Would you trust a $1,000 on this joint ?

[Roy Hess]

I really could use some opinions about the application of a “bed bolt”type fastening system in my application.


What you are looking at is called a Binocular Mount. They are used to hold large binoculars for astronomy enthusiasts. These binoculars can easily reach 25 X 100 power and beyond, 18” long and weigh up to 14 pounds. Because of their shear size, mounting them in some way to a tripod has many advantages.


I have changed my design somewhat, and am now proposing a 90 degree connection, using 1 3/4” Oak, a 3/4” piece of maple doweling, and a 3” x 5/16” stainless lag screw. All of this is assembled the same way that you would a bed bolt, for bed rails, or even a woodworking bench. I have made a slight modification, by adding a shallow dado in the vertical piece (1/4” deep ) for additional support.


Everything that I have read about these joints is that they are very strong. Considering that this specific joint would be holding at max, say, 15 pounds, with some minimal side to side pressure when in use.


So picture yourself using such a rig set up on a concrete sidewalk, with 15 pounds of glass hanging out there...................

[Brian Effinger]

What is the other end of this attached to (where the light colored arms are)? It seems to me that there would be a lot of tourqe? on the joint in question.

[Bruce Page]

Roy, that's a pretty good sized lever arm hanging out there. If it were me, I'd make at least the horizontal piece out of aluminum.

[Roy Hess]

What is the other end of this attached to (where the light colored arms are)? It seems to me that there would be a lot of torque? on the joint in question.

Brian - Here is a picture of the unit setup. Notice the change in location where the binocular holder connects with the parallelogram.

[Mark Mack]

Couldn't you just attach the binocular mount to the vertical piece of the parallelogram?

[Tim Sgrazzutti]

If it were me, and I wanted to stick with wood, my choice would be a bridle joint.

[Bill Petersen]

I voted yes, but then....they're not my binocs. I think that joint would have the strength. I'd be more worried about knocking the whole darned thing over.
Bill

[Brian Effinger]

Couldn't you just attach the binocular mount to the vertical piece of the parallelogram?

Or get a taller tripod?

Anyway, I'll stick with my poll respose of adding some sort of bracket. I just wouldn't trust such an expensive set up to only the bolt. A back up would be nice.

[Don Bullock]

I didn't vote because my choice isn't there. Bill made a good point that I agree with.

I'd be more worried about knocking the whole darned thing over.

If it were me I'd do something totally different that was a lot more stable. I think your binoculars extend too far beyond the center of the tripod. It just doesn't look like it's well balanced.

[Paul Steiner]

I would be more worried about getting caught looking in your neighborlady's window.

[David Moody]

Roy,
Have you checked in with this at the DIY ATM forum on Cloudynights.com? There are several folks there who have made bino mounts and would probably have some excellent experienced based advice to give here. I would check there just because of the experience base with this type of construction.

I have worked on building dobs, but not bino mounts. However, my experience with most of them is that they use aluminum and/or steel brackets with vertical pins to hold the binocular underswing mount to the parallelogram. You have a pretty dynamic load out at the end of that moment arm, so I agree with your concern.

[Fred Belknap]

probably work but I wouldn't trust it. a simple half lap with a bolt or two would be more secure.

[Roy Hess]

Couldn't you just attach the binocular mount to the vertical piece of the parallelogram?

Yes you could, but you would begin to limit the full range of motions, and the versatility of the parallelogram.

If it were me, and I wanted to stick with wood, my choice would be a bridle joint.

That's an interesting option. I may give that a try - Thanks !

If it were me I'd do something totally different that was a lot more stable. I think your binoculars extend too far beyond the center of the tripod. It just doesn't look like it's well balanced.

Yes, you might think so. The surveyor type tripods give good stability when in use, and the long reach of the parallelogram is considered an advantage when sitting down and viewing from a chair.

Have you checked in with this at the DIY ATM forum on Cloudynights.com?

Yes, I post there regularly. Thought that I would post this question here as I am interested in comments from the woodworking community, on the strength of the wood joint, as opposed to the design of the mount.

Thanks for your comments so far, they really are helpful !

[John Schreiber]

By any normal measure, that should be strong enough. It's just imagining $1,000 worth of glass hanging off of it that scares me.

One - you could reinforce it with some aluminum plates screwed into the wood from each side. That should make it bomb proof, but you would have to come up with something clever to make it removable.

Two - mount something twice as heavy as your binocs on there and try to break it. When it doesn't break, you will feel comfortable with your usual load.

Three - add a safety wire, so that if it breaks, it just bonks you in the face and doesn't hit the pavement.

[Steve Rozmiarek]

Wonder if you could just make the horizontal piece different, rather then just one square profiled piece, make it more of a triangle tapering down from where the parrallegram ends, to the mount for the binocs needs to be. That way you would have room for two bed bolts, rather than just one, which should more than double the strength I'd think. Keep the shallow dado though.

It would at least address the major problem of the bed bolt pulling the grain out the end of the horizontal member, and immediantly dropping your pricey glass. Two would probably provide you some notice if they where to fail.

You could also skip the bed bolts, and just mill the whole part out of one piece of lumber, and take your chances with the bolt on the binocular end.

I think you're fine as is, but...

BTW, I've always thought that those binocs where more expensive then that, could they be used to focus on much closer objects, like several miles?