Archive for June, 2009

Chain cutter

Tuesday, June 16th, 2009

This congenial looking tool is a chain cutter for exhaust pipe.

chain cutter

Basically, you loop it around the exhaust, anchoring the free end on the catch at the top of the handle.  You then tighten the assembly by twisting the grip area, which pulls the end of the chain into the handle.  After it is snug, you then work the handle partway around the exhaust pipe, and tighten again.  You repeat this, rust flakes settling on your forehead (and in your hair, eyes, etc.) until the cut is made and the now loose pipe falls on you.

This is the sort of tool that is purchased about 90 minutes into a project.  You have had time to get the car up on jackstands, find your cardboard “creeper”, get under the car, go back inside to get new batteries for your flashlight, get back under the car, and spend a fruitless 15 minutes trying to wangle a hacksaw blade into the cavity the exhaust pipe runs through.  After tiring of using about 3″ of the hacksaw blade due to lack of room, you get back out from under the car, brush yourself off, work circulation back into your arm, and try to remember why you didn’t get the special tool at the auto store.  Answer: it’s about $40.  This sum, which previously seemed princely for a tool you may use twice in your life (professionals use pneumatic grinders or saws if they can), now seems to be almost beggarly in return for the imagined bliss of an easy job.  You picture yourself diving under the car with your new cutter, spending a few minutes working it back and forth, and emerging with a smile on your face and the length of pipe in hand.

-$40 later, you return to the job and it is easier, even if you don’t work the cutter quite far enough back and forth each time, resulting in an intact strip of metal that was in the gap in the chain next to the handle flange.  Somehow, no matter the project, and no matter how many elegant tools you may have, things invariably come back to either a hammer, a saw, or main force (usually repetitive in nature).  In my case, I fatigued the exhaust pipe off by unbolting the other end, and working the pipe back and forth until the strip of metal gave up.  Rumors that I nearly punctured the underside of my car with a chisel are lies.  I didn’t have one on hand.

The cutter is on my table because I somehow damaged a cutting wheel on it, which will prevent it from working properly in the future, presumably 20 years from now after another unwise automotive “investment”.  With a damaged wheel, the chain will “jump the track” and never cut where you want it to.  Fixing it was a simple exercise with a file, honing down the damaged edges.

gloved hand holding chain cutter

Gloves make many things easier.  Holding a blade under pressure is one of them.

Lacewood veneer

Sunday, June 14th, 2009

My learning project for the past week was brought on by access to a woodshop.  An offhand remark by one of the Toolmonger site administrators about wanting a lacewood veneered desk led, as these things do, to me purchasing an infeasibly large amount of veneer and accompanying jug of contact cement.  I bought an 8′ x 2′ roll from Veneersupplies.com, primarily because I  this was the smallest size piece I could get that could cover a 2′ wide surface without me needing to join multiple pieces of veneer to do so.  Given my inexperience in these matters, I figured that I would try one thing at a time, and artfully joining veneers on a large surface seemed a much for a first outing with sheet veneer.

For those who know little about the subject, veneer is very thin-sliced wood, sold in sheets or rolls of strips.  It is often (but, importantly, not always) cut in a rotary fashion, peeling layers off of a log that has been put on a rotisserie.

Given that the supply of 3′ diameter mahogany, walnut, cherry, and indeed any tree has been sadly depleted by previous generations, we are left with two ways to make an attractive wood tabletop.

The first is to join smaller boards, butting them together along their long sides and gluing them.  (I’ve mentioned this in a previous article).  This gives you a strong surface, but you are limited in the “figure” of the wood; that is, the grain will almost always be parallel across the table, and individual boards can often be distinguished despite efforts to pick grain figure that blends the boards together.

The second way is to make a flat tabletop out of whatever you can (MDF, boards, plywood) and then glue a sheet of veneer over it.  You can also use multiple smaller sheets to make symmetric patterns (diamonds are popular), or, if truly masochistic, can use many many pieces of veneer and do parquetry and marquetry.  There are a few benefits to this technique; you can make more patterns, get the dimensional stability of plywood, and/or have the look of much more expensive wood than you could otherwise afford.

This is not to say that veneer is necessarily cheap.  The showy veneer figures, such as burl, birds-eye, and other “freak-figured” (really!) pieces, can easily cost several hundreds of dollars for large pieces.

I wanted something showy, but not hideously expensive.  Lacewood is an Australian tree (Carwellia Sublimis, for the taxonomists), and, unlike some fancy woods, is not endangered.  It is also, when cut properly, quite showy.

unstained lacewood

You can see how it looks different from, say, pine.  The whitish “rays” stand out quite a bit, even unstained.

Technically, the veneer I got was not a flitch, but several already joined onto a paper backing.  I don’t have a veneer press, and a little research on the Veneersupplies website indicated to me that using contact cement and a paper-backed veneer would work best if veneering by hand, so I got a quart of Titan DX Better Bond glue as well.

I took a piece of good-grade (read: flat) 3/4″ plywood, and cut a 22.5″‘ x 3′ section out of it.  If I want to make a desk out of it, it will be about the right size.  I wiped dust, sawdust, blood, etc. from the plywood, and picked up the glue bottle.  Unfortunately, the manufacturers of Titan DX assume that you know what you are doing, and provide no instructions on the jug.  After a little more research, I brushed it on both the plywood and the back of the veneer, making sure to get complete coverage and to pluck any errant bristles out of the glue.  I then held my breath, picked up the veneer, and brought the two surfaces together as if I were slowly closing a big coffee table book.  The concern at this point is air bubbles, since you will never get them out without cutting the veneer, once the glue is dry.  To drive out any bubbles, and to help the wood set together, I took a rounded off “chunk o’ 2×4” (TM) and worked it across the surface.  They say you are supposed to do this radially out from the center of the veneered surface, but the lacewood has a pronounced grain structure, and it was much smoother if I worked it along the grain.  I did this until I heard no more glue squelching noises.  To finish up, I clamped a similarly sized piece of plywood over the top of the veneer, thus making a poor man’s vertical press, using 8 clamps, my brother’s spare exercise weights, and some waxed paper between the plywood and the veneer, to avoid the embarassment of surplus glue making me a veneer sandwich.

It worked pretty well.  The next day, I took a new razor, flipped the newly veneered plywood over, and cut the spare veneer away from the edges, squaring it up.  Do this against a flat surface to avoid lifting the veneer away from the plywood at the edges.

One of my favorite moments when working on a carpentry project is staining the wood.  It is the point at which mistakes are made manifest, but also the point at which the wood ceases to look like raw materials and begins to look like something you might want to have in your living room.  Once again, I used Zar cherry 116.

stained-25

You can see near the top of the picture how it iridesces as the angle of light changes.  It should look even better after I put a coat of polyurethane on it, making it look a bit “wetter” and sealing up the slight unevenness of the surface of the lacewood.

Now I need to use it for something.

Suggestions?

Mousebot

Thursday, June 4th, 2009

I bought a Solarbotics “mousebot” a few months ago.  It’s kind of cute:

overhead view of mousebot

The mousebot’s official name is Herbie, which seems to have become a “cute” name in the last 40 years or so, possibly having something to do with the eponymous(e) Volkswagen.  Let’s look at another view of it:

close view of mousebot

Less cute.

mousebot kit

The kit’s instruction book is pretty well thought out, being large, well-illustrated, and detailed.  It is evident that the target market is new hobbyists, as there is a goodly amount of explanatory text, cautions where appropriate, and a scattering of jokes appropriate to the younger set.  This is fortunate, since one goal of my assembling the kit was to get comfortable with soldering.   (If this article reads slowly, it is because I am now typing with a bandage on my finger.  Fortunately, I only burned myself once.)

The kit, once assembled, proved to be quite durable, which impression I tested by accidentally stepping on the bot shortly after completing it.  The shell, held together by numerous solder joints, stayed intact, and the only damage was the motors breaking their moorings.  Fortunately, despite other shortcomings, I possess a solder sucker, which made short work of the (now bad) motor wire connections.

Assembly is straightforward, with one major caveat. The problem is that the battery fits quite tightly, so tightly that it is possible to construct the robot in such a way as to result in a too-small battery compartment.  I had to solder the LM386 chip directly to the circuit board, rather than using the socket provided.  This gave me a bit more room, and I would also suggest fitting the motors with the battery installed.  I would not suggest this kit for anyone younger than, say, 12, given the necessity to think around this problem.  Without a solder sucker, a razor blade, and some patience, I would have been out of luck.

underside view of mousebot

Being unable to leave anything stock, I did make one modification.  After the above picture was taken, I bound the front “whiskers” together at the bend just outside of the circuit board.  This made the whisker assembly a bit stiffer.

So, what does the robot do?

It is an example of the “light-seeking” type, sometimes called a “photovore”.  This sort of robot is a popular choice for inexpensive introductory kits, since the infrared sensors (the eyes) are cheap, and the robot can be led around with a flashlight.  Unlike most such kits, which are solar-powered, Herbie instead uses a 9-volt for it’s energy source, making it very fast for such a little kit with no gearing.  It moves at a brisk walking speed, and will likely outrun your kids.  Given that it has no suspension, it is best suited to very flat flooring; it would do well on a table but for a propensity to do a header over the edge after .5 sec running time.

The whiskers and the tail are both impact sensors.  When it flexes far enough, each sensor bumps the conductive ring surrounding its base, engaging a backup circuit that tells the robot to back up for a moment, skewing its direction a bit.

As is usual for me, the assembly of the kit is more fun than playing with the result, but given its purpose as a learning kit, this is perfectly OK.  The kit is a few dollars more expensive than I would prefer ($40 or so), but one is paying for the very good instructions as well as the parts, and so I don’t think the cost unreasonable.

mousetrap and robot

(Lest you worry, I know that cheese is bad for mice, but Herbie can’t be hurt by the past-its-sell-date Rambol in the trap, nor, really, the trap itself.)

What is it?

Thursday, June 4th, 2009

One of my co-workers, knowing my fascination with things mechanical, dropped this on my desk the other day:

it-1-orthog

it-1-rear

It took me a while to figure it out.

As a hint, the label on the end flange reads indicates that it takes 10 amps at 120 or 240 V, and there is one (optional) part missing.