The bolt may hold, but your footing may not. Over 20 years ago, I slipped while going downhill while carrying my metal field camera over my shoulder on a very sturdy tripod. The camera stayed on the tripod but hit the ground and bent the frame. Large format is a slow process anyway, I put the camera away when I'm moving any significant distance (long enough that I'd consider hoisting it over my shoulder).
Good luck.
Eric
Hey, I never even considered this question until it came up just now. I've been slinging my camera over my shoulder on a tripod for years and years (no idea actually what size the bolt is, and I've never inspected it).Originally Posted by Bruce Watson
But the question appealed to the cllimber in me, and it seems reasonable. Not because I think the bolt is likely to break, but because any time there's a lack of redundancy, and fairly high stakes, a bit of overkill makes sense.
Am I paranoid about it? Nope. Do I blame someone else for getting paranoid? Nope.
Someone needs to fess up to being stupid, so I will... about 3 weekends ago, I was walking on the road through a cemetery where I was photographing with my Shen Hao mounted on the tripod and the Sironar 210mm moounted on the camera - - all assembled and slung up on my shoulder. As I went under some low hanging tree branches, a branch must have caught on the QR lever on the tripod head and the camera and lense came crashing to the road - - but the 1/4" bolt on the tripod QR held! (Just kidding - - had nothing to do with it.) It is an older tripod head that doesn't have the little safety catch on the QR that prevents accidental release.
So while this story is only peripherally related to the 1/4" bolt, it is related to carrying your camera on the tripod over your shoulder. I have been carrying this arrangement for 4-5 years now, and the Mamiya TLRs the same way for 30 more years before that, but I don't think I will get over the sinking feeling of hearing the crash of the camera behind me enough to carry it that way anymore.
I bought new hardwood; I shaped replacements for the broken parts; I have reassembled the camera; and I am sending the lens off to be checked and repaired, if necessary... so I'm back in business... but I decided that the Shen Hao has that leather handle on the top for a reason and I'm going to remove the camera from the tripod and carry it that way from now on.
Westley
My LUG Gallery
Well in that case, I do a lot of photography of moving water where I set my tripod up in the water sometimes 3-4 feet deep.
I have knocked the tripod over in the water several times but the camera/tripod bolt has been solid each time.
The strangest time was when a 15-18" smallmouth bass came up and lunged against my tripod grabbing at the lever that locks the leg sections when you raise it up and down with his mouth. I was not more than 2 feet away when this happened, and if I did not see it, I would not have believed it. The tripod began to fall over but I was able to snatch the camera by the strap and save it. Of course since I often fish and photograph the same streams at the same time, I tried in vain the rest of the afternoon to cath that fish for dinner but was unable to.
Here are some real numbers:
The safe tensile working stress of a Grade 2 (read: typical crappy home-center bolt) 1/4"-20 bolt is 55,000 psi. With a stress area of 0.0318 square inches, that's a proof load of 1749 pounds.
How much bending will produce that much tension? If the center of gravity of the camera is 9 inches above the platform (which is about where it might be on my Sinar with the tall tripod adapter, but really much higher than for a field camera, it seems to me), and if the platform is about 0.6" from the bolt to the edge as it is (from memory) with a small Arca-Swiss plate, the weight of the camera might be amplified by a factor of 15 in the worst-case orientation (9 / 0.6). If my camera weighs 10 pounds, it might apply 150 pounds of tensile load on the bolt. Let's say I shake it up and down, resulting in a force of 2G's at the bottom of the shake. That would double that load to 300 pounds.
I would think all that is pretty much worst case. Most cameras are lower, the Arca plate that I use has a wider platform, and I don't think my Sinar weighs as much as 10 pounds. Plus, I don't shake it that much when it's over my shoulder--I'd have to shake my shoulder by the same amount and my legs can cushion load applications a lot better than that.
But we do have to add that load to the clamp load that exists because we tightened the bolt down. That clamp load at maximum tightening torque would be 723 pounds (when tightened to 49 in-lbs while lubricated). There is a lot that goes into clamp load, but I'll take that number as reasonable. That means that the safety margin is nearly 2 to 1. (1749 / (723 + 300) = 1.7).
And that's with crappy hardware-store Grade 2 bolts. The safety margin with Grade 5 bolts (typical bolt on a car) would be 1.9 (and that's if you tighten it to its maximum torque--much higher clamp load than with the Grade 2).
A 3/8"-16 bolt provides a safety margin 2-1/2 times what the 1/4" bolt provides. Many tripod heads and plates use a brass bolt in that size, which is probably no stronger than the cheapest steel bolt.
As for fatigue, the fatigue limit for steel bolts not loaded near their yield point is effectively infinite. Even when loaded close to their yield point, it might be millions of cycles, depending on how its made. Most bolts are stamped and have radiused thread roots that don't crack easily.
So, I think I've addressed all the concerns: The increase in the load from the leverage against the small plate, the shaking, the tall camera, the heavy camera, and the low-grade bolt, tightened to its maximum specification. Still a healthy safety margin. The only 1/4" tripod bolts I've seen that were broken were overtightened using a big wrench.
Rick "also an engineer" Denney
A long time ago, I was carrying a rented sinar over my shoulder.
Getting into a lift, I knocked the camera off the door, and the back fell off,
shattering the glass on the tiled floor-
Needless to say, the rest of the camera remained firmly attached...
Very interesting! But, I'm still not going to carry my camera while mounted on a tripod slung over my shoulder.
Everyone does what they are comfortable doing.Very interesting! But, I'm still not going to carry my camera while mounted on a tripod slung over my shoulder.
I carry my camera that way frequently, but only for short distances. My main limitation is my own clumsiness. The bolt won't break, but that doesn't mean I won't swing the camera into a post.
I was down at Niagara over the weekend, and suddenly the wind shifted and we were getting rained on by blowing mist. I picked up the tripod, threw it over my shoulder, threw the focus cloth over the camera, and ran. I never worried about the bolt
Rick "the picture from that spot sucked anyway" Denney
...unless, of course, while you are under the cloth setting up to take pix of those grizzlies in Yellowstone, one of their cousins approach from the south side, looking for a quick mealI consider this a valid question/concern. It should be fine... just don't go swinging it around as you would a baseball bat.
I’ve carried my 35mm w/ a 600mm 4.5 lens with the same 1/4bolt for 20+ years……no problem. I trust the bolt, not me. I’ve lost a camera one time because a bone head (me) didn’t take the time to make sure the camera was securely locked on the tripod head. When I carry my LF camera it’s for a short distance also. In a open field it’s over my shoulder otherwise under my arm covered with a focus cloth or in a bag. The only thing I’ve had break on me are those cheap plastic locking levers for the tripod legs.
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