Help with ramp material size....

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Well yall I guess this is where a mechanical engineering degree would come in handy but I currently don't have one so maybe the fine folks on here can help me. On to it, I have a customer that purchased a box truck to for his lawn business, he currently has two trucks with trailers and is trying to cut down on his storage foot print. From the beginning he wanted the typical dove tail with twin gates but the back of the box doesn't have enough meat to with out a bit of additional support, so he settled for the tow ramp option since grass season is about to end along with his money. I have built a complete 4' fold down gate before out of angle that is still in use 5 years later and done multiple trailer repair/projects but this one needs more brain cells. The ramps will 10' - 12' long and 16" wide, most gates are 1.5"x1.5"x1/8" wall square tube and they span 4' just fine. On the gate the load is usualy held by two of the how may ever runners it has on the ramps it will be held by four longitudinal runners both sides. Mower is right about 1k lbs plus operator brings us to 1200 total. Will be skinned on top with expanded metal probably 3/4" #9 or thicker so it wont deform as much. I was thinking of 2"x2"x1/8" square or stepping up to 2"x3"x1/8" rectangle to gain more of a web to them. They would be cross braced every so often with the same material (imagine a ladder in your head) for rigidity and holding up the expanded metal. Making the truck connection is a breeze compared to figuring out how to not crush ramps.  Just short of buying, building, breaking and building again till it holds, I have no way of know what I should build from. Hoping some of you more experienced fellas can help me out. So there it is let it fly the good the bad and the ugly.Realized this might belong in the projects section so my apologies if I got it wrong. If so the powers that be could move it Last edited by KineticWeldingServic; 09-24-2014 at 03:15 AM.Reason: added a sentenceRanger 250 thick stuffHobart Handler 140 not thick stuffthe pane and oxy setup
Reply:After crunching some numbers and finding out that 1.5''x2.5''x.120'' and 2''x.120''square tubing weigh the same per foot I am leaning towards the rectangular tube....time for bed now, good ole night shift.Ranger 250 thick stuffHobart Handler 140 not thick stuffthe pane and oxy setup
Reply:I've loaded 4000 LB autos for years with a pair of 12' ramps made from Micro Lam wooden beams 14" X 1.75. They are heavy! Have you considered a truss made from two pieces of aluminum square tube. Give them a taper at each end, weld the ends together with a series of varying length spacers. Under side will need a spreader keeping the bottom chord in place. These guys deploy ramps 10 times a day. 200 LB ramps will either leave them exhausted or turn them into sheet rockers.
Reply:I made my ramps from 3" channel alumimum, and 2.5" equal leg aluminum angle spaced 6" apart several years ago 8 feet long. I've loaded many, many iterations of 6K rolling loads with these for years never bending them. They weigh 26#, and 28# respectively and are easy to handle/carry. I always leave them chained down/locked also or inside the shop but never an "easy grab" for anyone desiring them.SlobPurveyor of intimate unparalleled knowledge of nothing about everything.Oh yeah, also an unabashed internet "Troll" too.....
Reply:Some where in this neighborhood there's a guy with a box truck they added a beaver tail too, and then built the folding ramps. I wish I knew where he was at, so I could take picts for you. The rig is massive though. The 3' off beaver tail that they added is triangulated to the back of the truck and works to not only support the ramp, but helps with part of the counter weight system they rigged to the top of the box so they could use cables to help with the weight of the ramp.A better system I've  seen is guys who use a box truck with one of the big lifts that fold down on the back. ( I'm drawing a blank for whatever reason on the normal name this morning). They simply drive the machine onto the lift, raise it up and drive into the truck. Same unloading..No government ever voluntarily reduces itself in size. Government programs, once launched, never disappear. Actually, a government bureau is the nearest thing to eternal life we'll ever see on this earth! Ronald Reagan
Reply:DSW had a good idea there about the counter weight system the rear frame of most box truck is usually the only part of a truck box with any strength . and you could always add some bracing on the inside to a floor cross member .
Reply:Originally Posted by DSWSome where in this neighborhood there's a guy with a box truck they added a beaver tail too, and then built the folding ramps. I wish I knew where he was at, so I could take picts for you. The rig is massive though. The 3' off beaver tail that they added is triangulated to the back of the truck and works to not only support the ramp, but helps with part of the counter weight system they rigged to the top of the box so they could use cables to help with the weight of the ramp.A better system I've  seen is guys who use a box truck with one of the big lifts that fold down on the back. ( I'm drawing a blank for whatever reason on the normal name this morning). They simply drive the machine onto the lift, raise it up and drive into the truck. Same unloading.
Reply:Originally Posted by M J DAre you talking about a Tommy lift gate?
Reply:You fellas can sure come up with more than one way to skin a cat. Aluminum cat skinning fab don't have the equipment. Premade fold out one would be the stuff except for the little zero turn mower tires.Tommy lift gate would be the stuff but the truck doesn't have one.Rough weight for steel would put them right around 130lbs a piece. Wood....intresting, not ruling it out. Time to keep thinking thanks yall.Ranger 250 thick stuffHobart Handler 140 not thick stuffthe pane and oxy setup
Reply:Used Tommy gates can often be picked up cheap. Check with wrecking yards that cater to medium and heavy trucks..No government ever voluntarily reduces itself in size. Government programs, once launched, never disappear. Actually, a government bureau is the nearest thing to eternal life we'll ever see on this earth! Ronald Reagan
Reply:That would probably be the safest way to go about.......not sure if that is the solution my customer is after.Ranger 250 thick stuffHobart Handler 140 not thick stuffthe pane and oxy setup
Reply:Yeah a 1200 to 1500lb zero turn coming sideways off a ramp doesn't sound like  a whole lot of fun.I've spun a track loader sideways on a wet set of steel ramps going up to the beavertail on a trailer. even though it was a lot closer to the ground than the deck of a box truck, with a heavy duty set of ROP's, and stayed upright and on the ramps, I probably could have used a change of shorts when it was over..No government ever voluntarily reduces itself in size. Government programs, once launched, never disappear. Actually, a government bureau is the nearest thing to eternal life we'll ever see on this earth! Ronald Reagan
Reply:Hi KineticWeldingServic,Whenever choosing material I use these calculators.  http://civilengineer.webinfolist.com/str/micalcrh.phpYou need to keep units consistent (always use inches, not inches & mm).You are looking for the highest Ixx/Area.  Without going into the detailed equations, Ixx is the strength and area is the mass, so you'll end up with the highest strength to mass ratio.Orientation matters!!!  Ixx is the highest number for C channel, but if you rotate it 90deg (c becomes a n), then you need Iyy/Area.Tim
Reply:For the material you're considering 1.5x2.5x.12 has an area of 3.73 in squared, and Ixx of 1.95 (if you lay it tall), or Iyy of 0.73 if you lay it on it's side (flat).  Strength to mass of 0.52 if you lay it tall and 0.20 if you lay it flat.  So it's 2.5x less effective if you lay it on its side.2x2x0.15 has an area of 3.98 inches squared (so it's slightly heavier), and Ixx=Iyy=1.33.  So strength to mass is 0.33.  You're actually better off using the 1.5x2.5 material if you lay it tall.Tim
Reply:tprothma, I am thank full for your brain cells, knew I should have stayed in college longer. I will be honest though and go ahead and admit I still don't understand what the numbers mean If I use the rectangle tube it will definitely be turned 'tall way up' otherwise that would defeat the purpose of using it. Now I am waiting on another off day to call the local suppliers for availability and prices.Ranger 250 thick stuffHobart Handler 140 not thick stuffthe pane and oxy setup
Reply:Well here is the conclusion everyone has been waiting on I declined this job. That is probably what some yall was thinking I should do. My reason after hearing from everyone and doing a bit of thinking the 'L' word liability if he were to overload them or just be negligent it would all come back to me. Ramps in the best of situations can be tricky (see YouTube) much less with zero turn mowers 42" off the ground. It is rare for me to say no unless its to the dog these days but, in this line of work I think it is getting more common for me. Again thanks y'all for all the help, i kinda feel like I got my tail between my legs and headed back to the porch on this one.Ranger 250 thick stuffHobart Handler 140 not thick stuffthe pane and oxy setup
Reply:Originally Posted by KineticWeldingServicWell here is the conclusion everyone has been waiting on I declined this job. That is probably what some yall was thinking I should do. My reason after hearing from everyone and doing a bit of thinking the 'L' word liability if he were to overload them or just be negligent it would all come back to me. Ramps in the best of situations can be tricky (see YouTube) much less with zero turn mowers 42" off the ground. It is rare for me to say no unless its to the dog these days but, in this line of work I think it is getting more common for me. Again thanks y'all for all the help, i kinda feel like I got my tail between my legs and headed back to the porch on this one.