Saturday, May 19, 2012

Sanding at last

When I first had the new boat assembled last fall, I knew my warm days were numbered, so rather than miss another week doing the sanding and varnishing, I decided I would wait and do that in the spring.  Well, warm weather is here at last.  I have put the garage back into workshop mode, and I have even taken the catamaran out for a cruise since the new boat was disassembled again.

I have been able to use my fancy new sander.  I also decided to try and hook up our indoor vacuum cleaner as a dust collector, since the shop vac has an oversized hose.  It worked remarkably well, and I'm sure as long as I change the bag when I'm done, it won't be any worse off.

The finish quality should be another incremental improvement over previous boats.  At least I would say the sanding results are an improvement.  I will be varnishing when I return from a trip next week.  Someday I will hopefully get professional quality results, it is a good challenge.  Maybe someday I will even get a spray gun.  Until then my brushing and rolling will only get me so far.

I have also spent some additional time on the drivetrain.  My previous posts showed a few images of a new all bevel gear design.  I would still expect this to be an improvement, but I have moved towards yet another iteration.  This one is a hybrid chain and bevel gear system, but it is still housed in a similar sized box.  The crank arms attach to a first shaft with large ANSI 35 sprocket.  An intermediate shaft has both a small sprocket and a large bevel gear.  This has the advantage of a higher gear ratio, I should hit 1:6.5 with this design.  It also uses a 1:2 bevel gear set which is significantly cheaper than a 1:4 set (enough that the cost of the sprockets is still cheaper overall).  Lastly, this means that the torque on the bevel gears will already be reduced by the chain gear ratio, so this will improve gear life.  With the lower torque, I will likely test a slightly smaller diameter shaft tube (5/8"), and I am eager to test a prop with carbon fiber blades made by Rick Willoughby that has been sized for this approximate gear ratio.

My budget will hopefully be stretched further by doing a greater amount of machining myself.  I have found a local "makers" organization with a shared workshop and inexpensive dues.  This should allow me to do most of the milling myself.  I have found a space with power for my welder, so if I brush up with a little practice, I can do this as well.

1 comment:

  1. May I suggest a bevel gear set from a big angle grinder for a future :) gearbox?

    I designed as a concept and 3D modelled a somewhat similar idea, using laser cut straight gears as first stage, and the above mentioned bevel gears for second.
    To give you a rough idea of the torque capability, the output pinion fits an 8mm shaft with a 3mm keyway. I think that would be enough to drive the propeller.