Replacement Athearn Bombardier BiLevel Trucks, aka making the train roll

[nscalbitz]

I suspect that the electric pickup will be ....
 This design is very innovative and "out of the box". I hope that it shows a large improvement of the rolling ability.

Pedants alive! 
"out of the box" would be the same...  "outside of the box" would be different = innovative. 

Heh, so many munged metaphors from  , musta been a heavy weekend!
Regards Dave

[peteski]

Pedants alive! 
"out of the box" would be the same...  "outside of the box" would be different = innovative. 

Heh, so many munged metaphors from  , musta been a heavy weekend!
Regards Dave

Part of it is my Polish heritage, and part of is inattention after a brain-melting 8-hour class.  Is that good enough of an excuse? Give me a break - I only missed 4 letters. 
Don't let the sleeping dogs bite, eh? 

[craigolio1]

It would be awesome if the new design provides good electrical pickup.

The bronze bushings worked well but did exhibit random drop outs. A keep alive would be needed, but I suspect we might see the same with the new design. You see it with Kato cars and they are what I consider to be the gold standard in passenger car trucks.

The holy grail here is electrical pick up AND better rolling.


Looking forward to testing the new design.

 Craig

[nkalanaga]

Powdered graphite in the bushings?  or maybe Conductalube?

[Lemosteam]

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. 

Cool!

I realize you are still in progress on this design so I have some thoughts.

How will you trap the axle from falling out now?  I would not bend the wires over to trap the axle as it will close off your 0.005" gap in a hurry.

It might be good to design a 5-10% snap into the slot and leave the wires vertical, and with the extra material you could add a downward stop with a small pocket for the wires to prevent the loose wire ends from moving toward the axles, which I would bend in an inverted U first before insertion. 

if the top wire is the electrical contact, I assume there is a way to connect to it somewhere in the truck?

Since the top wire would likely be phosphor bronze, would it make sense to have a side view parabolic curvature or gentle radius to force (under the weight of the car) the axle up and toward the four center wires (toward thew bolster center) for improved electrical contact?  I realize this will double your friction but it may be a reasonable trade-off.

Enjoying this progression of design!

[craigolio1]

The road testing of the train was done with graphite on the bushings.  I graphite spray was apppied prior to assembly.

Craig

[nkalanaga]

Craig:  You're ahead of me!  So much for that idea...

[RBrodzinsky]

@craigolio1 , @CNR5529  -- just bumping this thread; wondering if there has been any new progress with the new design?

[narrowminded]

I don't think this will ever be perfect but I do think something with reasonably reliable pickup could be made and it might be able to be done as a mod to the existing truck.  At least for prototyping.  I've acquired pretty extensive experience with this issue working on my miniature power trucks and have a few approaches that might be able to be adapted.  If somebody has a truck or two that I could look at I would be willing to give it a try.  Keep in mind though, in these ventures and in short quantities, ultimately cost can be an issue.

[CNR5529]

@craigolio1 , @CNR5529  -- just bumping this thread; wondering if there has been any new progress with the new design?

The latest test prints should be here any day! I will then set up a test ramp to compare a stock car against rev 1 and rev 2 of the new truck design. Should be able to report on this very soon.

[CNR5529]

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These are soaking in bestine as we speak. You can see the channels for the wire bearings, as well as how the wheels will be retained (snap in place). I just hope the printing tolerances are good enough...

[Lemosteam]

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These are soaking in bestine as we speak. You can see the channels for the wire bearings, as well as how the wheels will be retained (snap in place). I just hope the printing tolerances are good enough...

Suggestion, while soaking, snip off a piece of wire that you plan to use in the channels at a high angle and using a pin vise to gently rotate the wire like a drill to clean out the wax that I know is in those holes.

Will make your final assembly much easier.

Might want to re-soak after the wire is in, to clean off any wax transferred to the wire as you are feeding it into the holes.

[craigolio1]

This is awesome. I can't wait get moving on this again. It was really exciting the first time.

Craig

[CNR5529]

So an update is long overdue... I had assembled the trucks and conducted testing right before Christmas, but unforeseen circumstances kept me otherwise occupied and I wasn't able to write up a summary of my findings. So without further delay, here it goes!

After the bestine soak, installation of the bearing wires proceeded fairly uneventfully. I tried trimming the wire with a high angle per Lemosteam's suggestion, in order to "drill" out the holes. What I found however was that it tended to force the wire out of the channels in the openings, which in turn pinched the axles. When I cut the wires flush, and inserted them straight in (think pressing rather than twisting), the wire cleaned out the channel seats much more effectively, and the longitudinal axle bearing tolerance was restored.

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It was then a mater of snipping off the excess wire and snapping in the wheelsets. (Though the excess wire was not yet trimmed in this photo)

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As is, the truck is now extremely free rolling. If I set it down on my desk, which apparently has the slightest grade, it rolls away on me without needing a push to break friction. That's a step in the right direction!

Next, I assembled a test rig, with dimensional parameters similar to that of @RBrodzinsky 's rig.

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Tests were conducted with the rev 1 truck, the rev 2 truck and a stock car to act as a control and compare to previous test results. I also repeated the tests with the trucks by themselves, and assembled to the vehicles. This shows the influence of carbody weight on the various truck designs. So how did we do? Well here is some data:

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So what does this all mean? Well, generally speaking, Rev 1 trucks are better than stock, and Rev 2 trucks are better than Rev 1 trucks when considering distance traveled. In total, the rev 2 truck traveled almost 45% further than the stock truck. When the carbody was installed, the added weight did cause more friction to occur, and the end result is we have a vehicle with inboard bearing trucks which is now closer in performance to the Kato Amfleet Coach. Keep in mind I have yet to test the effects of lubricants on the Rev 2 truck.

One big improvement to the Rev 2 truck was a much reduced tuning time. It took Craig and myself quite a bit of time and effort to tune and align all the bushings in the Rev 1 truck for his train. In this updated version, it was a bit more work to thread the wires initially, but once this was done there was no need for optimizing or tuning. Also, if the installation was not done correctly (i.e. the wires aren't seated correctly or there is some print fuzz left), you know right away because the axles are not free to move.

On a level layout with fairly broad curves, we were able to haul a 7 car consist with the Rev 1 trucks using a single locomotive. Adding an 8th car would cause slipping to occur in the curves. I am guesstimating that the rev 2 truck should bring us closer to the 9-10 car mark, but this has yet to be tested.

Contact between the truck frame and axle has now been reduced to 2 points of contact at each journal, so I see no way of further optimizing the truck design. At this point the only way I see to get better performance would be to make the cars lighter. I am looking forward to testing out a complete trainset in the near future!

[RBrodzinsky]

Great work, and nice writeup!