Several good suggestions - thanks everyone. The link to the kadee website is really helpful - I had not visisted that site before. It should be straight forward in selecting a compatable draft box and an offset shank coupler - paying attention to plastic or insulating the coupler
I've done a number of these on old Athearn GP9s and F7s. I just found it easier to file down the old pin and box, tap what's left for a 2-56 screw and then mount a plastic Kadee box with a #5, #58 or #148 coupler.
It takes an iron man to play with a toy iron horse.
Go to the Kadee website. The "what fits what" list calls out a #37 coupler for the Athearn F7 (the geared model, and another one for the rubber band model), and has a good illustrated "how-to" sheet. It calls for drilling and tapping the old Athearn coupler box pads, (#50 tap drill, 2-56 tap) to secure the #37 coupler box. You can do it with a hand held pin vise. I have a drill press and that works just fine. I have never used a hand held power tool (Dremel or electric drill) and I don't recommend them for this job. The Athearn supplied plastic clip on coupler box/cover is worthless, it fits too loosely, and will fall off while running on your layout. Drill and tap, that works. The #37 is a non conductive plastic coupler. It's plenty strong enough.
If you drill the mounting holes as close to the center of the locomotive as you can, you will obtain a reasonably close coupled diesel setup.
You need non-conductive couplers on locomotives. Conductive couplers conduct to the hot chassis of the locomotive, which is directly connected to one running rail. Consider an AA diesel lashup. The hot chassis of one unit connects to the north rail, and the hot chassis of the second unit connects to the south rail, and when the conductive coupler connects the two hot but opposite polarity chassis you have a direct short circuit.
Over the years I have learned that the Kadee "what fits what" list is dependable. It's possible to warp an #5 Kadee into nearly anything, but using the Kadee recommended coupler will save you a lot of hacking and filing and cussing.
David Starr www.newsnorthwoods.blogspot.com
PA_NPRR I recently purchased an older Athern F7 locomotive with hook horn couplers and want to replace with Kadee knuckle couplers. The original hook horn mounting does not have the boxes typical of contemporary models and there is not a lot of room to fit a Kadee box. Are there suggestions from anyone having done such a replacement?
I recently purchased an older Athern F7 locomotive with hook horn couplers and want to replace with Kadee knuckle couplers. The original hook horn mounting does not have the boxes typical of contemporary models and there is not a lot of room to fit a Kadee box. Are there suggestions from anyone having done such a replacement?
If you use standard KD#5, the metal couplers will be in contact with the frame and may cause a short. As G Paine pointed out, there are KD's with a plastic shank, however they will stick out a lot and the plastic clip that comes with the Athearn is horrible IMO and the coupler will be sloppy in that type of mounting.
The recommendations I've seen is to tap out the hole in the metal tab to take the 2-56 screw and use it to mount a KD coupler with it's own box. That would solve the shorting problem AND give you a much more solid mounting.
Problem is, if you used a KD#5, it will come out too low. To get it to match the KD heigh gauge you'll have to file the frame mounted couple tab so it matches the surface of the KD height gauge, as I saw in a magazine article, or use a coupler with an offset head. That will raise up the whole box to close to correct height.
An alternative would be to buy a KD with the underset shank so it will bring the coupler up to close to correct height.
Either way, the conversion from hornhooks on the old blue box Athearn F7 frame may not be simple, unfortunately.
Personally I think the old Athearn blue box coupler mounting system on the engines was the worst thing about them.
Rio Grande. The Action Road - Focus 1977-1983
Eric WhiteAnother downside to doing this is that the metal coupler is part of the electric circuit for the locomotive. This can cause shorts if you couple two Athearn locomotives together with metal couplers back-to-back, as the frame in each locomotive takes its power from the opposite rail.
A Kadee #28 is like a #5, but in plastic; this should address the potential elecrtucal short issue.
https://kadee.com/htmbord/page28.htm
I do not see a plastic whisker coupler on the Kadee chart
https://kadee.com/htmbord/coupler.htm
George In Midcoast Maine, 'bout halfway up the Rockland branch
mbinsewiBut, if you have the plastic box that snaps in place, holding the coupler in, you can just pop that box off, replace with a Kadee #148 whisker coupler, and snap the plastic box back on. The problem that can arise from this, is the new coupler may sag or droop just a little bit, as it's not quite as thick as the horn hook.
Another downside to doing this is that the metal coupler is part of the electric circuit for the locomotive. This can cause shorts if you couple two Athearn locomotives together with metal couplers back-to-back, as the frame in each locomotive takes its power from the opposite rail.
Things can get really exciting if you add a DCC decoder to the mix, as the short will fry the decoder.
Eric
Welcome ! Not sure just how old you mean, gear drive? or rubberband drive? Here's one option, from the Kadee web site:
https://kadee.com/conv/pdf/ath9.pdf
But, if you have the plastic box that snaps in place, holding the coupler in, you can just pop that box off, replace with a Kadee #148 whisker coupler, and snap the plastic box back on. The problem that can arise from this, is the new coupler may sag or droop just a little bit, as it's not quite as thick as the horn hook.
https://kadee.com/htmbord/page148.htm
Check out the Kadee web site.
Mike.
EDIT: OOps! Frank beat me to it!
My You Tube
To The Forums.
Kadee coupler conversion chart for Athearns. Look up EMD F7 geared/rubber band drive whichever You have. Mine are done this way.
https://kadee.com/conv/hocc_athearn.htm
Take Care!
Frank