# USA Floppy Truck Change



## Bill Swindell (Jan 2, 2008)

I have always disliked the floppy axle that USA uses on their 6 wheel diesel trucks. Here are some pictures of how I changed it.

This is the motor block. The first and last axles were changed to eliminate the traqction tires and the axle that had no extensions.









I removed the existing bearing assemblies from the sideframes. Then, I drilled out the bearing from the back side with a 15/64 drill bit. Next, I drilled a 15/64 hole in a piece of .060 thich styrene. I glues this piece to the original bearing holder with epoxy glue as shown in the following picture.










The last part is fabricating the new bearing holder for the floppy axle.










The bearing block is maade with 3 pieces of .100 thick styrene glued together. I used .8" x .8" pieces of plastic for this. I then epoxied this piece to the side frame. You must make sure that these bearing blocks are lines up with the other 2 blocks and have the same spacing between the axles.

Ehne all was finished, I painted all of the new parts with flat black paint. 


The bearings that I used are 6mm x 3mm. The one problem with the bearings that I used is that they do not have metal balls. Therefore, they cna not be used for electrical pickup. If you run track power, you will need to find bearings with metal balls or just rely on the track slider for your electrical pickup.


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## NTCGRR (Jan 2, 2008)

Bill 
I did like Larry did


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## Bill Swindell (Jan 2, 2008)

That was the first attempt however, all of the wheels didn't touch the rail. Also, the ball bearings cut down on motor current. The other thing is that the pivot point on my trucks is now over the center axle. By adding the bearing in front, I can spread the engine weight among all of the axles.


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## Greg Elmassian (Jan 3, 2008)

And you can add more weight, I really like your idea of adding ball bearings to the USAT locos. 

I'm gonna have to do that.. 

Regards, Greg


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## Bill Swindell (Jan 2, 2008)

The first engine that I did the bearing thing to was my GP-9. I checked before and after. It reduced current draw bu 10%. By the tinme I add several pounds of batteries, the bearings really help.


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## NS37 (Jan 11, 2010)

what are the advantages of having the floppy axle to begin with? does this really make the turning radius so much tighter? what would you guess minimum turn is now? reason i ask all of this is i see that usa and dealers make a big warning that the sd40s can only go on 8'dia or higher. ive never used under 10' so i dont know.


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## Greg Elmassian (Jan 3, 2008)

Yep, that's the reason. Aristo solves their 3 axle problem by making gearboxes with a large amount of lateral motion on the axles. 

Regards, Greg


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## Torby (Jan 2, 2008)

We had a lot of trouble with our 3 axel USA's until we took the drive out of the floppy part. It's still floppy, but just rides along with the train. Since then, they run very nicely.


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## Greg Elmassian (Jan 3, 2008)

Funny, I have no problems at all, and have a number of them. I did dump the traction tires, and regauge the wheels to nmra standards. 

Regards, Greg


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## Nicholas Savatgy (Dec 17, 2008)

I have not had any issues with any of mine as well but they've never been run on anything less that 20ft dia curves. should they become an issue i will do as Marty did


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## Greg Elmassian (Jan 3, 2008)

It also may be that these trucks are more sensitive to abrupt vertical transitions.... I have also worked those kinks out of my trackwork. 

But, if I convert to ball bearings, might do exactly as Bill did. 

Regards, Greg


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## aceinspp (Jan 2, 2008)

So far I've not had problems with mine. I did as most and got rid of the traction tires. One thing they track well going through the AC wide radius turnouts. Later RJD


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## Bill Swindell (Jan 2, 2008)

I have no problems with mine either. I just don't like messing with the stupid think when putting the engine on the track. 

The other difference between my engine and your engines is that the bolster pivots on my trucks are over the center axle instead of being between axles 2 & 3. With this setup, the weight is carried by all three axles. In the original configuration, the axle carries no locomotive weight at all. It just goes along for the ride. I'm not even sure why thet bothered with driving the axle. My geuss is that this allows them to claim that all 6 axles are powered.


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## Greg Elmassian (Jan 3, 2008)

I'll bet you are right Bill! 

Have you checked what minimum radius or diameter your "rigid trucks" can handle? 

Regards, Greg


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## Bill Swindell (Jan 2, 2008)

I have to finish the battery installation before I really run it. I also have to fins a place to try tighter radaii.


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## Tom Lapointe (Jan 2, 2008)

This is a modification I've been considering myself for my USA Trains New Haven Alco PA's; I've had repeated problems with stripped idler gears







on them. I've already eliminated the traction tire axles in favor of plain ones (I'd rather have the drivers slip







than the gears strip!







). Removing the traction tires has meant that even with a pair of PA's pulling, I can't get my full 5-car New Haven streamliner set up my mainline's ruling 3% grade.







(Running it as a 4 car train - with a single coach behind my Aristo RS-3 as a "commuter" run







- did seem to help the gears last a bit longer, but I've still got one that managed to strip.







). Does NWSL (or anyone else) make a more robust replacement for the USAT idler gears







If I could get a beefier set of gears in the PA's trucks, I'd like to ballast them to make up for the lack of the traction tires (something which seems pointless to do currently with the existing gearing







).








Tom


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## aceinspp (Jan 2, 2008)

Tom : When replacing the wheels back in the block are you making sure the brass bearings are lined up correctly. If not this can be your problem for stripping the gear. I've run mine with no problems and have also removed the wheel sets with the traction tires and replaced with solid wheels. I've also added weight to mine and handle 15 car trains up my 1% grade. Later RJD


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## Torby (Jan 2, 2008)

"Funny, I have no problems at all, and have a number of them."

Well, you have to realize, any derailment at the Botanic is blamed on 3 axel trucks, even if there were none in the train


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## Greg Elmassian (Jan 3, 2008)

Old habits and old conclusions die hard, that is for sure. 

Tom, you could add some weight. Tom, when you replace the wheelsets, which way do you align the brass bushings on the axles... "flat" or "diamond"? (flat would be the flat surface parallel to the underside of the motor block, for example). 

Do you do the bearings differently between the "floppy axle" and the other two? 

Regards, Greg


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## Tom Lapointe (Jan 2, 2008)

Greg, I've tried to align the bushings with the "flats" parallel to the top of the truck when replacing the idler gears; I've also learned to be careful when putting the bottom covers back on as they tend to "move" around otherwise.







I usually run the loco back & forth a few feet on a test track before returning it to service; I had one instance where the bushing shifted out of position when the truck was reassembled







- it didn't cause the gear to strip then, but loaded the motor enough to blow a DCC decoder.







I have also removed the pickup "skates" on the trucks as they caused problems on a joint on an LGB bridge I have configured to lift up "drawbridge-style" for easy access inside of one of my elevated loops; removing the skates caused a pickup problem elsewhere where I had a pair of turnouts in a row (both LGB - an 18050 R5 followed by a 16050 R3). If I ran the curved route through the R5, the frog of the R3 immediately beyond (going *straight* through the R3 - the curved section of the R3 goes to my mining / logging branch, where I *don't *run the PA's), the space between the frogs coincided *exactly with the electrical pickup wheelbase of the PA's - causing first the lead loco, then the trailing one, to momentarily stall. *







Since this was before I had eliminated the traction tires, the *full weight of the following train (@ 100 lbs!) & the stalled unit would momentarily be thrown onto the other PA - further stressing the gears! *







My solution to the above was threefold: (1) eliminate the traction tires in favor of plain wheels to allow the loco to slip; (2) the sudden slack action sometimes caused the Kadees I had installed between the locos to uncouple, throwing the full train weight onto the trailing unit; I replaced the Kadees with a *solid drawbar; *(3) I installed an *"MU wiring harness" *







- a pair of Molex plugs connected to the pickups of both trucks. This allowed me to *parallel the pickup from both trucks for reliable pickup over the turnouts *(the Molex plugs exit out the rear doors of the PA's - when I want to run them, I first plug the two together electrically, then connect the drawbar). The Molex plugs are *nicely hidden by the diaphrams *between the two PA's.







These 3 modifications (& running 1 less car in the train) *vastly improved *the longevity of the idler gears - but the last time I ran the train a couple of months ago (after several hours of running), *I suddenly heard a telltale "whine" from the rear truck of the lead PA - & opened it find the idler adjacent to the fuel tank stripped. *







This is why I don't *dare *try to ballast the PA's with additional weight at present (there's certainly enough room inside them) - until I can find a way to make those truck gearboxes *"bulletproof". *







As a final note - I haven't had to *touch *the gears in the "floppy" end of the trucks, don't think they get loaded enough to strip. My curves are broad enough (69" minimum radius, Aristo 11.5 - foot diameter) that I could almost certainly eliminate the "floppy" motion of the truck without any tracking issues. Here's a YouTube clip of the train in operation shortly after I had initially converted it to DCC operation (& had to upgrade my power supply as a result!







), so you can get an idea exactly what my mainline is like:










*Tom*


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## aceinspp (Jan 2, 2008)

Tom one thing to do when working on the gear case and taking apart make sure you support the gear case as it drops down when removing the screws. I wedge two screw drivers between the gear block and the frame putting one on each side to support. This causes misalignment of the bushing when trying to reassemble the gear cover to the case. Later RJD


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## Greg Elmassian (Jan 3, 2008)

Tom, in a 3 axle USAT loco, ALL bushings go point up, not flat... I have read several sites where they say 2 axles are point up and the floppy one is flat... 

I took apart a number of brand new locos, and ALL were point up in the 3 axle ones, and "flat" in the 2 axle ones. 

If you put the floppy axle wrong, you will eventually strip the gears. 

I know many "expert sites" say different, but I personally opened ALL my USAT locos, so I am SURE... 

I would try doing the floppy axles point up from now on and see what your results are... 

Funny that you had the power pickup issue, I read what you wrote, but how you got all 4 axles on an insulated section seems almost impossible... but I try to only have "live frogs" on the main line, or very short ones... (all my #6 Aristos have been fixed with waterproof microswitches and Train-Li inserts) 

I use 4 screwdrivers, basically one under each corner of the motor block and wedge it up tight until I know for sure I have the cover all the way on and tightened down. With my 3.4% grade and long trains, I cannot mess this up! 

Regards, Greg


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## Tom Lapointe (Jan 2, 2008)

Greg, sorry for the delay in getting back to you, just been real busy







lately. Don't know if it was obvious in my original comments, but I've *never *disassembled the "floppy" axle gearboxes - the gears in them have held up!







The stripped gears in the "fixed" axles were originally noticed when I saw the PA's struggling upgrade which they had easily hauled the NH streamliner set up easily previously; looking closely, I had noticed some axles were *barely turning,* while others were *slipping!*







When I took the PA's off the track & turned them over, I found I was able to turn the wheels on the axles with stripped gears *easily by hand *







; those axles whose gears were intact were *not turnable by hand. *I've only disassembled the "fixed" gearboxes - am I correct in assuming that the bushings on those should be *"flat-side" down*







(As opposed to the "pointed-side" down you say the "floppy" axles should be







). The gears which stripped the most were on the axles equipped with the traction tires - which is why I replaced them with *plain-wheel *axles. Although the changes I've made have *improved the longevity *of the idler gears, it still hasn't eliminated their failure entirely- which is my *ultimate goal here. *It's a shame because the train really *wows the neighbors *







(especially running at night with the fully-lit interiors).








*Tom*


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## Bill Swindell (Jan 2, 2008)

Tom, I agree that there is practically no load on the floppy axle. The weight is all carried bu the 2 solid axles. If you are stripping the idler gears, you must either have a huge load on the drive train or something out of alignment within the motor block assembly.


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## Greg Elmassian (Jan 3, 2008)

There may be an additional facet to this question. 

Tom, all USAT locos have the propensity for "split axles"... and this might have been what you have also seen mixed in with gear problems. 

To test: lay the loco on it's back, and put your thumbs one each on a wheel on the SAME axle. If you can turn one wheel relative to it's "mate" on the other end of the same axle, you have this problem, where the gear no longer turns that "half axle". 

This is the first thing to check, it can seem like a stripped gear. 

Obviously if you open the gearbox and the gear is got a "half moon" carved out of the face, that is also bad! 

ALL bushings in 3 axle USAT locos are pointy side up/down, i.e. not with the flat surface parallel to the bottom of the motor housing... again, I have seen many "reputable" sites and people say otherwise... I have been very careful to observe this... Improper assembly can cause damaged gears right away or after a while. 

Also, when people remove the motor block bottom cover, if it's not very strongly supported from the rear, the axles can shift right away, and give people the wrong impression of the "right" way... I think that is part of the misunderstanding... 

I learned all of this the hard way with cracked gears, chewed up gears, etc. Now everything works great, although I got sloppy recently and put one together wrong, I got fat-headed and did not support the motor block while installing the cover, and an axle slipped out of place (the bushing turned). Did not follow my own admonitions! 

Regards, Greg


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## aceinspp (Jan 2, 2008)

Till I learned of the trick to support the gear case when dismantling and then putting back to gether and no knowing at the time that the wheel had slipped and turned the bushing caused me all kinds of head aches I always made sure the bushing is what I call the diamond edge up. You know right from the get go that when you put it on the track things just don't sound right. Later RJD


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