Shear load on bolts 4

[Jack_]

Hi all.
Trying to build my DIY weightlifting rack (bench press & squatting).
The two beams are 60x60 mm (3mm thick) galvanized steel.
The issue is with the hinges. Making a special welded hinge is too expensive.
Thought of using M22 bolts. The Olymic barbell will rest on one M22 bolt on each side, must hold up to 150 kg on each bolt (~300 lbs), about 5 cm from the beam.
Will it hold?

In the image (model): pencil = barbell
Did a test with an 11 mm thick bolt, bended after just 50 kg, and completely at 75 kg (although I placed the load ~9cm from the securing nut).

 

[SRCELL]

Might want to think about an impact load unless you plan on setting it gently each set.

 

[MegaStructures]

Yikes. Don't do that. Can't you use wood?

 

[Jack_]

&SRCELL
Yeah, a slight impact load is also an issue.
Let`s say dropping it from height of ~5 cm. Does it change anything?

 

[SRCELL]

Use wood. There's a bunch of how to videos on this now

 

[MegaStructures]

IMO you have to assume at least double the static force for a sudden drop even from just a couple inches. The bolts are going to be way too short for you to rerack your weight and far too weak. If you already have the tubes buy the J-hooks from a reputable company like Titan or Rogue. The better idea would be to probably just not do this though. How's the rest of your setup framed?

Wood is a much better idea, but make sure you know what you are doing, I've seen some bad injuries from DIY racks.

 

[Jack_]

&MegaStructures
It`s an open roof: sun, rain... I`d prefer steel.
Would adding a block of wood on the space between the bolt and the 6X6 beam suffice to provide the bolt with anti-bending support?

 

[MegaStructures]

Now you're getting closer. If you bolt at the top and bottom of a tall wood block you have yourself a much better setup. That way you can resolve the moment in the connection through a force couple.

 

[Jack_]

&MegaStructures
You mean resting it on a tall wooden beam?
I know it`s stronger, but I need height adjustment. Cannot just let it be a single beam to hold the weight at the top.
Rest of the setup is that I have an old base from an elevator, a UPN 10 mm. On its sides I`ll bolt the 6x6, and on them the hooks.
Buying commercial J hooks is last resort as it is out of budget for me, and missing from stores in my area.

 

[MegaStructures]

No I mean like 10” tall. Use multiple bolt holes on your support structure.

 

[Jack_]

OK, I got you.
The only problem with that would be, it`d require high precision in making the holes.
What bolt thickness should I use for that, if it`s 2 bolts holding a piece of wood, say the bolts are 2" apart [top to bottom] from each other? (are 2" that enough?)
And how to secure the barbell from falling from the wood (I don`t want to shape the wood)?

 

[MegaStructures]

Doesn't really require high precision to make the holes. Do you already have holes in the steel? If so, put your block of wood against the steel and mark the holes, then remove the wood and drill where your marks are. If you don't have holes drill them first and then do that process, it's called match drilling. As far as the forces It's simple statics, the axial force in the top bolt will be equal to the moment caused by the barbell divided by the distance between the bolts. Surely you took statics if you are a civil engineer. For the axial strength of the bolt multiply the cross sectional area by the strength of the bolt. The shear strength is even easier to figure out.

 

[Jack_]

 

[azcats]

I'm no fan of the rack in the link below, but there are a lot of them out there. They use 1 1/8" bolts for the pins. See item 8.

https://startingstrength.com/files/starting_strength_rack.pdf

I'd also recommend the factory made stuff but that is hard to get these days.

 

[rb1957]

so if you used metal for the block, instead of wood, and tightening it hard then it'd work better.

If you slope the upper face, to the load naturally drifts to the wall (support), that'll be better too.

If you don't use fully threaded bolts (but use bolts with a plane shank over the shear plane) that'll be even better.

another day in paradise, or is paradise one day closer ?

 

[Jack_]

@Azcats
Is this bolt 1 1/8 thick or just the head 1 1/18 (sorry, I have a hard time understanding inches.

 

[Jack_]

@rb1957
Thanks, I wish I could slope, but the design doesn`t allow that.
If I secure the bolt with just one nut, I might be able to use half threaded bolts, but the bolt will still have the thread at the contact points with the 6X6 pole.

What metal block would you recommend. Is a 6X6 cm square tube, 3 mm thick is enough?
And what orientation? (it`s gonna be open in one orientation)

Thanks everybody for your help here!

 

[azcats]

Jack - that's the diameter of the bolt shank. Similar to an M30 I'd say.

Couple photos of how they're used here:

https://www.tworepcave.com/10649/more-than-you-ever-wanted-to-know-about-power-rack-j-hooks/

 

[rb1957]

Nah, it's not M30 … compare the bolt to the scale beside it … looks like 3/8" or 1/4" (something like a pencil).

Ok, you can't machine a sloping face … can you machine a groove ?

I was thinking a block of Al, but a tube would be fine. If the walls of the tube have trouble, fill tube with wood.

another day in paradise, or is paradise one day closer ?

 

[azcats]

Hey rb1957 - I was referring to his question on my previous post. Different approach than he's attempting with the filler blocks where it's simply a large dia bolt.