Trailer Ramp Extensions

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I have drawn a little bit to demonstrate what I want to do for my Hudson trailer ramps.  I can't load a car on there because they're too short, so I want to build an equal length extension.  I figure two 1/2 grade 8 bolts should hold up pretty well, but relying on their tensile strength alone seems a bit foolish.  I was thinking a strap would stiffen things up and make the joint bulletproof.  I'm curious to know if anyone has a different opinion, so take a look.
Reply:Looks like the idea will work. Note sure if the plate to tie the two together is heavy enough depending on the weight of the car. On big folding ramps I often see a "foot" that extends down to the ground at the joint. At that point the 2 ramps really don't support each other like in your design, but both are sitting on the leg and all the weight is taken up by the ground. Sort of like a bridge pier. Usually there's enough pivot in the joint to deal with ground irregularities..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:2 bolts....that's very little imo. When the vehicle gets to the point where the 2 plates meet, those bolts will be experiencing a severe amount of shearing stress. You could either build a support under that part, like you have in the front, or put more bolts, and increase the bolt size. Also keep in mind that grade 8 bolts, although stronger, are much more brittle. And if you are constantly using these ramps you need to account for the stress needed not to fatigue the bolts.Last edited by duffman1278; 08-01-2012 at 12:11 AM.
Reply:your two bolts bolting the face of two cross members together really are not going to do much as they will have too much leverage against them and would likely twist the cross member off.  If welding the two halves together is not an option I would use a flat plate in the channel iron like you have and go ahead and put a strap of flat bar connecting the two halves on the top and bottom leg of the channel (on the outside)  I'd say all the splice plates should be 8" minimum from the each side of the joint but that will depend on what kind of weight you are dealing with.  You could also put a spacer under the joint and use flat bar or round rod to go from end to end of the ramp, bent over this spacer to give you a truss effect.
Reply:I made extensions for my trailer with similar looking ramps as yours, only I made a hinge versus a fixed extension. The extensions are about 3/4 the length of the ramps so they fold down and overlap each other when in the "up" position. This avoids 12 feet of ramp sticking up in the air and makes it easier to lift them off the ground to put up for travel. I made the extensions 8 years ago and have loaded many cars, trucks and tractors up those ramps. The hinge is a simple “bind” to set the ramps and I think I used ¾” rod. I can take a picture if your interested.
Reply:why not just but weld the channel together with a fish plate on each side?  Does a cross member really help much in this design?I ask because I keep toying with the idea of extending the ramps for my skid steer trailer (7000lb machine) and I was thinking of just butt welding the 3" channel on each side.Hobart LX235Victor 250 Oxy-Acetylene Rig (welding and cutting)Bobcat 773F-350, 1999, 4x4, 16' 10K# trailerOutdoor Wood Burner - 10 cords/year
Reply:the shear strength of 1/2" grade 8 bolts is nearly 18,000 lbs each. two of those per side are not going to be the weak point that fails.miller thunderbolt 250vlincoln square wave tig 175 prolincoln idealarc mig sp250everlast tig 210EXTeverlast power plasma 50chicago electric (hf) 130 tig/90 arcchicago electric 90 amp flux wire3 sets oxy/acet
Reply:Thanks for all the input.  I like the hinge idea, but I would like to see what you did first.  I wanted the ability to remove the ramps in pieces since they will likely weigh over 100 lbs each at 8 ft long.  The truss idea is also interesting.  I could gusset the corners on the inside of the joint to help with twisting stress.  I think it will be plenty strong in that regard but I'm no expert.
Reply:I made two piece ramps years ago, and they've done very well.You might want to incorporate a mid-point support leg into the joint/hinge.  It carries the load independant of the trailer at this point, and allows for a longer ramp.  The safety factor is unbeatable.Notice how it's all pinned together.  This makes assembly easy, and the 1" cold roll is more than adequate to handle any shear loads."Any day above ground is a good day"http://www.farmersamm.com/
Reply:Are the ramps steel or ally? I see a lot of cracked ally ramps. You will need a support leg in the middle l dont think two bolts on their own will be enough.
Reply:They're made of 3" (5lb/ft) steel u channel and angle.
Reply:Then I would go with something like Farmersamm.
Reply:1+ for hinged with a foot. I made a set for a friend to load his mini excavator. They work great, but you might be surprised how much they move when loading up the mini ex, even on pavement. If they were rigid they would bend and break pretty quick.Ian TannerKawasaki KX450 and many other fine tools
Reply:Originally Posted by boatbuoythe shear strength of 1/2" grade 8 bolts is nearly 18,000 lbs each. two of those per side are not going to be the weak point that fails.
Reply:I'm out of town for a while so I can't get a picture of the hinges I made, but here's a computerized model of what I did. When extended, the faces of the ramp sections meet causing a bind and the ramps stay flat. When in the up position the sections overlap. Attached Images
Reply:That looks pretty clever.  What thickness plate and bar did you use?  Was it just hot rolled or something stiffer?  I'm all for simple and I'm not loading bobcats or tractors.  I like how the binding hinge puts the load on the hinge pin and vertical plate.
Reply:I beleive the plate is 3/8" and the pin is either 5/8" or 3/4". It's been 8 years so I can't remember and would need to measure when I get back home. the plate is just hot rolled, but I remember buying a higher quality rod stock from Mcmaster.
Reply:If your going to be hauling cars on this trailer i wouldn't space the ramp traction bars as far apart as in the pic with small car tires it would be like having it drop into a hole and it will be a pain when loading dead cars even with a come along or winchBacked my CATMA over your CARMA oops clusmy me  What would SATAN do ?? Miller Trailblazer 302 AirPakMiller Digital Elite  Optrel Welding HatArcair K4000Suitcase 12RC / 12 VSHypertherm PM-45Rage 3 sawRusty old Truck
Reply:I'm with Sam, mid point support, or just build some step blocks out of old scrap 2x4's and jamb them where they make good contact."Si Vis Pacem Para Bellum"Lincoln Idealarc 250 AC/DCMillermatic 251   Syncrowave 300   30A spoolgunLincoln MP210Hypertherm 45(2) LN 25(2) Lincoln Weldanpower 225 CV(4) SA200   1 short hood    SA250    SAM 400