So, I occasionally have a need to move unpowered vehicles in and out of my garage.
The garage is relatively flat, while the driveway is sloped at 1.5-2″ over 12″ or 7-9 degrees (upwards towards the garage).
My idea was to make a large plate, maybe a foot deep by 2-3′ wide of .375″ or .5″ mild steel, which would be anchored to the concrete with probably 6 anchors and mount a winch to it.
I don’t know the thickness of the concrete — google says 4-6″ is common for garage pours, assume the worst case of 4″.
Is side-loading the concrete in this way such a bad idea as to not be worth pursuing? Is there a way to make it safe, like with a larger plate (longer along the axis of pull)?
Secondary question, how much of a safety factor should I consider for the winch? I.e. if the largest vehicle I’d yoink up there is around 5k lbs, knowing that it’s not being pulled vertically and is on wheels, is something like a 2k trailer winch sufficient?
How would you accomplish this?
Comments
For winch capacity, understand you won’t need a huge winch in the same way you can push a car with your chevrolegs. I bet you could crank that thing with a pulley and a 24” cheater bar tbh. But I digress. Point is winch capacity is fine, just get a cheap 1 ton.
Second thing I wanted to mention is it seems like your plate is way bigger than it needs to be. Check for access when deciding on where you’re putting your boreholes but otherwise minimize that steel and go make a knife with the rest.
Lastly, your concrete will react to you pulling on it like a tame horse carries a rider. It’ll think it’s wearing a hat or something but otherwise be unbothered.
4x 1/2” concrete anchors. Drill your bore holes for your plate oversized for tolerance.
Place the plate down without the winch, after the bore holes. Bang or drill a starter mark through the holes to mark locations in the concrete.
on the bottom side I’d countersink some flat head screws and drop the winch onto the upright bolts. This will allow your plate to lay flat.
Mount winch, place assembly aside. Drill concrete anchor bores, insert anchor, tighten to expand.
Grab assembly and see how high you can drop it from while still passing all through holes down the shanks of the anchors.
Get some Fat washers and go to install the anchor nut.
Realize you can’t turn the nut with an impact from the top because the winch body is in the way and-
A, be mad you didn’t save that extra steel you used to make a knife; or
B, turn that bitch with a wrench and contemplate your self worth for the extra 20m it took to tighten them down.
After your done, kick it to make sure “it ain’t going nowhere”
Finally- to answer your actual question, the “side load” will be translated as a torque at the winch, but luckily the distance from rotation axis is minimal, giving a tension load on your winch mounting bolts. The anchor bolts will look up to the smaller winch bolts and give an encouraging “you got this buddy!” While they are cozy in their concrete coffin.
You got nothing to worry about
Searching for “LDT tapcon shear capacity” will get you performance tables with ultimate shear loads. They recommend a safety factor of 4. They’re quite specific about embedment depth, edge distances, and required spacing between the fasteners.
I’d be sure to understand exactly how the slab you’ll be pulling on is anchored–slabs vary from “never going to move” like a monopour with rebar continuous to a thick footer, to “surprisingly easy to move” like a splash of concrete over dirt and anchored to nothing.
Non engineer here, so use that grain of rice people talk about:
If I were to do this: I don’t think the side loading is a big deal if you have at least 4″ of good concrete, and I would epoxy studs into the concrete instead of expansion anchors. Probably this plate. I would use a hoist/winch combo so that it can be hooked to the anchor plate on the floor when needed, and removed when not needed. Something like This .
Use 3- 1/2″ coarse threaded rods embedded at least 3″ into the concrete with Sika AnchorFix-2 adhesive. Follow the instructions and make sure to use compressed air to blow dust out of the holes before putting the adhesive in (this is often not done and causes a lot of problems). Sika AnchorFix is available at Home Depot. Allow it to cure fully before installing the anchor plate, after you install the plate torque the nuts to 15 ft-lbs (no more). If you over-torque the nuts it will break out a cone of concrete well before the epoxy fails. That anchor system will hold a 2k winch no problem.
I would design the plate in such a way that any pulling up on the back is countered by the plate pushing down on the front. Add a diagonal cross brace from the pillar to the front of the plate. You could even add a counterweight on the back of the winch to help balance the load.
I don’t think it has been mentioned but garage slabs are commonly pre or post-tensioned. Meaning there are tendons in the concrete under high load which you must be mindful of when drilling anchor holes. Cutting tendons could cause them to fail in a somewhat violent fashion; it would likely damage the slab as well when it does. Idk exactly how dangerous for the installer that failure would be, but I’ll tell you I wouldn’t want to be anywhere nearby. Maybe I’m a chicken.
Tensioned slabs are often stamped as such, or you can sometimes find the tendons on the exposed sides of the slab.
I’m curious if you don’t mind, what is “side loading” a concrete slab?