Mantua 4-6-2 questions

It's a fairly good representation of a USRA light Pacific. As such, it can be adapted to make a more or less accurate model of a variety of prototypes. The devil's in the details - there aren't nearly as many steam loco details available now as there were a couple of decades ago. However, real hobby shops tend to hold onto old, outdated stock, knowing that eventually someone will want it, so hie thee to the nearest one and sniff around. Good hunting!

The mech is barely acceptable by today's standards IMO, but can be run-in to operate quite smoothly. The weak point is the nylon worm (if that's the version you have) - nylon doesn't wear in the way metal does. So if you remotor, also get new gears - if memory serves NSWL makes a complete motor + gears replacement kit.

HTH

Aren't they all? One source says: "Davy Cormack feels this model is actually based largely on the B&O P7 class Pacific of 1927, the so-called "President class" since they were named after the first presidents. Cormack said the 20 locos of P7 class was very similar, but not identical to the USRA heavy. The cab and tender of the model don't match, as well as a couple of details on the boiler but the boiler is 90% correct. He said the model appears to be based on P7 no. 5314 as she was after initial rebuilding in the 1940's, including the use of 80 inch Boxpok drivers. Other P7 locos had a mix of driver types in later years. Nos. 5314 and 5316, for example, had Boxpok, while others such as nos. 5309, 5315, and 5312 had standard spoked drivers."

Interesting comments. However, since the Mantua Pacific has been used as the basis of a reasonable stand-in for the CNR Pacifics, I don't think "heavy USRA" is correct. Was the B&O President class based on the USRA design(s)? A lot of engines built the 20s/30s were copies or adaptations of the USRA designs, or so I've been told. And the USRA designs combined the most common features and practices of then existing engines, so that they would be as "universal" as possible.

"Our model is a U.S.R.A. Light Mikado boiler, but we have fitted it to drives other than the Mikado to give the modeler a wide range of similar engines for his railroad's roster, with a family look. Our boiler is a smooth, clean, accurate die casting, fits the Mantua (Tyco) Mikado, Pacific, or Decapod drives. When ordering, please specify which drive you intend to use the boiler on, as the drilling for mounting holes is different. We have provided a drawing for making the running boards out of thin stock (stock not included), which mount on wires that pass thru the boiler. A lost wax brass smokebox front is included with the boiler. The boiler can be ordered completely drilled for mounting the parts in our Detail Kit #520, which includes basic U.S.R.A. detail parts used on U.S.R.A. engines as originally built, or the boiler can also be ordered undrilled, if you wish to arrange things the way you want them. Either way the holes for mounting the boiler on the drive are drilled and tapped. Detail Kit #520, which is available separately as well as other U.S.R.A. parts, is listed elsewhere in this catalog."

Big heavy hunk of metal: "I doan gotta show you no steenkeeng traction tires."

Also lots of detail parts:

The B&O P-7 was closely based on the USRA heavy pacific (e.g. Erie K-5, the only RR to receive USRA heavy pacifics), but was not a direct copy. The P-7 was slightly larger, to wit (read in 3 columns): Dimension(both as-built, from reprints of the RR diagram booklets)/K-5/P-7

Measuring my old Mantua pacific, the boiler diameters appear to be about 2 scale inches larger than the above dimensions. But that may be that (I believe) the diagram books give the diameters of the boiler itself, and not the boiler with lagging and jacket, in which case the model boiler may be a couple scale inches under size. Geezer

I used the Mantua as the basis for a B&M P4 kitbash. Turns out the Mantua model's important dimensions (length, height, boiler diameter) match the B&M prototype give or take a couple of scale inches. I had photographs and plans of the P4 and worked from them. The B&M didn't use Boxpox drivers and so I ordered replacement spoked drivers from Mantua (they were still in business back then) Calscale had a cast brass pilot that matched my photographs well, and a front deck air compressor shield that was close enough. A couple of features didn't get modeled. The B&M had a nifty teardrop shaped stack and a racy forward slope to the front of the cab. Both of these details fell into my "too hard" box, I couldn't think of any way to model them, so I just ignored them. With a nice paint job and speed lettering decals on the tender, the result was very nice, and was well received down at the club. A Boston area club full of knowledgeable old-timers, some of 'em old enough to have operated a prototype P4.

The stock Mantua drive and motor is very good, smooth, good low speed running. You won't be unhappy with it. I did a can motor conversion on mine, and a good mechanism became even better. Stock, the engine would run down to 4 scale mph. With the can motor, creep speed dropped down to 0.01 scale mph, it would creep along tie by tie. It runs better than any brass steamer I ever saw, and just as well as my Bachmann consolidation. The conversion is easy, just screwdriver work. Was it me, I'd try for a can motor conversion kit. Yardbird had two of 'em.

David Starr

Thanks, that clears things up nicely.

It also means that a CNR Pacific based on this loco would be somewhat oversize, but not objectionably so.

GG:

Don't remotor until everything is working with stock parts. I say this particularly as you are just getting back into this. I know from experience that if you try to do everything perfectly right away, very often you get bogged down. Therefore, I wouldn't go pulling axle gears or remotoring just yet. If and when you do remotor it, you want to have a decent-running baseline to compare to, with the bugs already worked out. Furthermore, if you evaluate the performance with the old drive, you know just what improvement has been made.

Depending on the motor, you may not even want to replace it. If it's a "Power Drive" version with a covered worm and chunky MG81 motor (DC71-like appearance, stamped pole pieces) the noise level and low speed performance shouldn't be too far below present-day standards, and at any rate your Mantua's pulling power is going to walk all OVER present-day standards. If it's a plain angle-mounted PM-1 (smallish open-frame with cast pole pieces) there's a stronger case for remotoring, but again, don't remotor until the engine is running and broken in.

Wolf is right that the nylon worm & gear are a Mantua weakness; Mantua was a pioneer in the use of plastic in model railroading, believe it or not. The first Booster design had a plastic frame...in the early 1950s, but it apparently was not successful. The plastic gearing was one of their ideas that worked well enough to keep, but probably shoudn't have. However, the Helix Humper has a brass worm, and works with the present axle gear, which does eliminate the problem of running nylon on nylon. However, as I said, don't worry about that right away.

As for detail parts, Bowser and Yardbird have a lot. A lot of steam detail can be made from wire or bits of brass, too, or scavenged from plastic models as John Allen was known to do. Again, I wouldn't worry about that until you've got a good-running engine.

Suggestions for kit assembly:

Mantua kits were very well-engineered, and I find that most parts fit properly. As with any kits, you should take your time, and follow the instructions. Remove flash from parts first, using files and perhaps an Xacto knife.

You may occasionally find flash in the axle-slot ends. Remove this carefully, but do /not/ file the inside of the axle slots. On some kits, I have lightly scraped the /top/ of the slot to ensure all drivers pressed on the rail evenly, as determined by pushing the chassis with fingers lightly braking the drivers, but Mantua has bearing shells located by pegs, so don't do this. You could perhaps add shims if needed, but as I said Mantua tended to have good fits.

Riveting the valve-gear together is not easy, but you've built kits before so you'll pick up the skill. Just be careful and follow the kit instructions. Bowser has a riveting tool.

Be sure to adjust the worm-gear mesh, as recommended in the instructions.

Look at the punched side rods. You will note a slight rounding on one side, which is the side that dropped through the die. It is best if you arrange the rods on both sides so that this rounded side faces the same way...i.e. both right or both to the left. This way, any inaccuracy in the pinhole spacing tends to cancel out.

Some modelers use Loctite on crankpin screws. I've never done this, but it sounds like it could be a good idea. Has anybody out there tried this? If I did, I'd use a removable, fairly weak grade.

You will note that the instructions recommend that you run the mechanism at frequent intervals. This is important. In fact, the assembled mech without its motor should coast very freely down a slight grade, almost like a boxcar. This is vital to a good-running kit loco of any brand, and it's one area where RTR manufacturers just can't afford to match your own efforts. My MDC 2-6-0 runs much better than the locos MR tested, and it's because I worked every bind out before going to the next step.

I don't want this to sound discouraging. Kit building is a blast,and it's not that hard. The only REALLY hard part is developing the patience needed to tell yourself "I will complete this step and this step only, and I will not ruin my work by rushing". I ruined several kits before I learned this lesson, and I'd like to save others the same problem -- but I'm sure you already learned it with plastic models, of which I probably ruined a dozen through haste and carelessness before I got one right...it was a 1957 Chevy, two tone green. I remember busting a lot of shirt buttons over that one, and it made up for a lot of my junkyard (but in retrospect, probably not for the 1970 MPC Popcorn Wagon kit that I tried to assemble with Elmer's glue and Seal-All. Oh, the humanity...)

Of course I promptly made the opposite error, and decided my next kit would be modified with sparkplugwiresandopeningdoorsandopeningtrunkand... you guessed it, it never got assembled. This is the source of another lesson - get the basics down thoroughly before attempting embellishments, and that's largely behind my comments about remotoring. I've had to learn this lesson many times, too; I am not by nature a patient person, but one who tends to rush and get discouraged quickly, unless I make a conscious effort to avoid it. Quite frankly, if I can do it, anybody can.

To be fair, these lessons which I learned at some cost to my finances and my ego have paid off very well in other areas. They made me much more careful when fixing the house and car, or even at my job, to always find instructions if possible, to always read the manual or standards, and to work slowly and carefully when encountering an unfamiliar system.

By all means, though, don't let me worry you. Too many people moan and groan about what they can't do, but never try. Even if you do ruin some parts, you can order new ones, right? If you have any questions, just ask.

Cordially yours: Gerard P. President, a box of track and a gappy table.

Some 35 years ago I did a conversion of Mantua 4-6-2 based on a CNJ G3 although the Mantua sand domes are wrong for the G3. The boxpox drivers were replaced with PennLine/Bowser 80" drivers..also Tyco valve gear hanger and crosshead were replaced. Stock Mantua motor gave way to Pittman open frame motor although do not recall which one. That motor was balanced and trued up with the result the loco would move out with 5 AHM passenger cars in tow at 1.5 volts.

For pix see January 1972 RMC,. paged 50-51.