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 Posted - October 28 2009 : 3:48:02 PM
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Some time ago, I came into the possession of a Revell SW7 in good shape.
The seller stated that the motor ran, but the loco didn't move. $5 later it was mine.
So I took it home (got it from a local), and tore it down with the help of the diagram found at the tyco-trains site. Interesting, to be sure. It went together like an old Mantua - straight-head screws hold everything together.
The motor ran, for sure. I was sure I'd seen one like it before, though. Sure enough, it's near identical to the Athearn Hi-F rubber band drive motors as found in 50's vintage F7s and GP7s. Some commutator cleaning, bearing lubrication and brush replacement later, it ran smoothly and quietly.
I found out why it didn't move - the rubber band had completely disintegrated. I looked all over the parts box to find a rubber band of that size - and wound up using a traction tire off an old Bachmann 0-6-0 driver. Hey, no cracks, and it works.
I reassembled everything with fresh lubrication and cleaned the brass wheels, then plunked it on the track for a test run. Hey, it's running, but not moving - oh, there it goes. Guess that's how that "clutch" works.
Except that the clutch is pretty worthless. Hook the loco up to a cut of more than 3 cars and it'll sit there and not move - nice "throttling" sound of the motor, though, if it's at almost no throttle, it kinda sounds like a diesel prime mover.
I took it all apart again and disabled the clutch by drilling small holes in the clutch housing and "pressure surfaces", then attaching them with screws. Nice, solid mount now.
Surprise - she's a quiet smooth runner, almost the equal of a bluebox SW unit in power and noise - better than a Bachmann or Tyco PowerTorque motor, for sure.
The shell, although stated to be an SW7, is actually a Phase IV NW2. The short front grille and single light is the giveaway.
Mine was decorated as an ACL purple and silver unit. I stripped it in Castrol SuperClean to remove the factory paint. I then altered the step-down of the hood in front of the cab to reflect the earlier phase units. My goal is a Phase III NW2 which the shell is spot-on for, except the step-down.
Once this was done, I fashioned full sill handrails and removed the hood side railing. I painted the unit in CN black and orange and added aftermarket exhaust manifolds.
Pics to come soon. Needless to say I love this unit - it's as prototypical as it gets, having been rebuilt from an original 1957 model and still in service 52 years later.
Kris Carver-Seaboyer
Modelling the Grafton Terminal Railway, set in New Brunswick, Canada in the 1978-1984 time frame
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Posted - October 28 2009 : 7:34:09 PM
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quote:Some time ago, I came into the possession of a Revell SW7 in good shape.
The seller stated that the motor ran, but the loco didn't move. $5 later it was mine.
Originally posted by graftonterminalrr-October 28 2009: 3:48:02 PM
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I like the way you think. Sounds like my kind of project. I keep telling myself : I'm not going to buy any more derelict locomotives. But, I buy them anyway.
Unspoken expectations are premeditated failures.
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Posted - October 28 2009 : 7:49:43 PM
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I find rebuilding motors and drives to be just as fun as running the locomotive itself. 
    
- Matt -
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Posted - October 28 2009 : 8:07:19 PM
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quote:| I'm not going to buy any more derelict locomotives. |
 hey I PREFER that type of locos & cars I buy a loco IDC if it works or not I got a friend who can help me Anyone got any?
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Posted - October 28 2009 : 9:14:11 PM
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| I specifically look for locos that don't run. They're cheap, and usually they can be repaired with minimal effort. See my post in LOTW for a great example.
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Posted - October 28 2009 : 10:41:39 PM
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| Curses! I've long been intrigued by a Revell SW7, but had too many other novelty engines. Even trying to thin a few back. But now after hearing about this clutch, I'm intrigued again. I love a nice growly motor. DCC sound is cool but there's still something authentic about a mechanism's own song.
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Posted - October 29 2009 : 06:48:40 AM
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Ain't it the truth. It's really quite interesting from a technical standpoint - the motor drives a small, cast-metal flywheel in which is mounted a clutch, which actuates when the motor's got enough speed. This in turn drives a belt pulley to which is mounted a small rubber band. The rubber band drives a pulley attached to two worm gears which drive the axles a la the MDC Boxcab/Climax.
It's got character - no denying that.
I've got it semi-permanently coupled to a 1950's vintage Athearn GP7 that I chopnosed and removed the DB blister from.
Like I said before - completely prototypical. 50+ year old models still in service, heavily rebuilt but reliable.
Kris Carver-Seaboyer
Modelling the Grafton Terminal Railway, set in New Brunswick, Canada in the 1978-1984 time frame
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Posted - October 29 2009 : 08:48:11 AM
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I've always wanted to take a crack at one of these clutch drives, but I've never seen one at a train show.
The Tyco Depot
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Posted - October 29 2009 : 09:47:24 AM
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You can find them on Ebay, for sure. I've seen SW7s (NW2's, actually) and F3s here and there.
One thing I have to comment on, though. The F7 and SW7 shared rubber-band drive components, but the 0-6-0 and 0-4-0 had the motor run a worm that drove a gear. Therefore, the average Revell F7/SW7 will probably need a new rubber band to run, but the steamers usually run after a wheel cleaning.
Kris Carver-Seaboyer
Modelling the Grafton Terminal Railway, set in New Brunswick, Canada in the 1978-1984 time frame
Edited by - graftonterminalrr on October 29 2009 10:08:56 AM
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Posted - October 29 2009 : 09:55:07 AM
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| Huh. I have a Revell F7 that looks gorgeous and runs beautifully, but I never noticed any drag from a clutch. I do recall it making a unique noise, which was the primary reason I kept it. From your description of the SW and my experience with the F I was thinking they might have had different drives. I'll have to investigate it more closely...
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Posted - October 29 2009 : 10:08:17 AM
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Well, if you have the Revell F, you have the SW7 with a different shell and frame. The motor is the same, as is the clutch and worm gear (I believe).
Interestingly enough, NWSL still offers replacement wheelsets for these locomotives.
EDIT: Revell changed their drive systems around 1960 to a drive almost identical to the Varney F3. My SW7 has a 1957 copyright date molded into the truck gear covers.
*exact wording:
(c) REVELL INC. 1957 2
3994-004
Therefore, the earlier drive is different and sounds 1) more expensive to produce and 2) more powerful.
Prior to "fixing" the clutch drive, I would notice that it wouldn't engage until almost 3/4 throttle. Turn on the juice and you get a satisfying growl under the hood, but when the clutch kicked in it shot off like a rocket.
The clutch is a centrifugal clutch. I'll try to explain it as best I can.
Imagine a brake drum. Now shrink that brake drum to the diameter of an HO scale diesel drive wheel, and cut the drum sides to about 3mm long.
The drum has some tabs on the bottom "flat side" that correspond to holes in the cast brass belt pulley. The motor shaft runs through the drum, but the hole in the middle is just large enough to allow the brake drum to spin freely without wobbling.
The "brake drum" is the clutch housing.
Now, let's look at the flywheel. It's a cast piece of zinc that has two little tabs molded onto the side facing away from the motor.
These tabs are locating tabs for two semicircular pieces of styrene plastic shaped roughly like brake shoes. They are not attached to anything, but the tabs serve to limit the shoes' movement inside the clutch housing.
Now, imagine two small metal triangular pieces that dont attach to anything - they free float inside the clutch housing. These pieces ride between the styrene "brake shoes". The clutch housing fits over the whole works.
What happens is, the motor shaft and flywheel spins up when current is applied to the motor. The brake shoes and triangular pieces spin too, but the clutch housing does not spin because it is attached to the pulley/belt/worm/wheel assembly. There is insufficient friction as of yet to lock the spinning styrene brake shoes to the stationary clutch housing.
As the motor increases RPMs, centrifugal force causes the heavier metal triangular pieces to push against the styrene brake shoes, increasing pressure on the clutch housing. Eventually, enough friction is created that the housing starts to spin, thus powering the wheels.
When the loco is coupled to a long string of cars, this clutch is supposed to have the effect of easing the train to a start. Think about it - most kids crank the juice right up to 12V right away and the train takes off like a shot. The clutch was supposed to allow the motor to spin up quickly but the train to ease away from a stop.
Doesn't really work that way, though.
Kris Carver-Seaboyer
Modelling the Grafton Terminal Railway, set in New Brunswick, Canada in the 1978-1984 time frame
Edited by - graftonterminalrr on October 29 2009 10:25:03 AM
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Posted - October 29 2009 : 12:24:34 PM
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I had a Varney F3 with an aftermarket "Jerry Martin Centriclutch"
It was fun to play with for awhile but I ended up removing the clutch and puting a large can motor in the F3.
Ray
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Posted - October 29 2009 : 12:53:40 PM
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Anyone runnning one of the Lindberg SW6/900's?
Interested in what your experience was...
-Gareth
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Posted - October 29 2009 : 4:46:05 PM
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Found this one for 5 dollars at a Greenberg show....used a rubber O ring for the drive....after I got it running I wasn't impressed.
BT
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Posted - October 29 2009 : 5:04:33 PM
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Yours is missing the light bulb, and seems to be the "economy" model (no handrails or number board).
As well, someone has replaced the headlight casting with a dual-bulb casting.
The O-ring was a good idea, but they're noisy aren't they?
Kris Carver-Seaboyer
Modelling the Grafton Terminal Railway, set in New Brunswick, Canada in the 1978-1984 time frame
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Posted - October 29 2009 : 5:35:32 PM
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never mind a bulb use a LED instead! I like the UP loco tho Taycotrains 
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Posted - October 29 2009 : 9:31:06 PM
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Nice loco for $5.
Is the hood that wide or is it just the angle of the photo?
I thought they were about the same width as an Athearn.
Ray
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Posted - October 29 2009 : 9:37:30 PM
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I think its the angle Ray.
BT
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Posted - October 30 2009 : 3:19:12 PM
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Boo, my F7 must be one of the later models. It has a powered rear truck with a pittman-style motor and stacked gears, similar to Varney/Life-Like. Driveshaft through the fuel tank gears up the front truck, but electrical pickup is rear only (which seems like a glaring oversight). Still runs MUCH better than other implementations of this design; the Life-like version is probably the worst piece of garbage I have ever seen in HO.
I'm going to have to keep my eye out for a clutch version, as I'm very intrigued by this. Are there spotting features to look for?
BTW I've always been amazed at the coupler deisgn - that spring and draft gear arrangement is again, needlessly complex. I'm amazed my example's was still intact, I bet those springs are among the first pieces lost since you have to remove the coupler to remove the loco shell.
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Posted - October 30 2009 : 3:29:04 PM
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When I got mine, adding Kadees was the first thing I did.
Amazingly enough, both couplers and springs were intact and worked very well. For an X2F, it probably had the best example of coupler return with juuuuust-enough tension to return the coupler back to its start point. A train of these would exhibit very little side to side skew due to side forces from the couplers.
As far as spotting featurs, I surmise that the shell would be unchanged, but looking underneath the unit would be all that would be necessary. look for a frame with two screws in the fuel tank (motor hold-down screws).
Kris Carver-Seaboyer
Modelling the Grafton Terminal Railway, set in New Brunswick, Canada in the 1978-1984 time frame
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Posted - October 30 2009 : 3:34:27 PM
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Here's the parts diagram to the original F7:
Here's an image of the later drive, reminiscent of the Varney F3:
Kris Carver-Seaboyer
Modelling the Grafton Terminal Railway, set in New Brunswick, Canada in the 1978-1984 time frame
Edited by - graftonterminalrr on October 30 2009 3:35:59 PM
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Posted - October 30 2009 : 3:37:14 PM
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Let's try that again:
Kris Carver-Seaboyer
Modelling the Grafton Terminal Railway, set in New Brunswick, Canada in the 1978-1984 time frame
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