some air flow question

[zorn]

I have a question which I think will be a simple one for you guys.
I bought these mini confetti blowers. Mine came with a hose setup to suck the confetti:

Someone unlike me who actually understands why that is happening, can you explain why clog happens and how would you suggest me to modify my box shape to fix this?

[planters]

You might want to see how the manufacturers who have set this up do this. See if any of their manuals give a hint. From just a first guess the problem will probably continue as long as the confetti flow is concentrated at the entry point of the tube. The fact that you get a few seconds of flow means that you could probably extend this or prevent subsequent clogs if you disrupt the build up process.

A slowly tapering tube might be more resistant. Your baffles are along this line, but still way to abrupt at the entry point.
And/or, could you bleed 10-20% of the pressurized air from the blower and spray this into the box right at the point of the clog, from under the clog, pushing the clog away from the entrance point of the tube.
More complex would be a pulsed blast of HP CO2 rather than your hand to break up the clog. A solenoid switched by the same switch that turns on the blower motor would automate this.

[norty303]

You want some sort of agitator in the box.
Paintball guns suffer from blockages in the hopper feed so they developed agitators to ensure the balls feed consistently

[planters]

I would go with a funnel, especially if that meant you could increase the diameter of the tube entrance. The connecting tube becomes the funnel, The baffles in the box still suffer from the relatively abrupt transition to the tube.
Fans might work, but I would go with very high velocity fans like the screaming, Sunon tube-axials and blow away from the entrance port to the blower. The disruptive force needs to exceed the clogging force.

[haymaker]

Could it be the angle of the hopper. In the video the hopper is parallel but your diagram shows a downward slope to the feed tube.

[planters]

The static electricity probably hurts and may cause a few of the pieces to adhere and enhance the clogging, but, I don't think that is the major problem. The abrupt transition causes the pieces to decelerate and re-accelerate. There will also be regions at this point where the flow stagnates, like in the center of a vortex. The confetti would accumulate there.

What about stepping back a bit. Did this unit ever clog when the tube was placed in what ever the manufacturer recommended for the confetti storage? What about that beveled inlet on the stock tube? Maybe that is there because the manufacturer found a straight termination clogged?

[dsli_jon]

Sir Zorn -

...What about that beveled inlet on the stock tube?

..I think Sir Planters is onto something, there.. the 'raked-nozzle' on that hose prevents a 'vacuum' from forming in the first place, and would be more 'anti-clog'.. Plus, if you were 'feeding the fetti, manually' via that hose, the 'agitation' Norty was speaking of (great suggestion.. ) would be accomplished from you 'waggling your hose'.. ..I do-question tho (looking at the 'other models', there you-ref'd..) the Inlet-tube *size*, vs yours.. Theirs looks like a much bigger 'throat'..

..Anyhoo, home sick +_+ prepping for shows next week, and was finishing artwork-up for that, and a couple quick ideas came to my mouse..

a) Like Eric is suggesting, perhaps integrate a 'raked nozzle'...

..I would be wary, tho, of the 'red points', there, areas that the 'fetti would be prone to 'snag' / collect, etc.. Ideally, in addition to your (good idea..) to 'port the flow' the inside, ie: http://i.imgur.com/URKF4TO.png ..I'd see it ideal to try and eliminate that little 'step' below the tube (ie: make the tube Mouth near-flush with the 'floor' of the box.. Reduce another 'snag-point', etc..) Just a thought..

b) ..Further, incorporating that 'raked nozzle', with Both a 'larger mouth', as-mentioned above, and the 'funnel-throat' idea you / others mentioned..

..however, you might-still end up with the same bottleneck, where indicated, there.. Dunno.. SO... I got to thinking..

c) ..Sure, 'ideally' you'd have a 'worm-screw feed' to prevent clogs / positive-feed action, etc, but.. Ain't got no time for dat! BUT.. what about making up a small DIY 'ramjet' / venturi-creator / something that introduces a bit of 'eddy', right at the mouth, to help 'stir up' whatver was going in, ie:

..And, it would not (necessarily) have to be 'machined' (could make of wood or 'thermoplastic', etc, but.. Something really-smooth..) or too-hardcore, and you could experiment with what worked-best, on the 'leading end' (sharper tip, or more 'bull-nosed'..) as to what 'snagged less fetti', but..

..1. No moving parts 2. Even slightly 'restricting' the airflow, w/O actually blocking it, at that port, should (I think..) net the result of increasing air-flow speed / pressure, thereby 'improving suction', and, with the 'ram' going into the tube a bit, possibly serve as a 'passive clog-buster'... 3. If you wanted to get 'really fancy', I'm thinking a slightly 'spiral / fluted design' on this 'ram' could-possibly start to create 'rotational eddys', at that mouth, thus aiding in 'stirring-up' the air-flow a bit more.. Worth a test?

..Others have Ideas, off that? Perhaps, a 'combo' of the 3 - Large mouth / funnel throat / 'ramjet' inside, at the reduction, to aid with a bit of 'eddy' / vortex-generating (if spiral-fluted, etc..) Dunno.. If you wanted to get *really* really fancy, you could turn the 'ramjet' into a blower Nozzle, with 4 center-axis ports on the trailing-edge, fed from underneath by a tube-ported 'bleeder line', as was already suggested, as an 'inline turbo-flusher'..

OK, well, my Renders are done, so I gotta go hump a pillow..

fwiw..
j

[Datsurb]

If you look at the original hose that came with the blower, the end of it is cut in a 45deg angle. It is a reason for that. Find a way of having that tip installed imn your box. The angle makes the hole a lot bigger and the force of the vacuum is spread out of the lenght of the tube along the cut. This makes the confetti get sucked inn in the length direction.

No scientific mathematics behind this, but it seems like commen sence to me.

:-)

[planters]

At this point it seems like the part where the box connects with the tube sucks the air/fetti too fast because of venturi effect which could be slowed down with a funnel,

I do not think the velocity is too high. It's where the velocity BECOMES too low. The funnel would spread the velocity transition over the length of the tube and make any particular spot less likely to clog.

You're right that this is not a mathematical analysis and so you are at the point where you need to experiment. Try the beveled tip and try baffles that surround the hole that minimize any shoulders, approximating a funnel.

[Draco]

Vibrate it, in potato chip factories they vibrate the hoppers so the chips don't clog, and motor with an off balanced weight on the hopper might be worth trying, use some flexible coupling to the rest of the system