So I picked up this little Suydam HO scale electric work motor at an antique fair. It needs some cleanup and painting, but the price was right and this model is long since out of production.
It’s in pretty good condition, sort of runs after some cleaning, lubrication and adjustment, and it closely resembles a prototype on the railroad I model. I’m inching my railroad back in time (eventually will hang trolley wire) so this little gal will come in handy–the prototype I’m modeling was Sacramento Northern 701, a homebuilt work motor commonly called “Old Maude.” The prototype was used for railroad construction and light-duty freight hauling, scrapped in the mid-1930s as she was just too lightweight to be very useful in freight service.
But Old Maude has a problem. Power is via a small motor under the floor, which delivers power via two driveshafts. The screw on a coupling on one of the driveshafts is missing, resulting in one driveshaft that turns and another that just spins:
As I mentioned, it kind of runs, but because of the single driveshaft not working the mechanism occasionally binds up and stops running.
By comparison, here is what the other coupling looks like:
Any advice on how to find a replacement screw that has been out of production for decades, and whose manufacturer is out of business? Or is there a simpler solution?
The screw is not a custom part but some stock item. It will be metric since it is from Japan. The trick will be to find the correct screw without buying 25 different screws. A micrometer and screw guage should get you to the proper size and then be able to purchase said screw. If you have a good hobby shop they may be able to help.
Gidday, It’s a dying trade but if you have a clock maker/watch repairer in your vicinity, I’d be tempted to remove the other screw and see if they have a match. If it’s an unusual thread pitch or size they may be able to re-tap the hole and provide the appropriate screw.
Another possibility would be an optometrist - they do use microscrews to assemble eyeglasses.
If you find a screw with the right thread but the wrong length and/or head design, you can get creative with a Zona saw and files to reduce it.
When installing a collar with a set screw, it’s always a good idea to file a flat on the shaft before assembly.
Tsubomi, the shop that built Suydam’s models, was a micro-factory, located in a couple of ground floor rooms of the owner’s house. They also produced some fine models of JNR electrics, and those ‘plantation’ 0-4-0Ts in HO and HOn3.
I’m sure that NWSL will have suitable replacement screws, but you could also check out their drive train universals and their Stanton drives. Either of these will likely improve the performance.
They show up at some of the larger train shows. You might be able to get a show schedule from them. Look for all shows. It wouldn’t surprise me if they are at model plane and car shows, too.
Stanton drives are neat but way too big for this application–the trucks on this freight motor have axles spaced 5’ 6" apart with 28" wheels, while the smallest Stanton is for 6’6" and 33" wheels! The motor actually runs very nicely after a little tuning and cleaning, picks up power from both trucks, but only supplies power to one truck.It even runs around my tightest 12" curve with no problem, although it runs better in one direction than the other because of the unpowered truck.
I guess it’s time for a screw assortment from LHS or LHS (my local hardware store does carry a lot of tiny brass screws, as does my local hobby shop) and some test-fitting, followed by some creative saw work to turn it into a set screw small enough.
As a temporary/permanent fix, you can use super glue. The screw used is called a set-screw, and these were commonly used until good press-fitting plastics came along.
NWSL universals would make good replacements, but flexible drive tubing would also do well (there’s a guy who sells the stuff a lot on eBay). Or, if you want to replace the whole drive, check out the LoBoy by Hollywood Foundry.
Just guessing, but it looks like that’d be a 2mm set screw. I’d get a 1.5mm, a 2mm, and a 2.5mm screw, and see which one fits. Lots of sources for them out there (NWSL being one, I’d guess), and they’re not all that pricey…
