When I work on car kits or restore old already-built BBs and such, I follow the NMRA car weighting rule (1oz+1/2oz per inch of car length) pretty closely, give or take a tiny fraction of an ounce. I have been replacing all plastic wheels with metal ones, so I believe I understand the weight concept, as I see the improvements resulting from my work. Where things go off the ack, is when I am working on a diesel repower and restore situation. The existing weights are weighed separately and together with the loco. If I have a need to modify the arrangement of the weights, because a new motor is used, I try to restore the same overall weight as it initially had. Past that concept, I am not sure if I am doing things properly. Is there a recommended practice,rule or general guide for weighting HO diesels, similar to the car weighting practice? I have not dealt with steam locos yet, but will in the near future, so perhaps any comments on this could also address that situation? Thanks, Cedarwoodron
Weighing Engines? LION wants his engines to be as heavy and possible and still make it up the grades.
We hate engines waiting on the grades.
ROAR
I try to make my locos as heavy as possible. The few diesels I have have been optimized with lead weights. My steamers also get the added treatment. Another thing I do is eliminate the springs on the pilot and trailing trucks. My Spectrum K4 pacific could barely pull 3 HW cars up the clubs long grade. I added just a couple of ounces of lead where I could and now it will start a train of 7 HW cars on the hill and maybe more. Just adding an ounce makes a huge difference.
I do not add weight to my cars except for a load or two on flats and open top cars. Metal wheels and couplers is all I do and they work great also.I feel the NMRA recommendation should be updated.
Pete
LION does add weight to the cars, and yes, the engine (or power cars) must pay a penalty for this, but the weight there disguises poorer track work. In addition to engine weight, Bullfrog Snot helps a lot.
ROAR
If you’re adding weight to diesels, a simple rule of thumb is to not add so much weight that the locomotive cannot slip its wheels. If the loco is capable of pulling a heavy train on level track, but cannot pull the same train up a grade, the wheels should, at some point, begin to slip. If the loco is too heavy, the wheels won’t be able to slip, which means the motor will be unable to turn. This can result in damage to the motor.
The same theories apply to steam, with the added requirement that the weight in the locomotive should be balanced at the mid-point of the driver wheelbase. To test for balance, lead and trailing trucks should be in place. Any springs associated with them will influence the transfer of weight, so some locomotives should have them removed or altered, while others will benefit from their presence.
To test if a locomotive is able to slip its wheels, simply couple a car to it (the tender will serve the same purpose on a steamer) then apply power while restraining the car with your hand. If the wheels slip, the loco is not too heavy. If they don’t slip, you’ll need to remove weight until they do.
These Athearn U-boats were ballasted to about 33.5oz. each, and have a drawbar pull of about 8.5oz.
They’re still able to slip their wheels, though, as each is powered by two Mashima can motors.
There’s probably room to add another 3 or 4oz. of weight behind the pilots without altering their ability to slip the wheels, but I sold them several years ago.
The Athearn Genesis USRA Mikado was a smooth running locomotive, but notorious for its inability to pull even its own shadow around. I liked the locos, though, and decided to perfo
Locomotive weight. More is better. Pulling power is limited by wheel slip. Wheels will slip when the drawbar pull exceeds locomotive weight times the coefficient of friction. Metal on metal (metal wheel on metal rail) is 0.175. That means a locomotive call pull 0.175 times its own weight. So stick in all the weight that will fit. Traction tires have much better coefficients of friction resulting in greater pulling power.
Someone pointed out that too much weight may prevent the wheels from spinning should the locomotive get stuck, either by snagging some scenery or running into a tangle of derailed cars inside a tunnel. This is true, but it’s not a big problem. I have never been able to fit enough lead into an HO model to prevent wheel spin.
I’m not sure where you got those figures, David, but for a diesel, a figure equal to about 25% of it’s weight (at best) is equal to its drawbar pull - that’s for both a model and a real locomotive (not factoring in all of the wheelslip monitoring, etc,., etc. now available on modern prototype locomotives).
I easily fit enough weight into a Tyco C-430 (single truck powered) that it’s motor wouldn’t turn when too many cars were added to its drawbar.
This modified Akane USRA 2-10-2…
…has a very large motor…
…and is able to pull a loaded 100oz. train up a 2.5% grade located on an "S’ bend. The same train can also be handled by a pair of the modified Athearn Mikados which I mentioned. If I were to add one empty hopper (4oz.) to each train, both trains would stall on the hill.
The Mikados would sit there spinning their drivers, even for hours, if I didn’t care about wearing off the plating on the drivers, while the 2-10-2 would sit there totally motionless, the only sign of activity being the smell of burning motor windings and perhaps some non-prototypical smoke.
The difference between the locos is that the Mikes could handle more weight than could be fitted into them, while the Santa Fe, at 32oz., is at its weight limit. If the loco were mine, I would remove an ounce or so of weight, to give it some margin of safety, as I like to run heavy trains. However, I built it for a friend who seldom runs his trains, so there’s little danger of frying the motor.
If a locomotive can’t turn its wheels when power is applied, the motor will be damaged if power continues to be applied.
Adding weight shifts the point at which the wheels begin to slip, but it is pos
I use sheet lead squeezed and glued in wherever it can fit.
I went to Gander Mountain and bought a 20lb bag of small shot, each bebe is about half the size of a standard bebe. I then turn the loco upside down and fill the top of the shell with the shot and level it out to balance the loco. On my digital scale I place both fram and shell for a quick look at the weight then I retry the power and frame to make sure there is room for it, add elmers glue with some water added with alcohol to soak it and let it dry overnite and try the loco out for pulling power. Sometimes its hit or miss but mostly a hit, just my way of adding weight with out all the shaving and cutting for a good fit.Jim. P.S. works great for weighting rolling stock also.
To add the maximum weight, hold with no downward force or butt the engine up against an object and spin the wheels under full voltage. Then add weight until the engine can no longer slip the drivers. Now back off on the weight until you can spin them. Usually, but not always, you run out of room in the interior before this happens. Since the engine is held in this manner, it is equal to the longest train that could be coupled to it, since the engine can only sit and spin.
You can do the same thing with a DMM to monitor amp draw. Using the same holding technique, monitor the max slipping current. Then add weight until you see a sudden rise in current. This rise will usually be in sync with the drivers beginning to stall. Again, back off on weight until this sudden rise is eliminated on the DMM.
But traction tires, while they do improve an engine’s pulling power, also prevents wheel slip in most if not all cases.
Wheel slip is a safety factor for the motor to prevent damage to it, and anything that stops this is bad, IMHO. If a loco is weighted properly, and balanced well, there is no reason it shouldn’t be able to pull enough cars to satisfy almost any modeler. I have steamers that have been balanced so well and weighted properly that have no problem pulling 100 cars up a 2% grade, without relying on those tires.
It usually takes only a relatively few seconds of stalling most motors available today to damage them beyond repair.
Wayne,
I have one of those Akanes as well. On the club layout, I can pull from 85 to 100 hoppers with it, depending on the make, type, and owners of the hoppers, (metal wheels, weight of individual cars etc).
Traction tires, if the wheel is not grooved to accept them will be more prone to derailment. Thus Bullfrog Snot is the better choice, as it can be applied really thin and still improve the traction. On my subway cars I put Snot on all of the traction wheel of the power car, and for most modelers this would be a no no because then you would have no power pickup left. The LION, having replaced all of the couplers with drawbars also added wires between all of the cars. Now he has 48 wheel power pickup and never any electrical problems in his operations.
Of course you still need to weight the power car, and you cannot add so much weight as it stops pulling its train up the hill. If the wheels slip: add more weight, if the wheels stall remove some weight.
If you hit a happy medium, she should not have been walking on the tracks in the first place.
ROAR