Fasteners and bushings for a 4-bar linkage?

[Patrick Barnes]

I'd like to fabricate a linkage like this, but I'm not completely sure to build it.
(or buy one, but I had no luck finding something that goes from 0° and flush to 90° and stopped)

The bars could be made from pieces of angled and flat steel.
The action doesn't need to be frictionless, but it does need to be solid and reliable over time.
The fasteners need to be low profile and flush with the surface on one side.

• Is there a better solution than countersunk screws and nyloc nuts?
• Is there such a thing as a 'countersunk nyloc nut' (no luck on ebay), or a good way to keep both sides aligned?
• Are there low-friction washers or bushings to go between the bars that would allow it to move without wearing out or scratching?
  

-Patrick

[Matt Callow]

You don't say what size the final linkage will be, but what about transistor mounting bushes? 

http://www.mecint.co.uk/Item/118

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[Gav]

I don't know of any fantastic solutions, sorry. I'd try to avoid rotating a bolt in its countersunk hole, maybe put a nylock on the non-flush side so the bolt is rigid to the plate, and then find something bearing-like for the next segment?

Then maybe a flanged bushing to rotate against the bolt?:

http://smallparts.com.au/store/categories/

Smallparts's website is a pain, but have a search for 'bushings', and there's a few things that might suit. 

Cheers,

Gavin 

[kr...@sleepingplanet.com]

i'm not sure of the overall size of that, but might a kitchen cupboard hinge work?

they are/can be 0 to 90 with stopper and go flush with the added bonus of moving so that they don't rub one plane against the other...

[Patrick Barnes]

Hi Matt,

The linkage lengths are 50-120mm, depending. It will be used to hold up a shelf to which an electric piano is affixed, so the load between two linkages is about 10-15kg.

Shoulder washers! Brilliant, thank you for the term. (It's frustrating when you know the shape but not the name) They're plentiful and cheap on ebay, not like shoulder screws which cost ~$4 EACH.

So I'm thinking now of using those to keep the points aligned, with the countersunk bolt and nyloc nut through it to provide extra strength and tightened just enough to stop the linkage sliding apart.

-Patrick

[Patrick Barnes]

I looked at the available hardware out there, like 'cabinet stays' or 'lid stays', and they all looked a bit off...
About half of them are designed for upward-opening hinges, and searches return both.
A lot of them look dodgy, or impossible to adjust if sagging occurs.
They'd all need hinges as well.

I had no luck finding hinges with integrated 90° stop that could cope with a 10-15kg load. Are there any you'd think would work well?

-Patrick

[Max Nippard]

Not as nice as that linkage but we sell a couple of folding table brackets in stainless if you dont build one.https://www.whitworths.com.au/main_itemdetail.asp?item=85006

[kr...@sleepingplanet.com]

if your'e using two hinges that's only a 7.5kg load? 

some of the more premier hinges

http://www.blum.com/au/en/01/20/20/

wil hold that, you can also put shims in them to have it stop at 90 rather than 110 (normal cabinet opening angle)

not as nice looking but in the past a bit of chain has been used to take the strain and have the shelf stop where you want it...

[Patrick Barnes]

They're designed to fold *up*, but I suppose they might be installed
upside down and the locking mechanism removed.

Is that price for one bracket or one set?

[Patrick Barnes]

I didn't see a rating on that page, but I don't think a cabinet hinge rating would apply to force in that direction.
A bit of chain would work, yes, but it seems a bit risky. Remember, electric piano attached!

In case there was some confusion - that linkage picture in the initial post was upside down.
Here's what I have in mind;


-Patrick

[Kris]

Oh ooooooh
That's wonderful.

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[Patrick Barnes]

Another fastener comes to mind... Nutserts!


Any thoughts on whether they'd be appropriate?
(fixed to one side by the ribs and flange, with a bolt screwed into it retaining the other side while allowing it to pivot around the smooth part of the nutsert)

Do they usually have a constant O.D, or a taper?

-Patrick

Sent from my Android device with K-9 Mail. Please excuse my brevity. --

[Gav]

I've got a set of those in the space you're welcome to try. I'll leave it next to the vacuum system for you. 

Cheers,
Gavin 

[Patrick Barnes]

Ooh thanks. :-)

[Ada Lim]

On Tue, Apr 7, 2015 at 5:49 PM, Patrick Barnes <mrt...@gmail.com> wrote:

Another fastener comes to mind... Nutserts!


Any thoughts on whether they'd be appropriate?
(fixed to one side by the ribs and flange, with a bolt screwed into it retaining the other side while allowing it to pivot around the smooth part of the nutsert)

Are you thinking of inserting the bolt into the non-flange side?  I don't think they're designed to go in that way.  Perhaps if you tightened it on the flange side first so that it gripped, then put it in the other way.  (I don't know how much of the gripping is static deformation and how much is dynamic compression).

-A 

[Patrick Barnes]

My understanding is that nutserts are typically pressed hard into a hole, to provide a good thread in materials that otherwise wouldn't keep one. The only thing that stops them coming back out or spinning is friction from the original fit. I'm pretty sure that in a typical situation, tightening the bolt (inserted on the flange side) won't improve the nutsert's grip or make it expand like a pop-rivet.

I'm hoping to insert the bolt on the non-flange side. I do expect to be able to, because nutserts are open at both ends. (in order to cope with longer bolts)

-Patrick

On 8/04/2015 8:23 AM, Ada Lim wrote:

[Gav]

These particular nutserts come with a tool that'll pull back on them via the (say) M3 thread and 'crimp' them a little into the hole. A bit like a threaded rivet. 

However there's probably no reason why you can't just have a smaller hole and friction fit them. Worth a shot at least. 

Cheers,

Gavin 

[Patrick Barnes]

I understand better now, yes Gav and Ada were right about them being compressed as part of the installation.
That might work even better - the compressed bit forms a spacer - as long as there's enough body left for the other piece to pivot on.