When adding weights to a car (NMRA RP-20.1) is it better to add the weights directly over the trucks or to spread them out over the length of the car?
Thanks,
GN Goat
I would imagine that it would be better to see the weights added to the whole car to make the combined total weight higher than just over the trucks. My rationale is that if it was better to have them over the trucks more modeling companies would do it that way instead of a whole body weight. It also might help with ease of turnouts, etc.
I always put weight in the middle of the car when possible. You could add the same amount over each truck as well.
For weight I use used mag wheel weights from the local tire shop. Soak the weights in lacquer thinner for about ten minutes to remove the tape from the back. Attach the weights with contact cement or Walthers Goo. I add weight equally over each truck. Weigh the car before adding weight to see how much is needed.
The tire weights are in either 1/4 ounce or 1/2 ounce increments. Just break off what is needed and stick them down. Place your weight as low in the car as possible as this gets the centre of gravity lower and avoids a car being top heavy.
As usual you get varying opinions. I always have put the weights over each truck. I really dont see how it matters just centre them from side to side or the car will a a list. Are you using the 1/4 oz. stick on weights?
Dave
Keep the center of gravity as low as you can. Otherwise, it does not matter if its over the trucks or in the center of the car. I am not aware if NMRA specifies either over trucks or in car center.
The only two reasons I can see for keeping weight off the center of the car frame would be:
- The frame will distort under it. Since the weights we are discussing are a few ounces at most, I see this as a non-issue.
- The unprototypical weight would be visible through an open car door - which would only be an issue if the car doors can be opened.
IMHO, the biggest reason manufacturers use a single flat plate weight is for manufacturing convenience.
At one time, in order to hide the weight needed to bring a truss-rod flat car up to standard, I wrapped wire solder around the axles - after painting the backs of the wheels with insulating shellac. Can’t get the center of gravity much lower than that! (No car tilt from off-centerline weight, either.)
Chuck (modeling Central Japan in September, 1964)
The key is to keep the weight balanced from front to back and side to side. If I am just adding one weight, it goes in the center. If I need two, they go over the trucks. The trucks are supporting the same amount of weight no matter where the weights are place. As long as they are equally sharing the weight, you should have no problems.
I spread the weight evenly between the trucks when possible, otherwise I put it in the middle. One thing that can be used for weight and is cheap is Rose Art modeling clay. It’s easy to work with and can be pushed into bottom of a car, handy for adding weight to a flatcar. It can also be painted.
As has already been pointed out, keeping the weight low is important to keep the center of gravity low, and the items you’re using for adding weight will determine which will work best, long, thin, flat weight, or lump weight.
The other thing to consider is whether you’ll be adding interior detail, such as in a passenger car, in which case you’ll want to have a thin weight which can go between the car floor and the detail floor. Lump weights, like wheel balancing weights, would just be in the way for interior installation.
Chuck, That’s a great idea for adding additional weight. Many times a flat or bulkhead will be underweight and there’s really no place to add it. That would sure do the trick.
Hot glue may work to keep the solder insulated from the wheel back also.
I added some to some MDC hoppers that were too light.
I used some tire weights, and put them over the trucks. I used the tape that they came on though.
Chuck, I trust you used solder that didn’t contain rosin, or at least didn’t contain corrosive rosin.
Mark
Some time ago I discussed this with a physics prof from the local college. There is a lot of somewhat complicated physics involved, but the over-simplified answer is to put the weight over the trucks. This puts the weight where the greatest amount of force is required to “lift” the truck resulting in a derailment. Think of it this way. If the weight is spread thru the car, there is a lever effect resulting in less force to lift the truck on one end since you are only lifting part of the weight. As I said, it is actually pretty complicated. I would point out Branchline cars use a large nut over the truck at each end for weight.
Jeffrey, that may be a good idea for me too. I am doing coal operations and the “life-like” hoppers I have are not heavy enough to go through switches without jumping the switch. I have 1/2 ounce weights that I put in them and that takes care of the problem but then I have these ugly bulky lead weights in them, and I can’t cover them all with coal loads, have to have some empties ya know. No other place I can see to add these weights. I may be able to use the clay then sprinkle one some coal ballast to look like left over coal in the hoppers. What do you think?
Any reason you take the double sided tape off? I have many cars installed using the tape and never had one come loose yet.
Sounds like a good idea to me. Do whatever works best for you.
You can also try adding weight under the end slope sheets, or between the hoppers. Try a split shot type fishing sinker (the smaller, the easier to work with) or BB like for a BB gun.