9V High Speed - recent experiences and questions

[Haddock51]

The recent Lego Train Meeting 2013 in Eskilstuna/Sweden provided excellent opportunities to test some of the challenges for the planned 9V Extreme project, such as high speed, power supply/power management and action pictures with my new camera waggon (see also topic "High Speed Camera Waggon - the first action pictures" and "MOC: High Speed Camera Waggon"). Testing inclinations will be done later this year.

The test track in summary:

* Two high speed tracks with lengths of 14.5 and 15 meters. Each track powered with two 9V transformers in synch. Power connections each 5 m. All 90 degree curves slightly inclined with 1x2 plates (1-2-3-2-1).

* Three train yards with 16 open side tracks (one entry) and 16 standard switches.

* Two electrically operated crossover switches and two halfcurve switches.

High speed:

All trains ran smoothly all along the tracks with no loss of speed (except in the train yards where the loss of power was significant. Why?)

Trains with double 9V engines were very fast - in particular the camera waggon! - but I expected the 4 engine powered Horizon Express and Santa Fe Express to be faster with two 9V transformers.

Question: How much maximum power can you charge for 2 engine resp. 4 engine powered trains without risking to "burn up" the engines?

The double engine powered camera waggon was charged at most with 2 transformers in synch at approx. 75 percent of maximum speed, resulting in very high speed. This should give approx. 1.5 Amps for two engines that require 300 mA. Is that "healthy"? If yes, how much more can you charge without risking to "burn them up"? If no, what is "healthy"?

Power supply:

8 out of the 12 power connections were extended/soldered with loudspeaker cables (2x1.5 sq.mm) to a total length of approx. 4 meters each.

I am still worried about the (potential) loss of power, particularly considering the fact that the Lego wires are so thin (my guess is 0.2-0.5 sq.mm). I am even more worried thinking about the need for power cables of up to 15 meters in my future 9V Extreme display.

Question: If you want to skip the Lego wires completely, you can solder loudspeaker cables directly to the rails. But how can you connect such cables directly to the 9V transformers? Has anyone tried?

Train yards:

Building multiple track train yards with standard switches is no hit, not even with open tracks (one entry). The loss of track space is simply too big. And to pull large trains through 6 consecutive switches becomes too curvy - with a high risk for derailment. As a conclusion, I have decided to build my future train yards primarily with halfcurve switches even though this will require several modified straights (1/4, 1/2 and 3/4).

Question: I am still puzzled by the loss of power when pulling trains through 6 consecutive switches - with double power connections close to the first switch?! Has anyone measured the loss of power when applying consecutive switches?

Cable management:

It became quite obvious that all cables - in particular stronger loudspeaker cables - must be properly placed (at designated spots) below the rails, and that all rails must be properly fixed to the surface (which at this occasion was not possible) in order to avoid bumps and lower the risk for derailments. This becomes even more obvious when operating trains at high speed.

Trains:

The extended Horizon Express is simply spectacular - from all angles .....

At this accasion, I also had the opportunity to use some of my (purchased) MOCs for the first time - after a Lego break of more than five years (!) - such as the Trans Europa Express (TEE) and the Matterhorn-Gotthard Bahn. It was also fun to see the Emerald Night - at relatively high speed - and the extended Maersk container train in action, not to mention the Santa Fe....!

And finally: 9V and high speed - the ultimate Lego Train combination!

Edited March 21, 2013 by Haddock51

[alainneke]

One word: Impressive!!!

All trains ran smoothly all along the tracks with no loss of speed (except in the train yards where the loss of speed (power) was significant. Why?)

The loss of speed in the train yards is probably due to the large amount of curves and associated friction.

Question: How much maximum power can you charge for 2 engine resp. 4 engine powered trains without risking to "burn up" the engines?

According to Philo, a loaded 9V motor draws about 0,40 A. One (1) speed regulator should thus be safe for a 2 engine powered train, while two speed regulators should be safe for 4 engine powered trains.

The double engine powered camera waggon was charged at most with 2 transformers in synch at approx. 75 percent of maximum speed, resulting in very high speed. This should give approx. 1.5 Amps for two engines that require 300 mA. Is that "healthy"? If yes, how much more can you charge without risking to "burn them up"? If no, what is "healthy"?

Using 2 speed regulators for 2 engines shouldn't be a problem, as the regulators will only provide the current that's actually drawn by the engines (in this case 600 mA). However, problems may occur when one of the motors gets stalled: the motor will draw all available current (1,5 A) and burn up.

Power supply:

Question: If you want to skip the Lego wires completely, you can solder loudspeaker cables directly to the rails. But how can you connect such cables directly to the 9V transformers? Has anyone tried?

You could try to open up a regulator and solder a piece of cable directly to the pads leading to the 9V connector plate. Lead this cable through the housing and use some screw connectors to connect it to the rest of the wiring.

Question: I am still puzzled by the loss of power when pulling trains through 6 consecutive switches - with double power connections close to the first switch?! Has anyone measured the loss of power when applying consecutive switches?

6 consecutive switches roughly equal 12 alternating curves: this causes a lot of friction and drag!

[Haddock51]

Thank you alainneke for your comments which are very much appreciated.

As you can read between the lines, power and power supply remain the key challenges. I will have to get back to your previous comments re "9V Extreme" and this entire DCC theme.

I would also like to study this personally on sight in order to get a better understanding of potential alternatives.

[hoeij]

High speed:

All trains ran smoothly all along the tracks with no loss of speed (except in the train yards where the loss of speed (power) was significant. Why?)

Trains with double 9V engines were very fast - in particular the camera waggon! - but I expected the 4 engine powered Horizon Express and Santa Fe Express to be faster with two 9V transformers.

The trains slow down a lot in the train yard because the electricity is coming from only 1 direction, so if you calculate the electrical resistance (the number of Ohms) then it will be a lot higher there. Some of the switches

could also have a noticeable amount of electrical resistance (it varies quite a bit).

In a 9V train, adding more than 2 motors does not always make the train faster, this depends a bit on the power supply and the track itself. If you're on a part of the track that is electrically far away (i.e. counting in Ohms, not in meters) from the power supply, then having more motors leads to a larger drop in voltage (drop: comparing the voltage at the power supply with that at the motors). This larger drop in voltage means that you don't see the speedup you would expect from having an extra motor.

For my layout, I have measured the current that the trains use (note: in a curve they use more than on the straights). I use that data to calculate how many track connections are needed in order to avoid significant slowdowns.

Edited March 20, 2013 by hoeij

[hoeij]

The double engine powered camera waggon was charged at most with 2 transformers in synch at approx. 75 percent of maximum speed, resulting in very high speed. This should give approx. 1.5 Amps for two engines that require 300 mA. Is that "healthy"?

This question suggests a misunderstanding of current vs voltage.

The transformers don't determine the number of amps (the torque that the motors need to deliver determines the number of amps). The transformers only determine the number of volts.

So a 5 amp transformer is no more risky for the motor than a 1 amp transformer.

On the other hand, 20 volts is a lot more risky than say 8 volts.

The main thing you want from your power supply is this: That it delivers a constant voltage. When the train goes through a curve, it encounters more friction. This extra friction translates in more torque that the motors need to deliver. This extra torque translates into more amps. Due to electrical resistance, the extra amps cause the effective voltage to become lower; and that lower effective voltage is the reason that the train slows down in a curve.

Several things contribute to this lower effective voltage: (1) electrical resistance in the motor. (2) electrical resistance in the track (3) electrical resistance in the transformer.

A good transformer is one that behaves as though it had no electrical resistance (meaning that its voltage stays the same even if the number of amps goes up). The 9V controller does in fact behave like that, up to about 500 mAmp or so it behaves very well. If it is asked to deliver say 700 mAmp, it can do that, however, then its output voltage starts decreases and trains slow down more in curves than they have to (at such a load, things will work better with a 2nd controller added to the track).

PS. High quality industrial motors have very little electrical resistance; and if you keep the voltage the same, they stay at essentially the same speed, even if you drastically increase their workload.

Edited March 20, 2013 by hoeij

[Haddock51]

The trains slow down a lot in the train yard because the electricity is coming from only 1 direction, so if you calculate the electrical resistance (the number of Ohms) then it will be a lot higher there. Some of the switches

could also have a noticeable amount of electrical resistance (it varies quite a bit).

In a 9V train, adding more than 2 motors does not always make the train faster, this depends a bit on the power supply and the track itself. If you're on a part of the track that is electrically far away (i.e. counting in Ohms, not in meters) from the power supply, then having more motors leads to a larger drop in voltage (drop: comparing the voltage at the power supply with that at the motors). This larger drop in voltage means that you don't see the speedup you would expect from having an extra motor.

For my layout, I have measured the current that the trains use (note: in a curve they use more than on the straights). I use that data to calculate how many track connections are needed in order to avoid significant slowdowns.

The main train yard in my future layout will have only closed tracks with double entries which hopefully will solve some of the power supply issues there.

Please watch the video under topic "High Speed Camera Waggon - the first action pictures". Running a unit such as the camera waggon with 2 engines and powered with 2 transformers makes a real difference - you can both see and hear it! I could also increase the speed considerably for the Santa Fe and the Horizon Express, both equipped with 4 engines (I refrained from maximum speed to avoid derailing in the narrow curves).

Based on previous advice (see topic "9V Extreme"), I mounted power connections each 5 m which worked perfectly in terms of not loosing speed.

[Haddock51]

This question suggests a misunderstanding of current vs voltage.

The transformers don't determine the number of amps (the torque that the motors need to deliver determines the number of amps). The transformers only determine the number of volts.

So a 5 amp transformer is no more risky for the motor than a 1 amp transformer.

On the other hand, 20 volts is a lot more risky than say 8 volts.

The main thing you want from your power supply is this: That it delivers a constant voltage. When the train goes through a curve, it encounters more friction. This extra friction translates in more torque that the motors need to deliver. This extra torque translates into more amps. Due to electrical resistance, the extra amps cause the effective voltage to become lower; and that lower effective voltage is the reason that the train slows down in a curve.

Several things contribute to this lower effective voltage: (1) electrical resistance in the motor. (2) electrical resistance in the track (3) electrical resistance in the transformer.

A good transformer is one that behaves as though it had no electrical resistance (meaning that its voltage stays the same even if the number of amps goes up). The 9V controller does in fact behave like that, up to about 500 mAmp or so it behaves very well. If it is asked to deliver say 700 mAmp, it can do that, however, then its output voltage starts decreases and trains slow down more in curves than they have to (at such a load, things will work better with a 2nd controller added to the track).

PS. High quality industrial motors have very little electrical resistance; and if you keep the voltage the same, they stay at essentially the same speed, even if you drastically increase their workload.

Thank you very much for this information!

The main purpose with these tests was to get more knowledge and experience for the huge 9V Extreme project with significant inclinations and a total track length of approx. 175 meters (see topic "9V Extreme") that will start later this year.

In this topic, I got a lot of imput re power supply and power connections. Some of the power connections will be as long as 15 m from the transformers which also raises questions re the size of these cables (I will most likely only use loudspeaker cables 2x1.5 sq.mm and solder them directly to the rails and directly to the transformers).

I don´t know yet about the additional resistance due to the inclinations (approx. 8 percent) but in my previous display, I had no problems to pull up a 4 engine powered Santa Fe with 2 transformers in synch all the way up to the top with the same inclination (the major problem I experienced was the loss of speed due to long track distance and too few power connections).

I am not an expert in electrics so I will need to learn more in detail how all these parameters are linked together. Just to give you one thought: How would you calculate torque, resistance, voltage and amps for a 4 engine powered extended Horizon Express (with a total weight of approx. 3 kg) to get it up inclination sections of 4m with 8 percent inclination? Where would you expect bottle-necks - and how would you overcome/prevent them? If the primary objective is to maintain constant voltage then it seems like I am back to the key question of number of transformers needed, or?

I would really appreciate to get more facts and data on this equation.

Edited March 21, 2013 by Haddock51