Perry 951

Garrity Repta?


I agree with this 100%. I tossed my car off of 4 jack stands with no wheels on it. Thankfully I was out of the way in time. I thought it was very stable.. went to pull myself out from under the car and watched as the front 2 jackstands start to lean. I got the hell out of there, stood up to try to stop it from falling, and then it tipped over onto the ground. Almost put one of the stands through the drivers floor!

Be careful having a car that high. You need a bigger base for the lift portions to be on the floor.

Abby Normal

BE CAREFUL with that one...., reminds me of low crawling through mine fields!

david928

Good idea. This thread is great, because I've been thinking about the best way to raise the car since I bought it last November.

For now, I'm going to build a set of ramps as described on jorj7's 928 web site. They look very safe, stable, easy to use, cheap to build, and can be stored upright out of the way when not used. But they only raise the car 4.5 inches at the wheel. If I raise one end of the car with the ramps and use chocks, and jack up the other end onto jack stands, that will give enough room for most jobs. If I still need more height, then I'll look into building or buying some kind of lift.

Bill Ball

There goes one of your nine lives! You are one lucky dude. Me too, I guess. I've had mine up pretty high (22") on 4 jack stands doing things like the rear main seal. I have never liked being under there. My wife must be happy with my life insurance policy because she would not approve of me getting a decent lift.

AO

I agree with other comments about stability. It's all in the jack stand, and how it's loaded. I've been thinking of similar idea for a drive on lift that can be broken down and stored out of the way. I get the hibbe jeebies being under the car when it's on jack stands. Sometimes it's unavoidable though. Kudos for the effort!

Ron_H

I agree with Garth and Glen. At least 2 bolts per block to prevent twisting. You are using wood which lacks uniformity, can absorb oil, can possess hidden checks and faults. I would also place the longitudinal members transversely rather than longitudinally and jack the car from one end and then the other. Actually, I would lose the wood and find steel members. I agree with Dr. Bob, when he would do no more than change oil filters under this arrangement. Refine the concept using steel which has better and more uniformly predictable characteristics. You are in a low seismic risk area, but I would caution anyone in my area (zone 4) to not use this arrangement. In fact, I always leave one or two jacks in place as buffers when the car is on jack stands, and refuse to crawl under the car to check the transmission fluid level in my garage; I take it to Devek and sit comfortably in their waiting area.

hacker-pschorr

Ok, watching Monster Garage they always show up with a pickup bed full of steel 2x4's. Where do you get those? How strong are those (in a situations used as a jack pad) vs wood? I'm assuming the steel would be stronger eventhough it's not solid.

AO

I think I-beams would be better. But heavier. I think the whole idea is to have something light weight and strong.

Perhaps aluminum I-beams? You still need to figure out how to sabilize the jack stand though. Right now I think that's the weak link.

Thaddeus

Yes, it seems to me that the first time you start putting sideways force on the car (while torquing a bolt head, for example) you'd be running a riskk of having the thing shift sideways... and down. No car is worth dying under!

hacker-pschorr

I was thinking the same thing - not sure why a steel I beam would be heaver than a steel 2x4 with ouside dimentions being the same. Isn't the whole point of I beams their light weight? Or is that VS a solid steel beam?

Any way - for those trying to find a better jack stand solution, how about this. Take two steel 2x4's or 4x4's (or I beams) weld to them the jack pads designed for our cars. That way the car would be secure to the steel beam & would fit snug into the jack stands. If you wanted to get fancy, weld 1 or 2 cross braces (maybe even an X from corner to corner).

Just brainstorming.

EDIT - would the above setup be strong enough to jack up one side of the car by putting the jack in the middle of the steel beam between the two jack points? Or would it flex too much?

Ron_H

The steel 2x4s in this situation would be preferable to I beams because the purpose of an I section used as a beam is to concentrate the material where it is needed most: at the tension and compression faces. However it needs to be braced laterally to prevent lateral instability and rotation.
Since this application requires the member to exert axial tension and compression (only slightly, since the unibody of the vehicle already serves that function), a hollow circular section between both pads would be better suited because of higher polar moment of inertia. Weld a pad to each end of the center section to maintain relative dimensional stability.

FlyingDog

HP, look up metal shops or ask local welders. Some will only sell wholesale. Others will sell to anybody. They usually sell by the foot and either cut or let you cut to length on site (but may charge for it).

AO

Just out of curiosity... does anyone know the breaking strength of a Pressure treated 4x4? I know there's a lot of variability in these things, but this topic has my noodle going. I searched on google, but nothing jumped out at me. Any engineers or architects out there with a handy link for these kinds of specs?

deliriousga

Holy Cow!! Go to church, work in the yard a little and bammo, tons of questions. Please be patient, I’ll try and answer them all.

Garth S: 1) Yes, the through bolts act as locating pins. 2) You can try and jack from the mid-point of the side 4x4, but I think you’d get a see-saw effect so I wouldn’t recommend it. I jacked from 8”-12” from the lift points so I could place the stands directly underneath the lift points. 3) The cross member can’t be removed, but I drilled in 3 locations up and down the side beam so you can re-locate it depending on the job or add another if you want. I tried lifting it low without the cross member and it rocked badly. 4) The answer to the lifting question is at the end by itself. 5) Patentable? I got the idea from GlenL’s cross beam he uses. The problem for me with that one was it’s in the way for some projects so I wanted to try and figure out a way to lift it from the sides and be able to move the cross beam depending on the project.

jim morehouse: 1) Since the jack stands are under the wood and across the beam, the top of the stand sinks into the wood a little creating a cradle. The metal lift points on the car also sink into the top of the wood a little and the through bolts act as locator pins to keep the lift point from slipping off. With just stands, the lift points sitting on jack stands can slip off since there is no locking like there is with the Porsche jack and it is more difficult to get all 4 stands even without good jacking points outside the designated lift points where the stands have to go. 2) Since the cross beam has two shorter stands, each being 1’ outside the edge of the car, there is more side-to-side stability than just stands. I’ve grabbed every corner and yanked as hard as I can when it was lower and it doesn’t budge.

Thaddeus: None taken…when you see the plans it may help with seeing why it’s stable.

UKKid: The box on the right side is the receiver for the built-in Porsche factory radar detector. The PO lived in Virginia where they are illegal so it was disconnected. I hooked it back up and it’s pretty cool, just don’t know what bands it detects. I bought a new one and I’ll have them both on when I get her back on the road to see what bands they pick up.

Greggles: You can’t raise it from the cross member. You will get a see-saw effect…very dangerous. The only lifting on the cross member is a tiny bit to allow the two outside stands to be placed under it for side-to-side stability. Height to the oil pan is 22 ½”. Can be higher, but I’d recommend wider stands for that.

Scotsman: You could use a 2x4, but I wanted more height and also wanted more distance from the cross beam to the bottom of the car for possible future jobs where I would need that room. Lifting answer is at the end of the post.

OrionKhan: Lifting answer is at the end of the post.

Fst951: Wish I had a rotary lift. Sure would be nice, but not feasible right now. Some day….

dr bob: I have to get me a set of those wide base stands. I’ve placed two jack stands outside the normal 4 lifting points to give it 6 points to help with sway/tipping. I’m also putting my two rolling jacks under the front end just in case. That way if anything does happen, the rolling jacks will move with the car and keep the front end up. I like the idea of spacers below the stands. I’m keeping it up for a week and checking each night before I do anything underneath.

PorKen: If you come up with something made of steel please post it. I’d rather have that, but not proficient with that kind of stuff. You might want to look at something that can cradle all 4 wheels at a good height so the undercarriage is completely open. Great except for the tranny when you might need to take the weight off the rear wheels.

GlenL: I realize the pressure treating isn’t for strength, just can’t find non-pressure treated around here. Sure would be nice though for weight. The wood should be fine since the only load bearing is directly under the lift points. Also, there is more than the ½” square areas that make contact. Since I used 4x4s with rounded edges, the whole top of the stand cradles the width of the 4x4. I’ll try and get a picture of it. There are no places in the middle of the beams where it is holding the load, just extra stands for stability there. I’m hoping someone has an idea with what type of steel would be best to use instead and also where you might be able to get it. My brother-in-law is a mechanical engineer as well and I’m going to invite him over for dinner one evening and get him to look everything over.

Perry951: I’m looking into dr bob’s fat stands. I definitely like the idea of wider bottoms (hmmmm, reminds me of a Queen song).

david928: I’ll have to check out the ramps you’re talking about. I saw some wide blocks w/ chocks that were wide and about 2’ high for the wheels to sit in, but can’t find it. I really like that idea since it leaves everything wide open underneath.

RonH: That’s one thing we never think about here…seismic activity. In my 38 years we had a little tremble once in the middle of the night. The wife (after living in CA a few years as a teen) said “that felt like a tremor” to which we all said “yeah, right, in GA?” That’s all everyone talked about the next day. I wouldn’t use anything but a locking lift over there. I didn’t think about twisting on the lift points since all of the weight is directly under the lift points. I’ll add another bolt at one of the ends to alleviate that.

Lifting Sequence: I used two floor jacks to lift the sides evenly. The jacking sequence I used was to jack the front up and put the tires on ramps (unless you can get yours on ramps without ripping off the spoiler, I can’t). Next I put the two side members down and attached the cross member where I wanted it. Then I lined up the front lift points and jacked it up enough to get it on the lowest setting on the jack stands (lifted from 8”-12” inside the lift points). Next, I lined up the back lift points and jacked it up enough to get the back on the lowest setting on the jack stands. Next I lifted the driver’s side enough to move the jack stands up 2-3 clicks and then did the same on the passenger’s side. I did that again to lift it to the final height and used a level on both sides and the cross beam to make sure everything was kosher. In the end, I had to re-lift one corner and adjust one stand that ended up about ¼” out of vertical. After it was all good, I set the two lower stands to as close to the height of the cross beam as possible. They were about 1/16” higher than the bottom of the cross beam so I lifted it slightly to slide the stand underneath.

Final thoughts, well, maybe not so final...I like the steel idea if it can be done at a decent price so I can get approval. As soon as I have an extra grand, I'll be picking up one of those low-height (36" or 48") lifts. Since buying the 928 I've put $2K in parts in her (not a surprise, I expected it from the PO), not to mention the wife's Boxster which will hit the 60K mile mark soon and have $1K in maintenance if I do it, so the cost of a lift is out at the moment. Oh, and I forgot to mention the most expensive car we've ever owned, the Dodge Intrepid.

borland

Engineer chiming in.....

That lift with with only two floor jacks looks like a nice balancing act. Once you get the car on the four jackstands it will be safe to crawl under, but if those front to rear beams fail during the lift, you car is toast. Wood is very brittle under tension, and ductile under compression. So no dry rotted, pine, or balsa.

My 6 ton jackstands provide 24" of lift. For transmission or torque tube work, blocking the front tires with wooden blocks and using the 6 ton stands on the rear works fine........and you only need one floor jack.