Anyone using magnets on the bottom of frame to help trigger a slow red light? If so, how effective are they, or are they not worth the trouble to have them on board?

I don,t know about magnets but I picked up a way to get them changed when at the lights solo,they also have a sensor ( here in ozz) I always flash them with my high beam and it sets them off 100% everytime I do this

In the USA, flashing high beams doesn't work, because emergency vehicles use a pulsed strobe which sends a digital light pulse code that changes the lights for them.

And you can't buy the unit as a civilian.

Also, at least here, our road sensors measure mass, not pressure, not magnetic. They pick up the ferrous content of the magnets people have tried making them think they are magnetic sensors. They pick up the mass of ferrous metal, like a car has lots of, like engine, frame, drive shaft, bumpers, exhaust, etc.

Bikes have little of that, so if the sensor is set too high, it won't "see" the bike.

Sometimes dropping the side stand, or levering a center stand down enough to touch is enough ferrous mass to set the sensor off (cause it to trigger).

Here in America its popular to lay a wire loop in the road as a sensor. You may have read Hub and I speak of such... its called a Hall effect sensor.

Basically a large vehicle with all its metal projects a large magnetic field. A coil buried in the road can perceive this field. Not so with the modern version of a hyper bike. Lots of aluminum combined with a mind toward lower mass precludes this bike from tripping traffic sensors.

A product marketed as a solution to invisibility to traffic sensors is nothing more than a strip of magnets to glue on your bike.

Save your money. Buy a thirty cent neodymium magnet and place it in your belly fairing.

Hey Zach;
What about that light coming down 19N turning left going to racetrack road.I got a ticket there for blowing that light.Wonder if anything would work there.
Craig

If you see a hexagon cut into the road right before the white stop line that's the sensor.

Pa law allows you to ignore the signal if you sit thru two cycles and not get your turn.

And... hi Craig! Did you see someone here got 9300 miles out of their M5s?! I didn't get 2700!

I turn my bike at a 45 degree angle to take up more width in front of the light.... works every time. (I'm in NY)

Ivan

I just pull a 10 sec stoppie and the sensor is in such shock at feeling such a magnificent piece of artwork stand on it's head that it succumbs to awe and just lets me through...works every time, not just in NY ;-)

Here in FL we have the magnetic field sensors and ones that are affected by headlights like Bean has and yes the magnets work for the magnetic field one’s just make sure you get neodymium magnets because the magnets on your fridge don’t work so well!

Wonder if you can do a wheelie and hit the sensor,or do a burnout on it?hmmmm
Craig

Zach;
I saw that.My bikes 3 years old with 7000 miles.On my 3rd rear tire that looks 80percent.2nd front tire.I cancelled my tire change.I looked at it real good and it's just not that bad.It has about 4800 miles which isn't bad for a softer tire.It's a Pilot Power 2CT.Neighbor did a burnout in his truck the other day.He said I thought you would bring your Mustang over.I told him I didn't want to piss everybody off.Then I held the front brake while I was dropping the clutch.Smoke was rolling everywhere.I still get a kick out of that.
Craig

Bean has

Ferrous material disturbs an external magnetic field by concentrating it within the ferrous structure thus altering its intensity and path. Hall effect creates a transient current and voltage difference across a usually non-ferrous (like aluminum) conductor's surface by virtue of relative motion with an external magnetic field; the transient current creates its own magnetic field. How the Hall effect could possibly work with both the field and the cycle at rest with respect to each other is a mystery. The use of a powerful magnet to compensate for lack of ferrous in a cycle's body and thereby distorting the external field could serve as a trigger.

In Illinois for 2012, the authorities legalized cycles to go ahead thru a red light after waiting unsuccessfully for an "appropriate" time period for a "smart" light to change and visually verifying that no other traffic is incident on the intersection. I was doing that anyway as long as there were no police in sight.

I haven't tried the magnets but have been told by others that they work but effectiveness depends on strength and sensor nearness/sensitivity under the pavement.

Vehicle loops (round or diamond shaped) are simply a coil of copper wire. The asphalt is cut, using a wet saw & diamond blade. A single conductor (#14 RW90) is installed in the road surface to create a loop of 4 turns. The loop is tarred in place.
Inside the traffic cabinet is a loop detector. A loop detector creates a high alternating frequency. When connected to a loop, a resulting "monitoring" current flows. The loop wire itself has very little resistance. But the fact that it is coiled makes it an inductor (an open air inductor). An inductor resists the change of current in a circuit. In an AC circuit this resistance to the change of current is called Inductive Reactance.

When you drive your car or motorcycle over a loop the ferrous metal in the vehicle makes the loop a better inductor by giving the coil a core. This increases the inductance of the coil and the inductive reactance increases. As a result the current flow (monitoring current) drops. The detector senses the drop in current and provides an output to the traffic controller ("a call") for the vehicle phase associated with the loop / lane.

The problem is that vehicles are being made with less ferrous metals these days. All properly adjusted loops can and will pick up a motorcycle. Either the frequency, sensitivity, or both need to be adjusted. Call your City Engineering Dept and report the detection failure and ask them to resolve the "dangerous" and unsuitable situation.

It is the length of the core extending above the loop that has the biggest effect. Keep your fork tubes, exhaust pipe, center stands, kick stand, inside the loop.

Spyglass

That sounds valid to me and the fact that the external (to the vehicle) field is being generated by a high frequency
alternating current means that the field has a relative velocity and a reversal in polarity in the region of the vehicle. The resulting change in flux density caused by the concentration of the "core" is responsible for changing the reactance. At sufficiently high frequency, the thing will act like a choke. No problem with that at all.

So if you are not carrying enough ferrous material to make a significant flux concentration or effective "core" for the induction coil to react to the increased reactance; a permanent magnet of sufficient strength to "distort" (variously add to and detract from the alternating magnetic field of the coil) should be an aid to this detection process!

Hall effect detection from the transient currents in the conducting parts of the frame would be orders of magnitude less effective; I would suspect.

No one wants to haul around a large, heavy chunk of iron under their bike? How strong a magnetic field would it take (rare earth/ ceramic) to have the same effect on the coil flux density as an automobile body/frame if the biker is near the loop? Not sure it would be 100% in triggering the light but a strong magnet should increase the chances.

A magnet won't necessarily help.

The inductive coil is sensing mass. Not magnetism. Though it would sense the ferrous mass of the magnet. But a block of plain steel or iron would work better.

The problem is, it can only sense the mass of metals primarily. There are 2012 cars on the market which will not trip many inductive coil sensors unless you sit the engine or transaxle over the loop pad.

20+ years ago, Space & Missile Command was sensing the MIRV warheads coming out of an ICBM when it "MIRVs Out". They used a long range version of inductive coil sensing to read the mass of the warheads, so they could tell the dummies because they had less mass. Then the Soviets (and the USA) started adding mass to the dummies, and SMC had to work a little harder, but X-rays and really long wave radar solved that problem too, as they learned how to differentiate between iron mass and plutonium mass. It got to the point they could shoot at the real ones as they were re-entering the atmosphere. Not a desirable solution, but as good as it would get.

Fortunately we got past that stage, though there are a couple madmen left in the world with nukes (or will have them soon) who have no compunction against throwing a nuke at their neighbors, or even at the USA. We can blow them up if we see them launch, but if we don't see them launch, we won't see them until apogee, and then it gets really dicey.

Anyway, your traffic signal trigger pickup came out of that cold war tech.

Well, its sensing "mass" only in the sense that increased ferrous mass will add to the magnetic flux concentration and increased flux density in the coil thereby increasing its inductance and inductive reactance. Its not a mass spectrometer after all, LOL.

I'm not at all questioning the physics, but only the parameters of the engineering circuitry which will determine whether the addition of flux components from an outside magnet will be able to instigate variation in emf (and resultant current in the coil/ ELI) sufficiently to trigger the light?

Sounds like Privateer thinks that is not very likely at all. May be that is so.

Guess no one on this forum has any "direct lab tests" in the form of personal experience through purchase and trial of one of the commercially available accessory magnets?....anyone? ....anyone?.....Buehler?

I happened across this thread in search of headlight info... and I didn't read the entire thread word for word, but a quick browse and I did not see anyone mention the use of the starter button. pressing the starter button while passing over the sensor will trigger the light. this works on about 95% of the lights I encounter in the state of Ca.

I read that your best bet for triggering Hall-effect traffic light sensors is to stop the bike directly over the pavement cut so the wire loop has the best chance of sensing the bike. Then if that doesn't work, run it, legally or not. Most cops will understand, even if it's not legal. Some of them ride bikes and many ride at work or know another cop who does.