Regarding use of 2x4s vs. 2x6s on sides, I decided to use 2x4s and
center support (support the ramp in the middle), which I can do with
cinderblocks or jackstands, etc. Makes ramps a lot easier to deal
On Thu, 25 Oct 2007 11:48:26 -0500, Ignoramus20839
Just as a reference, my father made some ramps of 3"x12"x~10' rough
sawn live oak he used for over 30 years to load levee rollers on the
bobtail IH. The levee rollers were concrete spools with heavy angle
frames that weighed about 4800 lbs. We'd put three on the truck and
deliver them around to implement dealers, which is why I had a
commercial license at 16. Dad had mounted a hydraulic winch in the
bed, and we'd tilt the dump bed about 5 deg. up to load and unload.
Those old loading ramps never broke, although they did develop a
raised ridge over time down the middle. I guess something to do with
the way they were sawn.
Every time I took a load through the old Baytown tunnel, I'd have to
stop for an inspection. The chain boom handles had to be safety
wired, 2"x4" cleats nailed behind the rollers, etc. I guess they
didn't want to see three rollers unload down the tunnel as I exited.
The ramps were also a bear to handle, being pretty damn heavy. The
attachment to the bobtail (single rear axle truck) was just a small
angle bolted to the ramp set in a groove formed by a piece of bar
welded to the back of the bed.
On Oct 25, 5:39 pm, Ignoramus20839 <ignoramus20...@NOSPAM.
While you are playing with the design, think about a couple of blocks
you could put between about the middle of the ramp and the ground. If
you had a block in the middle of the span, it would be like two 4 foot
ramps in series. And I think the capacity would be much higher. So
you could use you original design which would be lighter to set in
You don't have to have it height adjustable. Just a reasonable size
so it will fit under the ramp. If the ramp is being used for a low
thing, the support may be close to the high end, and the unsupported
length a two foot span and a six foot span. If it is being used on a
very high thing, the support may be close to the ground end, and
again you have a two foot and six foot span. But when you play with
the program you will see a six foot span is much better than an eight
Of course cutting in to two four foot spans is even better, and those
aluminum support jacks look like a nice solution.
Using deflection as a criterion for beam design is not to be condoned.
The beam MUST be designed with an allowable BENDING stress in the top
and bottom flange of the beam.
Once this stress is at an acceptable level can the design be checked
for deflection and, if too large, the beam be made stronger TO REDUCE
Starting with deflection one has no idea what the bending stress is
and whether it has exceeded the allowable limit.
Since I generally do not design in wood..... if someone will supply
the info on type and grade of lumber, and allowable bending stress
(from a building code, perhaps) I would let you know the load
On Oct 25, 2:22 pm, Ignoramus20839 <ignoramus20...@NOSPAM.
Car jack stands work well for this as long as you tie the ramps to the
vehicle and use a crosswise plank between the stands and the ramps.
The ramps may twist if supported only by the narrow stand tops, and
when the vehicle sinks from the load, the ramp ends lift off the
ground and slide. Put some tiedown eyes on the sides of the ramp.
Why not nix the idea of the 2X4's on the sides and do this instead. Make
your own metal ramp ends that you fit to the ends of the ramps and then rout
slots on the underside of the boards where you run a couple of 1/4 or 3/8
rods that are fastened to the metal ends. This way the lumber will be in
compression, and the steel will restrain the wood from flexing too much.
I did something similar to some saggy rafters and was able to jack the whole
I like this idea, though the earlier idea of bolting on angle is
Alternatively, consider changing from box store softwood to a locally
milled rough hardwood like oak or ash. The wood itself is stiffer and
you'll gain a little more stiffness from it being thicker (close to a
As I sse the problem with the angle idea is that when the ramp is loaded,
the bolts you use to secure the angle to the wood will want to twist in the
wood, ant that would as I see it be the start of a failure.
By using the steel on the underside as I suggested the sag would be limited
to the ability of the steel to streach against the unwillingness of the wood
to compress against the end grain like a wall stud.
You could induce a little preload when welding the rods to the end caps if
you flipped the ramp upside down and between two fulcrum points. If you
welded one end, and then placed a weight on the center the wood would flex
down, (Actually "up" in its usual orientation.) and then you could weld the
other end. When the weight was released, the rods would already be in
About the time I had mastered getting the toothpaste back in the tube, then
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