I am just getting into HO racing and am in the process of building a small 4' x 8' layout with AFX track. I have been trying to decide what I want to do for lap timing and have a question about dead strips. I have read that the easiest way to create a dead strip for an HO track is to take a short section and remove enough rail that it does not make contact with the previous or next section. My question is how long does the track section need to be? Will a 3" section be enough or do I need to go with a 6" section? The layout I am building is the one that Gregory Braun has on his site that uses the Super International and 4-way Split track sets. I plan on having the lap counter in the middle of the main straight so it will be the fastest place on the track.
If you take a 6" section of track and cut 1" of the rail off of each end the result will give you a 4" sensor section which should be more than long enough to use... Of course you need to mount this at one of the fastest places on the track so you do not end up with stalled cars...
I hope this has been some help...
I hope, the translation from German to English does not alter the basic meaning of my post:
The lap timing circuit is connected to a small power source. Negative and Positive poles both lead to one of the insulated pieces of rail, thus the electric circuit is interrupted and no current is flowing. Now, if the car runs over that insualted part, the circuit is closed from the left to the right rail (or vice versa) via the pickups and the motor, current flows and this leads to the impulse.
Basically, what you assumed, but the motor does not act as a power source (generator) itself but rather as a bridge.
What you had in mind is the wiring for brakes; after the throttle is released, the arm still turns, acts an generator and the so produced energy is immediately led away through the rails which leads to the wanted brake effect.
Oughh, that was a hard one to translate - hope you understand what I mean.
Regards from Switzerland
Last edited by h0slot.ch; 10-23-2008 at 07:50 AM.
Reason: typos - as usually...
1>are you using mechanical or computer based timer?
for the mechanical timer 3 to 4 inches of dead section rail should be enough
for computer based system 2 to 3 inches should be enough
2>what the car does is to complete the circuit. when the circuit is completed
the counter will count.
for example, on a computer system, resisters are in place to prevent power from backing down the wires from the track to the computer.
on most mechanical systems, you need more current than a rolling car will produce so a seperate power supply is used. I have seen some dead sections that provide as much power as the track PS so that the car will not stop on the dead section.
I have seen a problem with dead strips if the rails are still close enought between the dead strip and rest of the track were a pickup shoe can bridge over, it has caused reading problems on computer base systems. Make sure the gap is wide enought from the start and finish of the dead strip so that no voltage and be carried over from the track.
I would go with a computer base counting system with IR's, not hard to build really, it's so easy that even a caveman can do it. Go to the following site: http://www.hoslotcarracing.com/
About any old computer that can run dos will work. All Inferred Parts needed can be gotten at Radio shack.
If you don't want to do the work then go to Trackmate.com and buy their ready made cable and software sets for around $50.00 or so and you are ready.
The dead strip system works best with 1/24 scale. It can be very hard to soldier the wires onto the rails unless you have good skills. Also you should carry an extra set of wires under the dead strip so that there isn't a break in the track circuit. I feel all and all that it can be harder to setup the dead strips than the IRs.
The dead strip is the cheapest, the IR is nicer and so are reed switches, why, no stalls!!! It's your call.
Last edited by slotcarjames; 10-23-2008 at 09:23 AM.
My MaxTrax has a dead strip connected to a TrikTrax counter/timer. A four inch dead strip is plenty. There are a few things that you need to know about dead strips. The first is that they are polarity sensitive. As a car is coasting across the dead strip its motor is acting as a generator and if the dead strips are connected the wrong way the computer will miss laps when the car is moving fast. Be sure to connect each lane the same way, if you have a problem you just reverse everything. The second issue is that you do not want track voltage to get to the computer's port or it will get burned out. There should be a 3/4 inch guard strip on each side of each dead strip. Some people also put a resistor in series with each dead strip. If you were to use TrakMate it has an extra cost dead strip option.
Can I assume that dead strip works because for the brief moment that the DC motor is not running it becomes a generator and sends a plulse to the timing system?
A couple of years ago I built a set of deadstrips for someone because they were "foolproof"... I had assumed that all the car did was complete the circuit across the rails to count a lap. The counter would see the circuit closed and count a lap.
Unfortunatly the computer system used actually was looking for voltage created by the unpowered car crossing the rails. (unlike a stand alone counter i.e. TrikTrax or other...) And TJets with weak magnets sometimes would not register. After playing around with the system (and a couple of phone calls) this was figured out...
So much for foolproof... lol
Most tracks I race on have a light bridge and sensors. I have seen computer problems, but never a sensor problem after it is set up
My own dinky track uses reed switches. No problem with these except when i run a high end magnet car that will sometimes trigger two lanes at once. But that can be fixed by glueing finishing nails next to the reeds to divert the magnetic force...
I just have never botherd to do it... lol
But like anything else, your mileage may vary...
I was thinking about using the IR harness from TrakMate but thought the dead strip might be a better option because of other cars accidentally tripping a sensor. The more I think about it I think I will stick with the IR sensors since the time will be in the middle of the main straight. A car shouldn't be swinging out into another lane by then and hopefully deslots at that point will be minimal.
If I decide that I like HO I will likely by a MaxTrax at some point so it is good to see that RichD says that the dead strip section they make works well.
I had a dead section and a light bridge working at the same time.
I thought the light system was fine till I started using both systems in a race.
Found out that some once in a great while the light system would miss a lap.
it did seem to follow certain paint schems, but was still random and usally no more than 1 lap.
The middle of the straight does not matter about flying cars unless they are T-jets
Car will still fly through counters in the middle.
heck i saw a car land under a bridge stop and spin right under the sensors
My computer system look for circuit completion: ie here is some info from trakmate:
From the main menu select 'Diagnostic - Sensor Test '
Test each lane by touching the wires together the Triggered counters should count while the wires are touching. When they are not touching only the Not Triggered counters should count. If all lanes work proceed with connecting the cable to the dead strip.
also from trakmate
Dead Strips is another method used for detecting cars in lap counters.
A Dead strip is a section of track 2 to 3" long (4" to 6" for 1/24 scale), which has no power (dead) and both rails are isolated from the track power. Many HO racers use a short piece of track and break the electrical contacts at each end to make the dead strip. Then wires from the lap counter are soldered to both rails in each lane. When the car crosses the dead strip it is detected by the lap counter. Only TrakMate cables sold as Dead Strip (DS marked on connector) compatible should be used on a Dead Strip. Using cables not designed for Dead Strips will not work properly. The advantages of using the Dead Strip is that no overhead light is required and it is not possible of trigger the lap counter with your hand. It also works with all types of slotcars.
As the author of the FSMRA article I can say that all three systems (dead strip, reed and IR) can be made to work and can be made to fail. I have used all three over the last 30 years or so and definitely prefer IR. What I have seen is that the type of Infrared LED is key and can lead to success or failure Infrared LEDs emit lights in discrete wavelengths. The most popular types are 850 nanometer and 950 nanometer. The detectors favor 850 nanometer LEDs as that wavelength is closer to their sweet spot. The 850 setups use less power and work better. Nuff said.
Check the Siberia Racing web pages for more.
lebTAZ, if you go with dead strips with the MaxTrax remember that you may want to put jumpers around them. I have the dead strips right next to the power strip and that was never a problem until I ran an RO car, in that case I could see a slight power drop after the dead strip because power had to go all around the track (51 feet) at that point. It is easy to add jumpers to a MaxTrax because you can solder them to the keys that hold the sections together. The other thing to do would be to have the power strip half way around from the dead strips. Some people just order a second power strip to avoid making jumpers.