Sir Brett . . . . .

After an initial observation of that 26 units hinge assembly, I then made a blow up of it, incorporating digital enhancement, to be able to scope it over, ever so more closely.

I have placed a second copy of the hinge down below for your confirmation of that area which I have red-dotted in what . . . it does seem ? . . . to be the subtle outline of one of the two metal portions side by side.

Thereby, in reality, the unit is being made with 3 laterally sliding / rotating sections, with one units [ A ]extreme end, then being coupled into the lids support arm.

Now I ask you, doesn’t one consider the assembly akin to a scaled down mechanics of the hood mechanism of an automobile.

It is being constructed in a small area footprint, but performing high level spring counterbalancing of a somewhat HEAVY weight, exacerbated by the close in pivoting axis of the top covers support arm.

To me, it seems like the only missing thing on your unit is the weight counterbalancing / tensioning spring.

In an initial overall look at the support mechanism, I was first considering there having been the utilization of a single . .or two . .turn loop of a HEAVY gauge spring (1/8 in tempered spring steel) with its 2 straight end extensions that snapped into
holes on the hinge assembly. . . . however, no strategically located holes were seen.

I see the unit constructed as 3 pieces A B C and the top cover hinge arm in the form of [ARM] with its movement between closed to open in making a swing between the yellow marked up slot assigned as C----O reference line at the top.

I see what seems to be four compression contact arc areas, left from spot weld joins at the (4) X-Red circled areas markups.

Then there is the rotational pivot point axis of the whole hinge which is then being designated by the mark up of “ Pivot ”.

That now leaves the two fold out tabs marked in AQUA rectangles, marked as #(1’s), for them serving as restraining stop tabs in the limited movement of section B, which can move upward, until it is stopped at the FUSCIA mark.

The, [ 1 ] tab at the bottom can move upwards until it hits the very bottom of the [A]
rail portion.

The whole hinge assembly seems to be mounted to the cabinet top via the two ? ? ? 8/32 - - -10/32----10/24 screws which seem to pass thru 2 (S-mark up) ordinary hex nuts of ¼ - 20 /---5/16----or 3/8 inch hardware gauging, with them being
used as spacers ? ? ?

NOW . . here is where your mechanical shortcoming seems to be, in looking at the enhancement of the [P] reference area, I seem to perceive an edge burring of that hole and possible ? a threading being inside of that [P] designated hole.

Look across the way to the companion P’ that I have made and that fold out strip from B section. It appears to have a darkening about ¼ down from its top end.

Wonder if THAT marking / discoloration could be the end result of a past times springs coil end link, abrading / chafing that area with its timely movement.

Now, in the whole perspective of its installation, how about visualizing a tensioning spring being used between that P’ tab and over to the [P] area where that vacant hole is located.

At the [P] area hole, consider a bolt being passed thru it and, with the left side of the bolt accepting the other end coil link of that mentioned tensioning spring that was coming over from P'.

More specifically on that bolt . . . possibly being a 1/4 -20 ? ? ? . sizing.

BOLTS . . . .One sees totally threaded bolts and when moving in to the LONGER lengths, there is a tendency to NOT thread the FULL length of the bolt.

Sooooooo . . . if one was to select a bolt of that category, it would then be possible to opt for the cutting off of the unthreaded end to leave a 3/8---3/4 unthreaded stub.

That stub should then permit the drilling in of a 1/16 hole thru it, then the use of a Dremel cut off wheel to permit the narrowing down of the end of that shaft down to an ~ 1/8 in width.

That should then permit the entry of the end link of the coil spring, with the additional capability of that end coil link, now being able to pivot up and down a bit.

Of course, in using this manner of construction, there would NOT be any threading used within the [P] hole , instead, the use of a friction washer / nut being used on the resultant threaded end of the bolt.

Tightening up the nut on the bolt . . . fine tunes in the tensioning springs degree of engagement.

There is then the probable of use of a second back up lock/nut for holding of that final
adjustment.

That only leaves the finding of that tensioning spring aspect, and with my having seen the LARGE metal cabinet at A True Value / ACE type of FULL (read as stock) Service Hardware Store, Egads, they must have 500+ different variants of springs.

If that spring is then installed and properly tensioned up . . . the pull on the spring
should be BELOW the pivotal axis shown and it then will attempt to bring the bottom [ 1 ] stop up against the bottom of rail [ A ] .
That is IF there was not the downward pressure of the pivoting [ARM]on the ‘C’ rail from the weight of the cabinet top.

BUT this upward lift DOES facilitate the raising of the top lid, and is then even further enhanced / multiplied as the attack angle of the arm up at the O------C slot is further decreased. Eventually, the angle decreases and support of the lid is accomplished.

Mechanically akin to the temporary use of a broom stick to hold up the lid of an automobile hood, too much of an angle and you are out of luck, but have that angle at an almost a vertical and you are in business . . .(‘til the time, you then accidentally brush against it ! )

On the reverse situation, in the closing of the lid, the counterbalancing of the spring mechanism changes an abrupt closure of the lid
(WHAMMM !)
to a . . . . .
whoosh .

73's de Edd