Can you get hold of any nylon to try instead of rubber?

I can try but I am still afraid that having zero flex in the bar stock will cause me to not get much friction from anything that I can squeeze in.

Bruce

Reduce the amount of friction force required at the hinges with some springs.

Unless we somehow come up with a better idea I would probably remake the middle part about 1.0" to 1.5" wider. I could then put some stiff springs and fender washers in between the inner and outer bar stock. My design had 1/16" top and 1/16" bottom gaps. My jig-less welding gave me about 1/16" total on one end and about 1/8" to 3/16" total on the other end. Pretty sad holding to tolerance, even for freehanding.

A smaller gap with smaller springs would be even better. I don't know what McMaster, MSC & others have available. My brain is currently stuck on lawn mower valve springs. They are too long but good to think about. Stiff springs with fender washers on each end would work but not be very "home" looking.

The spring type I had in mind was a torsion spring that could clip on right at your hinges to make spring-ed hinges. As far as the gaps in your hinges, I'd consider some plastic tube bushings. I'm sure you can find something like a PVC tube that you could cut to fit. I wouldn't use something like Teflon because you should be looking for some friction to hold things in place while still permitting motion.

Another well presented question. I don't have an answer at the moment but your problem is worth some consideration. This is the problem I face at work all the time, a good design idea that doesn't quite work the way you expect. Don't fear, your design and construction looks promising. It just needs a little more research and experimentation.

My first suggestion is to grab your trusty McMaster Carr catalogue and start thumbing through it. Somewhere in those thousands of pages is the piece of hardware that will do what you want. If it isn't there, you will probably have to invent it.

I am in now way associated with this company. I has just been my experience that most engineering problems can be resolved with their catalogue, a Swiss Army knife, and a roll of Duck Tape.

Look up Gobo heads as part of C Stands, and see if that helps. See if you can visit a Film Grip Rental supply house and look at some C Stands, and see if that helps.

Studs in the wall aren't always where they are supposed to be. Zipits will hold lots of weight in sheetrock on their own.

Also consider spline and axle rods instead of joint washer splines. You may also look at whatever Timpkin (sp) may offer as hardware ball bearing stuff, etc.

We, me don't care what it looks like, as long as it works. Paint it black. P.S. Matthews probably makes some grip equipment that will do what you want one way or another. I could see screwing a Junior Wall Plate into the wall and putting an offset arm in the receiver with an upturned plate to hold the TV on another bit of rig in about an hour and a half if I had a full grip kit from Matthews, who I don't work for.

Drill and tap the outer 3/16x 1" bars and use a thumb screw to lock things in place. Put a fender washer in place of the red rubber to prevent marring.

GA. I was thinking of bellville washers, but hadn't considered the delrin.

mareng,

I really ticks me off when people don't read the entire post and later in the thread suggest the same solution that I had already made.

Well, it seems that I _{(and one other poster)} did this very thing to you, here.

Sorry for repeating what you had already clearly pointed out.

I'll add my GA to your stack.

Interesting to think about ...

I have a modest home wood shop with an abrasive cutoff saw and MIG welder to add the slightest of metal capabilities. I'm afraid that without a lot of work on jigs my modest tolerances might still give me problems.

I know that there are friction hinges for laptop displays, but they are not directly suitable, too expensive and not available to the home hobby market. I still kick myself for not "redirecting" one of them at my old job for an engineering educational experiment. I always wanted to cut one open and see how they work. They worked great and lasted a long time, but at $10+ each (not pair) I couldn't cut open a good one.

At the moment I think my top option is to rebuild the center section to accommodate stiff compression springs and fender washers between the flat stock. But your suggestion is rattling around in my head. We'll see what falls out.

Thank you,

Bruce

You'll get there. I can only speak for myself, but, when I get stuck on a project, and the answer comes, it's usually so simple, it's embarrassing.

At the moment I think my top option is to rebuild the center section to accommodate stiff compression springs and fender washers between the flat stock.

Couldn't you use longer bolts at the hinges and put stiff springs on the bottoom such as rocker arm type springs and use fender washers on both ends?

What you need to do is print off the picture on Kramarat's thead (No 10) take it to a shop & buy one.

Bazzer

You might want a positive-stop spring at the wall end and an adjustable-tension 'brake pad' at the TV end. You'd need to round-off half of one end of the wall-end swivel bracket, and round off all of one end of the TV end swivel bracket. (What I've shown won't give you full 180-degree motion for the TV, but you could tweak it a bit as needed to get to 180.)

By using the end of the bracket you don't have to worry about the clearance issue between the different sections of the arm.

Something like this:

I'm not sure I am totally grasping this one. The positive stop spring seems to be slipping into a "detent" hole and the "brake pads" seem to be similar to the friction on washers we have talked about.

One of the other posts had words I Googled that led me to a Hollywood lighting supply store. They had small pads that looked like they were made for providing friction when parts rotated. I had to go to work so I haven't had a chance to investigate them further.

Thank you,

Bruce

Check out the barrel hinges here, http://images.google.com/imgres?imgurl=http://www.hooverfence.com/ornamental/hinges/jbh5.jpg&imgrefurl=http://www.hooverfence.com/ornamental/hinges/index.htm&usg=__hRUx1btuf-e8Ge_g4TUZPyrrvFI=&h=388&w=528&sz=33&hl=en&start=58&zoom=1&um=1&itbs=1&tbnid=66MJKXpT0lNLiM:&tbnh=97&tbnw=132&prev=/images%3Fq%3Dfence%2Bhinges%26start%3D42%26um%3D1%26hl%3Den%26sa%3DN%26ndsp%3D21%26tbs%3Disch:1, I'm thinking you could drill out your holes and press fit, followed by welding in place. Might work. I'm looking at the 3" ones in the first picture. Press fit from bottom and top at the pivot points, centering the swing space within the 1/16" clearance. It should give you just enough so that the metal bars won't make contact and scrape off the paint.

To be fair, the Belleville link is mostly (as far as I can see) talking about correct installation with regard to the static¹ electrical properties. This isn't what's needed in this app. - purely mechanical, and moving (i.e. some kind of friction washer - could be fibre, plastic, or whatever).

1) Give or take a bit of vibration.

Sorry,

Belleville washers are a mechanical device, not an electrical device:

"Belleville Washers

Categorized as a spring washer, Belleville Washers are defined by their conical shape. This unique shape provides a deflection property that is ideal for applications that require spring-like flexibility. In addition to deflection functionally, Belleville washers may be used to create a locking mechanism in applications with low dynamic loads.

Belleville Washers are designed to be loaded in the axial direction and can be statically loaded to be continuously, intermittently or cyclically deflected. Based upon the arrangement of stacked columns of Belleville washers, variable characteristics can be achieved. Belleville Washers are used for maximum "load build up" with minimum washer deflection. Belleville Washers are used singly and provides a larger washer load in smaller spaces."

I believe you mis-read the cyclic reference. I used them in one of my first jobs, building truck mounted "cherry pickers".

I'm sure friction washers can work too.

The bit of your link that caught my eye was:

"Most often, you'll find Belleville washers in applications where you have to connect bare, soft aluminum to aluminum or copper, or where you have conditions of high current loading or cycling. These washers do wonders for accommodating thermal cycling, but they can't eliminate all the problems resulting from poor workmanship. You must prepare the joint properly (as with any connection), but the key is selecting the proper design and size of Belleville washer for the fasteners and conditions of your application."

... et seq.

I guess it's because it was an article in "Electrical Construction & Maintenance (EC&M) magazine". Sorry if I took it wrongly.

For this app, I thought of the (vaguely) similar Schnoor washers - but maybe they're OTT. I used them many years ago (I still have a small stock of M3's) - I believe they're expensive!

I'm still backing my nylon washer scheme . Maybe nylon or Delrin (a la mareng in #9), in conjunction with some nice springy washers ... come to think of it, I'll give #9 a GA.

No, you took it right. My mistake for not posting something more to the (mechanical) point. ^{_{(I hate it when I'm wrong)}}

I don't think this will be the ultimate solution, anyway. I'm leaning toward friction washers. Much simpler.

wave washer was my first thought too!

I've used wave washers in joints for products similar to Angle-poise lamps but without the need for support springs. Once you get the compression on the wave washer right it should provide a reliable friction force. The product I was designing would have had the joints tested to 10,000 rotations without appreciable loss of friction.

In the OPs situation it would mean using a screw & washer to compress the wave spring then locking the screw with Loctite.

You might try substituting a welded stud in place of one bolt in each hinge, with brass washers and a wing nut to provide easily adjustable friction and fairly secure position lock.

Firstly, I hope your builders space the studs accurately, and that the specified stud spacing hasn't changed over time .......

Secondly, on your pivot issue, what about a wing nut and a cup washer at each pivot to clamp them, or if you want it to stay in position without having to clamp it, you could enlarge the overlap area of one knuckle at each pivot, grind an arc of detents in on side and mount a spring loaded ball (they are available from some hardware stores, or you could make your own) in the opposite wiping arm.

Thoughts

Bill

have you thought about using shoulder bolts witn flat washers and nylock nuts. The flat washers will keep the pin (shoulder bolt) from riding on the articulated arms. The nylocks will assure that the assemblies are not going to come apart.

You might try leather washers made out of some old stiff leather.

Now that is the sort of simple ideas I was looking for. More friction than Delrin/Teflon but still durable and not likely to shed metal/paint. There are several good ideas in this thread and leather washers is one of them.

Thank you,

Bruce

Are you trying to mount a Boeing 747 on your wall or a TV? I realize that things are bigger in the US but surely this is taking the piss.

I am mounting a TV to "engineer owns the house" standards. Bump it, it stays up. Go off balance and grab it, TV stays up.

My roofing is over code. My hurricane shutters are over code. My storm protection of doors and windows is over code. When Hurricanes Charlie, Jean, Francis and Wilma went through I only had landscaping damage. Overall I'm pretty happy with my approach to things. Sorry if I offend.

Bruce

Tamu and I are on close pages. Gobo Heads for C Stands will put things in an incredible variety of positions with extreme safety concerns and procedures designed to be fast and safe.

Whereas Tamu in Audio Visual uses a hacksaw a Gobo head uses circular opposing cuts, or what I call wheel splines.

You can loosen them and tighten them up in many positions. They are only part of a Grip Kit. While you may want to engineer things to your own standards, and I'm not there touching the thing. I will say you will now or later benefit as engineers if you are aware of what mature filmmaking tools are able to do.

Truly I am not, and have never claimed to be an engineer, but have been a Key Grip, and spent enough time as an aircraft mechanic, or mechanics helper to appreciate good tools and how you use them.

In my working career I have worked with many tools and rigs and to every engineer of CR4 I suggest they be aware of movie Grip tools and procedures as part of the mental library to bring to problems.

I had a very dangerous job when I was grilled, properly I might add, by the Business Agent representing the IATSE Union crew I needed to put up a light rig. At one point the BA asked me forthright if I was an Engineer, and I told him "No, but I'm a Key Grip."

In that case I did have to fabricate a job specific tool for the job, but it did get done.

Back when I was Video Committee Chairman at a Community College in Rochester New York I had TVs mounted all over the campus. Just bought the mounts. Everybody watched my TV Channel more. Was fun.

Too bad UNTV ain't much and hard to find. Since I'm not so robust at all and physically strong as I used to be, I drift back to what I did in College.

Was never without a job back in that recession, but compromised from Director, to Grip or Writer or Actor.

Anyway once you have worked a C Stand, maffer clamps, offset arms, used pinned clamps of all types, receivers that work off trees, cranes and dollies of all types, you at base will love film making tools, even if you don't love filmmaking.

Remember these things are meant to be able to be put up safely very fast, and if someone like a Million Dollar a Minute actor gets killed, you sure ain't working ever again, just like Aviation Chief Mechanics are done if they signed off on bad mechanics.

I only had a few minutes today to snoop through http://www.cinemagadgets.com/index.php and other "cinema grip" sites, but I do understand and agree with what you are saying. As most of us become obedient consumers that limit the scopes of our lives the grips live a life of adapting to and overcoming all sorts of problems. The cinema sites are very interesting to look at. Trying to understand them requires the use of WikiPedia to translate Grip into English, but that can be part of the fun.

Bruce

Hi, Sorry I did not wish to offend you. I am sure that it will take more than a hurricane to knock down your TV if it is mounted on that. We don't have such bad weather conditions here so it just looked way over the top. Thanks for the clarification (you learn something new everyday) and hopefully you will get thru the next hurricane unscathed.

Once again 4 thousand ways to overthink a project!! Using a Delrin or any other polymer type washer should take care of your issues as long as you have ground or sanded the surface smooth. I can only hope you do not plan on repositioning your TV 500 times a day, if that is the case only a bearing will do. The washers should out live you!

With my poor tolerances from back yard welding and the smooth surface of the Delrin I am confident that the TV will be moving due to both the "downhill" effect of not being manufactured perfectly and the force of the air conditioner.

I'm pretty good at making unexpected mistakes and I am pretty sure that I was headed for one. I wasn't overthinking if I didn't yet have a workable solution.

Bruce

try spring washers they should provide tension but help eliminate slipping

Would shoulder bolts help? You would have to drill out some of the holes to allow the bolt to pass through and then you can tighten against it without a washer in between. There are many different sizes of shoulder bolts available.

Spring type spacers in place of washers might work but not really. Use instead a pair of adjustable cross braces (seeing how rigid your frame work is you might do with only one centrally placed brace). The brace(s) would pivot on one end & pass through some slot with fastening/securing bolts coming down at right angles to the adj. brace. (consider also a curved brace to accomodate space restrictions) Another method to secure the frame position(ing) is a set of set of half circles mounted adjacent to the pivoting sections of the frame. The half circles should have holes or slots about its circumference & the adjacent frame should have matching holes. Insert a bolt or pin appropriately to lock in the favored position. Carlos

Google "friction grease". Put a dab on the interference surfaces. This should take care of the rubber getting torn up and provide a dampened motion. The trick will be to get the right amount.

You can try and weld larger washers to the bolt head and the nut to tighten it. This would give you a greater friction area. Just torque them down good for more friction and a tighter swivel. You might even slide a thin washer in between the moving parts, if you can get a rubber washer in there than you should be able to get a thin flat washer in there easier.

Teflon washers.

Adjust desired tension with the pivot bolts.

3/16" x 1" steel is not going to flex more than thousandths or less with my shoulder bolts. With my tolerances I am at least several orders of magnitude away from being able to make the friction adjustment with the bolts.

Thanks,

Bruce

Bruce,

You have plenty of suggestions now that seem at least plausible that they will work. Try one. If that one doesn't work try another. If neither work give us an update on what happened in each case and why it is not satisfactory to you. Maybe you could combine a few ideas to minimize the drawbacks of each approach used individually.

Now I want to try it to see if I can make this work.

Too much? Sorry.

I understand the desire to make something like this because one might think, "I could make one of those and do it better and cheaper." I'm not sure if this is one of those times where it works out that way. There are some great wall mounts out there that work really well. I had a Sanus mount that was great, and I think it was under $200. I hope for your sake that you haven't invested too much money or time into this.

As far as your problem, I like Randall's proposed solution to compress the nylon washers.

Also, maybe you have already thought of this, or maybe it won't be an issue at the height at which the TV will be mounted, but having the ability to tilt the TV forward slightly is handy for reducing glare and setting a more direct viewing angle.

Thank you to all. I now know what I want to try next.

My apologies to Redfred in #52 and to others for taking so long to post this "I think I have my answer" posting. The people that give me money to pay my bills expect me to show up 5 days a week and think about their problems. It is actually a very good gig, but it interferes with home projects.

My EUREKA moment was when Randall posted #35. My current prototype is configured like the left side of the drawing in #35. Some of the problems with the left side of #35 are:
1) Any changes in tightness, even imperfections in flatness or level, will affect the tightness on the other pivot point of the pair.
2) Attempting to put washers or other material BETWEEN the wall mounted arm and the articulated arm was very awkward, a lot of physical effort, very dependent upon fabrication imperfections and affected by the other pivot point in the pair.
3) Attempting to get my friction on the OUTSIDE of the arms had pivoting between bolt head and top washer(s), top arm, lower arm, lower washer(s) and lower nylock (nylon insert lock nut). Lots of pivoting surfaces made worse by the upper and lower parts of the pair interacting with each other. ("Interacting" = "teaming up to work against me")

I do like the look of the left side of #35 better than the right side, but the right side of #35 makes most of my problems go away. Some of the great things about the right side of #35 are:
1) The friction at the upper pivot point is completely isolated from and independent of the friction at the lower pivot point.
2) I can weld in the shoulder bolts (assembly impossible with welded bolts for the left side of #35). This makes mounting the TV MUCH EASIER and eliminates half of the rotational friction (or lack of friction) points.
3) If you consider that I was totally stuck on trying to add friction BETWEEN the stiff and poorly toleranced horizontals of the left side of #35 then you can start to understand that switching to the right side of #35 was necessary for the springs (Redfred #3 and others), wave washers (Rorschach #17 and others) and Belleville washers (Lynlynch #18 and others) to take their rightful place in my solution. Trying to use them between the horizontals of the left side of #35 didn't help me much. Using them as shown on the right side of #35 should work wonderfully.
4) Welding the bolts in place using the right side of #35 and using one or more of the springs or spring washer suggestions should make creating and adjusting the rotational friction easy to the point of being almost trivial.

If by chance I ever need a better pivot point then there were suggestions in the thread for items to purchase. The barrel hinge link is in the thread. I googled "gobo heads" and "C stands" as suggested by Transcendian in #7 and found all sorts of interesting things including special fiber material that is made for gaskets but is also used in the film industry to provide rotational friction like I am seeking. I don't think I need this now, but it was interesting and related to my problem.

Kramarat had it right in #13. Once I understood that I was barking up the wrong tree the solution was so simple it was embarrassing. (Actually I wasn't that embarrassed, but the solution was simple).

A big thank you to all for your help.

Bruce

I would think the weight of the tv would cause enough friction for the joints to stay put, if the unit is mounted level. I don't see an adjustment for tilting the tv. Mine is mounted up high, and angled down for viewing.

Like you say, the mount doesn't show, so it shouldn't matter if the paint at the joints gets scratched.

I would think any kind of delrin or teflon will make for less friction. The leather suggestion seems best to me. Love the smell of leather in the morning.

I wanted to provide a progress update but I didn't finish cutting and welding before the rain started. I didn't want to try "MIGging in the rain".

This is a weekend only, outdoors only projext. Hopefully I will have pictures of the final unit next week.

Bruce

I would not attempt to weld the shoulder bolts in place Bruce. Those bolts are high carbon steel and the weld will crack almost instantly.