Large Scale Central

Repairing USA Trains split axles

Modeling Rolling stock
#1

There seems to be an outbreak of cracked axles lately in early run USAT dismals. I thought a rerun of how to permanently fix the problem might be in order. So here is the sequence of pix on how to permanently repair the USA splitting axles I first published around June 2004. Gordon Watson turned up the brass sleeves for me and I still have them available. Until then I had removed the metal axles, closed the cracks in the plastic part with a clamp and then bound the plastic part with cotton thread which was soaked in Cyanoacrylate. Then the metal parts were pressed back into the plastic. The title of the jpg file should also help explain how to do it.

#2

Excellant info Tony, good pix too!

#3

I even had clean fingernails too.

#4

For my part , Aristo could engineer direct replacement [ easy swap out ] power trucks , with no traction tires , less amperage draw , and the plus of ball bearings . And then most of your diesels would be about the same speed . Just a thought …

#5

and, since these are basically the same motors, and other than color, same gears as early Aristo units…

I can tell you someone who found this contacted the importer, who initially did not believe it (seems to be pretty common), until they checked, and found for a short period of time the Manufacturer (factory in PRC) had changed one spec…either size of gear or size of axle…

Fixed it.

None of the newer units have exhibited this so far.

Plus, there seems to ba a ball-bearing that replaces the journal bushing in the truck…

#6

Now here’s a prime example of what I have been on about .
No whingeing about the manufacturer , just plain honest to goodness technical dissertation on how to sort it .
Makes good reading ,and doesn’t sound in the least negative .
Nice little post .
Mike

#7

Yeah, well, if I told you who it was who contacted the importer it would be “Katy bar the door!”

#8

Yeah , but you wouldn’t tell , would you Dave ? And spoil a good story ? Nah .
Mike M

#9

TOC do the 2 mfrs power trucks draw the same amperage ? I had previously belived that USA trucks/motors had a higher amp draw ? I mean now …this years power trucks ? Thanks

#10

Mike.

I would consider replacing the USA Trains two axle power trucks with two axle AC BB power trucks as I hate tyred drivers and the AC trucks have a sort of three point suspension.
I believe the regular un rubber tyred RS-3 to be the smoothest running 1:29 diesel loco of them all.

Under no circumstances would I consider swapping out the USA Trains 3 axle trucks, which in my opinion suck with that god awful articulated front gearbox, with the 3 axle AC trucks, as in every example I have seen they draw more current and are nowhere near as smooth as the USAT 3 axle trucks.
That means the LS’er wanting big power is stuck between the devil and the deep blue sea.

Dennis, I am well aware of the claims that USAT motor blocks draw high currents.
I do not believe it, as ever since I have been making them I have fitted my 3 amp R/C controllers in both AC and USAT locos with two axle blocks and have never had an overload in either.
I have done many dozens as have TOC and Don.
I cannot understand why it is necessary to fit 5 amp DCC decoders in the same locos. Unless of course the claims of the power handling capabilities of DCC decoders are somewhat overestimated.
RCS power ratings are for continuous draw, not just for the first cycle of the DCC pwm.

#11

I think the USAT high amperage story comes from the GP7 and George Schreyer’s posts and web site. He measured and published an abnormally high current draw when the GP7 was at full stall.

I have the F3’s and their stall current is nowhere near the GP7 data George published.

Next, in the evolution of the story, NCE stated that they would not guarantee any decoder in any USAT loco unless it was the D808 (8 amp continuous, 30 amp stall).

I don’t have a GP7 (yet, ebaying as we speak)… but will measure it.

While I highly respect George, I have yet to meet someone who operates at full stall. If the loco won’t pull the train, most people stop and add a loco, or shorten the train.

George’s idea is to bulletproof the DCC installation is a wise one, but classifying all the USAT locos by the unique motor in the GP7/9 is not right, but I believe this is how the story started.

A 5 amp decoder should be fine.

(Now that said, I went with D808’s myself, the extra cost was cheap insurance to me)

But when the LS Soundtraxx Tsunami’s come out, if all I can get is 4 amp ones, those I will buy.

Regards, Greg

#12

If I recall, talking to George, his idea of full stall was vicse-grips on the wheels.

I recall his 8 amps on the SD-40…and a certain PolkFolk claiming their new patented units sipped power…until the day they hit the shelves and it was modified to “patent pending” and the “sips power” just faded away.
George got 7 amps out of the 45, if I recall.

The GP7-9, GP-38, GP-30, F-3, and whatever other Blomberg truck units are all exactly the same.

Motors, gears, sideframes, wheels (newest ones have no traction tires at all), mounts, the works.

With sound and lights and load, 2 amps is about max.

#13

Revisiting George’s site to be sure I quoted right, he has a table of stall currents:

http://www.girr.org/girr/tips/tips4/tractive_effort_tests.html

I remembered correctly, the GP-7/9 was the top. It spiked to 8 amps just starting, full stall current was over 10 amps, and he notes (note #3 on the bottom of the page) that 10 amps was all his power supply would put out.

On the GP=7/9 page he further comments: "Measured right at the motor, the stall current is 15 amps per motor, beyond the capability of almost all currently manufactured DCC decoder. "

His measurement of the SD-45 was 8.8 volts, but he notes he was afraid to use more restraining force. His test for full stall was “The engine was prevented from moving by physically restraining it as the power system was set to full power (18 volts on the track) and the current was measured to the nearest 0.1 amp.”

No mention of vise grips.

Also, I believe the SD7/9 was released earlier than the SD-45, thus my theory of the beginning of the story.

Regards, Greg

#14

Greg,
With respect, what you need to remember is that George was paid by AC to write about the TE around that time which means quite possibly he had a vested interest in AC.
I always wonder about credibility in those circumstances.
Plus, you need to remember that George has not updated his website for … how many years?
I sent him a motor out of an F3-B that I know would only pull a couple of amps fully stalled. He rated it at about 13 amps.
I have been doing this since before USA Trains or AristoCraft got involved in Large Scale.
It never ceases to amaze me how these urban myths get started as soon as competition for market share comes to a market.

Greg Elmassian said:
His measurement of the SD-45 was 8.8 volts,

Also, I believe the SD7/9 was released earlier than the SD-45, thus my theory of the beginning of the story.

Regards, Greg


I think you mean 8.8 amps, which is possible although I doubt it, and GP-7/9 not SD-7/9.

#15

You’re right… amps not volts…oops!

Yep, when I started, did a lot of reading before buying anything, and it’s amazing how some information can get transmogrified … (cool word)

The current ratings amazed me, but I dismissed the full stall currents because I knew I would never go there.

When I finally bought a rampmeter and spent some time watching it on my DCC setup, I felt a lot better, and the numbers were more in line with what I would expect.

I did not know about the relationship between George and AC, interesting… I was surprised to see the extent of his writeup of it on his site, but so little on other types of power, especially since it seemed he was going to DCC.

The question of rating DCC decoders, and measuring motor current is a tough one, at best an inexact science. What strikes me as funny is the wide variation in the size of heat sinks I see on these. There is a brand with a huge heatsink, which seems to have a lower current rating than another with much less cooling.

From my physics background, power is power, and if you have to dissipate X watts, then you have to have a certain amount of heat sink surface. There is no real magic to getting rid of heat if you have a passive heat sink.

Interesting stuff, and I’m still learning something new every day. Decoding these myths is fun in a way though. You should see what kind of arguments I get into when I say nicads have no memory effect, it’s usually a poor charging situation that causes the diminished discharge capacity. When I start talking conductive dendrites I usually lose my audience!

Regards, Greg

#16

Thanks for the correct info guys .
Myth busters …you are .

#17

Dennis,

In respect to an earlier post you made in this string about Aristo Craft making a direct replacment for the USA trains motor blocks I do look for that to ever happen. However with some modifcations the Aristo Craft Ball Bearing motor block can be made to fit the USA Trains Geeps. I am in the process of doing one right now and will do two more later. This is not being done because their is anything wrong with the USA trains motor blocks, far from it, they are going to a friend who works for USA trains and will use them to do some repairs to locomotives that he uses on a Christmas display that runs 12 hours a day outdoors in all kinds of weather. I am doing this to get rid of the tires, and so that I can add about one and a half pounds of extra weight. Both the added weight and the extra height with the bigger wheels will allow me to use these three locomotives on my layout where before I was poping off the stirpus every time I went trough a turnout or cross over.

There are sseveral reasons that the Aristo Craft two (2) axel motor blocks will not act as a direct replacement to the USA Trains GP’s. First of all the axel spacing is off by about 2/32th of an inch, the Aristo Craft Wheel spacing being longer. The second is the Aristo Craft Wheels are bigger, which require the brake shoes to be ground down on the USA side frames so that the weels will fit in. Other than that they will work you have to master the wireing and modify the USA trains locomotive to use the Aristo Craft wireing harnees (recomended) so that you can remove or replace the AC blocks.

The Three axle blocs are a little more complex to do, the wheel spacing is the same but the AC motor blocks do not have axels that go into the side frames. I have designed a screw that will allow the the two axle blocks to be retro fit into AC two axel diesels without taking them appart and one and a half sets of those could be used to make a direct replacement of the three axle motor blocks.

Tony is to be commended on his approach to the helical gear problem, I faced this about seven years ago with several Bachmann Columbia locomotives that belonged to an older friend four out of four had split and I recomended a simular fix with about the same results, my fix involved a thinner sleve but was going in the same direction. Tony’s fix looks more robust.

I honestly think that if all manufactures used Tony’s approach they could cut warranty repairs by 50% and motor block repairs by as much as 80%. The up side to this is that it would not add much more than two or three cents to the cost of the gear, but would do all but prevent the striping of the gear itself.

Ron