I’m doing a little tune up on my Athearn BB SW switcher. (SW 900?) I have both plastic and brass worm gear replacements and was wondering which would be better and why? This is an early 90’s BB loco.
Thanks!
Probably six of one, half dozen of the other !
Plastic to plastic or brass to plastic will probably net no difference as far as performance and / or noise. The real difference would be if the first idler gear were brass (or other metal). If that were the case, definitely plastic, as a brass worm to a brass gear would be considerably noisier.
Mark.
As far as I can remember, Athearn has never used plastic worm gears in their H0 locomotives, the plastic worm gear is probably a LifeLike or Modelpower.
Some of the newer stuff have plastic worms in them. Here is an ebay listing that has an Athearn motor with the plastic worm gears. Mind you that the listing is just for illustration purposes.
While either one will work I found the plastic worm helps quiet the drive.
The older Athearn units here have brass worm gears in them while the ones purchaced just before most of the Blue Box locomotives were discontinued have plastic worm gears.
That’s kind of what I was thinking too. Both the brass and plastic are Athearn replacement parts.
Thanks all!
I never thought about this before. I only owned four Athearn locomotives and because of the unscale width hoods I disposed of those rather early; two were SD7/9s and two were Trainmasters. I do know that the Trainmasters had brass worms but I never paid much attention to the worm gears. I think I would follow Mark R.'s advice, however, and avoid brass-to-brass contact.
I’m wondering the same thing, which is better? I have a RTR Gp35 that I got as a dummy, so I have milled the frame to get a buhler into it, now I just need worms and couplings for a universal shaft.
So far it’s one vote for plastic.
BTW, I though the Athearn Traimasters were right as far as the wide hood was concerned.
I think it’s Atlas that makes the Trainmaster units.
My older Athearns all have brass worms but some of the newer ones have the plastic worms. I changed out the ones in my heavy haulers to brass.
I’m not sure who’s talking about what gear in this thread. The worm is the spiral cut (actually a helix) gear that turns at motor RPM. The worm gear is its mate; a gear that looks like it is square cut, but should be cut at a slight angle to match the worm.
Some gearboxes (mostly steam) add an idler worm gear between the worm and the worm gear to allow the motor shaft to be closer to horizontal. The taller gear tower allows univerals to couple the motor and better bearings so that the gear mesh between the worm and idler gear can be and remain precise.
The worm needs to be made of a harder material than the worm gear because of the higher pressure on the face of the teeth. Common combinations that work well are steel worm and brass worm gear, brass worm and plastic worm gear. As brass locomotive manufacturers proved years ago, making both worm and worm gear out of brass makes for a noisy and fast wearing drive.
Hope this helps
Fred W
I’ll echo Fred. All of my large roster of brass steamers (some dating from the late 'fifties) have brass worm to plastic or fibre/plastic gears, which makes for relatively quiet running and long, LONG life (I’ve never had to change out a plastic worm gear on any of my steamers, and I RUN them).
Tom
A WORM WHEEL is defined as:
A WORM GEAR is defined as:
Seems to me there’s an awful lot of people here just a little misinformed–and that, most certainly, includes myself.
So let me rephrase my previous response to loather’s query:Athearn’s Trainmaster used brass worms; I’m not sure just what material was used for the WORM WHEEL but I would avoid a brass-to-brass contact!
OK, I guess I was asking about the “worm” then. I used the brass worm which mates with the plastic worm idler gear and all is well.[:)] I tried both plastic and brass and couldn’t tell a difference in volume over the Athearn motor noise. I replaced all the bearings and a broken drive coupler and it runs great again. Now if I can just figure out how to add some weight in there to give it some more traction I’ll be a happy camper.(not much room in there.)
I stand corrected.