| Author | Message | ||
| Jayjay (205.188.209.8) Rating: N/A |
While working on a 4106,we find it still has the Auxilliary Brake Control Valve. That's the gadget that limits the front brakes to 50% power. (Dry road/Slippery road) My question is to EXPERTS ONLY: (Sorry, no opinions wanted, only factual, experienced advise) Can I safely remove it and join the two pieces of copper tubing together with a union? I've read 'Da Book and it seems to be no problem, BUT...I want some confirmation from those who have BTDT. It's not my coach ,so I'm a bit more cautious about this sort of situation. Bus Warrior? R.J. Long? Gus Haag? Surely some of you real Pros can give me some solid advise. BTW, It works... we're just cleaning up some of the unused/unneeded items, especially those that may cause air loss. Thanks, and Cheers...JJ | ||
| Buswarrior (Buswarrior) (64.229.210.156)
Rating: N/A |
Hi JJ! Thanks for asking! I'd definitely remove it, and check to be sure you end up with the capability of getting full pressure to the front chambers. Put a gauge on a brake line at a chamber to be sure. It might be prudent to remove the lines and especially any elbows that led to this device, and replumb, (duplicating the stock coaches without it) direct from the pedal to the axle components. I assume that the device was up on the dash somewhere? Check the schematic, probably a quick release valve between the foot valve and the brake chambers. Be careful as to the choice of tubing size, go stock. I would be suspicious that there was no allowance in the brake timing for the addition of this extra plumbing, and that the front brakes may currently be coming on slightly late. (Remembering that the rules for brake timing were not there at the date of manufacture, they probably just added it in, brake timing be damned) From the perspective of 2004, they should have never been installed in a two axle bus, and should not have been installed in tractor trailers either, since the loss in brake force didn't really give back anything in steering control. If the front axle would slide in a low traction situation, the rest of the axles were right there about to slide too, so, nothing gained. Hard to convince oldtimers of this, but proper testing has proven their use just gives away stopping distance. ABS takes care of directional control on the modern equipment without the same compromise in stopping distance. happy coaching! buswarrior | ||
| Geoff (66.238.120.34) Rating: N/A |
On truck brake adjustment we used to adjust the front brakes with a little more slack than the rear brakes so they wouldn't come on as strong when first applied. For instance if the rear slack adjusters where set 1/4 turn backed off, the front ones would be adjusted to 1/2 turn. This would still keep the brakes adjusted within legal travel limits. Is that factual enough? You might have hurt a lot of people's feelings when you say you don't want opinions! --Geoff '82 RTS CA | ||
| Terrance A.Haag (Mrbus) (205.188.209.8)
Rating: N/A |
JJ, I agree with Buswarrior, remove it and keep the control valve for some future project where you would like to control air to open or close something. These old limiting valves were considered to be "cutting edge" at one time, but I for one have never had a vehicle with too many brakes, and did not want to shut part of them off. Geoff is also correct in that people used to delay the steering axel brakes with a little more slack in the adjustments, but if both fron wheels are adjusted correctly I want them as tight as the others. Consider the amount of braking they do with the weight shift forward when applied. My experience.  Gus Haag | ||
| RJ Long (Rjlong) (66.229.97.200)
Rating: N/A |
Gus - IIRC, 65% of the braking on our coaches is done by the rear duals, according to our local Bendix rep and the experience of our local transit shop. . . FWIW, RJ PD4106-2784 Fresno CA | ||
| FAST FRED (63.234.22.189) Rating: N/A |
ONLY an opinion , but I would KEEP the setup , unless the owner is POSITIVE the coach will never see ice , & snow , or heavy enough rain to hydroplane , in the next 5 decades. Opinion ONLy FAST FRED | ||
| Terrance A.Haag (Mrbus) (205.188.209.8)
Rating: N/A |
Hey RJ, I would never debate with you, or a Bendix Rep, but I just want to make sure that the remaining 35% of the braking gets applied as soon as possible. Since it has snowed here 21 of the last 23 days, I will not even touch Freds opinion. Gus Haag | ||
| Jayjay (205.188.209.8) Rating: N/A |
Thanks for the help guys. It's going to get axed. It's a southern bus, and has never seen the snow, and the new ownwer says he'll not break that record! ('66 PD-4106 2554) As far as hurting someones feelings, that would be most unfortunate, but I deemed it necessary under the circumstances. Beside, if they are that thin skinned, then they'll get mauled almost daily on the 'Boards. Those who are experts, not so experts, and those with only a wild guess as to what is going on at any one time, will most assuredley, mentally bury a paranoid person in short order. Cheers...JJ | ||
| Luke Bonagura (Lukeatuscoach) (12.75.168.163)
Rating: N/A |
Hi Folks: I have found this an interesting thread and I would like some further info. Having only been working in the bus industry for 41 years, I know just enough to be dangerous, so here is my question: When Bendix designed a total braking system for the GMC 4106, WHY did they install the "Auxilliary Brake Control Valve"????? And if it could been elimiated at the time of GM 4106 production from 1961 to 1964, then why was it installed. I realize that the state of the art changes in every mechanical system as years go on, but we are talking about is a COACH SAFETY ITEM!!!!! And I am not so sure in my own mind that we can, or should, remove one item of a designed system to cure a leaking problem????? And "BY THE WAY", I don't know the answer, I am asking the question for my own edification!!!!! Thanks for the expected "TECHINCAL" responses from "QUALIFIED EXPERTS"!!!! (And I am not being a smart A--, I am asking a serious question!!!! Thanks in advance!!! LUKE at US COACH | ||
| Tom Caffrey (Pvcces) (65.74.64.127)
Rating: N/A |
JayJay, that serial number looks a lot like ours, PD4106-2576. Ours is a 1964. I mention this just in case the owner isn't aware of it, and goes looking for 1966 parts. Something I didn't see brought up on this thread was the idea that because of the relay valve used on the rears, they should set slightly ahead of the fronts, which have no relay valve. At least I seem to recall running across this somewhere. I thought that a pricipal use of the limiting valve was to reduce the applied air when you were running chains on the rears. In that case, full pressure would probably lock up the steering set before the rears when running on snow or ice. That's when I would turn it on. And no, I wouldn't remove the valve, either. For what it's worth. Tom Caffrey Suncatcher | ||
| RJ Long (Rjlong) (66.229.97.200)
Rating: N/A |
Gus - Was only passing on some info I thought you'd be interested in, no argument was intended or implied. Simply trivia. JJ - Tell your buddy that PD4106-2554 was delivered new in March of 1964 as fleet number 200 to Monumental Motor Tours of Baltimore, MD. It's not a '66 model based on that VIN. 4106 production ended in June of 1965. Luke - Don't you have a couple of '06 shells out back? Seems to me one of them you mentioned previously had a DD3 system on it. I wonder if those units that came with DD3s also had the ICC brake that non-DD3s came with, or this auxiliary brake control valve JJ's talking about. Think maybe you could look? RJ PD4106-2784 Fresno CA | ||
| Jayjay (152.163.252.163) Rating: N/A |
Okay Gang thanks again for the input,...and here's more info. First off I made a mistake, the bus is a '64 model, not '66. The valve in question is not leaking, just a potential source of such. The main concern is that it will be inadvertently pushed into the Slippety Road position, and reduce braking effectiveness. The DD-3's in the rear, and the chambers in the front as well, have all been replaced, along with the shoes, so normal braking effectiveness is not an issue. I, for one, cannot abide the thought, that if I apply the brakes, that I'll only get 83% of what the system is capable of. Wouldn't a smart-assed attorney make a big issue of it in a wrongful death suit? I don't believe any of you Gentleman would diminish the braking on your automobile by almost 20% would you? Certainly not! Cheers...JJ | ||
| Tim Brandt (Timb) (12.8.192.60)
Rating: N/A |
First the disclaimer....I am not a lawyer but I beleive they would have a far greater issue with you removing a piece of a system designed by Bendix that leaving it intact in a wrongful death suit. IMHO | ||
| Jimmci9 (209.240.205.60) Rating: N/A |
did you know that you have less braking action on the front than rear, because of smaller brake chambers..( less force)... and smaller shoes...(less brake lining surface).. | ||
| J.L.Vickers (209.34.31.141) Rating: N/A |
Let me jump in here on this front brake limiting valve question. I have a operating manual for the PD-4106 Greyhound Coach it (Does Not) show the front brake limiting valve on the Greyhound PD-4106 coaches. I also have a operating manual for the standard PD-4106 (non-Greyhound coach)it shows and explains the use of the front brake limiting valve if coach is so equipped. Now this is the question that I have did the PD-4106 coaches have a control problem (skidding on wet or icy conditions)because of the 8V/71 engine weight in the rear as compared to the PD-4104 with a 6/71? I have heard that the PD-4106 coaches were very easy to get into a 180 degree spin on icy and slick roads. Perhaps this is the reason that GM had this front brake limiting valve as a option on the PD-4106? My self if it were my coach I would just leave it in place and not use it and leave it in dry road only. Just a thought on my part J.L.Vickers | ||
| Sam Sperbeck (204.248.119.254) Rating: N/A |
Hi J.L. Vickers, We have a former Greyhound 4106 with the ICC valve, but I don't know what it is supposed to be used for. Does your operators manual show that? Thamks, Sam Sperbeck La Crescent, MN | ||
| Buswarrior (Buswarrior) (64.229.211.253)
Rating: N/A |
Hello all. Re: Luke's question. I am prepared to be corrected, but I doubt that there was any more re-engineering of the brake system to add a "front wheel limiting valve" (FWLV) than to add the control plumbing to the dash and install the valve itself down below in place of the regular quick release valve. Also, this valve would have been "optional" equipment. Would carefully reverting the brakes to the standard stock configuration have any legal ramifications? A FWLV is installed midway between the front brake chambers, in the same place that a quick release valve in the rest of the buses. When the dash control indicates "DRY" road, there is no control pressure applied to the FWLV, and full brake application pressure from the brake pedal to the front chambers is achieved. When the dash control is put in the "SLIPPERY" road position, there is pressure applied down the control line to the FWLV. With control air applied, the FWLV will limit the air pressure directed from the brake pedal to the chambers by half. It is a simple air activated on/off regulator. The effect is that the front brakes do not squeeze as hard as what the brake pedal is calling for, extending the stopping distance of the bus. FWLV were invented to solve a problem that didn't exist, especially on a bus, that is: skidding front wheels, under braking, during low traction. There was little science involved in those days. Skidding front wheels due to brake applications had more to do with brake adjustment or other brake balance problems in the vehicle than some ideas about how loaded the front axle was. By design, buses enjoy good proportional loading of the front axle, compared to many trucks and with only two axles to work with, from the vantage point of 2004, FWLV should never have been installed on one. Here's the best test: Try to get a Bendix rep to tell you how to install a FWLV in an old two axle bus without one, and I expect you will get silence, if s/he doesn't outright try to talk you out of it. Or, ask for them to provide you with a technical explanation, of how the brake design went from full front axle braking, to FWLV, to automatic FWLV to the current ABS on the front axle. I expect that the answer in so many words will be: FWLV were unneccessary if brakes and the forces involved had been better understood at that time. Of course, make sure they are willing to put it in writing... Re: leaving the front slack adjusters a little loose and relay valves. Again, an ancient practice which was not based on much science. Leaving the slack adjuster a little loose, so that the chamber has to stroke a little longer does in a very small way slow down the brake application at that location. However, the closer that a brake chamber's stroke gets to it's adjustment limit, the weaker its power output, due to having to squeeze the internal return spring down, coil against coil. Never mind what happens if it actually bottoms out, in which case the brake force is seriously affected! The installation of relay valves in the rear are exactly for speeding up the brake timing in the rear. Relay valves are used to transmit the large volume of air directly to the rear chambers, without it having to travel from the brake pedal. If it came from the brake pedal, the rears would come on significantly after the fronts, which are much closer, and require less air volume, since they are usually smaller chambers. The brake pedal signals the relay valve, using air pressure, to direct air from the tanks to the rear chambers. The trick for the brake designer is to do the proper math on hose and chamber sizes and lengths, front and rear, and come up with the right mileages for the air to travel, so that front and rear come at at the same time. Again, hopefully, we are all maintaining our brakes properly, so any of these strategies to keep the vehicles going down the road without the paid driver complaining about them are not required. When one is travlling down the road at 60 mph, that works out to 88 feet per second. Just for fun, let's say that loosening off those front brakes that extra quarter or half inch of pushrod stroke adds a tenth of a second to their application. So, almost 9 extra feet after the rear brakes come on before any front braking takes place, And the rears came on somewhere around half a second after you slammed the brake pedal to the floor, thanks to the time it takes for the air to travel through the hoses, so that was 44 feet. Using RJ's 65/35 front rear split, you have delayed 35 percent of your braking by almost 5%. And then it is found that the power output of that 35% was further degraded because the brakes were willfully adjusted looser by the owner, who gets in the stand and gives everyone an "education" in their brake knowledge, which is later blown to pieces by the Bendix "expert witness", which any two bit litigation lawyer has on his speed dial. And therefore, men and women of the jury, it is not inconceivable that the bus in question would have been able to stop at least 6 feet sooner, avoiding striking the plaintif's auto, rendering him permanently disabled and unable to work due to his soft tissue neck injury... Or some such conjecture. Anyway... All that a FWLV can do is weaken the front brakes. Its removal eliminates any challenge as to its position during a collision. So: Adjust all of your brakes up as tight as you can get them without dragging any shoes when the wheels are spun, forget these particular myths of the past, and keep that FWLV in the dry road position, if you aren't removing it. how's that? happy coaching! buswarrior | ||
| Terrance A.Haag (Mrbus) (205.188.209.8)
Rating: N/A |
Buswarrior, Well said, and very descriptive. RJ. My remark about not debating was intended as a compliment to you and the Bendix Rep. Luke, After retireing from the bus maint. field, I am always amazed as to just how little I do know. Gus Haag | ||
| J.L.Vickers (209.34.31.141) Rating: N/A |
Hi J.L. Vickers, We have a former Greyhound 4106 with the ICC valve, but I don't know what it is supposed to be used for. Does your operators manual show that? Thamks, Sam Sperbeck La Crescent, MN Sam, The ICC Emergency Brake valve and I quote the PD 4106 Greyhound Operating Manual: USE OF ICC EMERGENCY BRAKE VALVE The emergency brake valve is located on panel just to the right of driver's seat. The two-position valve lever must always be in "OFF" position for normal operation. When valve lever is placed into "ON" position, brakes on rear axel are applied. Caution THIS "ICC BRAKE VALVE" IS FOR EMERGENCY USE ONLY WHEN OPERATOR IS UNABLE TO STOP COACH WITH THE USE OF SERVICE AND HAND BRAKES. MOVING THE LEVER TO "ON" PRODUCES A QUICK AND SEVERE STOP. THIS SYSTEM MUST NEVER BE USED AS A PARKING BRAKE AS LOSS OF AIR WILL PERMIT BRAKES TO RELEASE. The later P-4104 coaches were the first to have this ICC emegency brake valve installed from GMC. I hope this helps, J.L.Vickers | ||
| Jayjay (152.163.252.163) Rating: N/A |
Again my thanks to all of you kind souls. Buswarrior, and RJ, I was glad to finally get to meet you Arcadia, and I especially want to thank you for your long involved posts, and the time you took to produce them. I spent a long time with the Maint. Manual, reading the appropiate section many times, just to glean the information that you so succintly gave us. Gus, as usualy your input is appreciated (BTW, I regularly use the manuals you sold me for my 4905) If the damned thing was so wonderful, why wasn't it continued onto the later GMC models, not to mention the myriad other coach manufacturers lines? Seems to me I remember that when driving on snow and ice and the rear wheeels locked up, then a 180 was in the offing. At the SCCA Driving Schools, and Clayton Stryker's Anti-terrorist Driving Course, that's how a hand brake 180 turn is accomplished. Lock up the rear brakes first (with the hand brake) then cut the wheel and the rear end comes around quite readily. So why did GM decide to set up a situation that duplicates those conditions? Go figure, Huh? Again my thanks to you experts, for your time. Cheers...JJ | ||
| RJ Long (Rjlong) (66.229.97.200)
Rating: N/A |
"Seems to me I remember that when driving on snow and ice and the rear wheeels locked up, then a 180 was in the offing. At the SCCA Driving Schools, and Clayton Stryker's Anti-terrorist Driving Course, that's how a hand brake 180 turn is accomplished. Lock up the rear brakes first (with the hand brake) then cut the wheel and the rear end comes around quite readily. So why did GM decide to set up a situation that duplicates those conditions? Go figure, Huh?" ************************************************* Simple, JJ. The 4106 is considered by many to be the "Sports Car of Buses", so it seems only fitting that you should be able to do 180s, right? What the hey, let's find a big enough area, and we'll do some 360s, too!! Just like 911 Porsches - back off the throttle suddenly in the middle of the turn (especially on a slick surface), and BINGO - you're going where you just came from!! Wheeeeeeee!!!! ROFLMAO!!!! RJ | ||
| FAST FRED (63.234.22.92) Rating: N/A |
EVERY coach will swop ends if driven hard in the slipery stuff. With most of the weight in the rear , no design is immune. When the Slipery valve was an option , GM was just begining to sell coaches to other operators than just Hound. My guess is that it was a great help for small operators that got out before the roads were cleared & sanded. The liability issue was probably less a problem 40 years ago , as there was less lawyer cancer. Today with ABS , (if the driver is trained properly ), the coaches stop with less skill required ,unfortunatly the ability to spin remains . FAST FRED | ||
| Jayjay (152.163.252.163) Rating: N/A |
Hey RJ, I've done that (almost) in my 4905. Sideways in the rain in Louisiana last year, dodging an Idiot. Believe me sonny...with 134 ft between the axles, and 37 turns lock-to-lock on the steering, you're just a passenger. Folks who saw it thought I was a magician, but believe me, tha only magic was that I didn't smell worse than I did when it was over!!! Bent the front wheels against both curbs of the bridge, but other than that I got away clean. Snow? Ice? I'll stay in the back lot at the Flyin' J 'til the road gets dry. BTW, rear engined Ferrari's are as bad as Porsches. Cheers...JJ |