Replacement Athearn Bombardier BiLevel Trucks, aka making the train roll

[CNR5529]

As most of you know, the Athearn Bombardier BiLevel commuter cars are great looking models, which suffer the same problem as most other coaches with inside bearing truck, such as Amfleets: they dont roll particularly well. A friend best described these cars as rolling marginally better than a sack of hammers. This topic has been previously discussed here https://www.therailwire.net/forum/index.php?topic=39533.msg483403#msg483403, and a practical solution was presented for Amfleets here https://www.therailwire.net/forum/index.php?topic=39504.30 using miniature bearings.

The inside bearing trucks as designed cause a lot of rolling resistance, and I believe this is caused by two factors: the internal friction of truck clips holding the wheelsets, and the truck mounted couplers and excessive lateral play of the wheelsets causing the back of the wheels to rub on the truck frames in curves. This means that longer trains such as those typical of transit authorities such as GO Transit, with up to 12 cars pulled by a single locomotive, are not practically possible in miniature.

Using the bushings proposed by @mmagliaro in the previous thread, as well as accurate reference material, I was able to redesign a truck from the ground up for 3D printing, to replace the original trucks.

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This conversion reuses the original wheelsets, and will require body mounted couplers as well as the bushings in question. Test prints have been ordered from Shapeways, and will be tested on a 7 car trainset once the conversion is complete. I hope to be able to report operational and aesthetic improvements in the near future!

[ryan_wilkerson]

Interesting project!

[peteski]

The key to decreasing rolling friction is the minimize the contact area between the axle and the bearing.  Kato so far is the leader by using 1mm dia. steel axles and copper bearing plates with a very small contact area in the bearing.

Your design appears to use rather large diameter axles and bearings. I don't see how that will roll much better than the stock trucks.  I think that using Kato wheels/bearings in your design would dramatically decrease the rolling friction.  But if course that would be quite expensive.

[railnerd]

Very interested as well.

[CNR5529]

@peteski Keep in mind that the stock athearn axle is 1.2 mm in diameter, vs the kato axle that is only marginally smaller at 1mm in diameter. What you see there as the "large axle" is the O.D. of the bushings, as well as the plastic tube used to isolate the two wheels and split axle. The actual axle is inside the bushings and tube.

Either way, testing will show if this is better or not than the stock truck. If it is, I'll make these available. If not, then no harm done trying to improve something that we can both agree is already a poor performer. 

[Loren Perry]

This reminds me of  similar problem I dealt with back in the 1990's when I built a detailed car-for-car replica of an Amtrak San Diegan I rode on when I was a member of the Belmont Shore Lines Model Railroad Club in San Pedro, CA.

All we had then was a choice of Model Power and Life-Like (my ultimate choice) F-40PH's and the Bachmann Amfleet 1 cars.

I rebuilt the F-40PH with an N-scale of Nevada replacement metal chassis and did some serious surgery to rebuild one Amfleet coach into a Food Service Cafe car and a second coach as a cab control car.

Finally, I had to do something about those horrible trucks. The rebuilt (and now heavier) locomotive could only move three cars on a straight and level track.

I ended up discarding the cars' wheels and axles and then cutting off the ends of the plastic truck frames. Next, I acquired a bunch of Micro-Trains "pizza cutter" wheel sets (I had plenty as I had been converting my entire fleet of cars to Micro's low-profile 1008 wheels.) Two reason for this: the Pizza Cutters had thinner and more true-running Delrin axles which minimized friction, and 2. the deeper flanges would help keep the cars on the rails during extended high-speed running in "push mode".

To hold the axles to the truck frames, I made short bearing boxes from precisely cut lengths of C-shaped styrene and cemented them to the ends of Bachmann's plastic central truck frame components while trapping a wheel set inside the bearing box. I had to make a simple alignment jig to ensure all the axles were parallel to each other as well as perfectly perpendicular to the bolster pin hole. NOTE: The cab control car didn't need any of this as it rides on conventional drop-equalizer outside bearing trucks.

The end result is a very smooth rolling eight car 1990's vintage Amtrak train that allows me to go up 2% grades with a single F-40PH, exactly as used on the prototype: five coaches (including one business class car), one food service cafe car, one cab control car, and one short baggage car with single centrally located doors on both sides which I semi-scratchbuilt using Con-Cor car body components as a starting point. The baggage car rides on conventional outside-bearing trucks like the cab car, so only a total of six cars use inside bearing trucks.

I ran this train in both push and pull modes many times as a member of the BSMRR club and still have the train today.

[peteski]

@peteski Keep in mind that the stock athearn axle is 1.2 mm in diameter, vs the kato axle that is only marginally smaller at 1mm in diameter. What you see there as the "large axle" is the O.D. of the bushings, as well as the plastic tube used to isolate the two wheels and split axle. The actual axle is inside the bushings and tube.

Either way, testing will show if this is better or not than the stock truck. If it is, I'll make these available. If not, then no harm done trying to improve something that we can both agree is already a poor performer. 

If you made the bushings (or whatever the axle is rotating in) about 0.5mm wide or less (instead of how wide they are now) that would decrease the contact area and the friction.  I was thinking of etching the bearings out of thin (0.005") stainless steel or brass to minimize the contact area.

[jagged ben]

Following!

[craigolio1]

Hello all. I'm the person that brought this to Fredrick, and boy am I glad I did. First off the design is incredible and even if it rolls the same as the Athearn car, it will look wayyyy better so it's a win no matter what.

My train is seven cars so we'll be using it as a test bed. I plan to body mount 1015s.

I'll start by converting one car to the new trucks. I'll set up an incline with two identical lengths of track. Testing will simply be to set them both rolling down the incline and onto a flat. The car that rolls the farthest obviously had a lower coefficient of friction.

These are the bushings I ordered, and that Fredrick based the design on:

http://timesavers.com/i-9605176-13-bergeon-style-american-made-bronze-bushing-20-pack.html

I measure the axles on several trucks and found they were all around 1.2mm and so we settled on a 1.25mm bushing for a clearance fit. When they arrived I test fit them and they slipped right on.

They almost fit without modifying the axle tube as you can see here, compared to a Fox Valley wheelset:



Once I knew they fit I used a precision Dairy Caliper to grip the bushing and roll the truck. It was extremely free rolling, albeit with no weight of any kind and being pushed by a giant hand.



I'm really looking forward to further testing on these once they arrive.

Thanks again for your effort Fredrick. They look amazing.

Craig

[peteski]

I'm very curious about the results.
I agree that the truck design looks very good, as you said, much better than the original trucks.

[nkalanaga]

The 1960s Minitrix F units had "bearings" made from brass tubes, about as simple as they could get, and the dummy versions actually rolled fairly well.

Knowing nothing about these cars, my biggest concern would be whether there is enough side play for the wheels, or the center tube, to rub on the sides of the bushing.  If so, that would be a major source of friction, and could cancel any benefits from the better bearings.

[CNR5529]

First off the design is incredible and even if it rolls the same as the Athearn car, it will look wayyyy better so it's a win no matter what.

Thanks! Indeed, accuracy of the truck was a big part of this exercise for me personally. It helps when one works with some of the guys that designed the original 1:1 truck... So far they are impressed with the CAD renders! Another requirement Craig and I agreed on early on was the need to develop lower rolling resistance using parts that are available to everyone. I cant design a truck, make it available through shapeways, and expect everyone who buys it to machine their own custom bushings, or etch brass pickup tabs like what Kato has done, its just not realistic. Many modelers/operators/collectors wouldn't have the equipment or the skillset to do this. That is why we settled on these tiny brass bronze bushings. Again, testing will either confirm any improvement or show that it was waste of my time. So far though, we both are confident that there will be an improvement.

Knowing nothing about these cars, my biggest concern would be whether there is enough side play for the wheels, or the center tube, to rub on the sides of the bushing.  If so, that would be a major source of friction, and could cancel any benefits from the better bearings.

I completely agree with this, and will show you how we are addressing it in a minute. Part of the design philosophy here is maintaining tighter lateral play tolerances. I believe that a secondary source of the friction in the original truck was from excessive side to side "slop". As forces in the couplers made the truck pivot (particularly while curving), this slop caused one wheelset to move sideways to the left and the other to move sideways to the right, until both wheels were rubbing against the frame, and angling excessively. In railway vehicle dynamics jargon, we say that there is excessive angle of attack. By removing the truck mounted coupler, and ensuring that the wheels cannot touch the frame directly (only metal on metal contact with the side wall of the bushing), we hope to eliminate the second source of friction altogether. To ensure that there is no contact with the center tube, I designed an assembly jig to help modelers with wheelset refurbishment:

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First, trim the axle tube so that it fits between the mounting fingers (go/nogo). Next, mount the bushings on each stub axle, and press the stub axles on the axle tube. press until the wheels make contact with the outside of the jig mounting fingers. At this point, the wheels will be perfectly in gauge, and there will be enough built in clearance with the bushings and tube. As an added bonus, I included a drill template on the back of the jig to drill the new coupler mounting screw hole. This jig will be included with replacement truck sets.

[Dksw]

I am gunning to have two operating GO Transit L10 set-ups on my layout.  There will be a helix with a 1.5% grade.  Smooth rolling and all the extra weight I can add to a Kato MP36 will hopefully allow for it.

[RBrodzinsky]

Any thought for allowing electrical pickup?  I am in the starting phase of putting LED lights in a cab-car of these units  (headlight & flashing ditch,  red rear class lights). I have the Streamlined Backshop Wheel Wiper kit for use with the standard trucks, but if these trucks pan out, would love to improve the overall performance.

[peteski]

Any thought for allowing electrical pickup?  I am in the starting phase of putting LED lights in a cab-car of these units  (headlight & flashing ditch,  red rear class lights). I have the Streamlined Backshop Wheel Wiper kit for use with the standard trucks, but if these trucks pan out, would love to improve the overall performance.

Pickups which rub against the wheel backs increase friction. But making the brass bushings/bearings into electrical pickups should do the trick without increasing friction.