Hello; just finished repairing a 336 AF Northern; runs and smokes fine; question: what is the best min radius or diameter to run this loco on?  Using 20" radius fastrack for test and does OK but not happy.  Is there a difference in rail height between AF track and Fastrak?  Lastly, how to replace the front pilot truck spring?  The one in there now is flat!  Help and advise is much appreciated; Falcon70

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RoyBoy posted:

If you are careful, you can thread the new spring into place without removing the stud. Yank out the old spring first.

I have done it this way as well. Start threading it on from the large end first. I have come across some engines where the stud is threaded into the pilot truck but at the moment I can’t remember which ones. They are not the norm though.

UK and Roy; tried as you suggested as I have done the spring replacement that way on Lionel PW roller pick ups; too clumsy at my end on ths AF!  Have another issue on this loco; had the remnants of the original traction tires; removed them and it ran fine; installed some thin MTH tires and I cannot keep this loco on the track; it rolls over on both RH and LH curves; it fastrack or original AF track; runs fine on the straight track.  Running slow on the curve it begins to wobble and then rolls over; can always go bare rear rims but not stock; any ideas are appreciated; thanks; Falcon70

Winding a new spring on the stud is do-able, but difficult without distorting the spring. Very limited room to work doing that process. Not near as easy as winding a spring on a pick-up roller rivet. As to derailing on curves, loose tire on the wheel, wheel not centered on axle (wobbles when it runs), wheel(s) out of gauge. I assume you removed a pulmor tire (bonded to the wheel) and not a actual traction tire.

Gilbert 336 steamers did not have replaceable traction "tires". The traction material was bonded/vulcanized to the steel rim which was inserted into the white plastic insulator rim. A wheel replacement is in order or perhaps the wheel can be saved with "bullfrog snot" from Port Lines Hobbies.



You might want to check Port Lines Hobbies, they have traction tires that will work on Gilbert steamers, I recently replaced the traction tires on one of my Hudsons.



Check the rims of all the drivers. They come loose between the rim and the white insulator. That makes the loco fall off the track.

Push the rims side to side to see which ones are loose.

If they are loose, clean them with alcohol and epoxy them back into place. This is easier to do with the rods removed so the axle can be rotated by hand. Rotate the wheels to make sure the rim is straight before letting the epoxy set up.


Thanks for all the great info!  Yes, the 336 came with very thin traction bands on non grooved wheels; believe the later 5 digit AF steamers had grooved rims.  Removed the traction tires, polished the wheels and runs much better; no derailments and no noticeable wobble; 20" radius track is still to tight.  Ordered very thin "traction bands" from Portline; also checked the rims and wheels for looseness; none found.  And yes, the present day traction tires (no matter how thin) is a serious no no.  Again, thanks to all; take care; Falcon70

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