Tungsten Weights for Tomytec and Other Power Chassis

[brill27mcb]

I have a lot of smaller plastic Tomytec power chassis for powering both Tomytec trolley/tram models and other models like 3D-printed and resin-cast shells. Chassis like the Tomytec TM-TR01 and TM-TR04 come with chassis end extensions (4 various lengths to suit the particular model) and 2 cast weights designed to fit into these extensions and add necessary weight. I used to simply place the weights in, thinking that when the extensions were press-fit onto the main chassis the weights would stay in place. This turned out to be wrong. The 2 weights are different (thick and thin versions), and the longer extensions let them slide toward the end of the model so they could get loose. I've actually lost a few weights this way.

 

So I recently went through my Tomytec fleet and glued the weights down with craft store "tacky glue." Sometimes, the pedestrian safety bars at the ends of the models (called Lifeguards in the U.S., an actual trolley hardware manufacturer's product name) that go into slots on the front of the chassis extensions pop off easily, too. They are very easy to lose, so whenever I found one that was a loose fit I tack-glued that into position, too, gluing at the top where any mess would be out of sight.

 

After searching, I found a ready U.S.-based source of small weights that I could use to replace (or add to) the Tomytec weights. There is not much free room on these chassis to add weight. These weights are made from tungsten, which is denser weight-wise than lead, steel or brass. They are also rectangular, so they can be grouped together closely and even stacked for more weight. The ones I found are sold as high-tech parts for Pinewood Derby gravity-powered race cars by someone on Ebay with the ID of "TxChemist Tungsten" in Texas. It's hard to find weights smaller than 1/4 inch cubes. These are the smallest weights I could find, and they are offered in convenient quantities at prices I think are reasonable. The ones I found are 3mm cubes (the seller calls them 1/8 inch but they are smaller), and 4x4x1mm "chips" or flat tiles. This seller provides 60 3mm cubes grouped between 2 layers of clear tape, so they are organized (and can stay organized); the 60 or so tiles are simply loose. Here are some links with photos for reference (I have no affiliation with this seller, and these links will probably go dead after some time):

 

Cubes: https://www.ebay.com/itm/134053730273

Tiles: https://www.ebay.com/itm/132959165446

Assortment of both: https://www.ebay.com/itm/134105058336

 

I bought the assortment. These work perfectly on the TM-TR01 and TM-TR04 Tomytec chassis. Two of the 3mm cubes just fit side-by-side between the extension's round mounting lugs, and then 2 of the 4x4x1mm tiles fit vertically against these and ahead of the lugs. Here's a photo:

 

 

The left side shows the four chassis extension sizes, and on the right (from top) are the mounted Tomytec thick weight, the thin weight, and the substitute tungsten cubes and tiles. Once the tungsten weights get clear of the main chassis overhang, more could be stacked vertically for additional weight. These little weights will also be useful to tuck into available spaces on other small powered chassis to improve wheel/rail adhesion and electrical contact.

 

Rich K.

 

[cteno4]

Nice Rich! Add some tungsten powder in the rest of the space to max it out.

 

jeff

[brill27mcb]

I saw that there is a tungsten putty, too, which supposedly never hardens. I wonder if it can be removed cleanly or leaves a sticky residue. I prefer processes and materials that can be undone, when possible. What holds the powder together and in place?

 

A note on adding weight: You can add too much. Decades ago I used to read the National Model Railroad Association (NMRA) "Bulletin" every month, and there was a regular column where the author would put different manufactured model railroad locomotives through a standard series of lab tests. This included weight, motor voltage/speed/current-draw charts, pulling power, maximum incline angle the loco could climb, and so on. They would rank the model's performance and efficiency. There was also a small sector of the hobby that focused on model loco performance, maximizing traction, balance, pulling power, slowest-possible speed, and so on. They would hold contests. One lesson I remember from reading all of this was that modelers who gave thought to all of this would find out or determine the "maximum continuous amperage" that a particular motor could draw safely without overheating. They would add weight to the model loco until that current level was reached when pulling a load. Then they would stop adding weight. The engineering logic was that when a loco reached that "red line" on current drawn, they wanted its wheels to start slipping. This slipping would act as a "safety valve" to prevent damage to the motor.

 

The Tomytec motors are hardly the best ones to use to maximize pulling power or weight. Their actual useful operating speed occurs at a voltage well below the nominal standard 12 volts. At a lower voltage, to get the same power (watts, which in DC is volts x amps) the current they have to draw has to increase, raising the heat of the motor and prospect for overload and damage. The Tomytec motors are inexpensive, low-grade motors by today's standards, and I'm amazed when people want to use a Tomytec chassis to power locomotive models and pull a long string of cars. It's the wrong choice. (For a trolley or tram pulling a trailer or two, it's fine.) Some skilled N-scale loco builders use a Tomytec chassis as a basis to power small "critter" locos, but the first thing they do is replace the motor with a higher-quality 12-volt motor, often one with a gearhead attachment to lower the loco's speed even more and give the motor a greater mechanical advantage. Only then do they think about how much weight they can safely add.

 

Rich K.

[cteno4]

Rich,

 

tungsten putty is at about solid lead density, so you loose some. I’ve never used it but never heard any comments about residue but I expect none were into removing it.

 

tor tungsten you can use PVA glue that should easily pop out of the plastic cavities with a little prying or soak it out. Can’t use PVA on lead as slow acetate reaction that swells the mass and eventually breaking down. This has been a long standing debate, but it was settled for me a decade ago when I was reading about it and dug up a few old cars from my childhood where I had added lead shot with PVA glue and yes it had swelled and some actually broken apart. 
 

there was an old method using plaster powder to make a paste, seems messy. 

 

I can see some more weight in some of the Tomytec mechs mire for smoother running as they can jump around on points and some track joints and stutter a bit. Also btrain shorties may use some more weight as well.

 

jeff