Test rig for FXD printed truck frames with metal axles.

[thomasjmdavis]

John,
Can't thank you enough for investing all the time and effort to do this testing.  Certainly addresses any concerns I had over using FXD trucks.

[C855B]

Good job. I know you have been fretting over this issue for a while, and am happy it has resolved to your satisfaction. Now... repeat the same thing with Photon resins...

[grinning, ducking and running]

[Lemosteam]

If someone wants to send me a set with axles, I'd be happy to!  But, because of the small radius of the drum, the axle spacing must be short and the spring area has to be ground away.

Not going to throw the est rig away anytime soon.

[Chris333]

Like before I've never had a problem with Shapeways trucks. I have dropped them before though    But I also dropped the Photon trucks and they didn't break. But being resin who knows if they will hold up over time. Maybe they will become brittle even though they are painted. And I tweaked the width till the wheels spun free with no extra work, this was in clear orange resin. When I switched to solid grey resin using the exact same file the axles where a little tight.

[SandyEggoJake]

Thx John.  Great test!   And looks like an interesting mini paint mixer as well!

If I may ask, what is the equivalent turn radius of the slight curvature you included? 

Of course, the variability in the design of the truck / journal box is a key factor in the durability of a specific truck.  And I'm still concerned by the stability of FXD/FUD over time, given the observation of oxidative degradation (as evidenced by crystal bloom) and how such that may theoretically lead to an increase in embitterment. 

And of course, to test, one ideally would modify your rig till it leads to truck failures (increase speed, distance, time and/or radius of track curvature) and compare to expected use.  Theoretically, the failure points would be wear in pocket trailing journal as well as potential to snap the box off, but such is looking less likely.

Still, would also be interested to learn if some of the axle point wear (if I'm seeing it correctly) could be reduced with lube?  While not needed in POM given it's greasy finish, FXD/FUD seems to be the opposite extreme - dry and abrasive.  So if compatible, a dry lube product like "Grease'em" (dry graphite) or a dry moly might get embedded into the FXD matrix, providing a Babbet like surface improving rolling operations / reducing fiction.

[TRW Drift Alert] 

@Chris333 Would be interesting to confirm similar results with other resins.  I suspect "Mama" is right... resin is as resin does.  I've been impressed (and surprised) by some side by side comparisons of FXD to Photon stuff in terms of layering - surprised as FXD is laid down at 16 microns while from what I've read the Photo layers are 25-100.  Perhaps fodder for a separate thread, but what do we know yet about the Photon resins vs FXD/FUD?  To your point, are you aware of any published comparative data on the various Photon resins?   (physical metrics such as elongation & flexibility etc)

[Chris333]

@Chris333 Would be interesting to confirm similar results with other resins.  I suspect "Mama" is right... resin is as resin does.  I've been impressed (and surprised) by some side by side comparisons of FXD to Photon stuff in terms of layering - surprised as FXD is laid down at 16 microns while from what I've read the Photo layers are 25-100.  Perhaps fodder for a separate thread, but what do we know yet about the Photon resins vs FXD/FUD?  To your point, are you aware of any published comparative data on the various Photon resins?   (physical metrics such as elongation & flexibility etc)

I have not seen any of this data. Pretty sure the Photon game is cornered by the war game folks. They pick resin by what cool color it is. For me it is all getting painted and if you leave it unpainted you still need to give it a UV clear coat.

Some use casting resin to make jewelry (dentist use it as well) and those folks might be more picky.

John,  I don't need a test on my Photon trucks, but if you want to play with them I can send a few your way.

This is all they are:

No notch to slide the axle in, but I can spread the side frames to get the axle in and with the brake beams you need to put in the wheels from above.

[tom mann]

Nice work, John.  I would let Shapeways in on your test results - they probably have no idea how FXD wears over time.

[chicken45]

This kind of asshattery also needs bannerized. 

[tom mann]

This kind of asshattery also needs bannerized. 

agree calling @David K. Smith !

[DKS]

[Lemosteam]

Thx John.  Great test!   And looks like an interesting mini paint mixer as well!

If I may ask, what is the equivalent turn radius of the slight curvature you included? 

Of course, the variability in the design of the truck / journal box is a key factor in the durability of a specific truck.  And I'm still concerned by the stability of FXD/FUD over time, given the observation of oxidative degradation (as evidenced by crystal bloom) and how such that may theoretically lead to an increase in embrittlement. 

And of course, to test, one ideally would modify your rig till it leads to truck failures (increase speed, distance, time and/or radius of track curvature) and compare to expected use.  Theoretically, the failure points would be wear in pocket trailing journal as well as potential to snap the box off, but such is looking less likely.

Still, would also be interested to learn if some of the axle point wear (if I'm seeing it correctly) could be reduced with lube?  While not needed in POM given it's greasy finish, FXD/FUD seems to be the opposite extreme - dry and abrasive.  So if compatible, a dry lube product like "Grease'em" (dry graphite) or a dry moly might get embedded into the FXD matrix, providing a Babbet like surface improving rolling operations / reducing fiction.

[TRW Drift Alert] 

@Chris333 Would be interesting to confirm similar results with other resins.  I suspect "Mama" is right... resin is as resin does.  I've been impressed (and surprised) by some side by side comparisons of FXD to Photon stuff in terms of layering - surprised as FXD is laid down at 16 microns while from what I've read the Photo layers are 25-100.  Perhaps fodder for a separate thread, but what do we know yet about the Photon resins vs FXD/FUD?  To your point, are you aware of any published comparative data on the various Photon resins?   (physical metrics such as elongation & flexibility etc)

@SandyEggoJake The radius is not as slight as you think at 9.36" at the centerline. 

The truck is 3 months old after Bestine cleaning in my UC, no protective coating or paint , just sitting in a tray in an uncontrolled atmosphere of my basement (and by the way, I have not experienced any of the crystallization/embrittlement that folks are talking about).

There is a point of diminishing returns (not to mention the electric bill).  This is not Mythbusters, one does not have to destroy something to determine how long it lives.  I once knew a high speed bearing (needle, ball, tapered roller) engineer who once told me that with bearings, once you test past a certain point in a bearing's life and it has not failed it will live forever, properly maintained.

Lets do some math.

-Radius of drum = 0.65" 
-Radius of wheel = 0.1031" 
-Drum to wheel ratio is 6.3 (.65" drum radius / 0.1031" wheel radius)
-Drum turns at 2.65 RPM avg rated per motor specs
-Wheel turns at 16.695 RPM (2.65 motor RPM x 6.3 ratio)
-Wheel's circumference is 0.648" (0.1031" x 2 x Pi)
-Distance of wheel travel per revolution is 10.818" per minute (0.648" x 16.695 RPM)
-Distance traveled per day is 15,578.00" per day (10.818.00" x 1440 min/day)
-Distance traveled in test of 7 days= 109,045.00" (15,578.00" per day x 7 days)
-Distance in miles= 1.721 miles (109,045.00" / 63360 inches per mile)
-Distance in terms of 30" pieces of Atlas flex track= 519.26 pieces (15,578.00" / 30")

I'm thinking that any other variables won't matter (increase speed, distance, time and/or radius of track curvature), but the graphite could help.  It may not be evident in the video, but some of the movements that the truck endured were fairly severe in miniature.  there is a point at each revolution where the entire truck bumps (near derailment) and must realign with the track.  There are also vertical undulations (misaligned rail joiner type) that the truck endures.  The track curvature simulates a never ending "S" curve.

I also suspect you have not rolled one of these yourself to see that they are as nearly as smooth rolling as an MT truck or Kato passenger car truck with electrical cups.  If you like i will mail you a pair to try at a grueling NTrak show for a different real life scenario.  PM me if you would support the trial.

Also I do not believe that there is any axle wear at all (although I had no way of measuring it before or after accurately), because as you can see the original machining marks are still on the part in the near exact locations as another axle from the same wheelset batch. I believe that the only wear is the removal of the coating that FVM uses, down to the raw metal and that is the buildup you see in the truck pockets:

[DKS]

...and how such that may theoretically lead to an increase in embitterment.

Hope you meant embrittlement...

[Maletrain]

Hope you meant embrittlement...

I might be embittered if those FUD bobber caboose underframes get embrittled.  Not so easy to replace those, as it is with trucks.

[Lemosteam]

Hope you meant embrittlement...

Corrected. Mr. Eagle Eye.   

[SandyEggoJake]

embitterment.

 

This is not Mythbusters, one does not have to destroy something to determine how long it lives.

I do love MB so....  and of course finding the failure point is a routine part of materials torture testing. 

Thanks for the math.    So that would be about equivalent to 100 cycles on a 3x6" roundy-round?  Seems a fair minimum test distance - at least to find wear issues.

Yep, one could go nuts here, if the wanted to have fun with it.  For example, we've not touched on the "proper" weight for the truck (spring tension) or real world track issue like frog crossings, stop and go, drag, and transitions to and from vertical curves ... etc, etc.  But it's your rig... we are just enjoying any results you are willing to produce with it!

Still, it would be interesting to see the performance of the truck off a Photon.  But it seems an archbar design like that by @Chris333 , and his pocket too, are more fragile than what you tested.   Totally get you were testing to a different objective - a specific design to address the level of your own concerns.   But to be able to draw meaningful conclusion re resin performance, or even use of FXD for trucks of ALL designs, a better test would be to take the most frail prototype one may use (@Chris333 archbars, perhaps?) and test head to head using both prints of FXD vs best challenger resin.

But no... I won't be "embittered" if you pass.