US Hobbies GP-7

[R.K. Maroon]

Allan asked for photos of the underside of the GP-7:







The axle gearsets look a lot like All Nation, but I haven't put one side-by-side for direct comparison. The gear ration on these is 8:1 and my records show that an All Nation is 8.5:1, so maybe they are not the same. These are certainly not the standard KTM gearboxes that I am used to seeing (and that Allan is repairing in a different thread). Anybody recognize these as something other than All Nation?

Jim

[Jay Criswell]

Jim,

If I had to bet your life on it, I'd say A-N. What I don't see is the gears for the tower end. Straight cut or angled? Speedo cable or ball & socket?

Jay

[hibar]

The US Hobbies shells have the Lifting jack pad castings [I believe that is what they are called]over the center of each truck, to my knowledge all came with zamac enclosed axel gearboxes. I was a "basement" dealer for USH for many years and moved a lot of product until Westside and escalating prices effectively dried up my customer base.

[Jay Criswell]

To be honest, nothing looks exactly like I'd expect. Knowing how good the Japanese we are knocking things off, they may be just that. The trucks don't look like KTM and they sure as hell ain't AN.

Jay

[sarge]

Jay, I'm starting to wonder whether this is early NJCB. Memory serves they did Geeps, the drives on many of their earlier locos were all almost-copies of A/N. I believe the builder was the same as for the earlier Alco Models in HO...

[Jay Criswell]

Sarge,

I think you may be on to something.

Jay

[R.K. Maroon]

I like to snag photos of models as they go by on eBay, but I checked my files and I don't have any photos of a NJCB GP-7 or GP-9. I don't have any memory of them offering one either, but I haven't been around the hobby all that long so there is much I am not aware of. I did find one NJCB diesel in my files, a Baldwin RF-16 sharknose:







Those definitely look like All Nation drives, so Sarge may indeed be on to something. This one cleary has a chain-drive tower on each truck. My unit has a frame-mounted tower in the center, as shown in the photos several posts back. The motor and tower on mine clearly match the photo in the US Hobbies flyer (also shown several posts back). So it could be that the modeler had some of the "cracked gear" problems on the axles that Allan is posting about and swapped out the lower drive. I have to say that the entire installation is clean, so if this one has mods they were very well done.

I will do a closer comparison with an All Nation drive as time allows and report back.

Jim

[Jay Criswell]

Jim,

The Sharks definitely are A-N drives.

Don't think so on the GP in question.

The sprockets on the A-N chain drive split before the axle gears normally. When the went to the chain/sprocket the removed a large portion of the sprocket hub thus weakening it to the point where early failure was common. I replace all the sprockets & remove material from the assembly instead of the sprocket. This helps with longevity of said sprockets.

Jay

[R.K. Maroon]

I thought I would update the progress on converting the USH/MG GP-7 from outside third rail back to 2-rail. Installation of all-wheel pickup wipers is complete:



A few things to note here. First, the black circle of paint in the middle of the wheel is residual. The locomotive arrived with the back of the wheels completely painted. I put the chassis on its back and ran the motor while scrapping off the paint with a straight-blade Exacto knife. A perfectionist might have removed it all but it's a bit of work and I had eight wheels to do. There was some fine corrosion down in the machining grooves of the wheels so after paint removal I dressed these with fine carborundum paper. I used a drop of oil on the paper, which makes an easier cut and also helps with dust.

Also note the steel wheel rim on brass core. Not seen that before on wheels this small. Also surprising that the rims are so thick. Or maybe it's an illusion because I am looking at the backside and the wheel tread is tapered.

Next, note the slide switch off to the left. There was one installed on arrival for reversing locomotive direction (I guess the OTR system was constant polarity). There was a spot on the other side for a second switch, so I installed two new switches as headlight cutouts. I am installing constant-brightness directional headlights and wanted to be able to MU this with its matching unit and have full headlight control.

Finally, note that the wipers, which come from Rod Miller, are attached to Garolite, which Jay was kind enough to recommend.

One question: Is it a good idea or not to put a small drop of light oil on wipers? I was surprised when I first read the recommendation (on the LaBelle bottle) to lubricate motor brushes. As oil is used to suppress sparks in power line AC distribution switches, I would have thought it an insulator and not the thing to put on brushes. But it works (and the motor indeed runs more freely), so what about wheel wipers?

Jim

[sarge]

Moisten (not "soak") a cotton bud with Wahl and wipe the inside of the wheel. The tiniest bit is my recommendation; too much and a dirt magnet.

Sparks suppress and the pits won't start, especially if to be run on DCC.

Argument might vary about dry vs. ever so slightly oiled; I'm up for "ever so slightly oiled"- Grin!

[prrjim]

I have an original MG SD9 and it has the same gearboxes. This predates NJCB by about a decade I think. I think those gearboxes were original MG that may be a copy of AN gearboxes. They do run smoother and quieter than my AN switchers.

I also 2 MG GP35s. They have fabricated brass closed gearboxes. However they are similar in shape. Both the SD9 and the GP35s are built basically the way the GP7s is shown with the plate frame. I think that mechanism is original but has been worked on over the years with some adjustments but no major mods.

ON GP7 vs GP9, another spotting feature was the louvres on the long hood doors as built. All the models illustrate the as-built GP7 configuration with a lot of plain doors in the middle. the GP9s came with louvres along the middle of the long hood making lettering more of challenge. I imagine these doors could have been swapped around during major shoppings.

[milepost57]

I am not sure what that thin orange colored line is on the backside of the wheel.
it may be insulation, if so then your wipers look to be very close to bridging the gap.

[R.K. Maroon]

I am not sure what that thin orange colored line is on the backside of the wheel.
it may be insulation, if so then your wipers look to be very close to bridging the gap.

Hmm…Interesting question. As it is, I left on travel yesterday and cannot inspect the unit to see if there is something there or if it is an artifact of the photo. If there is some insulation there then we can be sure that all the wheels can't have it, as the original model did not have wheel pickups and there would be no way to get power off the rail to the motor. And I do know that all the wheels have the brass-steel combination. So the question is whether half of the wheels have insulation at that interface or, again, whether this is an illusion of the photograph. Unfortunately, it will be a week until I am back home and have an answer.

Jim

[prrjim]

I think all of my MG diesels have the wheel insulation at the hub. Basically the insulated wheels have a larger dia axle hole and an insulator is used as a shim.

Also, all of them had 4 wheel pickups through the wheels and axles. One or both trucks were insulated from the body and were opposite polarity. The had insulated wheels on one side on one truck and the other side on the other truck. I can't remember whether the pickup was through the mounting screws or with a screw on the truck.

[jwmathews]

Re the motor; that's a US Hobbies motor, possibly a U-79 but I'm not sure without measuring. Most Max Gray steam locos had wound-field motors, originally with hand reverse levers under the cab roof. I'm not familiar with MG diesel drives.

When Levon Kemalyan began importing KTM locos ca 1966 after MG died in May 1965, KTM made permag open-frame motors for their steamers. The smaller one was # U-79 with a field length of 0.890 inch. The larger motor was the U-80 with a field length of 1.265 inch. Both mootors were 1.915" wide. Both are shown in the catalogs as single-shaft with the shaft on the "front" end of the motor, away from the commutator/brush end. I think they could be supplied with the shaft on the brush end if so ordered, however.

The earliest USH mailing I have dates from about March, 1967. Photos from 1967 mailings show an SD-9 and a GP-35 with motors visible in their cabs, so that could well be an original motor arrangement. At that time, the U-79 motor was listed as DV-320 and the U-80 was called a DV-330. An even larger motor, the DV-4000 had been discontinued. Its magnet was 1.69 " long with a shorter shaft; otherwise the same as the other two.

In later years when US Hobbies imported diesels, narrower motors were supplied. The catalog numbers were U-186 and U-187, with 1"-long fields, identical in size except that U-187 had a double shaft. The width of both motors was 1.425 inch. These were made to fit low in the carbody with the 2-shaft motor driving both trucks. The U-186 could be used with a tower transmission for diesels & was also used in smaller steamers, such as the UP 2-8-0.

All these motors had sleeve bearings with oil holes & cloth wicks to hold oil around the bearing. Occasionally there might be quality control problems, such as a loose wire between commutator & armature, but I think they were generally well-made, sturdy products for the open-frame era. My thought is: "If it ain't broke, don't fix it!"

One tip about wheel or axle wipers: To make them last longer, put a blob of solder on the contact point. or even better, solder a piece of brass bar where the wiper bears on the wheel or axle. Wipers are a great idea to improve reliable electrical pickup.

Re the NJCB diesels, those did use A-N drives. NJ stood for Nick & Jack, the two partners who owned NJ International/Custom Brass. One thing about the Shark trucks; they have friction journal boxes, which is incorrect. Roller bearings were standard on those. I have an A-B set, & purchased R-B box covers from PSC. Grinding the factory boxes flat is a lot of work & I think it might be easier to build up the original boxes with epoxy to attach the R-B covers. Thoughts on this subject from others will be welcomed.