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Harbor Freight Rikon Impeller Upgrade – Is It Worth It? #5: De-Constructing the HFDC

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Blog entry by clagwell posted 12-11-2019 07:43 PM 539 reads 0 times favorited 7 comments Add to Favorites Watch
« Part 4: Performance Curve Comparisons Part 5 of Harbor Freight Rikon Impeller Upgrade – Is It Worth It? series no next part

This is the fun part where I remove parts of the dust collector and see how much the flow increases.

Baseline

The baseline configuration here is the stock DC modified with the Rikon impeller and a 6” inlet:

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The performance curve was shown in the previous post but here it is again. Note that the CFM axis has been extended to 1200CFM. We’ll need that later.

Remove the Filter Bag

Of course the first thing to do is remove the filter bag.

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Internet wisdom says that the bag doesn’t have enough area to get good flow and that’s probably true for a well used one. This bag has only been used for testing, never with dusty air. It’s porous enough that’s there’s almost no resistance to flow. The dashed Blue line is the performance curve without the bag. There’s a difference but it’s too small to show up on the graph.

Remove the Centrifugal Separator (aka “Bag Holder”)

The next thing to go is the centrifugal separator (or “collector ring” or “bag holder”). I tried to keep the bend in the hose unchanged to isolate it’s effect.

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This makes a big difference. The graph shows 2.5” loss at 600CFM caused by the separator. It’s definitely something that has to go if a pre-separater like a Thein baffle or cyclone is used. Using it to simply hold a filter is a waste of precious static pressure.

That 2.5” at 600CFM is probably enough to make up for the loss caused by a cyclone.

How Bad is the Hose?

Let’s take it off and find out!

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That’s another 1” of loss at 600CFM.

Fan Outlet to 5” Round Transition

The last thing to remove is the plastic transition from the rectangular fan outlet to the 5” hose.

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This of course is the performance of the fan by itself. Operating it this way with no restrictions will quickly smoke the motor. I had to be careful testing at these flow levels. I scrambled the order of the orifices and allowed for plenty of cooling time.

The curve extrapolates to a free delivery rating of 1400CFM if that matters to you.

Flow rates above about 600CFM will cause reduced motor life. Above 800CFM can cause air quality issues (smoke).

-- Dave, Tippecanoe County, IN



7 comments so far

View EarlS's profile

EarlS

3425 posts in 2953 days


#1 posted 12-11-2019 08:23 PM

No surprises from what I see. Just goes to show what the impact of the various parts of the system have on the pressure/flow.

I’m surprised you didn’t over amp the motor and trip the breaker.

-- Earl "I'm a pessamist - generally that increases the chance that things will turn out better than expected"

View MacNut11's profile

MacNut11

33 posts in 2642 days


#2 posted 12-11-2019 08:36 PM

I just scrolled through all 5 parts of this topic and I don’t see a photo of the actual impellers. Did or could you take photos of them?

View Brawler's profile

Brawler

101 posts in 436 days


#3 posted 12-11-2019 09:15 PM

Why would not having the hose on the output “reduce motor life”? I read somewhere (honestly I think it was on LJ) that the lack of back pressure is easier on the motor because the impeller is spinning in vacuum and doesn’t have to push against that backpressure. I’m no expert, just got conflicting info. I work with a whole building full of engineers I think I need to ivestigate this. However thanks for the graphs, interesting measurements.

-- Daniel

View clagwell's profile

clagwell

70 posts in 398 days


#4 posted 12-11-2019 09:18 PM



No surprises from what I see. Just goes to show what the impact of the various parts of the system have on the pressure/flow.

I m surprised you didn t over amp the motor and trip the breaker.

- EarlS

The highest current I measured was 20.51A. I made the traverse in about 5 minutes. That’s not enough I-squared-t to trip a 20A breaker.

I measured the thermal time constant of the motor at about 15 minutes. My temperature rise extrapolation (see Part 3 of this blog) for 20A is 140C. 5 minutes is about one third of a time constant so I would expect a rise of somewhat less than 50C in that time. So, definitely over amped but not yet smoke.


I just scrolled through all 5 parts of this topic and I don t see a photo of the actual impellers. Did or could you take photos of them?

- MacNut11

The original fan is 10” diameter with 3” high blades forward curved at roughly 15 degrees.

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The Rikon replacement is 12” or so in diameter also with 3” high blades. They are backward curved. I can’t get to them right now to check the angle but I don’t remember it being much different from the HF (opposite direction of course.)

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-- Dave, Tippecanoe County, IN

View clagwell's profile

clagwell

70 posts in 398 days


#5 posted 12-11-2019 09:47 PM



Why would not having the hose on the output “reduce motor life”? I read somewhere (honestly I think it was on LJ) that the lack of back pressure is easier on the motor because the impeller is spinning in vacuum and doesn t have to push against that backpressure. I m no expert, just got conflicting info. I work with a whole building full of engineers I think I need to ivestigate this. However thanks for the graphs, interesting measurements.

- Brawler

Ok, first of all, there’s nothing remotely close to a vacuum in a dust collector. A vacuum is about 400” of water. The most negative pressure here is 10”. Nowhere close to a vacuum.

The horsepower requirements of a fan increase with increasing flow rates. Minimum power at zero flow and maximum power at maximum flow.

There’s a chart in Part 1 showing motor current as a function of flow rate. Higher current means a hotter motor (see Part 3). The higher the motor temperature the shorter it’s life.

-- Dave, Tippecanoe County, IN

View Redoak49's profile

Redoak49

4351 posts in 2594 days


#6 posted 12-11-2019 11:11 PM

The logical question is what is the max cfm that you can run without damaging the motor.

AND the big question is given the max cfm that you can run is the upgrade worthwhile?

A great job with this and should answer many question about the true cfm of the HF dust collector.

View clagwell's profile

clagwell

70 posts in 398 days


#7 posted 12-12-2019 12:20 AM


The logical question is what is the max cfm that you can run without damaging the motor.

AND the big question is given the max cfm that you can run is the upgrade worthwhile?

A great job with this and should answer many question about the true cfm of the HF dust collector.

- Redoak49

Thanks Redoak49. I hadn’t been able to find performance data on the “Rikon Upgrade” so I thought I’d share what I’ve learned.

I’ll have a lot more to say about the motor and the value of the upgrade in a future post.

-- Dave, Tippecanoe County, IN

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