# Multiple unit operation



## Treeline (Sep 7, 2009)

I recently acquired 3 battery equipped locomotives. They have batteries and ESC modules (each runs at a different voltage}. None have a receiver installed. Can I install a receiver in 1 loco and run a buss line between the ESC units to run as a multiple unit until I can afford the other receivers ?


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## Treeman (Jan 6, 2008)

Do you intend to run all three on one battery.


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## NTCGRR (Jan 2, 2008)

Can you tell us the make and type?


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## Treeline (Sep 7, 2009)

Thanks for replying . 
The locomotives started as Battery Bachmann Big Haulers and are as follows: (1) 7.2 V NiCd battery, Aristo-Craft SP-6 speed control, stock motor; (2) 8.4 V NiCd battery, Futaba MC 210B speed control, stock motor; (3) 1.5 V NiCd X 8, unknown brand speed control, replacement motor brand unknown. 
I also have 1 Futaba 75 MHz 2DR transmitter and 1 Futaba FP-R102JE receiver I used to test the locos, they all work. 
I would like to couple together and use as helper engines or as plow pushers, not in constant service. You might be laughing about now, but this is a low (no) budget RR at present. Any ideas on how to do this would be welcome, as this is my first RC project. 

Roger


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## East Broad Top (Dec 29, 2007)

Sounds like all three locos use the MOSFET-style speed controllers designed for R/C cars and boats. Technically, you _could_ run the output of one receiver to each separate speed controller, but there are some significant drawbacks. First, each locomotive runs on a different voltage, so your speed range on each one will be different. The MOSFET speed controls are not "smooth" controls like we're used to in trains, but step up rather coarsely from one speed to the next. (Cars, boats, and planes don't need the fine level of speed control we need in model trains.) For instance, if there are 8 steps, your first locomotive will step up just under 1 volt per step, the second will step up around 1 volt, and the third will step up 1.5 volts per step. So, for a given stick position, your locos will be running at three different speeds. That's not good for MUing. 

Second, there's the issue of getting the control signal from one receiver to each of the ESCs. Without knowing much/anything about the specific ESCs, I don't know how they're getting their power to run the ESC itself (not the motor it's controlling). If it's taking it from the battery, then all you'd need to do is run the signal wire from the receiver (the white wire) to the ESC. If it's using the 5 volts from the receiver (the red and black wires), then you'd have to run those as well. I suppose you could plug each ESC into its own separate channel, so you could control all three locos from one transmitter (assuming it's at least a 3-channel transmitter), and each loco would be on its own stick. Personally, that might get a bit confusing, but on the other hand, you could set each stick at a different position to match the speeds. I might suggest that running only two at a time would probably be a better model there than trying to juggle three, but it's at least feasible. 

Your other option would be to get one of the new 2.4 gHz spectrum transmitter/receiver sets and two extra receivers. Extra 2.4 gHz receivers can be quite inexpensive (I've seen people mention them for as little as $15 each!). You can then link all three receivers to the transmitter so they operate in concert. (This assumes the three ESCs all operate the same. Most are single-channel, up for forward, back for reverse.) Then, they can all be run from the same stick on the transmitter. They may run at different speeds, though. Changing the batteries on the locos so they all have the same voltage would also help them run closer to the same speed through the range. The advantage there is that should you decide you want to run one loco independent of the others, all you need to do is tell the receiver to switch to a different channel (no crystals to change--it's all electronic) and you can now run independently of the others. (You may want a second transmitter for that...) 

For a low/no budget solution to your question, either one of those solutions will do what you need with what you got (mostly). The ESCs you've got are not by any means ideal for the purpose, but so long as you're fine with that, then there's nothing to keep you from using it. Long term, you may want to keep your eyes out for people selling off older train-specific R/C systems to get smoother control over the trains. (Along those lines, check Craigslist, etc. for people selling their older 75mHz Futaba R/C transmitters and receivers. Many R/C guys have now migrated to the 2.4gHz stuff and are dumping the old stuff. Check your local R/C shop if you have one nearby. 

Later, 

K


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## Treeline (Sep 7, 2009)

Sorry for the delay in replying, been reading some RC aircraft websites (more info on wiring multiple motors). What I will do is to standardize on 7.2V batteries and hook a bus line between them. Found some old NiCad rechargeable D cells (still work after 12 years) that will fit in the original battery compartments. I will install ESC in each of the tenders, I have 2 tenders with the sound installed I can tap the 7.2 V bus for power and set each up as trailing RC cars. I'll use one Rx in the trailing tender and Y to the ESCs (adding new Rxs , better ESCs and more batteries as they are acquired). Two locos is plenty. Clipping the power leads from the Rx to the lead loco is an idea I didn't see before. This should get me started. Thanks to all that responded! Roger


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