US Hobbies GP-7

[R.K. Maroon]

...it would be prototypical if all the trailing units of your engine consist would have their headlights switched off (and thereby
not illuminating the class lights)

Yes, that is the idea (if we ignore the possibility implied by Dave of running the string light). As I said:

I already have installed two slides switches under the loco as it is -- one for each headlight. This allows me to MU this guy and have the headlights on or off as needed

This applies to all the units I plan to MU with the GP7. I mentioned earlier in this thread that the Milwaukee Road would often haul drag freights with lots of first-generation diesels up front. I have four appropriate units (two GPs and two RS units) that will make a nice string. I would really like to put any unit up front, oriented either short-hood or long-hood forward, and have the forward-pointing headlight be the only headlight lit. I may compromise though depending on what I am facing in modifying the other three units. Look how long it has taken me to get this first one done.

Jim

[De Bruin]

...... the Milwaukee Road would often haul drag freights with lots of first-generation diesels up front. I have four appropriate units (two GPs and two RS units) that will make a nice string. Jim

Jim has wandered into an interesting subject for me and since I've let go as in "viva la thread drift" have to ask-
Hypothetically how many powered units can you practically operate (as in track speed without throwing a circuit breaker or limiting fault) in O-scale world?
When I was in the DFWOSM club (Maroon's buddies) many years ago in Dallas, we used these big honking 20 amp bench/lab power supplies that could weld wheel-sets to rail if you weren't paying attention to derailments (good story for a different time) but I currently am limited (on track-world) to 8 amps and have discovered all these goodies like aftermarket solid state lighting circuits can lard up the load pretty quickly though in all fairness I'm not a whiz like Jim with electronics, likewise the downtown club is nominally 16 amps but results per block vary in actuality.
I have three matching OMI units, all Pittman cans, but no factory lighting. How does DCC handle the issue with more than two units, assuming they'll have boards installed and programmed to a single throttle?
I'm not too worried about getting them to run using straight current but think these should at least be set-up to accomidate adding the boards later.

[E7]

Jim has wandered into an interesting subject for me and since I've let go as in "viva la thread drift" have to ask- Hypothetically how many powered units can you practically operate (as in track speed without throwing a circuit breaker or limiting fault) in O-scale world?

Pete,

I am guessing if your power source was RC Battery, however many locos you could jam onto the layout given an operator and a controller for each one. That said, I don't remotely claim to be ANY kind of authority on the subject of RC Battery.. The biggest downside I can think of is if a loco wouldn't respond to a "stop" command and go trundling off on it's own, but I'm fairly sure there are other possible issues. I'm thinking one thing that might be in order is a switch to open at least one of the leads between the battery and the motor. Not sure if that would be necessary, but seems like a good fail safe to keep things stopped when you are absent.

Can't help you with your DCC question. My knowledge of DCC is slim and none and Slim is out of town.

As for the Milwaukee Road, very appealing subject to model in my opinion. Would need to have one of their Erie Builts for sure!

Rich

[ScaleCraft]

Hmmm...Do we want to get into a Battery R/C discussion?

Been doing model railroad battery r/c for what, 25 or more years.

In large scale, with locos under load just before slip can and do draw 5 amps, you can get into a real bind running any type of power attached to the rails.

But, hey, others probably have far more experience and will jump in momentarily.

[E7]

Dave,

Guessing you have forgotten more about RC Battery than I know. It is probably the way I will go if I ever get started. If not that just plain old DC. I'd be interested in ANY comments you have.

Rich

[ScaleCraft]

I'll get into it a bit later today. Shopping run now.

And charging 14 locos plus batteries for tomorrow.

[R.K. Maroon]

I am also interested in the general subject of operating multiple units. The DCC question is interesting but not in my wheelhouse. For DC operation, there seems to be a conventional wisdom regarding the need for all the units in an MU consist to have similar operating speeds for any throttle setting. I believe this to be more conservative than needed. Units with different gearing or torque-speed curves will automatically load share, which each unit pulling a proportional amount of the load and all couplers in tension. I would think the biggest hiccup might be in how the lash-up starts, but I think that often happens anyway even if all units are nominally the same, as each unit has its own friction characteristics and other unit-to-unit variations.

I have some more photos to post of the GP7 but I'll wait to see how this thread drift goes before going back on subject.

By the way, our club bought a surplus lab-grade variable power supply on eBay as a backup last year (after throttle problems at a show). The supply is rated at 10-amps, which I figure should be enough to run the two GPs and two RSs.

Jim

[ScaleCraft]

I get into arguments all the time on the wonderfulness of dcc and speed matching, setting curves....and I ain't got time for that BS.

With this stuff I use, I have done lots of multiple diseasemal units on same freq and address, and other that setting it for two button operation so you don't get a reverse out of sequence, nobody has been dissatisfied.

On steam, I laugh at folks demanding MU operation for steam. Never happened in real life.

So, on our 150' of 4%, if we have traction issues (usually really wet rails...like a storm) we drag one of two Shay helpers stored in the engine shed at the lower end of the 4%, couple onto the back, hold uphill engine transmitter in the uphill hand, reverse for pusher, and watch the coupler to see if you are applying adequate assistance. Works flawlessly.

BruceRainResize.jpg (101.47 KiB) Viewed 6682 times

That should give you and idea of how we do this.

[R.K. Maroon]

Here as promised is another shot of the lighting setup on the GP-7:

USH GP7 Lighting 03.jpg (367.46 KiB) Viewed 6625 times

Note that light fixture is located so that the spot from the penlight bulb lands on the dual headlights but not on the number boards. The stray light from the bulb is enough to light the number boards and markers. This is a very effective setup, and it only takes two diodes in series with the motor to get the voltage needed to light the bulb. I put a 1 ohm resistor in series with the bulb to dim it a bit so it lasts longer.

One other thing: Not all 112 penlight bulbs have a spot this clean. By a box of a dozen (cheap on eBay) and check them before you install them.

Jim

[R.K. Maroon]

I haven't posted on this thread since last summer, when I wrapped up the conversion of a USH MIlwaukee Road GP-7 from outside third rail to two-rail. The conversion included installation of switchable constant-brightness directional headlights and pickup wipers to all wheels. Since then I have been restoring a bunch of old Milwaukee Road boxcars and reefers:

Milwaukee Road String.JPG (54.35 KiB) Viewed 6431 times

The string is getting long enough now to warrant a second locomotive, so the mate to the first unit wound up on my workbench over the weekend. Here it is in "as arrived" configuration with the body removed:

USH GP MILW RD 2310 As Arrived.JPG (91.45 KiB) Viewed 6431 times

Note the outside third rail pickups and the penlight bulb headlights mounted to stray-light shields:

Pickups and Penlights.JPG (61.4 KiB) Viewed 6431 times

The pair of blue cylinders are capacitors. One of each is in series with each headlight. I have a theory of what the purpose of these was, which I will share if anybody is interested. I am not sure why that unused brass shelf was installed -- maybe to mount the capacitors originally?

More later
Jim

[ScaleCraft]

Guess on the caps....reduce low speed light flicker from open frame motor. Set up as bi-polar so direction is immaterial.

[J. S. Bach]

The shelf maybe as a guard to keep the wires away from the driveline?

[R.K. Maroon]

Those are both very reasonable guesses. The bracket may indeed be to keep the wires out of the mechanism. The circuit however is something I have never seen in a locomotive before. Here is the schematic:

As Wired.jpg (81.88 KiB) Viewed 6372 times

I am pretty sure I have this figured out, but others may want the chance to have a shot at it without my opinion in the mix, so I'll hold off for now.

Jim

[ScaleCraft]

The switch makes no sense other than to change the default start up direction (nmra right rail positive forward), and since OS 3rd, may be necessary as who knows what constitutes right rail.

Caps block DC, pass AC, so if this was originally a field wound motor running on AC, then the caps would have passed AC to the lights.

Something missing, like bypass resistors hidden in the shrink sleeving. Or directional diodes in shrink sleeving bypassing caps to give directional lights.

If the caps were across the light leads and to common, flicker (AC component) to lights would have shunted past.

Not done yet.

TOC

[R.K. Maroon]

One bit of information I left off the schematic but which could be gleaned from the photos and text that proceeded it: The bulbs are penlight bulbs, which are low-voltage bulbs. GE 222 in particular, rated at 2.25 Volts.