The Rodding Roundtable
Motorhead Message Central => Rodder's Roundtable => Topic started by: 50 F1 on November 10, 2019, 06:28:43 AM
I have seen quite a few times on the automotive shows on TV where the shops are using stands that they have built up out of 2x4's under each wheel. Built up like cribbing the house movers and riggers use.
Does anyone here use these?
Do you think they are safe? One show had the stands under the wheels and also had jack stands.
I have a scissor lift and a lift that you drive on and jack the back up and swing the rear legs down. (don't want to use the names) They are both a pain in the back side sometimes. Gotta get rid of both of them and get a hoist.
Mike
I have often thought of making some of these myself but I did not feel comfortable about the safety factor until I had more information.
Maybe we will get some input, or at least someone will make some, and slid under a car to test them.
I've used cribbing to support cars. Before I built my stands I wondered about it some. Once I started using them I stopped worrying pretty quickly as they never showed any sign of strain. Zero signs of crushing, cracking, bending, never made a squeak when I put weight on them and they feel solid as a rock when I shake or bounce on the car. Mine are 12" square 9 layers of 2x4 high. The corners are fastened with 2 nails each. Each layer except for the bottom (second?) one uses nails long enough to extend all the way through the one below, slightly into the second one down.
At 12" on a side, 7" of that is supported by wood directly below. That leaves a span of only 5", not a lot. You're also on a base which is quite a bit wider than a typical jackstand. Wood is certainly going to compress some with weight, but that's spread all the way down 4 columns of 3.5x3.5x4, or 49 square inches. That's enough to carry a good bit of load.
This topic got me curious enough to do a little research about cribbing. I found a FEMA source which said lumber bearing a load across the grain will start to make cracking sounds as a warning of impending overload at 500-1,000 psi. That's a minimum of 24,500# at 49 square inches of bearing area. They encourage incorporating crossgrain loading within part of a temporary support structure specifically to create that warning.
I think it's safe to put a car on cribbing.
I have a set I made some years ago made of two by sixes. basically a two by six square with more two by sixes on top, and built in chocks to keep the wheels from rolling. I'll see if I can get a picture today.
I have spent many hours under stuff sitting on plywood wheels.
I'd like to see some pics
Quote from: "jaybee"I've used cribbing to support cars. Before I built my stands I wondered about it some. Once I started using them I stopped worrying pretty quickly as they never showed any sign of strain. Zero signs of crushing, cracking, bending, never made a squeak when I put weight on them and they feel solid as a rock when I shake or bounce on the car. Mine are 12" square 9 layers of 2x4 high. The corners are fastened with 2 nails each. Each layer except for the bottom (second?) one uses nails long enough to extend all the way through the one below, slightly into the second one down.
At 12" on a side, 7" of that is supported by wood directly below. That leaves a span of only 5", not a lot. You're also on a base which is quite a bit wider than a typical jackstand. Wood is certainly going to compress some with weight, but that's spread all the way down 4 columns of 3.5x3.5x4, or 49 square inches. That's enough to carry a good bit of load.
This topic got me curious enough to do a little research about cribbing. I found a FEMA source which said lumber bearing a load across the grain will start to make cracking sounds as a warning of impending overload at 500-1,000 psi. That's a minimum of 24,500# at 49 square inches of bearing area. They encourage incorporating crossgrain loading within part of a temporary support structure specifically to create that warning.
I think it's safe to put a car on cribbing.
^ I made 12" cubes out of 2x12
Finally built some of these. I spent about 3 hours under my car and I'm still alive. I like them.
Mike
here are mine
I haven't enough jacks to get a car's wheels that high off the ground. I'd have to make something to raise my floor jack up. That's also out of the range of the bifocals in my glasses. I seem to be getting old faster than you guys are. GPster
I have a set of 4 that look more or less just like Frank's. The fronts are 7-1/2" wide and the rears are 9-1/2". They have a block front and rear. Later on I made a 1-1/2' riser to nest on the top with a block on each end of those. The bases are little over 10" and with the rise rthey are about 11-3/4". Each unit is 24" long.
I've been using these for 25 years or more with never a problem. The heaviest thing I've had on them is my 2017 Grand Cherokee which probably weighs in around 2-1/2 tons.
The cribbing ones shown also look more than tough enough.
The other day I bought a used set of Quick Jacks that will lift up to 7000 pounds around 20". I'm looking forward to the ease of that process.
Quote from: "Charlie Chops 1940"I have a set of 4 that look more or less just like Frank's. The fronts are 7-1/2" wide and the rears are 9-1/2". They have a block front and rear. Later on I made a 1-1/2' riser to nest on the top with a block on each end of those. The bases are little over 10" and with the rise rthey are about 11-3/4". Each unit is 24" long.
I've been using these for 25 years or more with never a problem. The heaviest thing I've had on them is my 2017 Grand Cherokee which probably weighs in around 2-1/2 tons.
The cribbing ones shown also look more than tough enough.
The other day I bought a used set of Quick Jacks that will lift up to 7000 pounds around 20". I'm looking forward to the ease of that process.
I'd quite enjoy a set of Quick Jacks.