does motor replacement typically require a new worm/workgear?

[dinwitty]

NWSL has shims to fit smaller shafts.

[doctorwayne]

For a lot of older models, brass, diecast, or plastic, it's a matter of tailoring the conversion work to suit the particular model.
Open-frame Pittman-type motors are good candidates for new rare-earth magnets.  These generally lower current draw and motor speed, improve starting voltage requirements and power output, too.
This brass switcher was given to me by a friend, who claimed that it wouldn't pull enough cars....

In addition to new magnets, I added all-wheel pick-up, quite a bit of extra weight,l and gave it a new paint job....

When he came to visit, I ran it at the head of a 20 car train (on level track).  While he was duly impressed, he wouldn't take it back when I offered it, as he had already purchased a larger replacement.
Such magnets are available almost everywhere, nowadays, but I got mine from MicroMark.
Stack together as many as will fit (make-up any leftover space at the top using sheet steel - old Athearn-type car weights, cut to size with a hacksaw, work well) and make sure that the polarity matches that of the original magnet. 
Here's one for a brass 10-Wheeler...

This ex-B&M B-15 Mogul had an open frame motor but would barely run....

This was before the magnets, shown above, were available, so I replaced the original small motor with a very small NWSL can motor.  Unfortunately, the motor was wider than the original, and while it could, with difficulty, be fitted into the boiler, it couldn't be mounted on the loco's frame because, once mounted there, the boiler/cab assembly wouldn't fit over it.  I solved that problem by mounting the motor in the boiler, with half the NWSL U-joints mounted on the motor shaft and the mating parts mounted on the worm's shaft.  Tweezers were used to line-up everything during assembly.

Many years ago, I re-built two brass 10-Wheelers for a friend when their open-frame motors wore out.  However, I couldn't, at that time, locate can motors small enough to fit within the boiler/cab assembly.
Instead, I dismantled the old motors, leaving only the frames and bearings, and replacing the original motor shafts with longer ones. I removed the worms from the old shafts and re-installed them on the new ones, then re-mounted the empty motor frames in their original position, with the new, lengthened shafts protruding from the rear. 
I put a large, flat can motor, laying on its side, in each tender, then added NWSL universals between the motor shafts and the extended ones in the locomotives.  While the new set-up worked okay, the motor torque would cause the tenders to tilt to one side, depending on the direction selected for operation.  This was corrected by adding bearing blocks, made from Kadee #5 draught gear cover plates, between the tender frame and the truck sideframes (the Kadee plastic was the only source, of which I was aware, for black plastic - essential for an appliction that would otherwise quickly wear away a coat of black paint.  That taken care of, I added as much weight as possible into the cab and boiler of the two locomotives.  Low speed performance was much improved, and pulling power greatly increased, and a casual observer wouldn't even notice the driveshaft between tender and loco.

Can motors are now available almost everywhere, and at much better prices than when first introduced.  I got five small, low-rpm cans on-line for $13.00, and used them to replace a worn-out can motor in an IHC Mogul...

...and an open frame motor in this brass Mogul, currently being re-worked to match a specific prototype...

Again, depending on the particular model, you may wish to use the original drive train and gearing, or replace the latter with a new gearbox.
NWSL offers several variations, and many for specific models.  I've used their universals, but for many applications, model airplane fuel line is a good choice, too.  It's available in different sizes, and can solve the issue of disparate shaft sizes at a very low cost.

Wayne

[richg1998]

Not sure all know but the worm is on the motor. The worm gear is on the driver axle.

Rich

[snjroy]

Hi there. Personally, I try to preserve the worm (edited, thanks Rich). If the motor shaft diameter is too small, you can certainly add a bushing that can be purchased from NWSL. I've done it several times succesfully. I file the shaft a bit to get a bit of friction and glue the bushing with CA.

And yes, you can use caulk (I use silicone) to attach a new motor. This can be a bit tricky and you might have to go through a few tries to align the motor properly. A new high quality can motor will definitely be quieter than an open-frame motor, and draw less amps if you are considering DCC.

But increasing the power is something else. Power issues are often related to (insufficient) weight or unbalanced weight of the loco itself. They can also come from friction coming from somewhere else in the power train. It is unlikely that installing new motors alone will improve the power of your engines.

I have never replaced magnets but there are a few advocates on this forum of rare-earth replacement magnets for Pitman motors. I prefer to replace the entire motor myself but to each his own.

Simon

[richg1998]

Many years ago I replaced a motor in two locos using a Sagami can motor from NWSL. New worm and worm gear. I used bath caulk and carefully aligned the motor for minimum gear lash. One loco was 45 to 1, the other a switcher with 72 to 1. Both quiet.

I used the MDC step gear set up. The bath caulk was the reason. The 72 to 1, the motor rotated at a higher rpm even though the loco would only run at 20 mph max.

NWSL sells adapters for shafts that I have used.

Call or email Dave at NWSL. He has helped me.

Edit.

Some years ago I had an old all metal MDC 4-4-2 with a Pittman two amp motor that Dave replaced for me. Cannot remember if worm and worm gear on driver.

Rich

[mbinsewi]

I'm not familiar at all with the types of motors you show, Greg, as just about everything I have repowered has the can motor with the flat side, and flywheels, but I do usually have to change drive shafts, and sometimes worm gears, depending on the make of loco I'm working on.

Mike.

[gregc]

while my locos run OK, one is noisy and others, i feel, would run better if they had more power.   I don't need speed.

whenever i've considered replacing the motor, i have difficulty finding a motor with the same shaft diameter of the existing motor and worm.

i assume i can find a new worm matching the shaft of a new motor from NWSL, but wonder if i also need to replace the wormgear on the drive axle.

and then, when replacing an old Pittman motor, there's the issue of whether a new motor can physically align with the existing workgear or if a gearbox is needed, which may be more expensive than the motor.

or maybe a bushing/shaft adapter ($6) is a way to use the existing work with a new motor.

in particular, two of my locos, GEM Reading B8 and ? boxcab have vertically mounted motors very similar to the Kemtron.   Not sure about replacing the magnets on this type of motor.

what are my options?

thanks