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Are Two 9V Motors Better Than One?


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#1 TheBrickster

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Posted 22 August 2009 - 04:06 PM

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For those of you who collect 9V trains, I'd like to address a topic related to motors.

Does the use of two 9V motors really add power or speed to your engines?  While I believe the answer is yes; because not all 9V motors operate at the same speed, how does this affect the slower motor?
Is it bad to have one motor helping pull another?  
How does additional tension/strain on the slower motor affect its long term use?  
Are two motors really better than one?

Discuss the use of two 9V motors here.

#2 muffinman42

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Posted 22 August 2009 - 05:05 PM

with two moters your spliting the weight between two of them so they effectively pull only half the train each.
with PF moters (both linked to the same battery box) it works that more moters=better.
if you put a moter in each truck then your speed should stay the same(if you dont change the speed setting) since each one added is pulling its own weight.
the more moters you have the less each moter is pulling.

#3 Rijkjavik

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Posted 22 August 2009 - 05:06 PM

Never tested a train with two motors, but I think two are more powerful. If I look at big 8-wide 9V powered engines that have to haul a long train, almost everytime the engine has two 9V motors.

It's multifunctionomical.

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#4 Captain Zuloo

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Posted 22 August 2009 - 11:50 PM

As we have seen other uses fo 9v motors being pulled (by PF over a piece of 9v track to trigger an event) I would assume that pulling the motor wouldn't be a bad thing. In fact, as 2 motors are used to pull the train rather than 1, I would say that using 2 motors would certainly even prolong the life span of each motor.

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#5 Diamondback

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Posted 23 August 2009 - 06:01 AM

Advantages: more pulling power, longer motor life.

Disadvantages: slower speed, less juice to each motor. (Even if you firewall it to WOT, a power-pack can only pump so much volt-amperage into the rails--unless you build your own, and that could get dangerous playing with high voltage.)

That said, all my big 10-wide designs for 9v are at least 2-motor (some steamers 3, 8-axle diesels like DD35's, C855s and DD40AX's have 4).

Edited by Diamondback, 23 August 2009 - 06:03 AM.


#6 Davey

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Posted 23 August 2009 - 06:17 AM

View PostDiamondback, on Aug 23 2009, 01:01 AM, said:

Advantages: more pulling power, longer motor life.

Disadvantages: slower speed, less juice to each motor. (Even if you firewall it to WOT, a power-pack can only pump so much volt-amperage into the rails--unless you build your own, and that could get dangerous playing with high voltage.)

That said, all my big 10-wide designs for 9v are at least 2-motor (some steamers 3, 8-axle diesels like DD35's, C855s and DD40AX's have 4).

The biggest advantage as others have said is that you spread the load over two motors.  This will definitely prolong the motor life and allow you to pull longer trains.  As Diamondback mentions above, the downside is that you are splitting the available amperage between two motors which can lead to lower speed in longer loops.  The solution to this is to either use a modified controller or...if you prefer not to modify like me...you can run two controllers on one loop thereby increasing the available amperage.  The key here is that both controllers have to be set at the same 'speed notch'.  My layout is large enough now that I have to do this on at least two of my loops.

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#7 TaltosVT

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Posted 23 August 2009 - 01:34 PM

My experience has been that two motors will add more power, but not speed.  I've used up to three motors on a single train without problems.  After three, the regulator starts to get overloaded and shuts down.

As for faster/slower motors together, they seem to be fine on the same locomotive.  If you want to spread the pulling power across a long train (say one motor in the locomotive and one in the middle of the train attached to a boxcar), it's best to have the faster motor in the front.  If the faster motor is in the back, it will tend to push the train together, sometimes causing derailments.  With the faster motor in the front, there is always tension on the train.

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#8 Modulex Guy

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Posted 23 August 2009 - 03:13 PM

Simple, MORE TORQUE!!!

You get the benefit of getting more low end grunt with two motors than with one.

Two motors are not necessary for a train that is short and light, like a passenger train, but for long freight trains, you get the power to get the train moving.

the motors do not get worn faster if two are used, because the voltage is just cut in half between the two motors rather than full power to both.
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#9 aawsum

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Posted 24 August 2009 - 07:26 PM

I have 0 experience with 9V, but I have built this in with the RC system.
I have a lot of upgoing track, and with 2 motors I am getting enough grip to pull away on a climb form standing still. With 1 motor the wheels start spinning and it will not move. As we speak, all of my trains are powered with 2 RC motors (and they are in boxes btw  :cry_sad:

Edited by aawsum, 24 August 2009 - 07:26 PM.


#10 Mark Bellis

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Posted 24 August 2009 - 11:07 PM

For anything bigger than a train set, it's 2 motors every time!

Important point though: always wire them together, so they get the same electric supply.  Otherwise one motor pushes or pulls the other over points, which will reduce motor life.

Yes, a standard 9V controller is limited to 2 motors' worth of current.  I've had one overheat after a while with only 2 motors on a light train.  I use a dual 30V 3A bench power supply for running 9V main lines - no messing with high voltages as it's a ready-made unit.  I added a couple of DPDT centre-off switches for the direction.  This PSU will easily handle double headers, 4-motor trains, locos with auxiliary motors and live train swapping (running one train into a through siding and another out of another at the same time, requiring double the current).  This last technique is useful at shows because it reduces the interrupt time between trains that the public can see running, which is what holds their interest.

When I have bought a batch of motors, I put them on a 9V circuit and run them all together, swapping any pairs as one catches up with another, till I have the set rated in speed order.  Then I pick two motors adjacent in rank (matching them) and put the faster one at the front of a 2-motor loco.  A shame this is not possible with PF train motors!

In a pair of Class 20s it was better to put 2 motors in one and run the other without any motors than to put one motor in each, even when they were wired together.  This was because the push-pull happens over points, which are on a curve, and a push together on a curve can lead to derailments because the couplings (in this case a thin liftarm instead) are at an angle to the bogies.

2 motors also use 100% of the weight of a loco as traction weight.  In a 3-axle bogie I allow the 3rd pair of wheels to swivel and tilt, so it does not carry the weight of the loco body (and hence run the risk of catching on it).  The use of traction weight is a big consideration in the design of real trains, both steam and diesel.  The difference is shown between a 4-6-2 and a 2-8-0 because the firebox and cab weight is traction weight for a 2-8-0.  An A1A-A1A diesel wastes traction weight with the un-powered wheels.

I agree about hill climbing too.  I'm sure some of the tyres on my motors have lasted longer because using 2 motors reduces wheel slip.  A single-motor small engine has noticeable wheel slip, which has worn down the tyres.

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#11 Diamondback

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Posted 26 August 2009 - 06:54 AM

View PostMark Bellis, on Aug 24 2009, 04:07 PM, said:

2 motors also use 100% of the weight of a loco as traction weight.  In a 3-axle bogie I allow the 3rd pair of wheels to swivel and tilt, so it does not carry the weight of the loco body (and hence run the risk of catching on it).  The use of traction weight is a big consideration in the design of real trains, both steam and diesel.  The difference is shown between a 4-6-2 and a 2-8-0 because the firebox and cab weight is traction weight for a 2-8-0.  An A1A-A1A diesel wastes traction weight with the un-powered wheels.
True, Mark, but when you have light rails that can only take so much weight, the A1A-A1A distributes its weight over more rail area. The increased tractive weight, IIRC, was part of why GM recommended steam-generator-equipped F-units rather than E-units for mountain operations like in the Rockies or the Sierra Nevada. (And the only reason Great Northern and Milwaukee Road got by with E's was they had electrics pulling the E's and their attached trains over the worst of the Rockies...)




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