The Canadian

[CNR5529]

I wonder if the problem is that the CAD drawing is made in a way that the axle point is riding in the center of the bearing cup, when in real life the axle has some play in it, so it rides a bit higher in the axle cup?

This definitively seems like the case on many cars, yet others roll quite freely. Add in some other QC issues with the pickups being bent, and we seem to have figured out what is going on. Fortunately these are all simple enough issues to fix.

[Angus Shops]

One would think that with the design being done in CAD, there should not be any clearance or interference issues between various parts of the car (like axle and the center frame).  I wonder if the problem is that the CAD drawing is made in a way that the axle point is riding in the center of the bearing cup, when in real life the axle has some play in it, so it rides a bit higher in the axle cup? Just a theory.

As good a theory as any. When I hold a car upside down in my hand and spin the axle with my finger, it seems to spin (mostly) freely. But when I put the car on the track, not so much. Only on some cars though. There seem to be some very close tolerances and any slight motion of the truck or variation in the way the parts go together causes a problem...

[muktown128]

One would think that with the design being done in CAD, there should not be any clearance or interference issues between various parts of the car (like axle and the center frame).  I wonder if the problem is that the CAD drawing is made in a way that the axle point is riding in the center of the bearing cup, when in real life the axle has some play in it, so it rides a bit higher in the axle cup? Just a theory.

Sounds like they may need a cup check 

[bbussey]

Took a lunch break and worked on my D&H dome.  I removed the trucks and they rolled well independently, so I'll leave them as is for now.  The centersill slopes down under the outer axles slightly, but it's enough to interfere.  I shaved it even with the bulk of the centersill and that improved operation tremendously.  It's no longer running as if the brake shoes are engaged.  Still not as free-rolling as the New Haven cars though.

[MRLX1020]

Another approach so as not to modify the beautiful center sill and draft gear pan details - Kadee # 209 washers.  These are very much like the full size 3/4" thick fabreeka shims for 24" central bearing center plates - as used by Budd on most outside swing hanger trucks.  Two shims per bolster location and you're good to go.  This also solved a few droopy couplers in the set.

[bbussey]

I'd rather modify detail that won't be seen unless the car derails and flips rather than raise the ride height by 3 scale inches, which also raises the coupler height.

[MRLX1020]

The shimmed cars coupler height gauged out better with the shims than without overall, so I'd say its a winner.  I had several loose cpupler cover screws that helped once tightened up.

I shared my findings with Rapido, in the event it helps someone else who might be slightly frustrated at this issue.

[peteski]

Period! 

[CNR5529]

Well, its definitively prototypical!

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If the shims add the clearance that was lost by the truck sitting lower on the axle cones than they were supposed to, that means the car once shimmed is back to where it should be height wise. In other words, out of the box it may be too low... will have to measure it out I guess.

[peteski]

If the shims add the clearance that was lost by the truck sitting lower on the axle cones than they were supposed to, that means the car once shimmed is back to where it should be height wise. In other words, out of the box it may be too low... will have to measure it out I guess.

True about  the overall height from the railhead, but shimming will increase the distance between the bottom of the car and the top of the truck, and that is where the excessive ride height is most visible.

[CNR5529]

True about  the overall height from the railhead, but shimming will increase the distance between the bottom of the car and the top of the truck, and that is where the excessive ride height is most visible.

I suppose the proper place to shim then would be between the truck frame and the pickups, which will be tough to do as the pickups sit on pins inside the truck.

[peteski]

I suppose the proper place to shim then would be between the truck frame and the pickups, which will be tough to do as the pickups sit on pins inside the truck.

If the real problem is with the axle points riding too high in the cups the the easiest and best solution would be to slightly push the axle ends out, to increase the overall axle length, but just long enough to ride in closest to the center of the cups, while still free rolling.

I still think that modifying (trimming) the center beam slightly is the simplest and easiest solution which does not change the ride height.

[CNR5529]

If the real problem is with the axle points riding too high in the cups the the easiest and best solution would be to slightly push the axle ends out, to increase the overall axle length, but just long enough to ride in closest to the center of the cups, while still free rolling.

I still think that modifying (trimming) the center beam slightly is the simplest and easiest solution which does not change the ride height.

So two things there, pushing the axles out will change the gauge of the wheelset, and although I myself am leaning towards just filing the centersill as others have done to create added clearance, it doesn't fix the fact the carbody may still be too low.

[peteski]

So two things there, pushing the axles out will change the gauge of the wheelset, and although I myself am leaning towards just filing the centersill as others have done to create added clearance, it doesn't fix the fact the carbody may still be too low.

Notice that I mentioned axle (half-axle) ends out. Push them  out further from the wheel face.  I do that to use Kato loco wheelsets in Atlas engines.  It can work to extend or retract the half axles.

[CNR5529]

I'll have to remember that for kato diesel axles, but for this case, the axles and wheels are one piece. Pushing out the axles will change the gauge...