Q&D plenum question

[Michael Moore]

Hello,

I've just received a Flow Quik. I'm going to be using it to do mostly some small (100-250cc) motorcycle heads so I got the 2" version. These are for my own projects, not a commercial deal, so I'm not terribly concerned about whether my numbers match those of someone else's bench. I plan on using a shop vac for the vacuum/blowing.

I've been trying to find information that addresses whether there is any advantage to a cylindrical plenum vs a rectangular one, but I haven't seen anything yet. I did search through the fora here.

A sturdy plastic pail (or the body of an old shop vac) would seem to be a good candidate for a plenum and the cylinder should be better able to resist the suction than a flat-sided box. I don't know if the cylindrical plenum would be prone to more cyclonic flow patterns inside, or if some sort of air-straightening lattice would be worth putting in.

I suspect that it probably doesn't matter much as long as I'm just doing relative tests on the same bench with the same problems (if any).

A six gallon pail would give a 48X plenum capacity on a 500 single and near 100X on the small bikes. 9-16 gallon shop vacs seem common and finding a dead one might not be too hard to do. Or I could turn my 20 year old 7 amp/12 gallon vac into the plenum and buy a new one for air supply/vac chores, and maybe add the old vac motor onto the new one for extra flow capacity if needed.

FWIW I was looking at some specs on Rigid shop vacs and something seems not quite right in vacuum advertising land:

289 cubic feet/min, 10A, 12 gal, claimed 5 hp. But 5 hp should be 3.7kW and 10A x 120v seems to me like 1.2kW

187 cu/ft , 12A, 16g, claimed 6.5hp but 1.4kw is 1.9hp

203 cu/ft, 12a, 16g, claimed 6.5hp

cheers,
Michael

[49-1183904562]

[Scott H]

[Michael Moore]

Hi Scott,

Yes, Euro Spares is my website. I'm glad you've found it worthwhile.

Rick, I have read a lot of the posts and did search, but I didn't see anything that seemed to address my question. It seemed like a fairly obvious one and I am not surprised that it had already been asked, but I couldn't find that discussion.

I don't enjoy carpentry (when I cut too much wood off every attempt to weld it back on has failed) and rectangular boxes don't seem like the best way to enclose a low pressure area according to the posts I've seen about having to brace them so they don't flex/collapse. A shop vac cannister is obviously up to the job and seems like it should make for a relatively easy build. Using a plastic or stainless steel vac body avoids painting/sealing wood or trying to keep regular steel from rusting.

cheers,
Michael

[slracer]

Hello Michael, I can echo the comments about Eurospares and had a pic of my first bike posted there! I also had dinner with you at a place just south of LAX about 10 years ago! It's truly a small world! Welcome aboard! -- Doug

[49-1183904562]

[bruce]

I'm a pitot convert (I've seen the light err I mean airflow) . . . I'd ask Audie what they recommend to use with their flow element.

We could speculate all we want but it's their flow element they would know what works with it.

[jfholm]

Michael,
I had a Flowquick at one time. The shape of the settling chamber I feel does not matter, it is the size.

For our orifice benches it is more convenient to build box type. But you could build a cylinder type if the area was large enough, in my opinion.

edit ps: I started typing this before the others added their comments. The Flowquick has a flow strightening mesh in each end of the flow element. I actually used my Flowquick without a settling chamber. I just added another 24" of tube length to the flow element and had a cylinder adaptor made out of PVC. I used a 4" pvc tube that adapted down to the 2" tube for a head adaptor. I had a flat piece of pvc glued to the top of the 4" to adapt the head to the Flowquik element that I added 24" to. It seemed to work fine.

John