Estimating wooden ramp strength

[wfhabicher]

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 THE DEFLECTION.

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 capacity.

Wolfgang

[Mike Marlow]

Home Depot sells the ramp ends pretty cheap. They're in the Outdoor Garden department.

[Mike Marlow]

Why the "I" on the ramp? Especially at the ground end, it serves no purpose that I can see and only makes it harder to get things started up the ramp.

[Mike Marlow]

Holy Cow!!! Talk about over engineered! Three layers of 3/4" ply? Expensive and heavy.

And get a second truck to follow along and carry the ramps. But - no doubt they will be strong.

[J. Clarke]

The building codes for residential wooden structures do not in general specify allowable bending stress, they specify allowable deflection.

[Pete C.]

Probably about 60# each. Not that heavy really.

[Joseph Gwinn]

I think that Machinery's Handbook has strength and modulus data on wood.

One thing to consider is tipping due to an offcenter load, if the road surface is too soft and the ramp too narrow.

Joe Gwinn

[J. Clarke]

One thing to consider is tipping due to an offcenter load, if the > road

[Ned Simmons]

No question about that.

But there is stress in both the webs and flanges. With a little care in selecting the 2Xs you're unlikely to have a problem using them in tension or compression for the bottom and top plates. Any hidden defects, or overloading, are much more likely to cause a failure along the grain if they're subject to shear. The criss-cross grain of the plywood makes it the better choice for carrying the shear in the webs.

[Roger Shoaf]

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 roof straight.

[Jim Wilkins]

On Oct 25, 2:22 pm, Ignoramus20839 wrote: ...

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.

Jim W

[B A R R Y]

I have a set of those. They work fine with 2x8's getting my 500 pound wide cut mower in and out of my 4x4 Tacoma twice a year.

[Mike Marlow]

How did this get to be a couple thousand pound project? Wasn't the OP talking about such things as mowers and snowblowers? Who's going to be building ramps to load a couple thousand pound object into the back of a pickup?

Very heavy compared to the alternatives.

[B A R R Y]

I'd like to see the pickup with a couple thousand pounds in the back.

May the OP should just give up and hire a roll-back.

[Ignoramus7291]

I have a trailer that can carry a lot more than 2,000 lbs. I made it myself, kind of.

It can carry about 4k lbs.

i

[Lee Michaels]

"Ignoramus7291" wrote

After viewing your very impressive trailer build, I have two very irreverant thoughts.

The first is a mental picture of those crummy trailer kits sold at the borg and Harbor Freight. You know, the light weight trailers that come in two big cardboard boxes. Lots of pieces that you bolt together.

What you built is twenty times heavier, a hundred times more sturdy and million times more classy that those cheap kits.

The second thought is that cammo paint job looks really good on the trailer. When are you going to paint the truck to match the trailer?

[glyford]

I like this idea, though the earlier idea of bolting on angle is probably easier.

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 full 2").

--Glenn Lyford

[Ignoramus7291]

I bought one once. Sold it to my friend promptly. Could not stand the sight of it.

It is more like 10 times heavier. But yes. This is "the real thing".

I love the camo job, yes, and here's my dilemma. I feel like I need to sand and paint over some spots, but I do not know how to prevent the pattern.

This trailer actually gets compliments from completely random people on the streets.

Did you see the pictures of bullet holes on this trailer? (real bullet holes, not fake stickers)

Making it was fun. It was my winter project. It actually took relatively little time due to me wanting to get it out of the garage so as to not tp upset my wife too much. But it was as lot of work.

i

[Ignoramus7291]

I mean, how to keep the pattern, I do not know what I was thinking.

i

[Lee Michaels]

That information has to be around someplace. i have seen good cammo paint jobs done with spray paint (in a can).