Looking for help designing a truck axle pocket wear test fixture

[Lemosteam]

Looking for some thoughts here.  As you know I design some FXD passenger trucks that use metal wheels inside.  Some folks have asked me about FXD wear in the axle pockets and I don't have a useful answer!

That got me thinking of how I could make an inexpensive test rig,

Thinking of using a thick cardboard drum with a piece of track wrapped around it and soldered closed. Mount that directly to a used O Scale motor shaft (roundness and runout should not matter) more on that in a minute.

Above that would be a pivoted weighted or sprung stick with a sliding and pivoting mount for any truck. The stick would allow for track imperfection, side to side wobble and radial runout.

Mount the truck, lower it onto the "track" turn on the drum, at a relatively slow RPM. Let it run  for 7 days continuously or to truck failure, whichever comes first. Pull the axles and check for wear in the pockets-

Whatcha think?

So this would be kinda like a Drum Recording... lol.

[wcfn100]

Why not just run one of the cars on a circle of track?

Jason

[C855B]

Why not just run one of the cars on a circle of track?

I have a Unitrack figure-8 for this. Need to test with equal curves in each direction. Just use a throwaway loco, I s'pose.

I realize you're trying to placate 3D-printing skeptics on this, but I don't see it as much of an issue. FXD truck frames roll very nicely. Maybe not Delrin slick, but quite acceptable at least in my operating environment. Wear may be a factor for the 200 smph crowd due to heating at the the axle cone tip, but normal operation? Nah.

[learmoia]

Well as much as the cars will truly run on a layout.. the first 20 years of service, the 'wear' will likely smooth the FUD finish and improve performancnce.

~Ian

[Lemosteam]

Why not just run one of the cars on a circle of track?

Jason

@wcfn100 ,  No room, don't want hours on an engine.

@C855B Nope, no skeptics per se, mor like simple queries.  I am genuinely curious myself, and it will also provide some reasonable data.  I think having some wobble in the track on the tube will simulate curves decently,

@learmoia , I tend to agree, but it would be cool to test on a small rig.

The question really is do you think the concept will work/function as I envisioned.

[Mark W]

Some folks have asked me about FXD wear in the axle pockets and I don't have a useful answer!

Let it run  for 7 days continuously or to truck failure, whichever comes first. Pull the axles and check for wear in the pockets-

Whatcha think?

I don't have any logs or hard data to show for it, but I have several 3D printed trucks in use going on 6-7 years of operation.  They don't remain on the layout at all times, so my anecdote includes higher than typical handling as well.  The biggest risk to these trucks is getting the axle installed, once successfully installed and with careful handling, I don't expect they'll wear out in any measurable time frame.

[Lemosteam]

Thanks @Mark W , not too many folks can say that.

[learmoia]

Why not make a jig for the truck, mount a motor adjacent to the jig and turn the wheel rubber band style drive..

You'd have to measure rpm of the motor, but run it til failure and calculate the life with time x rpm.

[Lemosteam]

Why not make a jig for the truck, mount a motor adjacent to the jig and turn the wheel rubber band style drive..

You'd have to measure rpm of the motor, but run it til failure and calculate the life with time x rpm.

Hmm!  Like this?  Great simple idea!  With the truck upside down, the rubber band would also put pressure on the cone points of the axles into the FUD, in the same direction as and similar to the weight of the car.  Very unlikely the rubber band will stay centered either and will pull the axles along their axes quite a bit.

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Cool weekend project!

[learmoia]

Hmm!  Like this?  Great simple idea!  With the truck upside down, the rubber band would also put pressure on the cone points of the axles into the FUD, in the same direction as and similar to the weight of the car.  Very unlikely the rubber band will stay centered either and will pull the axles along their axes quite a bit.

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Cool weekend project!

I was thinking just doing one axle, but I was also thinking of the drive axle being perpendicular to the wheel and 'power' both wheels..  like the old Athearn plymouth rocket switcher  .

You would have some excess wear caused by the tension of the band.. but if you can keep it light enough, it would simulate pressure of the car sitting on the truck sitting on wheel.

[learmoia]

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If you turned the motor shaft 90deg (centered on the axle), that might take care of the drifting center problem..

[mmagliaro]

Get some of thoseof those Bachrus roller stands
http://www.bachrus.com/40series.php

And then rig up a little motor with a rubber drive wheel to ride against one of the roller bearings.
It would be a small roller, but I think it's doable.  Something about 1/8" in diameter.
Now a car with your trucks on it could just sit on the rollers and have one of its wheelsets continuously
running with the actual weight of the car on it.

Although I really think this is overkill.  I can't imagine running one of these long enough to actually wear out the truck cones.

[peteski]

I think that learmoia's idea is the easiest.  The rubber bands will already provide pressure equivalent to a weight of the car. Not need for rollers (since we aren't interested in the wheel wear.

[Lemosteam]

Get some of thoseof those Bachrus roller stands
http://www.bachrus.com/40series.php

And then rig up a little motor with a rubber drive wheel to ride against one of the roller bearings.
It would be a small roller, but I think it's doable.  Something about 1/8" in diameter.
Now a car with your trucks on it could just sit on the rollers and have one of its wheelsets continuously
running with the actual weight of the car on it.

Although I really think this is overkill.  I can't imagine running one of these long enough to actually wear out the truck cones.

@mmagliaro , Says the man who has just exhausted all resources for a valve handle.  Lol.  Not sure if I was clear. This is for axle points running in nothing but FUD  i.e. no electrical cone point contact.

@peteski I agree CHEAP and easy.  I don't want to twist the band though. I am hoping for a little wander so the band puts an axial side load on the axle pushing it into the FUD cone.

[OldEastRR]

And as soon as you make one, some mfr will come out with one.