N Scale Truck Reamers?

[SandyEggoJake]

For controlling weight delta, I'm with @MK. 

If testing a wheel swap, easiest is just to start with a metal wheelset load taped on top of the trucks with plastic wheels and test. 
Then swap the wheelsets to the metal ones, with a plastic wheelsets as the load & retest. 

I expect the result of the first to be more than 10 and second to be less than 14 ... thought with the added weight, donno.  Both might right shift some too, but with less but still a material delta.

[narrowminded]

@narrowminded

Love the test rig... though expected a duel gauge rig from you to test both N & Z trucks on the same set up!

Thanks.   I had that piece of scrap laying about from a prior track radius cutout so when I saw the idea of the cradle I decided to just throw it together and see what there was to see.  Having seen the possibilities and usefulness I probably will put together a Z track one as that's the one I'm most likely to get some real use from.  I've already fiddled with some printed Nn3 cars and the printed axle pockets are definitely varied in their performance.  I have just lifted the end of a test track which demonstrated the extremes but this rig is actually easier and much more honest in its information.  It's beautiful in its performance and simplicity.

[narrowminded]

For controlling weight delta, I'm with @MK. 

If testing a wheel swap, easiest is just to start with a metal wheelset load taped on top of the trucks with plastic wheels and test. 
Then swap the wheelsets to the metal ones, with a plastic wheelsets as the load & retest. 

I expect the result of the first to be more than 10 and second to be less than 14 ... thought with the added weight, donno.  Both might right shift some too, but with less but still a material delta.

I'll do that tonight.   

[narrowminded]

For controlling weight delta, I'm with @MK. 

If testing a wheel swap, easiest is just to start with a metal wheelset load taped on top of the trucks with plastic wheels and test. 
Then swap the wheelsets to the metal ones, with a plastic wheelsets as the load & retest. 

I expect the result of the first to be more than 10 and second to be less than 14 ... thought with the added weight, donno.  Both might right shift some too, but with less but still a material delta.

Here's another video.  Back to back trucks, one metal wheelset, one plastic.  Cycles about the same as single truck examples with just wheel swaps.  This shows that it gives repeatable and usable data void of mood or opinion.  More well designed tests should afford even more useable information.  I'm done for now but the direction and basic idea is there.  Have at it if this kind of data could be useful to you.

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Edit add:  Had two more MT trucks with plastic wheels in the junk box.  Tested both and got the exact same results.  Four for four says something for MT consistent product.    And really that should be no surprise.  Machinery is like that.  When ALL parts and service conditions are the same the results will be the same.  It can't be otherwise.

[C855B]

I had a similar test setup many years ago, also comparing plastic vs. metal, including a horizontal curve to factor resistance from side forces. Two things to consider that I discovered - first, prying the sideframes to change wheelsets contributed to inconsistency. The sideframes did not magically resume their original position, spreading had a toll in loosening the axle. That was the conclusion I drew when running A-B-A tests, plastic-metal-plastic, where the third run was nearly always better than the first, and in some cases equal to the second (metal).

Second, plastic axles against plastic trucks, run repeatedly at a fairly high speed (similar to your test arc), would generate enough warmth through friction where test results would degrade consistently through subsequent runs, probably due to softening of the plastic. Metal axles did not exhibit this.

The conclusion of my tests was to adopt metal wheels across the board, but in retrospect I wonder how much influence in the improved performance was from the axles alone.

[ednadolski]

Were those plastic wheels in the test the pizza-cutters or low-profile?

Ed

[narrowminded]

Were those plastic wheels in the test the pizza-cutters or low-profile?

Ed

They were relatively new trucks that had shipping damaged couplers in them.  The wheels are low profile but I suspect the performance wouldn't change as that's an axle and tread finish thing which I suspect are the same.  I could dig through and find an old wheelset and test that if it would help.

And it's these kinds of questions that suggest the possible usefulness of a tool like this for serious modelers or clubs, especially since most could build a totally workable rig from scraps laying about.  A low effort, low tech, no BS test.

[SandyEggoJake]

Thx @narrowminded

Some thoughts. 

Code 55 v code 80:

Yes, code 55 might bend better.  However my concern is for some old OEM trucks for which one might seek a baseline would have pizza cutters... and flanges bouncing off spike heads wouldn't isolate the test to improved axle point pockets.  But I guess would still be a fair test for general improvements one might see from an improved truck on a code 55 layout.  Thanks again.

@C855B

Interesting observation about warming plastic axle / truck pairs results in test data degrade, though I doubt such was from "softening" of the plastic (POM?), but perhaps rather thermal expansion leading to a tighter pocket?  Even so, hard to fathom much difference...
 

[ednadolski]

However my concern is for some old OEM trucks for which one might seek a baseline would have pizza cutters... and flanges bouncing off spike heads wouldn't isolate the test to improved axle point pockets.  But I guess would still be a fair test for general improvements one might see from an improved truck on a code 55 layout.

One other thought re: pizza cutters.  The larger flanges would induce greater drag against the rail surfaces when used on regular (horizontal) layout curves.   Since this test jig is a vertical curve, it is in effect tangent in the horizontal plane, so the extra drag of the pizza cutters would not be noticed.  The PC's could perform equivalently on the jig, but worse on a layout with actual curves, esp. for longer trains.

Interesting observation about warming plastic axle / truck pairs results in test data degrade, though I doubt such was from "softening" of the plastic (POM?), but perhaps rather thermal expansion leading to a tighter pocket.

Seems to me the 'warm' condition is the normal operational state (unless operations means just moving the train a few feet, then waiting for it to "cool" again).   I'd suspect that it's not a significant or even measurable effect (much less anything approaching a 'softening' of the plastic), but anyone wanting to be sure could always point an IR camera  at the truck to look for "hot boxes".... 

Ed

[narrowminded]

 I am very familiar with the newer NMRA  RP-25 standard because I actually drew those profiles for the programming and machining of the 24", 26", and 33" wheels for my projects.  And when comparing to an old pizza cutter wheel, its shape is very similar with the exception of the flange.  The standard has the tread at a 3 degree taper across the tread, transitioning to a .008" (if my memory is right) radius to the vertical flange, which at the end of the .008" radius immediately starts a second opposite arc away from vertical until it intersects at a point on the C/L of the outer perimeter of the flange with a mirrored arc heading back towards center on the wheel back.  The pizza cutter appears to skip the second reverse arc heading outward towards the perimeter and instead just heads straight out to the perimeter at an angle away from vertical and ending at the outer perimeter with no return arc down the wheel back. 

What all of that results in with either style is that when running, the wheel really only contacts the rail at a point somewhere on the tread and/ or up to the tread/ flange transition radius but in normal operation the rail side never contacts the vertical flange.  I think it's also why the idea of the excess diameter that was the pizza cutter flange was so easily dismissed in the new standard as being nothing more than unnecessary material that is just along for the ride, hanging out in the breeze, never contacting the rail so serving no real purpose in actual service.  It might have helped placing the wheels on the rails but not much else.

I had some pizza cutters in the junk box so assembled a couple of trucks with them and just ran them.  Initially one ran eight cycles and one ran nine.  A careful inspection (as well as the sound they made) showed that they had the typical gunk buildup found on dirty wheels so I took them back out, cleaned them, and sure enough, 10-11 cycles for both trucks.  No change from the later RP-25 wheel profile.  Very consistent running.

[up1950s]

Warming axles  , me thinks gunk at the axle ends is a bigger tightening threat to free rolling . Maybe allowing more side play ( amount ? ) would neutralize hot wheel expansion and allow a degree of space for  some gunk to call home ?

[narrowminded]

Warming axles  , me thinks gunk at the axle ends is a bigger tightening threat to free rolling . Maybe allowing more side play ( amount ? ) would neutralize hot wheel expansion and allow a degree of space for  some gunk to call home ?

That's not heat.  The whole point of the pointed axle for this very light load and relatively low RPM is, small contact diameter, therefore minimal circumference, therefore extremely low SFPM travel, therefore no friction, therefore free running and no heat. 

What is present is plastic to plastic which works OK in this application because it's not a demanding application at all.  But the like materials actually have more friction than dissimilar materials.  Best with delrin is hardened steel but close enough at these low loads is just about any metal that you're likely to want to machine in these small dimensions, and with a nice finish.  I suspect that's also the main source of the improved performance in metal wheelsets vs: plastic.  Maybe the wheel to rail contact too but I suspect it's mostly the metal axle to the delrin frame.   That's a test for someone else or another day.

[peteski]

Warming axles  , me thinks gunk at the axle ends is a bigger tightening threat to free rolling . Maybe allowing more side play ( amount ? ) would neutralize hot wheel expansion and allow a degree of space for  some gunk to call home ?

I think that (as it often happens in online forums) we might be overthinking this a bit.  What's next the quantum physics friction theory? 

[wazzou]

It seems it would make more sense to have say a 3-4' long section with a grade of some steepness at one end, a flat tangent section and a smaller grade at the opposite or return end and a measurement can be calculated on how far it rolls back in inches using a seamstress tape glued beside the test track.
But I still wouldn't go to all the trouble.

[up1950s]

I think that (as it often happens in online forums) we might be overthinking this a bit.  What's next the quantum physics friction theory? 

Ahhh ... degree of angle of slope sheets in quad hoppers .