NoDirectionHome Posted July 9, 2017 Report Share Posted July 9, 2017 I'll disagree with one statement regarding the moments and forces. They are all transferred into and about the tire contact patch, not the axle, so I feel the diagrams are misleading, although the general point being correct. "There are No Experts, Do the Math!" 2014 Freightliner Cascadia DD16 600hp 1850ft-lb 18spd 3.31 260"wb SpaceCraft S-470 SKP #131740 Link to comment Share on other sites More sharing options...
rickeieio Posted July 9, 2017 Report Share Posted July 9, 2017 I've been pondering the issues of weight and balance on our rigs, and it occurred to me that finding the "station" of our tanks can be a bit of a WAG, if we have an enclosed underside. Perhaps not a big thing, but sometimes, little numbers add up. So, water weighs 8.3#\gal. Gray water likely is close to that. What does "black water" weigh? KW T-680, POPEMOBILE Newmar X-Aire, VATICAN Lots of old motorcycles, Moto Guzzi Griso and Spyder F3 currently in the front row Young enough to play in the dirt as a retired farmer. contact me at rickeieio1@comcast.net Link to comment Share on other sites More sharing options...
SuiteSuccess Posted July 9, 2017 Report Share Posted July 9, 2017 16 minutes ago, rickeieio said: I've been pondering the issues of weight and balance on our rigs, and it occurred to me that finding the "station" of our tanks can be a bit of a WAG, if we have an enclosed underside. Perhaps not a big thing, but sometimes, little numbers add up. So, water weighs 8.3#\gal. Gray water likely is close to that. What does "black water" weigh? Depends if you had Rice Krispies or enchiladas. ? 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...
phoenix2013 Posted July 9, 2017 Report Share Posted July 9, 2017 20 minutes ago, rickeieio said: I've been pondering the issues of weight and balance on our rigs, and it occurred to me that finding the "station" of our tanks can be a bit of a WAG, if we have an enclosed underside. Perhaps not a big thing, but sometimes, little numbers add up. So, water weighs 8.3#\gal. Gray water likely is close to that. What does "black water" weigh? I did a lot of "research" into the subject at one time. Once things dissolve it's still water (8.3/gal) regardless how nasty Link to comment Share on other sites More sharing options...
Darryl&Rita Posted July 9, 2017 Report Share Posted July 9, 2017 In the calculations I've been involved in, we use a relative density of 1.14. Assume water is 1.00, (stuff settles out) and it runs close to 9.5 lb/gal. I have been wrong before, I'll probably be wrong again. 2000 Kenworth T 2000 w/N-14 and 10 speed Gen1 Autoshift, deck built by Star Fabrication 2006 smart fourtwo cdi cabriolet 2007 32.5' Fleetwood QuantumPlease e-mail us here. Link to comment Share on other sites More sharing options...
Dollytrolley Posted July 9, 2017 Report Share Posted July 9, 2017 43 minutes ago, Darryl&Rita said: In the calculations I've been involved in, we use a relative density of 1.14. Assume water is 1.00, (stuff settles out) and it runs close to 9.5 lb/gal. Now we are getting........"Down AND Dirty here"...... Drive on.........(how much does the ......"honey wagon" weigh today?) 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 9, 2017 Report Share Posted July 9, 2017 Would politician black water have it's own category? "Are we there yet?" asked no motorcycle rider, ever. Link to comment Share on other sites More sharing options...
phoenix2013 Posted July 9, 2017 Report Share Posted July 9, 2017 5 hours ago, NoDirectionHome said: I'll disagree with one statement regarding the moments and forces. They are all transferred into and about the tire contact patch, not the axle, so I feel the diagrams are misleading, although the general point being correct. I tried to simplify the drawing (used in another article) hence the straight vector lines (it is misleading for this discussion). What's important is the rotational (torque) vectors shown. Those are true forces acting on the puller when the fifth tries to come forward. The tire patch besides bearing the weight (gravity) becomes a center of rotation. The torque circle originates from the tire patch so it's even larger than shown. We've instrumented a hitch pin and observed chucking. It's a very complex wave form which is primarily a result of an interaction between two vehicles with different weights, different wheelbases and most importantly different suspensions. On pickups the chucking you feel is primarily from the front truck suspension which gets precessed down by that torque circle when the trailer comes forward (for whatever reason) and then gets rapidly released when the trailer bounces back. Link to comment Share on other sites More sharing options...
phoenix2013 Posted July 9, 2017 Report Share Posted July 9, 2017 6 minutes ago, noteven said: Would politician black water have it's own category? It should it's truly rancid. H2O+HO4S Link to comment Share on other sites More sharing options...
Dollytrolley Posted July 9, 2017 Report Share Posted July 9, 2017 5 hours ago, Shawn Patterson said: Thanks for the offer! It's a good point, and yes, our holding tanks are forward of the axles so we could use them for ballast. I'm less excited about that though being as I am right at my GVWR for the trailer overall. Additionally, we aren't having any stability issues, and I like to keep about 1/3 of a tank of fresh water on board for emergencies. Personally, I am going to start with moving some heavy loads around and the RVH DRV Pinbox and see where that gets us. After that, I may consider having Henry add the bounce absorbers to my ET hitch. Good morning Shawn, Indeed I understand your desire to keep your liquids in your trailer tanks at a low weight and I tend to do the same on our basic 30 ft toy hauler even though it has 200 gal of fresh water tankage it is silly to use all that capacity since that simply tends to bring the marginal trailer tires to capacities that tend to bring tire failure to unacceptable levels. What I was suggesting is that perhaps a fresh water tank forward could be utilized to off load mass from a freshwater farther aft so in essence you would not carry more water weight but you would shift the weight forward. Now IF you decide to obtain more pin weight it is likely best to make a detailed inspection of the structure that supports the trailer hitch pin.......IF the folks that designed the trailer were indeed trying to keep pin weights light they also may have taken steps to keep the pin structure "modest" and so the structure may become "compromised" if you carve too far into any "margins" of overload designed into the trailer structure. Many structural engineers could help you determine the status of your structure. Indeed tandem class 8 tractors are highly dampening vehicles by design so light pin weights that my create unstable tows with lesser vehicles will tend tow well with a class 8 tandem.........however sudden "un-stabilizing actions" may exceed the normal dampening that you have come to expect and then you are now in a new realm of vehicle-dynamics that may or may not be nice..... I used to have to share space with a bunch of vehicle-dynamics-big-brain-geeks and they would not concentrate on pin weight matters nearly as much as "mass-distribution" in other words where the mass is placed is VERY important....... Now the dynamics of of air hitches / air hitch boxes attached to air-suspended tractors can be a dynamics-playground like batting big beach balls around by batting them with other beach balls............as Henry says ..........air hitch boxes hitched to air-hitches bolted to air-suspended tractors can get very .........."interesting""""""""""""""""""""""""""" Drive on..............(where is my trailer mass.......today) 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...
NoDirectionHome Posted July 9, 2017 Report Share Posted July 9, 2017 Quote they would not concentrate on pin weight matters nearly as much as "mass-distribution" in other words where the mass is placed is VERY important....... I've tried to make that point several times, but it seems only one guy gets it I'm hoping it's somewhat due to the fact the weight distribution is not easily changed. MOI! "There are No Experts, Do the Math!" 2014 Freightliner Cascadia DD16 600hp 1850ft-lb 18spd 3.31 260"wb SpaceCraft S-470 SKP #131740 Link to comment Share on other sites More sharing options...
noteven Posted July 9, 2017 Report Share Posted July 9, 2017 In my Carriage toyhauler the 110 gals fresh water tank and the two holding tanks installed below the fresh tank station almost offset each other weight transfer wise... nice design... The fluid load goes about 30% on the pin 70% on the axles. I always carry water to offset scooters in the garage. Being a motorcycle rider, and formerly involved in industry around the building of trucks equipped with large specialized equipment bodies, I understand mass centralization too. I've posted links to videos from the U.K. and Australia showing models designed to show how the location of equipment and cargo affects RV trailer handling. Well designed single axle caravans are towed by cars and small SUV's... without the use of "sway" gadgetry. They response is generally remarks about the presenters' accents... "Are we there yet?" asked no motorcycle rider, ever. Link to comment Share on other sites More sharing options...
Dollytrolley Posted July 10, 2017 Report Share Posted July 10, 2017 15 hours ago, NoDirectionHome said: I've tried to make that point several times, but it seems only one guy gets it I'm hoping it's somewhat due to the fact the weight distribution is not easily changed. MOI! No Dir, Indeed it wants to make you want to pull your hair out when you see the "herd" become "addicted" to the "heavy-pin--weight" theory when in FACT the real study should involve the ACTUAL weight distribution of the trailer and NOT seeking huge pin weights in a effort to somehow luck into a stable tow. A arm of 1 ft with 100 pounds applied yields 100 ft/ lbs at the rotation point...........an arm of 10 ft with 10 pounds applied yields 100 ft/ lbs at the rotation point ........... Arm and mass (weight) matter......... Drive on.........(pin weight often leads to ...........mass confusion) 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...
NoDirectionHome Posted July 10, 2017 Report Share Posted July 10, 2017 4 hours ago, Dollytrolley said: pin weight often leads to ...........mass confusion good one! "There are No Experts, Do the Math!" 2014 Freightliner Cascadia DD16 600hp 1850ft-lb 18spd 3.31 260"wb SpaceCraft S-470 SKP #131740 Link to comment Share on other sites More sharing options...
rickeieio Posted July 10, 2017 Report Share Posted July 10, 2017 Just had that discussion yesterday with a new rv'er. He was comparing the weights and towing experience between a tandem bumper pull, and a tandem pop-up of the same weight. He got glassy eyed when I tried to explain why the pop-up would pull better. But then, he thinks his VW Touareg handles the (6500#) bumper pull just fine, even after pulling it with my F-150 Eco-Boost. But the Touareg is a diesel, so it has to pull better. Oh, he's my son-in-law....................... KW T-680, POPEMOBILE Newmar X-Aire, VATICAN Lots of old motorcycles, Moto Guzzi Griso and Spyder F3 currently in the front row Young enough to play in the dirt as a retired farmer. contact me at rickeieio1@comcast.net Link to comment Share on other sites More sharing options...
Shawn Patterson Posted July 10, 2017 Author Report Share Posted July 10, 2017 22 hours ago, Dollytrolley said: Good morning Shawn, Indeed I understand your desire to keep your liquids in your trailer tanks at a low weight and I tend to do the same on our basic 30 ft toy hauler even though it has 200 gal of fresh water tankage it is silly to use all that capacity since that simply tends to bring the marginal trailer tires to capacities that tend to bring tire failure to unacceptable levels. 1 6 Ahh, gotcha... Yes, that makes sense and it will be something that I will consider doing. I am going to implement the easier items first and see how close we can get to the 20% mark. I'm not excited about going to the trouble/expense of moving that fresh water tank if I can avoid it. My experience with previous trailers has been that it is rarely an easy job for something like that. If anyone with a larger DRV trailer has experience otherwise, I would love to hear about it. You bring up another good point about the structural capability of the unit to handle redistributed weight. This is something I would certainly take up with DRV before making a change like that to see if they had any advice other than "we don't recommend it"... Shawn and Andrea Elvis the Cheagle Dog 2013 Volvo 730 / iShift / D13 XE Package / ET Hitch 2016 DRV Mobile Suites 43 Atlanta 2018 Jeep Wrangler Rubicon Unlimited Read the blog at 40foothouse.com Link to comment Share on other sites More sharing options...
Dollytrolley Posted July 10, 2017 Report Share Posted July 10, 2017 15 minutes ago, Shawn Patterson said: Ahh, gotcha... Yes, that makes sense and it will be something that I will consider doing. I am going to implement the easier items first and see how close we can get to the 20% mark. I'm not excited about going to the trouble/expense of moving that fresh water tank if I can avoid it. My experience with previous trailers has been that it is rarely an easy job for something like that. If anyone with a larger DRV trailer has experience otherwise, I would love to hear about it. You bring up another good point about the structural capability of the unit to handle redistributed weight. This is something I would certainly take up with DRV before making a change like that to see if they had any advice other than "we don't recommend it"... Shawn, Indeed my suggestion of a water tank forward seems like a near-free-lunch........however like many "free-lunches" the devil is in the details. Here is something that NoDirection and I have been harping on and that the subject of weight distribution and while it can be a complex subject that vehicle-dynamics-geeks really love to flog the basics for RV trailers boils down to the farther aft of your trailer axles you go the less load (mass / weight) you should place in your trailer..........perhaps consider moving the big recliners near or forward of the axles for your tow times as an example........Just like my torque-wrench example in the previous post those heavy recliners at the back wall of your trailer have a considerable force factor on your potential yaw vectors (swerve)........ Maybe moving your recliners forward may not add much weight to your hitch pin but it will lessen your yaw factor by a considerable moment (Weight times Arm=Moment)........ RV units tend to be less than ideal in vehicle dynamics but a tandem class 8 tractor has many advantages of dampening until the point of stability reaches zero and then any efforts we have made to improve the trailer stability will pay rewards....... Drive on.........(how tail heavy is your RV?) 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...
Alie&Jim's Carrilite Posted July 10, 2017 Report Share Posted July 10, 2017 Locate a lead recycler in your area. I used to buy 80lb lead bars when other companies couldn't figure out why their big 'ole boats heeled to one side. Before moving tanks and what not, it might be easier to buy 200lbs and move it around the storage areas to find the optimum spot. Alie & Jim + 8 paws 2017 DRV Memphis BART- 1998 Volvo 610 Lil'ole 6cyl Cummins Link to comment Share on other sites More sharing options...
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