Some CFM stats for CT-midi and comparisons to shopvac, dust deputy, etc

[amt]

I got my new toy, oops, I mean tool in today.  It is a Pyle Thermo-anemometer.  It has a fan-like sensor in a 2.75" cage which can measure air velocity up to 5900 ft/sec.  I thought I would run some tests on the ct-midi and a old shop vac I have.  To run the tests I connected a 25 foot 2" ID hose to the vacuums.  This hose is the Genesis DPZ static conductive hose, available at Amazon and Wynn Environmental (it is a excellent quality hose).  I tested various configurations:

shop vac with dust deputy, no bag, with filter (somewhat dirty but not clogged): 98 CFM
shop vac without dust deputy, no bag with filter (somewhat dirty but not clogged): 139 CFM
ct-midi with bag 1/3 full and fairly new & clean filter: 104 CFM
ct-midi with bag emptied and fairly new & clean filter: 140 CFM
ct-midi with no bag and fiarly new & clean filter: 163 CFM
ct-midi with no bag or filter: 172 CFM

I am not 100% convinced the CFM numbers are spot on.  I measured velocity (ft/min) directly and calculated CFM based on the cross sectional area of the anemometer.  I do think, however, that their relative differences are probably valid.

What stood out for me was (a) the difference with/without the dust deputy and (b) the difference between a 1/3 full and an emptied ct-midi bag.

Seeing the CFM drop by ~40% by adding the dust deputy was disappointing.  Some of this is probably due to the drag it adds, but I suspect, for these measurements with  2" hose end-to-end, the dust deputy may not be ideal.  The DD specs that the hose connections are 2", but that is the OD, where as the hoses used have a 2" ID.  The actual ID of the DD might be more like 1.75", which could significantly reduce CFM.  I think I'll know more about this when I test with a 36mm and 27mm hoses (should see that the drop in CFM when adding the DD is much less).  

Although the ct-midi may have similar CFM ratings as the other festool vacuums, you may want to consider what the CFM might be with a bag 1/2 full, if that is the average configuration.  I would not be surprised if a ct-36 has a lot more CFM with a bag 1/2 full compared to a ct-midi 1/2 full, as the bag area is much larger and can probably flow more.

As for the ct-midi with no bag or filter, well darn, that is moving.  Probably not a good idea to run it like this (I only do it for the test).

 

[RKA]

Very interesting indeed!  I wish I had considered that before ordering my mini.  I was under the impression from all the glowing feedback here that these DE's would maintain more of their flow as the bags filled up compared to other vacs. 

Oh, I think you flip flopped the numbers for the shop vac.  With DD should be the lower number.

 

[Saskataper]

That's awesome. I have a toy like that as well and have thought of doing similar tests but never got around to it. If I remember to I'll compare my older midi to my 36ac.

 

[jacko9]

Interesting, since the CT-Mini at 1/3 fill drops a similar amount as the Dust Deputy inline what is the overall effect of having the Dust Deputy inline to keep the bag from filling?  I have filled my UDD box but my CT22 bag was still empty and the flow seems to be constant?

I would be interested in more data with different configurations.

Thanks for the information,

Jack

 

[amt]

Thanks for catching the error, RKA.  I have updated the data in the first post. 

I would have also hoped the CFM would not drop so much with the bag 1/3 full, but it kind of makes sense given the small bag size.  I would stress that this is a test with a 2" hose, so the drop off might not be as bad with a 36mm or 27mm hose, as they will certainly have mush less CFM even in the most ideal conditions.

Jack, I am curious about the DD with clean bag on the ct midi as well, and hope to test that soon.

 

[amt]

Some results for 36mm hose.  This is with the shopvac, no bag, somewhat dirty but not clogged filter

without dust deputy: 105 CFM
with dust deputy: 80 CFM

So, the drop in CFM was ~24%, compared to a ~29% drop for the 2" hose.

There's one more thing I want to change out, and that is the hose between the dust deputy and the vacuum.  This is a very short, but old shopvac hose which is probably not as smooth as a Festool or Genesis hose.  I just need to order a couple hose ends to make a new hose out of the Genesis DPZ 2" hose.

 

[jacko9]

Some results for 36mm hose.  This is with the shopvac, no bag, somewhat dirty but not clogged filter

without dust deputy: 105 CFM
with dust deputy: 80 CFM

So, the drop in CFM was ~24%, compared to a ~29% drop for the 2" hose.

There's one more thing I want to change out, and that is the hose between the dust deputy and the vacuum.  This is a very short, but old shopvac hose which is probably not as smooth as a Festool or Genesis hose.  I just need to order a couple hose ends to make a new hose out of the Genesis DPZ 2" hose.

I thought that the whole point of the Dust Deputy was to keep the filter unclogged so the experiment that might make sense is running the shopvac x number of hours and watch the pressure drop as it gets clogged and then run the system with the Dust Deputy inline and see what the pressure is after the same number of hours.

The point of the system is to get the best results over time without having to keep cleaning your filter or changing bags not the initial pressure drop or am I missing something here?

Jack

 

[iamnothim]

This is great info.  Thanks !
I own a CT-Midi.  Had I known this, I would have purchased a CT-36 or CT-26 .  They have the same CFM but double the bag size (8.9 / 6.3 gal vs 3.3gal).  Assuming your measurements are correct,  the increased volume of the 26/36 bags translate to a stronger, longer CFM with only a $2 cost per bag increase.  The only reason I see to own a Midi is size and weight.

 

[amt]

Some results for 36mm hose.  This is with the shopvac, no bag, somewhat dirty but not clogged filter

without dust deputy: 105 CFM
with dust deputy: 80 CFM

So, the drop in CFM was ~24%, compared to a ~29% drop for the 2" hose.

There's one more thing I want to change out, and that is the hose between the dust deputy and the vacuum.  This is a very short, but old shopvac hose which is probably not as smooth as a Festool or Genesis hose.  I just need to order a couple hose ends to make a new hose out of the Genesis DPZ 2" hose.

I thought that the whole point of the Dust Deputy was to keep the filter unclogged so the experiment that might make sense is running the shopvac x number of hours and watch the pressure drop as it gets clogged and then run the system with the Dust Deputy inline and see what the pressure is after the same number of hours.

The point of the system is to get the best results over time without having to keep cleaning your filter or changing bags not the initial pressure drop or am I missing something here?

Jack

Your thoughts are on track.  I just wanted to get some baseline results first and characterize specific parts.  Your point about using the DD to keep the filter clean & bag empty is a good one, and it's probably the next test to do.  Since I already have a result for a 1/3 full bag on the ct-midi, I can now test the ct-midi with a empty bag and a the dust deputy.  I suspect we we'll see is that the performance is about the same, but there is no need to change out bags when using the dust deputy.

 

[jacko9]

Some results for 36mm hose.  This is with the shopvac, no bag, somewhat dirty but not clogged filter

without dust deputy: 105 CFM
with dust deputy: 80 CFM

So, the drop in CFM was ~24%, compared to a ~29% drop for the 2" hose.

There's one more thing I want to change out, and that is the hose between the dust deputy and the vacuum.  This is a very short, but old shopvac hose which is probably not as smooth as a Festool or Genesis hose.  I just need to order a couple hose ends to make a new hose out of the Genesis DPZ 2" hose.

I thought that the whole point of the Dust Deputy was to keep the filter unclogged so the experiment that might make sense is running the shopvac x number of hours and watch the pressure drop as it gets clogged and then run the system with the Dust Deputy inline and see what the pressure is after the same number of hours.

The point of the system is to get the best results over time without having to keep cleaning your filter or changing bags not the initial pressure drop or am I missing something here?

Jack

Your thoughts are on track.  I just wanted to get some baseline results first and characterize specific parts.  Your point about using the DD to keep the filter clean & bag empty is a good one, and it's probably the next test to do.  Since I already have a result for a 1/3 full bag on the ct-midi, I can now test the ct-midi with a empty bag and a the dust deputy.  I suspect we we'll see is that the performance is about the same, but there is no need to change out bags when using the dust deputy.

I really appreciate your taking the time to gather this data which I think should be interesting to a lot of members on here.

Jack

 

[grbmds]

The real question is which works best in practice. I have a CT48 which is superior to anything else I've ever owned for pick-up and noise level. I have a Fein which is great also and, with a HEPA filter, probably does about the same job. For me, actual performance in use is the test regardless of what you found in CFM measurements. After all, isn't that why we bought them? Mine works great and I will never second guess my decision.

 

[rst]

All things being equal, the collector with the largest filter capacity will always have the best draw.  I have two of Oneida's steel dust deputys and have no dust in my Fein vacs despite cutting wood, acrylics and aluminum.  I have a 20 gallon heavy steel drum (similar to drums grease comes in) and I can hear the lid pop tight when I turn on the vac . 

 

[amt]

some more results:

27mm hose:
ct-midi with DD: 65 CFM
ct-midi without DD 70 CFM
shopvac with DD: 51 CFM
shopvac without DD: 57 CFM

36m hose:
ct-midi with DD: 87 CFM
ct-midi without DD: 108 CFM
shopvac with DD: 80 CFM
shopvac without DD: 104 CFM

 

[grbmds]

I'm confused. Are your vacs not working properly? I was just  curious what promote the measurements? My Festool vac sucks up more of my sawdust than any other vac I have owned. To me, that's what's important.

 

[amt]

grbmds, I am providing this information who are interested in knowing it.  Knowing that the vacuum might work better/worse in certain configurations (different hose sizes, bag empty/full, with or without cyclone) is useful to some people here..  Clearly, you are not one of those people, so please move along...

 

[grbmds]

grbmds, I am providing this information who are interested in knowing it.  Knowing that the vacuum might work better/worse in certain configurations (different hose sizes, bag empty/full, with or without cyclone) is useful to some people here..  Clearly, you are not one of those people, so please move along...

Just that, for me, my CT 48 works all the time no matter what configuration. That's why I'm confused by the information. Don't they all work the same. I've never had a vac that did as great a job with lest dust/sawdust escaping; 27 mm or 36 mm hose, various adapters, aside. I've never tried without the filter or bag. No need. It works great as is. I thought about the Dust Deputy and even bought one for my Fein. It works OK but it's a pain and really seems to defeat the purpose of having a HEPA filter and disposable bag that can just be removed when full without a lot of dust escaping. I'm not a fan of all Festools, but the dust extractors, as they are, work the best. I will move on as you suggest.

 

[jonathan-m]

I also got myself an Ultimate Dust Deputy (UDD) with the new black anti-static cyclone for my VCP260 with boom arm.
Reasons I got one are:
1) When the bag gets around 50% full, the suction noticibly starts to drops off.
2) Since I have a boom arm attached, I had a really, really hard time to take off the motor and changing the bags.

I already had a hose run up the boom arm which made the vac bulky and adding an UDD definitely doesn't improve the situation.
Overall though, I'm happier now than I was before as my capacity has gone up, my suction doesn't drop off anymore and changing bags is a lot easier now that I don't have to wrestle the boom arm anymore.

So yeah, there are tradeoff's in appearance and footprint & mobility, but the UDD is a worthwile investment in my opinion.
I do wish I had an airflow meter to measure the differences in suction.

Here's a few pictures to show side by side the difference in size.
[attachimg=1]
[attachimg=2]
[attachimg=3]

 

[neeleman]

Hello Jonathan,

Nice setup, nice to see the Protool Vac's.
I also acquired a VCP 260 when they sold them at a discount when changing to the green versions.
Did you get your Oneida Dust Depoty in Europe?
Can you tell me where. I already found a German webshop: Sorotec.
But there don't sell a black version.

 

[jonathan-m]

Thanks neeleman. Hehe same story here. They went for a great price during the clearance compared to the Festool brother!
Then a few weeks later I managed to snag up a used one in good condition from The Netherlands as well. Couldn't let it pass me by

So now I have 2. Im beginning to think vacs are like clamps. You can never have enough of them  [embarassed]

Ive sent you a private message regarding the UDD.

PS: almost forgot. To get the UDD to clip on top of the vac youll need to saw out the tab spacing a little deeper. Otherwise the clips cant fully engage the tabs on the collection box. No big deal though.

 

[objectgroup]

Any chance you can measure the lowest setting on the midi? Trying to figure out the minimum cfm (for an HVLP setup).

shop vac with dust deputy, no bag, with filter (somewhat dirty but not clogged): 98 CFM
shop vac without dust deputy, no bag with filter (somewhat dirty but not clogged): 139 CFM
ct-midi with bag 1/3 full and fairly new & clean filter: 104 CFM
ct-midi with bag emptied and fairly new & clean filter: 140 CFM
ct-midi with no bag and fiarly new & clean filter: 163 CFM
ct-midi with no bag or filter: 172 CFM