DIY Work Ramps

[808muscle]

And safer! All my Corvette buddies use mine now. Lol

 

[GTOdude]

I wound up getting lazy and got a set of the Rhino extreme ramps.. Local parts shop gave 'em to me for a great deal and they work great.

 

[Darin]

Someone posted a while back (last year maybe) about some mega ramps they made. Used 2x10s I think, pegs, slots, and made them drive up for all four wheels and then you could take off the ramp parts and just leave the car up on all four corners. Was pretty big set up, but hella nice. I can't find the thread though. Anyone remember which one I am talking about?

Not exactly what you are talking about but I made these years ago. Once I drive it up and chock the rear wheels I take the "ramp" out and it makes it much easier to be able to have side access. Notice the first of the 5 boards is longer it's a must for lowered cars.

 

[01bluesnake]

Those are pretty nice ramps, need to make me something like those. I just use 2x10 boards and usually works out enough to get a jack under.

 

[Thekid760]

Not exactly what you are talking about but I made these years ago. Once I drive it up and chock the rear wheels I take the "ramp" out and it makes it much easier to be able to have side access. Notice the first of the 5 boards is longer it's a must for lowered cars.

Awesome! I had the same idea as far as cutting and stacking 2x12, but I didn't think about making them 2-piece or adding a wheel chock.


Misspelling courtesy of my fat fingers...

 

[Thekid760]

If anyone is concerned about weight capacity (why would you be?) my Father uses this exact setup to level his 35 foot motor home.

I know or at least highly doubt anyone is truly concerned about the weight capacity, but I'm bored at work so I tweaked a bit...

Some facts:

- Perpendicular compressive strength of southern pine is 565 psi, but we use 500 at work for a small safety factor.
- Based on my Nitto NT555 275/40/18 @ 36.75 psi it has a contact patch of 10.48 wide by 6.46 length giving it an area of 67.7 (call it 68) square inches each tire.

68*500 = 34,000 lbs per tire.

or the exact gnats ass:

67.7*565 = 38,250.5 lbs per tire.









Sources for tire contact patch and lumber strength:

http://bndtechsource.ucoz.com/index/tire_data_calculator/0-20

http://www.southernpine.com/using-southern-pine_design-values-qa.asp

 

[Wes06]

in other words, put all the weight you want from any vehicle you could own, and a stack of wood in this design can hold it

 

[Norm Peterson]

Be careful.

That analysis works for a solid stack of wooden planks, but not when the wheel is sitting over a "window" underneath the top plank as shown here. . . for this situation you need to work with allowable bending stress. You'd also need to know the length of the window and the dimensions of the plank before you could calculate backward to find the maximum allowable wheel load. This bending stress calculation is somewhat more involved than load divided by area.

I don't want people thinking it's too easy to do this stuff or that safety margins are always going to be as high as 38000 lbs allowable divided by 1000 lbs or so actual.

Thanks for the links. Kind of early in the day, but


Norm

 

[Wes06]

has a point on the shown ramps, if I were to build that set I would have a hollowed out section to reduce weight, but have a few pieces a few inches wide through the middle, prevent the wood bending and transfering weight directly down

 

[Thekid760]

Norm,

Your absolutely right (as usual, I enjoy your input). My mistake I didn't clarify, I was replying to the earlier quote about strength which was referencing the original design of solid members.

If I get bored later I might take a stab at calculating it out, but I'm a bit of a moron so I might screw it up, just so you are all forewarned not to take my numbers as gospel

Those links I found in google, but I really like that contact patch one, it seems fairly accurate assuming you have correct input numbers.

And cheers to you as well, it's 5'oclock somewhere. If only I wasn't stuck at work for a few days...


Misspelling courtesy of my fat fingers...

 

[Darin]

Those concerned about the weight on my design I have had by friends F350 dually on those ramps, front and rear wheels. All pieces assembled are glued and screwed.

I had a chock for the tire that the pegs held in but they recenlty got misplaced.

I will be making another set soon that will be 3" taller. That design is ok for oil changes but anything else and it's a little cramped under there.

 

[Norm Peterson]

Darin - I like the disassembly option.

Question: are the two screws that hold the pieces together threaded into the lower plank or do they just drop into clearance holes?


Norm

 

[19COBRA93]

I don't know if some of you have had problems with your ramps wanting to slide forward as you're trying to pull up on them, but I have. My garage floor is the typical very smooth garage cement. So I drilled a couple holes through the ramps into the cement floor to help lock in the ramps so they never move when I'm pulling up on them. Each ramp has an exact location marked on the floor so I know exactly where to place them. The drilled holes are all slightly larger than the 4.6L main bolts I drop into them (I had them laying around). It's a very inexpensive but effective way of getting a lowered car up in the air quickly.

In this pic you can barely see the bolt head just below the 3rd tier. These were made from 2x12's.

 

[zquez]

I might have to make some of these to get the car on the lift. Its such a pain to jack the car up just to get the damn arms underneath

 

[Darin]

Darin - I like the disassembly option.

Question: are the two screws that hold the pieces together threaded into the lower plank or do they just drop into clearance holes?


Norm

They are bolts I cut the threads off so they just drop in a hole 1 drill bit size larger than the bolt.

My solution for ramps that want to slide on you is the longer 1st board so the tire isn't immediately trying to roll up the whole ramp and if you still have trouble make the floor dirty under the ramp.... a few grains of dirt or sand always works for me.

 

[Thekid760]

Norm I'll prob need a little help here, because I'm not sure if I'm doing it right.

I attempted to calculate the load rating of the open center type ramps.

I found this document on how to calculate loads for scaffolding using different types of wood. Southern pine is what we typically use at work for our wood ratings since it is common. The way the ramp was designed uses the same principles as scaffolding, but scaffolding tends to use dynamic vs static, so I am unsure how that will effect the numbers.

http://www.fpl.fs.fed.us/documnts/fpltn/fpltn-264.pdf

And yes it is an old document, but its somewhere to start.

The formula used to calculate concentrated safe loads for scaffolding is as follows:

P=[2W(T squared)F] / 3L

P is the safe load in pounds (I'm assuming in lbs per sq inch as most wood is rated).
W is the actual width of plank in inches
T is the actual thickness of plank in inches.
F is the safe working stress in bending, in lbs per square inch.
L is the span between the supports, in inches.

I assumed a few variables here. The wood used is a 2x12. The span is 12". The wood is southern long leaf pine with a 15% moisture content.

Lets plug some numbers in so we can get the calculator out:
W = 11.25"
T = 1.5"
F = 102
L = 12"

P = (2*11.25*2.25*102) / (3*12)
P = 143.43 lbs per square inch
Contact area = 67.7 square inches per tire
143.43*67.7 = 9710.211 lbs per ramp.

Now lets go worst case scenario.

Variables used: The wood used is a 2x10. The span is 12". The wood is Western Red Cedar with a 15% moisture content, the lowest rated wood in that document.

P = (2*9.25*2.25*60) / (3*12)
P = 69.375 lbs per square inch
Contact area = 67.7 square inches per tire.
69.375*67.7 = 4696.6875 lbs per ramp.


I assumes a lot of variables, and also ASSumed the P was lbs per square inch.















What happened? I blacked out...

 

[BlueSoulStang]

Straight up gangsta. Haha. Easy does it.

 

[onehotpny]

Made these ramps last week , had some 6x6's laying around, so i did the layout and cut them, worked for what I needed. will be making an improved version in the next couple of weeks, once I do I'll post pics of it.

 

[B2B]

I noticed only a handful of ramps shown here have enough room for a wheel choke. If you put the front of the car up on the ramps, keep in mind that the taller the ramps, the more likely the car is going to roll back on you when you jack up the rear of the car.

If you are making a pair of ramps, leave some length on the top shelf for some kind of wheel choke. It doesn't needs a lot, but there should be something there to keep the tires from rolling.

 

[Norm Peterson]

I always chock one of the wheels that is still on the ground. Sometimes both of them. More than once I've forgotten about the chocks and tried to drive over them coming down off the ramps. Cuss a little, drive back up a tad, remove chocks, try again..


Norm