Lets talk shear vs tension...

So, I have been wanting to make a pull up bar from pipe fittings, kinda like this:

And I am just about ready to get started, but I'm worried...I will be building mine in the basement, hanging between the joists of the first floor, and my anchors will need to be in shear, just like the photo.

I know that putting fasteners in a shear configuration is typically a no-no, but was curious if it's ok when you have an abundance of them? If each mounting flange has 4 screws, and I will have 2 flanges, for 8 total anchor screws, is that qty enough to purge the sin of shear mounting? I'm trying to avoid a catastrophic failure leading to me in a pile on the concrete floor.

Is my other option adding some 2x8 bridging between the joists that I can use to mount the anchors in tenstion? I'm worried about that too, because then I have to think about making sure the 2x8s can take my weight, as they too will be in shear.

Am I over thinking it? What says the hive?

You won't shear those screws off, not unless you're about 1000lbs.

The more likely scenario is the constant side/shear load on the screws will cause the holes in the timber to elongate over time. If you'd rather be safe, use bolts and a backing plate or washers on the reverse side of the 2x8.

I don't like the length that one hangs down. Not worried about the shear from pulling down, but the constant back and forward motion on that bar during pullups could tear up the wood pretty quick.

Mine is just a bar with two holes screwed directly to the rafters above with 3.5 inch wood screws in tension.

No engineering thought in it, but it works for me and it was quick.

When these are $42 delivered... I wouldn't build from pipe that isn't made to support you.

Linky

But if you do it, use through bolts and washers and locate them in the middle of the joist or higher.

In reply to OHSCrifle:

Yup, lag bolts are the answer.

Bolts that are loaded in shear are undertightened

I agree, through bolts, then don't worry about it. That should be sufficient overkill.

OHSCrifle wrote: When these are $42 delivered... I wouldn't build from pipe that isn't made to support you. Linky But if you do it, use through bolts and washers and locate them in the middle of the joist or higher.

Ive seen these, and I like them, but I need my bar running perpendicular to the joists because of space reasons.

I think Im going to go with bolts and washers. I dont know why I hadnt thought of that before!

Thanks guys!

I can guarantee that the iron pipe will be stronger than the premade pull up bar!

Bolts are a good idea. You'll have a lot of side to side forces on that thing.

Just to clarify: bolts that see a shearing force in their threaded portion are a big no-no.

If you use a bolt thru the wood beams with the nut on the opposite side of the pipe flange, it's fine.

In reply to dculberson:

SCH40 steel gas/water pipe itself is pretty strong stuff, the threaded connections with sharp grooves that cut more or less halfway through the pipe are not.

In reply to BrokenYugo:

Yes, but the threaded male portion of one section interlocks with the threaded female portion of another section, so the material loss in cutting the threads is abated...or so it seems to me.

All you guys worried about the strength of the pipe - we're talking about a pretty light load on a 1" pipe. It's not like he's planning to use it to pull an engine.

I just built a pull-up bar for my wife. Built it out of a piece of 1" pipe with floor flanges on the ends. I welded two arms on each end so it's got a wide footprint and the fore-aft strength needed for horsing around on a TRX. I was trying to figure out how to build it out of various Home Depot pipe parts, then realized I have a welder It's attached with 8 5/16" lag bolts that are in tension. I think we'll be good.

Keith Tanner wrote: All you guys worried about the strength of the pipe - we're talking about a pretty light load on a 1" pipe. It's not like he's planning to use it to pull an engine.

I made the upper link for my rear suspension out of galvanized threaded pipe. Butt welded it to some old bushing holders, right on the threads. Then sliced it apart a couple times to adjust the length. Everything else around it broke but the pipe was fine. (Welding it was fun. No matter how much I cleaned it off, it was "fumey". Hold breath while welding and walk away to fresh air before inhaling)

More recently, my harness bar is also 1" galvanized pipe, as are the tire racks on my trailer. Everything else around them will break before the pipes will.

Oh, and my steering wheel also has a section of pipe welded into it. The threaded portion was the perfect taper to sit in the base of the wheel

captdownshift wrote: In reply to OHSCrifle: Yup, lag bolts are the answer.

Through-bolts !=! lag bolts.

In reply to Knurled:

Dip galvanized, zinc, cadmium or any plated steel in muriatic acid before welding, a quick rinse w/ water will neutralize any remaining acid. Stand upwind tho as the fumes are pretty nasty. Welds clean after that.

Actually a great weld prep for rusty metal also, especially TIG, digs deep into the pores.

BrokenYugo wrote: In reply to dculberson: SCH40 steel gas/water pipe itself is pretty strong stuff, the threaded connections with sharp grooves that cut more or less halfway through the pipe are not.

With a wall thickness of .133 inches, a 1" steel pipe can be cut into a lot more than 50% and still be stronger than the paper thin steel they make stuff like pull-up bars out of.

... and then there's always Schedule 80

dculberson wrote:

BrokenYugo wrote: In reply to dculberson: SCH40 steel gas/water pipe itself is pretty strong stuff, the threaded connections with sharp grooves that cut more or less halfway through the pipe are not.

With a wall thickness of .133 inches, a 1" steel pipe can be cut into a lot more than 50% and still be stronger than the paper thin steel they make stuff like pull-up bars out of.

Yeah, I'm thinking here of mountain bike handlebars that were .025" aluminum or something. Needed to put reinforcements in the ends if you wanted to stick barends on them. Replace them every year if you wanted to keep your face.

dculberson wrote:

BrokenYugo wrote: In reply to dculberson: SCH40 steel gas/water pipe itself is pretty strong stuff, the threaded connections with sharp grooves that cut more or less halfway through the pipe are not.

With a wall thickness of .133 inches, a 1" steel pipe can be cut into a lot more than 50% and still be stronger than the paper thin steel they make stuff like pull-up bars out of.

At 260lbs, I'm wondering if even the flimsy store bought bars are up to the task? I'm seeing 250lb limits on some.

Come to think of it, I wonder what the failure point is on 1" sch40 deflection test?

260 won't even tickle that thing.

I'm 212# and I bought the one that I linked above. The few times I hung from it, it was plenty strong.. Me not so much. But it does require more ceiling height.

You could also screw a couple lengths of 2x8 vertically, hanging down about 6" below the joists and then bore a hole through the 2x8 for a straight pipe. Fewer moving parts.

As a theater rigger, I'll add my two cents.

Never use tension fastening into wood. It doesn't matter how good the screw is, you're relying on the wood to not just give way and the screw just pulls out. Even if you use 180,000 psi ARP fasteners, if the wood gives out at 15,000 psi, its no benefit.

For lifting purposes, never rely on threads. Always rely on compression. That means bolts instead of screws. Pulling on those screws causes them to yaw in the hole, putting all the responsibility on the integrity of the wood. After repeated use the shank of the screw will either fail or the wood will finally fatigue and give way. A through-bolt causes compression. A significant portion of the torsion (shear) load is reduced because the bolt is squeezing the entire beam of wood.

In general, riggers always use grade 8 bolts (which really pisses me off). Grade 8 has its place. Shear is NOT its place. Grade 5 for shear, grade 8 for tensile.

Having said that, I think you'd be perfectly fine with a chin-up bar using 5/16" lag screws. I don't think you'll ever pull them out. I would personally use 5/16" bolts through the wood so I don't get surprised in case there is a soft spot in the wood, a hidden knot, or other void. In your case, don't use grade 8. Waste of money and overkill. 6 or 8 standard Zinc Grade 2 bolts will have 5 times the strength of the cast threads in the pipe.

curtis73 wrote: In general, riggers always use grade 8 bolts (which really pisses me off). Grade 8 has its place. Shear is NOT its place. Grade 5 for shear, grade 8 for tensile.

Could you please explain your logic here? A Grade 8 bolt of equal size, similarly loaded, is stronger in sheer and tension than a grade 5.

I, too, would like to know more.

Is it a brittleness thing?

Knurled wrote: I, too, would like to know more. Is it a brittleness thing?

That is the only reasoning I could think of but a gr8 still has a higher shear load than gr5.