Charging Station

After a few years of testing and a few changes to the original design, the time came for the final version:  we got more devices and the prototype wasn’t big enough.

I made the final version from canarywood scraps I had lying around.  The space on the wall allowed me to fit a thirty inch wide shelf to hold the devices.  Hopefully this will suffice for all the devices the household requires.  To make the shelf I glued together two pieces of canarywood, drilled holes at the base of each slot, and finally cut out the thirteen slots with a hand saw.   Shaping and smoothing these slots and, finally, sanding them was extremely time consuming.   My saw cuts weren’t precisely tangent to the holes I drilled, so those transitions all needed attention.  I had to round over all of the top corners.  Finishing end grain is always more work, and this design creates a lot of exposed end grain that is hard to get to.   Is there a way to change the design to make the build easier?

I glued a continuous strip of the EPDM rubber along the slots. I punched a 7/64″ hole and then cut a slit leading up to the hole.

My final selection for the cable gripping rubber was EPDM rubber, 1/16 inch thick, and 40A hardness.   I originally used 1/8 inch holes.  The 1/8″ holes are great when they work, because they grip the cables tightly, but they are too small for some thick USB cables.   I had to increase the size to 7/64″ to accommodate these fatter cables.  This does mean that the rubber almost never actually grips the cable.  It just confines it.  For my prototype I glued on the rubber using epoxy, but the rubber peeled off in some places.  In looking for an alternative I found Nexabond, a slow curing cyanoacrylate adhesive, which seems to dissolve the rubber and create a very strong bond.  Nexabond is now sold as Rapid Fuse.  I used the variety marketed for wood.   I found that it’s not possible to clean it off the rubber, so I had to be careful when applying it to avoid excessive squeeze out, but to use enough to secure the rubber all the way to the edge of the wood.

The rubber loosely grips the cables. The USB plug can rest in the space in front of the rubber in each slot.

The cable management box was hard for me to design.   My original design left the wrapped cables exposed.  I found that users often leave the ends of the cables dangling over the cable management box rather than securing them above on the shelf.  The dangling cables combined with the exposed wrapped cables form a very busy visual image, and it is hard to identify the loose ends that you may want to plug into your dying device.  In the prototype, I added a cover secured with a pair of magnets.  Maybe this approach could work somehow, but two problems would need to be addressed.  I was never sure where to put the cover after removing it, and I found it hard to close it because the cover would snap suddenly into place and I had to make sure it didn’t capture any cables over its whole width.   However, a normal hinged door would extend 15 inches, which seems unwieldy.  I  considered doors that swiveled down, but one of them would collide with the USB hub.  Finally, after talking with a friend about my design challenge, I revisited the idea of a hinged door and hit on the idea of a door that folds in half.

Two doors, each with a hinge in the center so they can fold in half.  Note the continuous grain lines across all four parts of the door.

The center section opens first.

 

If necessary you can open the second section of the doors, which have their own separate magnetic latches.

Selecting hinges was another challenge.   I hadn’t been planning to spend so much on hardware for this project.  The hidden hinges in the middle of each door are Soss Invisible hinges, and I ended up using Brusso brass butt hinges to mount the doors to the frame.   The Soss hinges come in a brass finish, which would have blended better, but when I found these on ebay for half price I decided I’d take them.  I love magnets, but getting the right magnetic force seems to be an ongoing challenge.  In this case, I mounted 3/8 inch magnets using screw in cups.  The resulting magnetic force was excessive.   One solution is to recess the mating washers farther into the wood (to increase the distance), but once the magnets are installed it is impossible to remove them.  In fact, once the steel cups are installed I find that they fit so tightly it is impossible to remove them, even before screwing them in.  Covering the magnets with high friction disks provided some extra separation that weakened the magnetic force enough to make the doors useful, though they do still stick shut a little bit more strongly than I would prefer.

For securing the cables I use a pair of 3/8 inch dowels and wrap the cables in a figure eight fashion.  I have seen quite a few gizmos for managing cables and, from what I can tell, none of them works as well as just wrapping cables in a figure eight; the cables don’t tangle, and you don’t need a special device.  Try it with your earbuds.  A strip of velcro holds each cable in place.  I used a two inch wide strip of white velcro hook material for the back of the box and I secured the cables using 3/4 inch black loop strips.   Reportedly the loop side of the velcro wears out first, so I used it in the more easily replaceable location.   Along the top edge of the box I made small cutouts for rubber cable holders.  These hold the cables up if you open the box.

The doors open all the way out and can tuck up against the wall at the sides. We secure the cables using figure eight wrapping onto two posts, with a strip of velcro to hold them in place. I chose white velcro for the background so it’s easy to see the black velcro that holds down the cables.

Installation of the Soss hinges requires a weird shaped mortise 3/8 inches wide with rounded ends and a deeper center section.  I drilled this using a centering drill guide and a brad point bit.  I had some trouble with hole depth and later found myself trying to deepen parts of the mortises with chisels.  But eventually I got the mortises cut.  For hardware installation I chose to use machine screws, both for the Soss hinges and the Brusso hinges.  Many people recommend machine screws for wood, especially when the screws are small and short.  I thought I would be installing and removing the screws many times, so this supported my decision to use machine screws.  In the case of the Soss hinges, the fit in the mortises was very tight.  They weren’t going  anywhere.  It was hard to take the hinges out after test fitting them in the holes.  Strength of the screws wouldn’t have made a difference.  And since it was so hard to install and remove the hinges I ended up doing it only one time and doing the finishing with the hinges installed.   I also broke two 4-40 taps cutting the threads.  In retrospect, I think this happened because I pre-drilled holes that were a size too small.

I installed the Brusso hinges using chisels and a router plane, a process that I enjoyed much more than drilling with a guide.  And I didn’t break the tap when cutting threads for 2-56 screws.  Using machine screws here seemed like the right thing to do.  The hinges didn’t stay in their mortises from friction alone like the Soss ones, and the use of machine screws enabled me to use longer screws on the frame and shorter ones on the door without having to buy two boxes of screws.  My wire cutters cut easily through the brass machine screws so I could make the lengths I needed.   I did end up installing and removing the hinges several times.

One disappointment is that the Soss hinges have a little bit of slop in them.  I’m not sure if I loosened them up somehow while prying them out of their mortises after test fitting, but if I close the doors without trying to force them upward they don’t create an even gap.

Uniform gap between the doors.

Uneven gap between the doors, narrower at the top.

 

The final component of the charging station is the hub holder.   As long as we charge devices using cables, the rest of the ensemble can remain unchanged, but this hub is the part most likely to change in the future.  It already changed: I have a new hub with more ports.  I didn’t want to work too hard on this part so I used a simple design that is very easy to make and somewhat adaptable—unlike the prototype it can at least accommodate charging hubs of varying length.  This design requires no complex joinery since the wood grain all runs in the same direction.  I tried to shape it to echo the curves of the shelf at the top, with the the back section sticking out to the sides for easy screw mounting.

Very simple hub holder design with open ends.

I think overall this is a great design for a charging station. It only uses wall space, not desk space, and keeps all our devices out of the way. I’m happy with the final result. The only thing that could be improved is the location of cable holding holes in the rubber. These holes are about an inch behind the front of the slot, and this is a little bit too far. Three fourths of an inch would be better.

Bedroom Chest: First Steps

chestdesign1My latest big project is a chest to go at the end of the bed. We had a bench there, but piles of clothing and linens covered its surface, and hence I could never actually sit on it. Storage in a small, old house is scarce, so I decided to replace the bench with a storage cabinet. The standard chest at the end of a bed opens on the top. If we had such a chest we’d never be able to open it, so my design features sliding doors and drawers. The top remains available for piles of clothing, and a backsplash prevents the piles from dripping off onto the bed.  The current design appears above, though I still have some uncertainty about the drawer widths. Work has been proceeding at a glacial pace over the past couple years.

This cabinet will be made out of quarter sawn hard maple. I had difficulty buying quarter sawn maple. I found a guy with a chainsaw who sold me a small lot cut from one log. It had some very nice boards in it, some up to 11 inches wide, but the boards were only 46 inches long, which won’t work for a four foot wide cabinet.   Nobody has 11 inch wide material; most online vendors said their boards were four inches wide, which wasn’t appealing. I finally ordered some wood that was over 5 inches wide with some nine inch boards.  The length ended up being seven feet, the worst possible length for my four foot wide cabinet.   As I began to work the wood I found that the guy with the chainsaw delivered nice looking, wide boards, but they were pretty badly twisted, so jointing the lumber by hand was a lot of work. But the real lumber yard delivered wood that was riddled with cracks across the face of the boards. I’m guessing this is the drying defect known as “honeycombing.”

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This board has several cracks across its surface that you can see if you enlarge the image.

For the panels of the sliding doors I selected some spalted quilted maple material. This too, turned out to suffer from drying defects. I had the option of returning it or working with it and ended up deciding to fill the cracks and move ahead, rather than trying to locate a different panel. I tried to plane the material slightly to decrease the size of the cracks…but they got bigger instead. I chose to fill the cracks with black epoxy, hoping that it would match the spalting lines and blend in. It seems like most people think this looks fine, but I’m less enthusiastic.

As always, the process of selecting wood for different parts of the project went slowly. I began by choosing wood for the sides because I wanted to use the short, wide pieces there. Then came the task of selecting rail and stile material. One thing I love about quarter sawn wood is the ray flecking, but for the rails and stiles I wanted it to be really more rift sawn: straight grained without fleck to provide a good frame to the busy internal panel. Then it was time to get to work. I cut the grooves using my Veritas plow plane.

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Note the fuzzy tear out towards the back end of the plane on the front edge of the groove.

I had a lot of problems with tear out while making these cuts. Part of the problem was user error: if I tipped the plane even a bit it could rip out a chunk on the side wall of the groove. But because the wood is quarter sawn, the edge, where I’m cutting the groove, has badly behaved grain. I did find that the front edge of the groove came out worse than the back one every time. I think this is because I can tip the plane toward me but the fence prevents me from tipping it the other way. I switched my reference around and referenced from the back of the panels to get the best looking show side. But it seems that ultimately to get a nice groove in material with reversing grain you have to precut the groove edges with a chisel.

The spalted maple panels were very porous, and when I started applying shellac the liquid quickly vanished into the wood. When the finishing was complete I discovered that the wood had warped considerably. I tried to flatten it by putting some shellac on the back. This helped a bit, but the panel remained warped. People use to say you needed to finish both sides of a panel to prevent warping. Then this idea got attacked as a myth. I wonder if I had finished both sides exactly the same would the panel have stayed flat and made the assembly easier—it’s more difficult to squeeze a warped panel into a groove.

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This panel was flat before I applied shellac. Note the shadow of the straight edge on the wood.

I cut mortise and tenon joints to hold the panels together. The joints weren’t my best fitting. I had been wondering whether to drawbore or not, and decided I had better drawbore.  A drawbore is a joint where a peg is inserted through the joint but holes are misaligned so that the peg has to bend a little bit and it strongly forces the joint together.  Based on Schwarz’s recommendation I offset my 1/4” drawbore holes by 3/32” for my first door. I made riven white oak pegs using a dowel plate and cut a taper at the starting end. When I went to hammer the pegs home, though, I had some problems. I had tested the joint with drawbore pins and it seemed to be OK. But the pegs splintered inside the work, with only part of the peg emerging on the back side. Additionally, they forced the joint to come together crookedly so that the door didn’t lie flat on the bench. When I remembered to put glue on the peg it worked a bit better, but I only remembered one out of four times to do that. Application of a mallet and clamping the door flat onto the bench seemed to correct the problem.  The pictures below show four pegs from the back.  The top left is a peg that was lubed with glue and went through neatly.  The bottom left peg opened a gap, the top right peg was somewhat mangled and the bottom right beg lost a quarter of itself somewhere in the hole, leaving a gaping space.

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For the second door I adjusted the procedure. I used a 1/16” offset and I put the pegs into a cup of glue so I wouldn’t forget to lubricate them with the hide glue I was using. This door went together much more smoothly, without the problems I had on door number one.  Some of the pegs look bad on the back of the door, but as these are sliding doors, nobody will see them.  The front pegs look good.

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The last issue is securing the panels so that they stay centered in the groove if the panel shrinks or expands.  I’ve seen special foam balls sold for this job, but that solution wasn’t appealing.  It sounds like a standard solution is to hammer in a nail at the panel center but I realized I wasn’t sure how the nail should go in.  If I tried to angle it then the nail would almost completely miss the panel.  I had some 1.25″ cut nails handy.  I trimmed them to be about 1/2″ long, oriented them correctly to the grain of the frame and tapped them into pilot holes.  Nothing split, and hopefully they actually pierced the panels, so they should do the job.  I wonder if a dab of glue would have been an easier solution?  Would that hold well enough if I can only squirt it into an already assembled panel from the outside?

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Finished door panels. Note that the rails are overly long and still need to be cut flush with the stiles.

Now it’s back to lumber selection. I need to select boards to use for the top of the cabinet, and then see if I have enough wood to make the dividers. I am thinking that I may have to glue up three foot lengths into a four foot long panel butcher block style to use the lumber I have on hand.

I haven’t quite figured out the proportions for the drawers.  Here is a subtle change in the drawer proportions.  Which is better?

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Drawers at 2:1 ratio. Center drawer 9″ wide.

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Drawers at 5:3 ratio. Center drawer 10.5″ wide.

Another outstanding design question is: can I do something with the drawers to unify them with the much darker spalted panels on the sliding doors below. Perhaps spalted maple drawer pulls would have this effect?

Magnetic Wood and Magnet Selection

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We find hanging utensils in the kitchen to be the best storage method; most of the vertical space in the kitchen is covered with kitchen equipment.  However, the sides of the cabinets above the sink had nothing hanging on them! This problem demanded a solution. Last time I did a project like this I made pegboard, but pegboard is inflexible both in spacing and in the type of hooks available. This time: magnets.

I started with 1/16″ thick sheets of steel, which I covered with oak veneer. Technical support at 3M advised me to use spray adhesive, so I adhered the veneer with Super 77. The trim on the cabinets conceals the side edges, but not the bottom edges, so I epoxied small oak strips along the top and bottom to hide those edges and blend into the cabinetry.

Once I had the veneered steel screwed to the cabinets I realized that I couldn’t find magnetic hooks suitable for hanging kitchen tools.  I could hang a few things with Super Fridge Magnets and some things with the Standoff Magnetic Tool Holder, but most of the things I wanted to hang would require a different solution.

These  magnetic bases have a protruding threaded rod. To transform them into hanging rods I attached standoffs, metal tubes that are threaded on the inside. At McMaster I could buy standoffs in a variety of lengths, though for some reason the stainless steel ones were twice the price of aluminum.  To get a finished look I found two options. McMaster sells elegant end caps for the stand offs, but they are expensive—more than the shorter length standoffs. You can see them below in stainless steel (which is the same price as aluminum). I also bought a box of stainless fillister head machine screws which make reasonable looking caps for the standoffs at just pennies a piece. This scheme enabled me to make hooks as long or as short as needed. I worried that the absence of a hooked end might allow tools to fall off the wall and plunge into the sink, but that hasn’t been a problem for most things.




The one exception is the red funnel which slips right off of a rod. A simple solution is to insert a screw that is longer than the threaded rod so the screw head acts as a stop.

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Hanging this funnel required a trick to keep it from sliding off the rod.

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We also have some spatulas whose hang holes do not admit a 1/4″ shaft, and the threaded rod does not come in a smaller size that is compatible with the magnetic screw bases. I attached a 1/2″ diameter magnet to a small piece of wood and inserted a 3/16″ diameter stainless rod to create a suitably sized hanger. It didn’t work: I planned to hang four spatulas from this rod, but the hook would slide down and fall off the wall if I loaded it with more than two of the utensils.

Next I tried polymagnets. I recently learned about these magnets where the magnetic field varies spatially across the magnet to produce different effects. They make several types of magnet pairs, including the spring, latch, and centering magnets. For this task I was testing the “attach” type magnets, which supposedly concentrate the magnetic field closer to the magnet so that the magnet grips more strongly. I had on hand some 1″ diameter, 1/32″ thick “attach” magnets as well as two 1″ diameter, 1/8″ thick “attach” magnets (one with a mounting hole and one without). The 1/32″ thick magnets have the same volume of magnetic material as the 1/2″ diameter, 1/8″ thick magnets I used to make my unsuccessful hooks. Another observation is that two of the 1/32″ magnets got stuck to each other at one point and they were extremely difficult to separate. It was impossible to slide them apart like one usually does to separate rare earth magnets. I had to separate them using a wedge, something I’ve never had to do before, even with larger 3/4″ diameter, 1/8″ thick magnets. These magnets are not weak.

I glued a 1″ diameter 1/32″ thick “attach” magnet to a small piece of wood and again inserted a length of steel rod.   This new hook was very weak and slide right down the wall.  I glued on a second “attach” magnet, and now it could hold the weight of 3 spatulas, but not 4.  When attached to the refrigerator, however, the hook would hold the necessary weight—the four spatulas I wanted to hang weighed about a pound in total. Note also that the rolling pin weighed more than a pound and yet was easily held to the veneered steel by one hook with a 1/2″ magnet.  The hook with two polymagnets has double the amount of magnetic material,  but it fails to do the job.

I abandoned that design.  The hanging rod in my original design was below the magnet instead of centered over it.  The wood was 1/4″ thick.  The magnets are 1/8″ thick.  I didn’t think the remaining 1/8″ of wood sufficed to support the hanging rod.  The off-center hanging rod seems to make the shear hold weaker because the load on the rod can tilt the magnet away from the surface.  I made the centered rod design (right) by using a magnet with a screw mounting hole in the center. The rod goes through the screw mounting hole, and I filled the space with epoxy to ensure that the rod would be well supported.  This new hook holds all four spatulas without any difficulty.

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Spatula hooks. The bloodwood hook on the left with a conventional half inch magnet has the hang bar off center and can hold only two spatulas. The chechen wood hook on the right, with a one inch polymagnet and centered bar easily holds four spatulas.

 

Measuring magnets

So what was going on with my magnets? I tried to measure the capacity by filling a bag with weights (dried beans) and determining the point at which the hook began to slip. This was kind of messy and I didn’t feel very confident about my accuracy, but I did find that the hook with the two polymagnets held 4.25 lbs on the refrigerator and only 1.1 pounds on the wood covered steel. One important factor in this sort of holding power is friction. Is it possible that my finish on the wood was too slippery? Or did the magnets simply hold with less strength on the wood.

forcesheer_smTo get to the bottom of this I purchased a Chatillon force gauge cheaply on eBay. This device measures force in pounds and enabled me to measure the pull force to detach magnets from surfaces as well as the shear force (the hanging load that would cause the magnet to begin sliding). Measuring shear force is relatively easy: I attached a loop of string to the hook and pull downward with the gauge.

Measuring pull force is a bit more difficult. I used a strip of Tyvek and placed the magnet over it. This means that the magnetic force is decreased by the extra distance created by the layer of Tyvek. It also is difficult to be sure that the pull is applied directly perpendicular to the plane of the magnet, and I suspect that an angled pull may lift the magnet more easily.

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Measurement of the magnets resulted in a complicated set of data with some inconsistencies. I tested magnets on two surfaces, the refrigerator and the wood veneered steel. If the pull force of the magnet is F then the shear force is supposed to be equal to σF where the coefficient of friction, σ, depends just on the surfaces. Lee Valley sells two self-adhesive high friction materials. One is their High Friction Disks, specifically marketed for use with rare earth magnets. The other is the Super High Friction Tape. When I ordered the polymagnets I also included some Traction Tape to use with them. My hook that wouldn’t support a pound of spatulas gave the following test results

Two thin Polymagnets glued to wood
Pull Force (lb) Shear Force (lb) σ
Fridge Wood Fridge Wood Fridge Wood
Bare magnets 5 1 1.5 0.25 0.3 0.25
Friction disks 3 0.5 3.75 1 1.25 2
Friction tape 1.75 0.5 5.5 2 3.1 2
Traction tape 4.25 1.1

When placed on the refrigerator the pair of 1/32″ thick 1″ diameter “attach” polymagnets gave a respectable pull force, five pounds with nothing but a sheet of Tyvek separating them from the refrigerator. The friction disks are only 0.022″ thick and the friction tape is 0.016″ thick. But this small extra separation from the metal created by the friction disk or friction tape reduced the pull force considerably to 1/3–1/2 of the original amount. Despite this decrease in pull force, the shear force increased. Without a friction tape of some kind the coefficient of friction was around 0.25, but with friction tape it rose as high as 3.1. Note that for this hook the high friction tape gave the best result: with two pounds of holding power even on the wood it would have sufficed to hold the 1 pound load of spatulas.

Why is the magnetic force of attraction to the refrigerator so different from the force of attraction to the veneered steel?  And why can’t two magnets hold on as strongly as a single magnet hook? Is the high friction tape really so much better than the other tapes?  I made the same measurements of the screw bases:

Small (16mm) screw base magnet
Pull Force (lb) Shear Force (lb) σ
Fridge Wood Fridge Wood Fridge Wood
Bare magnet 4.5 3.5 2.75 1 0.61 0.28
Friction disk 2.5 2.75 2 2 0.8 0.73
Friction tape 2.5 1.5 2 2.5 0.8 1.7

The strength of attraction to the wood and the fridge are closer together in this case, and the shear forces are very similar. In some cases the attraction to the wood is higher than the attraction to the fridge. This result is quite different from the previous one. One anomaly stands out: the shear force for the bare magnet on the fridge is very high. I noticed that when I dragged this magnet on the fridge it was scraping little white bits of the vinyl off, so I think that rough edges of the magnet were digging in and providing a huge boost to friction. I tried sanding the base but it didn’t significantly change the results, though. (Maybe I didn’t go far enough.)  Another anomaly is the high σ value with friction tape on wood; I have no explanation for this one.  These screw bases feature a 1/2″ diameter magnet that I assumed was 1/8″ thick, which would mean they have half the magnetic material of the two polymagnets I used above, and yet the holding power on the wood is higher. Moving on to the larger screw base:

Large (20mm) screw base magnet
Pull Force (lb) Shear Force (lb) σ
Fridge Wood Fridge Wood Fridge Wood
Bare magnet 4.75 6.25 1.5 1.25 0.3 0.2
Friction disk 3 4 3.25 4 1.1 1
Friction tape 3 4 3.5 4.5 1.2 1.1

This larger base clings to the fridge with greater strength than the smaller base, and on the wood it is even more powerful. The shear force strength is also somewhat stronger on the wood. So a bigger magnet is gripping more tightly and giving more holding power, right?

Wrong. Both screw bases have the same sized magnet.  The larger base has a plastic ring encircling the magnet.

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I disassembled one of each hook and found that the magnets were slightly bigger than 1/2″ in diameter (0.54″) and at 0.15″ thick, they were thicker than expected.  And they were indeed the same.  These neodymium magnets come in different grades with different strengths, but I tested the pull force and found no difference: both held to the fridge with 2 lbs and the wood with 2.5 lbs.

So apparently the difference in magnetic forces depends on the way the magnet is enclosed. I measured the pull force for a bare 1/2″ magnet and got 1.5 pounds for both the fridge and the wood. When I put the magnet into a steel cup the force rose to 3 pounds.  The observations above suggest that I might get even more force if I had an oversized cup surrounding my 1/2″ magnet.  So I tried inserting my 1/2″ magnet into a base designed for a 5/8″ magnet.  The force rose slightly to 3.25 lb on either the wood or the fridge.  I didn’t see the striking increase I got with the magnet base on the wood.   I tried a larger 3/4″ magnet cup and the force decreased slightly.  The only curiosity was that when I inverted the magnet cup, so the magnet was backed with steel but not covered on the sides, I saw an increase in the attraction to the wood to 3.5 lb, while the attraction to the fridge declined to 2.5 lb.

What conclusions can we draw from these measurements? Clearly backing the magnet with steel makes a big difference.  It seems like it’s hard to predict the attractive force of different configurations, so measurement may be the only way to know what will happen. The thin polymagnets did not adhere well to the wood. Perhaps their magnetic force is shorter range than the normal magnets, and the veneer is thicker than the vinyl that covers the refrigerator. This behavior doesn’t offer any obvious advantages, so I don’t plan to use those magnets again.

The coefficient of friction for the bare magnets came out consistently around 0.2–0.3, and inserting friction tape of some kind improves this to about 1. The small gap created by the friction tape significantly reduces magnetic pull, but you still get more shear force. Don’t skip the friction tape if you care about shear loading! But I didn’t get consistent friction coefficients as claimed by the physics books. My measurements were all over the place, ranging from 0.73 up to 3.1. Why the big spread? The friction coefficient is supposed to be independent of contact area, but I’m observing higher values when I have more contact area and the lowest values when contact area is the least. The high friction tape seemed to perform better with the polymagnets, but not at any other time, so I can’t identify a winner among the friction tapes.

Tilting can play a role in limiting the load a magnet can hold on a vertical surface. These magnetic hooks fail  not by sliding down the fridge but by tipping forward: the failure isn’t in shear.  I tested my wooden hooks (pictured above) on the veneered steel surface.  The bloodwood hook could support 1.75 lbs of force at the base of its 1.5″ rod but only 1 lb of force at the tip.  The chechen hook has a four times bigger magnet and could support 5 lbs at its base, but again only 1 lb at the tip of its longer 2.125″ rod.  When the load was at the tip it  usually failed by tilting, or it vibrated as it moved.  Perhaps even when magnets are sliding down the fridge they are tipped forward, compressing the friction tape at the bottom and moving the magnet away from the fridge at the top.

I’ll finish with some measurements of a few other polymagnets. I have a 1″ diameter, 1/8″ thick “attach” magnet. It has a marked side that I thought was supposed to be the active side. Pull force on the fridge was 7 lbs on the active side and 13.5 lbs on the reverse side. On the wood I got 3 lbs on the active side and 5.5 lbs on the reverse side. I also have a polymagnet with ring shaped magnetic regions designed so that a pair of them will center on each other. This magnet is 3/4″ in diameter and 1/8″ thick. With the marked side to the fridge it had a 9 lb pull force and with the reverse side only 4 lbs. On the wood, this magnet gave a pathetic 2 lb pull on the active side. A normal magnet of the same dimensions clung to the fridge with 2 lbs of force, and the wood with 2.5 lbs. The 1/2″ magnets I tested above are only 44% as big and yet 75% as powerful in this situation, so for hanging stuff on the fridge, at least, save money and use the smaller magnets—or spring for that centering polymagnet.

 

Draining Rack


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We have various soaps next to the kitchen sink, and I noticed that as a result, the sink area was always wet, which led to mold growth. To address this problem, I tried building a drainage rack out of wood, which I hoped would allow the water to dry and prevent the growth of mold. I’m not sure whether it was helping with the mold, but it turned out to have another problem: the wood itself produced brown stains on the counter.




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Underneath the tray it looks worse.

It seemed that for this project, I needed a different material.  I envisioned something with holes in the top and a sloping drainage tray to send water back to the sink.  Shapeways offered a 3D printed ceramic material that is dishwasher safe and food safe.  It seemed ideal.   So I started designing in SketchUp.  SketchUp is easy to use for lots of things, but I found it tricky for this task.  Arranging the holes in the top proved tricky, tedious, and hard to change once it was done.  The printed object will be nicer with rounded corners and edges, but SketchUp is not very good with rounding over corners. But eventually I got a model done and submitted it to Shapeways.

It was rejected because the walls of the design were too thin somewhere.  After resolving that problem my design got rejected because it wasn’t adequately supported.  But the exact nature of the support I needed remained elusive as I tried to redesign the model to comply with their vague requirements.  Then the ceramic material got discontinued entirely.

Months later I was admitted to the Shapeways pilot project for a new porcelain material. I had to reduce the size of my model to make it printable, but the only hitch I had was failing to meet a minimum size requirement.  So finally, I was able to make the print.

My original design was a two piece ceramic structure with a drainage tray in the base and a top that lift off for cleaning.  This was quite expensive, so in a quest to lower the price, I devised a design with a single ceramic part and a slit to hold a drainage tray.  I ordered a piece of white plastic from McMaster and cut it to size to fit into the slot.

The result is functional and reasonable looking.  I was a little disappointed by the way the glaze looked:  I was expecting a more uniform deep green color.  The long unsupported top span sagged a little bit during fabrication, but this doesn’t affect its function.  The rack has stood up to a couple months of use and has definitely improved the sink area.


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drainagetray4_sm



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Charging Station Prototype

We have enough rechargeable devices that we needed a way to charge them that was less chaotic, that didn’t leave devices on the floor.  I looked at commercially available options, but nothing seemed to do what I want.  So I started constructing my own wall mounting approach.

My idea was to have a shallow shelf that devices rest on, with some mechanism to hold and organize the cables and a box to hold the charger hub.   I thought initially that cables could rest in slots that were narrow enough so that the plug wouldn’t fall through:

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Cables can slip into the skinny slot to hold them in place. The wider part of the slot permits the cable end to stick down when a device is charging.

This approach didn’t work because the cables sometimes pull forward out of the slots.  The next idea was to use rubber to hold the cables in place.  But which type of rubber?  McMaster has an overwhelming number of options, both types of rubber, thicknesses, and hardnesses.   I tested several options:

dsc09092It seemed like the 1/32″ EPDM with a Shore hardness of 40A was promising.  So the prototype looks like this:

dsc00043I realized that velcro alone did not suffice to manage the cables, so I added the cable wrapping posts.  Also it seemed like the EPDM rubber was not holding cables as well as I expected, especially with thicker cables.  So I tried a change in the design with a thicker piece of rubber and a hole to hold the cable.  This seems to work better at holding cables, though it is more difficult to get them in and out.

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The black rubber has a hole punched in it to hold the cable. This does seem to be more secure, though choosing the right rubber is still an issue.

We’ve had this in use for a while now, but one problem I’ve noticed is that the users don’t like to leave the cables secured in the rubber slots.  They prefer to just leave them dangling.  Does this mean the rubber slots are unnecessary?

How can this design be improved?

Couch Cabinet

dsc00014After finishing the Utilitarian Cabinet I said I was going to lay off the plywood for a long while. Events conspired against me: we needed a small table or cabinet to fill the narrow space beside the couch and the remaining walnut plywood was just right for the job.

For this cabinet I borrowed a Festool Domino to make the joints for the case and drawers.  The Domino is a lot nicer than dowels. It can make one pair of tight fitting mortises for alignment and loose fitting holes elsewhere, which makes the joint much easier to assemble and disassemble than dowels.  This cabinet went together without the struggles that we had with the dowel-joined Utilitarian Cabinet—I was able to do it without a helper. The drawers went together very easily as well, and the dominos helped in assembling the miter joints in the pedestal and in affixing the pedestal to the case.

I also experimented with the undermounting Blum Tandem-Plus Blumotion drawer slides, which waste less space at the sides of the drawers.   With the drawer cavity only seven inches wide I wanted to make the widest drawers I could.  Understanding the requirements for these slides proved to be rather difficult. Blum is very bad about posting detailed information, and they also sell different products in Canada than they do in the USA, so Lee Valley has products that are not otherwise available in the USA. It wasn’t immediately obvious to me—though it should have been—that the undermounting slides would have a minimum drawer width. It is not easy to figure out what this minimum width is.  Lee Valley didn’t know, and when I asked Blum USA about the Canadian slides they couldn’t find the answer!  I eventually learned that the Tandem-Plus would work on my narrow drawers as long as I used special “locking devices”.  The undermounting slides waste less horizontal space but they consume over an inch of vertical space.   This led to a problem when I positioned the handle without checking the position carefully and the mounting screw hole hit the drawer bottom.

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See the recess I carved into the drawer bottom to allow me to attach the drawer pull?

When I went to fit the drawers into the cabinet they worked right the first time. This is a huge contrast to my experience with the side mounting slides I used in the Utilitarian Cabinet where I had to spend hours on drawer fitting.  I had a brief problem with it when I did the final test fit and the drawer hit the case.  It turned out I had accidentally pressed the levers that raised the drawer.  Lowering the drawer back to the correct position was very easy.  The finished drawers open and close very smoothly and much more easily than the drawers in the Utilitarian Cabinet, though we’re not sure we like the Blumotion drawer closing action.  Because the drawers are tall and narrow I used the wood with the grain running vertically and I mounted the handles vertically.

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Note the continuous grain on the mahogany drawer fronts.

The corner in which the cabinet sits is not square.  It was necessary to curve the edge considerably to get a reasonable fit.  dsc00021

Kitchen Organization

This post is a round up of small kitchen organization projects, inspired by a few recently completed ones, but including some projects from years ago.

Organize a Bottom Freezer

This one isn’t very interesting as a woodworking project, but might be interesting to people looking for a solution to the problem of organizing a bottom freezer. Our old refrigerator had a top freezer, and I had containers in the door, labeled on the side, and shelves in the freezer space. The new freezer has a big open cavity and a sliding top drawer. How could I use this space effectively? When I looked around online for ideas on freezer organization, I didn’t see anything that looked both effective and efficient.

For the sliding top drawer, my solution is to use these air-tight containers that can be turned sideways and labeled on their sides.
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For labeling I find that the Pentel Wet Erase Chalk Marker works well. It resists water, but can be washed off of smooth surfaces easily when desired (though it mysteriously does not come off in the dishwasher). The only problem is that these particular containers have a rough area on the side, from which the pen does not clean off.

For organizing the bottom some people put things in containers, but this wastes scarce freezer space. I made wooden dividers to partition the big, open space into sections sized to quart freezer bags.

freezebottom

The left side is divided into six spaces. The right side is divided into four larger spaces.

 

I cut these dividers from quarter inch plywood using my band saw, but a jigsaw would work too. There is no need to finish them.  Observe how the dividers fit into the gap in the freezer frame at the far right and left sides.

dividers

These are the dividers for the right side. The top one is cut to match the slope of the back send of the freezer. The lower piece, which runs left to right when assembled, has a small notch to fit onto the plastic divider that came with the freezer.

 

Measuring Cups & Spoons

We have a lot of measuring cups and spoons. Some of them hang on hooks from holes in the handles, but we had a plastic set with no hang holes that I hung using magnets. The nice thing about the magnets was that it was very easy to hang them or grab them. The troublesome thing was that adhering magnets to the polyethylene measuring cups required an expensive adhesive and they would eventually fall off. I got new stainless steel measuring cups and their different shape and increased weight made the magnets a more troublesome solution. So I came up with this approach that exploits the little tabs on the ends of the cups. (However the one cup measure has no tab and requires a little support bar underneath.)

cuprack

This measuring cup rack is angled 45 degrees to the wall. It might be slightly easier to use if it was a bit closer to horizontal.

I attempted to drill the large holes using an expansive auger bit. These tools seem to be plentiful on ebay but they  don’t seem to work. (Why did they make so many if the tools didn’t work?)  In each case the center hole cut by the lead screw would grow until the bit could wobble around in the hole with nothing guiding the cut. The deepest I could cut was about 3/16″ before it became impossible to make further progress. I had to cut out the centers with a coping saw and finish the edges with a drawknife. With a drill press and a circle cutter this job would be easy, in theory, but when I equipped my drill press with this unbalanced cutter the lateral forces caused the chuck to fall off.  The chuck continued to fall off periodically after that, until I learned the trick of freezing the arbor.

I marked the sizes using punches and then inking them with pens.  Curiously some pens, like the Pigma Micron, seem to be ruined by writing on wood.  They never started writing again after I used them for this job.

For years we hung the other measuring cups on a store bought rack, which really didn’t work well. The hooks would fall off, and it wasn’t well organized. So to go with the rack above I made a rack with designated hooks:

cuphooks

For the measuring spoons I made this rack by attaching veneer to a square foot sheet of plywood:
spoonhooks


Pen and Paper on the Fridge

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We need pen and paper available at the fridge. To make a pen holder I started with a small scrap of cherry.  I used the router to cut out a recess in the block of wood and I installed some magnets on the back.  If I was going to make one of these today, I’d probably glue together two layers to avoid using the router.

To hold paper we used a plastic rack for many years, but its weak magnets resulted in frequent trips to the floor, and it eventually cracked beyond repair.  I made a much nicer wooden replacement from quarter sawn cherry I had left over from the file cabinet.

Now we just need to figure out how to keep people from walking off with the pens.


pen.rack

Room for four pens.

pen.holder.rear

Five quarter inch rare earth magnets keep this firmly in place on the refrigerator.


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Look at the fantastic quarter sawn fleck figure.

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This needed to be thicker than the pen holder. I made it from several pieces rather than hollowing it out by router. It is also much newer than the pen holder. Is the lighter color due to fewer years of darkening? Or is it a lighter colored tree?

paper.rack.rear

Next time I think I would use a smaller number of larger magnets. But this holds securely even on the slightly curved surface of our new refrigerator.

Hanging Utensils on the Wall

We bought a rack for hanging utensils on the wall, but then we ran out of room. So I made a pegboard out of oak. I built it using frame and panel construction with oak plywood for the panel. I used a piece of pegboard to guide the drilling of the holes in the oak plywood.

pegboard_front

The Talon pegboard hooks hold utensils well, though I did have to clip off some of them with wire cutters to get a good fit for some items.

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From the front the oak frame blends in with the cabinet. The non-woodworkers don’t notice the change in grain.

 

Cooling Rack

For mounting cooling racks I made magnetic bars by setting 1/8″ thick half-inch rare earth magnets into 1/4″ thick wooden bars. The magnets hold the bar onto the fridge and also hold the steel cooling racks. They worked well—until we switched to a stainless steel rack that was only barely magnetic. Each of the three bars could hold its own steel cooling rack, but all three bars together barely keep the stainless one on the fridge.  A better design would probably make use of hooks instead of magnets to hold the stainless steel racks.

coolingrack1

Three bars with magnets embedded in them.

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Barely holding up a stainless cooling rack.

Draining rack by the sink—fail

We have the dish soap and hand soap by the sink and that area stays constantly wet, leading to mold. I tried building a draining rack to improve this situation. I used the router to cut grooves in a piece of ipe.  (I think I killed the router bit.) Underneath the groves are perpendicular so water drains all the way through.  The first problem was that the wood stayed wet underneath.  I discovered that tiny insects had taken up residence.   To correct this problem I raised the wood up off the counter on rubber feet.  This got rid of the bugs, but I now have brown staining coming from the wood.  It seems that wood is not the right material for this application.

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Draining soap rack made from ipe.

 

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Rack in use.