Please help with folding tail gate ramp.

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Good morning, Welding Web!I just joined your forum today, but I've been reading it for a while.I'm a hobby welder with an old Lincoln in the garage. My welds are without question, sub par. I learn by doing. So, I'm doing.My problem here today is more of a design issue.I'm building a folding ramp to replace the tailgate on my truck. It's going to be used to load/unload a ztr lawn mower.Because these mowers are back heavy, and low to the ground, a longer ramp is needed than you need to load a conventional mower.My solution is a spring loaded 8' ramp that is comprised of two 4' sections that fold down and out.It functions, it fits, the mower goes up and down.The problem is that it is so heavy, that after it comes down about 2/3 of the travel, it is very difficult to control.When it comes down hard, it puts tremendous stress on the center - where the two sections of ramp meet. It can be hard enough to break it.I'm going to post a few pictures, to better illustrate my situation, and to show some of the things I've tried to soften the blow. The legs that you see on the bottom are connected to the top section of the ramp, they fold down but are blocked from extending past a certain point. A chain is connected from the bottom of the leg to the middle of the bottom ramp.That helps lessen the impact to an extent, but doesn't make it come down any softer. The picture of the partially folded ramp was taken at the point where it begins to get difficult to lower without losing control.So, to clarify, I need a way to lower and raise the ramp with more control, and or soften the blow towards the middle. The springs I'm using are 140lb garage door extension springs, the largest springs available at any big box home center.I need to get this finished yesterday, so I'm going to try some things while I'm waiting for a response, like move the springs back further in the bed to put more tension on the whole thing.Thank you all very much for reading this.-Hundredaire Attached Images
Reply:I have a dumb question? why would quad ramps not work for you?not knocking the project, just curious.
Reply:Crawford,Thanks for your reply. I'm sure there's a commercially available solution.Quad ramps may work, but any ramp for my mower would probably have to be at least 8' long, which would be impractical to stow away in my short bed truck. Also I'm in the business of providing lawn care, which means I need a solution that is practical, and easy to deploy multiple times per day.Another question could be, why don't I just use the trailer that you can partially see in one of the pictures? Or maybe one of the other two trailers scattered around the back yard?Neither of those solutions will help me further my design or welding skills at all, nor will they give me something special and custom to be proud of while I'm spending my days performing menial labor tasks for money.The good news is that I moved the position of the springs back another 13" towards the cab of the truck, which seems like it's going to help a lot, a few more adjustments, and I hope to have a functional product by the end of the day.But I'd still appreciate all the suggestions that any of you have to offer.Thanks again
Reply:http://www.rockymountainatvmc.com/pr...FamilyId=14165that's what I use for my quad, they work great w/ my 6.5' bed, but i see your point in the fab part.what about attaching a hand crank winch to one side to help control the ramp? with the other side you could use the spring or double up both on one side?
Reply:First, put safety cables on/through those garage door extension springs!There is a h-u-g-e amount of energy in those springs when they are stretched.  When (notice I said "when" and not "if") one of those springs fails and lets loose, chunks of broken spring go flying at kind of high speeds, to put it mildly.  The safety cables don't help with the small broken pieces (like if the end hook breaks) but they do usually keep big chunks of broken spring from flying off or flailing about.Next, maybe you can change the ramp's deployment method/procedure and extend the ramp until the lower section's lip touches the ground and then 'slide' it out until the mid-span support foot reaches the ground.  All instead of just flopping the whole thing down and letting it crash to the ground.  Maybe another choice would be to change the hinge position from the 'bottom' (closer to the ground side of the ramp) of the ramp to the 'top' (closer to the sky side of the ramp, the side where the mower's tires ride on) of the ramp.  Then you unfold the (folded in half) ramp from the truck until the mid-span support reaches the ground, all aided by the tension springs helping somewhat to pull 'up' on all that weight, and -then- you unfold the other ramp section until the end reaches the ground.Oh, and watch out for the pinch-points on that ramp.  It has "Ouch" or "@#%%@!" or guillotine written all over it.  The best laid schemes ... Gang oft agley ...
Reply:Cut that sumbeech right down the middle so you have 2 lighter rampsEd Conleyhttp://www.screamingbroccoli.com/MM252MM211 (Sold)Passport Plus & Spool gunLincoln SP135 Plus- (Gone to a good home)Klutch 120v Plasma cutterSO 2020 benderBeer in the fridge
Reply:I'd dtich the springs all together and install a cable winch.Synchowave 180SD  Bernard 3500SS water coolerMillermatic 200Parker Plasma Tec 40dvOperating Engineers Local 12
Reply:If you keep those springs please run a cable threw themI always tried to work with the oldest hand on the job to gain knowlege but now I can't find any.
Reply:As others have said put a cable thru those springs.As for the ramp, how 'bout a torsion spring on each side of the ramp going from one section to the other There's some good size ones on the tarp arms of tandem dumps to take some of the weight of the tarp off the crank mechanism.We've built a couple of trailers at work that have a two setion ramp for small rollers and we've used a crank mechanism off a large boat trailer. It's a pia tho as it's damn slow...Mike
Reply:Originally Posted by MoonRiseFirst, put safety cables on/through those garage door extension springs!There is a h-u-g-e amount of energy in those springs when they are stretched.  When (notice I said "when" and not "if") one of those springs fails and lets loose, chunks of broken spring go flying at kind of high speeds, to put it mildly.  The safety cables don't help with the small broken pieces (like if the end hook breaks) but they do usually keep big chunks of broken spring from flying off or flailing about.
Reply:I'd say, learn to pick your battles.  If ya got a trailer, use it.  If I hire somebody for anything (which I usually don't)  and they show up with equipment that is obviously homebuilt,  I start second guessing my decision to hire them.My name's not Jim....
Reply:i would reverse the hinge so it was on the top. as you llift the unit off the bed, the legs would hit the ground and carry the weight. then you would unfold the top part, (the bottom of the ramp).
Reply:you would have to build some offset into the point where the ramp connects to the truck tailgate pivots..
Reply:Originally Posted by BoostinjdmI'd say, learn to pick your battles.  If ya got a trailer, use it.  If I hire somebody for anything (which I usually don't)  and they show up with equipment that is obviously homebuilt,  I start second guessing my decision to hire them.
Reply:Northern has this "Gorilla-Lift 2-Sided Tailgate Lift Assist" thing that might do the trick.http://www.northerntool.com/shop/too...6067_200316067http://www.gorilla-lift.com/I suspect it has some pulleys (like a block and tackle) with one end being sprung. Anyone know how these work or have a diagram?
Reply:I'll leave the safety issues to others with more experience with large springs on trailers and focus on geometry.  Notice that as your ramp descends, the line of action of the springs lowers dramatically, reducing the lifting effect of the springs on the ramp.  Just eyeballing the photos, it looks like the line of action of your springs is about 2/5ths of the height of the upper rear corner of the side panels so you are getting about 2/5ths of the benefit you would get if you could maintain the line of action at the top of the side panels.   Moving the point of attachment of the springs forward on the truck increases the tension of the springs but further lowers the line of action of the springs, counteracting the benefit of the greater tension.  If the line of action of the springs lowered to pass through the hinge between the bed and the ramp, you would get NO lifting effect.Notice that the Gorilla-Lift maintains the line of action of the cable at the top rail of the truck side panels.  This is very beneficial.  You might be able to eenhance both the safety and the effectiveness of your spring assist by moving the springs to be fully forward of the tailgate, enclosing them in steel tubes, providing a pulley at the top rear end of the side panels, and using a cable between the spring and the ramp.  In other words, duplicate the design concept of the Gorilla-Lift.Gotta run without refining this comment, but you get the point.awright
Reply:I saw this on instructables earlier today.
Reply:Originally Posted by forhireI suspect it has some pulleys (like a block and tackle) with one end being sprung. Anyone know how these work or have a diagram?
Reply:Ah the wonderful world of mechanical leverage with pulleys,,, It's amazing how few people realize what you can accomplish with pulleys these days. Far cry from 50 years or so ago when manual labor was still used to move things and Armstrong was the name of the game rather than electric or hydraulics. I've seen similar ramps on delivery trucks the mower repair guy in our area uses. I've never looked that close at it, but my bet is his unit is hydraulic. There's a lot that could be easily done with a  metering valve and some thought on geometry. As the ramp unfolds the pistons could act like syringes and suck fluid in rather than be pushed out. If you can control the speed that the flow moves in you would control the speed the ramp lowers. Wide open they resistance to closing would be small, but you'd still have to deal with the weight. A plow pump would probably be more than enough to run this if you wanted to go powered..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:They make the conventional ramp springs like you see on heavy equipment trailer ramps and such. They need a fairly large diameter shaft tho. Here's one for an 1" & 1/2 shaft. I don't know that I've seen them smaller than about a 1"&1/4 shaft but that doesn't mean they don't make them. On heavy trailer ramps you can add or take away the number of springs you feel you want. Usually two on a side. for a full ramp you could add however many you wanted one at a time.Here's an example: http://totaltrailerparts.com/store/i...05a90484e284bd"The things that will destroy America are prosperity at any price, peace at any price, safety first instead of duty first, the love of soft living and the get rich quick theory of life." -Theodore Roosevelt
Reply:I would really like to thank all of you for all of your ideas, and encouragement.There have been so many great suggestions, I'm not certain yet what I'm going to try first. I moved the springs back a bit, and this seems to make it workable for the short term. But I fully intend on making some changes like moving the hinges to the top, and experimenting with a diy version of the gorilla lift. Thanks so much for the explanation of those. I'd assumed it was just an extension spring in there, but the block and tackle makes much more sense, especially with the limited travel space.I just know that having two exposed massive extension springs can't possibly be a good idea.  Another thanks to all that warned me about that. I know it's really, really hard to see in my poor iphone pictures, but they've actually got cables through them already.But, they're connected to the same eyebolt that holds the spring, which probably isn't that good of an idea, either.So I'm going to get it together, then keep improving on it based on your recommendations,- all of them except picking my battles, anywayThanks again!-Hundredaire
Reply:Regarding using sheaves as force multipliers:  Remember that the stroke required of the energy source (in this case, the spring) is multiplied in the exact ratio of the force multiplication achieved with the pulley system.  You are already using quite a bit of stroke without using force multiplication - with it you could well over-extend the spring causing either breakage or permanent yielding of the spring and resulting loss of effectiveness.  I would consult with the spring manufacturer or spring design handbooks to determine the permissible safe extension of your springs.  A chat with an overhead door installer might also be very useful.Had forhire measured actual forces and distances in his experiment he would have found that the force multiplication (neglecting any friction in the sheaves) is exactly the number of parts of rope coming from the pulley block attached to the moving load and that the distance that the end of the rope must be pulled is multiplied by exactly the same ratio.  You run out of spring stroke pretty quickly if you use pulley blocks as force multipliers.It's pretty clear that the Gorilla-Lift is just a spring, a tube that is bolted or welded to the top of the side rail, a wire rope between the spring and the tailgate, and sheaves to guide the wire rope and keep it at the height of the top of the side rails.  Their price seems pretty reasonable since they've done most of the work for you, but you could easily duplicate the function at low cost using your springs with the addition of tubing, sheaves, and wire rope.  Provision of a number of holes along the tube and clevis pins to secure the fixed end loop of the spring would allow easy optimization of spring tension.I think Gorilla-Lift has proven that the concept can work fine.  Adding hydraulics would unnecessarily complicate things and be overkill for the task at hand.awright
Reply:Originally Posted by forhireYou may need to experiment with springs until you get the lift you'd like as the pulleys reduce the force by 1/4.
Reply:The Gorilla lift seems like the simplest. Just a spring in a tube, attached to a cable, that runs over a roller.Here's the patent application with diagrams.http://www.freepatentsonline.com/6126223.pdfHere's another one that's essentially the same thing, but with a couple of pulleys.http://www.freepatentsonline.com/5954383.pdfSo you're both right!I need to get some tube tomorrow.
Reply:That shows imagination and guts!!  Tommy Gate/ Lift Gate.  ~or~A set of aluminum ramps in a rack. Just an example...http://www.woodshedtech.com/ramp_rack/ The thing your dealing with is the bed-height, that is why so many landscapers use lowboy style trailers.The spring loaded ramps can be dangerous. We repair roll-up doors, ramp-doors and such, that come installed on trailers and I always seem to get those jobs... The safety cable is a nice idea.Here is another system. http://www.discountramps.com/truck-bed-ramp.htmCity of L.A. Structural; Manual & Semi-Automatic;"Surely there is a mine for silver, and a place where gold is refined. Iron is taken from the earth, and copper is smelted from ore."Job 28:1,2Lincoln, Miller, Victor & ISV BibleDannyThere is a trailer in your futureUA Local 598
Reply:Originally Posted by MoonRiseOh, and watch out for the pinch-points on that ramp.  It has "Ouch" or "@#%%@!" or guillotine written all over it.
Reply:Originally Posted by awrightNotice that as your ramp descends, the line of action of the springs lowers dramatically, reducing the lifting effect of the springs on the ramp.  Just eyeballing the photos, it looks like the line of action of your springs is about 2/5ths of the height of the upper rear corner of the side panels so you are getting about 2/5ths of the benefit you would get if you could maintain the line of action at the top of the side panels.   Moving the point of attachment of the springs forward on the truck increases the tension of the springs but further lowers the line of action of the springs, counteracting the benefit of the greater tension.  If the line of action of the springs lowered to pass through the hinge between the bed and the ramp, you would get NO lifting effect.Notice that the Gorilla-Lift maintains the line of action of the cable at the top rail of the truck side panels.  This is very beneficial.  You might be able to eenhance both the safety and the effectiveness of your spring assist by moving the springs to be fully forward of the tailgate, enclosing them in steel tubes, providing a pulley at the top rear end of the side panels, and using a cable between the spring and the ramp.  In other words, duplicate the design concept of the Gorilla-Lift.awright
Reply:I have been thinking of the same idea....I have a Hustler Mini Z mower that fits perfect in my truck bed.  I mostly mow residential yards so most of the time parking space can be an issue.  I thought if I could build something to drive my mower up/down that would save me from pulling a trailer.  Just wanted to know if you have loaded your ztr on the ramp and how it worked out.
Reply:Kindly post a picture of the front mounting for the springs.You might just want to stock up on rear windows for the cab.
Reply:Perhaps lift struts would work.