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# Water Cooled Disk Brakes for Big Rigs3

## Water Cooled Disk Brakes for Big Rigs

(OP)
It's an obvious idea. Coming down off the Ridge Route (AKA The Grapevine) portion of I-5, on the north end's over 3000 foot descent I've seen trucks with brakes smoking or actually on fire. I've asked myself why don't they use disk brakes? Also, if you've seen European truck tractor races, you've seen the steam from the water cooling of the brakes. As an emergency expedient, water would save a truck in trouble. Why not?

### RE: Water Cooled Disk Brakes for Big Rigs

Presumably a matter of cost.
Actually, there are two questions there -
1) aux cooling for existing brakes, possibly by total loss water spray, and
2) what about disk brakes, which are easier to cool?

Seems like you could do a total loss spray on the outside of the drums, and cool them pretty effectively. And/or you could add some forced ventilation to the existing drums (electric blower, thermally activated?)
I wonder if that (either of them, actually) could be a saleable aftermarket item?

Jay Maechtlen
http://www.laserpubs.com/techcomm

### RE: Water Cooled Disk Brakes for Big Rigs

(OP)
Yes, cost is a factor. And, if disks allowed a truck to descend a grade at 5mph more speed, maybe we wouldn't want that. but, the brake emergency problem is another matter. If a guy makes a mistake of coming down a particularly long grade at just a little too high a speed he can lose braking and die. It happens too often. An emergency stash of water could get him out of trouble. In fact, just having heat sensors at each brake is something that ought to be law.

### RE: Water Cooled Disk Brakes for Big Rigs

Sure, and are you willing to pay double for all your vegetables? And that's assuming that a retrofit is even possible on all existing hardware. If every outdated trailer and trailer in the US and Mexico were replaced?

The bottom line is always the bottom line, and almost no one wants to pay THAT price, and they're willing to gamble. We developed a safety system for preventing a large portion of helicopter aerial collisions, and even with a relatively low cost, there was great reluctance, because outfitting the entire fleet would have cost ~$250 million, and that buys a lot of bullets and prevents losing bullet carrying capability. TTFN FAQ731-376: Eng-Tips.com Forum Policies Need help writing a question or understanding a reply? forum1529: Translation Assistance for Engineers ### RE: Water Cooled Disk Brakes for Big Rigs (OP) IRstuff, I don't know how much a big rig tractor and trailer cost, but I doubt that changing to disk brakes or a water emergency braking system will double the cost nor double the cost of the driver's compensation nor double the cost of growing, packing, stocking and selling the veggies. Hmm, did disk brakes double the cost of cars? I think it will add something to the cost and save some lives. How much are the lives worth? I'm just asking what are reasons not to do any of this and I expected to hear that costs are a reason. Is there any other, a technical downside that you can think of? ### RE: Water Cooled Disk Brakes for Big Rigs (OP) I should have researched this question before posting it. Here is a paper by Bendix. It is interesting at least for what it says about previous disk systems even considering that Bendix has a vested interest. http://www.foundationbrakes.com/media/documents/ai... ### RE: Water Cooled Disk Brakes for Big Rigs Maintenance costs and downtime. Disc pads do not live as long as linings. No matter how much performance you build in it does not increase safety if the operator just uses the extra performance and leaves the same estimated margin. It saves time, but does not increase safety. A total loss water system would require a lot of water at the cost of payload which means many operators would not use it when needed most. Regards Pat See FAQ731-376: Eng-Tips.com Forum Policies for tips on use of eng-tips by professional engineers & http://eng-tips.com/market.cfm for site rules ### RE: Water Cooled Disk Brakes for Big Rigs Logging trucks do have water-cooled brakes. Here's one with the steam going downhill: Here's the water spout: Here's the 400 gallons water tank: for more info: Link ### RE: Water Cooled Disk Brakes for Big Rigs (OP) Pat, good points. There are speed limits that are aggressively enforced on that dangerous stretch of I-5. An extra speed margin would result in more margin of safety. But in general what you say is true. Drivers tend to find out what the brakes will take and then use the margin, leaving none. The idea of a water spray would not be for general use, but a desperation measure to slow a truck when it has lost brakes. Presumably, merely cooling the brakes enough restores function sufficient to slow the truck to a safe speed or stop it, and if the truck then descends within the recommended speed there is no problem. How much water would be required is a question, but I bet it's not a lot for a one time event IF the driver uses it as soon as he realizes the brakes are in trouble (assuming the brakes are just above operational temp). That's where sensors come in. The supply could be replenished at the next stop. ### RE: Water Cooled Disk Brakes for Big Rigs The reason for the cost increase is the extra overhead, maintenance/support costs. Since the original equipment, particularly for older trailers, is already depreciated, new equipment means new depreciation, in addition to the lost time for retrofitting. That all costs money. TTFN FAQ731-376: Eng-Tips.com Forum Policies Need help writing a question or understanding a reply? forum1529: Translation Assistance for Engineers ### RE: Water Cooled Disk Brakes for Big Rigs (OP) IRstuff, I think new mandates for braking performance from the NHTSA are going to force upgrading on existing truck and trailers, probably cheapest with improved drums. For new production, the NHTSA estimates less than$1500 to go disk all around on a tractor. There is pressure to get US and Canadian trucks in line with Europe which looks to be ahead on this. What additional maintenance costs will be born uniformly. I guess my question about disks is answered with it's gradually coming.

http://fleetowner.com/regulations/truck-stops-here...

JackAction, thanks for the photos. Logging trucks are special equipment on especially steep roads and I can see that they would be more likely to need extreme measures. For I-5 the argument would be is there enough of a need, but at least I see that it is being done on some trucks.

### RE: Water Cooled Disk Brakes for Big Rigs

I expect that pad life is related to pad area - and lots of other factors, probably.
But I don't remember front drum brakes going as far as disks go now- I usually get 50-70k miles from front pads.
What did classic drums get? 20-40k miles?

Disk brakes can dissipate more heat than drums, but generally need some speed to pump air through them.
I took our Aerostar up a steep dirt road once - that was fine.
Coming back down, low gear wasn't low enough to control speed, the road was too steep and safe speed was maybe 15MPH.
The disks weren't getting any airflow at 5-15mph, and overheated.

That's why I mentioned forced ventilation!

Jay Maechtlen
http://www.laserpubs.com/techcomm

### RE: Water Cooled Disk Brakes for Big Rigs

I know what modern disk pads get. The point is what did classic disk pads get vs classic drum brake linings. In my experience when a similar car was offered with optional disk brakes, the disk brake option required more regular replacement. Maybe it was placebo or maybe small sample size or different demographics of the drivers

I agree the vents in the rotors rely on wheel speed to pump air so high speed light weight suits them better than low speed heavy weight.

Regards
Pat
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### RE: Water Cooled Disk Brakes for Big Rigs

(OP)
Jay, you are right that the biggest advantage of disk brakes, much better ventilation, is less effective at very slow speeds. So, you have to allow for that as you compensate for the grade. Otherwise, you cut your speed in half for a grade twice as steep. On unpaved roads it's harder to judge the grade. Jack mentioned 32%. That's horrendous.

### RE: Water Cooled Disk Brakes for Big Rigs

You are ignoring that nearly every diesel truck today is equipped with an engine brake that can absorb more power than it can put out a full "throttle". So as long as the trucker starts down the grade at a proper speed and in the correct gear, the engine can keep the speed under control without using the service brakes at all. That logging truck is obviously an exception.

Regarding maintenance costs, I have always found disk brakes much easier to work on than drums. Some designs like my motorcycle, the pads can be removed and changed by pulling one pin out, no need to remove the wheel. I've never seen a drum that can be serviced like that. Time is money in trucking so this could potentially save money.

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The Help for this program was created in Windows Help format, which depends on a feature that isn't included in this version of Windows.

### RE: Water Cooled Disk Brakes for Big Rigs

(OP)
dgallup, I think you are only partly correct. First, the engine may not be able to control the truck's speed if the grade is TOO steep. The logging trucks are an example. Also, if the trailers brakes are not holding, engine braking could cause jackknifing. Second, the power of engine braking depends numerically on the gear ratio. So, at 60mph engine braking on a 6% grade should be hopelessly insufficient because of the gear ratio. The trucker has to downshift and he may not be able to get the gear he needs. Truckers have died trying everything to slow down. Runnaway trucks that have lost brakes may be doing 70mph or more and have no recourse except the escape turnouts that put the truck into a gravel trap. I've seen films of tests of traps. It's a hell of a ride, but a life saver. There are a couple of them on the Grapevine, one on the left side which I always thought was strange, but I guess if you can't hold the 35-45mph of the trucks in the right lane, you have to go left.

However, engine braking contributes. It could be all you need depending on grade, speed and gear.
Are you referring to "jake braking"? Is that is the most effective of several techniques? The speed limit for trucks on the grade is 35mph and at that speed, jake braking could probably hold the truck. But, I've seen trucks doing more than that.

http://www.crashforensics.com/tejonpass.cfm

### RE: Water Cooled Disk Brakes for Big Rigs

"First, the engine may not be able to control the truck's speed if the grade is TOO steep. The logging trucks are an example. Also, if the trailers brakes are not holding, engine braking could cause jackknifing. "

That's not the case for I-5, though, since its grading was designed for even older trucks. And that's the reason why there's a brake check area prior to the downgrade. Invariably, the reason trucks have absymally poor maintenance, which is why changing the braking mechanism will most likely not help; the truckers will defer maintenance to the point of failure.

TTFN
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### RE: Water Cooled Disk Brakes for Big Rigs

(OP)
IRstuff, that's true. The trucks I've seen with smoking brakes weren't going all that fast. It points possibly to brake problems due to maintenance.

### RE: Water Cooled Disk Brakes for Big Rigs

Heat input is proportional to speed squared.

Cooling - treating the disk vanes as a fan - is proportional to speed, more or less.

So if the cooling is sized correctly for high speed, high energy stops then you should be ahead of the game at slow speeds.

At any rate, considering that there is a substantial population of trucks with the tractor's front brakes disconnected because drivers still think that they get better braking performance that way I don't think there is much of a market for disks.

### RE: Water Cooled Disk Brakes for Big Rigs

Jake Brake is one trademarked name for an engine retarder designed by the Jacobs Engineering company. Nearly every engine manufacture has more or less the same thing. These brakes can absorb considerably more power than the engine puts out so if the engine can haul it up the hill the engine can slow it going down the hill providing the driver starts the descent slow enough and in the correct gear. I don't think jack knifing would be any concern unless on a low traction surface.

If the driver lets the speed build up too much there is nothing but the escape road that is going to save him.

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The Help for this program was created in Windows Help format, which depends on a feature that isn't included in this version of Windows.

### RE: Water Cooled Disk Brakes for Big Rigs

Over the road truckers get paid to haul payload, not water so any extra weight that displaces revenue producing payload is a deal killer. Off road truckers like loggers don't have to worry about gross weight, so the added weight of water, tanks, etc., is justified in increased productivity. Same would hold true with race trucks.

In my experience with truck brakes years ago (haven't messed with them since I was on a SAE Brake Div, retarder sub-committee about 20 years ago, so my info may be old) was that disc brakes would save the rig, but destroy themselves. In other words, in an abusive braking situation, you could get safey down the hill, but the discs would be completely gone, requiring replacement at the bottom. At least the driver would be alive to perform the replacement, but it would mess up his schedule.

Drum brakes, on the other hand just get hot and expand away from the ability of the pads to maintain contact with them, thereby releasing the rig to crash after a very fast ride, but after the crash, when the drums cooled off, the brakes on the (now) wrecked vehicle would work just fine.

Any driver who is smoking his brakes on the Grapevine is (A) smoking something himself, or (B) from back east somewhere. I did get a motor home's brakes a little too hot on the Grapevine once and was in for a ride I'll never forget. The worst part was that my family was on board.

There are all kinds of retarders on the market to help with productivity on downhill runs ranging from engine brakes already mentined (although I believe someone has been reading too much sales literature based on testing we did during my stint on the committee) but all of them add some weight, and weight is king in OTR trucking. The lightest of course is the engine brake.

I once demonstrated an electromagnetic retarder on an 18 wheeler (trailer axle mounted) that was 4 times more powerful than the engine brakes of the time and when the operator applied the first step of the four step retarder actuator and snidely turned and sneered at me 'see it is about the same as the engine brake' to which I replied, "yes, but you have 3 more positions, all the while grabbing the retarder control handle and moving it through the second, third to the fourth position. If only I'd had a camera to capture the look on his face as he commenced to grabbing gears to match his rapidly declining speed.

rmw

### RE: Water Cooled Disk Brakes for Big Rigs

(OP)
rmw, Very interesting information. I never heard of an electromagnetic retarder.
Some truckers do push the margin. You see some outpacing others by 10 or 15mph. However, how fast they can safely go depends on their load. Although I've never seen a runaway truck, I always can smell their brakes on the Grapevine grade and usually there is at least one with brakes smoking by the time they reach the bottom.
I wouldn't assume a trucker in trouble must necessarily be on something or dumb. All that has to happen is he gets a wrong weight for his load or he makes an insufficient compensation for it or he underestimates the grade. Your own experience with your RV shows it's easy to make a mistake.
The water idea was for a one-time emergency use, not continuous. How much do you think would be needed to save overheated brakes and slow the rig to a safe speed or stop it? How about for a motor home?

In Malibu there is a truck killing road called Kanan-Dume (Doom) Road. Coming out of the Santa Monica Mountains down to PCH is a long downgrade that I think truckers tend to underestimate. They are banned from being on the road in the first place, but they sometimes take it anyway. Every few years there is another, usually fatal, incident.

### RE: Water Cooled Disk Brakes for Big Rigs

I do I-5 pretty regularly, about 5 times a year, but I've rarely seen smoking brakes, but I could just be concentrating on getting to where I'm going. It could also be that the holiday truck traffic is different. But, no doubt trucks are going faster than they're supposed to be on the downgrades, which presumably they compensate for by driving SLOOOOOWLY on the flats.

"The water idea was for a one-time emergency use, not continuous." but the water has to be carried continuously.

TTFN
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### RE: Water Cooled Disk Brakes for Big Rigs

140Airpower,
You've probably heard of/seen the retarders but haven't realized it-- they are commonly used as the retarder on eddy current chassis dynos. Frenelsa and Telma are the two brands that come to mind, though there are others.

### RE: Water Cooled Disk Brakes for Big Rigs

(OP)
IRstuff, yes it would be a constant weight penalty, but the amount would only be for a one-time use, enough to cool the brakes so that effectiveness is restored to slow a truck from say 50 or 60mph to about 30mph by normal braking action. A system would have to be mandated, not voluntary and I suppose the industry would fight it. It's a speculative idea.
Disk brakes alone, if universal, would allow a higher safe speed. Truckers should welcome that. But, adopting higher speeds on grades would use up the safety margin that disks provide as pointed out before. In any case it appears disks will eventually become the standard here as they are in Europe.

The CHP says the escape ramps get used 30-35 times a year. Truck traffic is up to 22,000 per day. I think most truckers in trouble simply ride it out. They can probably negotiate the car traffic up to about 70-75mph. I've seen only a few flipped over trucks off the shoulder at the bottom of the grade and those were not necessarily runaways.

crersu75, I looked up he retarders, thanks.

### RE: Water Cooled Disk Brakes for Big Rigs

Bottom line: water cooling brakes is solving a symptom of the problem, not the problem. Except as noted later, if a trucker is smoking his brakes, he is going too fast for the conditons, part of which is determined by the amount of retardation he/she has on board in the form of compression brakes, exhaust brakes, electromagnetic, hydraulic, etc., etc. I've seen drivers with engine brakes (compression brakes) smoke their brakes too when they overran the ability of the engine brakes to hold them back. Cold brakes will stop anything. Keeping the brakes from overheating is a requirement of professional driving (and staying alive.)

Now things happen, like missing a gear on a downhill where one would have to use more brakes than normal to bring the rig back under control. But the average driver who is smoking those brakes you are seeing is just a dunce and needs to be doing something else. Sorry - it is a hard saying, but look at the 99% of drivers that arean't smoking brakes on the same hill.

The exception I mentioned earlier is where the smoke isn't the brakes, but grease from a leaking wheel seal burning off when the brakes get hot. The brakes overall may be hot, but not too hot to control the vehicle, but hot enough to torch off any greast built up by grease leaking through a seal onto a brake drum.

Now Crerus, Frenelsa & Telma.... That takes me back several lifetimes. 140 AP, google Klam, Zelu, and the word "ralentizadores" if you want to read any more about electromagnetics.

rmw

### RE: Water Cooled Disk Brakes for Big Rigs

(OP)
rmw, you said "the average driver who is smoking those brakes you are seeing is just a dunce and needs to be doing something else. Sorry - it is a hard saying, but look at the 99% of drivers that arean't smoking brakes on the same hill".

I certainly agree that it is the driver's professional obligation to not overrun his brakes, but mistakes happen to the best and IIRC much more than 1% of the trucks on the grade had smoking brakes and I could always smell somebody's brakes. However, most of my experience was in the '90s when I did about 120 trips to the Bay Area. I take that route only a few times a year nowadays and only to the Frazier Pk turnoff. The difference in that is that I'm not in a lane to watch the fastest trucks nor do I go all the way down.

Now it occurs to me that in my memory most smoking brakes I've seen were on the trailers, not the tractor and I think that makes a difference. Anyway, I did run across a quote by a trucker who also noted he always sees someones brakes smoking. Like I said, some guys run 10-15mph faster than the other trucks and that may or may not be ok.

### RE: Water Cooled Disk Brakes for Big Rigs

(OP)
About truckers: Although I think more than 1% of trucks on the Grapevine get to the bottom with overheated brakes, the vast majority, probably over 95%, do not. Like I said, overheating your brakes is not necessarily a sign of incompetence. A safe speed depends on your load and even a smart guy can make a mistake estimating what he can do. Experience is everything. What makes Kanann-Dume Rd so bad is that the grade is 8% and truckers have no experience on that road. A load safe for 35mph on the Grapevine has to be taken down Kanan-Dume at 25mph. If the trucker does 30 he'll likely be in trouble.

### RE: Water Cooled Disk Brakes for Big Rigs

Is there really a problem? I don't know if you're always talking about the same road in all your posts, but you've said earlier:

#### Quote (140Airpower)

The CHP says the escape ramps get used 30-35 times a year. Truck traffic is up to 22,000 per day.

That means that 99,999595 % of the trucks don't have any problems going down that hill. At least nothing too serious. Furthermore, those escape ramps did the job: stop the (very few) runaway trucks. And if we're talking about modifying the brake system of all trucks & trailers across North America, even the ones that don't go on these kinds of roads, the number of decimals needed for this number will become ridiculously high.

In my honest opinion, that should answer the question in your original post:

#### Quote (140Airpower)

Why not?

Otherwise, if we really want to eliminate all possible accidents due to deficient brakes, we could also ask: Why not put a parachute in the back of every trailer in case of emergency, just like the ones used by dragster?

Even then, I'm sure there will still be a parachute that won't open at one time or another when needed.

### RE: Water Cooled Disk Brakes for Big Rigs

Ah, 140AP, you now get to learn another truism about the trucking world. A fairly significant number of trucks (meaning truck/trailer rigs) on the road are owner operators who own their own tractor and lease it to a company who provides the trailer - a company owned trailer.

Guess whose brakes get abused with that combination. There is even a term for it (or at least was 25 years ago when that scene was part of my world) amoung owner operators: "Company jake brake" which meant that they would reach over and pull the trailer brake handle to ensure that they do the lions share of the braking while sparing the use of their own tractor's brakes.

Secondly, company trailers get bounced around and often spend large periods of time out and about before they make it into a terminal where maintenance is performed on them, so encountering a company trailer with brakes in all states of disrepair isn't uncommon at all which means that when they are used, some brakes on the trailer are doing all the work while others less well adjusted are less heavily loaded. That is even true of company trailers behind company tractors.

So, not suprising at all to read that you see more trailer brakes smoking.

rmw

### RE: Water Cooled Disk Brakes for Big Rigs

(OP)
Jack, we've discussed MANY techniques to control the speed of trucks on grades. If there was no problem, no special techniques would be needed. None are needed for cars. If ANY single technique was completely satisfactory there would be no need for any others. Just because 99.99+ percent of trucks don't use the ramps does not at all mean that that percentage have NO problems. The truth is that trucks are and always have been severely underbraked for long grades on today's roads and there is no fail-safe. Otherwise escape roads would not be necessary. It's an area for innovation. If you are not interested, ok.

### RE: Water Cooled Disk Brakes for Big Rigs

(OP)
rmw, I kind of started to have suspicions about that.

### RE: Water Cooled Disk Brakes for Big Rigs

140AP,

Thre is no need for innovation. There is a laundry list of equipment that will aid trucks get downhill or even do all the hold back required. The unfortunate thing as Pat P states above is that truckers are not willing to sacrifice payload - or that is to say that - anything that they perceive would reduce payload (because some of what they do replaces payload but they accept it as normal and I'll name a couple below.)

For now the comment is about the need to innovate or not. The retardation system that will do all the holdback adds about 1500 lbs to the rig's tare weight and the industry won't have it. For the weight of the water that you proposed adding, they can have the finest retarders on the market. Heavier retarders are fairly well accepted in the offroad community where they don't have to worry about state or federal weight laws.

I know first hand of a situation where a trailer axle retarder user was smoothing off of I-8 eastbound out of San Diego on a serious downgrade - 8% which is maximum allowed on the Interstate system - at night at about the automobile speed limit of 70 mph (and knowing him, I bet he was crowding that by a few mph) and due to a total malfunction of the electrical system associated with his 12/24V starting system, when a certain circuit breaker opened up, he lost every bit of his electrical system, lights, engine controls, everything including his electric retarder. Well, the saying is that cold brakes will stop anything and he proved it that night. He stated that he wouldn't have been able to stop like that twice in a row, but he did get it stopped and to the side of the road whereupon the circuit breaker cooled off, remade and his electrics returned. I know about it because he came straight to me and made me figure it out and come up with a fix, which I did. I don't remember all the details now of what we modified, but if I studied a 12/24V starting system for a few minutes I'd remember.

He had a 1693 Cat engine which was adapted from a motor grader engine and there were no engine brakes for that model. He typically ran downhills so fast with that trailer axle retarder that he had to put a sign on the back of his trailer warning other truckers not to attempt to follow him off down grades. The trailer axle manufacturer showed a photo of his trailer rear doors at major truck shows and truckers stopped by with regularity and told stories of trying to follow him and getting into big trouble. His CB handle was 'Sarge' and the stories about that old man were rampant in those days.

He was different in that he was willing to make the payload sacrifice and understood that the increase in productivity (he ran a reefer between Texas and California, chickens westbound, produce eastbound for a grocery chain) plus the peace of mind made up the difference.

And now for the perceptions.

The American trucking industry, and I include Canada and most of Central and South America is in love with the twin screw tractor while Europe figured out decades ago that they couldn't afford all that extra dead weight for no more benefit that it produces. So there is 1500 lb. right there.

Trailers knows as "taughtliners" or "curtain sides" add about 1100 lbs to the weight of a trailer but those who think that faster unloading from the sides is worth that weight penalty gladly pay the price for payload reduction.

Electric starters - I knew of a bulk hauler and tanker outfit in Utah some years back that did the math and realized that air starters (and associated equipment) were lighter than electric starters and associated equipment so their fleet was equipped with air starters. It was interesting one bitter cold winter day I was at their shop to see one of their rigs out against the fence with an electrical cord and an air line strung out to the rig to try to get it started (electricity because the battery was dead and the engine kill switch was electric and needed power to allow the rig to start).

So it is all a matter of perception. They accept what they perceive they need regardless of the weight it adds and reject what they perceive that adds weight if their granddaddy didn't do it that way.

Where the electromagnetics really became popular was in France and Spain in the '60's - '70's when the national governments gave an automatic overweight allowance for the weight of any retarder on board. Why not go for the best which was also the heaviest. I am not so sure those laws still apply since I have been away from it so long.

I don't know where all the work we did on the Retarder Sub Committee for the SAE is today, but there is quite a bit published on the topic if you can find it, but the bottom line conclusion was that until and unless governments got on board and gave an overweight allowance for safety equipment it wasn't going to happen. IN the case of our country as you know, that involves getting 50 states to all get together on something. Hearding cats would be easier.

And then of course, there is the old fashioned way that was done before Clessie Cummins invented what Jacobs Chuck Co would market as the "Jake Brake" and that is to select a gear low enough to ride all the way down the hill without any or precious little use of brakes and just go slow. The Grapevine is a long way to gear low and go slow especially when the "large cars" are streaking by you in the fast lane, but many a trucker has done just that so that he would live to see another day.

I have personally driven many a load of skiiers in large motor coaches down some of the nastiest slopes Colorado has to offer with nothing but gears, but when there are up to 46 people sitting behind you whose lives at stake you find out that it can be done. We didn't go fast, but noone objected and we all lived for me to be able to write this.

rmw

### RE: Water Cooled Disk Brakes for Big Rigs

(OP)
rmw, A wonderful post! There ain't nothing like the observations and wisdom of an old hand who's smart enough to have understood and benefited from his experience.

### RE: Water Cooled Disk Brakes for Big Rigs

(OP)
rmw, We live in a technological society. Innovation is the source and product of technology.
When you find a variety of solutions to a problem it's a sign that probably none of them work well enough or have merits that obviously outweigh their drawbacks. I think THE solution to heavy truck braking on grades has either not been found -or exists but has not been mandated.

Note that friction brakes alone could do the job under all conditions of speed and grade given ENOUGH dissipation. The rate of energy dissipation to hold a constant speed on a grade is only double at 70mph what it is at 35mph. That energy is basically just the gravitational potential energy difference between two altitudes. This energy does not disappear. It has to be dissipated. The rate of dissipation required is proportional to the rate of vertical descent. All the various techniques transfer this energy to the air. Jake-braking pumps air to high temperatures and pressures and releases it without getting any return energy in the expansion. Electromagnetic brakes have a lot of airflow and fins to pump energy to the atmosphere identically to friction brakes. These techniques add dissipation to what the friction brakes provide -no "better" than an additional or better set of friction brakes could do.
Here "better" has to do with space, weight, cost, etc.
For example, at the Telma website they have a video with Jay Leno that shows their $10,000 driveline unit. Coincidentally, its heatsinks look like large brake disks. These heatsinks limit how much braking this unit can provide because, unless the unit can charge a battery pack, the energy from braking has to go to the atmosphere through these heatsinks. Now these heatsinks could be replaced by two cheap same-sized disk brakes and dissipate the same or probably much more energy (because they can operate at a much higher temperature). So, additional and better friction braking is a possible solution that exists but has not been mandated. Of course it may not be the BEST solution and maybe should not be mandated. ### RE: Water Cooled Disk Brakes for Big Rigs So get you a patent, a financial backer (unless you are already really rich) and get out there and convince the marketplace or if you have even more money, the lawmakers. rmw ### RE: Water Cooled Disk Brakes for Big Rigs (OP) rmw, Just throwing ideas out there. That one has already been rejected, as evidenced by current practice. But I do believe truck safety is more limited by vested interests and politics than by technology. The bare economics reminds me of the calculations that gave us the Pinto gas tanks. ### RE: Water Cooled Disk Brakes for Big Rigs Advances in brake pad materials and sensing systems to balance wear coupled with the easier maintenance of disk brakes is making them more prevalent in truck and bus applications. Application specific vehicles like in mining, logging or oil fields already have custom modifications to brakes and other systems to ensure safe and constant operation (gotta make a living...) For 'generic' rigs that find themselves in the occasional unusual situation a more cost effective solution than making special equipment standard could be to provide appropriately spec'd shunt tractors at the top of the pass to take the load to the bottom ### RE: Water Cooled Disk Brakes for Big Rigs - Much of the online bandwidth re: Pinto gas tanks speaks of fire resulting from rear end collision. - However the few sites that I looked at allegedly referencing the infamous internal Ford$$/life memo refer to roll over accidents http://www.calbaptist.edu/dskubik/pinto.htm This tends to be supported as some sites maintain stuff like this - " 1. ...... The memo apparently wasn't used or consulted in Ford's internal decision making. It was attached to a letter written to the National Highway Transportation Safety Bureau (NHTSA) concerning a proposed regulation. Plaintiffs tried to use the memo in support of punitive damages, but the trial judge ruled it inadmissible for that purpose (p. 1021). 2. The horrifically low figure of$200,000 per life was not Ford's value; it was a value used, with qualifications, within NHTSA at the time."

- The recall repairs/upgrades were gas tank mount protection related.
http://www.fordpinto.com/index.php?page=149

The basic gas tank location (under the floor, behind the rear axle) was and is indeed pretty common.
Volvo 240, with some plumbing added by an enthusiast.

### RE: Water Cooled Disk Brakes for Big Rigs

(OP)
Tmoose, I think the "Pinto gas tank" is a symbol that illustrates a point. Distortions of history, deliberate to make a legal case, or inadvertent because the inaccurate versions makes a better story, color our perceptions and memories. But, Ford did indeed consider the vulnerability of the gas tank and did in fact decide not to take measures it knew about that could have improved safety. This happens all the time. It's happening with trucks. The basic economic trade-offs require that at some point a compromise has to be made.

I think we are used to the world we live in. But, we continue to seek improvement. An old movie "They Drive by Night" gives a depiction of the Ridge Route in the old days. We are light years ahead now. But for me the continued need for runaway truck ramps says we are "not there yet".

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