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Unread 01/02/2018, 04:39 PM   #10
OzIA
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Join Date: Sep 2016
Posts: 214
I finally moved back to the drive system for the Bio-Reactor’s agitation arm. I guess I’ve been avoiding spending the time on it because of the tedium but it is a very critical component and I need to see if it will work as designed. It’s also very cold, which means I have less desire to spend time in the garage.

I am using ribbed Kevlar belts from the food processing industry. One longer belt (the wet belt) will be used to drive the main pulley, attached to the arm. This belt will be mostly under water all the time. I am using a second “dry” belt to separate the moisture from the motor and also to extend the motor above the sump. This will help prevent the motor from getting salt water in it, regardless of how high the water level gets. Hopefully, the use of two belts will also prevent moisture from getting on the drive shaft, which is metal. I constructed the box for the motor, which is a 12 v 6 rpm geared setup. The shaft is the only thing that is exposed and most of it is in the first pully. Again, I got it off eBay. They claimed it was a “high torque” 80KG / cm motor. It seems to live up to that billing. It uses about ½ an amp, no load but jumps up to 2 amps with me trying to stop it. It seems like it will do the job.

The main drive pulley is cut from two 3/8 plexi disks welded together. The wet belt is just over 5/8 inches wide. I cut two 3/8 inch disks with a 4” hole saw and welded them together. I then cut groves or slots about 1/8 inch deep into the welded disk with a table saw. These groves will line up with the ribs on the belts. This is very tedious: Turn the saw on, make a pass over the blade, turn the disk slightly and repeat. I then added 1/16” poly-carbonate disks on the outside as guides. This process was repeated for all three pulleys. I cut 16 circles out to make all of them and that was just counting the final product. I also had several mistakes and remakes. It took a long time.

The final reduction was only 3 to 1 instead of 6 to 1 so my arms turn at 2 RPM and not the 1 RPM I had planned for. I just didn’t feel comfortable cutting the small pulleys any smaller and I didn’t have enough belt to make the big ones larger and keep the motor out of the water. It’s still pretty slow and the motor seems to have plenty of torque. I’m going to fill the reactor with dry bio-balls and test it out next. I am also thinking I need a tensioner on the larger wet belt.


Attached Images
File Type: jpg motor&box.jpg (48.6 KB, 70 views)
File Type: jpg Belt& Pulley.jpg (67.6 KB, 86 views)
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