I need to slow down trains in a 3 rail lionel conventional control public / club layout. We are running multiple trains using stop and trigger tracks. There are some down grade areas where the trains just run too fast. We want this when on view to the public be a hands off layout. I need to isolate some blocks and through rheostats, or a resistor bridge taps decrease the voltage to these blocks, while maintaining it on the others. Using Lionel 135 or 180 watt powerhouse bricks what value and wattage resistors / rheostats should I use, and where best to buy? Thanks, Dave
wow 30 x 50 thats huge. Got any pics? Sorry i dont know anything about Rheostats, just say the huge layout and was wondering if you got pics. Dont worry there are some smart guys and gals here who will answer this. …thanks
I used a variable resistor from a trailer brake for a car.I don’t know the price because I had one laying around but it should be available from any auto store.I have had it hooked up for about three years and have had great results.I just wired it into the block that controls the down grade.I use the same power system you decscribe so I know it will work.
Ed
I’m not familiar with trailer brakes; but that may be a good source of rheostats. Old Lionel rheostats, like the 81, 88, and 95, which have a maximum resistance of 5 ohms, are easy to find at trains shows and on Ebay and usually cheap.
Rheostats are certainly a simple way to do the job. Bridge rectifiers have the advantage that the voltage reduction does not depend on the load current. This could be useful if trains with different current requirements are run on the same grade. To modify a rectifier module, short the + and - terminals together and put the ~ terminals in series between the transformer and the center rail. Use as many modules, rated around 5 amperes, as you need to get the speed you want. You can use the ± point of one module as a half-module tap for fine adjustment. The drop will be a little more than 1 volt per module; but you can’t measure it accurately with any usual voltmeter. Trial and error is best anyway.
Bob gave me the bridge rectifier instructions several years ago to reduce voltage for a smoke unit I put in a dummy. I have used them since for more smoke units and reduce voltage to accessories “in line” with other that operate on a higher voltage. Works great.
And that’s how I did all of my voltage reduction, thanks to Bob. I went the easy way out and used the rectifier modules from Radio Shack, but it was very easy because they are big and have a mounting screw hole. I had to go to 5 different RS to get enough. Each one has a couple in stock.
Wes
Those big ones with the holes (276-1185) are rated for 25 amperes. But the hole can be handy for mounting, as Wes says, and might be worth the extra buck.
The 6-ampere ones (276-1181) are plenty big electrically. Even the 4-ampere ones might be big enough; but I wouldn’t go lower. The 400-volt rating (276-1173) is no better for us than 50 volts (276-1146), and it’s 50 cents cheaper.
Mine is the 276.1181. There is a hole in the center…
http://www.radioshack.com/product/index.jsp?productId=2062583
I have been using diodes to control speed on both uphill and downhill grades on my Lionel postwar layout that uses a standard set of Lionel trestles. This is quite a steep grade. Here’s how I do it. For blocks that are level I use 2 sets of opposite facing 6 amp diodes. This reduces the voltage to the level blocks by about 1.4 volts. The uphill grade gets full power. On the downhill grades I use a series of opposite facing diodes running through a 6 position rotary switch (Radio Shack). I have two separate blocks on the downhill grade, so I can select the following:
Position 1. 1 diodes beginning grade 0 diode ending grade
Position 2. 1 diodes beginning grade 1 diode ending grade
Position 3. 2 diodes beginning grade 0 diode ending grade
Position 4. 2 diodes beginning grade 1 diode ending grade
Position 5. 3 diodes beginning grade 0 diode ending grade
Position 6. 3 diodes beginning grade 1 diode ending grade
The ending grade adds 0 or 1 diode to the beginning grade.
The downhill grade diodes run through the level block diodes. I know that this sounds complicated, but it gives you lots of control over the downhill grade.
Factors that affect the speed on the downhill grade, engine type(magnatraction, traction tires, weight of engine, type of motor), number and weight of cars.
You can see that I have only one selection for going uphill but many selections for going downhill. For some reason the downhill grade is much more variable that the uphill grade.
I also run all track power on my LW transformer through 2 sets of opposite facing diodes to cut the power even more so that the low end speed is easier to control and the top end power is reduced a little.
To add to the above post, I use the same RS 6 position switch and it works great. Pos 6 is full throttle, pos 1 is just enough voltage to stop the train without shutting down the speed control. I just grabbed 4 more voltages from the strip to fill the other 4 positions.
Wes
Major problem with using resistors is heat and different voltage with every different train or load.
Isolate the track section you want to run at a different speed.
Place a small transformer set for the speed you want for that section.
I think you have to worry about transformer phase with ajoining track pieces being run off of two different transformers. That’s what I remember reading here.
You can do it all with one transformer if you use the rectifier diodes.
So many different ways to do it.
Wes
Wes, unless you have the phase and the frequency and the waveform and the voltage the same, there will be a fault current and arcing. But if all those are the same, there will be no change in the speed either. That is a good reason for using a voltage-dropping element like a rheostat or a diode string.
Spike, doing it that way guarantees a fault current. It is true that the voltage drop with a rheostat varies with the current drawn by the train. But the voltage drop using the bridge rectifiers does not.
I made a comment earlier about doubling the current rating of the bridge rectifiers, which was wrong. I have edited it out.
Since I don’t know much about syncing all of that up, I’ll stick with my strip of rectifiers!
I just dug out one of the Radio Shack 6-ampere bridges; and, sure enough, there is a hole, just like Wes says.
If you have trouble finding these at RS, a lot of them are dropping components, All Electronics has 6A with a mounting hole for .80 each in lots of 10.
http://www.allelectronics.com/cgi-bin/item/FWB-66/search/6A_600V_BRIDGE_RECTIFIER_.html
Keep in mind that this is a surplus house and what they have in stock varies from time to time.
Do I understand this correctly???
Can I connect (1) series of bridge rectifiers and tap off varoius locations to provide voltage reduction to various blocks? It looks like there is one series of bridge rectifiers, with multiple take offs.
Say I have 3-blocks of track and I want to reduce speed 3-times. Can I build one series of rectifiers, and tap off three times from that same block?
Thanks,
Kurt
If you look at my strip, the highest voltage in on the left (where the output of the transformer is clipped on), and the smallest voltage is on the right-most prong. Each prong offers less voltage as you move from left to right. I think you will find that each prong drops around 1/4V or so. That’s small enough steps for me.
You can tap as many times off of one prong as you need to. If you have trains with a speed control, all you probably have to do is step them down to the final voltage since it will slow down (with brakes if you have sound). If you are running older post war trains and you have the slow down room, I would probably string a bunch of single track blocks together and drop a half volt or so each. It might be smoother than just dropping your total 3 volts all at once. I haven’t tried it as all of my trains are newer MTH models.
Wes
Yes, Kurt. You can use multiple taps on a single string of modules for different blocks; and you can tap the same point for multiple blocks. You can even get a half step by tapping the ± connection of a module. Each complete module will drop the RMS voltage by a little more than a volt. The steps are not all the same, but close enough. You can’t measure the voltage accurately with a normal voltmeter, neither on the track nor across the rectifiers, because the rectifiers do not produce the sinusoidal waveform that most meters expect.
Maybe this is my problem. I hooked up three bridge rectifiers (RS 25A 50 V) as described. I tied the + and - together and then ran the Ac in series through the ~ leads. When measuring with a DVM on AC scale I was only getting a .7 volt drop instead of the expected 1.2 - 1.7 drop the package said I would get. Did I do something wrong, or can this only be measured with a scope ? Dave
BTW I wired and attached them to a board. On the same board a used a Euro Terminal block. This gave me a place for AC in, then 3 taps, one after each bridge rectifier.