Wednesday, July 18, 2018

A sonic mystery...

A sonic mystery...  Most mornings at home, I make a cup of tea for myself and a cup of coffee for Debbie.  We both use the same kind of mug: a 16 ounce double-walled stainless steel mug.  A long time ago I noticed something odd: tapping a spoon on the rim of the mug makes a distinctly different sound on the tea mug than it does on the coffee mug.  The tea mug sounds higher pitched and crisper; the coffee mug lower pitched and sort of a thud.

Why would this be so?

I've been trying various experiments over the past couple of weeks to try and narrow down the cause.  First I kept track of the mugs we used, and switched which one was for tea.  That made no discernible difference.  Then I compared the tea and coffee with no additives (cream, sugar, etc.).  This time the two mugs sounded very similar, though the coffee mug was still slightly lower pitched and not quite as crisp.  Then I added sugar to the tea – and the pitch went up (not what I expected at all!).  I added Equal to Debbie's coffee and heard no difference.  I added milk to my tea and the sound pitch went down slightly and got slightly less crisp.  Then I added collagen powder to Debbie's coffee, and the sound changed quite dramatically: lower pitch, much thuddier.  Ah ha!  Then when I added milk to her coffee and the pitch went down a bit more.

So ... collagen powder made the biggest difference.  Why?  What does it do to the liquid that affects the sound of tapping the mug's rim?

I have two theories.  First theory is that the collagen powder increases the viscosity of the liquid, and thereby increases the damping effect it has on the “ringing” caused by the tapping.  Second theory is that the collagen powder, when dissolved, changes the speed of sound in the liquid, which changes the resonating characteristics.

Do any of my readers have any knowledge of this phenomenon?

Monday, July 16, 2018

On precision...

On precision...  Do you know the best way to gauge the alignment between two pieces of wood?  This need comes up frequently in woodworking, and getting alignment wrong means (at best) a lot of sanding and (at worst) discarding a piece of work.  So what's the best way to determine whether two pieces of wood are lined up exactly?

Most woodworkers already know the answer, either from a mentor early in their woodworking efforts, or through hard experience.  I'm in the former camp, myself – my grandfather (father's side) taught me this simple technique.

Most non-woodworkers don't know this technique, and if asked to speculate, will usually come up with answer involving a known straight edge and squinting at how it sits across the joint that is supposed to be lined up.  That technique is difficult and quite error-prone – and isn't all that accurate anyway.  The best way actually involves no tools or instruments of any kind – just your finger!  All you do is run your finger across the joint to feel if there's a difference in height between the two pieces of wood.  Really!

A study five years ago determined that fingertips can detect surface details as small as 13 nanometers ( about 0.0000005 inches).  No instrument within reach of an amateur woodworker or cabinet shop can measure anything that small.

Your fingers are a marvel of texture-detecting design – better than anything mankind has ever been able to make...

Sunday, July 15, 2018

Tesla Model X...

Tesla Model X...  Our Model X is still in the shop, as the techs haven't yet figured out the source of one problem I reported.  That problem: sometimes as I start a trip, the cruise control won't work.  Also the center console isn't showing a picture of the road, with other cars detected.  I infer that the sensor system is therefore not working, as that's the source of the data for both observed issues.  A few miles after starting, both issues just go away, and everything works as usual.

The techs could not replicate this problem, of course (isn't it always like that?).  However, the Model X apparently has quite a bit of logging internally, and they were able to see the evidence of the problem in that log (and, incidentally, convince themselves that I wasn't some kind of nut).  So the techs kicked this up to engineering.  The first group of engineers to examine issue, late last week, couldn't figure out what was going on.  So they kicked it up to “zone”, which, I'm told, is internal Tesla-speak for “the real engineers, the ones who actually know what they’re doing”.  I'm told that escalation to “zone” is quite unusual.  It figures that such weirdness would be visited upon me!  The plan as of Friday was to wait out the day on Monday (tomorrow) to see if “zone” comes back with some kind of answer.  If they do, then they'll fix the problem and I can have my car back.  If they don't, then the techs will finish servicing my car and give it back anyway – and whenever “zone” finally decides to grace us with some feedback we'll decide what to do next.

Which means that we've been stuck with the Audi A6 since Wednesday.  I'm ready to find me a great big power hammer somewhere and squish the damned thing!

Last night...

Last night ... Debbie made Brussels sprouts and blue marlin (fresh from our local supermarket), photo at right is just before they went on the grill.   The marlin was very tasty, but Debbie and I agreed that it's one of those fish dishes that really needs a sauce.  The meat's texture, after cooking, is much like chicken – it's not an oily fish, like (say) salmon.  The Brussels sprouts were delicious, but I suspect not quite done in the middle, and my tummy rebelled.  Debbie's learning how to use our new grill, which is amazingly hot compared with anything we've ever had before.  Today she made chicken and roast corn, the former following some directions specific to our grill (she found them on the web).  The chicken pieces (thighs) were on the grill for just 8 minutes per side and they were completely done.  That grill is fast – but the high heat means that Debbie has to learn grilling techniques that are a bit different than what she's used to.  Tomorrow she tries a ribeye steak...

I started working on the remaining five drawers for the grill cabinet today.  It's almost a week since Jim and Michelle left, and I last worked on them – my time has been consumed with all sorts of other things.  I started two drawers today: the two that go under the wider middle sections.  One of those drawers is the shallowest I've made yet, which means the vertical pieces that tie the horizontal rails together are the shortest I've made yet – under 2" long.  That's so short that I can't have opposing pocket screws that line up with each other, as there simply isn't room for them.  So I resorted to a “trick”: I offset the screws just enough to let them clear each other.  At left below is the piece of wood with the pocket screw holes drilled, and at right is the installed piece.  It worked great!

Midway through this construction process, I heard an ominous rattle from my trusty Makita drill.  With a little investigation I figured out that it was the thrust bearing – quite an important piece of any electric drill (even when in screwdriver mode).  It still worked, but it seemed clear that it wouldn't survive for long.  So I decided to make a run to our local Home Depot (one of the few places open on Sunday here) and pick up a replacement.  I am delighted with that drill, which I purchased about seven years ago, so my intent was to purchase exactly the same drill.  This was not to be, as Makita has stopped making them.  There's a newer version, however, with all the same functions (drill, screwdriver with torque limiting, and impact drill), but with more torque, a brushless motor, electronic speed control, and smaller.  In the photos below, the all-black drill is the new one, the blue-and-black the old one.  I've long been impressed with Makita's battery-powered tools, but I didn't think they had much room for improvement on their drill.  I was wrong.  The new one is a bit lighter, substantially smaller, and the added torque is impressive.  The brushless motor with electronic speed control is really nice – the drill ramps up the torque as required to maintain the speed you've selected.  The old drill's trigger didn't select the speed, but rather the power – and often that meant the drill would run much faster than you intended when the load was light.  Not this one.  Another nice touch: manually tightening the chuck is much more comfortable with the new, larger, rubber chuck grip.  Nice one, Makita!

Saturday, July 14, 2018

An old friend of mine...

An old friend of mine ... Mike B., from North Carolina, mentioned to me that he had two GPS systems for his big rig truck that were broken.  He depends on these to do his job, and the loss of the more capable GPS was really making his life difficult.  In both cases the necessary repair involved soldering tiny little parts.  The more capable GPS had a surface-mounted mini-USB connector that needed replacing; the other a resistive touch screen that needed to be soldered (flexible PC to flexible PC).

I have the right tools to do the job, and perhaps hands that are a bit steadier.  So I had him ship the two GPSs to me.  Working yesterday and this morning, I was able to repair them both.  Some specialized tools really helped a lot.  I have a head-mounted pair of 3.5x binoculars (designed for surgeons and dentists, much like the ones at right); these gave me a nice, clear view of the work.  I'll bet I looked pretty weird while wearing these!  My Hakko desoldering iron (with built-in vacuum) nicely desoldered the old parts.  Finally, my Hakko soldering iron with a 0.03" diameter tip let me solder the new parts on.  I don't mean to say that it was all easy because of the tools, though – there might have been a bit of non-Mormon approved language as I struggled to get all the pieces in place and hold them there while soldering.  Removing the old mini-USB connector was a challenge mechanically.  My finest solder was twice the diameter of the work piece, making it a real challenge to get solder only where it belonged.  And both circuit boards had taken some hits, with traces lifted during both the current and previous repairs.  Those had to be repaired with wire jumpers. 

But in the end, I managed to get both of them working.  Mike was very happy to see this (I sent him proof-of-life photos of the GPS screen).  It felt good to be able to help a friend, and it also felt go to have proof that I can still repair delicate electronics.  Both GPSs are now at the post office, and he should get them next Tuesday or Wednesday...

Friday, July 13, 2018

We are laughing at ourselves for this!

We are laughing at ourselves for this!  Our Tesla Model X was due for service, and on Wednesday morning we made the 90 minute drive down to Salt Lake City to drop it off.  We made an appointment early in the morning (8 am) to maximize our chances of getting a Model S as a loaner (we knew they'd be keeping our car for a day or two).  We didn't get the Model S – they'd all been taken already.  So we got a rental: an Audi A6.

At any point in our lives prior to buying the Model X, we'd have been astounded at getting an A6 as a loaner.  By any conventional measure, it's a very nice car.  Plenty of power, handles very nicely, lots of modern conveniences, etc., etc.

But we are Model X owners.  We've driving 36,000 miles in our Model X.  We're spoiled rotten by the experience.  Now the A6 looks like a miserable POS to us.  We hate it...