Is it really needed?

I guess if you trap the balls on flippers alot

I plan, someday, doing the fans. I have the heat sinks, ones from tower hobbies that are intended for rc car motors and fit around coils perfectly. While they do improve, there is still a change from the start until deep in a marathon game.

It's much better, but I want complete consistency throughout, So I will be doing the fan mod when I bet around to itm

I tried the RC car heat sinks. Unfortunately, flipper coils exert a lot of vibration and the alum shorted one of the coil windings. I ended up going to pinball life's stronger Lotr coils. Much better.

I wrapped mine up with electrical tape before hand, and secured them with plastic ties. They have held strong for two years without movement of issue.

I've used a single 80mm fan tie strapped to the wires blowing air into the flipper coils. I used this on batman forever where the flippers tended to get worse the longer the game was played. This solved the problems utterly.

I did the same with a TSPP i had on location a few years ago. It really did help keep the flippers cool when operated for long periods of time.

If you find the need for flipper coil cooling, heat sinks are one way to go.
However, a fan is a far better solution.

I'm on mobile right now but if you look at my post history in the lotr member thread I have some pictures of how I mounted my fans. Lotr have an aux power port in the front of the cab you can get 12v from and use computer fans. They are silent fans so you can't hear them at all. I've had quite a few marathon games on them and never had a problem since installing the fans. I've done it on both lotr and tspp.

Who will be the first to liquid cool them?

Phase change?

OP, you should have some thermodynamics experience, at least some formal training (Wikipedia does not count) and document test data before determining the next steps.

After 15-20 minutes the flippers on my standard coil LOTR SE would get noticeably weaker. Tried heat sinks (held on with thermal tape and a zip tie), which added about 10 minutes of full power time. Finally in addition added a pair of large fans left over from a computer case that did not need them, mounted on some custom brackets, and that really did the trick: Full power for hours of play.

I ran some wires to the backbox, and since I have a ColorDMD, I was able to tie into the aux power pass-thru on that board, but you can just run back to the accessory connector in the cabinet front (like the colorDMD already does).

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I didn't realize this was actually a thing. What's the reason for the loss of power? Is it the coil heating up, expanding, and squeezing the sleeve/plunger harder?

The coil is heating up. LOTR is apparently way worse than any other game. I had a TSPP and never had problems, but I've heard it a million times about LOTR.

Yes multiple people have used fans to solve the issue, it works great. It also solves the problem people complain about by using the more powerful coils, which is that they are extremely powerful at first and then get down to a reasonable level after they warm up. These are the exact same, not too powerful and not too weak, all the time. If you look at the lotr valinor video on Youtube they mention in the comments about using fans on that game as well. Here's how I attached mine using zip ties. I'd recommend something like that vs permanently screwing something into the playfield. This way if I want to remove them it's a matter of snipping two ties. This is TSPP but as I said earlier I did the same on both TSPP and LOTR.

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Sterns 5020 coils are strong but small and can hear up even with eos working correctly. I've experienced it with lotr, batman forever, acdc (my first one not this one), and 24. The games that use 5032 coils seem better but those are weaker coils.

It's because there is constant flipping. If you are up top going into pops, your flipping around the lane changers, any ramp shot or inlane return, you are flipping for the KEEP letters, and that's up top of already epic flipper action with a lot of multiball play.

I would love to see a mod which will drastically reduce, the carbon dust.

It you look at my last picture the aux power connector is the one I'm holding with black, red, and gray wires. I can't remember off the top of my head which two pins are for 12v. Do you have a multimeter? If so it'll be easy to figure out. The fans won't have the same type connector so you'll need to come up with a way to connect the power wires for the fan to the aux power. I happened to have an extra aux connector so I cut that and spliced the wires into it. I would recommend doing the same so that you are not permanently altering your machine in any way.

The inrush current is what's making them heat up, but what's the scientific explanation for why they lose power? Heating wouldn't effect the coil operation electrically until it failed, unless I'm missing something.

Is it the expansion from heating that causes more friction?

I believe the coils heating up softens the sleeves, in turn causing increased friction.

Magnetic flux density (B) is determined by B=NI, where N= number of turns, I = current. N will not change as the coil heats up. However, the resistance of the coil will go up with temperature. I=V/R where V= Volts, R = resistance of the coil. Volts will not change, so as R goes up, I, the current, goes down. Then B goes down and the flippers lose strength.

Don C.

Going from room temp (around 22C) to boiling water (100C) would only increase the resistance by about 1 ohm on a 5020, I didn't realize it would have that much effect on the power. TIL...

Seems like a single DC blower might be enough to blow across both coils. Should be quiet enough depending which one is used.

One ohm sounds insignificant, but let’s see...

I don’t have the exact resistance of the 090-5025-00 coil (which is 24-1570, or gauge 24 wire 1570 turns). But flipper coils are generally about 3 to 4 Ohms.

If the coil resistance is 3.6 ohms at 20 degrees C, what is its resistance at t2= 80 degrees? Temperature coefficient of copper is .00393 per degree C.

R2 = R [1 + a(t2 - t1)]
R2 = 3.60 [1 + 0.00393(80 - 20)]
R2 = 3.6 X 1.236 = 4.45 ohms, or a .85 Ohm increase in resistance.

So, about a 1 Ohm increase.

But .85 ohm added on to 3.6 Ohms is about 24% more resistance, or 24% less current, or 24% less magnetic flux available to create the tractive force that moves the coil core.

If a 24% loss of flux sounds bad, it gets a bit worse! B is not the force of the magnetic field, just the flux. For the force we need another equation. In the formula for the force, the B term is a squared term. So any loss in flux is a much bigger loss in force.

Stolen from Wikipedia:

Force between two nearby magnetized surfaces of area A
The mechanical force (F) between two nearby magnetized surfaces can be calculated with the following equation. The equation is valid only for cases in which the effect of fringing is negligible and the volume of the air gap is much smaller than that of the magnetized material:

F = B^2 A/2 μ0 (B squared times the Area divided by 2 times mu zero)

where:
A is the area of each surface
μ0 is the permeability of space (very close to that of air)
B is the flux density

Area and mu zero stay the same hot or cold. But B has dropped 24%. What is the effect of the 24% reduction in flux on the Force?
Let’s use some round numbers to illustrate. Let’s say you have a cold coil current of 10 amps x 1000 turns, or B = 10,000 Ampere-turns. So, B squared is 100,000,000.

Hot coil current is 10 Amps less 24% or about 7.6 Amps. B will be 7.6 Amps times 1000 turns = 7,600 Ampere turns. B squared is 57,760,000.

Going from cold to hot is going from 100,000,000 A-t to 57,760,000 A-t or 42% less force, or only 58% of your cold flipper strength.
So a 60 degree C temperature rise, creating a .85 Ohm change in resistance can create a 42% reduction in force on the coil core. This is the very large drop off that people notice.

I just wanted people to know that it’s not friction, but the resistance change that lowers the force.

Don C.

Don, thank you very much for spending the time to type this out and explain it. It's exactly the kind of explanation I was looking for!

No problem, I spent many years designing the big electromagnets you see in scrap yards and steel mills. Maybe that explains my 'attraction' to pinball.

Don C.

Yes ty from me too! I was just going to type the same thing out myself but I was eating a sandwich. Btw, I did stay at a Holiday Inn Express last night!

I used a 120mm pc fan ties strapped to the wires pointing at both coils and it did its job well

DOES ANYONE HAVE A SIMPLER SOLUTION TO THIS PROBLEM? sorry for the caps. seems like adding a fan is a bandaid

Adding a fan is the simplest way to solve the problem.

are these 12 volt pc fans all pretty much the same? i am going to order a couple

No, they come in many different varieties, with different noise levels and moving different CFMs of air.

Computer fans come with 2, 3, or 4 wires but you only use two to run the fan. The others are for sensors to detect the speed and allow it to be controlled via software.
I think a 120 mm case fan would work well.

perfect. thanks man!

My LOTR doesn't heat up...
Why do coils get warm? If the stroke-time is too long the flippers will heat up faster.

Try adjusting the EOS (the software actually does more than pulse the stroke when a ball is falling on it)
And try adjusting the software. I believe there are software revisions which allow for 3 extra adjustments for the flippers. At least mine does. Adjustments like minimum stroke time and stroke-time after EOS has been made. And one extra.

There might also be an adjustment for coil power. Not sure if this is also present for LOTR.

Again: my LOTR doesn't have heating problems and all shots can be made easily (including the ring from the left flipper in a long lasting game). So it must be possible without extra cooling.

when I got the game there were no eos switches in it. I rebuilt the flippers and the eos switched from the kit were installed and adjusted properly.

ADDED FANS. NO LUCK. SAME ISSUE THOUGH NOW I am thinking it's more intermittent than heat related. I will check for loose connections in the wiring and on the pcb. a few have mentioned faulty transistors. also of not the flippers assy's both had the eos switched removed when I got it. i'm wondering if this has damaged the electronics

Maybe you should start a tech thread where you can clearly describe the problem, list the game, etc

thats a good idea now. i wanted to read up on it before asking so I found this thread first. i will take your advice though at this point because I just tried a whole bunch of stuff

Can anyone explain what the flaw is in the Stern system that causes this? It can't be the coils (I have run them and full Stern mechs off Capcom board set for **hours** without any heat, and retaining the fabled Capcom "feel" still there). Not having an electronics background, I don't appreciate the difference between how Capcom did it so well and Stern so poorly. Must be an explanation in there though?

Necro!
anyone know the answer to Vege's question? why do LotR (and other) coils fade so much when others don't? someone have a heat sink solution? the fans are well known.
thx

I do know the answer to this and it's related to the way the flippers in Stern machines are engineered in comparison to those used most other manufacturers.

Stern uses a standard coil for the flippers which means every time the flipper is energized full power is applied to the coil; obviously you cant apply full power to a coil all the time as it will either melt, blow a fuse, or sometimes both. What Stern does is implement a computer controlled Pulse width Modulation (PWM) scheme so that full power is only applied to the coil for a few milliseconds when the coil first fires, and then power to the coil is pulsed often enough to keep it raised as long as the flipper is pressed; this works well and is low cost alternative to having a dual wound flipper coils and drivers like you find in CGC, JJP, and old Bally/Williams games to name a few.

Like everything in life there is a tradeoff to that lowered cost, and the tradeoff comes in the form of efficiency. Since a single wound coil can only apply full power to the coil every time its fired, it can never be as efficient as a dual coil that contains separate windings for both flipper power and hold functions allowing the low power hold coil to be energized indefinitely with minimal heat buildup. Since LOTR games often last for long periods of time, the flipper coils which are constantly in use have very little time at rest to shed this heat buildup which results in increased coil resistance and weaker coils.

A simple analogy would be to think of if as if you were doing low weight curls; consider the amount of force needed to raise the weight (full power coil) vs holding it once you have it up (holding coil). In the PWM world you never really hold it up but instead you start to let it drop a little it and then pull it back up repeatedly; now think of the energy it would take to hold the weight under both of these conditions and how long you can sustain holding that weight without getting tired.

The only solution is to engineer a means of keeping the coils for getting too hot and the low cost solution is a simple fan. I'm not sure a passive heatsink would help much in this case as the coil itself is already made of solid copper and it just lacks sufficient airflow to remove the heat.