I made the conversion because I was tiered of paying for the rather expensive disposable bags for my vacuum cleaner.
A Fine quality vacuum cleaner (look for space were the bag is used to be)
I suggest an old Nilfisk G80 G70 or older.
Tree old cans or other cylindrical chambers that fits around each other and of cause fits inside the vacuum cleaner
a roll of Window Insulation Strip.
pop rivets .
5. thin fabric (put it to your mouth you should be able to breath through it, if it is to dense you wont get any suction) you should have enough to wrap it around the smallest of the tree containers/canes.
Some locks, cramps and what ever you can find to keep your contraption tight when the vacuum cleaner is operating.
Blind rivet tool,
screwdrivers and spanners
Get a good old, not be too small, vacuum cleaner.
Nilfisk is an old Danish brand so if you live in Denmark or some where near Denmark, it is not unusual to spot fine working old Nilfisk vacuum cleaners in the recycling stations and on the local garbage collection. For some reasons a lot of Danes seems to be ignorant towards the quality of these old machines. However this can be an advantage as you should be able to pick up functioning Nilfisk vacuum cleaners for free.
Nilfisk is just the model I choose to use, you should be able to find other models in your neighbourhood suitable. I don't recommend using any particular brand but keep in mind that there should be some space where the bag use to be.
Update: I am going to make a new pre motor filter some day. there is of cause a reason for that being there, it takes the last specks of dust which escapes the bag/filtering system. I recommend that you do the same.
What we want to build now is a box with tree chambers. the outer chamber is going to have a hole in the wall that fits the intake of the vacuum cleaner were the bag would be. the next chamber is going to have small holes drilled in the side so it functions as a filter for larger objects so that it allows only sand an dust to go through. the last chamber is going to have larger holes but these are covered by some fabric which is wrapped around its sides. this should collect the remaining fine dust and sand. on the top of this inner container a big hole will be drilled (between 1 1/2 and 2 inches) this hole shall pierce all the layers yet only leaving airs from the inner chamber to be sucked out. I added an extra layer of fabric on the top of the hole to minimise the risk of any dust escaping the system.
You can use Cookie Tin Boxes to create the tree chambers depending on the shape of the vacum cleaner you may find other containers more suitable. the containers should also be able to fit inside eachother with a close fit on the top and button but leaving some space at the sides for dust collecting.
I was lucky to find two tin boxes which fitted eachother in height. I had to trim of a little of the height on the last tin.
Update: Actually it is better just to leave out the middle box, after using it for some weeks I found out that it clocked up too soon so I tried removing the middle box, I found out that I actually did not need it.
Drill a large hole about two or 1 1/2 inches that penetrates the lids of all the boxes.
I recommend that you cover this hole with an extra layer of fabric to prevent any dust that might have escaped the inner filter from getting blown back into your house.
When you have sorted out the leakages your bagless vacuumcleaner is finished and ready for service. congratulations.
If you have to little suction power you should try drilling more holes in the two inner boxes.