It would be not make sense for the NMRA to give a minumum or standards for weight in a locomotive since a 4-4-0 tea pot may not be large enough to add a sufficient amount of weight to meet any univeral standard. Traction tires are used in the case of plastic modles needing more weight.
The interesting result of adding weight to a model is the adhesion factor of metal to most metals is normally around 25%. If your model weights about 16ozs and all of the weight is on the driving wheels, the drawbar pull should be about 4ozs. You need to add about four times of weight compared to the added amount of tractive effort achieved.
New models tend to be better pullers after some of the polish is off of the wheels. Real prototypes normally fall in the same adhesion percentages except for the newer AC diesels using over slip electronics achieve a much higher adhesion factor. Six axles usually pull better than four for the same overall weight. I am sure there are exceptions to this, but it is a general physical characteristic of the metal to metal interaction.
Traction tires alter this factor since they do not use metal against metal and offer much higher adhesion levels. The model should always be able to spin its wheels at the stalling point to prevent the motor from damage.
Leon,
I have six of the metal bodied shark A Units, and two B units. Three of the A's have the original drive and three have the Hobbytown drive. I got all these off Ebay, some came with the drive, some were just the body. The original drives run good but don't pull as well as the Hobbytowns, which have all wheels driven. The power truck from the later F Units (identified by the metal plate on the bottom) were some of the better ones for the money at that time. This was when Athearn had the rubber band drive locos, so the gear driven motor unit (called the MU-2 power truck by Mantua/Tyco) was a real advance, and only a bit more expensive than the Athearns of that time.
I still have most of them, and they all run well.
Leon Silverman wrote: The rated stall current for a particular motor may not be available to you. In addition, this may not be a safe load limit for that motor anyway. Knowing it's value is important if you decide to install a decoder.
The rated stall current for a particular motor may not be available to you. In addition, this may not be a safe load limit for that motor anyway. Knowing it's value is important if you decide to install a decoder.
Yes it is.
If the decoder has a lower rating than the motor's stall current, it will shut down without burning out your motor. If the decoder's capacity exceeds the stall current of the motor, it can concievably burn out your motor by overloading it.
No don't do that. The decoder has to be able to accept the stall current in order not to burn the decoder up. If not you are pushing too much current through very delicate electronics, guess what, it fries itself. Then you have to put in a new one. A rule of thumb for HO is Athearn BB is 1.5 amp and 1 amp in other quality locos like P2K, Genesis, Kato and Atlas. These motors will handle the excess power far better than the decoder.
Locomotives never have enough weight.
As long they spin wheels when stalled they should do fine.
I usually add more locomotives to the consist until the train moves; it seems to be easier to have several motors sharing the load than one motor overburdened with weight.
Larry
Conductor.
Summerset Ry.
"Stay Alert, Don't get hurt Safety First!"
The rated stall current for a particular motor may not be available to you. In addition, this may not be a safe load limit for that motor anyway. Knowing it's value is important if you decide to install a decoder. If the decoder has a lower rating than the motor's stall current, it will shut down without burning out your motor. If the decoder's capacity exceeds the stall current of the motor, it can concievably burn out your motor by overloading it.
The safest way to determine the weight limit of an engine is to run it at full load (speed and train length for at least 1/2 and hour and feel the shell around the motor. If it is cool to the touch, you can add weight. Retest the engine at the higher weight and longer train length again for half an hour. If it is still cool, you are OK. This might be an issue with the older style opened frame motors. Modern can-type motors should not be sensitive to added weight.
Tom Dielh:
I also had a Tyco Shark. It had a single powered truck with traction tires and the motor actually inside the power truck and gearing directly to the wheeels. This engine ran hot and eventually burned itself out. A hobby shop proprietor told me that there was too much weight for that single motor to handle. Considering the fact that this armature was buried inside the truck with no air circulating around it for cooling, I am not surprised. I noticed later that Tyco offered an F-unit with the same type of drive, but it was dual motored.
METRO wrote:There have been a couple of heavyweight preformers in modern model railroading as well. The P1K DL109 comes to mind, that thing can pull better than my Genesis F7s. The only problem I've found with weighting the top of bodyshells on Athearn BBs is that it reduces their top speed around curves. I've got a few of the older BB C44-9Ws that came in kit form and the weight made them unstable on curves, so I had to put it lower on the frame. Cheers! ~METRO
OOOOKAY..Never notice that problem at scale speeds..What type of weight did you add to the frame? That sounds interesting..I might be able to add some more weight..
As Virginian said above, there is no standard for weight of locomotives, or cars for that matter. RP20.1 is a Recommended Practice and the NMRA goes to great lengths to differentiate between the two.
Not quite sure what you mean by "pull the train with a strain." Is the loco slipping?
Back in the old days (yes, I'm old enough to say that), locomotive models were made as heavy as possible for the best pulling power. Die cast metal bodies and boilers were the norm rather than the exception back then. I have several Tyco models of the Baldwin Shark with a die cast body shell. The body weighs slightly over a pound by itself. Couple a string of model cars behind this with the slippery plastic trucks made nowadays and these things can pull a heck of a train.
"Clipping" only happens with an AC voltage/signal, the top and bottom of the sine wave is "clipped off" best seen with an oscilloscope. The closest thing that would happen to a DC voltage is to overload the power source (too many Amps being drawn). The best ways to add weight to a locomotive safely (to prevent motor burnout) would be 1. insure that the locomotive drivers will still slip if you try to pull too many cars, 2. have an ampmeter connected with the power pack and insure you're not exceeding the rating of the motor (for old BB Athearns, I believe it was half Amp or 500 milliamps).
While there is no standard, remember that it's possible to add too much weight.
I have a all-cast metal DL109 (Athearn drive) that will not spin the wheels under any circumstances. That's too much weight.
Your loco should have enough power to break traction. Otherwise, you can easily overload the motor (by stalling it) and melt it.
Paul A. Cutler III*************Weather Or No Go New Haven*************
Have been playing with the old Athearn Blue Boxes some more and pulled out a E-bay win that had not been up to snuff. Ran well but pulling power was not great. It has the old style round motor and steel flywheels, it is a SPD-40 C&O.
I hooked it up to a 39 car train that has to go up a 2% grade. An BB FP-45 will pull the same train but it is a strain. With the C&O I had to help it up the grade. It did feel lite but was running well so I added some weight.
Added around 3 oz and would pull the train but was still a strain but will do it. My scale only goes up to 16 OZ's then 500 grams, must be a metric thing. With the weights I bureded the 500 grams and guessing around 19OZ's.
Just wanted a idea too what one should weight. F-7A Super weight comes in right at 16OZ's.
Went double headed SPD's and pulling well.
Now thottle question? Is to much thottle bad? Thanks to Darrell I am running a MRC 2500 with 16VA out put. Doubled headed I have to crank it to 90% to get any kind of speed. Have a MRC 260 coming at 20 VA so I have a little more power.
Now back to my stereo back ground. On a lower power amp when you drive it to hard something called CLIP happens. Amps does not have the back up power to power a transtiant peak, power wave falls off, goes flat and blowes a speaker. In stereo world back up power is called Head Room. Amps is putting out say 150 Watts RMS but there is a passage that needs say 175 watts too sound right. Power caps store power so when it happens you have 175 watts +.
Just wondering if anything like this happens with DC thottles, and if so will it fry a train motor?
Well it is 4:00 AM and time to crash. But if the darn board was not running so well I would have hit the hay 3 hours ago. Round 150 hours with no problems, added 2 more rolling stock that has been worked.
This is getting to be fun again, Cuda Ken
I hate Rust