71 replies to this topic

[Marty Stanley]

I have been wondering this of late - How did we get to the point where higher voltages like 14.1 or higher voltage is being run on slot car tracks?

When you run a battery like an 8D, it is comprised of 6 cells of lead acid technology. This technology will produce 2.17 to 2.21 volts of DC when properly maintained. In telephone companies, they have huge battery plants that supply the necessary voltage to keep the telephone switching systems functioning during power outages. Have you ever noticed that you can call the power company to ask when the power will be back on when your home is without electricity?

Some of these batteries are HUGE and trust me, quite expensive. To keep costs down, maintenance is something that is kept very strict control over. Each of the cells is read on a weekly or bi-weekly basis, recorded and sent into the responsible manager of the power systems. Along with the voltages being read, hydrometer readings and water levels are recorded. If the cell readings are not in the requited range of 2.17 and 2.21 volts, maintenance starts tight then and there. Typically the chargers are switched from "Float" to "Equalize". This higher voltage will 'shock' the batteries and help bring them back into spec.

Why don't the telephone companies run this higher voltage all the time? Simply put, it destroys the batteries by causing excessive heat in the plates of the batteries. This excessive heat causes the plates to warp which degrades the ability of the battery to hold a charge. The telephone companies typically keep a battery string up and running for 20 years.

Now we look at slot car batteries. If you maintain that 2.17 to 2.21 volts, you should read a fully charged battery at 13.02 to 13.26 volts. Remember, that if you are the high end of the reading, your batteries will not last as long as they do at 13.02 volts.

At one of the raceways we were having issues with a brand of motor that was all of a sudden reliability issues. One of our racers changed 4 motors during the course of a race. By accident, the charger was switched off one weekend. During the race no one went through a motor, the racing action was a bit slower - perhaps a couple of tenths and most of us agreed the racing action was cleaner and keener.

So I still have to ask, why do we insist on running more voltage on our tracks then manufacturers reccomend and then complain about the life expectancy of motors and such?

At a recent race during a preliminary trip, it was noted that the track was a bit tricky to get around. When we measured the voltage it was at 14.1 volts. We asked the track owner if the voltage could be dropped. Basically the charger was turned off and the track voltage was at 12.9 volts at the start of the race and also at the end of the race. A properly maintained 8D battery can handle 25 amps for 460 minutes. So a race that has Falcon 7 motors with 8 cars running draws less then that amount of power. With the race running for 24 minutes, you hardly scratch the surface of the ability of the battery's capacity.

If you really want to get 'high tech' on battery systems for slot car racing, all you need to do is set up the charger so the AC to the charger is turned off when track power is turned on and back on when track power is turned off. During a typical retro race you run 3 minutes of on and 2 minutes of off for each heat. At the end of the race you have run about 25 amps for 8 minutes without the charger being on.

Now if you consider that most tracks that have 8D batteries have two of them wired in parallel, then you can run the races twice as long or up to 50 amps for 460 minutes.

Does anyone know why we do this to our slot car racing?

[TSR]

Marty,

Well said.

If it was my raceway, i would find a technical way to limit the power on the track to 12 volts by any means, period, end of sentence.

At 12 volts of pure, regulated DC power, motors run cool, last a very long time and provide clean racing at maybe a couple tenths per lap slower.

So what?

[tonyp]

We used to run Gp7s on just batteries and the chargers on between heats and drew a hell of a lot more amps then we do now. I guess it is easier to crank up the power than make a faster motor.

It probably all came about when trackowners became engaged in the "world's fastest track" wars...

[Marty Stanley]

Phillipe,

Since the power is the same for everyone, I would also imagine the consistency between motor types would also be closer.

Do you agree?

[John Streisguth]

Marty:

In addition to a higher voltage, I'm sure if you check you will find a small amount of AC ripple from the charger. This adds to heat as well.

When I came back to slots in the late '80s after over fifteen years away, it seemed that many tracks had "qualifying voltage" pushing near 16v. I guess for track records? Made no sense to me, you should qualify at the voltage you race at.

But then they used to use special qualifying motors in NASCAR many years ago, didn't they?

[Marty Stanley]

John,

I'm sure that at higher voltages that induced AC ripple might even be higher.

Also if a charger has a bad filter circuit, the ripple is even going to be higher.

I wonder how often chargers (power supplies) are checked with an oscilloscope to insure the quality of the DC provided?

Hmmm, excessive heat from AC ripple... I would bet money that would shorten motor life!

[zipper]

Because of public demand we organized the ´92 European Championships in Kuopio with batteries capable to 17v. Never seen drivers so hurried to wind chokes on empty cans (and I had to buy a Koford external resistor controller to replace my early '70s Parma triple barrel).

After G27 it was pretty easy to gather consensus to drop to about 14v - it was good enough to smash the cars in the tricky corners.

[Hworth08]

Slot racing just gets "hung" with a standard. The standard for charging a 12 volt source is to use about 14 volts. This causes no damage to the mulitude of equiment using these voltages.

Slot racing comes along and wants the standards rewritten to preserve their motors. It ain't gonna be!

But slot racers can demand the slot motors be changed to milder winds that can operate at 14 volts. The first Mabuchi 16D motors were designed to operate on Revell's 18 volt power supplies. It's the racers that wanted hotter winds.

Slot racers aren't going to change the world standard of 14 volts. They can request milder motors that operate with higher voltage. Of course, as Philippe states, the cars will be a couple tenths slower. And the motor suppliers will resist, as they will sell less motors.

[tonyp]

Never understood the thinking of jacking up track power, then having to use a choke to lower it back down again.

[jimht]

Voltage was pretty much a local option with no standards from the very beginning.
Blame the drag racers and Bob Herrick when he was the USRA tech inspector for sanctification of high voltage.

From the USRA Rulebook:

"In all USRA events, qualifying voltage for all classes will be limited to a
maximum of 16.0 volts, and race voltage will be limited to a maximum of 14.3
volts."

He wrote the 16v max into the rules to control voltage for drag racing, thinking no-one would be crazy enough to use it as a way to justify 16v on a road course... silly optimist.

[TSR]

Jim,

Indeed that was the stupidest thing they did. It also is killing open-class racing. Amazing of imbecility in reasoning. Will it now kill Retro racing???

Since the power is the same for everyone, I would also imagine the consistency between motor types would also be closer.

Do you agree?

Marty,

It would the same situation when you have higher voltage in a way with a bit more extreme figures, but it is clear that higher voltage plus AC ripple kills our slot car motors regardless of which type.

Hence, any SANE raceway owner would be well advised to take things in his own hands and get devices to regulate track power to straight 12 volt (and not even that "magical" 13.6 or "fully charged batteries") and keep it there. Such a raceway would increase its customers base right there.

Just to give you an idea of the diff: we ran a D3 retro Pro race last Saturday art BP. The track record on basically 14 volts and a bit of ripple at the Checkpoint Cup last January is 3.24", most guys ran in the 3.6" range and several motors (the normally bullet-proof PS/X12) went poof. Saturday we ran just about 12.5 volt on tired batteries, and the speeds were 3.6" to 3.8". My own motor ran so cool I was amazed, and the loaner D3 Coupe from my friend Bryan Warmack ran virtually COLD (Falcon 7).

So the speeds were 2 to 4 tenths off "record" speeds. Who cares???

Is it not time for some sanity out there?

[Ron Hershman]

Voltage was pretty much a local option with no standards from the very beginning.
Blame the drag racers and Bob Herrick when he was the USRA tech inspector for sanctification of high voltage.

From the USRA Rulebook:

"In all USRA events, qualifying voltage for all classes will be limited to a
maximum of 16.0 volts, and race voltage will be limited to a maximum of 14.3
volts."

He wrote the 16v max into the rules to control voltage for drag racing, thinking no-one would be crazy enough to use it as a way to justify 16v on a road course... silly optimist.

Errrr, ummmmmmm, not Bob Herrick's fault in any way... just so you know as you weren't there... here is what happened back then...

As more and more tracks wanted to be the world's fastest... a situation at a race in Chicago where they were qualifying on 22 volts or pretty close to that, a piece of a exploding armature that almost caused loss of eyesight to a turn marshal, the USRA took action and came up with a voltage "limit" for USRA racing only as there had never been any limits before then.

After much discussion and meetings among USRA officials and manufacturers... the 14/16 rule came about and again... it's for USRA racing only and NO raceway has to follow USRA voltage rules.

Any raceway is free to do what they want with voltage today or tomorrow... the USRA or Bob Herrick has no control over that... never had. never will.

Raceway owners/management control the voltage... NO ONE else. Voltage ONLY has to be controlled at USRA events.

[flem1959]

I agree completely about controlling voltage.

When I was racing Box 12 it was always a motor change drill. I blew up several motors at Rick`s track.
Seems like it would be better to run a little slower, not a lot, and go eight heats on one motor.

I still like Wing cars the best.

[TSR]

So,

What is the easiest, least costly, most reliable way to control/reduce voltage for a track owner?

[PCH Parts Express]

If I install a Tilt-N-Tech the power can be turned down to 12.00v. Do you guys want that? We currently run about 13.25v.

[Marty Stanley]

So,
What is the easiest, least costly, most reliable way to control/reduce voltage fro a track owner?

Turn the chargers off during races. The voltage will be 13.02 or slightly lower on properly maintained batteries.

It don't get much cheaper then this.

No induced AC, no over power, just pure DC from a battery without the charger on.

On tracks with chargers that are called power supplies, most of the chargers I've ever seen have the ability to adjust the output. Once again a no-cost adjustment.

[Jacob Shiplet]

Well since Scott is chiming in on this, how hard is this to do? What damage is done to the batteries/track/etc? I would like to know how much this would slow down cars on a big track. Would this change cars to being full punch at some of the swoopy kings?

[Ron Hershman]

If I install a Tilt-N-Tech the power can be turned down to 12.00V. Do you guys want that? We currently run about 13.25V

If you're having problems at 13.2 volts... then by all means turn the voltage down... you will find guys running bigger pinions and still having motor issues at lower voltage as well.

Maybe lower the voltage and have a pinion rule... that should solve any problems.

[Rick]

Just like you say the race car is a complete package, so are track systems. I have had them all. The wiring harness is as important as the power source and many times, more so.

I hated the charging between heats and turning the charger off when the heat started, you would have a surface charge for 20 seconds and then back to the battery reserve the rest of the heat, unless you have multiple battery sets to suck the surface charge into the passive set for the heat it will be very up and down. When batteries are new even with a charger on the ripple is negligible, I have had an oscilloscope on the track to check this. As the battery wears out, the ripple will go up.

Many times when the car runs hot the return is just not of sufficient size although the math says it is.

I have used every kind of battery on the planet, 8Ds probably being the worst to use because it's just not correct for the application but they are reasonable and when new really pump out the voltage. Many can tell you the stories of the Nuc power plant batteries I had in the '90s. No charger at all, one day, 120 entries and they lost one-tenth of 1 volt at the end of the day, from Group 12 to opens. They were individual cells 2.2 volts each and weighed in at 80 pounds apiece. There were 48 of them under the pit tables and six 8Ds inside the infield. LOL. No charger required.

[RomanK]

Well, since Scott is chiming in on this, how hard is this to do? What damage is done to the batteries, track, etc? I would like to know how much this would slow down cars on a big track. Would this change cars to being full punch at some of the swoopy Kings?

At 12 VDC you could use a rubber band as a driver on our King on six of eight lanes.

[RomanK]

If it was my raceway, i would find a technical way to limit the power on the track to 12 volts by any means, period, end of sentence.

At 12 volts of pure, regulated DC power, motors run cool, last a very long time and provide clean racing at maybe a couple tenths per lap slower.

So what?

Running a battery at 12 VDC would be bad for the batt as it would be in some state of less than full charge to get that voltage.

[Guy Spaulding]

When we visited a track for a SoCal USRA race in the early '80s, we always had to ask about the power. "Was the big charger going to be on during practice? Quals? Races?" That would determine what winds we would use. Some of us had adopted a 30A Tophat diode for e-drop and ripple reduction.

[RomanK]

So,
What is the easiest, least costly, most reliable way to control/reduce voltage fro a track owner?

Straight power supplies would do what you are looking for perhaps adding 1 or 2 farad of capacitance, but most raceways would choke on the price of a quality power supplies capable of supplying the clean current required (lack of leakage ripple) that is so detrimental to any type of DC device.

The reason you see cheap power supplies and battery chargers under tracks is cause they are cheap and by attaching them to a battery, there is some cleaning of the lousy power those things are kicking out. Luckily the batteries do OK with that type of power but our motors do not. For whatever reason, very few raceways using poor power supplies seem to have wired their systems (batteries and power supplies) in such a way as to isolate the track from the power supplies output.

[Ron Hershman]

Just like you say the race car is a complete package, so are track systems. I have had them all. The wiring harness is as important as the power source and many times, more so.

Now we are talking... it's the delivery system of the voltage and amps.

I have raced on 14.5 volt tracks that felt like there was only 12 volts and I have raced on 13.2 tracks that felt like 16 volts.

Most tracks have built in "chokes" in the wiring system and sizes being used.

[tonyp]

The Viper Pit King has 13 plus volts but Pro Slots run like they are on 8 volts and F7s scream. The Pro Slots run red hot as well.

Something is not right. It's like there is no amperage. Their Engleman is just fine.