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Boosted output from an amplified Mike...

..or to put it another way: how to boost the pulling power of the Athearn Mikado and improve its over-all performance. If this subject is of interest to you, please read through before starting: while not particularly difficult, it involves working with lead, so if you're uncomfortable with this, save your time. The gain is dependent upon addition of lead.
The first step is to disassemble the locomotive, making notes and/or sketches as required, to aid in re-assembly. First, disengage the boiler braces from the sides of the smokebox, then remove and discard the long screw that goes up through the cylinder block. Remove the damper control from the engineer's side of the smokebox, too.  Disengage the lower ends of the cab handrails, and then, using a small flat screwdriver, carefully spread, from the inside, the bottom front corners of the cab, and lift off the cab. Next, squeeze the lower rear end of the boiler between your thumb and forefinger, in order to disengage the tabs that protrude through the firebox, then lift. Continue lifting the rear of the boiler until it is high enough to clear the top of the motor (this is a tight fit). Now slide the boiler forward until it clears the front of the main boiler weight, and set aside. To remove the weight/motor/idler gear unit, remove the screws, as shown below, from both sides of the boiler weight (above the lead driver), and the screws from the motor terminals (bottom rear area of the motor). Lift off the entire assembly, feeding the "pigtail" through the slot at the rear (the small circuit board on the end of the pigtail must be removed to obtain enough clearance).


Now, slide the running board/lower boiler assembly to the rear, until the protrusion on the chassis is clear of the slot in the lower cab backplate. Lift off, and set aside, taking care to not lose the screws.
To disassemble the weight, remove the three screws (and nuts) as shown in the photo below. Don't lose the plastic spacers from between the halves of the weight. Carefully separate the two parts of the weight: the motor and driveline should stay together with one side or the other.


If you are using DCC, or want working lights but don't wish to rewire them, skip this step. I feel that the "pigtail" adversely affects the tracking qualities of the tender, so I remove it. To do so, strip the heat shink tubing from the wires and cut the Red and Black wires near the circuit board. Unsolder the Grey wire from the upper motor terminal and replace it with the bare end of the shortened Black wire. Repeat this operation, using the shortened Red wire to replace the Orange wire on the lower motor terminal. On re-assembly, the brass terminal connectors on the other ends of these wires will be screwed on at the rear of the motor as before, Red on the right (engineer's side), Black on the left (fireman's side).
Mark the top of the motor, and note the placement of the worm bearings and the idler gearbox. Remove the motor/flywheel/worm/bearings as a unit and set aside. Remove the idler gearbox. Wipe the stripped-down weight halves of excess grease and oil.

Using a suitable square, and working on the inside face of each half weight, project a line from the forward face of the gearbox protrusion up to the top edge of the weight, then carry this line onto the outer surface of the weight.


Using a suitable straightedge, line it up with the top edge of the two bearing retainer slots machined into the casting. Scribe or mark a line from the previously scribed vertical line, forward to the end of the flat surface. The arrows on the photo indicate the bearing slots.


Scribe another vertical line mid-way between the hole for the front screw/spacer/nut and the square depression machined into the bottom of the weight, which accepts the mounting protrusion that extends upward from the chassis. This line represents the first cut, which will remove the shaded area in the photo.


Using a hacksaw, make the first cut, removing the front of both halves of the weight. Next, cut along the two lines to remove the shaded area, then clean up all cuts with a mill file.


The next photo shows two modified halves at the top, with two unmodified half-weights below.


I removed, using the same techniques, an additional small amount from the stock weights, as shown by the shaded area.


The stripped-down stock weight weighed 5 1/4 ounces, while our cut-down version tips the scales at 3 1/2 ounces, a net loss of 1 3/4 ounces.

Now we need to make new weights. I use old wheel balancing weights, obtained free from a local tire shop. Using a suitable metal container and a propane torch, you can melt the wheel weights, which will allow the steel clips and dirt and impurities to float to the surface of the molten lead, where they can be removed. First though, we need to make some moulds. I used .015" sheet aluminum (scrap aluminum siding will also work: make sure that the painted side faces out).


These are simple tubes, held together with soft steel wire. The inserts (one per tube) are to provide a rough profile of the "step" required to nest this casting into the end of the modified stock casting. Cut the curved end to match the diameter of the tube: the other end is pinched over, as shown on the upright mould to the right side of the photo. To pour the weights, the moulds should be standing, as shown, on a metal sheet.
When handling the lead, do not eat, smoke, pick your nose, or in any other way ingest lead residue from your hands. Always wash your hands thoroughly after handling lead and don't leave it where children or pets can come in contact with it. I always wear a two-stage respirator when melting and pouring the lead, although workers that I spoke with at a lead casting factory assured me that no harmful fumes are released when lead reaches its melting temperature. At higher temperatures, lead vapours are released and are very harmful to breathe. (I worked in a steel mill where we occasionally rolled a grade of steel with a high lead content: breathing protection was required, as the rolling temperature was 2350 degrees Fahrenheit, and the sweetish smell of the lead vapours was everywhere).
When the lead is molten, and the impurities have been removed, gently pour it into the upright mould. I hold the mould with a pair of channel-locks to prevent tipping. Make sure that you have enough lead to fill the mould in one pour. If some slops, or if you accidently overfill the mould, don't worry: you can go back after the mould is filled and play the torch flame over the offending mess and it will soften and drop off. Make sure that the lead has cooled (this takes more than a couple of minutes) before removing the mould. The insert may need to be removed from the casting with pliers if there was leakage between it and the mould.
Now you need a coarse file to shape the rough casting: any will work, but I've found that the type used in autobody work is the fastest. Clamp the rough casting in a vise for this. You need to shape the back end of the lead so that it mates with the front end of the modified stock weight, and adjust the diameter so that the assembled pieces will fit into the plastic boiler casting. File and fit until satisfactory, then thoroughly clean the stock weights with soap and water to remove all grease, oil, and filings. Reassemble the motor/drivetrain assembly back into the modified weight, paying attention that the depressions on the edges of the plastic bearing retainers face to either side, with the protruding nubs oriented vertically, so as to be trapped between the halves of the weight. The plastic spacer with the smaller flange installs between the halves of the weight at the upper rear of the motor.
I also cast small lead weights that go on top of the frame just behind the cylinder casting and another that fits into the cylinder itself. These, as well as the large lead weight, are insulated from the frame with electrician's tape.


Also shown in the photo above are the new air tanks: these are pieces of brass tubing, filled with lead, and fitted with brass mounting bands.
The first step is to remove the plastic air tanks. I used a utility knife for this, as the mounting lugs cast onto the boiler shell are fairly heavy.


Next, we need to remove the cooling coils, complete with their mounting pins, from the air tanks. Some of the ones on my locos simply pulled out, while others required that the tank be carved away from them. This photo doesn't show it very clearly, but the knife is used to remove a wedge of material from the air tank, with the mounting pin in its middle, then the excess material is trimmed away from the pin.


Some of the cooling coil mounting pins fit into bosses cast on the underside of the running boards. We need to remove part of these in order for the new air tanks to sit snug against the underside of the running boards and we also need to retain part of these bosses for re-attaching the cooling coils. In the photo below, the chisel blade is cutting down along the curve of the boiler, while the other blade is cutting on an angle towards it. The piece between the two blades is to be removed, then the back end of the remaining piece carefully trimmed until the new air tank will lie flat on the underside of the running board.


Below is a view of the new air tanks, ready for installation. I used brass wire, inserted into holes drilled in the back of the tanks, as mounting pins, pushed into appropriate holes drilled in the boiler, along with some epoxy where the running board meets the boiler. The slots, cut into the two front air tanks (using a cut-off disc in a Dremel tool), are for the cooling coil mounting pins that were cut free from the tanks earlier. The mounting boss that was trimmed in the previous step can be seen, in the second photo below, to the left of the brass tank on the right: the mounting pin of the cooling coil will be epoxied into it.



The balance of the loco work involves reassembly and, if you wish, detailing, paint, etc. I also modified the tenders to pick up current, using trucks from the Bachmann Consolidation. To use these trucks, the mounting bolsters on the Athearn tender need to be cut down enough so that proper coupler height is maintained. I set mine up so that the rear truck picks up from the right rail and feeds to the right (Red) terminal on the motor, while the front truck picks up from the left rail and feeds to the left (Black) terminal on the motor. If you've retained the pigtail and circuit board, you'll need to figure out where to connect the wires, which may make separation of the tender from the loco difficult. I used a two conductor mini plug between the loco and tender, which works well for my unlit, DC powered locos.


The stock Athearn Mikado, loco only, weighs 12.5 oz., balanced at the rear of the third driver. The modified Mike weighs 16.75 oz. (later increased to 17.5oz), balanced at the mid-point of the driver wheelbase. I have removed the overly strong spring from the trailing truck, as this tends to shift the balance point too far forward. I may experiment with the spring reinstalled, with more weight added inside the cab. As it stands, the added weight, along with the shift forward of the balance point, has greatly increased the pulling power of these locos. I operate them as pairs: two will handle a 13 car coal train (100 oz. weight) up the 2.8% ruling grade on the subdivision or will pull a 24 car merchandise train up the same hill. The grade is laid out on a 34" radius "S" curve, with the distance between the curves shorter even than the length of the 13 car train, so the effect of the grade is compounded by the curves.
Here are a couple of builder's photos.



And another of two of them in service at Lowbanks.

And finally, a shot of the 636 at speed, near Airline Junction, on the Grand Valley.


I hope that some of you have found the foregoing to be of some use or interest. Your questions and comments are welcomed.
Wayne, looks excellent. These Athearn mikes got a bad reputation, because of pulling power and cracked axle gears. I an not a big fan of split-axle designs, especially on steam locomotives, but i guess they are ubiquitous these days.

About your lead casting- I save tire weights that I find in the street. I have melted a bunch down into large "ingots" that I eventually will use for something someday. Have you ever poured generic segmented weights similar to the "stick on " type found in hobby shops? I was thinking of making a reusable mold, and then attaching double sided tape to the finished lead. I haven't tried it yet, but was hoping someone may have tried something like this before and could give me a few dos/don'ts for this process.
Thanks for recreating this Wayne! Excellent description and photos for those wishing to upgrade... Thumbsup Thumbsup

okay so I guess my only question is: should I assume that you replaced the front portion of existing weight in the boiler with your own weight as yours was heavier that the factory one? I hate to assume as you know what often happens when you do.
Kevin, I was certain that I'd posted a thread on casting lead weights either here or at Zealot, but I can't seem to find it. I'll keep searching and, if I don't find it, make up a new one, as I do know where the pictures are. Wink Goldth

bob_suruncle Wrote:okay so I guess my only question is:  should I assume that  you replaced the front portion of existing weight in the boiler with your own weight as yours was heavier that the factory one?  I hate to assume as you know what often happens when you do.

A safe assumption, uncle Bob, and correct for the assumed reason, although that's just my polite way of saying that I was really just too lazy to re-cast the entire weight in lead.  Wink  Misngth
The density of lead is greater than that of the cast Zamac weight that's included with the loco, and while not substantially greater, I also increased the size of the main weight by eliminating the circuitry for the headlight.

Anyone wanting to improve any loco's pulling capacity, steam or diesel, could use some or all of these techniques.
I modified three Athearn U-boats by ballasting them to just over 33 oz. each, using custom-cast lead weights to almost totally fill the body cavities.  All of the locos on my layout have been modified in this manner, to some degree, as I expect them to be able, either alone or in combination with other locos, to move specified amounts of "tonnage".  

nachoman Wrote:About your lead casting- I save tire weights that I find in the street. I have melted a bunch down into large "ingots" that I eventually will use for something someday. Have you ever poured generic segmented weights similar to the "stick on " type found in hobby shops? I was thinking of making a reusable mold, and then attaching double sided tape to the finished lead. I haven't tried it yet, but was hoping someone may have tried something like this before and could give me a few dos/don'ts for this process.

Kevin, while I haven't cast segmented weights, there's a thread HERE on making simple re-useable moulds.

Hi Doc---great "how to" thread on the conversion---here's a couple of examples of the end results

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Quote:The stock Athearn Mikado, loco only, weighs 12.5 oz., balanced at the rear of the third driver. The modified Mike weighs 16.75 oz., balanced at the mid-point of the driver wheelbase.
I suspect that more than the added 4.25 oz. the moving of the balance point forward of the third driver, was the significant factor in getting better pulling power.
Either way, this is a valuable "how-to"! Thanks!
You're right about that, Pete.  Balancing the loco while maintaining the stock weight would have been preferable to simply adding weight, but still leaving the loco unbalanced.

The loco shown below, belonging to my good friend Mister Nutbar, was severely back-heavy when we first got it, mostly due to the extremely large can motor used to re-power it.  While I didn't think to weigh it before doing the conversion work on it, I knew that it would need to be balanced in order to improve both its pulling ability and its tracking qualities, as the lead drivers actually lifted off the rails on some curves.  Eek

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The new cab, a cast brass one from Kemtron, made the loco even more back-heavy, so I cast a new main boiler weight for it, in addition to the lead-filled airtanks.  With the new weights installed, I found the loco to now be heavy in the front end.  Wallbang   While I could have added more weight inside the cab, in order to achieve proper balance, I felt that the motor was too close to its limits to make this feasible.  Instead, I trimmed back the boiler weight until the loco was balanced about the centre-point of the driver wheelbase.  With a weight of 32oz. (loco only) she'll handle the same 100oz. train that requires two of the rebuilt Mikados.

As usual you've done some fine work there Wayne. Thumbsup

Quite fascinating how adding weight to a loco will actually increase its ability to pull rolling stock. Are most steamers out of the box poorly balanced and under weight? If so, it makes me wonder why Manufactures have not done anything to address the issue. I wonder how many other owners of the "same" engines have these problems but don't have the knowledge or where-with-all to fix them. I wonder how many people get frustrated and just end up placing them in a display cabinet?

Some silly questions. In your opinion does the added weight create more stress on the mechanical parts and motor? By putting more weight on the wheels do you think that they may wear out faster? Or is it really a non-issue and that the benefits far outweigh any perceived risks?

My experience is limited. Even my little switcher can pull a string of over twenty cars with no wheel slip, so I am curious as to why I hear about this problem with regards to steam engines for the most part?
Thanks, Shane.  Wink   I'm sure that there are some steam locos available that will pull a decent train, but a lot of model steamers do seem to be out-of-balance and/or too light.  Some of their pulling ability is lost in the side rod and valve motion, too, and the larger diameter wheels, just like the prototype, are prone to slip more easily.  Another thing to keep in mind is that I'm doing this to make the locos suitable for use on my layout, which has a lot of curves and a lot of grades, most occurring at the same place.  I also like to run some heavy trains.  For instance, Mister Nutbar's 2-10-2 would be an excellent loco for my layout if it would fit on my turntable, but I doubt that its tractive effort will ever be put to the test on his own layout:  I don't doubt that it could pull a hundred normal-weight cars on straight, level track.
I have a Proto USRA 0-8-0 switcher that couldn't move four regular boxcars up the grade to my station at Dunnville.  It's a beautiful-running locomotive, but no "oomph".  I was going to get rid of it, but, fortunately, took it apart to see what the problem was.  I discovered that the cast weight (of a similar light material as that of the Athearn Mikado) had been cast to accommodate a circuit board for the headlight and a tiny flywheel, the mass of which didn't appear adequate to have any effect.  By replacing those unnecessary, to me, at least, items with lead, then adding more where space was available, I was able to double its tonnage rating to eight cars - good enough to make it onto the roster and merit a complete makeover, too.

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A good test when you're adding weight to any loco is to apply power to it while physically restraining it from moving - for a steam loco, simple hold the tender, while a car coupled to a diesel will serve the same purpose.  If the wheels slip, the loco is not too heavy for its motor.  If the wheels don't slip, the motor will continue to try to turn, with the result that it will begin to overheat.   If it gets hot enough, the insulating varnish on the motor windings will melt, damaging or destroying the motor.  Many locos can handle much more weight than would be possible to hide within them, though.
Unless there's a flaw within the drivetrain (such as split gears) the added weight is unlikely to cause added strain to either the motor or other mechanical parts.  Excessive wheelslip can, however, wear away the plating that's found on most loco drive wheels, so, while it's good that the wheels are able to slip when the load is too great, it's best not to tax your locos to that point.

I think that for most modellers, though, the pulling ability of a loco is not high on their list of requirements.  So, if it runs well and has the details and other features that they want, it's probably "good enough" as it is, right out of the box.
This, of course, makes my thread here something of limited interest for most.  For me, though, it's an integral part of the way I do model railroading.  Wink  :mrgreen:

Great thread Wayne. I have saved it to a folder in "my documents" so that I can easily bring it up when I do a similar job on my Athearn "mike." I have found that the stock Athearn wheel treads are so slick that they pull terribly "out of the box." After being run a while and allowing the drivers to slip, the pulling power has improved. When I first tried it out, I could not pull more than 6 cars. It now pulls 10-12 cars without too much trouble, but a mike ought to be able to pull at least 15-20 cars on level track.
Very well documented Wayne, I have a couple of my steam engines that need to be modified for better pulling power.
Thanks, guys: it's very satisfying to know both that the information is useful, and that people are willing to modify the techniques to suit their own particular purposes. Please feel free to add information to this thread as you see fit.

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