Again, thank you for your advice on special cleaning techniques - from balsa blocks to alligator clips to Post-its. I'd like to ask another performance question: Is there anything simple that can be done to get 2 locos (same model; DC, not DCC) to run closer together in speed? Couple years ago, I bought 2 Bachmann Spectrum 2-8-0s to run in tandem over my mountain division. Wonderful smooth-running little locos, but one draws much more current than the other - runs much slower when the 2 occupy the same powered block. If there's a problem, it's not obvious - they both run smoothly and quietly - just at different speeds. I'm not eager to tear apart the slow one to enlarge the valve gear holes, but I'd really like to use them in tandem. Any recommendation on what to do? Scott
Well Scott, I have been asking the very same question in (hide my shame) another site! Most replies answer with: Resistors, Zener Diodes, or small Linear Taper Pots. I have experimented with resistors, but have yet to get enough of them to pick the right one. I have a brass steamer which needs a little help pulling a heavy passenger train, so I added a Tomytec chassis to a Microtrains RPO, but separately it tears off down the track long before the steamer even thinks of moving! Attached, it just spins it's flywheels. Now the shops are open again, I will be getting a few bits to try. In the meantime, any advice would be most welcome! Cheers, Bob.
I'll give you two tips that have been very helpful for me. First, the type of DC is a factor. Plain 'ol straight DC remember is not controlling voltage, it is actually controlling current by introducing a resistor in series into the circuit by use of a rheostat. Voltage drops as a function of increasing resistance. If you look at any of the 'transistor' type throttles, they vary from a pure pulse-power situation where half-wave AC is put in the circuit (very buzzy) to 'stepped' square-wave pulses of varying voltage. I have two transistor throttles of long vintage - one an original "Cama" train controller and the second a "PSI 550 Cabtroller". Both are designed to take in a fixed DC voltage and modify it for train control but it is still "DC". These work sort of like pulse power. On full tilt, they act like it.... rather noisy and buzzy. But what I discovered was that if you decrease the input voltage they still work, and run cooler and quieter. What's this have to do with motors? Well, on any kind of square or half-wave DC, an interesting phenomenon happens that the motors are 'stepped' in unison. You can actually see it if you put a string of diesels in a row with the body shells off. They will typically start, and run, in identical RPM. You're popping them with powerful short bursts of DC which tends to run them the same speed, and there's enough power there to keep them moving. The impact on train operations is impressive. It about doubles the adhesion of multiple unit strings - the tendency for one unit to start spinning is minimized. As long as the motors and gear ratios are at least similar, it will work. So I run three Kato SD45's, and two C30's and a GP35 (Kato), and two SD45's and an Atlas SD50, and four remotored RSD15's, and four Kato F-units..... you get the picture. If the mechanisms and motors are similar, it works well. Put them on straight DC and I get the same problems, the one with the least resistance always runs faster. You'll still run into situations where one unit is significantly faster. I have that with the Atlas SD50 vs. the Kato SD45's. A trick I learned was to put two diodes in opposite direction beside each other making a 'bridge' in series with one side of the motor. Each diode pair tends to drop voltage about 1.3 v or so. What that does is decrease the voltage to the motor without changing the resistance, so it slows the unit down by 1.3v. per pair of diodes. You can pile as many in there as you can fit - it took four of them to make the SD50 slow down to work with the SD45's. So you can tweak it this way, but you can't do miracles. I will tell you that resistors will not help, you're modifying the current, not the voltage, so all you'll do is modify the rpm's under load, and as soon as that load increases enough the resistors will get plastic-melting hot. On my transistor throttles, I control the input voltage to balance out the need for power vs. the racket the motors make - I'll turn it all the way up for a four-unit set of Kato F's and have it maybe half the input power for a single SW-8 working the yard. Multiple units tend to need the higher voltage spikes to keep them running in unison. Since DCC started these techniques seem to have been lost, as you can program speed tables into units individually. But this is one of the reasons I stay with DC, I can get things to run the way I want and have for years. That PSI 550 was a real nice hand-held throttle, one of the best, and has complete momentum and braking and a 'brake handle' that you can do a set and release on, great fun to use. I use the old Cama for yard switching and the 550 for road trains. I just love to hand over the 550 to an 'expert' modeler and watch him shut off the throttle and the train coasts until he applies brakes... you can even 'power brake' with it.
Since not everybody is an expert electrician the easiest thing you can do is get two new motors. This worked for me, if you can change motors the new motors Atlas and B-mann are manufacturing now are a lot slower and much quieter so they match a lot better in speed I have changed a few motor in my Atlas locos and a few in B-mann's also now most all my Atlas run the same speed and same with some of my B-mann I can also run some Atlas with Kato since the motors are almost the same, in fact I have changed one of the motor from my Kato SD40's because it was a fast Kato motor to an Atlas motor and it matches better with my other Kato SD40's then before because it has the same speed. The nice thing about the motor swap is that you can sell your old motor so you get some money back also. I hope this helps you a little better.
BTW, the tomytec motors are some of the fastest out there. My 'powered boxcar' conversion is designed to use either the original motor in my new frame or an Atlas slow-speed motor like in their current diesels. There's an enormous difference in the rpm's between an old Atlas and a new Atlas that no electronic tweaking of mine can overcome, so...yeah.
Issue: Locomotives run at different speeds. For the most part this is based mostly on the use of Atlas four axle locos. Visually I like running two Canadian Pacific locos, (elephant style), up front with a string of matching bright red coal hoppers / porters / bath gons etc. Proffered Idea: There are a few possible uses for the faster 4 and 6 axle type models. Caution - derailment danger: Do Not try this where there is an open drop to the floor Do Not try this where there is a hard to reach spot on the layout Is very time consuming - uses trial and error approach Requires significant observational skill How to: The following is based on a huge amount of "trial and error" along with dumb luck. Like many I noticed that one of my Atlas GP30/35 units was running a lot faster. If it was 2nd it would start to move before the lead unit. Hmmm, ok, now what? So, I put the two on the same loop of track and watched. Ok, "Spedie" was moving way too fast. I put "Spedie" behind the 6th car of a 12 car the consist unit train. As expected she moved out first compressing the string ever so much. A few seconds later he, (the brute), lead unit moved out and off the train went. Around they went a few times much to my joy - flawlessly. Oh, wait, is that the phone? Off I rushed to answer it. When I got back the - just a few minutes later -: The lead unit had stalled Speedy had kept going 3 cars had been pushed off the track 2 more were dangling Fortunately this was not where they could fall to the floor. I figured if I added cars behind "Spedie" then in the event of a stall speedy would stall as well. Trial and error ensued. Other uses: "Spedies" can be used for light weight / short commuter rail / passenger service where higher speed is acceptable "Brutes" can be used for yards and locals or with other brutes as lead units. Conclusion: Atlas GPs in general make great mid train helpers - if - you are careful and never leave the room. When your back is turned the lead unit will stall and the "Spedies" of the world will shove the intervening cars off the track. You can reduce the derailment by increasing the number of cars behind the mid-train helper. It will take a bit, (maybe a lot of), time until you can easily make up such a consist. Note: I have no idea how this would apply to steam type locos.
IT WORKS!!! Many thanks rangust. I experimented, as you suggested, with diodes and found 3 "facing" each way (6 in total) onto one motor terminal, and the Tomytec now runs exactly the same speed as the Pecos River Brass 4-6-4. Thank you,thank you,thank you. Cheers, Bob.
I cover this whole concept in-depth on my 'powered boxcar' instructions that use my own frame with the Tomytec parts to power an REA-type express car. I first started tinkering around with the diodes back in the 70's because I was using straight DC and had a fleet of Minitrix U-boats that would just not work together right. One of my electronics buddies gave me the idea and some tiny diodes and that's what worked. And, considering the price of diodes, this is dirt cheap and easy.
Um, I don't think he needs "easy". He pulled off the fix in less time than it took for me to post my "MU" options, (less than 45 minutes). Very impressive.
Rangust - thanks for your very informative input. If anyone has time I'd love to know why diodes work. I thought they controlled direction of travel for electricity? Do they also have an influence on hertz and such? Wish my father, (EE / AD / Power Conversion), was still around. There are soooo many things I want to do with electronics to automate the "Grey and Grandure". Um, then again, if he was, he would have probably directed me into some form of DCC so far over my head, well, anyway, a nice dream. Thanks again Rangust.
Wow, if you need that amount of money for a DCC system & chips, then you must have a very substantial investment in MR equipment. Why not take out a loan and make the switch? You'll be glad you did!
Trouble is, I'm semi-retired now and don't ever want to be in debt again. Mortgage paid off, and just working the odd day for fuel for the cars! And, I'm too lazy to start fitting chips in 140 locos and adding reverse loop voodoo magic boxes LOL.
If you have two identical engines and one is drawing more current and running slower there is most likely something binding mechanically. You may be able to compensate by reducing the voltage to the faster engine as mentioned in several of the posts, but you aren't fixing the problem you're hiding it temporarily. Sooner or later you need to fix the mechanical problem.
The diodes work because when they are conducting there is about a .6 to .7 volt drop across each one. Having three in series would yield a voltage drop around two volts. The reason you need a set going in both directions is so you can get the same voltage drop in forward and reverse.
Just a thought ( I dought if it ever has been tried) but try putting a 1 ohm to ten ohm resistor in series with the power pickup lead or a light bulb of different current ratings in the faster engine it just might work.
