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Author Topic: Brass Mongering
Robert

Posts: 392
Post Re: Brass Mongering
on: November 14, 2017,
Quote

In the hands of many hobbyists this little locomotive would end up with questionable running qualities, and left to become operated only occasionally for a quick tour around the loop and back to a siding to gather dust for another few weeks.

But your going to get the maximum from it Ed, and that's why I'm so interested in the whole project. Keep on tinkering.

Robert

Ed Bommer

Posts: 362
Post Re: Brass Mongering
on: November 14, 2017,
Quote

Thank you for the encouragement, Robert.

Yes, I want this to be more than the shelf-queen it was when it arrived. I think I can get it to run reasonably well, although with fairly light weight, short train. The prototype rarely handled more than three cars, which can be seen in is photo earlier in the thread.

There is of course, an ulterior motive behind work on this loco. The next project will be building some Pullman Palace Plan 70 'suburban' coaches for it, which the prototype drew every day work.

Here are two plan copies for the Pullman Palace Plan 70 coach of the late 1870's. They are from the Illinois Transportation Museum. I had to sign model maker's license for their use with Bombardier Transportation of Canada, which owns the rights to these (and all other Pullman Company) drawings.
Image

Image

I plan to make styrene masters of a car side and end, develop molds and make resin castings of them. Two pours would do one car. Not sure about how to do the flat-end, monitor roof just yet. In the past making such castings was not a crowning success. In building an O scale depot of 1889 back in 2008, there were a number of parts pours which never set properly, staying soft and rubbery. Possibly from too much humidity?
Image

Wood frame trucks for these cars may also present some issues. But I think the coaches could be built with
resin castings, thin wood flooring and styrene and not weigh too much over a pound each. Lots of fussy fitting, but I'm hoping that Grandt Line's coach windows can be used. There are 36 identical windows per car!

Ed Bommer

Robert

Posts: 392
Post Re: Brass Mongering
on: November 14, 2017,
Quote

Speaking of encouragement Ed...here's a photo of my just completed Westbrook PRR Gondola which you gave me some helpful tips on building if you recall that. It came out nice I think.

Robert

Image

Ed Bommer

Posts: 362
Post Re: Brass Mongering
on: November 15, 2017,
Quote

That is one great looking gondola, Robert. Impressive!
Indeed, a Westbrook kit from long ago can be made into a very nice model.

Ed Bommer

Robert

Posts: 392
Post Re: Brass Mongering
on: November 15, 2017,
Quote

Thank you Ed...that means a lot coming from a master builder like you.

Robert

Tom-
Dempsey

Posts: 98
Post Re: Brass Mongering
on: November 16, 2017,
Quote

I second Ed's assessment Robert.

Ed Bommer

Posts: 362
Post Re: Brass Mongering
on: November 16, 2017,
Quote

The Gem Forney transmission is at last done. Pictures tomorrow. The batteries in the camera were too low and are being recharged as I write this.

The first order of business was to get the floating worm transmission unit (it rides on the driver axle) to stay centered on the axle gear. On center, one side of the casing plate was close to a brass boss on the driver gear axle. The opposite side had about 1/8" open space between the axle gear face and the casing. Lots of space in which to slosh about and get out of mesh.

The inside face of the worm transmission box on the open side was cleaned and tinned on each side of the axle slot. The box is made of two 3/64" thick brass stampings soldered together. Two 3/8" long pieces of 1/8" OD square brass tubing were cut and soldered in place to act as thrust spacers. They will help center the worm over the axle gear. It still has some side play, about .010" or so. Its not so much that it would upset the gear mesh than having 1/8" did!

The for and aft end play of the worm and shaft was reduced from .035" to about.0001" by adjusting with shim washers. The worm had not been centered fore and aft over the driver gear, so that was fixed as well. The worm and shaft turn without any undue drag, and will likely free up more as the transmission is broken in under power.

The mesh space between the worm and driver axle gear was increased by .019" on one side and .026" on the other. This was done by soldering in small strips of .015" x 1/16" strip brass into the crowns of the axle slots and filing them to re-fit the curvature of the axle shaft. It took thee tries on one side, two on the other to get the slots even. That way, the driver axle gear would be true and perpendicular to the worm.

All told this increased the space between the gear and worm by about .015". The mesh has about .0002" free play, which will also increase a bit as it's broken in.

However, before that can happen the bottom plate that holds the transmission to the axle shaft needed shimming. This was done with trial and error fits using styrene sheet of various thicknesses. The point here is to reduce to a minimum, the free play of the driver axle in the transmission case. Thicknesses used were .010". ,015", .020" and .025".

With .010", the axle was locked in the case and nothing could turn. With .015", it turned but was stiff and should have been freer. With .020", it was discovered that one axle slot was slightly deeper than the other, in spite of what my Vernier caliper told me earlier.

Well, take it all apart, solder in another .015" x 1/16" (x 1/8") piece of brass strip on the loose side, file it to fit, put it all back together and check again. Did this twice to finally get it right. .025" bottom plate shims were tried.

Everything was good and all turned freely. But the diver axle seemed too floppy. So, back to the thinner .020" shims. There is still a bit of play wit them, but I think it's tolerable, given the not exactly Rolls Royce quality of the original Gem transmission. The styrene test shims will be replaced with brass shims soldered in place.

Once assembled, the unit was run in slowly using an electric drill chucked onto the worm shaft. It was run in both directions for about 20 minutes, back and forth. This helped seat the bearing surfaces as pressure was applied to the drivers, to imitate a load.

Then a bench test, with the motor the loco will use. A temporary shaft coupling was made with plastic tubing (an old Badger airbrush tube) and some .005" shim stock (for the smaller diameter motor shaft). The motor was checked for its polarity/direction for forward operation (+ on that side!) and provided with hook up wires.

An HO power pack for testing provided the power. At a full 12 volts with the 28:1 reduction between worm and gear, the top speed seems to be about a scale 45-50 MPH with a slight load on the driver - more than enough for a Forney as they rarely went over 35 in service. 25-30 MPH was typical in 1890's commuter work.

One more test will be made. This time with the Forney's running gear fully assembled and on rollers. If the motor handles this well, the next step is adaptive surgery on the worm and motor shafts, grinding each down to half-width and adjusting their combined length for a brass tube slip-over coupling. It will also show where and how the motor will need to be mounted on the frame. Hopefully, all will fit as planned?

More steps lay ahead,
Ed Bommer

Ed Bommer

Posts: 362
Post Re: Brass Mongering
on: November 17, 2017,
Quote

Admittedly, my long tome in the previous message is not an easy read. "A picture is worth a thousand words" someone said a long time ago. That saying still stands.

Here are three photos showing how alterations were made to the Gem transmission box:

First was reducing the back and forth end play (or travel) of the worm shaft between its bearings with thrust washers. Also how the axle slot was filled in to increase the space between the worm and drive gear on the axle.
Image

Then, adding the 1/8"square thrust spacers to keep the floating transmission box centered on the main gear. You will see one of them slipped a bit out of line vertically due to heat from soldering in an additional spacer for the axle slot.
Image

Last, showing how the transmission fits on the driver axle and gear. Everything will be taken apart and cleaned for painting. I'm also thinking over how I might make thin brass covers for the transmission so the gearing is not exposed but can be easily lubricated as needed. Those little styrene shims for the bottom plate will be replaced with brass.
Image

Ed Bommer

Ed Bommer

Posts: 362
Post Re: Brass Mongering
on: November 17, 2017,
Quote

Here it is, fully assembled and running on a test set up. Spot facing of the worm shaft and driver axle is needed to secure seats for the set screws. Otherwise, the shafts may slip under high load situations.
Image

The motor and gearing ran smoothly. Enough so, that at full throttle as seen here the motor stayed on its rest without jiggling, jumping or vibrating. Next, to make a motor mount and coupling so all will fit on the fame and inside the cab.
Image

Seems to be a winner!

Ed Bommer

Robert

Posts: 392
Post Re: Brass Mongering
on: November 18, 2017,
Quote

Yes indeed photos are so helpful. I read all the words nevertheless on the chance of learning new things...which in your project is very likely. I didn't realize this gearbox tuning was so important to the final operation of the locomotive. Curious why you didn't clamp the square thrust spacer to prevent it from slipping? Rollers sure help prove out a mechanism, I use mine more often than I thought I would...in fact I will use them today to try and isolate a squeak in one of my locomotives.

Still reading

Robert

Ed Bommer

Posts: 362
Post Re: Brass Mongering
on: November 21, 2017,
Quote

Removed because of a posting glitch saying it was spam.
Same message is below:

Ed B

Ed Bommer

Posts: 362
Post Re: Brass Mongering
on: November 21, 2017,
Quote

Admittedly I took a chance by not using clamps on the transmission box spacers. There is not much room between them for soldering in a driver axle slot shim on that side. Both of those should have been clamped.

Moving on, the machinery of this model loco (or any other) needs the best possible set ups for clearances, tolerances and alignments for smooth operation that is as friction-free as possible.

The small motor I am using will be put to its maximum output to move the loco with a short train. I set up the mechanism with all drivers connected, then laid the boiler weight and superstructure on the frame to test the motor. A bit worrisome as it takes a little over 1 amp to get it started. It draws about 1/2-2/3 amp when running. Very much on the borderline.

In re-checking everything, the cylinder block casting is not perfectly square. I will need to add shims to the right rear corner where it fits into the frame to correct that. The screw that holds it to the frame is not able to keep it tight enough. It can move a bit when the loco runs.

Next, the coupling of the motor and worm shafts was done by cutting them down to "D" shaped half-shafts, so that a piece of tubing is used to hold them together. Here is the start of that process. The motor was wrapped with masking tape to trap steel filings of the shaft over the magnetic field in the casing. A Dremel cut off wheel was used. Forceps hold the easily turned shaft until a flat surface is cut into it.
Image

Exactly half of the shaft is cut away with the cut surface made smooth, straight and perfectly even for its length. The micrometer helped with that for the motor and worm shafts, which happen to be of two different diameters. The motor shaft is smaller than the worm shaft. The worm shaft is about .006" in diameter smaller than 1/8", and the motor shaft is about .005 smaller in diameter than the worm shaft.
Image

To get the motor shaft closer to the worm shaft size, a piece of .005" shim brass was attached to the remaining side with a little barge cement to keep it from slipping. The object in fitting the two shafts together for a slip joint coupling is that they must share the same center point. This was done by carefully grinding each shaft flat until they were concentric. This was done on the flat of the Dremel wheel, lightly touching the two shafts many times over until the measurement was correct.

Then the motor and worm coupling test with the slip coupling which is a piece of 1/8" ID brass tubing. I found
I had to make a few of these to get one that was truly concentric. Brass tubing sometimes may not be perfectly round or have exactly even wall thickness. It all depends on the quality of manufacture. Here is the finished coupling, ready for a powered test.
Image

Ed Bommer

Ed Bommer

Posts: 362
Post Re: Brass Mongering
on: November 21, 2017,
Quote

When linked and run, the joint was noisy and jittery. This was due to the shaft diameter being slightly smaller than the ID of the brass tubing, as you may recall from above. The fit inside the tubing was too loose. So a shim was cut from some thin aluminum (about .008" thick from a used offset press master) and slipped between the flats of the motor and worm shafts. This snugged the fit of the two half-shafts inside the brass tube and still allowed it to slide on easily. Everything was given a touch of lube oil as well.

Then total power was applied, as seen here. There is still a bit of vibration at very high speed, indicating concentricity may be slightly off.

Image

True concentricity is a difficult goal to achieve. I don't have high precision machine shop tooling to do this critical work. However, the vibration seems minimal and in operating the model the RPM's seen here would not be reached anyway, So perhaps a flex mount for the motor to frame connection may be sufficient to isolate this vibration and possible noise.

Now, to get his set up to fit inside the loco frame and cab!
Ed Bommer

Robert

Posts: 392
Post Re: Brass Mongering
on: November 21, 2017,
Quote

Yes I was wondering if you had planned to cushion mount the motor to the frame...and so you are.

Curious...would a tiny universal coupling such as available from Sterling Instrument have worked in place of grinding those flats? Thinking in terms of getting one sized to the smaller shaft and then enlarging the bore in the opposite end to fit the larger shaft?

Is this locomotive going to be run with a DCC system?

Robert

Ed Bommer

Posts: 362
Post Re: Brass Mongering
on: November 21, 2017,
Quote

Posting error

Ed Bommer

Posts: 362
Post Re: Brass Mongering
on: November 21, 2017,
Quote

All told, the shaft coupling length (and ground shaft overlap) is 6/32" - just over 1/8". While such a universal joint would be great, I think it would be too long to fit this application. Also, the smaller the U joint, the less capable it may be under varying torque stress.

I trimmed the ends of the motor and worm shafts a little at a time, until the motor fitted into the allotted space. The back head casting was temporarily mounted to the frame. It will carry the sheet brass boiler casing through the cab to the front wall, covering the motor.
Image

The casing will be detailed with gauges, the throttle and reverse lever, as well the vacuum brake valve. Those last two will be on a small flange that rests on the cab floor. The cab boiler casing and rear wall of the cab will be made as a removable part, to simplify disassembly of the model loco for repairs.

A sharp eye will note that the worm and motor shafts are not in perfect alignment. That will come when the motor mounting bracket is done. Also, a limit block will be added to the frame so the transmission case will not rotate forward too far and slip out of the coupling. As one can see, the fit of the motor to the frame is very close indeed.
Image

Flexibility is needed since the drivers are sprung. A cushion mount for the motor frame will also help. However, the coupling between the motor and worm gear shaft needs to be as close a precision working fit as possible.

Another step along this journey,
Ed Bommer

Robert

Posts: 392
Post Re: Brass Mongering
on: November 22, 2017,
Quote

I didn't realize the coupling length was so short. You've managed to make a difficult fit successful while maintaining the desired function of the drive train. Ed, will this engine be operated on a DC or DCC system?

You've dispatched each problem with well thought out creativity...so interesting to follow this. Thank you!

Robert

BruceB

Posts: 59
Post Re: Brass Mongering
on: November 22, 2017,
Quote

Very enjoyable and informative thread. Thanks Ed!

Ed Bommer

Posts: 362
Post Re: Brass Mongering
on: November 22, 2017,
Quote

While I do not work with DCC, this model will be DCC compatible.

A decoder could be mounted inside the tender shell. Also, the motor has a + and - connection plug for its wiring. The loco is wired with a harness that has negative side contacts on all wheels. The positive connection from the frame (using the rear truck mounting screw) is also wired, like the negative side, to the plug for the motor. So connecting a DCC decoder should be rather easy as the motor must be isolated from the frame.

I'm still undecided about wiring the two head lamps. Unless run at night, they were not lit back in their era. Lit headlights on locomotives during day time is a largely post WW-II development.

Coal oil or kerosene burning headlamps were troublesome to light and maintain (especially in bad weather!). There was no simple on and off switch for them. Somebody had to get out there, open a side panel and light it with a match or burning stick of wood. Then adjust the lamp setting for best light.

Further, oil burning head lamps had to be cleaned and their reservoirs refilled on a regular basis. While most often done on terminal layovers, sometimes there was trouble with these fragile lamps out on the road.

Acetylene headlamps replaced some oil burning lamps by the early 1900s. A few autos of the period also had them. Electric arc headlamps came about as well. But their main use was in movie theatre projectors. After WW I, light blubs were developed with filaments rugged and bright enough for railroad work. Their descendants were the 'rough service' light bulbs used with garage door openers.

But I digress.
For these bi-directional Forney locos, night service likely meant both headlamps were lit. One of the daytime class flags or some other blind was hung over the lit headlamp not facing the direction of travel, so its light would not stare too deeply into the following coach.

Not doing DCC, I might install 12 V grain of rice bulbs. They have the best shape for modeling the tall glass globe chimneys used inside oil burning headlamps.

Or, it would not be too difficult to put in a diode bridge for constant/directional head lamps with 1.5V bulbs, if the Swiss motor can be suitable ballast for them. Some sort of reed or magnetic switch might also be fitted in for turning the headlamp circuit on or off. As for LED's, they are a step beyond me at this point.

But that's crossing bridges which are farther along this road!
Ed Bommer

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