Dollytrolley Posted July 14, 2015 Report Share Posted July 14, 2015 For a flighty example, my other 18wheeler job involved a Boeing 747. With the 200 series 747 that is identical in nearly every aspect to the 100 series, except the number of brake disks. The 200 series has a major difference in shorter computed stopping distance over an identical weight 100 series, at any given airport. Both aircraft have the same number and type of tires (18). The Boeing data is hauntingly accurate for both takeoff and landing data. All braking data for transport category aircraft is also computed predicated on engine reversers being inoperative. If an airline has a plane with one or two defective brakes, they can still take off but have to invoke a substantial cargo or passenger weight reduction, in case they need to abort the takeoff. As you mentioned, Geo, as the temp goes above ISA, the braking efficiency decreases. In my bird-man days I dreaded formal brake testing.........if anything will prove how inconstant -of-a-pilot you are.........brake testing is the pilots Waterloo.......... Thank god I did not have to work the 747 brake tests, otherwise VegasFlyer might being hiking up out of the gully at the end of some far-off runway....... But I often was flying tests at Moses Lake WA when some of the 747 testing was in progress and brake tests were a HUGE effort with way too many engineers and tech-geeks making the pilots look bad........(ANYTHING that is bad in the flying game is.....the pilots fault....) Anyhow I have had a real chuckle with this thread so far.......IF only brake operations were as simple as a couple of math problems and a quick tire pressure checks (don't forget to count your tires) Now most folks know that Boeing only has a FEW engineers......ya right.......Anyhow when a couple plane-loads of brake-engineer-geeks unload for a brake test "program" it is a bit like a D-Day landing........you just did not know there were that many geek in the world..... One day I was hiding under a wing in the shade when I noticed a geek sitting under my other wing punching a ton of numbers into his HP-geek- calculator ...........I wondered over and ask whats up and he looked up and smiled and said ......."oh man I have the best "task" in the whole "program" I am graphing the "vertical Center-of-Gravity-Shifts-During-Braking"..........I stood there for a moment with a little pilot drool look ....then I said "Oh ya man, I get off on those calcs before every landing"...... Like Vegas says......The Boeing data is hauntingly accurate for both takeoff and landing data. The point is that REAL-WORLD brake and STOPPING performance calculations and testing is a HUGELY COMPLEX tasking and leaving one or two or 104 items out of the tasking will just not work in the real world.... Granted truck drivers are better "machine" operators in general .........heck truckers drive on two lane roads and meet and pass just a few feet apart (most of the time) ..........Pilots....heck many are hard pressed to hit near the center of a 150 ft-wide runway and IF they manage to stay on the runway they are hard pressed to get stopped in TWO Miles....... All kidding aside.......Vegas brings a important point home........it is likely more important how imperfect your tires and brakes are from the "perfect-datum-point...... Boeing has way too many charts that call for this and that item(s) failed .....but they do it for two reasons......one pilots are.......pilots.....AND as the old capt said......"sonny, it's-not-a-perfect-world". Drive on...........(leave plenty distance to brake........) 97 Freightshaker Century Cummins M11-370 / 1350 /10 spd / 3:08 /tandem/ 20ft Garage/ 30 ft Curtis Dune toybox with a removable horse-haul-module to transport Dolly-The-Painthorse to horse camps and trail heads all over the Western U S Link to comment Share on other sites More sharing options...
Vegas Teacher Posted July 14, 2015 Report Share Posted July 14, 2015 Hello All, I have been reading this and I am a Physics teacher that loves this entire conversation. Let's go back and remember something very simple, and I will quote a line from the old movie JFK........... "In a Physics Lab scientist can prove how an elephant can hang off of the side of a Mountain by its tail" So I can pull out a bunch of formulas to show almost any situation in most mechanical objects can be proven true or false. I can use several different really fancy equations to show both braking and stopping. There are a lot that deal with friction. Add in Sign, Cosign and Tangent on a TI 89 calculator with a graphing screen and I can show a formula of a how a mouse can kill a great white shark. My point is this formulas can show you and prove anything to you that you want them to when applied to the situation for the outcome you would like, even if some of these formulas and the way they were applied were a little less than perfect. We have to remember these trucks Like the Volvo 780 were designed in the tandem axle fashion, so why mess around with sound physics and solid mechanics. Buy the semi to be a semi. I am just being realistic. Why take apart something that was built and constructed a certain way to do a job. I am not saying anybody is wrong, but think about what you are doing to a machine that was designed by engineers and do you really have more mechanical knowledge than what they do? Later, O Keep on Dreaming and coming up with ideas, I love reading them. Link to comment Share on other sites More sharing options...
Jack Mayer Posted July 14, 2015 Report Share Posted July 14, 2015 Not all semi trucks are built tandem. They are built tandem primarily for the designated load. If the load is not large/heavy then the truck will be built single rear. Puzzle me this one....IF single rear trucks were so dangerous because they cannot stop, why are manufacturers building them? Must be lots of liability. Jack & Danielle Mayer #60376 Lifetime Member Living on the road since 2000PLEASE no PM's. Email me. jackdanmayer AT gmail 2016 DRV Houston 44' 5er (we still have it) 2022 New Horizons 43' 5er 2016 Itasca 27N 28' motorhome 2019 Volvo 860, D13 455/1850, 236" wb, I-Shift, battery-based APU No truck at the moment - we use one of our demo units 2016 smart Passion, piggyback on the truck -------------------------------------------------------------------------See our website for info on New Horizons 5th wheels, HDTs as tow vehicles, communications on the road, and use of solar powerwww.jackdanmayer.com Principal in RVH Lifestyles. RVH-Lifestyles.com Link to comment Share on other sites More sharing options...
G&K Posted July 14, 2015 Report Share Posted July 14, 2015 Possibly the broader point is that single conversions have to be engineered properly to be safe. Lots of people around now that know what they are doing which is great, but I well remember the trouble some people had with some Larry Z conversions in the early days. Geo George,Suzuki Celerio 998cc Yamaha NMAX scooter Work ride is Western Star N2 Tri-Tri tanker at 56,500kg loaded Link to comment Share on other sites More sharing options...
Dollytrolley Posted July 14, 2015 Report Share Posted July 14, 2015 I suppose now is not a good time to bring up how well the 550 Ton -10 axle crane carrier stopped ......... (think of it as 5 "singles" hooked together). Maybe the Vegas-Teach could graph to see if maybe the carrier had too many axles........ We topped the carrier at about 45 MPH .......that seemed plenty fast...... but it stopped pretty well.......never gave a thought to singling the carrier...... boy oh boy could we saved a bundle in tires......( might need the singles tires inflated to about 500PSI to carry the load......) As for the Mouse-that-knocks-off the Great White.........love to see the calcs prof......... Drive on........(Graph only when stopped.....) 97 Freightshaker Century Cummins M11-370 / 1350 /10 spd / 3:08 /tandem/ 20ft Garage/ 30 ft Curtis Dune toybox with a removable horse-haul-module to transport Dolly-The-Painthorse to horse camps and trail heads all over the Western U S Link to comment Share on other sites More sharing options...
Big5er Posted July 14, 2015 Report Share Posted July 14, 2015 Possibly the broader point is that single conversions have to be engineered properly to be safe. Lots of people around now that know what they are doing which is great, but I well remember the trouble some people had with some Larry Z conversions in the early days. Geo Oh yeah, lets throw old LarryZ into the mix. The POS trucks he built have nothing to do with this topic but a little smoke to cloud the subject is good. I notice that every one of you has skipped right on past Jack's post. MY PEOPLE SKILLS ARE JUST FINE.~It's my tolerance to idiots that needs work.~ 2005 Volvo 780 VED12 465hp / Freedomline transmission singled mid position / Bed by Larry Herrin2018 customed Mobile Suites 40KSSB3 2014 smart Fortwo Link to comment Share on other sites More sharing options...
G&K Posted July 14, 2015 Report Share Posted July 14, 2015 Nothing to disagree with in Jack's post. Most European trucks are single axle and I could probably make an argument that they are generally better units than most fleet trucks here. But if you're doing a conversion, do it properly. You take exception to this why exactly? George,Suzuki Celerio 998cc Yamaha NMAX scooter Work ride is Western Star N2 Tri-Tri tanker at 56,500kg loaded Link to comment Share on other sites More sharing options...
VegasFlyer Posted July 14, 2015 Report Share Posted July 14, 2015 Not all semi trucks are built tandem. They are built tandem primarily for the designated load. If the load is not large/heavy then the truck will be built single rear. Puzzle me this one....IF single rear trucks were so dangerous because they cannot stop, why are manufacturers building them? Must be lots of liability. Oh yeah, lets throw old LarryZ into the mix. The POS trucks he built have nothing to do with this topic but a little smoke to cloud the subject is good. I notice that every one of you has skipped right on past Jack's post. I'm your Huckleberry! Jack, I have read through this thread after reading your post and for some reason I have not seen one single post from anyone saying that single rear axle trucks are "unsafe because they cannot stop". Please enlighten me how you came to that conclusion. For my part of this discussion, I completely agree that a single rear axle truck would be sufficient for hauling a load within the design limits of the truck, etc. That thought would especially be relevant if you were specing out a new truck. This discussion is not, nor has it been, specing out a new truck and paying extra money to put tandem axles on a new truck or retrofitting tandem axles to an existing single axle truck. The discussion and original point was questioning the wisdom in paying money to diminish the additional safety and inherent redundancy that tandem axles provide. More specifically there is disagreement on whether having the additional tires will provide greater braking efficiency or added safety. Those arguing against my point seem to have either said it flat would not be any different whatsoever, or they say that it would be better, but not by much. Both of these points were either based on personal opinion or a simple formula, with no quantitative data. There was even one post stating that a bicycle, sports car and HDT traveling at the same speed would take the same distance to stop. Big5er, In reading your posts, it is rather interesting that you appear to be debating against me and the others who claim a tandem axle truck will have more traction and braking efficiency than a single rear axle truck, yet the technical facts that you posted actually bolster our side of the debate. When you wrote, "Yeah, bigger BRAKES make the difference, not bigger or more tires." , you provided additional proof that having the two extra wheel brakes would be like adding huge brakes to a single axle truck and would make a difference. A large difference according to Bendix. When you wrote, "One last point. Michelin claims that their super single puts more foot print on the road which helps in "TRACTION" for better "STABILITY". They also talk about better fuel economy and less weight, but nowhere do they mention better stopping ability with this larger foot print. I wonder why? ", you provided additional proof that having the more foot print by having four additional tires would provide more traction. More traction equates to more braking efficiency. Traction is synonymous with increased coefficient of friction. Increased coefficient of friction allows a greater applied braking forces. Greater applied braking force equates to more braking efficiency. As said before, I would hope that nobody involved in the discussion/debate is taking any of this personally. John John Southern Nevada 2008 Volvo 780, D13, I-Shift 2017 Keystone Fuzion 420 Toyhauler 2017 Can-Am Maverick X3-RS Link to comment Share on other sites More sharing options...
GeorgiaHybrid Posted July 15, 2015 Author Report Share Posted July 15, 2015 Vegas, I thought the "discussion and original point" of this thread was to find out what, if any, suspension systems would be an issue on a Kenworth or a Freightliner to single. I don't really care about the single vs tandem argument as my current class 7 Freightliner could have been ordered single (like mine is) or with tandems. I can also order a class 8 as a tandem or single. I feel entirely safe with the truck I have and the load that is on it and, after going over the numbers, will feel just as safe in a class 8 that has been singled. My concern was to make sure that any truck I searched for on the internet would be easy to eliminate the axle and change the wheelbase as needed and not waste my time searching for a hard to convert suspension system. I do know which ones to look at now and I appreciate all of the comments so far. I hope to see a LOT of you in Hutch as I will be hunting for bed options and builders there and hope to see a few more rigs than I was able to on my shortened visit to the ECR. OK, Intermission is over so let the tandem vs single, low pressure vs high pressure debate begin anew.... This is starting to look interesting... 2017 Kenworth T6802015 DRV 38RSSA Elite Suites2016 Smart Prime Link to comment Share on other sites More sharing options...
Dollytrolley Posted July 15, 2015 Report Share Posted July 15, 2015 Very interesting thread folks...... Stopping anything withHIGH-SPEED- HIGH-MASS has always been a chore if time, distance, and energy management are limited..... perhaps the link below might answer some questions and.........bring about more......... Take a peek at the link below...... http://local.aaca.org/siraaca/truck_safety.htm Drive on........(keep good stopping distance .........) On edit:..... the link above seems to not be concerned with axle-count but seems concerned with....... Inertia...... 97 Freightshaker Century Cummins M11-370 / 1350 /10 spd / 3:08 /tandem/ 20ft Garage/ 30 ft Curtis Dune toybox with a removable horse-haul-module to transport Dolly-The-Painthorse to horse camps and trail heads all over the Western U S Link to comment Share on other sites More sharing options...
VegasFlyer Posted July 15, 2015 Report Share Posted July 15, 2015 Vegas, I thought the "discussion and original point" of this thread was to find out what, if any, suspension systems would be an issue on a Kenworth or a Freightliner to single. I don't really care about the single vs tandem argument as my current class 7 Freightliner could have been ordered single (like mine is) or with tandems. I can also order a class 8 as a tandem or single. I feel entirely safe with the truck I have and the load that is on it and, after going over the numbers, will feel just as safe in a class 8 that has been singled. My concern was to make sure that any truck I searched for on the internet would be easy to eliminate the axle and change the wheelbase as needed and not waste my time searching for a hard to convert suspension system. I do know which ones to look at now and I appreciate all of the comments so far. I hope to see a LOT of you in Hutch as I will be hunting for bed options and builders there and hope to see a few more rigs than I was able to on my shortened visit to the ECR. OK, Intermission is over so let the tandem vs single, low pressure vs high pressure debate begin anew.... This is starting to look interesting... GeorgiaHybrid, You are correct that your original post was about singling a Kenworth T680 (Great Truck) or a Cascadia Evolution (Great Truck for a Freightliner....lol). I jumped in after Jack Mayer pointed out to you that you might consider leaving whichever truck you chose, tandem. Things seemed to go in an interesting direction after that so I am probably responsible for turning your thread on it's head.....lol. Seriously though, I am sorry, that was definitely not my intention. We could move this discussion/debate to another thread if you like? You seem to have a good handle on what will work for you in regards to your next truck. I just could not let some of the posts go unchallenged, more for the sake of new folks who might come in and read this bizarre thread at a later date. John John Southern Nevada 2008 Volvo 780, D13, I-Shift 2017 Keystone Fuzion 420 Toyhauler 2017 Can-Am Maverick X3-RS Link to comment Share on other sites More sharing options...
VegasFlyer Posted July 15, 2015 Report Share Posted July 15, 2015 Dollytrolley, Good link, thanks! John John Southern Nevada 2008 Volvo 780, D13, I-Shift 2017 Keystone Fuzion 420 Toyhauler 2017 Can-Am Maverick X3-RS Link to comment Share on other sites More sharing options...
VegasFlyer Posted July 15, 2015 Report Share Posted July 15, 2015 Here is a video that some folks might find interesting. WARNING: Some viewers may find this video offensive as there are graphic scenes showing two identically loaded trucks performing braking comparison tests and the trucks do not stop in the same distance..... https://m.youtube.com/watch?v=v57K1WW41K8 John Southern Nevada 2008 Volvo 780, D13, I-Shift 2017 Keystone Fuzion 420 Toyhauler 2017 Can-Am Maverick X3-RS Link to comment Share on other sites More sharing options...
Dollytrolley Posted July 15, 2015 Report Share Posted July 15, 2015 Vegas......great vids.......really shows the value of great brakes for Energy Management........ Obviously not all brakes are created equal..... Drive on.......(Have great brakes......) 97 Freightshaker Century Cummins M11-370 / 1350 /10 spd / 3:08 /tandem/ 20ft Garage/ 30 ft Curtis Dune toybox with a removable horse-haul-module to transport Dolly-The-Painthorse to horse camps and trail heads all over the Western U S Link to comment Share on other sites More sharing options...
GeorgiaHybrid Posted July 15, 2015 Author Report Share Posted July 15, 2015 John, Carry on.... It is fun when a thread gets a life of its own..... David 2017 Kenworth T6802015 DRV 38RSSA Elite Suites2016 Smart Prime Link to comment Share on other sites More sharing options...
Dollytrolley Posted July 15, 2015 Report Share Posted July 15, 2015 Something all of us that operate a RV HDT might consider ........most of us have had HD-Pickups at some time and some were dual wheel rigs with a fair size tire patch...........how many want to return to pickup brakes........even HD pickup brakes...... Brakes are a major factor why I have a HDT and my RV is fairly light.......but I don't want a heavy pickup ever again........ No.....I don't want to tandem a pickup .........thank you....... Drive on.......(pickups are for chasing parts.....) 97 Freightshaker Century Cummins M11-370 / 1350 /10 spd / 3:08 /tandem/ 20ft Garage/ 30 ft Curtis Dune toybox with a removable horse-haul-module to transport Dolly-The-Painthorse to horse camps and trail heads all over the Western U S Link to comment Share on other sites More sharing options...
noteven Posted July 15, 2015 Report Share Posted July 15, 2015 this thread hasn't come to a stop has it? "Are we there yet?" asked no motorcycle rider, ever. Link to comment Share on other sites More sharing options...
CDR Posted July 15, 2015 Report Share Posted July 15, 2015 Anyone on hear pushing the limits of our braking systems in this RV vocation, (single or tandem) is a fool in my book! That's one reason I have an HDT, increased safety factor. Besides, I have "never" bought a vehicle with the intent of wrecking it. Nor have I turned one down because another was "safer". I drive what I want/can afford to drive, period. So when carbon brake rotors are offered on HDT's, wake me up! Please! Curt 2001 Freightliner Century, 500hp Series 60, Gen 2 autoshift, 3.42 singled rear locker. 2004 Keystone Sprinter 299RLS (TT) 2 & 4 Wheelers! 2013 Polaris Ranger 800 midsize LE Our motto "4 wheels move the body, 2 wheels move the soul!" Link to comment Share on other sites More sharing options...
Jack Mayer Posted July 15, 2015 Report Share Posted July 15, 2015 I'm with you, Curt. I often hear how well an HDT stops our RVs. And that is true. BUT, I can tell you from actual braking tests that I have done that having disc brakes on the trailer with BluDot does stop the combo WAY faster than no trailer brakes or even properly adjusted drum brakes. So those who may believe that with an HDT that the trailer brakes are somewhat unnecessary are mistaken. Not that I believe a lot of people hold this opinion but I have seen it voiced. I did my brake testing when I put the BluDot and Kodiak disc brakes on my Royals International, years ago now. I say BluDot only because that was the actuator I was using. I'm not saying that IT made the major difference. But the disc's sure did. Jack & Danielle Mayer #60376 Lifetime Member Living on the road since 2000PLEASE no PM's. Email me. jackdanmayer AT gmail 2016 DRV Houston 44' 5er (we still have it) 2022 New Horizons 43' 5er 2016 Itasca 27N 28' motorhome 2019 Volvo 860, D13 455/1850, 236" wb, I-Shift, battery-based APU No truck at the moment - we use one of our demo units 2016 smart Passion, piggyback on the truck -------------------------------------------------------------------------See our website for info on New Horizons 5th wheels, HDTs as tow vehicles, communications on the road, and use of solar powerwww.jackdanmayer.com Principal in RVH Lifestyles. RVH-Lifestyles.com Link to comment Share on other sites More sharing options...
G&K Posted July 15, 2015 Report Share Posted July 15, 2015 There is a really good video out there that I can't find to post. Its terrifying because it shows the inevitability of a collision when a truck is following a car too closely. And the car has to make an emergency stop. And at highway speeds, too closely can be a LONG way back. That big separation from the vehicle in front is required due to the huge difference in performance between modern car braking and last gen truck braking. (Like my Volvo) It was a very sobering experience watching that video in CDL school because they explain the physics clearly. And it didn't look like the truck driver was doing anything wrong until you saw the math. Just another day on the highway. Geo George,Suzuki Celerio 998cc Yamaha NMAX scooter Work ride is Western Star N2 Tri-Tri tanker at 56,500kg loaded Link to comment Share on other sites More sharing options...
VegasFlyer Posted July 15, 2015 Report Share Posted July 15, 2015 I'm with you, Curt. I often hear how well an HDT stops our RVs. And that is true. BUT, I can tell you from actual braking tests that I have done that having disc brakes on the trailer with BluDot does stop the combo WAY faster than no trailer brakes or even properly adjusted drum brakes. So those who may believe that with an HDT that the trailer brakes are somewhat unnecessary are mistaken. Not that I believe a lot of people hold this opinion but I have seen it voiced. I did my brake testing when I put the BluDot and Kodiak disc brakes on my Royals International, years ago now. I say BluDot only because that was the actuator I was using. I'm not saying that IT made the major difference. But the disc's sure did. Jack, Have you done any brake tests on your New Horizon with the MORryde suspension? John Southern Nevada 2008 Volvo 780, D13, I-Shift 2017 Keystone Fuzion 420 Toyhauler 2017 Can-Am Maverick X3-RS Link to comment Share on other sites More sharing options...
Scrap Posted July 15, 2015 Report Share Posted July 15, 2015 I think part of what is tripping it all up is that the two trucks aren't built the same. Typically, not always but typically, pre RSD 6x4 tractors are built with 15x4 type 20 front and 16.5x7 rear brakes. 4x2's have 16.5x5 type 30 front and 16.5x7 rear brakes with sometimes up to 6" slacks. So your Brake Factors between the two are closer than just one axle away. Also, the weight of that axle is unsprung weight which, depending on suspension, can be a 1:4 to 1:9 ratio with the effectiveness of sprung weight. So ya it does makes a difference weight wise but it isn't 1:1. As for putting a distance to it I'm sure there are hundreds of NHTSA test results online somewhere. So now you take all the charts, numbers, videos, and math above, take in to account that 1.8" of your 2" stroke is taken up by fade/deflection/running clearance (ie: the feel 'sensitivity' mentioned above) even when set up right, and that 30% of trucks out there in 2014 had 2 or more brakes that weren't right, and you end up with 106 trucks on this forum that statistically don't make the cut. So you can see why it is important and probably worth 5 pages of discussion. Have we all rolled under our trucks and checked brakes today? EDIT - Wow I meant to say 4x2's and not 6x2's! Link to comment Share on other sites More sharing options...
topgashd Posted July 15, 2015 Report Share Posted July 15, 2015 I see not much has changed around here. Lots more numbers and statistics than seat time. I will answer the question regarding the low psi in the greater sized tire such as the dragster tire mentioned, psi is, pounds per square inch, the greater the surface area it is spread out over, the greater the force that is being exerted against it. Playing with calculator will scare you to death sometimes. Do NOT send me a PM, Cliick HERE to email me! In considering a truck like that you need to ask yourself just how much you enjoy meeting new people, such as tow truck drivers and heavy truck mechanics? Or perhaps, enjoying the great outdoors, like the side of the road while waiting to meet those exciting people? Link to comment Share on other sites More sharing options...
SuiteSuccess Posted July 15, 2015 Report Share Posted July 15, 2015 Pipe, Welcome back. We miss you around here. 2006 Volvo 780 "Hoss" Volvo D12, 465hp, 1650 ft/lbs tq., ultrashift Bed Build by "JW Morgan's Custom Welding" 2017 DRV 39DBRS3 2013 Smart Passion Coupe "Itty Bitty" "Don't go around saying the world owes you a living. The world owes you nothing. It was here first!" Link to comment Share on other sites More sharing options...
Broncohauler Posted July 15, 2015 Report Share Posted July 15, 2015 Hey pipe glad to hear from you bud. Link to comment Share on other sites More sharing options...
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