Sunday, July 12, 2015

Remote Set Spat on Shell

On July 10, 2015 we deployed the remote set spat on shell treatments: 6 envelopes on racks, 6 envelopes on the ground and a comparable amount of shell directly on the substrate.  Each envelope consisted of 2.5 Kg of spat on shell (Spissula primarily).  Because of a shortage of remote spat on shell from the hatchery we had to half the amount of shell per treatment.  Also the shell material differed from the non-remote set treatments (Spissula vs Crassostrea shells) so we will have to break the experiment into two independent studies.  At right  the experimental treatments, cultch in envelopes on ground,  directly on the ground and envelopes on the racks.  

Friday, June 26, 2015

Cultch Efficiency: Rationale and setup


We are continuing our studies of how aquaculture techniques can be leveraged to increase the growth and survival of oyster spat on shell cultch for oyster restoration.  


Racks and Bags
Bags on Ground
no Bag no Rack
(on ground)
Remote set cultch
Clean cultch
This year we have chosen the following sets of treatments.   We will try to separate out the role of oyster bags and racks on survival and growth of remote set and wild set spat on shell cultch.  Our control treatment will be cultch on the bottom without any protection.  Cultch material consists of 5 kg lots of dried oyster shell which have been out of the water for over one year.  The shells vary in size but are for the most part whole.  On June 24, 2015 mesh bags of oyster shell were placed in the remote settling tank at the hatchery.  The three clean cultch treatments were prepared for deployment on July 1, 2015.

Tuesday, September 24, 2013

Rage WITH the Machine

We have made several key adjustments to the drive system and the machine is working very well.  First we upgraded to a new Makita 14.4 volt lithium ion battery which pairs better with the opperating voltage of the motor (12-14 Volt) giving us an increased roller speed and the added benefit of a longer working time.  Second we discovered that round belts are driven more efficiently by a v-notched pulley which reduces belt slippage.  As a consequence, we are getting more efficient drive from the setup.  Today we used the sorter to sort clams from an area and stockpile the legal sized product in a special row so we can dig 100% legal sized clams quickly on a harvest day.  Field sorting also allowed us to put the two sublegal grades back in other areas reducing harvest time in the future since like sized clams will be ready at similar times.  The motor and battery mount is removable so that all the electrical components can be easily removed when the machine is cleaned.
Motor and drive pulley,(center), white idler pulley (left) and the Makita battery (right)

Wednesday, July 17, 2013

Field Throw Down!

We took the field sorter out to the flats today for the first time.  While Deniz and Taner bullraked for clams offshore, we set up the machine at the water's edge for sorting.  We took half bushels of rinsed clams and poured them onto the hopper and fired up the machine.  It worked very well sorting into runts, borderline and market-sized clams.  We were able to go through about six bushels of product in under an hour.
Feeding clams onto the rollers
  • Feed from hopper to rollers is easy and fast
  • Sorted product quickly and efficiently
  • No breakage of clams - used extruded mesh bumpers in crates to minimize impact between clams 
  • Battery provided adequate power for an hour of sorting
  • Wiring needs work: need to enclose battery, motor and wiring
  • Motor had enough torque to drive the rollers except when both rollers fully loaded-probably from belt slip (need adjustable tensioner) not lack of torque
Overall, we are very pleased with the first field test.  Tomorrow we'll take it out for a full-on harvest and see how it performs.  In the mean time, we have ordered some connectors for the permanent wiring and will work on the motor mount and belt tensioning mechanism.

Sunday, July 7, 2013


Getting the drive system right for the field sorter has been our focus for the last month.  Originally we felt that we could adapt a portable 18V electric drill to power the sorter but discovered that the high speed, relatively low torque of a drill motor was not well suited for attaching a drive pulley to drive the round belt and rollers. We started looking for an inexpensive DC motor with the specs that we needed.  First we tried a small rotisserie motor ($59.99)  which had adequate torque but turned at 50 RPM, which would have taken a very large pulley to step up the speed of the rollers.  Next we found a little DC motor with high torque that turned at 192 RPM ($14.75).   It was a surplus auto seat motor with a metric worm gear shaft.  We have mounted it on the frame and put a 2" pulley on it to drive the round belt.  In a test using a fully charged Makita 12V drill battery the motor ran the roller sorter for an hour without loading any clams on the rollers.  Next we run the clams.

Wednesday, May 1, 2013

Been Framed!

Wellfleet Steel Works has completed their work on the frame.  They did a fantastic job putting it together.  We have assembled  the rollers with PVC pipe and end caps with blind bore roller bearings.  The next step is to put plastic inserts on the diverters to guide clams toward the rollers once they are swept off the hopper.  The biggest challenge now is figuring out the drive mechanism.  Our original design uses an 18v rechargeable drill motor with a continuous round belt, but we are concerned that it can deliver high torque at low speeds for the duration of an average sorting session in the field.  We have run some tests with a 12V hammer drill but it goes into hammer mode at a relatively low torque and doesn't deliver the power we need.  I think if we had a low speed drill without a clutch or hammer mechanism it might work well.  A plug in electric drill spins the rollers easily.  One alternative that has always appealed to us is a foot treadle.  People power!  Stay tuned...

Wednesday, April 10, 2013

Fabricating the Frame

Matt and Bob at Wellfleet Steel Works work their magic
Modified frame with bump out and simpler roller end support
Plans have been handed off to Matt at Wellfleet Steel Works, where he and his assistant Bob are turning the diagrams into aluminum reality!  I made a number of alterations in the plans based on suggestions from the guys, primarily with the roller frame which made it a lot simpler, sturdier and better.  Instead of having individual posts holding the ends of each roller, we are going to have a single flat piece drilled with slots to accept the stub shafts.  I also realized, in the middle of the night (go figure)  that the continuous round belt went around the frame!  That means that to change the belt you would have to unweld the frame- oops!  We decided to bump the frame out on the side to accept a tension pulley and Matt suggested that we make a bolt on back piece for the roller frame.  That way the belt can be easily changed by undoing the four bolts on the back piece.  Bob is now working on making the hopper and guides.