Here's an application of the 3D printed wiper blocks for one of David's F7B units. I tore into it because there was an out-of-gauge wheel that caused frequent derailments. The wiper screws are 0-80 and the mount to the spring plank 2-56. These holes were hand tapped since my FDM printer can't print useful threads at these miniature sizes.



And the final installation. I really like Rod Miller's wipers.



An astute observer may notice that the right side gear box is not tightly screwed together. I discovered that some of the wheel axle gear profiles changed between early and late models. When the screws were fully tightened, there was a once-around bind with the brass worm. Loosening the screws a tad allows the two gearbox halves to slightly move relative to each other. I applied Loctite to the 4-40 gearbox screws to keep them from loosening.

Jim -

I'm glad you are participating on this thread! You have helped me break out of some mental blocks and arrive at better solutions, for which I am appreciative.

I'm in no way concerned about insufficient top speed with the Portescap motor. In fact I still plan to change the P&D 15:1 reduction to 25:1 reduction. That should multipliy the motor torque by about 1.6, although I do not anticipate lack of torque to be an issue. It will, however, reduce the average motor current.

The A&O isn't a racetrack display layout. It is for guys who like to operate. Although it is in a huge basement, running fast on the mainline and getting to the next "town" in a matter of seconds doesn't satisfy and would be an undue stress on the dispatcher. Most trains do switching, and for that smooth low-speed control is preferable.

What top speed is appropriate for your models depends on how you want to run them. The Reading ran a lot of SW "pups" in mainline coal hauling. On the other hand, GCOR limits the top yard speed to 10 MPH, although many modelers run faster than that, seemingly trying to pop a wheelie when accelerating from a stop. When when stopping, they stop on a dime, which sometimes may unfortunately be in the brakeman's pocket.

I anticipate that the larger HO decoders, such as the 58240, should be able to handle the motor current. The thinner height opens a lot of possibilities.

I also don't expect the less powerful amplifier in an HO decoder to be an issue. Our ears respond to increases in SPL in a logarithmic fashion, so a 3W amp isn't 3X as loud as a 1W amp.

The keep-alive is a consideration. ESU sells good 3-wire PowerPacks. The small one has a single 1 Farad capacitor. The 5L decoder has two 1 Farad capacitors. The large PowerPack has two 5 Farad capacitors. But sometimes the longest run time isn't the best. How much trouble can a derailed locomotive get into in only 4 seconds? Can it meet our nemesis gravity?

As for lift rings, glad to hear your SD40-2 measurement matches. Also note that the cast base or washer of the lift ring is of a large diameter. For a while I was concerned that the P&D lift rings were about 30 thou in diameter, but that's about not oversize. If anything it is undersize.

Hi Bob,
I have another pair of questions regarding the re-motor project.  I hope I don't tire you out tugging on your sleeve all the time. 

I notice in your motor comparison matrix that the Portescap motor has a significantly lower no-load speed than either Pittman option.  Presuming that gear reduction remains the same without regard to choice of motor, does the lower top end speed present any issues for you?  I recognize that we seldom run our models as fast as they could go, so I suspect it's not a problem.

In a different context, where reduction is not predetermined, the no-load or rated speeds do affect a final gear ratio, which in turn affects torque.  It's been a bit of a balancing act as I seek a suitable motor for my switcher project.  It seems that many of the better quality motors have substantially lower no-load speeds compared to the Pittmans.

The second question is in regard to the use of an HO decoder, in particular one of the ESU Loksound variety.  Do the HO decoders have enough power to successfully feed the Tang Band modules?  Or to power a TB module and a smaller driver for the bell and horn, as I believe they have two speaker outputs.  Also, the large format Loksound decoders have onboard keep-alives now.  Are they integral or separate on the HO versions.  It would be nice to use an HO decoder for space and cost, although some of that may be offset if a separate keep-alive is required.

Jim

With the printed blocks I will have to carefully trim the length of brass grab irons so that they don't extend past the inside wall of the shell.

I've just been re-reading this thread.  Could you not leave some voids in the light blocks to account for grab iron penetration?  You could do blind holes, or full depth, and you could do holes for each leg of each grab, or a slot per grab that accounted for both legs.  Some precision would be prudent for the top two grabs near the numberboard and class light openings, but the rest could be generously sized to allow plenty of room for penetrating wire and glue blob.

Jim

Rick -

The motor is a custom unit, military surplus. 216E specifies a 12 Volt 10 Ohm winding. It has a double shaft, but curiously one end is 3mm and the other end 2mm diameter. Mounting screws are normally metric but this one was tapped 4-40.

At the moment the listing has disappeared from eBay. The seller was Elimia Industrial. They sold for $37 each in single quantity. I found a stock motor from an industrial supply house in England, but the price was about $200 USD.