So I am trying to finish a Roundhouse SP 0-6-0 that dates from probably the late 1970s: plastic boiler shell, but open frame motor. I have the mechanism working perfectly, but for some reason, it stops dead once the boiler shell is in place. I thought at first that the weight might be rubbing against the worm gear, so I cut the weight back, but the problem persists. I think it MIGHT be the boiler shell pressing the motor brushes against the armature, so that they act like brakes, but before I try to file the shell, I thought I would see if anyone else has ever had this issue.
i love the Roundhouse kits, but honestly, they can be such a chore…
There are four versions of the MDC 0-6-0, what motor did it come with, DC70 or DC71?
The open frame motor (versions 1 to 3, 50s to 80s) have an adjustment screw to adjust the worm to axle gear alignment. Tightening the bottom screws can apply a downward pressure binding the worm to gear adjustment. If the motor draws current and the wheels don’t move check the adjustment screw.
If the motor doesn’t draw current a common problem is the wire going to the motor brush can be moved when the boiler shell is installed causing the brush to not make contact to the commutator. Make sure the wire is clear and not touching the boiler.
I’m not familiar with that particular locomotive, but I’ve seen several where putting the boiler in place either touches a motor brush directly or, when the wire to it is too stiff/heavy and the inside of the boiler touches it. In both cases, the result is that the brush is lifted, losing contact with the commutator.
Depending on the internal set-up, perhaps the weight is touching the motor and simply creating a short.
Does the motor turn without the boiler attached to the loco? Does your powerpack indicate a short when you put the engine on the track? I assume this is the tank engine. If not, are you sure the wiring for the tender is ok?
After a bit of thinking I remember that I replaced the brush wire with a more flexible wire. I remember the motor came prewired with a short about 20 gauge wire that was fairly stiff. From your description I think your problem is the stiff wire touching the boiler wall and moving the brush away from the commutator.
I can’t remember any problems with my original locomotive, it’s been awhile since I first assembled it. My first HO locomotive is a 63 year old one owner MDC 0-6-0 switcher locomotive with a slope back tender. I bought it with paper route money in 1952. I’ve overhauled is several times over the years and it still runs perfect.
I recently found (August 2013) an early MDC 0-6-0 (all metal 1952) unbuilt kit on eBay, I wired it for DCC operation using #28 decoder wire with the decoder installed in the tender. If the DC70 motor rotor stalls the decoder is toast, locked rotor current is 1½ amps.
This is the tender engine, with a DC-71 motor. The wire connecting engine and tender is soldered to the top and runs directly back, so I am pretty sure it’s not fouling the brushes, and I cut the weight back, so I know that’s not fouling the worm gear. When I remove the plastic boiler shell, it runs perfectly. When I put the shell in place, it runs perfectly- until I try to snug the boiler down. Then it won’t draw any current, until the boiler is removed. Is it possible the boiler shell is forcing the brushes against the commutator, and stalling the motor?
If I remember right, there is a wire that needs to run near the bottom that was almost over the motor, think I got thinner longer wire and ran it a different way.
If the motor doesn’t draw current one the brushes is not touching the commutator! The boiler shell is pushing the top of the brush in forcing the carbon brush away from the commutator.
Try to resolder the wire on the inside of the brush and keep it as small as possible. It only has to move away .001” to break connection.
In the photo Mel has supplied, the photo identifies a DC 70 motor. It is not. It is a DC-60. The DC-60 had its brushes mounted near the magnet, as shown. The DC-70 had them near the front bearing.
The other motor may or may not be a Pittman DC-71. It looks a LOT like one, except the brush spring arrangement is not typical of a Pittman motor. I offer that it MAY be a copy.
It’s my recollection that, in the “olden” days, some manufacturers would use Pittman motors until they found someone who would supply cheaper motors. It would have been tempting if a company was actually trying to turn a profit.
I would agree with you ED except that the motor labeled DC 70 1951 is the original MDC motor and the Instruction sheet from MDC dated 1951 calls it a DC70. I bought the MDC Kit new in the box from H&H Hobbies in El Paso Texas in 1952. I also think the MDC instructions are incorrect but not knowing positively I labeled my picture per the MDC instructions.
I replaced all of the insulators on my Pittman motors, that’s why they look different. I bought the Pittman DCC brush insulator conversion kits from Bowser. Bowser claims to have purchased the Pittman dies for the DC60/70/71 and still sell motors an
I did not know that there were still leftover Pittman motors. I wandered around the Bowser site and found the page you mentioned. I see the photo of the DC-71 shows a skew wound armature–something I don’t recall ever seeing in the Pittman line.
I do really wonder about that DC-70 in 1951. It’s my impression that they were introduced in the late 50’s, thus being unable to be referenced in 1951. Curious. Curious.
I do note that MDC catalogs from 1949 to 1973 all say the 0-6-0 came with a DC-60. I suspect you have found a misprint. And, of course, you HAVE a DC-60.
The catalog also mentions a 35:1 gear reduction. Very nice, in a switcher!
I am surprised that a DC-71 would fit in that little switcher. I repowered a brass 4-8-4 with one, and it was a boiler-filler. And a darn good motor. Still is.
Those MDC switchers were really neat, for their day. I wanted one, myself, back then. Well, and everything else, to admit the truth.
I had an old Varney from the early 50s and it had a DC70. The only locomotive I”ve ever seen with a DC60 is the MDC 0-6-0, I had a 0-4-0 Yard Bird from the very early 50s that had a DC70 in it . . . . you talk about a tight, fit that was for sure.
My Penn Line 2-8-0 came with a DC-60–something an SP modeler would likely have missed. So did their 4-4-2 and Whitcomb switcher. The Varney 4-6-0 also had a DC-60 in 1950, according to the instructions. As did their Dockside and their NW2 and F3.
I also had a Varney Dockside but didn’t remember which motor it had. When I got married in 1958 I left my railroad stuff at my folks house for several years and my 9 year younger brother dinged and lost all kinds of stuff. Several Varney locos and a 2-6-2 Mother Hubbard, unknown manufacturer. The only reason I still have my MDC 0-6-0 is that I took that one with me.
