As usual, click any photo to bring up a larger version.  

Improving The Bucket Cyclone


I was between projects, which is usually a good time to clean the shop. During projects, the shop becomes more disorganized as tools end up moved around. More importantly, the dust spreads everywhere and a good sweeping and vacuuming are called for.

But cleaning is not so much fun, so instead I thought it would be a good time to take a follow-up look at the DIY Bucket Cyclone that I made a year ago. This was a practically free Thien-baffle type of cyclone, made from a couple of trash-picked buckets, some scrap plywood, and a trash-picked shopvac.

The cyclone worked amazing. In the year that I have been using it, I have NEVER had to empty the shopvac. There is maybe a tablespoon or two of accumulated stuff inside the shopvac canister. To be fair, I am a hobbyist, so I am not using this eight hours a day, but it does get used most weekends and on some evenings.

On the downside, the suction was significantly worse than it was straight from the shopvac. Many people told me that using the crevice tool as the means of "injecting" the airstream into the cyclone was a mistake. More on that later.

In the course of the past year I had made just a few minor upgrades.

First of all, I mounted the whole assembly on a piece of scrap plywood with castors, so it was mobile as a unit. I drilled four holes partway through the plywood as a place for the wheels of the shopvac to be held in place. I also used some paracord to tie the vacuum to the platform. Some bungie cord would have worked better, but this was what I had on hand. (I'm still trying to do this without spending money!)

The cyclone bucket would also slip around so I added three L-brackets on the platform. They are not bolted to the bucket; they are just placed snug so that the bucket stays in place with friction.

Now let's run the numbers.

If I measure the inlet of the cyclone (crevice tool) it is 2-1/4" in diameter. The formula for the area of a circle is πr2, and in this case that means π multiplied by 1-1/8" squared, which comes out to just about four square inches of area.

In contrast, if I measure the other end of the inlet (the skinny part of the crevice tool, inset in the phot), the dimensions are two inches tall, by 3/4" wide, which works out to one-and-one-half square inches in area. Compared to four inches of inlet and that is a HUGE restriction on the airflow.

Fixing that is the most important thing to try.

I used hot glue when building the cyclone, which is fairly easy to cut through and break free. So I removed the crevice tool from the top of the cyclone.

Adapting a round pipe to a curved bucket seems way too complicated, so I'm just building an adaptor out of wood. I'm sort of copying Matthias Wandel's small cyclone build for this.

First I traced the curve of the bucket on a thin pine board, which I then cut out on the bandsaw.

These were glued to some thin pieces of plywood to make an inlet that would match the curve of the bucket.

The inlet side of the crevice tool was traced onto a piece of wood and the curves were cut out on the bandsaw and fine-tuned on the Oscillating spindle sander. In the background of the photo you can see how the crevice tool was also cut short, leaving just the wide section.

I attached the new inlet to the bucket with a whole lot of hot glue.

I also replaced the outlet with a short section of 2" PVC (leftover from when I made an air rocket launch system) which I also hot-glued into place.


Here is a look inside the top of the newly improved bucket cyclone.

I'm quite sure that fixing the inlet will solve the issue of low suction. However, for $5 I bought a small roll of foam weatherstripping and applied it to the top and bottom of the baffle. This should help seal the connection between the baffle and the two buckets.

All that is left to do is to put it all back together.

Unfortunately, I had to re-use the beat up old vacuum filter. I checked the local Home Depot, the local Lowes, Amazon, and I even checked a few stores in Michigan when I was travelling there last weekend. Unfortunately this is a discontinued model and I have not been able to find a match. The best I could find was some for about US$30-$40 that I would still have to modify somehow to maybe fit.

Bear in mind that this is a trash-picked shopvac and I've already had to take the motor apart to lubricate the bearings once. I'm reluctant to put that kind of money into this, when if I wait I can probably find a brand new vacuum on sale for less than double that if I'm patient.

And here is the finished and rebuilt bucket cyclone unit.

Unfortunately I do not have a way to test suction, so I do not have any hard numbers on performance. All I can tell you is that subjectively the suction does feel a lot stronger. I'm quite happy with the improvement, I think it will be useful in my shop, and it still fits in the "almost free" category, which is the best kind of shop project!

Some of the Tools/Supplies Used In This Project: (Affiliate Links)


Thanks for reading!

See Also:

Air Rocket System

Dust Collector Expansion

Worst job in my shop

Simple Shop Vac Fix

DIY bucket cyclone separator