Dollytrolley Posted January 8, 2017 Author Report Share Posted January 8, 2017 Then, when the skinny kid is at his highest, the fat kid jumps (falls) off. OK Steve..........just how s k i n n y or ......FAT .....was you as a kid? Drive on........(teteer or.....ta-otter.....) 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...
Dollytrolley Posted January 8, 2017 Author Report Share Posted January 8, 2017 Maybe I can add a couple thoughts from an unwashed engineer, pilot and now glass shop owner on the topic of weight, arm and moment. Moment is a made up number, an engineering tool used to figure these calculations. It isn't a graduation on a scale or measuring stick. Think of it in terms of balancing a teeter-totter. If there is equal weight on both sides, it will balance. Everyone has fun. (50# kid, 100" away from center on both sides.) If the fat kid (100#) and the skinny kid (50#) want to ride the teeter-totter, what has to happen? The fat kid needs to be closer to the fulcrum (hinge point) to make it balance. This is where "arm" comes into play. The 50# kid is still 100" out, where does the 100# kid have to be? Here is the calculation: 50# (weight) times 100" (arm) equals 5,000 (moment). This is the known skinny kid side. To calculate the fat kid side, take that moment, 5,000, divide it by the weight of the fat kid, 100#, and you get the arm length, 50". Therefore if you place the fat kid at 50" from the fulcrum everyone has fun, again. Now to transition this to loading a vehicle. You use the weigh times the arm for the moment or derivatives of this equation to calculate weights or locations of weights to make things work on your vehicle. Where it gets a little more abstract is on your vehicle, if you add up the weights taken from sum of the known arm locations you can then calculate the center of gravity (balance point) of the vehicle: Take the total weight at front axle (arm 0) and total weight at rear axle (x arm) added together divided by the total of the moments and you get the arm length of the center of gravity. So aver8er IF someone dropped off the truck in your driveway with the title taped to the rock chipped windshield........(glass-geeks just paste a Good Sam sticker over the rock chip) but anyhow.......what would you do with is HDT combo....? Drive on.......(What-if.....) 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...
Star Dreamer Posted January 8, 2017 Report Share Posted January 8, 2017 Any ideas ? In airplanes we often limit fuel loads to skinny by on weight and balance limits.....most aircraft burn fuel at high hourly rates so adjusting fuel loads from mostly empty tanks is common. Fuel often lingers longer in most HDT RV units. Maybe offload the Smart and have someone drive it.....? Offload the passenger and cargo....? Maybe the +14,000 steer load is within the safety margin of the axle and tires......and maybe the overload is not too large? Maybe install a Heavy capacity steer axle , wheels and tires? Maybe move the drive axle from long to mid or.....maybe short wheelbase?? What to do? Suggestions? Drive on......(feeling a bit nose heavy....) For a short distance and low speeds, I would not do anything. For longer distances and higher speeds, I would have an alternate position for the smart where I move it back towards the rear axle. Since there is no trailer you do not have to worry about trailer swing. We would need to know current location and weight of smart to calculate new locations that would work. Dave 2005 Freightliner Century S/T, Singled, Air ride ET Jr. hitch 2019 46'+ Dune Sport Man Cave custom 5th wheel toy hauler Owner of the 1978 Custom Van "Star Dreamer" which might be seen at a local car show near you! Check out http://www.hhrvresource.com/ for much more info on HDT's. Link to comment Share on other sites More sharing options...
Av8r3400 Posted January 8, 2017 Report Share Posted January 8, 2017 So aver8er IF someone dropped off the truck in your driveway with the title taped to the rock chipped windshield........(glass-geeks just paste a Good Sam sticker over the rock chip) but anyhow.......what would you do with is HDT combo....? Drive on.......(What-if.....) Well - We'd throw a windshield in 'er and run it down to the DOT office and get that title processed. Av8r34002012 Volvo VNL 730 D13 iShift & 2021 Grand Design Momentum 397TH I'd rather die trying to live - Than live trying not to die. -Leonard Perry Link to comment Share on other sites More sharing options...
Dollytrolley Posted January 9, 2017 Author Report Share Posted January 9, 2017 For a short distance and low speeds, I would not do anything. For longer distances and higher speeds, I would have an alternate position for the smart where I move it back towards the rear axle. Since there is no trailer you do not have to worry about trailer swing. We would need to know current location and weight of smart to calculate new locations that would work. Dave Dave, so if we assume that the Smart C G is currently 200 inches aft of the steer axle and the hitch pin is 335 inches aft of the steer axle that is a distance of 135 inches aft, so lets assume that the hitch pin location is the end of the bed deck configured suitable for securing the Smart so with a width of 62 inches divided by two we have the C G of the smart car C G at 31 inches forward of the hitch pin (335" - 31" = 304" aft of the steer axle). So lets move the 2200 aft 104 inches aft so the smart CG will fall 304" -285" = 19" aft of the drive axle......lets see what changes we can expect in the balance. So we crunch the numbers and ,Load C-1 was our starting configuration and then we relocate the Smart aft 104 inches and arrive at Loading C-2, listed below C-1. Load C-1: Hitch Pin 0 Lbs Steer axle is 14,032 Lbs Drive axle is 10,948 Lbs Wheelbase 283 inches Loaded C. G, 124.03 inches Fifth Hitch 335 inches Datum 0 Center of Steer axle Total Loaded Wt 24,980 Lbs Loading C-2: Hitch Pin 0 Lbs Steer axle is 13,224 Lbs (808 pounds less steer axle weight than loading C-1) Drive axle is 11,756 Lbs (808 pound MORE drive axle weight than loading C-1) Wheelbase 283 inches Loaded C. G, 133.19 inches ( Truck C G has moved aft 9.16 inches aft of the C-1 loading) Fifth Hitch 335 inches Datum 0 Center of Steer axle Total Loaded Wt 24,980 Lbs Smart Car moved from 200 station aft to station 304 So Dave If we have a 13.2K steer axle we are right on the limit .....IF we have a common 12K steer axle we are still over limit..... What else might we do to obtain better balance? Drive on......(104 inch Smart drive helps....some) 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...
Star Dreamer Posted January 9, 2017 Report Share Posted January 9, 2017 Since at baseline the truck front axle is almost at max capacity, best thing eould be to have the cargo shift to behind the rear axle and see if that helps. If the truck is only in the planning stages and has not already been singled, I would look to see if singling mid would help next. If truck is already built and moving cargo doesn't help enough or can't be moved, I would look to see how much added weight at very rear of truck is needed. As there is still some reserve on the rear axle of about 2k #'s, you could look at a heavier rear bumper, water tank, a thicker hitch plate or any number of other ways to add weight to the rear to take weight off of front axle. You would need to run the new weights through all of the configurations to make sure it works for all. Dave 2005 Freightliner Century S/T, Singled, Air ride ET Jr. hitch 2019 46'+ Dune Sport Man Cave custom 5th wheel toy hauler Owner of the 1978 Custom Van "Star Dreamer" which might be seen at a local car show near you! Check out http://www.hhrvresource.com/ for much more info on HDT's. Link to comment Share on other sites More sharing options...
Dollytrolley Posted January 11, 2017 Author Report Share Posted January 11, 2017 Since at baseline the truck front axle is almost at max capacity, best thing eould be to have the cargo shift to behind the rear axle and see if that helps. If the truck is only in the planning stages and has not already been singled, I would look to see if singling mid would help next. If truck is already built and moving cargo doesn't help enough or can't be moved, I would look to see how much added weight at very rear of truck is needed. As there is still some reserve on the rear axle of about 2k #'s, you could look at a heavier rear bumper, water tank, a thicker hitch plate or any number of other ways to add weight to the rear to take weight off of front axle. You would need to run the new weights through all of the configurations to make sure it works for all. Dave Dave, for sure some thoughts to ponder. It seems where we might be wondering to here might be.,,,,a weight and balance budget study....where we compose a set of mission requirements and then design the layout of the truck to achieve the mission goals. For the most part our HDT is the half of our RV combo lends itself to modification so we just need to stand back and look at the big picture and then start testing and refining various layouts to achieve our goal($).... Speaking of goals...... retirement has been interrupted in that I left Last Chance Peak at 67f and slogged 864 miles north mosty through blizzards back to Bend where snow in the back yard is 34 inches and getting deeper......uuuug Any how it appears that I will be out of this thread for some days until I can slog my way back south again....or freeze or whatever..... Drive on.....(already wore out first set of chains for the day....uuuug) . 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...
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