Late last night Dr. Wayne provided responses on the Electronics and DCC Forum in a string entitled “How to Repair the Wiring Harness on a Athearn Genesis 282 Light”. In his last response he included a link to a 2009 spread that he did on 2-8-2 mods on the Bluetrains forum. As is all his stuff on behalf of the community, it is a masterful presentation, replete with photos and step-by-step instructions - including particulars on the casting of customized weights from scrap lead to maximize loco pulling power. He spoke of the importance of the engine’s weight being evenly distributed across the wheelbase of the drivers for best effect.
This piqued my interest immediately as I have two Genesis SP Mountains that likely will need the treatment once I generate enough courage to open them up. But I am a bit unclear on two points: 1) I presume that the balancing should take into account the entire engine upon its reassembly, and 2) what method and devices (jigs, etc.) are used in the balancing process?
I fully expect Wayne to chime in here - in spite of all the other stuff that he has to do. But I will also look forward to what other advice (and gizmos) come from the rest of you steamer mechs out there. Photos will be icing on this cake.
I’m not sure I follow you. If you’re talking about the lead and trailing trucks, they’re mostly decorative on a model. The balance point should be the middle of the driver wheelbase.
Place the locomotive on a “plank” that is strong enough to support it. Balance this assembly on a dowel or pencil. The balance point should be as mentioned above.
That being the case, if we had a 0-8-0 with center of gravity not over the midpoint of the 4 axles, let’s say towards the last axle, the forward axles would lose tractive effort and the rear axles would increase their effort and it would tend to come out near the same. Two caveats come to mind. If the drawbar to the tender started picking up some of the out of balance force, some of the loco weight would transfer to the tender for a net (tractive) loss. If nearly all the weight were over the 4th axle, it would be ok (if that axle not on an especially slippery area)?? I may be missing something here.
This would be complicated by:
a) one axle having traction tires, perhaps, where the friction factor for that axle is higher, so the more weight force there, the better. I’m assuming that the traction tire and bare wheels have equal radii and are touching simultaneously.
b) sprung drivers, but that might not matter much as long as none are bottomed out. While the axles with least spring compression would get less weight (downforce) the other axles would make up for that (the weight sum being the same)??
c) leading and trailing trucks. If the trucks had much stronger springs than needed to barely help them track adequately, they would be stealing weight (downforce) from the driven axles / wheels and reduce traction.
I’m thinking the keys are:
(a) the more weight, the more traction, and the center of gravity (if there are leading or trailing trucks) should simply be within the front and rear driven axles (more precise centering may not matter much), and
John, the loco is fully assembled for the balance test, even though the lead and trailing trucks have little weight to contribute and are mostly supported on their own wheels.
As Ed mentions, you can create a balance with a piece of wood and some dowel - I made mine from a sheet of brass, with heavy brass wire soldered across its balance point.
Even if the loco is picked up, with thumb and finger on the running boards in a light grip, and at the mid-point of the driver wheelbase, you can get a pretty-good sense of how well it is (or isn’t) balanced.
Prior to doing the modifications outlined in that thread, I placed one of those locos and its tender on the layout, then draped a “saddle” of folded sheet lead over the boiler, and while restraining the tender with my hand, applied power.
The locomotive attempted to surge forward, then immediately slipped its drivers, a sure sign that the weight was not too much for the motor to handle. As I recall, that “saddle” was well in excess of two pounds, and of more volume than could ever be fit into that locomotive.
If you have diesels and think that weight could help increase tractive effort, you can do a similar wheelslip test by coupling a car to the diesel, and holding it in place, as I did with the tender. Most diesels I’ve owned seem to have been pretty well-balanced, but I did add weight to pretty-well all of them…my layout is mostly grades and curves, usually occurring in the same places.
The Athearn USRA locos (Mikados and Pacifics) both came with springs on the trailing truck, and I think that its main purpose was an attempt to shift some of the imbalanced weight forward.
If you complete the outlined modifications, the spring should be removed - the truck tracks well without it, and leaving the spring in place will create another imbalance. I had intended to add more weight inside the cabs, and then re-install the springs, but I went on a bit of a tear a
In his presentation on Bluetrain, Wayne did mention that in doing his mods he had to replace trailing truck springs which effectively skewed the driver pressures so that they were unequal for each axle. With all the variables, not to mention the available spaces present in the boiler for additional weighting, it is all an exacting exercise in the art of physics. A few of us become as capable as violin makers, but most of us do well to rise to less exacting results I can see why many throw up their hands and just consign wimpy locos to flatlander or short consist duties - or get rid of them. Arrgh.
The issue of traction tires adds a new factor. The Athearn Mountains have them, but I don’t think they’re on all four driver axles.
Thanks for your initial observations. Heady stuff, once one begins to reflect a little. Mr. Cargo, my junior college physics teacher from the previous century, would have moved you to a seat in the front row of the classroom - where all the smart ones sat.
It seems to me that if only one wheelset were bearing the bulk of the weight, then yes, you’d think it would still be okay, but were the weight balanced, the friction of eight wheels would, I think, translate to more applied tractive effort.
Given relatively equal specifications an 0-8-0 was generally more capable than a comparable 0-6-0.
Thanks, Wayne. And Ed, too. I get the notion that merely establishing a pivot at the mid-point of the driver wheel base is sufficient and that I should not concern myself with the possibility of loading variations from one axle to another.
But I’m inclined to think that any platform upon which the engine is placed for the test must extend equal distances from the mid-point of the drivers’ wheelbase. If not, I would think the platform itself will be unbalanced and throw the whole test out the window.
I’d certainly buy that. Intuitively, eight points where a given coefficient of friction can be applied to the rails is better than six. Presuming that the per axle load weight for four is the same as for three . . .
Yes, the balance platform, by name and nature, is of course balanced when not in use.
If you put a loco, balanced at the mid-point of its driver wheelbase, with that mid-point atop the fulcrum of the balance, it matters not if the loco’s pilot extends further from the pivot point than does the rear of the cab - the balance is for weight only, not length.
Properly balanced, everything forward of the mid-point of the driver wheelbase weighs the same as everything aft of that mid-point.
This one was harder to balance than any of my other steamers…
…and still isn’t all that great for moving much of anything. I had intended to use it as a pusher on the long grade up to the layout’s second level, but I added all-wheel pick-up to both tenders, which creates too much drag. On a positive note, it can run a fair amount of distance into an unpowered siding, though.
Those are known as overfire jets…they used steam to force more air into the firebox. I’m not sure if it was only to improve loco performance or also an attempt to control smoke from the stack.
This is an important point, if you’re using this method. You are balancing BOTH the locomotive and the platform.
During setup, put only the platform on the dowel and balance it. Make a mark on the platform for this point. Since the platform is almost surely of equal cross-section on its length, the middle of the platform will be the balance point of the platform.
When you place the locomotive (no tender, by the way) on it and balance the assembly, the mark on the platform will have to line up with the dowel. You essentially move the loco on the platform to find ITS balance point.
I think Paul is right about the balance point being anywhere within the driver wheelbase, but only as a first approximation. If nothing else, having it too far from the middle might encourage derailment tendencies on the light end.
Wayne mentioned placing a saddle of lead over an engine. An experimentalist might used this technique to determine how important centering the balance point is–just reposition the lead and see if it makes a difference.
First and foremost, Wayne, your modeling is incredible and your very complete (with photos) make it most interesting. Maybe in my next lifetime…
If I may, I find exploring the traction issue a bit more of interest, so read on or ignore as you may be interested in that angle. Purely for interest…
I’ve reinforced my conclusion that the center of gravity being within the (driver axles / wheelbase is a critical issue, but off-center within that wheelbase is not a significant issue from a traction angle.
The key thing is the equation (see link above) where tangential friction force (traction at a wheel rim) equals, and is proportional to, only two things:
I have an Athearn Genesis Mikado, and it seems to balance over the third driver. It has issues–it seems to short out on Atlas turnouts near the frog. I ran it on my friend’s layout, which uses Peco track and turnouts, last night and while it didn’t short out, it seemed to have problems having all the drivers staying on the rails–it looked like the second driver was “off” the rail. I wasn’t derailed, but I couldn’t get all the drivers to sit flat on the railhead.
I have to admit I’m a little afraid of performing the surgery the good Doctor prescribes–I’ll start by adding some lead weight to the front end to see if it helps. But I may have to break down and start cutting.
I’m guessing that rather than a short, what’s happening is that the loco is losing contact with the track. I had a number of Atlas turnouts which worked well with all of my Athearn Mikes (I did mention, but perhaps only in the linked-to thread, that I added Bachmann pick-ups to the tender trucks on my Athearn Mikes), but when a visiting friend brought several brass locomotives to run (Mikes, Mountains, and Northerns), all of those locos stalled on the same turnouts.
It seemed unusual that all of those locomotives would have the same problem, so I looked to the turnouts for the problem.
What I found was that some code 83 #6 Atlas turnouts had frogs that were too high. The brass locomotives, with their usually too-stiff springing, and at low speed, ended up with the non-insulated drivers on the unpowered frog, and none on that side in contact with the live rail before or after the frog.
In contrast, the softer springing in the Athearn locomotive allowed the wheels to move up and down as they should, and at least one wheel would be receiving power as the loco passed over the frog. Even if the Athearn loco was sprung like the brass ones, the fact that the tender collected power from both rails (one truck for each rail) allowed it to continue without hesitation.
After my friend had left, I checked all of the Atlas turnouts by placing a metal straightedge across the rails (power off, of course) and sliding it along the railtops to the frog. Any which revealed the frog to be too high were quickly remedied with judicious use of a mill file. (Based on the placement of the turnouts, it appears that all offending ones were purchased at the same time, and likely from the same production run).
If some drivers aren’t contacting the rail, check that the wheel wipers aren’t mis-bent and someh
If you are dealing with DCC, a short would likely cause a system shutdown, while a contact problem would not cause a total shutdown. I recently had a contact problem with a Mantua 2-8-4. I fixed the problem by adding a keep-alive decoder. They really do wonders to prevent that contact problem, in DCC mode of course.
I read it all and did find it interesting and informative, and not at all boring. I am, however, not scientifically-minded at all, so am not really qualified to dispute your conclusions.
All I know is that my two purchased-new Athearn Mikes were useless pullers and the modifications made changed them into useful locomotives, capable, when doubleheaded, of handling a 100oz. train on my long 2.8% grades.
The improvements lead me to purchase four more of them, all only slightly used, likely due to their poor performance.
Two of those are in-service, while the other two await conversion to change their appearance to match a couple of different prototypes, but they’ll also get the performance upgrades.
A pair of my slightly modified Bachmann Consolidations could handle that same train, but I had mistakenly thought that I had at least changed the plastic air reservoirs for lead-filled brass tubing. I finally got curious enough to check, and was surprised to find the plastic ones still in place, but not for long…
I didn’t bother modifying the stock weight in the same way as on the Athearn locos, but did add weight on the frames, inside the domes, smokebox front, and air reservoirs, and on the cab floor and in the cab ceiling.
Weight now, loco only, is about 16.25oz., with five such locos in service. I have another three awaiting conversion to match specific prototypes, but hope to get them at least to a similar, if not higher, weight.
