November 29, 2007

Mechanical Problems with New Athearn UP FEF 4-8-4

Athearn Locos

We just received the latest Athearn Genesis steam release, the UP FEF 4-8-4. Customarily when a new release arrives we are all eager to see it in action. We were quickly disappointed with this loco's speed control. We tested several more with the same results. All other aspects of the loco were comparable to prior Genesis releases.

The speed control definitely appeared to have a mechanical problem we have come to know as "stiction" in that the loco would not move until speed step 30/128. Once the mechanical friction was overcome the loco took off.

There was essentially no proportional low speed control. We were able, once the loco was moving, to back off to about speed step 20/128 and lower the running speed. At about speed step 20/128 the loco jerked to an abrupt stop. Next we increased the start voltage by programming CV2=30 which gave us marginal improvement. The stiction was still the winner and low speed control continued to be poor.

To prove to ourselves that this was not the sound decoder motor control problem we swapped the FEF tender with an Athearn Challenger tender (which has the identical decoder) and the Challenger started at speed step 7/128 with much better low speed control.

Some users have reported that "running in" helps a little?

For those of you who have purchased this loco from us we are in the process of contacting you to determine if you want the loco or not. Please call if you have not heard from us by Friday, Nov 30, 2007.

This is all reminiscent of the Athearn Genesis 2-8-2 releases several years ago. Nice detail, smooth gearbox and running gear but the locos had no traction and would walk off the rails in curves. The problem was that the loco was not balanced and tail heavy that resulted in the poor traction and derailing. Athearn was notified by many users but continued to issue subsequent releases without correcting the problem!