4 Bar Linkage Joint Options 1

[MechyMech]

Hi all,

I have an assembly of serial four bar linkages designed, but am looking for different options on implementing the joints, which I need to be relatively low-profile.

General info: The loads are very small, with linkage lengths 0.625-3.000" and widths 0.250"-ish. Linkages are made of either stainless sheet around 14ga, or aluminum sheet/flatbar a bit thicker.

Obvious options:
- shoulder screws w/washers and nuts
- pins w/grooves to receive retaining rings or E-rings (note 1)
- pop rivets (note 2)
- rivets (note 2)
- clevis pins w/cotter pins

Note 1: I've found at mcmaster pins "Grooved Headless with Retaining Rings" and "Grooved with Retaining Ring" (with head), but they don't have ones short enough for this application. Shortest appears to be 0.500"overall with 0.406"usable. Anyone know where I can get shorter ones? (with usable lengths around 0.200")

Note 2: For standard or pop rivets, placing a thin slotted shim in the stackup during riveting, then working it loose, should allow ease the clamping force of the rivet. One hole surely must be oversized to allow the joint to pivot. Haven't tried this before though.

Any ideas on hardware or approach for the low-profile joints is greatly appreciated. Thanks...

 

[btrueblood]

PEM makes a press-fit rotating pin joint (both sides get staked/pressed to bind to the sheet). Very low profile, essentially flush to the external sheet metal, with a shim or washer between the sheets.

http://www.pemnet.com/fastening_products/pdf/sfwdata.pdf

 

[MechyMech]

Wow, that's slick! Thanks much...

I can't have the drag created by the wave washer, but it looks like it's not needed for assembly. Even if it were, a slotted or 2-piece shim could be used and removed after assembly.

Do you have personal experience with these? How do you like them?

Thx again.

 

[handleman]

Not sure about their inch size range, but in metric you can get precision pivot pins with retaining rings down to 2mm diameter x 5mm useable length.

-handleman, CSWP (The new, easy test)

 

[btrueblood]

Mechy,

I've seen the little sample piece and played with it in my hands. For a lightly loaded linkage, it seems like a good fit. I've used the same mfgr'.s threaded inserts and had good success - never had the inserts punch out from the sheet when they were properly installed. I'm in no way affiliated with them, just like the stuff they make. Good luck!