CHJ
Established Member
You have made yourself a Camvac :lol:
New vac, it's a question of suckage. . . . . . . . . .
- Thread starter fluffflinger
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fluffflinger
Established Member
Thanks Chas.
I new we could do it.
So I presume that means next time Aldi have shop vac's on offer you'll be buying a second one and building your own twin motored Chasvac :lol: :lol: :lol:
I new we could do it.
So I presume that means next time Aldi have shop vac's on offer you'll be buying a second one and building your own twin motored Chasvac :lol: :lol: :lol:
CHJ
Established Member
Don't think I'll bother, the suckers I've got work fine for me.
siggy_7
Full time tool collector, part time woodworker
Digit":1te7ozo7 said:
That's not quite right I think. The flow velocity will remain the same through a hose regardless of the hose diameter, if you neglect all other effects. Theroetically therefore, doubling the diameter of the hose would quadruple the air moved. The restrictions through the motor ducting and no-load blower speed/power/efficiency however mean that in practice once you make the hose beyond a certain size so that there are small flow losses through the hose, you hit the maxmim mass flow rate through the suction system and therefore flow speed through the hose tails off as you increase the size.
Mod Edit: Quote reference corrected
Only if the the existing hose is restricting the power unit's performence. If the hose is already passing the max that the unit is capable of increasing the hose dia will not effect the outcome.
Best option under any conditions is to keep the hose as short as possible.
Roy.
All other thing constant, increasing hose diameter will allow the motor to move more air.From a label on one of my vacs:
hose dia. min airflow.
21mm 25cbm/h
27mm 40cbm/h
32mm 55cbm/h
36mm 70cbm/h
50mm 140cbm/h
It has one motor so larger hoses wouldn't be used.(20 m/s minimum airspeed wouldn't be met)
From these numbers it's tempting to use the biggest hose possible, but this can effect filtration. If your vac was designed for 32mm hose and you increase to 50mm then the volume of air pulled through the same filter media is more than doubled - the Filter Surface Load Rate has increased - this can mean vacuum motors pulling fine dust through filters. Professional machines typically have massive filter area, an airflow monitor to warn you when it's blocked and a method of cleaning the filter without exposing you to dust. On hobby machines it's likely that the hose is used as a 'choke' to restrict the airflow so that the filters stand a better chance of catching finer dust
It's a complex subject and a bit dull
Matt
hose dia. min airflow.
21mm 25cbm/h
27mm 40cbm/h
32mm 55cbm/h
36mm 70cbm/h
50mm 140cbm/h
It has one motor so larger hoses wouldn't be used.(20 m/s minimum airspeed wouldn't be met)
From these numbers it's tempting to use the biggest hose possible, but this can effect filtration. If your vac was designed for 32mm hose and you increase to 50mm then the volume of air pulled through the same filter media is more than doubled - the Filter Surface Load Rate has increased - this can mean vacuum motors pulling fine dust through filters. Professional machines typically have massive filter area, an airflow monitor to warn you when it's blocked and a method of cleaning the filter without exposing you to dust. On hobby machines it's likely that the hose is used as a 'choke' to restrict the airflow so that the filters stand a better chance of catching finer dust
It's a complex subject and a bit dull
Matt
fluffflinger
Established Member
Matt
I agree with regard to filtration and I am addressing this issue with a cyclone to remove as much material as possible before it enters the vac.
Looking it at it from afar I see it is common in the US for shop vac's to be running on 2.5" (63mm) hose, albeit they have bigger motors but are still relying on the same type of cartridge filter as in the machine I have. That is a HEPA filter designed to stop 99% of particles 0.3 micron and larger. Hopefully with a reasonably efficient cyclone I will not see too much reaching the vac and the filter being able to cope without clogging or letting too much through.
Some fine dust (and I am aware that it is the worst kind) will escape but I will be doing a better job of collection at source which is what good dust extraction is all about and one would hope that overall I will be doing a better job?
I always wear a mask anyway but hopefully the shop will remain a lot cleaner.
I agree it's not the most exciting topic but those who use power tools all suffer the same issues and have to address the problem the best we can.
I agree with regard to filtration and I am addressing this issue with a cyclone to remove as much material as possible before it enters the vac.
Looking it at it from afar I see it is common in the US for shop vac's to be running on 2.5" (63mm) hose, albeit they have bigger motors but are still relying on the same type of cartridge filter as in the machine I have. That is a HEPA filter designed to stop 99% of particles 0.3 micron and larger. Hopefully with a reasonably efficient cyclone I will not see too much reaching the vac and the filter being able to cope without clogging or letting too much through.
Some fine dust (and I am aware that it is the worst kind) will escape but I will be doing a better job of collection at source which is what good dust extraction is all about and one would hope that overall I will be doing a better job?
I always wear a mask anyway but hopefully the shop will remain a lot cleaner.
I agree it's not the most exciting topic but those who use power tools all suffer the same issues and have to address the problem the best we can.
Matt, you are talking volume and I have been concerned with velocity.
Removing dust particles from the air, for example, can be achieved with a low velocity air movement, moving chips, for example cannot.
I'll try and explain, take a regular sided cube weighing one ounce, we'll call the weight X and the air velocity V
Now at a given velocity X will move, all other things being equal the volume of air is irrelvant.
Now if we increase V by a factor of 2 then the weight that will now move is 16W!
Duck, run, tin hat, door!
Roy.
Removing dust particles from the air, for example, can be achieved with a low velocity air movement, moving chips, for example cannot.
I'll try and explain, take a regular sided cube weighing one ounce, we'll call the weight X and the air velocity V
Now at a given velocity X will move, all other things being equal the volume of air is irrelvant.
Now if we increase V by a factor of 2 then the weight that will now move is 16W!
Duck, run, tin hat, door!
Roy.
mack22
Established Member
While folk discuss air flow ,velocity and vortex, etc... spare a thought for the machine that sends all these messages down the wire to this page, The Computer, probably more neglected than some workshop equipment, (or dare I say, even a few wives!) therefore please don't forget that some of the debris that is causing concern about getting into ones lungs will also be getting into the computer, make Saturday 'Check your heat sink day!'
After I had finished my apprenticeship I started working in Radio/TV etc, this was the early 60s and you could always tell the home with a vacuum cleaner, there was little dust in the back of the TVs
Roy.
Roy.
