Will we ever do away with Hydraulic Braking Systems?

General Discussion
181

Regarding WheresRick’s comment about blowing a hydraulic brake line, something similar happened with me some years ago on a motorcycle trip to Sturgis, SD.
A fully loaded Harley approaching a sharp bend at the bottom of a steep hill and while riding the brakes to hold the speed down the pedal flopped on me.

That left me with nothing but the front brake (near useless in this situation with over half a ton GW) and a runaway logging truck ramp facing me. I was banging gears and praying as I opted for the turn rather than the runaway ramp. It took every bit of gumption I had to wrestle that Harley through a turn designed for speeds about 30 MPH slower than what I was actually doing.
Finally getting it stopped I found the brake bleeder nipple on the rear caliper had blown out and took the threads with it.

My antique Harleys have front and rear drums and personally, I like them better than discs. Simple, functional, and in my opinion will slow the bike down better than discs.

182
the same mountainbike Long Lost Magliozzi Brother

12:21AM edited 12:21AM

Interesting. I was unaware that railroad cars had individual traction motors in each car or at each axle.
Does this system supplement the air brakes?

Only the locomotives have traction motors on all the axles, like using a Jake Brake, it supplements the air brakes. Also, railroad engineers are very good at shutting off the power in time to barely need brakes except in unforeseen emergencies. There may be some tracks where long downgrades make dynamic braking necessary to keep the speed at a safe level. This may be why we see so many trains with locomotives on both ends of the train on that BNSF track that parallels highway 84 going through New Mexico.

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@BLE and Same,good answear-conventional trains arent very tolerant of grades excedding a few percent%,the company used to keep a spare locomotive parked on a side track on a lot of grades around here when the main locomotives would lose traction and not be able to pull the “string” up the hill and a good engineer fears an occurance called a “runaway” a few 100 ton locomotives cant hold several thousand tons back very effectively another interesting thing is,some railroad shops build a thing called a “slug” I believe(which has no diesel engine,but is connected to the other locomotives to furnish enough traction to pull a train when the main engines dont have enough traction to get the job done-but have more then ample generating capacity-Kevin

184

I didn’t say electric brake actuators wouldn’t work. I’m just saying that it takes energy to keep it applied and it is worse than what we have now, in the energy consumption perspective. Even though air brakes use engine output, they only use stored energy and they don’t require additional energy to keep them applied. Electric actuators use a constant supply of kinetic energy. Now that much of a vehicle’s functions are electronically controlled, I can understand the advantage of using electro-hydraulic or electro-pneumatic. The computer can divide retardation between engine and friction to prolong brake pad life. And both forms of electronic braking use stored energy. But if we are to use electric actuators that require a constant supply of electricity, there better be something to gain from that extra energy usage.

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Stupid smart fone double posting. BTW, @Rick, have you ever driven something with air disc brakes? They can bring 50 tons to a halt like a compact car without fading. The mechanics love them as they don’t have to heave the drum out to change the pads.

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Interesting. I never knew that about locomotives having motors at each wheel. I learn something new every day.

187

Eight driven wheels is nothing new:

188

I wonder if you can “Jake Brake” a steam engine. I imagine there is braking when you close the throttle because it will prevent the engine from pumping air. I just wonder if there was a provision for additional engine braking, allowing air into the intake instead of high pressure steam and having a throttle restricting the exhaust outflow for example. The heat from compressing air would also keep the cylinder hot so when it’s time to turn the power back on, you don’t risk hydraulic lock from steam condensation in the cylinders.

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Remember in the movies when the steam train HAD to stop and you could see the drive wheels lock up, then start going BACKWARDS as the train stopped?

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I have a toy miniature steam engine and it’s possible to spin the flywheel and pump a bunch or air into the boiler and then the engine will run on that air for a half second or so. Energy recovery braking that doesn’t involve electricity!

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In steam days having helper locomotives to help trains get up grades was very common. With diesels it is less common, though still done in rare cases. Trains usually just slow down to make it up grades. For a steam locomotive that doesn’t work. Slowing a steam engine also reduces the power output. With a disel electric locomotive you can keep the diesel engines running at top speed, but the generators and motors can run at lower speeds and still use that power. It’s one of the big advantages of diesels over steam. Some early diesels had unpowered axles, especially passenger locomotives, but these days the diesel engines are so powerful you need a traction motor on every axle.

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The right thing tobdo on hills is to stop the train and manually set the brakes on some cars. This is done with either a brake wheel (in olden days, always) or a ratcheted lever. This not only applies a constant braking force that doesn’t need to be applied by the air brakes or dynamic brakes, it also makes it much easier for the engineer to control slack in the train, which can be very dangerous as a long train covers terrain with varying grades. There is an art to braking. If too much braking is applied couplers can break and the train separate. Not managing slack correctly can also cause this. Anyone who has ever tried one of the computer train simulators will quickly come to appreciate the difficulties an engineer faces that no driver does.

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I don’t know how train engineers maintain their sanity. One can only imagine over a month’s time how many motorists dart in front of them and I’d have to imagine that a train crew would get extremely frustrated over close calls.

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Not just the close calls. During their careers most engineers will hit one or more cars or people (often suicides) on the tracks. Trains don’t stop quickly. Engineers have to be ready to face the possibility their train will kill someone every time they check in for work. Still, railway people almost all love their jobs. If they make it through the early days, they’re likely to retire with a railroad pension.

195

Y’know, having thought about it I do seem to recall reading long ago that the diesel engines were simply to run the generators and the wheels were powered by an electric motor at each. It’s been so long that I’d forgotten. Old age, I guess. I used to know stuff.

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Locomotives use a generator-motor link to the driving wheels mostly because it’s the most practical infinitely variable transmission that can handle the horsepower of a locomotive. Specifically, it’s a differentially compounded DC generator that drives series wound DC traction motors.
Series wound DC motors automatically weaken the field as the armature draws less current, which means the output RPM automatically rises with a reduction of load, the motor is constantly “shifting gears” as the speed increases.
A differentially compounded generator automatically reduces the output voltage when more current is drawn and is inherently current limiting, hence their use in DC welders.
This combination effectively gives a locomotive a stepless infinitely variable automatic transmission that is reversible, it can go and pull just as well backwards as forward.

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@‌ WheresRick

“I remember people hanging on to their carburetor cars, screaming about the demons of fuel injection.”

Do you remember the problems people had with electronic fuel injectors? It took them a long time to get them right. Remember they offered it in 1957, (note electronic not mechanical) it had cold start problems, electronic failures, etc. EFI really only took off when exhaust emission were regulated and the addition of many sensors (which in themselves took a while to prefect) to bring us to the reliable systems we have today. Now if a car that isn’t running right, or not starting that is a problem, but not as big of a problem as it not stopping. I have told my son over and over, a car that won’t run isn’t a problem a car that can’t stop is.

Now on an electric car, sure dynamic braking and regenerative braking will slow down and stop a car, but they already have the electric motors where as an ICE car doesn’t.

" maintenance intensive problematic hydraulic systems"

Maintenance intensive? What change pads every two or three years, and change out brake fluid every two or three years, in a shop that can do that in a matter of two or three hours. I would hardly call that maintenance intensive. Do you call replacing tires maintenance intensive too?

Now if I had to design a electronic braking system I’d use disks, they have many advantages over drums. I would have a fail-safe system IE emergence brake that could engage the brakes if the car lost electrical power a mechanical system that would probably engage the back brakes only. So that part wouldn’t change much, a cable and a handle, just like we have with hydraulic brakes and an linear servo actuator to an arm to engage the brakes. But what have you really gained? Nothing really, yes you don’t have to dispose of brake fluid nor do you have to change it, but you’re still replacing pads (or shoes if you insist) you’re burning more fuel, you’ve added more sensors, you’re going to have to add feed back to the brake pedal so more power. That probably means a bigger alternator, so more cost. The what to do if one servo fails, turn one off on the other side? With the way I’d set them up that wheel wouldn’t brake at all, but remember if they are setup the way you stated you’d lock one wheel up, not fun.

Notice I didn’t say it couldn’t be done but there are problems and no real gains. You’d have much more expanse have a much more complex system.

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I can only speak from my own experience, but I have not found hydraulic brake systems to be maintenance intensive. Quite the opposite.

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@MarkM

"Slowing a steam engine also reduces the power output. "

Not quite true, a steam engine produces maximum torque at almost 0 rpm. Decreasing the amount of steam or steam pressure will reduce output, but going up a hill doesn’t decrease the amount of steam. But going up hill does increase the rolling resistance, at some point you can’t overcome the rolling resistance and the train stops (due to wheel slippage), even though it’s putting out it’s maximum torque and power. It make it simple the wheel is spinning but we aren’t going anywhere. There is a limited amount of power you can transfer to the track through the driver at a given weight. So it’s more of a function of the number of traction motors the diesel has vs the number of drivers on the steam engine and the amount of weight on its drivers. You’re putting more power down because you’re spreading out the load over more axles.

So the real reason you can go up a steep grade without a helper is because you have a traction motor on every axle and thus you can put more power down, not that you’re losing steam power because the rpms are slowing down.

I hope I was clear

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I suppose the old steam locomotives effectivly had one steam motor on each side?with the output ganged or divided among the drive wheels-Kevin