Replacement Athearn Bombardier BiLevel Trucks, aka making the train roll

[nscalbitz]

Well it wasn't the success I'd hoped it would be, but I would still call the experiment a success because we improved on the performance of the original design....
Craig

PS: Fredrick I'm still pissed off that my Dinner Train was a complete fail so if you feel I've embellished at all in an effort to have SOME success from the day please add any corrections. Folks Fredrick has no feelings. Only computations and hypothesis.

PPS: That was supposed to be a joke either in case Fredrick has feelings and is insulted, or in case I'm right, and he had to be told it was a joke.

These kick-a$$-in-the-head moments are often ROFLMAO ones too... glad you pro's know what you're doing !
BTW, my first ever Rapido souvenir (CBQ) Baggage car will roll onto a Kato CZ as a 'replacement' car at some stage.
Hope to try more in future,
regds Dave

[CNR5529]

or in case I'm right, and he had to be told it was a joke.

Noted...

LOL, the results of my analysis match your findings. The new trucks are an improvement over the stock arrangement as we were able to pull a 7-8 car train. (And boy was I pleased to see that train start to roll!) However the coupler/diaphragm problem caused binding on some curves which stalled the trainset. That and the true scale couplers were infuriating to couple without the centering!!! I also agree on the keep alive caps.

Bottom line, this is a partial success. I think grades would have been problematic, and there is still room for improvement. Stay tuned for Rev. 2.

P.s. I was so focused on programing the ditch lights on your loco and cab car, I never even saw the whole diner train on the track! 

P.p.s Pics or it didnt happen. 

glad you pro's know what you're doing !

It only looks like we know what we are doing... HAHAHA. To be fair, and I've said this before, if this was an easy problem to solve, someone would have solved it already. So yeah, a bit of engineering and a bit of experimenting is going on here.

[mmagliaro]

IIRC @mmagliaro experimented with using (inexpensive) micro ball bearings in his scratchbuilt loco but abandoned that idea. One of the problems was very poor electrical conductivity. Yes, you can install wheel wipers but that increases friction . . .

Exactly correct.  Not only that, but the decrease in friction from using miniature ball bearings vs a thin steel axle in a bronze bushing is not very guaranteed.  Those little 681 and 681x bearings don't roll as smoothly as you'd think.  Where they might shine over a bushing would be with heavy loads, but that isn't the case here with a little N Scale car to carry.

A thought on getting the bushings located exactly right so they are both centered on a given axle...  Yes, this is an absolute must.  And if they are mounted in a rigid way, I don't think you can ever make it work.  They have to float just a little so that the axle can find its happy place going through the two bushings.  My experience with this from my 0-6-0 mirrors yours with regard to a misalignment of only .001" being "huge".  I have an idler gear running in two of those bushings.  I found that the only way to make it work so that the gear axle would spin freely in the bushings was to put the bushings into their holders, put an axle through them, clamp everything down, while repeatedly spinning the axle with my fingers to make sure it was free
when I got the clamps right.  THEN solder the bushings in place so the wouldn't move.  And yes, an error of only .001" or so would make the axle bind up badly.  There is not a lot of slop in those bronze bushings (which is as it should be).

My case was with a gear, so I couldn't allow any slop in the bushings.  But for wheels in a truck, you certainly can.
Perhaps reaming out the insides of the bearings just a hair would make the whole thing very tolerant of any slight misalignment when assembling them.  They make 1.55mm chucking reamers.  http://www.northbaycuttingtools.com/0610-155mm-hss-chucking-reamer-53300610

You could spin one of those through the bearing to open it up from 1.5 to 1.55 (that's only .002").  But the assembly tolerance and rolling quality would improve.

[RBrodzinsky]

A few weeks ago, @peteski asked about how the Athearn inner rolling bearings fare against the Kato Amfleet bearings (and, also, these new ones, which are still a work in progress). So, I decided to give it a test myself.  I strung together 23 of the Kato Unitrack 248mm (9.75") straights. I created an ~8% launching ramp (4.5" in first 55") and then a long straight track (which scared the heck out of the cats).

The launch point
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Looking back from end to launch
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I tested not only the AmFleet and Athearn Bombardier, but a number of other cars, too.  You can see that I had a number of Kato passenger cars that ran into the bumper at the end of the 23 sections of track. The Kato CalTrain coach 3860 hit the bumper at speed, while most of the others were already slowed down.

While the Kato Amfleet cars did better than the Athearn Bombardier, neither do very well compared to the others.

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Also, here are a couple videos of the testing.  First the Athearn Bombardier

And a Kato Bi-Level Cal Train car

[peteski]

Great info Rick - thanks for setting up this experiment!  You could have most likely got valid info from a much shorter track with gentler incline but you went al out with a huge ramp and long coasting truck - I like it! 

What is not surprising is that all of the 2-axle outside-bearing  (axle-point/bearing cup) trucks had much less rolling resistance than any inside-bearing trucks. Those trucks have very low rolling resistance.

One thing which is skewing the results is the mass of those cars. The heavier cars will have more momentum. The ideal test would be to run each pair of trucks under the same car test body.  Or I suppose the mass coudl be used alongside of the rolling test results to nullify the effect of the car's mass. We would need one of our resident math experts to come up with a formula to do that (and we would need to know the weight of each car).

For example I wonder if the Athearn Caltrain cab car has a different mass than the coaches?  That could explain the difference between these cars (even though they use identical trucks).

I'm also surprised by the difference between Kato Amfleet Cafe and Coach.  They weight just about the same and use identical trucks. Is is possible that one of them has more running time (more broken in) than the other? Kato greases the Amfleet trucks with small globs of grease in each bearing - maybe if the grease is thoroughtly spread into the bearing changes its rolling resistance?

What is missing from this test (and what I was hoping for) was a comparison between the Kato Amfleet and those custom built Athearn inside-bearing trucks we are discussing here.  But I realize that you had no way to test that truck.

[RBrodzinsky]

Agghh, I had meant to weigh the cars, but when my wife got home, I got distracted in cleaning up my experiment. I no longer have access to good lab scales, so will have to use a kitchen scale. May not be sensitive enough.

Both Amfleet cars are brand new, delivered today. I also order a pair of replacement Kato trucks, so I can check if they make a difference.

I went for the steeper slope after I couldn't even get the Athearn cars to roll down the full length of a 1.5% grade on the JACALAR. Then I just kept lengthening the coasting track for the cars, until I ran out of easily accessible straight Unitrack, so that most cars didn't reach the bumper.

I had fun

[CNR5529]

Love it! Thanks for sharing your results. We should be able to duplicate the ramp to compare any mods here as we carry forward. I should also be able to duplicate the unmodded result as a control...

[RBrodzinsky]

Besides mass(weight), I might try rerunning part of the test, to measure the exit velocity from the ramp. With mass, initial velocity and distance, we can calculate friction. Granted, it will be in scale-mph, but converting is easy.

The videos show how much slower the Athearns are vs the regular truck Katos on exit of the ramp.

[nkalanaga]

In theory, the mass wouldn't affect the exit velocity from the ramp, Galileo proved that.  It would affect the momentum, and thus the roll-out distance.  In practice, it would also affect the exit velocity, because it would affect the friction in the trucks.

[RBrodzinsky]

OK, a little more data on my experiment (just wish I could test the new trucks).  I found a really cool little electronic balance, for all of $12 on Amazon. 0-500g range (approx 1 lb) with 0.01g readout.   Seems to be fairly accurate with high precision (repeat ability).    I measured the mass (weight) of each of the cars, and also the velocity of the car, using my Accutrack II speedometer, at the point the car hits the bottom of the ramp, and starts across the flat.  This is the point where there is no additional acceleration due to gravity.

I also converted units into metric, for anyone interested in doing further calculations.  Distance traveled is from the first experiment, but the cars were all behaving the same for this retest.

It is interesting to note that in addition to the inside roller bearings, the Athearn cars are significantly heavier.

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Items of note:
(1) on the Amfleet Cafe, I tried replacing the trucks with the spare pair I ordered from Kato.  Car would barely move (and yes, I checked for everything I could think of).  When I replaced the originals, it actually rolled a bit better (exit velocity was measured prior to my playing with trucks)
(2)  When I added the decoder and extra lighting to the Kato Cab Car, I also added extra weight, hence the difference between 4024 and 3860

[CNR5529]

So its been a few weeks since last checking in with the somewhat improved BiLevel trucks, and I spoke of a version 2.0. Got a bit swamped with the day job, as well as other projects, but here is what I have been working on so far.

The idea was to do away with the bushings and associated misalignment issues, reduce contact area thus reducing friction, and generally simplify assembly. In this case, the truck frame has a series of holes pre-drilled in specific locations.

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These holes will allow for thin brass/steel/material of choice wire to be installed and act as very small load bearing surfaces. The horizontal wires will provide single point contact on the top of the axles, while the vertical wires have 0.0005" clearance (0.001" total clearance) for longitudinal play. Only one vertical wire should make contact with the axle at a time at each axlebox. The total contact area for the entire car is now reduced to 16 single points of contact (ok ok, not really if you consider actual hertzian contact theory, but we are talking microscopic contact areas), and I see no way to get less. Slight misalignment should not be problematic, as the wheelsets would still only make single point contact on each wire.

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The idea will be to simply glue the wires in place, trim to length, install wheelsets, and off you go. I still need to put in an upstop/wheelset retention method, which might just be a retention wire under the axle or a bit of a plastic protrusion to snap the wheelset in. I will also add the lateral bosses similar to what @Lemosteam had sketched out previously. After that, these will go to the printers for testing!

At this point I anticipate that electrical pick up will be completely unreliable, so the bushing trucks might still be necessary for electrified cab cars, but we will see during the next round of testing.

Oh, and just for clarification @peteski, I hid the plastic axle tubes in these screenshots to make it easier to see, but they still hold the wheelset spacing as before. 

[peteski]

Oh, and just for clarification @peteski, I hid the plastic axle tubes in these screenshots to make it easier to see, but they still hold the wheelset spacing as before. 

Oh come on - I'm not that bad!   
I'll be curious how these roll and how close the tolerances are between the design and printed item.

[craigolio1]

I love this idea. Having been the poor SOB that assembled, aligned, installed, and realigned the test trucks on the 7 car train, (which took HOURS!) I look forward to this much simpler installation procedure.

In the event that this works and the bushings ARE required for reliable power pick up, I have 6 sets of assembled trucks for sale for those who want powered cab cars, haha. (Seriously though. Just the cost of the parts.)

Thanks so much for the effort in design version 2.0!

Craig

[RBrodzinsky]

Craig - if this works, count me in for 2 sets of trucks with the bushings -- 2 cab cars = 4 trucks.

[peteski]

I love this idea. Having been the poor SOB that assembled, aligned, installed, and realigned the test trucks on the 7 car train, (which took HOURS!) I look forward to this much simpler installation procedure.

In the event that this works and the bushings ARE required for reliable power pick up, I have 6 sets of assembled trucks for sale for those who want powered cab cars, haha. (Seriously though. Just the cost of the parts.)

Thanks so much for the effort in design version 2.0!

Craig

I suspect that the electric pickup will be good on the revised truck. Since the contact area between the axle and one of the small-diameter wires is very small, the pressure at the contact area should be more grams per square millimeter than with the brass bushings.  That seems like it'll actually improve the electrical contact.  This desing is very innovative and "outside of the box". I hope that it shows a large improvement of the rolling ability.