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How do I adjust rotation with discrete stops?

2363 Views 21 Replies 9 Participants Last post by  Stokestack
Hi all.

I made this driveway mirror and mounted it to a post. I needed to be able to adjust its tilt and rotation a bit with the mirror in position, then lock it securely at the correct angle.

I tried to use pipe fittings with locking collars (picture attached), which worked for a while but continually moved with wind despite being secured with "permanent" threadlock.

So what I think I need is metal discs with holes through them, which can be rotated in relation to each other then locked in place with a pin. Almost like a super-robust lazy-suzan bearing with discrete stops. They use large versions of what I'm talking about on exercise machines, to adjust the position of armatures for different-sized people. I tried searching using relevant terms but haven't found anything. Maybe I just don't know what they're called. Any suggestions?

I'd make something myself, but I don't have the necessary tools to cut and drill through steel discs.

Thanks!

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thoroughly clean then put locktite on all of the treads....
use the unions for the rotation,,
rubber cement the union flanges...
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@Stokestack,
Gavin, unless you plan to re-adjust the mirror, have you considered drilling through each joint, flange and union, and driving in a nail or a self-tapping screw? At most it might cost you a metal-cutting drill bit.
As far as I know, threadlock is designed to break with sufficient load - I believe it is meant to prevent unthreading due to vibration.
Thanks for the replies.

I might be able to drill through the joints... I guess it's a reasonable idea. I have metal bits.

I also have some 3M panel-bonding cement, which might be strong enough for this application.
locktite red or gray will keep the threads from turning unless you demand it...
you will need to clean the threads 1st...
2
why not use an automotive/truck mirror bracket...
there are a zillion bracket assemblies to choose from...
https://www.iowa80.com/browse/brackets-and-braces-for-truck-mirrors/MIRRBRCKT/UNI/

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I think you might be able to do what you want by moving the horizontal mount to the center of the left stile (as viewed in the picture). If need be make the vertical pipe taller. By centering the horizontal mount to the mirror you will distribute the weight more evenly and it should not tilt once positioned.

If you have access to drill bits and taps you could drill and tap a hole in the female joints and put a screw in against the male threads.

You could also consider eliminating some of the joints and using only straight pipe between the elbows...

...more ideas after coffee... :smile:
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Get a good pipe wrench and tighten all the joints like they should be tightened and I don't think you would get all the movement problems. If part of the problem is people running into the mirror and knocking it out of alignment then drilling the joints and adding screws after adjusting the mirror should help but might hurt someone if it will not give when hit.
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Thanks for the replies.

I might be able to drill through the joints... I guess it's a reasonable idea. I have metal bits.

I also have some 3M panel-bonding cement, which might be strong enough for this application.
just a thought what if you drilled at the joints and threaded the holes for set screws then you could still adjust them if needed. I also like sticks idea of using truck style mirror brakets. You could probably find something at a local auto salvage yard.
Hey, Gavin; looking at the design two things strike me.
1) the horizontal arm is allowing the wind effect to add significant torque /leverage to the vertical joints portion. Maybe eliminate it? (as Nick suggested)
2) same problem for the low mounting position on the mirror; the mirror weight is acting against the joints in the horizontal portion. Move the attachment point to the middle of the mirror panel
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Both good notes about the attachment points. I would have opted for different ones, but unfortunately this application required this arrangement for several reasons. The mirror needs to:


  • Be above the existing, useless, management-installed one
  • Be be tall, to be usable from vehicles of significantly different heights
  • Be elevated higher than this pole to provide adequate view
  • Extend out from the pole toward the street to provide adequate view
  • Not extend out any farther, because trucks will hit it

It seems to me that changing the attachment points by extending the pipes wouldn't change the forces exerted by wind and weight.

I don't think that truck-mirror mount would support this thing or provide enough resistance to pitching downward (because of that smooth piece of metal), but good suggestion. I might look at other designs.
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"It seems to me that changing the attachment points by extending the pipes wouldn't change the forces exerted by wind and weight."
-Gavin

If you used a longer vertical pipe nipple...maybe 10" longer...you could mount that wider mirror support board at the 1/2 way point or slightly higher. That would change nothing in the mirrors actual position.
The good news is that the existing mirror-applied-torque is actually tightening the connections, except for the union ( I think?)
The vertical column joints are still at the mercy of wind pressure on the mirror arm, if the wind comes from behind the mirror. I'm all for drilling, tapping, and set-screwing the joints.
On another aspect entirely; almost all malleable iron fittings are from China, with the quality of the metal up to their usual high standards. *zips lips*
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Both good notes about the attachment points. I would have opted for different ones, but unfortunately this application required this arrangement for several reasons. The mirror needs to:


  • Be above the existing, useless, management-installed one
  • Be be tall, to be usable from vehicles of significantly different heights
  • Be elevated higher than this pole to provide adequate view
  • Extend out from the pole toward the street to provide adequate view
  • Not extend out any farther, because trucks will hit it

It seems to me that changing the attachment points by extending the pipes wouldn't change the forces exerted by wind and weight.

I don't think that truck-mirror mount would support this thing or provide enough resistance to pitching downward (because of that smooth piece of metal), but good suggestion. I might look at other designs.

By mounting the horizontal attachment higher (middle of the vertical frame) you will eliminate the weight torque because the mirror will be balanced. By drilling, tapping and set-screwing the joints it will take care of the wind pressure. Think in terms of lever...the way you have the horizontal attached at the bottom of the frame the wind has the greater advantage...

You could minimize the wind torque by adding a rail in the center of the frame and attach there and further minimize the outward weight pressure...
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Maybe a bracket from a satellite dish?
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Maybe a bracket from a satellite dish?
best plan yet...
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@Stokestack

...how about if you attached the vertical on the side of the 4x4 a foot or so down and add a clamp around the pipe at the top of the 4x4...this would give you two mounting points for the vertical...?

...sorta like mounting an old TV antenna on the side of a chimney...

Gonna suggest a re-design...mount a straight piece of pipe with u-clamps to the side of the 4x4...go straight up and elbow a short piece of pipe to attach to the mirror. Put a rail in the center of the mirror to attach the short horizontal pipe to. Use a wedge to create the down angle for the mirror. No more wind or weight problem...

If it worked for TV antennae it will work for your mirror...what'd ya think...?
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Must the mirror be as pictured? Flat & square?
If not
how about a
"hospital corridor mirror"
https://www.google.com/search?newwi...hUKEwi-3Y7S-NPpAhWSknIEHVg1DScQ4dUDCAk&uact=5

or "safety mirror"

https://www.amazon.com/Premium-Conv...d-search-10&pf_rd_t=BROWSE&pf_rd_i=3430079011


Google it
Ha, thanks for all the brainstorming, people!

The current design evolved out of doing it as inexpensively as possible using only the wooden post that the management put in. But... recently somebody dumped a really nice 2 x 4 next to the building, which I could indeed secure to this post to extend & widen it.

The number of joints I used was the only way I could (under the above limitation) figure out to allow adjustment in two planes. But yes, it's probably best to abandon these limits, put the taller & wider board up, and use metal pipe with U-clamps affixed so the horizontal pipe crosses the vertical center of the mirror, as @Nickp suggests.

Must the mirror be as pictured? Flat & square?
Absolutely yes! Convex mirrors are wholly misguided in a driveway application. They show you the sky, the building behind you and across the street, yourself, the sidewalk... when the only objects of interest (cars coming from the left) are tiny specks with grossly distorted proximity. They're quite dangerous, and one resident's car was already totaled even with the management-supplied convex mirror in place.

You only need to see the cars coming from the left, so in this case the total field of view only needs to be two lanes wide. That's easily accomplished with a flat mirror, which provides a large, undistorted view and accurate way to judge distance. The building residents loved it and have been lamenting its breakage for months.
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Here's what I ended up going with. It reflects (har har) several improvements as suggested in this thread, and some that became apparent as I put it together. It's not as high as the previous one, but if I need to raise it I can.

The bars are 1" conduit. Mirror tilt is secured by a metal strip with holes in it. Clockwise yaw is prevented by a stop-screw in the top of the pole, counter-clockwise by a wooden bar pressing against the back of the mounting board.

A key find was conduit-couplers with set screws; I cut them in half to make collars and caps that I could slide over the conduit and lock it in place to prevent it from sliding out of the U brackets.

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Certainly looks like you've got all the angles and dangles covered...:smile:
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