Restoring Atlas contacts

[jagged ben]

(Caveat - I don't own any Atlas locos, so my comments refer to a Kato truck, but I think the design is similar.)  ...

...

This is a critical caveat that should not have been in parentheses.   

The thread was about Atlas.  You are correct that the design is similar, but I believe it is not the same in the respect we are talking about.  Perhaps it was a failure of the Atlas engineers to understand the concept of the Kato design. 

However, the trucks roll a little bit better with the axle cups in place, so I think the axle cups bear a fraction of the weight

This is subjective, but I would say that Kato trucks roll a lot better with the axle cups in place.  Whereas with Atlas trucks (the HTC trucks, at least) arguably do not demonstrate a discernible difference in overall friction.  The axles flop around more without the cups in place, but I'm pretty sure that if you apply the same amount of force to get one moving, the distance it rolls on straight track won't be much different. 

[jagged ben]

I either need a better camera or a better lighting setup, or both, to get pictures of the Atlas truck that are similar to Gary's.  (It's also harder to see the relevant stuff when both the axles and the truck tower are black.)  But here's one interesting photo that also demonstrates something I forgot about the HTC truck.

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What do you notice?  Hint:  I take back what I said above with respect to the middle axle.

[peteski]

Yes, I misread the gear part.  Still, all 3 axles are load bearing (and the weight transfer is still at the needle point bearings).  On a flat track-work of course.
Ben, I might just take you up on the challenge and when I find some time, give you my version of how those Atlas trucks work. How about Atlas 2-axle trucks?
As for the low-friction part, why do you not consider them as such?  Their design is very similar to the Kato low-friction trucks. 

[jagged ben]

Ok, I did do some 'experimenting' since the last post, and I will walk back my comments somewhat, but not on some key points. 

I agree that the Atlas designs look similar to the Kato.  And I agree it's reasonable to assume that whoever designed those trucks thought they were copying the design principles.   However I still maintain that the execution of the Atlas HTC truck fails to do that, and that the truck tower plastic is actually resting on the outside plastic axles at least  most of the time.  Whether they didn't really understand the Kato principles, or whether they just screwed up the dimensions in the design and tooling process, I can only speculate on.  However, the way those outside axle housings are flat on top, and the well documented middle axle 'hop' due to the extra round space and the fact that the cups don't bear down on that axle...  those things suggest maybe the designer didn't fully understand what they were trying to achieve.  (Not saying I could have done better, just observing the result.)


As far as other Atlas trucks, including 2 axle trucks,  I'll reserve comment until I have more time to look at a few more.  I took apart a GP35 tonight and was frankly surprised at how well the trucks rolled on their own, because in the past I recall very poor rolling examples, particularly with the GE sideframes.  With that said, it did seem that the cups might be reliably supporting those trucks on the axles.

I was being a bit facetious about Atlas not being low friction, but this is what I mean:

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That's an HTC truck, parts cleaned and checked and reassembled.  And no, the photo is not rotated nor are there any other tricks going on.  That board is raised up at about 35 degrees. In my experience this is not a fluke result.The truck does not roll on its own.  Period.  Not with a little nudge to get it started, like some need.  Not at all. You can get the wheels and gears to turn if you apply a minimal downward pressure and move it back and forth.  But the truck's own weight does not apply enough grip to the rails to overcome its internal friction.  Whether this is the fault of where the weight bears, or the cups, or the gears, I don't know for sure.  But it's not a low friction truck!

[peteski]

Ok, I did do some 'experimenting' since the last post, and I will walk back my comments somewhat, but not on some key points. 

I agree that the Atlas designs look similar to the Kato.  And I agree it's reasonable to assume that whoever designed those trucks thought they were copying the design principles.   However I still maintain that the execution of the Atlas HTC truck fails to do that, and that the truck tower plastic is actually resting on the outside plastic axles at least  most of the time.  Whether they didn't really understand the Kato principles, or whether they just screwed up the dimensions in the design and tooling process, I can only speculate on.  However, the way those outside axle housings are flat on top, and the well documented middle axle 'hop' due to the extra round space and the fact that the cups don't bear down on that axle...  those things suggest maybe the designer didn't fully understand what they were trying to achieve.  (Not saying I could have done better, just observing the result.)


As far as other Atlas trucks, including 2 axle trucks,  I'll reserve comment until I have more time to look at a few more.  I took apart a GP35 tonight and was frankly surprised at how well the trucks rolled on their own, because in the past I recall very poor rolling examples, particularly with the GE sideframes.  With that said, it did seem that the cups might be reliably supporting those trucks on the axles.

I was being a bit facetious about Atlas not being low friction, but this is what I mean:

That's an HTC truck, parts cleaned and checked and reassembled.  And no, the photo is not rotated nor are there any other tricks going on.  That board is raised up at about 35 degrees. In my experience this is not a fluke result.The truck does not roll on its own.  Period.  Not with a little nudge to get it started, like some need.  Not at all. You can get the wheels and gears to turn if you apply a minimal downward pressure and move it back and forth.  But the truck's own weight does not apply enough grip to the rails to overcome its internal friction.  Whether this is the fault of where the weight bears, or the cups, or the gears, I don't know for sure.  But it's not a low friction truck!

Yes, the Atlas truck design is undoubtedly based on the Kato design.

Are the gears in that poorly-rolling truck clean and dry, or did you also lubricate them?  Grease in the gears would dampen their movement.  The other problem with Atlas trucks is that the wheelset axles are too short, thus too loose in the bearing cups.  That makes them ride too high in the gear frame. But as they come from the factory, their gauge is too tight.  If you properly gauge the wheels, that increases the axle length which will make them roll better.  Or even better, replace them with the new Kato wheelsets.  But axle length of Katos is actually too wide, which binds them in the Atlas axle cups.  I press the half-axles in slightly (using an arbor press and a fixture) to give them optimal lenght.

EDIT:  Also, the Atlas trucks have few more small idler gears vs. single large ones in Kato trucks. That results in more friction of the gear-train.   But I'm pretty sure that if I roll a clean an unlubricated Atlas truck where I corrected the axle lengths (so the axle doesn't have much play in the bearing cups), it will roll almost as well as Kato (and much better than your example).