Pittman Motor Upgrade for Williams Cab Forward

I remember changing out the open frame DC motors in Athearn HO scale locos and Hobbytown power chassis kits in the 70s and 80s. Even back then, the difference was like night and day. I’m sure the Pittman’s of today are even better.

@Rich Melvin posted:

I remember changing out the open frame DC motors in Athearn HO scale locos and Hobbytown power chassis kits in the 70s and 80s. Even back then, the difference was like night and day. I’m sure the Pittman’s of today are even better.

Well, the Mabuchi RS-550 is a crappy 3-pole motor, so it kinda' runs like the old Lionel open frame motors.  Seems to draw as much current as well, I was blown away with almost an amp sitting on the bench with nothing connected to it!  Noisy as all get-out too, and you couldn't really tell that the Pittman was running.

It's sad that Pittman priced itself out of the model train market, they were far and away the best motor I've seen used.  I guess the Buehler Motors are a close second, but they are even more expensive than Pittman motors now!  Lionel used the Buehler in a couple of locomotives, but I've only ran across a couple.

The gear box in those engines are geared to the moon & back, …..don’t expect to break any land speed records, and running slow with a long drag will have some increased motor RPM’s, but it’ll work,…..The reason Williams used the amp hog  550, was because it’s speced to turn 10,000 RPM. …..this way, the motor could outrun the gear box. It’s the other way around with a Pittman….youll run out of motor, long before you ever run out of gear………

Pat

Are the Mabuchis any more efficient at high RPMs? If you can stand the jet engine level noise maybe they do ok if you do have some low gearing?

Nice work!

What does a Pittman cost relative to other commonly used alternatives?  Just curious,

Merry Christmas!

@rplst8 posted:

Are the Mabuchis any more efficient at high RPMs? If you can stand the jet engine level noise maybe they do ok if you do have some low gearing?

No, they start off as amp hogs, and continue to guzzle energy at an alarming rate.

Pat

@Ray Lombardo posted:

Nice work!

What does a Pittman cost relative to other commonly used alternatives?  Just curious,

Merry Christmas!

To buy a modern day Pittman/Ametek motor today from the now parent Ametek, would literally knock your socks off. Ametek priced these motors right out of our hobby. They focus on aeronautics, aerospace, medical, & things like ATM machines. We search the world over for Pittmans on the secondary market. Sometimes you can find a deal, other times, you can’t …..

Pat

The patents on Pittman motors have to have expired by now, it's really surprising that a lower cost manufacturer hasn't stepped in.

If Pittman previously made the motors at a lower price point, it should be doable.

I guess like John always says, nothing is as easy as you imagine someone else doing.

Still it seems odd since motors are relatively simple devices.

@rplst8 posted:

The patents on Pittman motors have to have expired by now, it's really surprising that a lower cost manufacturer hasn't stepped in.

If Pittman previously made the motors at a lower price point, it should be doable.

I guess like John always says, nothing is as easy as you imagine someone else doing.

Still it seems odd since motors are relatively simple devices.

No, Ametek still vigorously holds onto the patents for the skewed armature design. It’s what makes Pittman’s lo-cog motors so smooth. Some manufacturers have copied Pittman’s can design, end bell designs, seamless can, etc, etc, etc, but they still don’t have that twist in the armature. It’s that twist that makes virtually zero cogging effect. That’s what makes command control so incredibly smooth with just a simple worm on wheel gear box in our hobby. Without that, the model mfr.’s had to come up with workarounds to make the first & lowest speed steps as smooth as possible for us consumers. Lionel adopted the double lead worm compound gear box, that allows inertia to eat up any motor cog, and MTH had to of altered their electronics to compensate …….Ive been inside all the “knockoff” Pittman replacements, ….SPG’s, the black can motor MTH uses now, and the god awful Cannon,…..none have a skewed rotor, and you can feel the cogging effect when you hold these motors in your hand, and slowly rotate the armature shaft.

Pat

@harmonyards posted:

The gear box in those engines are geared to the moon & back, …..don’t expect to break any land speed records, and running slow with a long drag will have some increased motor RPM’s, but it’ll work,…..The reason Williams used the amp hog  550, was because it’s speced to turn 10,000 RPM. …..this way, the motor could outrun the gear box. It’s the other way around with a Pittman….youll run out of motor, long before you ever run out of gear………

Pat, I never break speed records anyway with anything steam.  I know these have the infamous Williams 44:1 gearing, I've upgraded a few Williams steam from the same era.

@rplst8 posted:

Are the Mabuchis any more efficient at high RPMs? If you can stand the jet engine level noise maybe they do ok if you do have some low gearing?

The Mabuchi RS-550 never gets below around .8 amps free running, I hesitate to even speculate what it needs under load!

Here's a comparison of the motor I took out and an identical one to the one I put in.  Note that true to form, the Mabuchi was still drawing around 6X the current that the Pittman was throughout the range from 1V to 12V power to the motor.  The voltage steps are 1V.

Just the noise level of the Mabuchi motor is enough to frighten away the train crew!

@rplst8 posted:

The patents on Pittman motors have to have expired by now, it's really surprising that a lower cost manufacturer hasn't stepped in.

Actually, there was a Chinese knockoff that was decent, I believe MTH used it in a couple of engines.  I actually have one in captivity.

No ID of any kind, but the design is obviously the same.  The screws are smaller than the Pittman, but other than that, you can hardly tell the difference.  It draws a little more power than the Pittman, around 30%, but still decent.  It's also not quite as silent as the Pittman, but again, much better than the Mabuchi.

Any motor whether Pittman or Mabuchi you pay for RPM with current draw even running free without any load what so ever. if you want a scale top speed with the 44 or 42:1 gearbox your going to need a lower static resistance motor (lower voltage rating). You can tame the sound a bit but not the current pull. I line the inside of the brass body with foam tape like used in air conditioning  on the high pressure side and surrounded the motor with foam being careful not to obstruct the vent holes in the motor. On smaller locos than your  cab forward I use mabuchi 385s or 395 motors when space allows the 44:1 gearing provides enough torque a the wheels that even the smaller motor provides enough power. Also with that high a gear ratio you will not see much difference in start up and creaping speeds between a 3 or a 5pole motor and the 3 pole will spin faster than a 5 or 7 pole at any given static resistance. Mabuchi does make a premium line of motors with Neodymium magnets ball bearings and silver/graphite brushes,  if your willing to pay almost as much as the Pittman. One option is to install a 9v pittman if you want more speed. I have not tried that and it is bound to run a bit hotter than the 12v however the Pittmans have a higher static resistance than their Mabuchi counterparts and if you check the motor temp till you determine how long and what load you can get by with it may give you the additional top speed. Another thing which creates a lot of noise in the Williams locos is often the flywheel is drilled off center and wobbles creating vibrations and noise so you need to make sure your flywheel is concentric. Power the loco chassis on blocks and see if your flywheel wobbles at all. At the higher rpm needed with the 44:1 gearing it must run true. I guess all this is why I sold all my Williams articulated locos. Though I have several of their Mikados and Northerns.    See pix for how I padded the inside of boiler shell and mounted the motor in foam.                   j         

I was going to send my Williams Challenger to Pat for fixing the low gear box issue. I didn't want him to lose interest in fixing trains!

( like I have)

@JohnActon posted:

Any motor whether Pittman or Mabuchi you pay for RPM with current draw even running free without any load what so ever. if you want a scale top speed with the 44 or 42:1 gearbox your going to need a lower static resistance motor (lower voltage rating). You can tame the sound a bit but not the current pull.    

We'll have to agree to disagree on this point. There's a little more in play here than simply the RPM.

The Pittman motor runs at a measured 5100 RPM with 12VDC on it drawing 230 milliamps.

The Mabuchi RS550 motor runs at a measured 10800 RPM with 12VDC on it drawing 1180 milliamps.  When I slow down the RS-550 where it's running around 5,000 RPM, it's still drawing over 900 milliamps.

All measurements on the bench with no load on the motors.  However, adding a flywheel to each didn't really change the current readings by more than a couple percent.

One problem with the RS-550 is the 3-pole design where the Pittman is a 7-pole motor.