## Saturday, May 27, 2017

### Paradise ponders: exploding saws, hydraulic ignorance, and wooden trigonometry edition...

Paradise ponders: exploding saws, hydraulic ignorance, and wooden trigonometry edition...  Yesterday morning I started on the project of building the cedar shed kit that arrived the day before.  The shed is going onto an existing concrete slab, but there's a small challenge there: the slab is sloped (3.5" in 10'), and I'd kind of like my shed to stand up straight.  The kit includes a plywood floor built on cedar 2x4 “joists”.  After examining that floor's design, I figured out that I could support the floor on four pieces of pressure-treated lumber, nominally 4" thick.  The height of each piece would be different, varying from 2" to 5.5", to correct the slab's slope – I actually got to use some trigonometry to figure that out.  I'd also cut each piece of wood using a small angle (1.6°) so that the tops of the pieces would all be in one plane and level.  Sounds easy!  So off I went to Home Depot to buy my four pieces of lumber.

So why did the saw's safety system trigger?  My finger never touched the blade.  However, the pressure-treated lumber I was trying to saw was quite wet, as evidenced by its weight.  Lumber that's sufficiently wet will conduct electricity, and the saw detects human contact with the blade electrically.  Because the lumber was conductive, it fooled the saw into thinking that it was in contact with me, and it triggered.  The saw has a “bypass” mode that will let me run it without the safety mechanism.  That's what I'll have to do to saw this lumber – after I replace the brake cartridge and install my new saw blade.  I could let the lumber dry out, but then I wouldn't be able to build my shed until about August!

When I ran up to Logan yesterday to pick up a new saw blade, I stopped by an irrigation company referred by my sprinkler contractor, to talk with them about constant pressure pumps.  I'm not going to name the company, as I haven't actually done any business with them.  They had me talk with their pump expert.  It was kind of appalling, really.  I am far from a pump expert, but I do know a little bit about them.  I understand, for instance, the relationship between pressure and flow rate; I know what friction loss and head height is.  I know how to read a pump curve.  That dangerously small amount of knowledge made me a certifiable rocket scientist by comparison with their “pump expert”.  He was also very fast with the (outrageously) expensive solutions.  For instance, he proposed two \$1,400 motor-operated valves when I told him I wanted an automatic bypass for the pump.  When I showed him how to accomplish the same thing with a \$50 check valve, he had trouble comprehending how it would work and was clearly put off by my interference with his \$2,800 sale.  I don't think I'll be buying my booster pump from those folks! :)