The project: Convert an Athearn SD40P into an SD40.
This involves cosmetic and mechanical alterations. Cosmetically, the steam generator has to be removed behind the two long rectangular grilles
Mechanically, the original SD40 truck won’t work with the resulting “porch” on the rear of the locomotive, so I thought I’d substitute an Athearn SD40-2 truck. This has a much lower gear tower and platform that the bolster sits on. So the bolster itself needs removed and a lower one fabricated from brass. Now the motor rides way too high for this truck, so I very laboriously milled out the white metal frame under the motor to lower it about 5/32"
Sometime during this process I also took on the meticulous task of cutting the steam generator off the body and fitting a new rear body section from a GP35 shell, makin sure there’s internal clearancesfor everything. Lookin good though.
Well,after all the cutting, fitting, fabricating, milling, soldering, hours and hours, not to mention countless assembly-disassembly-reassembly procedures, it was all assembled and ready for a test run. Place 'er on the layout. turn on the power, throttle up. It runs alright. The wheels turn alright. There arent even any vibrations, the culmination of all that milling. Both trucks are performing smoothly and powerfully. After all this work, all I can do is sit there with my mouth open while the locomotive runs in one place as reality sets in that these SD and dash2 trucks run…
IN THE OPPOSITE DIRECTION!!![xx(]
Sounds like you have replaced the trucks in the wrong order. Put the front one on the back and the rear one on the front and see if that corrects the directional running. Don’t ask me how I know this!
Bob Boudreau
Canada
Are you saying that you are using one truck from one engine and the other truck is from a different model? Actually, all Athearn diesels should have a clockwise gear tower and a counterclockwise gear tower in each engine since they are being driven off the same shaft.
Yes, Athearn uses the same worm gears in all their locomotives, but the SD40 trucks have the worm driving a BIG gear that drives 2 of the axles directly, the 3rd by a idler.
SD40p trucks have…Worm / gear/ axle
The Dash-2 type trucks have worm / gear / idler / axle.
Yup, that idler in the Dash 2 makes the trucks go in the opposite direction than the one without.
The obvious solution for me is to get another Dash-2 truck for the front of this locomotive and modify the bolster-n-such like the rear one. I just thought y’all would get a kick out of this post. It does look mighty strange sitting there running, doing its own little tug of war. It scoots back and forth about 1/2 inch. Dan
Unfortunately I have no advice on how to sort this out since I have no experience with something like this. I sure can sympathize with you though. The sinking feeling in the pit of your stomach when, after a lot of work, something doesn’t do like it’s supposed to, isn’t any fun at all. Good luck on getting it straightened out.
Tom Watkins
As a short-term fix, you could try removing the worm drive and driveshaft from one truck - the loco will only be powered on 3 axles but it will run. This would allow you to operate it while waiting for replacement parts to become available. Fitting a “-2” front truck will probably improve the running, especially if you can get the one-piece driveshafts from the new-type SD40-2 to fit - these are much quieter in my experience than the old multi-piece units
I know how you feel. Its like when youve just spent a week on your favorite engine putting in DCC, QSI sound, Lights and all the rest. You put in on your layout and think to yourself, this is great… You hear the sound, see the lights and the great smoke effects, and then you realize…
you didnt install a smoke system[xx(]
I like RRing Brit’s suggestion, run one truck till I get the other Dash-2 unit. Actually I contemplated just powering one truck when I first started the project, but decided to go to the bother to power 'em both. Now it’s a matter of principal.
Bob’s suggestion works when an Athearn is running backwards, but on both trucks. Dan
I have been thinking of this same conversion … now I am thinking twice. Why Athearn made an SD40P is one of the great mysteries of model railroading.
The other problem is at the end of the day what you have is an EMD engine where the hood is too wide since Athearn did not get around to correcting that for years to come.
Dave Nelson