarge)
If don't mind a little more spacing, another option is to use the remains of the monting pad and drill a new mounting hole as I did on the front.
The Broadway engines are left alone as they are with the couplers. They are sometimes in manifest service or are able to drop off the booster units for A-A unit service where turntables are not availible.
I did have a set of drawbar on a Athearn 1500 Cow and Calf and learned that they dont flex very well causing the units to fight over which truck should be lifted off the track.
Here are 2 photos that show the correct 3' spacing of 2 coupled F units.
The PRR F3 on the left is a P1K body on the Athearn F7 frame modified as shown above. The CPR F7B is a Highliner body on a Kato chassis with the Kadee coupler kit installed.