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Public Lab Research note


This is an attempt to replicate an activity.

First Time Build: The Bucket Air Quality Monitor

by a1ahna | March 29, 2021 18:01 29 Mar 18:01 | #26056 | #26056

This research note contains my personal experience building The Bucket Air Quality Monitoring kit. I built the variant from the store that includes the clear bucket and pump. This is documentation of my personal experience, so to be clear - I didn't follow the steps exactly in order of the manual, and I only took photographs of the more confusing steps.

The first step in the Bucket Build is to set up your sample bag by tightening a ferrule onto the bulkhead, or plastic tube extending from the 5L Tedlar sample bag. Having never worked with ferrules before, I was confused on how to tighten the ferrule and initially thought I needed to use the wrench on the ferrule directly. I was wrong!

  • Figure 2. The bulkhead disassembled. The front ferrule and back ferrule are both contained within the end nut when they arrive from the manufacturer. In this photo, the two parts of the ferrule have been removed and put on display. Figure 5 demonstrates the arrangement of the front and back ferrule within the end nut. The intake port will have a plug on the exterior, exposed side of the bulkhead, while the interior portion of the bulkhead (inside the bucket) will have the end nut attached to the sample bag screwed onto it.

The image above shows the bulkhead disassembled, with two end nuts and one plug. The front and back ferrule are contained within the end nut. The image above shows the ferrules removed from the end nut, so your part may look different the first time you disassemble it. To "crush" a ferrule, you simply tighten the end nut onto the bulk head with the front and back ferrule still contained inside the end nut. Therefore to tighten the ferrule onto the sample bag, you simply slide the end nut (with ferrules inside) onto the tube extending from the sample bag, use two wrenches to tighten the two pieces together, and then untighten the bulkhead to remove it.

While awaiting counsel from the master of bucket building, @kagradow1, I jumped on down to step 4 - drill holes in the lid of the bucket. Despite my limited hardware knowledge, I knew I could handle this task.

  • Figure 3. Drilling the ⅜" hole in the bucket lid for the intake port

  • Figure 4: drilling the 9/16" hole in the bucket lid for the outtake port, tube, and pump.

Once I had Katie's reassurance that I was attaching the bulkhead correctly, I went forward with tightening the ferrule. This step was the most difficult for me because I have never worked with hardware that had ferrules to tighten, therefore I didn't understand what I was supposed to do. With Katie's direction, I realized that this step was incredibly simple once I understood conceptually what I was trying to accomplish. In summary, a ferrule is like a grip inside of an end nut that prevents the end nut from moving or sliding. A detailed workflow for steps one and two can be found in the captions for Figures 5, 6, and 7.

  • Figure 5. The back ferrule and front ferrule sit inside of the end nut as demonstrated above. In order to tighten the ferrule, make sure the ferrule inside of the end nut rests near the end of the tube as seen in the image above. If any mistakes are made, you can clip the end of the tube off and try again, therefore you should place the ferrule as near to the end of the tube as possible. _

  • Figure 6. Next, the end nut was slid towards the end of the tube so that the ferrule is contained within the end nut, then the bulkhead was loaded into the end nut. Tightening these two parts together by hand will not exert enough force to properly crush the ferrule, therefore you need two wrenches, as demonstrated in Figure 7. _

  • Figure 7. Using one wrench, hold the fixed nut of the bulkhead. Using the other wrench, grip the end nut with the ferrule inside. Tighten the two parts together. Loosen the two parts, and the end nut should be securely affixed to the end of the tube extending from the sample bag. The end nut and ferrule are not reusable and will stay affixed on the sample bag.

Steps 5 through 8 detail attaching the intake port to the lid by sanding the area around the drilled holes. Note that the fixed nut of the bulkhead should be inside of the bucket, meaning you should insert the bulkhead from the bottom of the bucket to the top. I placed a sticker on the lid of my bucket so that I could better distinguish which side was which.

Steps 9 and 10 detail the process of affixing the tubing to the brass coupling. Similar to the first two steps, a "sleeve" contained within the end nut of the brass coupling needs to be crushed onto the tube so that the end nut will stay in place and not slide along the tube. In order to affix the sleeve, slide the tube through the end nut with the sleeve inside it, then tighten the end nut onto the brass coupling, as depicted in step 10 of the build guide.

Step 11: Beware that the fixed nut of the brass coupling should be on the inside of the bucket, just like with the bulkhead of the intake port. This means if you were to put the lid onto the bucket, all that should be exposed outside of the bucket are the threaded portions of the bulkhead / brass coupling and the washer used to steady them. Next you will screw a plug onto the exposed threads of the bulkhead, and you will screw the end nut and tube to the exposed threads of the brass coupling, as seen in the images below.

Once everything screwed into place, your bucket is almost complete! If you purchased a pump from Public Lab, you should use the smallest nozzle to fit into the tube. You may have to put a little cut into the tube so that the nozzle of the pump fits.

I hope this breakdown helps you along the way to building your own bucket!

  • Figure 8. The inside of the bucket lid. The fixed nuts of the bulkhead and the brass coupling should be visible on this side of the lid.

  • Figure 9. The exterior facing, or top side of the bucket lid. The tube has been screwed into the brass coupling. The plug has not been screwed into the bulkhead.

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