Atlas Universal Joint Repair Donut

[C855B]

Cussed and discussed in this thread was the problem with the motor shaft universal joint "donut" cracking on several Atlas N scale 6-axle models. I personally know this to be the case on the SD24 and C628/C630. I have not checked the SD7/9 and SD35 as yet, and there may be others that don't immediately come to mind such as the FM Trainmaster.

Anyway, the problem needing to be solved was availability of the replacement part since this is a consistent and repeated issue. My solution was to reproduce the donut on my (original) Photon printer using regular Anycubic gray resin. Bottom line is success:



The black donut on the left is an original Atlas part, the gray one is the 3D print. The SD24 repaired with this homebrew part runs great. I have no idea as to longevity since I have but two hours of run time on it.

The STL file if you are able to print your own is here: http://www.everywherewest.com/Atlas_Universal_Donut.stl

Only post-processing required is to ream the shaft hole with a #55 (0.052") or #54 (0.055") drill bit since the resin process isn't particularly accurate for small holes. The 0.055" drill bit is almost a slip fit, so you would want to use a tiny drop of Loctite 680 to secure it as noted in the original thread. Additional info in post below.

EDIT: STL URL fixed.

[Erock482]

Excellent work and write up solving a seemingly common issue. Well Done!

[C855B]

Additional info:

Add the SD7/9 to the list. Just repaired one.

Also, be ready to add a #53 (0.0595") drill to the reaming process. The SD7 I just fixed would crack the new donuts on insertion without the extra reaming. The motor shaft is obviously supposed to be 0.060", so the #53 hole was barely a press fit on this loco. It ran well and was not slipping under load, so I'm going to let it run that way for the time being.

The nice thing about the resin prints is that it takes the same amount of time to print 1 or 100, the additional 99 consuming pennies' worth of additional resin. So if you crack a few, crunch all you want, we'll make more.

Three out of the three I opened-up in the past two days had cracked donuts. Like I said, there's no experience yet whether the photoresin approach is going to be any better, short- or long-term, but we do know the original design is certainly lacking.

And thanks, @Erock482 ! Thank you!

[johnh35]

Mike, do you have any plans to sell these if there is interest?

[C855B]

PM sent.

Another note - the SD35 and Trainmaster have different driveshaft designs and aren't affected by this bug.

[wcfn100]

The H15/16s use this part as well.


Jason

[JMaurer1]

I have a small fleet of SD-7s and 9s (NWP mostly ran them) that I haven't run for awhile and now you have me nervous. I really hope that this part isn't the reason I have to buy a 3D printer. I already have a library of things that I want printed but I also know that having something and USING that same something are two very different things (I have an ALPS printer for two years and never printed a thing...next thing I knew, my computer no longer had a port that the printer could connect to). Either way, thanks for making this available!

[peteski]

(I have an ALPS printer for two years and never printed a thing...next thing I knew, my computer no longer had a port that the printer could connect to).

There are workarounds for that, but Alps printers are still "happiest" and the install is easiest one an old XP machine (I still use Win98SE and XP to run my Alps MD).  If you ever get serious abotu using it for decals there is a community of over 2000 Alps users on https://alps.groups.io/g/ALPS

[MK]

I have an ALPS printer for two years and never printed a thing...next thing I knew, my computer no longer had a port that the printer could connect to.

What port do you need?  Like Peteski said, there are many USB to XXX adapters/dongles out there.  You can pretty much convert a USB port to anything now a days.

[peteski]

What port do you need?  Like Peteski said, there are many USB to XXX adapters/dongles out there.  You can pretty much convert a USB port to anything now a days.

It uses parallel interface. Yes, USB-parallel (LPT) port is the solution, but it has some limitations, and the drivers can be a pain to install. Alps drivers also only work in 32 bit OS. setting up a VM to run the printer usually ends up with more problems.   Like I mentioned, using older physical hardware and OS is the easiest solution.

[wcfn100]

Like Peteski said, there are many USB to XXX adapters/dongles out there.  You can pretty much convert a USB port to anything now a days.

You have to have one with good drivers.  IIRC, one issue is not being able to change the COMM port on some adaptors.

Jason

[peteski]

You have to have one with good drivers.  IIRC, one issue is not being able to change the COMM port on some adaptors.

Jason

LPT (parallel) not a COM (serial) port.  It is a different problem.  It is the lack of bidirectional (hardware) capabilities on some USB dongles. But the bigger problem is the 64 bit OS which pukes on Alps drivers (which are decades old).  Trust me, we have been over this ad nauseam on the Alps groups.

[wcfn100]

LPT (parallel) not a COM (serial) port.  It is a different problem.

Okay,  I may confusing this with some DCC stuff from years ago.

Jason