[Barry-TJetSlots]

Update: I've added a second power tap and reduced the voltage for each of the two supplies to 20.4 volts. Cars are running very smooth, constant speed and no stops. I may eventually add a 4th power tap.

 

[X2slotbob]

"A power supply with more amp capacity is not a cure for a track with bad joints."--Rich D

Agreed, a point I have long made.

However, this time my point was a little different. On a long track with good joints there is increased resistance inherently, correct? If so, it would seem that more amperage (to overcome those additive losses) would be a good thing.

Do you concur?

 

[X2slotbob]

" [Added a power tap, and] tested with one of my slower cars and it makes a difference...I've added a second power tap and reduced the voltage for each of the two supplies to 20.4 volts. Cars are running very smooth, constant speed and no stops."--Barry

Ah yes, the real world. Thanks Barry.

 

[jordan89]

IF it is at one particular point you have a connection problem and I would suggest that NEITHER adding power taps nor more voltage (or amperage, for that matter) will help.

If you have an area of the track where there is a 'bad' connection for whatever reason then the easy fix is to solder or use spades and just connect the 4 rails together under the track between the two pieces in question, whether or not you would call these joins power taps I don't know but probably they are...

 

[Barry-TJetSlots]

If you have an area of the track where there is a 'bad' connection for whatever reason then the easy fix is to solder or use spades and just connect the 4 rails together under the track between the two pieces in question, whether or not you would call these joins power taps I don't know but probably they are...

Usually when I have that problem, I clean the connector terminals or I just replace the questionable track

 

[X2slotbob]

"If you have an area of the track where there is a 'bad' connection for whatever reason then the easy fix is to solder or use spades and just connect the 4 rails together under the track between the two pieces in question, whether or not you would call these joins power taps I don't know but probably they are..."--Jordan89

Yeppers. And Tyco track rail interface is essentially two flat blades lying against each other. In a humid climate (ie here), they frequently corrode.

And since my track is permanent, and I don't know which joints will become 'bad' over time, I did that with virtually all of my track connections, effectively creating four big pieces of track. They were then finally soldered together from above at the joint per se.

I used small gauge solid wire. It was tedious and redundant, but it is done.

 

[RichD]

The longer the track is the more important the resistance of the rails themselves will be. The voltage drop is the problem, not the lack of amperage. The voltage drop due to the resistance of the rails will vary with the resistance of the rails and the amperage in the circuit, which is dictated by the amount of current that the cars want to draw. Cars with low ohm motors will want more power, the amps will go up and so will the voltage drop across the rails. You could measure the voltage under load at the far side of the track and crank up the voltage, but if you do that the higher voltage near the power strip might make the cars more difficult to drive there. I would expect that if the voltage drop was under 1 volt most people could live with that. A few fanatics would want a zero voltage drop. I did have a problem with my MaxTrax, those are sectional, but the sections can be as much as 46 inches long and there are only 23 joints. The keys that join the sections are an inch long, and the rails are thicker than the standard Tomy/AFX ones. My track is about 50 feet long, but there is a set of dead strips next to the power strip. When a car crossed the dead strip there would be 100 feet of rail between the power supply and the car. That was OK as long as I was running set type cars with 6 ohm armatures. When I got a Restricted Open car, that could pull perhaps 2 amps as opposed to 0.5 amps, so the car would hiccup when it crossed the dead strips. The fix was to add one set of jumpers after the dead strips. If I was not using dead strips I might not have had a problem. At that time the track was powered with a pair of 8.6 amp laboratory grade regulated power supplies with each one doing two lanes.
Note that the latest MaxTrax have L shaped rails with twice the cross sectional area of conventional rails.

 

[X2slotbob]

"Cars with low ohm motors will want more power, the amps will go up and so will the voltage drop across the rails." "The voltage drop is the problem, not the lack of amperage." --RD

So...are the above statements mutually exclusive or... causative?

 

[RichD]

Causative, I believe. Providing that your power supply has enough power, a car with a more powerful motor will draw more amps. The more amps that are going through the circuit the greater the voltage drop due to the rails will be. A person with nothing better to do could disconnect the track from one side of the power strip and measure the ohms. If all of the joints are good the voltage would be lowest at the part of the track that is furthest from the power strip and the power to the car would actually be coming from two directions at once. Also remember that the power comes from the power supply, goes through the track wiring, the controller and one rail through the car's motor, then back through the other rail and wiring to the power supply to make a complete circuit. To simplify things just measure one rail. Since you can expect a set type car with a 6 ohm armature to draw 0.5 amps, if the rails were to measure 1 ohm the voltage drop would be 1/0.5 or 2 volts, I would consider that to be significant.

 

[X2slotbob]

I concur, of course.

So, let's see. A 20v Aurora powerpack that has a real world slot car load on it immediately runs short of amps upon startup, and therefore the voltage drops to try to compensate. Got that. Meanwhile my Astron ham supply has no appreciable loss of voltage due to it's ability to deliver 10 amps of power.

Extrapolating (maybe incorrectly), if one has a looooooooong DHORC style track, lets say new track with good joints, there is presumably some "loss" of power as the car gets further away from the terminal track due to additive resistance. Is that analogous to the heavier-load-than-the-powerpack-can-handle example above...?

The question is, would say, 100 (or pick your number, we have plenty in theoretical land) amps of 20volt power be enough to maintain the 20volts at the furthest point?

 

[MrFlippant]

Yes, it will have 20v, but that's not what we're talking about. The car will not be able to pull clean power from that point, even if you had a car battery powering the track. There will be power (amp) loss, even at infinite amps. The voltage (20v) will not drop, but the power will not pull as efficiently through so much resistance, and the motor will take longer to reach its ultimate speed. The final speed will be the same (volts), but the ability to reach that speed will be diminished (amps) due to resistance. This is why bigger power supplies are NOT the cure for power loss due to sectional track connections. Only power taps resolve that issue.

 

[merkit the grof]

Surely it's the other way round isn't it? There will always be a voltage drop at the far end of the track because the track resistance is greater there causing the drop.
Incidentally power taps can only reduce the issue, not eliminate it entirely.

Joel

 

[MrFlippant]

I guess it's both? But you won't be able to measure the voltage drop without a load. That's why you can't just go around with a volt meter to find where the problems are, or if there's even a problem to begin with.

I'll be honest, I'm not educated in electronics. All I know is that unless you add power taps, it doesn't matter how great your power supply is. When you have a lot of connections between the car and the controller output, especially when some of those connections are not so good, the car just don't got much oomph. Why is that? To the layman (me) it doesn't really matter. All that matter is how to fix it. Add the power taps, and move along. I added power taps galore AND soldered jumpers across every join. If there is any power loss on my track, it will take some fancy equipment to detect.

 

[jordan89]

Surely it's the other way round isn't it? There will always be a voltage drop at the far end of the track because the track resistance is greater there causing the drop.
Incidentally power taps can only reduce the issue, not eliminate it entirely.

Joel

If you have no power taps and a layout that depends on track pieces physical electrical connections (over the 4 rails for 2 lanes), even if you solder every piece of track together then you will still get voltage drop from the source supply, maybe more if you use thin wire to fix a dead connection but have dry/sloppy solder joints between two track pieces.

Power taps reduce voltage drop as they take voltage from source (or as close as), and deliver voltage direct to the tap, not through metres of track to get to that piece of track (resistance), so somewhat negating the drop, using thick wire also helps the cause.

If you want a track with as little as voltage drop as possible (practically none), then rather than solder all the track pieces rails together solder taps from source to every piece of track using 10 AWG.

 

[jordan89]

I concur, of course.

So, let's see. A 20v Aurora powerpack that has a real world slot car load on it immediately runs short of amps upon startup, and therefore the voltage drops to try to compensate. Got that. Meanwhile my Astron ham supply has no appreciable loss of voltage due to it's ability to deliver 10 amps of power.

Extrapolating (maybe incorrectly), if one has a looooooooong DHORC style track, lets say new track with good joints, there is presumably some "loss" of power as the car gets further away from the terminal track due to additive resistance. Is that analogous to the heavier-load-than-the-powerpack-can-handle example above...?

The question is, would say, 100 (or pick your number, we have plenty in theoretical land) amps of 20volt power be enough to maintain the 20volts at the furthest point?

One thing to keep in mind for people racing digital is that a clean signal is important, bumping up voltage will not help a digital chip that is struggling to receive it's data due to poor connectivity in rails, if anything signals will get more noisy and prone to failure/runaway with earlier revisions.

There really is no other solution other than taps.

EDIT: apart from copper taping rails etc...

 

[RichD]

It is the car motors that draw power, not the track. The track rails have resistance and that will cause a drop in the voltage the further you get from the place where the power comes in. Poor track joints are usually a much bigger problem however. If you try to compensate for the voltage drop by cranking up your power supply the cars are likely to become difficult to drive when they are close to the power strip.
DC motors draw a lot more power when they first start up than they do once they get up to speed. The starting amperage is difficult to measure, but it can be calculated if you know the ohm value of the car's armature. For a motor with a 6 ohm armature and an applied voltage of 18 volts that would be 3 amps. I have measured the draw of a regular set type HO car with a 6 ohm armature as it circulates around the track. That is about 0.5 amps when the car is accelerating off of a corner and 0.25 amps when it has reached top speed. If you were doing a race on a four lane track the cars would need a total of 12 amps for an instant when the green light came on. If you had a regulated 10 amp power supply you might see a slight dip in the voltage at the start of a heat. In practice 10 amps would be sufficient for a four lane track, even if you were running high performance cars. On the other hand, a vintage 20 volt Aurora power supply will drop down to 14 volts with a 0.5 ohm load.
In case you were wondering my own track is powered by two 20 amp regulated power supplies with each one connected to two lanes.

 

[X2slotbob]

"Rather than solder all the track pieces rails together solder taps from source to every piece of track using 10 AWG."--Jordan

Yep, that would do it!

Found a way to describe what I have learned: A local power plant powering the town of Mayberry (pop 56) may be able to get away with relatively small wires on the poles. But Atlanta? Even if you ran more amperage through Mayberry's wires it would not cut it. You need bigger cables. I get that .

Now, if your slot track is long enough it is analogous. Clearly, rail size is a given, and therefore the only solution is to run taps--essentially decreasing resistance.

 

[Barry-TJetSlots]

Amazing how this topic has generated such great follow up discussion. Back to my real world experience and after testing the track for a few days, I'm going to stay with the two power tops for now. To the points of the discussion, the total circuit consists of a voltage source power supply in which the current will vary depending on the load impedance. The impedance of the car (at steady state) can be assumed to be fixed. The controller varies its impdeance to increase or decrease the current to the car. The track is therefore the other variable resistance. At the midpoint of the track should represent the highest impedance assuming a constance impedance at each section. But that typically would typically not be the case because of the potential variable of the track condition and contacts. As the total impedance increases, the current through the circuit will go down from the contstant voltage source and the power distributed to the car also goes down (P=I2xR). WIth the tap, resistors are now in parallel thus reducing the overall resistance and resulting in increased power to the car.

 

[X2slotbob]

Yeah, all that too.