help again, .. - leaks & exhaust flow

[cboggs]

OK gang, .. having some more problems, .. and need help.

First, .. I've got a leak somewhere, .. flowed a head yesterday and
gained 10 cfm on a head I've been working with for over 5 years, .. NOT !

Put my test plate on and the bench is reading 10 cfm high all the sudden.
So, .. where do I look for leaks??? The orifice plate and the dividing
wall it is mounted on??? or could it be some place else and cause it
to read high too???

Second problem is a bigger one, ..

when trying to calibrate the exhaust it blew the back off, .. and I think is
causing my high cfm problem in that it "separated" most of the inside
construction of the bench. I haven't run exhaust tests as I think the bench
won't handle it.

I'm not a wood worker, .. and to be honest with the work load I have
don't have time to build another cabinet. The guy who built this for
me just didn't build it strong enough for 36" test pressures, .. used
press board for most of the inside parts, etc.

I'd REALLY like to find a VERY good cabinet maker to build this thing
right, .. but, .. haven't found one around the Northern virginia / dc area that
didn't want $5K to build it. Shame too cause I really like the way it works.

Any ideas??

I've even thought of ( gasp, .. ) getting a used SF-600 and maybe adding
a few motors. The problem with that is it's limited to measuring 600 cfm.

Ideas, .. ????? I've got a CnC machine showing up in a few weeks,
gotta learn that, get heads digitized and programed, .. .. a TON
of work to get out, .. development jobs people are waiting on, .. just no time
to deal with this too. ( arrgggg )

Curtis

[bruce]

If it wasn't such a long commute to DC from PA I'd come work for you, can't afford the cost of living down there either so moving is out

I know that didn't answer your problems though . . .

[Scott]

Let your guy have another go at it, show him the kinds of pressure we're dealing with, I'm sure he's capable of fixing it.

Scott

[cboggs]

[bruce]

695 and 495 suck! I was driving that a few years ago down to Walter Reed AMC when I was undergoing testing and I HATED it! Lucky for me they kept me for 2-3 weeks at a time, I could never do it daily. Trip takes about 2.5 hrs on a good day with light traffic.

Never gave the nylon strap a thought? Sounds like a plan to me. Course I am also anal rentenative or so I am told all the time at work. I also get told "its not going to the Moon" so just fix it . . .

Humm is that something all flowbench guys have in common?

Bracing should be a good fix

[larrycavan]

[Thomas Vaught]

Most every bench I have seen has had a "blow-out" due to not compensating for the forces that the bench can create. Glad you like the stopper deal Curtis. I have been using them for years once I saw the weaknesses in the msd orifice design. Even Harold Betties likes the stopper bench over the rotating deal.

Tom V.

[Nick]

Mummm stoppers good, rotating disk bad. I'll build you a new bench for $4000. I guess this is why them blue benches cost so much, because your income depends on it working day in and day out. Sorry dude. I still would not buy a superflow, that to me would mean defeat, and I am not willing to do that.

My bench tried to self destruct to. I did not sit down to calculate the forces involved. I figured I wanted to to stay together with as much as all the motors could pull. So I hooked up a makeshift water gauge sealed it up and turned on the motors. It was fine at 28" but as it got to about 60" the sides moved in about 3/16". I stopped right there and reinforced every wall, before I tried an exhaust test. I'm sure the thing would have came apart if I did not go back and redo the bracing.

I like liquid nails. It is very strong, and fairly cheap in the big tubes at Home Depot.

Put 2x2s in every corner and every 8" in the field, fully glued and a few screws to hold it until it drys, and it will be bullet proof.



Nick

[cboggs]

[Tony]

I have never had a bench rupture on me, but it is scary to see those panels bulge the way they do.

My latest effort has a completely welded steel angle frame, and panels bolted and glued onto the outside. Wood screws leave a lot to be desired, especially if they have to be removed and replaced repeatedly to gain internal access. A nut and a bolt is far more secure.

[larrycavan]

[larrycavan]

[Thomas Vaught]

Quote:

"I wonder if the SF bench will handle the extra pressure?"

If you read the MSD article closely you will see that the guy put 16 motors into the basic envelope. He also had to add reinforcements.

I have heard of several people who have installed 12 motors in a MSD type design. Wrench's Garage shows a bench with three rows of motors (4 motors in a row). The package is pretty easy.

The SF bench is made out of Birch plywood (7 laminates, I believe).

Most Benches using MFD will be very strong up to the point that they blow apart. Plywood is more forgiving.

I presently am thinking about reinforcing my bench design with the previously mentioned "T" nuts. I was thinking that maybe if I used
a wall of 1/2" MFD then a 1/8" sheet of aluminum, and then another 1/2" wall of MFD glued together with construction adhesive that the walls would be less likely to blow apart, would weigh slightly more and would allow normal glue up techniques.

What do you think?

Only other way I see is the dedicated frame deal with panels attached.

Tom V.

[larrycavan]

Birch plywood ought to be pretty strong and like you said, more forgiving. Not much in terms of flex with particle laminates. They just take what they can and then BOOM!...

If a guy took the back off the bench and installed 2" square supports along the corner seams with good glue and a few wood screws, the cabinet strength would be raised a fair bit. Tom Clark [original MSD bench builder] installed metal cross braces like Tom points out. His bench was [as I recall] only 1/2" plywood to begin with and they ended up with something like 12 motors in it. I'll wager a phone call to MSD would get you hooked up with Tom if he's still there. I spoke to him shortly after the article was printed and he was very helpful.


JMO

Larry C

[Tony]

Tom, why not use one inch MDF ?

Two half inch sheets will weaken the structure because the sheets can move independently. Think of how a leaf spring works. Or a wire rope as compared to a solid steel bar. To be stiff it needs to be one solid sheet.