Atlas SD35 Truck Frames Riding LOW!

[busdriver]

Hey all,

I have purchased a couple of the Atlas SD35s.  These are the latest ones with ESU DCC/Sound.  Being an SP fan, I like having all of the models since they would throw anything that runs into a consist to get a train down the line. 

I'm having an unfortunate problem of the bottom of the truck frames hitting switch machines on my layout.  The switches are all Atlas Code 80 switches of various vintages.  Even the latest version will cause a hit and halt the engine in its tracks (no pun intended). 

I'm attaching photos of the SD35 and an SD9 to show the difference.  I also notice that the SD35 has a very tall bolster that makes the body ride high compared to what seems right and the SD9.  I'm less concerned about that, but wanted to put it out there as well.  It actually causes the coupler height to be a bit high so I had to shim the coupler on the end pulling the train to bring it down.

Any ideas on how to address the truck frame riding low issue?  Grind off those little tabs below each axle?  Those seem to be the biggest culprit for catching trackside equipment.  I did verify that the truck frames are completely and fully snapped onto the truck body. 

Thanks.

Bryce

[Olivani]

That truck frame looks like it is not attached to the gear tower at all. If you look at the truck from the underside, can you see the gears on the axles ? If you can't click it on and you can't see the gears, check if the gear tower is the wrong way around in the chassis. Can you lay the loco on it's roof and take a picture from the truck and post it ?

[busdriver]

Olivani,

I agree that is what it looks like, but they are fully clicked in.  They changed the design of the truck relative to others I have seen where the tower is much taller, and the frames are really low relative to the axles.  Here are the pics of the underside.  Both locomotives are exactly the same and catch on things.

Bryce

[sizemore]

SD-35's look like they ride high by nature since the walkway is thinner than first and second generation GP/SD counterparts. But that does still look "to low". The SD7/9 and SD-35 trucks from Atlas are interchangeable, may consider temporarily swapping them to see if the appearance changes much. Then inspect the SD-35 trucks, there may be an assembly issue where the side frames bow out when looking head on to the truck, caused by the wiper cups not seated in the truck frame recesses. This lends to the truck appearing "lower" than normal.

HTH
The S.

[peteski]

I wonder if the axles are too short and they ride high in the axle cups, causing the truck to sit low.  You can check if that's the case by holding the model upright in the air and gently pushing up on the wheels. If they move up quite a bit, then that might be the problem.

[busdriver]

Thanks Peteski and Sizmore.  I will double check all of those things.  I'll also see if there is an SD 9 that I can borrow trucks from for testing.  My initial look last night seemed to show that the trucks are oriented differently relative to the brake shoes, so I'm not sure they will clear the pilot if swapped.  However, I think I was comparing to an older generation of SD9 (not the ESU version with the wired pickups).  I'll look at one of the most recent SD9s.

Bryce

[Rasputen]

I would disassemble one and inspect how the bronze pickup strips are located to the truck centers.  On my friend's IM FT units which I think use Atlas truck innards, there are some very tiny pins molded on the truck centers that the bronze pickups are supposed to be located on.  The pickups were originally glued to the truck centers, but if the truck is disassembled or too much downward force has been put on the locomotive, it can disengage the pickups from the tiny plastic pins.  The tell tale sign is the large gap between the bent part of the bronze pickup and the top of the sideframe which I can see in your images.  On the IM FT there is not enough material in the truck center to put a threaded fastener there to hold them.  I thought about putting a .020 steel pin through the whole thing to hold them together, but this would mean any future servicing would be even harder.  In the end I decided to carefully remove the factory glue residue from the truck center and the bronze pickup, and clean out the small hole in the pickup so that it can't slide off of the pin so easily.  On the FT, like a lot of other models, the sideframes snap on only at the ends of the trucks, but the ride height is controlled by how the bronze pickup is located.  I hope this makes sense, I don't think I took any photos.

[chessie system fan]

Yeah, by the look of things (I just got my own earlier run model out), these trucks haven't been redesigned.  I would remove the shell so that you don't accidentally damage it. And then disassemble the truck sideframes and put them back together.

[mu26aeh]

I just looked at one here at the shop and there is almost zero reveal of the wheel face, whereas other atlas units you can see some face

[turbowhiz]

Almost looks like the wheels could be undersize?

[busdriver]

Mu26aeh, thanks for looking at yours at the shop.  I think they are all this way.  I bought 2 different ones from 2 different places, and they all look this way. 

I will take one apart to see if anything strange is going on in there.  I kind of hope there is, but I doubt I will be that lucky.  I did measure the wheel diameter relative to an SD9, and they were the same.

I'll study it and get back....thanks to everyone!

Bryce

[busdriver]

Well, unfortunately, this issue is "by design."  There were no issues with the way the trucks were assembled.  Everything was aligned and where it was supposed to be. 




The truck tower/gearbox is very different between an SD9 and SD35.  In this picture the SD35 is on the left.  This explains why the engine chassis rides higher.  I tried putting the SD9 gear tower in the SD35, but it does not fit right and will not allow the truck to turn.




In looking at all of the parts, there are two reasons that the truck frames ride low to the rail.  The first is that the axle holes in the gear tower go up higher into the tower than the SD9 tower relative to the base of the tower.  That allows the wheels to be further recessed up into the truck/truck frame.




The second reason is that the truck frame sides are not flush with the base of the truck frame like the SD9.  This effectively lowers the sides relative to the wheels.  Here is the SD35 frame against a straight edge.



Here is the SD9 frame that is basically flush with the base.




The combination of these 2 factors make the truck frames ride just low enough to catch switch machines.  My solution turns out to be grinding off the tiny little nubs that are below each axle.  Those are the low points and would catch.  I am happy to report that by making that small adjustment that the locomotives now go around the layout with no issues.  Fortunately, when the locos are on the layout, you would never have any way to see/notice that those little nubs are gone......



Thanks to everyone for the ideas and information that gave me the confidence to determine that all was put together properly and find the solution of grinding off the tabs.

Bryce

[GGNInNScale]

Hi  I have a lot of Atlas switches of various ages.  A couple of the older ones have a higher "bump" on the switch motor top casing.  I take an emery board and just sand off a bit of the top cover until it no longer interferes with the sideframes.  Bevel it a bit so if there is interference, the diesel will slide over.  Cannot see it from a foot away, works for my diesel fleet.
I had a plow on an Intermountain diesel that also fouled the switch cover.  I just filed it back until it cleared.  Again, cannot tell without a magnifier.

[martin station]

 Just wanted to pass along that I was watching a YouTube review on the new Atlas SD35 by the Marshell and Southern and he is having the same problem with the trucks riding low. You might want to check it out. Should be easy to find by typing in Marshall and Southern or Review Atlas SD35.
Ralph

[GaryHinshaw]

I believe this is the video Ralph refers to: