Atlas SD-7/9 Universal Troubles...

[sizemore]

I have an Atlas SD-7 with the tinsy-tiny universal pin on the motor shaft and cup on the worm end. It suffers from the pin coming loose on the motor shaft. Thinking the simplest fix is some lock-tite, while the more expensive fix might be switching it to SD-35 motor/worm with hex shafts on the motor end.

Thanks,
The S.

[kornellred]

The Atlas N Scale Century 628 and 630 locos have that tiny little press-fit fixture on the motor shafts that engage the universal shaft connecting to the worm shaft.  I have Century models but no SD7/9's, but I imagine their drive systems are the same or similar.
What I do with the Century models is dispose of that press-fit fixture on the motor shafts, then, using a drill press, carefully drill through the flywheels as close to the ends of the motor shafts as possible with a small diameter bit.  Then, insert a brass or other metal rod of the appropriate size through the holes you drilled.  The holes you drilled must be exactly perpendicular to the motor shaft.  The universal shaft from the worm assembly will engage the perpendicular rod you installed.  No more glued in or press-fit fixtures on the motor shafts.  Clean-up measures will become obvious.

[sizemore]

Thanks @kornellred! I found SD-35 guts from a frame donor. Not able to sleep I put the bits in the SD-7 and it works. Just need the SD-7/9 motor cradle, and the intermediate shaft. The shafts can be found on the Atlas website (while I have one) the issue then is finding the motor. I searched for a bit on the Atlas website but couldn't find one, only the newer stuff for sound equipped locos.

The S.

[martin station]

I had the exact problem with my one SD7 and removing the motor from the cradel one of the motor contacts to the lightboard broke off. I couldn't find another motor either so I removed the motor and worm gear and am using it as a dummy locomotive until I can find one.
Ralph

[woodchip]

This is an ongoing problem. I would not object to buying from Atlas a motor with a hex drive and the neccesary bits to convert the engines with this drive system. I get the world has moved on and they've changed the chassis design to accommodate sound but a bit of support for what seems to be a flawed design would be nice. 

[tehachapifan]

Does the recent release of SD9's still have this same universal setup as before?

[Lackawannae8]

I have an Atlas SD-7 with the tinsy-tiny universal pin on the motor shaft and cup on the worm end. It suffers from the pin coming loose on the motor shaft. Thinking the simplest fix is some lock-tite, while the more expensive fix might be switching it to SD-35 motor/worm with hex shafts on the motor end.

Thanks,
The S.

i clean surfaces with some 91% alcohol try to scuff up the ends then a dab of Gel super glue. hasnt failed me yet

[sizemore]

i clean surfaces with some 91% alcohol try to scuff up the ends then a dab of Gel super glue. hasnt failed me yet

I have two others SD-7/9's and a few 620's which haven't given up the ghost yet, so I am on the right path with Lock-Tite or Super-Glu gel.

Greatly appreciate it!
The S.

[sizemore]

Also in looking at the "new" DCC Motor and cradle, the can, cap and flywheels look to be identical to the "slow-speed" motors. May be able to switch the brush-caps and contacts from the "old" motor to make it work. Something else to consider.

The S.

[randgust]

I had my C630 crack the ball universals to the point where it just sat there spinning.

I can confirm that you can replace it all with the NWSL universals, steel shaft, ends, etc.   That hasn't failed.

[sizemore]

I can confirm that you can replace it all with the NWSL universals, steel shaft, ends, etc.   That hasn't failed.

Gotta link?

The S.

[jjb62556]

I have extra ball replacements if you need a few....

[randgust]

Gotta link?

The S.

See:  http://www.randgust.com/C63001%20shaft.jpg



http://www.randgust.com/C63002%20drive%20train.jpg



NWSL:  https://nwsl.com/collections/shaft-couplings-driveline-universals

It doesn't show real clearly, but the secret sauce to their product is that you have to use a Dremel or similar abrasive disk to grind the ends into a "D" shape to fit the socket in the shaft, you're not totally dependent on friction to hold the darn thing together. 

[atsf_arizona]

Great, Randgust, thx for this.   This seems like a systemic fix to these particular problematic Atlas stock connections.