Plastic Super Dust Deputy

[Troy Turner]

Contacted the nice folks over at Oneida last week about the metal version of their SDD. She told me that if I could hold out, they have a new molded one coming online. Got this email last night. Looks pretty interesting.

I'm going to put it in front of my Jet 1 1/2hp (with Wynn filter).

Any thoughts?

253737

[paul cottingham]

Wow, I am seriously considering one myself, and now this comes along. I wonder what motivated them to go this route. I also wonder if it is as efficient as the metal one.....

[Cyrus Brewster 7]

Any word on price?

[Mark Welte]

Had to be manufacturing costs and lead time. When I ordered my metal one they were 6 weeks behind schedule on getting them built and shipped. Also because of the issues with working with metal I bet there are some trade offs made between being able to manufacturing and efficiency of the cyclone. It would be interesting to see if there are any notable performance differences between the plastic and metal Super Dust Deputies.

[Troy Turner]

Any word on price?

That's what's got me. When I talked to them, they said it would be cheaper than the metal for the sheer fact that it's plastic. But it's an intro price of $169 with $199 crossed out. That was the price of the metal one. I'll give them another call and see what they say.

[Troy Turner]

Ok, so I called and asked them about the price. He wasn't too sure, but did say the metal may actually go up in price, but he doesn't think the plastic one would go to the $199 mark.

What I took from the conversation was "order it now because this is the cheapest it will ever be".

[Ben Hatcher]

Very interesting. I have the 2009 version of their metal SDD and I'm not sure if it has an inlet ramp like this one has. I wonder how to two compare in terms of separation.

[Wade Lippman]

I looked at their website. They show it attached to the DC with flexible hose with two tight 180 degree bends. Wouldn't that radically reduce the air flow?

[paul cottingham]

Yes. I would never hook it up like that, all of the pipe in my shop is solid PVC, all running into my 1.5 HP steel city unit. works pretty well, and rolling the unit around won't work in my shop.
Smooth pipe works way better than flex. Big surprise, eh?
i recognize that my setup is way less than ideal, but these are the compromises we make sometimes.

[Alan Schaffter]

Manufacturing with plastic is soooo much cheaper- materials maybe a wash but labor costs nothing compared to metal fabrication and manufacturing speed- lightning compared to metal fabrication. Frankly I am totally surprised the DC manufacturers haven't made plastic cylones for years. I can see some sort of OSHA restriction on plastic commercial units, but not on consumer grade units.

And did you notice it appears to have a spiral inlet ramp like the ClearVue? Hmmm, what does that say about other Oneida designs that don't have it? Wouldn't they benefit from the same "innovation"? How does the saying go- imitation is the sincerest form of flattery?

[Wade Lippman]

And did you notice it appears to have a spiral inlet ramp like the ClearVue? Hmmm, what does that say about other Oneida designs that don't have it? Wouldn't they benefit from the same "innovation"? How does the saying go- imitation is the sincerest form of flattery?

The Griz I just got has a spiral inlet and they have been making it for like 6 years now. Maybe they all do and you just don't see it in metal?

[Peter Aeschliman]

I have a 3hp Grizzly four-bag unit, modified with integrated Thien Baffles and Wynn environmental filters. I was looking at adding this to my setup and going away from the Thien Baffles. But the thing that keeps me from pulling the trigger is the 5" inlet. It seems really odd that it has a 5" inlet and a 6" outlet. Why not do 6" for both?

I've run 6" ducting in my shop and it sure would be a shame to choke it down to 5" like that. So I think I'm going to pass.

[Alan Schaffter]

The Griz I just got has a spiral inlet and they have been making it for like 6 years now. Maybe they all do and you just don't see it in metal?

I have not looked inside a Grizz, but are you sure it has the "spiral inlet ramp", not just a sloped inlet which they call a "ramped inlet" in their catalog? The spiral inlet ramp is a "warped"* helix that wraps completely around the central tube. It ensures when air has completed one rotation around the central tube it cannot impact the side of the (slanted) inlet nor strike the incoming air from the side where it can generate turbulence. (I believe you can clearly see it in pics and videos on the ClearVue site.)

A spiral inlet ramp looks something like the one in the pic below taken before installation. It wraps around the central tube and is usually attached to the tube and the cylinder wall once installed. Again, I haven't looked inside a Griz, but I can't see any indications in their website and catalog photos that one was spot welded to the main cylinder and there is no mention of "spiral" in the product description, just "ramped inlet." To me that means it has a slanted inlet that likely just extends to the central tube and not something that wraps the central tube (if so, it would be classified as a neutral vane, a misnomer). The reason I say this is that it can be costly and difficult to manufacture and install, because a helix must not only be cut correctly it must be warped- * a true helix cannot be made from a flat sheet without warping it- trust me this is a geometric FACT! In fact, the dimensions provided on Bill Pentz's site (which he got from a Cornell math prof) are for a helix approximation only.

I could be wrong, wouldn't be the first time.

http://www.ncwoodworker.net/pp/data/1329/medium/inlet_ramp.JPG

Here is a spiral inlet ramp partially installed in the main cylinder- the pic was taken looking from the bottom of the main cylinder before the cone was installed. Note, because of the spiral ramp you (and the spiraling air) can only see the end of the rectangular inlet, not its sides or bottom. After the incoming air makes a full rotation the direction of air flow will be parallel to air just entering the cyclone.

http://www.ncwoodworker.net/pp/data/1329/medium/P10101092.JPG

[Phil Thien]

I have not looked inside a Grizz, but are you sure it has the "spiral inlet ramp", not just a sloped inlet which they call a "ramped inlet" in their catalog?

The Donaldson Torit cyclone I saw the other day had what they call a helical baffle that looks just like your helix above.

That Torit looked pretty old, but nobody knew how old it was.

Anyone know how long DT has had helical baffles?

[Wade Lippman]

I have not looked inside a Grizz, but are you sure it has the "spiral inlet ramp", not just a sloped inlet which they call a "ramped inlet" in their catalog?

I pulled the hose off and had a look. Just a ramped inlet. I guess I was impressed by that, because my old JDS didn't even have that. The Griz tube is much shorter (at least relative to diameter) than yours.

[Michael W. Clark]

The benefit I see to the spiral is that it reduces short-circuiting from the inlet to the outlet pipe. It is really a band-aid to improve the efficiency of what would be a low efficiency cyclone due to the tangential inlet being so close to the outlet pipe and the short outlet pipe. It is a concession that is made to try to keep the cyclones small to fit in a given space and therefore reducing price.

In industrial applications, erosion (abrasion) is a major factor with wood dust applications (and especially other more abrasive applications). A tangential inlet is much cheaper to build than an involute that wraps around the outside of the body. The tangential inlet on a standard effciency cyclone like the DT will have material impacting the outlet pipe. Unless you direct that material away from the outlet pipe, you will wear a hole in it and the efficiency goes out the window.

Mike

[David Kumm]

My old Torit has a rectangular inlet that narrows to about 5" as it gets to the cylinder which is about the distance between the helical baffle and the outer wall. I would guess the cyclone is over 20 years old. It has the full mounting ring welded to the cone and those haven't been made for a long time. I also have an Air Sentry cyclone that has the helical baffle inside as well and it is old. It is a compromise. There are a few cyclones with the involute inlet but they are usually custom made and more expensive. Dave

[Alan Schaffter]

Few really understand the purpose of the spiral ramp and its predecessor, the so called "neutral vane" (I haven't been able to determine the source of that name). But, for those who get lost in words, below are a few diagrams that should help illustrate what Michael and I have said. In the first case incoming air can strike the central exhaust tube as well as the spiraling air. The neutral vane prevents this, but adds its own resistance as spiralling air can strike the side of it. The spiral ramp takes the neutral vane concept one step farther. It forces the spiraling air lower and prevents it from hitting the side of the neutral vane or the incoming air. It may also reduce the effects of the velocity difference between the incoming air and the spiraling air.

Basic cyclone (Wood mag DIY, early Oneida, Grizz, etc., all(?) older consumer grade cyclones and some retail units still being sold to WWers today)- no neutral vane, no spiral ramp:

http://www.ncwoodworker.net/pp/data/1329/medium/Cyclone.jpg

Cyclone with neutral vane- essentially the inlet has been extended until it reaches the central exhaust tube.:

http://www.ncwoodworker.net/pp/data/1329/medium/Cyclone-NV.jpg

Cyclone with spiral ramp (hard to really show what is happening using 2D only):

http://www.ncwoodworker.net/pp/data/1329/medium/Cyclone-SR.jpg

[Michael W. Clark]

I have a 3hp Grizzly four-bag unit, modified with integrated Thien Baffles and Wynn environmental filters. I was looking at adding this to my setup and going away from the Thien Baffles. But the thing that keeps me from pulling the trigger is the 5" inlet. It seems really odd that it has a 5" inlet and a 6" outlet. Why not do 6" for both?

I've run 6" ducting in my shop and it sure would be a shame to choke it down to 5" like that. So I think I'm going to pass.

It is common for cyclone inlet/outlet connections to be different sizes. In this case, the 5" inlet is more of a pain requiring a transition. The goal of this small cyclone is to get the big stuff and reduce loading on the filters downstream, so a 6" inlet would have been more accommodating. However, if you pull the same air volume through a cyclone with a 5" inlet vs. a 6" inlet, the one with the 5" inlet should be more efficient, assuming all other things are equal.

Mike

[Michael W. Clark]

There are a few cyclones with the involute inlet but they are usually custom made and more expensive. Dave

One way they get around it on some commercial cyclones is to make the cyclone fatter and use the tangential inlets. This creates more space between the inlet and outlet pipe and still using the less expensive fabrication process. The downside is the efficiency is that of a cyclone with smaller diameter, but you have to pay for the materials to make the larger diameter.

[Noel Poore]

Alan

The fourth picture on the g0440 page at Grizzly seems to show that it has at least a partial "spiral inlet ramp"? You can't tell from that picture whether or not the ramp goes all the way round, but there's no particular reason to assume that it does not.

Noel


I have not looked inside a Grizz, but are you sure it has the "spiral inlet ramp", not just a sloped inlet which they call a "ramped inlet" in their catalog? The spiral inlet ramp is a "warped"* helix that wraps completely around the central tube. It ensures when air has completed one rotation around the central tube it cannot impact the side of the (slanted) inlet nor strike the incoming air from the side where it can generate turbulence. (I believe you can clearly see it in pics and videos on the ClearVue site.)

[Jim Neeley]

It seems really odd that it has a 5" inlet and a 6" outlet. Why not do 6" for both?



Peter,

The smaller the inlet the higher the pressure drop but the higher the velocity of the air / wood blend.

While greatly simplified, separation is a function of the velocity at the inlet, as the higher velocity tends to draw the wood towards the outer wall of the cyclone as the air goes around the cyclone. From the outer wall it falls to the bottom and doesn't get drawn up the inside center to the filters.

The larger diameter on the outlet has the air moving slower, so less likely to carry wood from the cyclone.

Jim