Sunday, January 22, 2012

A Kitchen Garbage Pail Repair

This kitchen garbage pail would be quite decent if it weren't such a piece of wreckage.

It has two problems; the foot pedal for raising the lid is inoperative, and the plastic inner pail's bottom is a ruin.

Here's a view of what's at fault in the foot pedal linkage.

The fulcrum-point for the chrome plated crank rod that the pedal acts on is torn out. Pedal motion is lost to pushing up the torn plastic. I can repair that with a steel strap across the top of the fulcrum-point. (The other 'rod' in the photo is a screwdriver shank that I wedged in there to hold the plastic apart to show the fault better.)

The ruined plastic pail bottom will be more work. Here's a view of it.

My wife wasn't very forthcoming about what happened there, and I didn't press the issue. While I don't subscribe to the theory that 'ignorance is bliss', the fact is that I don't need to know everything. Some things just are as they are, and I can deal with them fine without knowing all the gruesome details of what brought them about.

Anyway, the first order of business is to get the lid off so the thing will be easier to work with. That's just a matter of spreading the bail at the back that serves as the hinge pins.

With that freed, the vertical linkage rod is easily disengaged and the lid can come away.

And not only does the lid come away, but it turned to be not difficult to separate the base ring with the foot pedal mechanism from the canister. That really simplified repairing the fulcrum. Here's a view of the fulcrum-point back in good order.

That's a 2 1/4" length of 1/2" wide mild steel flat and some 8-32 fasteners and washers. Now the foot pedal will raise the lid again as it's supposed to, although the hinge/lever affair attached to the lid could stand some attention. Here's a view of that.

The pivot points are just holes in thin plastic -- that's not going to last. The crank that lifts the lid is operating with a very short moment arm,[1] so there's considerable stress on the pivot points whenever the lid is pedalled open. As it turns out, 1/4" eyelets[2] fit the holes, and will make pretty good 'bearings' for the 4mm diameter rod that the hinge bail and crank rod are made of, like so.

I'll grease the rod ends at final reassembly, and I'll have a long-lasting hinge/crank mechanism.

Next up is to repair the outrageous damage to the bottom of the plastic inner pail. I'll need to round up suitable material first.

To be continued.

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The Pail Bottom Repaired

Here's a view of the pail bottom repair.

The sheet metal is galvanized steel, just over ten thou thick. I won't hold my breath waiting to win an industrial design award for that, but it will serve. That was quite a challenging and interesting bit of work. I've much more to tell of what was involved in it.

To be continued.

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The Pail Bottom Repair

I had to hack away some of the distorted, protruding stuff with snips, then I laid down masking tape[3] to give me a 'writable' surface for marking a cut-line on. A big coffee tin served nicely as a circle template. I cut away the remaining rough stuff with a jigsaw, and smoothed the edges with a 1 1/2" diameter drum sander chucked in the drill press. All that got me to where I could cut a sheet metal disc and install it with hollow ('Pop') rivets. There are several points about using hollow rivets in a situation like this that I ought to elaborate on a bit.

Hole Size

I was using 1/8" diameter rivets, so one would expect to use a 1/8" drill, but that's actually not such a good practice in some cases.

When you drill 1/8" for a 1/8" rivet, you get a borderline interference fit for the barrel of the rivet. Inserting the rivet can be a bit of a struggle. What you want to use is a drill just a tiny bit larger than 1/8" (0.125").

A No. 30 drill is 0.1285" diameter, 0.0035" greater than 1/8". Drilling No. 30 rather than 1/8" makes the work go much more smoothly.[4]

Backup Washers

When clinching a rivet in material like fabric or leather, you have to use backup washers to give the rivet's barrel an unyielding surround to clinch against. The same applies for a thin sheet metal and plastic lamination as I was working with here. The materials are too yielding to be riveted successfully without backup washers.

Backup washers are just flat washers with a bore diameter that just fits the barrel of a rivet. The 1/8" size is readily available; the other sizes not so much. I make the other sizes the odd time that I need them from undersize washers that I bore out to fit. This post shows the method I use to make 3/32" backup washers.

Join Tightness

When joining thin material with hollow rivets, it's essential that the lamination be held tightly together as the rivet is clinched, else the resulting job is likely to be a be a poor one. The following photo shows a good and a bad rivet installation.

The join at the right is as it should be -- tightly squeezed together. The join at the left is near-worthless -- the materials aren't squeezed together at all. The process of clinching the rivet will not draw things together on its own; the join has to be forcefully held together as the rivet is clinched.

To get the outcome shown at the right, use a small (3/16") socket wrench as an 'anvil' on the clinch side to support the backup washer while providing clearance for the rivet end -- that makes it possible to bear down with the riveting tool and ensure a good join.

To apply that method to the bottom of the pail, I had to rig a way to support the small socket wrench in space far enough out to reach inside the pail. Here's a view of how I did that.

It was a bit of an awkward arrangement, but it did the job for me and got me a sound riveting job.

Once all the riveting was done, I 'caulked' all the seams and small gaps with clear silicone sealant, so the thing now would even hold water if it needed to.

Anyway, the pail is now fully repaired and ready for delivery back to the kitchen. Far better that than delivery to the landfill.

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[1] To oversimplify a bit, in any arrangement where something is rotated by a crank, the effective length of the crank is the 'moment arm'. As with everything, one could make a career out of learning all that's associated with the term 'moment arm'.

[2] It's not at all clear to me how Canadian Tire arrived at the 1/4" dimension for these eyelets.

The Flange diameter is 5/16"; the barrel diameter is just over 3/16". Nowhere in these eyelets can I discover a dimension equal to 1/4".

Be that as it may, they're just what was needed.

[3] Masking tape is a great lay-out aid for surfaces that are difficult to mark. I always have a roll of it handy, and I use it often for such purpose.

[4] The same applies to the other sizes of hollow rivet. Here's a list of nominal rivet sizes with their corresponding, slightly oversize drills.

3/32" (0.09375") -- No. 41 (0.096")

1/8" (0.125") -- No. 30 (0.1285")

5/32" (0.15625") -- No. 22 (0.157")

3/16" (0.1875") -- No. 12 (0.189")

A slightly oversize hole is often, but not always, desirable. A good method is to drill nominal size first, then if rivet insertion proves to be difficult, enlarge the hole with the appropriate number size drill.

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