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Author Topic: proper way to decend grade  (Read 22451 times)
gus
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« Reply #75 on: August 28, 2007, 10:14:30 PM »

Tom,

You probably mistyped your third sentence but I think I know what you mean.

Speed makes no difference whether loaded or empty if it is safe

Stopping is the problem. I was talking about braking.

There is more friction in a loaded truck than an empty one.

Air resistance is the same for both.

There were probably more skips on older trucks because most didn't have front wheel brakes at all. I remember being instructed by an old timer to always apply trailer brakes first. A sure way to get passed by your trailer!

 

Skip marks are caused by all kinds of things, not just trailers. Driving without a trailer or with an unbalanced load can cause skips on any axle. The tractor rear will skip if the trailer is empty.

It usually isn't the front axle that skips because the load shifts to the front upon braking.
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« Reply #76 on: August 29, 2007, 05:21:13 AM »

Gus,

I did mistype the third sentence. Thanks! I fixed it.

"There were probably more skips on older trucks because most didn't have front wheel brakes at all."

I would disagree with that but I am not going to argue about it.

"Skip marks are caused by all kinds of things, not just trailers. Driving without a trailer or with an unbalanced load can cause skips on any axle. The tractor rear will skip if the trailer is empty."

I agree. They can also be caused by braking or accelerating over railroad tracks, bridge joints, or other uneven pavement. That bad habit was a surefire way to get fired when I was driving. But, that was a long time ago in a far away land. My kids say I am living in the past and they are probably right. It is, however, a nice place to visit..  Grin

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Nick Badame Refrig/ACC
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« Reply #77 on: August 29, 2007, 05:40:23 AM »

My Conclusion,

I think we all learned quite a bit about braking in this thread.

What I came away with from all your posts is to have all this info under my belt and use what is most comfortable

for me. And, most important, judge your speed for the grade your descending on.

This wealth of knowledge alone will better prepair me for my next decent.

Thanks All...
Nick-
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Len Silva
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« Reply #78 on: August 29, 2007, 05:56:03 AM »

Another point to remember with a stick is to START OUT IN THE LOWER GEAR.  If you get going a little too fast down hill, and are near max rpm, it can be difficult if not impossible to down shift.  If you miss a shift and cannot get it completely stopped with the brakes, it's going to be a bad day.

Len
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« Reply #79 on: August 29, 2007, 08:43:55 AM »

No matter what method you use to come down a hill (you could also use an anchor or Fred Flintstone's way) the bottom line is that you stay under control, at or under the speed limit, and reach the bottom of the hill relaxed without having to pry your hands off the steering wheel or go change your shorts.  Good Luck, TomC
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Tom & Donna Christman. '77 AMGeneral 10240B; 8V-71TATAIC V730.
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« Reply #80 on: August 29, 2007, 01:39:00 PM »

I hate getting old and demented!  What I MEANT to say is "What we have here is a failure to communabrake"!  He...he...he...!  Smiley Smiley Smiley   Broommmmmmmm.....!!
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Don Fairchild
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« Reply #81 on: August 30, 2007, 11:46:24 AM »

I heard on the radio last nite that a truck coming down from shaver lake with the driver riding the brakes got them to hot and at the bottom of the hill the right rear brake came apart and started a 160 acre froest fire. Don't have any other news. don't know if he was loaded or empty. Maybe R.J has some other info on it.

Don
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Dreamscape
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« Reply #82 on: August 30, 2007, 06:24:37 PM »

I know this one thing for sure, don't go any faster up a hill than you can go down. I have no problem taking it easy and letting the engine do the work. If I'm slow, so what. If other big rigs pass me, I don't care. I am in for the journey not how fast I can get there. I don't care about hot rodding the motor to make it fly, cause you gotta have the bakes to stop it. Don't get me wrong I like drag racing, but they have a parachute, I don't.

It all boils down to one thing, drive safe at any speed. Only go as fast as you feel comfortable with when having to stop suddenly, for that idot in front of you when he slams on the brakes after he cruised by at lightening speed because he thinks you can stop just as fast. I don't know about you but it involves my life and the dear person sitting next to me, let alone others on the road.

It just means common sense, and not all have that! Cry

Paul
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TomC
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« Reply #83 on: August 30, 2007, 09:10:25 PM »

Shaver lake hill is a nasty one with a big curve at the bottom.  About an 8% grade.  Good Luck, TomC
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Tom & Donna Christman. '77 AMGeneral 10240B; 8V-71TATAIC V730.
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« Reply #84 on: August 31, 2007, 07:23:07 AM »

Someone mentioned people waving at them with 1 finger.  Gee, I thought they were telling me I was number 1!  You would rather spend more time getting to the bottom. The other people that get upset are not the ones that pay for the repairs to your bus from wearing out parts.  Jack
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« Reply #85 on: August 31, 2007, 07:33:42 AM »

On the note on being told you're number one- I have two sayings that keep me from getting balistic from driving Los Angeles freeways everyday.  First- if someone cuts me off, I just say to myself "is this going to make any difference at the end of the day?"  Then if I get the number one middle finger, I just figure I won.  Keeps the blood pressure down.  Good Luck, TomC
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Tom & Donna Christman. '77 AMGeneral 10240B; 8V-71TATAIC V730.
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« Reply #86 on: August 31, 2007, 09:24:41 AM »

I just give 'em the peace sign or an OK sign and a big smile. I think it pisses 'em off even more.
Don & Sheila
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Len Silva
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« Reply #87 on: August 31, 2007, 01:31:20 PM »

I just blow them a kiss and mouth "I Love You".  Drives them crazy  Cheesy
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« Reply #88 on: September 01, 2007, 06:36:11 PM »

Someone mentioned people waving at them with 1 finger.  Gee, I thought they were telling me I was number 1!  You would rather spend more time getting to the bottom. The other people that get upset are not the ones that pay for the repairs to your bus from wearing out parts.  Jack

Jack back when I was a dumb ol' hick from the hills drivin' a big ol' purty large car with all kinds of chrome, stainless, chicken lights, and 10" straight stacks, I figured out that it wasn't a # 1 sign but rather a NEW JERSEY SALUTE, because everywhere I went and everything I did there they were giving saluting me with that one finger! Well I started paying attention and noticed they just didn't do it to me, but almost everybody! So that's how I figured out it was a salute because everybody can't be # 1 !
But anyways I found that if ya start bouncin' up and down and wav'n back at them (using all4 fingers & yer thumb), while just smile'n from ear to ear! It just drives the crazy that they didn't make ya mad, and that they think yer ignorant as they are, to be act'n a fool instead of gett'n all fired up and rasing yer blood pressure fer nut'n! JMHO FWIW Grin  BK  Grin
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Tim Strommen
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« Reply #89 on: December 24, 2007, 02:21:14 PM »

I have a co-worker who does something to really tick off those who give others "the finger", or when a driver does something really dumb (like cut him off).

He makes eye-contact and makes sure they see that he gives them a "tumbs down" all while shaking his head side to side and mouthing the word "no".  I've been in a car with him when he did this to a lady driving a Mercedes, and she just crouched in her seat and made like "a hole in the asphalt" after that.

I'm sure that others might not respond very well to a dissapproving vote on their driving, but it's better than swerving to run them off the road... Shocked


My two cents on the braking topic is similar to that of my performance driving knowledge - forced-air cooling the brakes (as I believe Chaz had suggested) is a good idea, so long as the incoming air doesn't have a lot of debris/contaminents.  Engine braking is easiest for speed control (i.e. get in the right gear for the hill and your rig's weight and let the centrifugal/pumping losses of the engine drag down the speed of the rig).  When "stock" engine braking is not enough, a supplemental engine braking system like a Jake will increase the pumping losses enough to not need to touch the service brakes (YMMV) - heat here isn't an issue (and I think that most will agree that on a 2-stroke, the engine will cool down quite a bit while the Jakes are running due to the lack of combustion on the cylinders).

Where Jakes aren't allowed or don't fit (due to regional restrictions [I'm in Ohio now and I see a lot of "No Engine Brake" signs around] or engine height clearance issues, since Jakes need taller valve covers) and there's extra drive-train length space available, a transmission retarder might be the right ticket (or you might have one on your tranny already) - caution should be used to ensure that the tranny fluid doesn't boil (transmission retarders work by restricting the flow of fluid which puts the fluid under imense pressure - creating a lot of heat), the heat in the tranny fluid needs to be rejected to the atmosphere to avoid build-up, so on heavy rigs or those with small fluid-to-air exchangers (and I think there are even some which exchange heat with the engine) - this may only be good for a short while, so "careful" use should still be the name of the game.  A temperature gauge on the tranny fluid inlet should help manage the heat within the tranny.

For those who are using transmissions where retarders are not feasable, Jakes are hard to find, or concern for shaft breakage is a design consideration - a Telma is probably the ticket.  A "Focal" model retarder can be mounted right to the differential's pinion input, and only requires electrical power to run.  Again, caution should be used in the design of a Telma installation (this is why Telmas are supposed to be installed by authorized installers/dealers) because the electrical system must be able to sustain the draw of a full-load Telma (up to 400Amps in some installations), and the heat which is rejected by the Telma must go somewhere "safely" (i.e. it must be kept clear of wires, air lines, fuel lines, etc.).

After that, one can consider retro-rockets and parachutes to slow you down - but if you need to resort to this extreme, just give me a call before you hit the road so I can get off it Grin.


As an asside, with automatic transmissions and engine/jake braking one must ensure that the tranny's torque converter is in "lockup" or the engine resistance will be lost without the direct mechanical connection to the engine (a torque converter uses fluid resistance to rotate the transmission relative to the engine when the engine "turbine" is rotating faster than the transmission "turbine", when the inverse is the case, the converter resistance is lower so the trany turbine can spin much faster than the engine turbine - letting the rig go down hill faster without much of the rotational energy getting to the engine.  A lockup clutch connects the engine turbine to the tranny turbine and the rotational energy can go both ways (engine to transmission or transmission to engine).  I believe there was an article by Brian Diehl on how to force this for an Allison HT754 transmission on this board, and he may still have the web page on this topic up on his website.  On my first trip, I found that downshifting out of "drive" into one of the numbered gears, kept the tranny in lockup all the way down to 15MPH (YMMV).  If you can hear your prime mover while driving, a transmission in lockup should maintain roughly the RPMs when you reduce your pressure on the accelerator - while a transmission out of lockup should have the engine RPMs drop off sharply with less throttle (causing a coast).


I won't comment on the braking method that anyone should use, I personally use the pumping but this is due to my track time in cars (where a constant pressure may end up with locked up wheels, whereas a "pulse" or "cadence" braking would allow wheels which had locked up a chance to re-gain traction and help keep the vehicle track correct).  With ABS, this isn't much of a concern - but since most of our old rigs don't have ABS, it's a point to bring up (if you're used to cadence braking you're more likely to use it correctly in an emergency).


Cheers!

-Tim

P.S. My ideal system would include both a Telma and Jakes, with the option to pick which or both should be used in a specific region (4-position switch Off-Jake-Telma-Both for selection), with both a separate pedal for retarder control and an air/retarder brake pedal to control the level of retarding power (with modern PWM tecniques, we can get more than a 2-to-4-step level control on electrically controlled retarders, now we can get more than 32 steps for better control). -T
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