Motor Possibility

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TinGoat
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Re: Motor Possibility

Post by TinGoat »

I don't know if it's true but I had heard that you can't use DCC on coreless motors.

That may have been true a few years ago but maybe DCC has improved their sin wave dc since then.

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AstroGoat760
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Re: Motor Possibility

Post by AstroGoat760 »

Those possibilities are definitely tempting to find more out about!
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Re: Motor Possibility

Post by ConducTTor »

Hey Bernd (and anyone else who has experience), what is your experience with twin motor drives? I've thought about this solution but have been concerned about the two motors not being exactly in sync (where one boggie is dragging the other and the other is holding the first one back).


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Re: Motor Possibility

Post by ConducTTor »

Also, does a dual motor setup require two decoders?


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Tom Dempsey
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Re: Motor Possibility

Post by Tom Dempsey »

In O Scale, the two motor set up is referred to as a "China Drive". It is extraordinarily unpopular and generally disdained by builders. The minimum fix is to connect the motors in series rather than in parallel as shipped. Only one decoder is required. Builders pretty much seem to universally go with a single horizontal drive. Faulhaber, et al, put out gear head motor setups. Very small, very powerful, very torquey, very small current draw, very cool running, very quiet, very expensive.

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Re: Motor Possibility

Post by ConducTTor »

What is a gearhead motor setup?


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CFRiad
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Re: Motor Possibility

Post by CFRiad »

ConducTTor wrote:[...]what is your experience with twin motor drives?
ConducTTor wrote:Also, does a dual motor setup require two decoders?
krokodil wrote:Normally the motors are never equal, ie there is almost always a slip between the two drives, what reduces heavily the efficiency of the whole construction. Some people were trying to equalize the performance of the two motors with two decoders but I never heard about big success stories.
First rule of engineering: two identical systems are never identical. With dual motors, there are differences in the motors themselves and in the gear trains. If using separate decoders, there are differences in the decoders too.

With this out of the way, let's say that it can be done. It may be labour intensive and convoluted, but not impossible. Basically one needs to speed match the two trucks. It is easier if the two motors are on separate frames, such as an articulated unit. For a rigid-frame loco, I would use two decoders and build two temporary identical frames, each with a driven truck at one end and an idle truck at the other. Then I would speed match the two frames, making sure one truck runs in reverse.

There are quite a few websites demonstrating the principles of speed matching for consisting.

With that done, I would install the trucks in the loco and voilá, dual drive. It will never be perfect, there will be some slip, but within acceptable limits. Don't forget, it's a toy, not a life-critical piece of equipment.

Even on the prototypes, there is always a slip between the 4 or 6 motors. The locos with DC motors and pulse-width modulation drives have electronics that monitor the slip and regulate the current to individual motors. The machines with 3-phase asynchronous induction motors and variable frequency drives regulate themselves (sort of).

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CFRiad
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Re: Motor Possibility

Post by CFRiad »

krokodil wrote:As already mentioned two units never worked identically. The problems was always with the start-up, when one of the locos did not started at the same voltage ( what is almost always a case) the better engine started earlier and tried to pull the next locomotive(s) and the whole train.
This is very true for DC.

The problem can be mitigated to a satisfactory (not perfect) level in DCC. If DCC locos are speed matched correctly, they will run fine at all speeds. The only problem that remains with multiple DCC locos in consists is poor current pickup from the track. If, at low speed, one of the locos loses power momentarily, the consist jerks.

Since here we are talking about dual drives on one loco, both decoders can be powered in parallel from all pickups so they will both lose power at the same time or not at all.

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CFRiad
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Re: Motor Possibility

Post by CFRiad »

Bernd wrote:Guess I better yank the motor and gears out of the Cow, the one without the cab, on the TR2 project since they won't play nice together.
Bernd, everything I read so far in this thread, makes me guess that you are running DC. If this is the case, your life will be much easier with a motorless Cow.

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Re: Motor Possibility

Post by dileTTante »

ConducTTor wrote:Hey Bernd (and anyone else who has experience), what is your experience with twin motor drives? I've thought about this solution but have been concerned about the two motors not being exactly in sync (where one boggie is dragging the other and the other is holding the first one back).


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As you know already, the Brawa E95 in TT is basically two locomotives joined together as one. It has a motor and decoder in each unit. The drive in one unit is connected to the other by cardan shaft. This works. The only electrical connections between the two locomotives are for the front and rear lights and for track power.

The units separated run nearly identically. They could be timed and adjusted separately as though in consist. They can be programmed separately but I found that just programming the two units at the same time as one works well enough, possibly thanks to the cardan shaft.

Also as food for thought, the old American Flyer S scale Alco diesels have a motor on each truck, the two motors completely independent from each other. I've haven't read any criticism of this method.

- Terry C

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