Yes
I did not paint lines on the floor, but I do have tape on the floor for that purpose.
Thanks for the confirmation of the logic.
Vehicle Lifts: 2-post, 4-post, etc
- Thread starter Waorani
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Yes
I did not paint lines on the floor, but I do have tape on the floor for that purpose.
Thanks for the confirmation of the logic.
ccasteel
SILVER Star
The 2 post would definitely make several jobs easier. But I went with the 4 post because of space I always have something stored on it. It's more stable. Also, I like the ability to move the lift around. It's not bolted down which makes it not quite as solid as it could be, but my needs frequently change so I couldn't commit to one place. Mine's an older Danmark. The went out of business a couple years ago. Thankfully Bendpak took over the name and I can still get parts.
All that said, I'm having a problem with the return hose blowing off. Hopefully someone here can point me in the right direction. As the lift gets close to the top it starts to struggle and if I'm not watching closely the hose will blow off making a huge mess. The pressure in the cylinder isn't released because the lift doesn't begin going down. But then it's not going anywhere until I get a new connector. Any ideas as to what could be causing this and how to fix it. I have had it about 12 years and this just started about 3 months ago.
All that said, I'm having a problem with the return hose blowing off. Hopefully someone here can point me in the right direction. As the lift gets close to the top it starts to struggle and if I'm not watching closely the hose will blow off making a huge mess. The pressure in the cylinder isn't released because the lift doesn't begin going down. But then it's not going anywhere until I get a new connector. Any ideas as to what could be causing this and how to fix it. I have had it about 12 years and this just started about 3 months ago.
What's the general consensus on the thickness of concrete needed for a two post lift?
I have a large three car garage that could fit a lift - 13' ceiling - but I didn't build it and need to figure out how thick my slab is.
I have a large three car garage that could fit a lift - 13' ceiling - but I didn't build it and need to figure out how thick my slab is.
Malleus
Far west of Siegen
Is this an air line or hydraulic line? I assume air, because that looks like a pushlok fitting. I used to design pneumatic/hydraulic systems; I wouldn't trust a pushlok on anything that I needed to depend on, like a suspended load. If the fitting is original to the build, I'd just replace it (and all the others) with a screw type fitting.
Malleus
Far west of Siegen
It depends on what the compressive strength of your concrete is; there's no way to tell for sure, without coring a part of it and sending it to a testing lab. I'd personally doubt it was better than 2500 pound concrete, though. And probably less than 4 inches on average, at that. Worse, the base probably wasn't compacted, prior to placing the concrete.
All that means that you really need to do some preparation before you install the lift. If it was me, I'd cut a 12x12-inch square out of the floor, everywhere I was going to set the foot of the lift, oriented with the corners pointed in the direction of the entry/exit to the lift. Then, I'd excavate 12 inches down, place 6 inches of well compacted #72 aggregate, in at least two lifts, and then place minimum 4000 pound concrete in the hole, after I lined the sides with expansion material to isolate the pier. If you asked a structural engineer the question, that's the answer you'd get.
Having said that, I'm willing to bet you could find an unlimited number of people who haven't done any of that, and who'll swear there's nothing wrong with their floors or their lifts.
My personal preference would not be a post lift, although I know that's the current fashion. I favor the scissor type lifts, with the sliding scissor trays. You can drive on, without fiddling with arms, you have a place for tools and parts while you're working, and you can get the wheels off the ramps with the sliding trays. All this and the load is spread out over a larger area, so concrete strength cannot be a problem. Plus, if you prepared ahead of time, you can sink it into the floor, making it essentially flat all over the floor area (OK, the middle area is still non-skateboardable, but you can't have everything). If anyone has one for sale, I'm in the market
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Lift manufacturers all have very clear published concrete and anchoring specs.
If your concrete does not meet spec they also have very clearly laid out remedies so you can still install one.
To test, you drill a hole through. You can tell exactly where you break through a slab with a hammer drill. A long 3/8 bit is a good size to test.
2500 psi concrete is not used in flatwork. You cannot finish concrete without atleast enough cement to make it 3500 psi. Most every slab is poured from 5k mix.
If your slab is too thin for a 2 post the remedy Rotary promotes is to cut about 3' x 4' under each post. Dig down a foot. Dig under the slab a few inches each side. Drill into sides of old slab. Epoxy in rebar. Tie your rebar grid to that. Pour new 12" thick slab and vibe well to ensure mud flows under old slab.
Not a big deal.
WarDamnEagle
SILVER Star
Pretty sure that’s not the answer you would get. That’s way too small.
@PIP is spot on with his reply.
- Thread starter
- #49
By "making a huge mess" I assume you mean hydraulic fluid? And now that I look closer, I can see what looks like fluid dripping. But like mentioned above, that looks like an air line fitting. There are "push-lock" hydraulic fittings but none that I've seen like that. Count yourself lucky if you've gotten by this far.
edit - looks like BendPak/Danmar does use the same tubing/fittings for air and return hydraulic fluid. Return is not under as high a pressure as lift but that still seems odd. Minimally I'd replace lines/fittings with new but if it were mine I'd plumb return with actual hydraulic hose.
edit - looks like BendPak/Danmar does use the same tubing/fittings for air and return hydraulic fluid. Return is not under as high a pressure as lift but that still seems odd. Minimally I'd replace lines/fittings with new but if it were mine I'd plumb return with actual hydraulic hose.
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Malleus
Far west of Siegen
It's the answer you just got from a structural engineer. A 3x4 foot pier will certainly work, but you'd loose your job if you spec'd that for a homeowner customer. And, 2500 psi concrete is all that's used for non-commercial flatwork in the south, unless the engineer specifies something greater. You'd have to bribe someone to ship 5000 pound concrete around here.
Manufacturers routinely overspecify requirements in order to prevent lawsuits. Building piers in a parking garage, for example are typically 3x3 foot square, and several yards apart, and they're holding the whole thing up.
The west coast has earthquake requirements that no other area, outside Hawaii and Chicago have.
You bring up a good point and I think you touch on what his problem is- His lift has a single acting hydraulic cylinder. The hose that's blowing off is a vent line, not a return. The reason it's blowing off could be the piston seal is leaking, overpressurizing the vent tubing.
Do they rate it differently somehow? I've done a lot of concrete. I've used 3500 mix for a slab and it was a mf'r to finish with so little cement in it- No cream on top. The concrete all costs the same here. I can spec 5k with 1" rock and its the same price as 2500 psi with 3/4" rock. The batch plant doesn't care if you want 50 cents more cement in the truck.
- Thread starter
- #54
That was my first thought too but BendPak calls it a "return line" in their instructions so I went addle brain for a minute. Seals need to be replaced.
Installing the Return Line
The Return Line takes excess Hydraulic Fluid coming out of the Hydraulic Cylinder and sends it back
into the Fluid Reservoir on the Power Unit.
The Return Line is a single piece of ¼ inch, black, polyethylene Tubing with Elbow Compression
Fittings on each end. You need to cut off a piece of the supplied Tubing of the right length to create
the Return Line.
Important: The Return Line uses the same ¼ inch, black, polyethylene Tubing as the Air Lines. Be
sure not to confuse the two; the Return Line and the Air Lines do completely different
things and
must be kept separate from each other
WarDamnEagle
SILVER Star
I am not a structural engineer but I am an engineer, married to a CE and have a Son In law with a Masters in Structural Engineering. Lots of concrete and rebar discussions around our house.
But since you’re the expert; I have a Rotary SPOA10. The baseplates are larger than 12” x 12” And the anchor bolts are obviously on the edge. If for no other reason than those dimensions your advised solution wouldn’t work. And even if it would fit dimensionally, I frankly don’t believe it is safe to only have 1/2 ft3 of concrete under each post. Are you sure you’re fine with that recommendation? Remember the question was about 2 post lifts, not 4 post.
It’s a good question, I would be surprised if it’s rated differently. Guessing we can get away with lower psi due to no freeze concerns? I just installed a 3500psi slab w fiber mesh in my back yard for my shop, so it’s easy to exceed that 2500 standard as you’ve mentioned. The slab was 4” but I added a 6” section approx 2’x15’ to accommodate a 2 post lift. Turndown footer is 18”dx22”w per city of PHX spec. Spent a few years estimating for a concrete contractor here in the valley.
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Hard to find anything definitive on it, but I did run across this discussion- https://www.eng-tips.com/viewthread.cfm?qid=428355
It sounds like concrete psi norms vary by location.
Here in Oregon it's hard to order anything under 4000 psi mix. The plants will actually try to talk you out of it.
I believe the answer would be here: 318-11 Building Code Requirements for Structural Concrete And - https://docslib.org/doc/9743357/318-11-building-code-requirements-for-structural-concrete-and
My engineered plans referenced ACI 318-11. Full disclosure.. I didn't read the whole thing. =)
Malleus
Far west of Siegen
That's not surprising at all, considering the building standards on the west coast. FWIW, the construction industry is highly regional. Ready mix plants produce what is most commonly ordered, without regard to the intended use. It's just too difficult to run a plant of any size efficiently (and ensure quality) when you're changing mix recipes often.
There's another thing to consider: commercial and industrial construction bonds and licensed engineering specifications often require construction material testing. If the mix doesn't meet the specs, the plant pays for it. Around here, residential mixes are never tested, regardless of the mix strength. I've never worked in construction outside the southeast (well, there was a job in Montreal, but I don't count that one), but I've been told by colleagues that their experiences, with the exception of the west coast, are similar to mine.
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Malleus
Far west of Siegen
Yes, every concrete question can be answered by reading 318...but not without a lot of work. And 318 doesn't cover practice standards, just minimums.
I had a professor (actually he was the chair of the department and my advisor) who laughed at the practice of allowing formula cheat sheets for tests. Someone once asked him what he'd allow on a cheat sheet for an upcoming test and he wrote F=MA on the board. He said that was the only formula a good engineer needed. While being technically correct, it wasn't in the least helpful for the heat transfer mid-term we were reviewing.
