Small blower/vac with fanblade?

[Number21]

I want to build a gas powered blower/vacuum with a 6.5hp engine I have. I also have a big old 7 blade fan from a 70s ford big block which I could easily attach to the engine.

If I built a plywood/sheetmetal enclosure for the fan, with very close tolerences and a 6" suction hose/output port, would it actually have any sucking or blowing power? Or would it be better to design a blade from scratch?

[Treemonkey1000]

I think that I would just look for an old backpack blower from Craigslist or Ebay. If you have the skills and desire to try what you were thinking something that is already built up could be a thing you would pick up for cheap. It might need some work if you found one cheap enough. I use a backpack blower around my house and love it. Dirt and gravel as well as tree needles and leaves. It works good on cleaning out the gutters as well.

[RonMar]

I don't think it is going to work very well. That fan just wasn't meant to build any real pressure/vacume. Most fans are high volume low pressure devices, and as soon as you restrict their flow too much, they stall and cavitate and the air just flows around and bypasses the blade.

Vacumes use centrifugal blowers. These are capable of developing high pressure/vacume. You could probably make one out of a round plate and some carefully cut sections of large round pipe for the blades that would be welded to the plate. A little more calculation needs to be brought to bear as a 3600 RPM spinning plate can generate some pretty serious forces if something fails...

[MJPetersen]

Originally Posted by RonMar

A little more calculation needs to be brought to bear as a 3600 RPM spinning plate can generate some pretty serious forces if something fails...

Not to mention the critical balance necessary at 3600 rpm. The vibration of out of balance will take out the bearings in a small engine.

Mike

[Number21]

Originally Posted by Treemonkey1000

I use a backpack blower around my house and love it. Dirt and gravel as well as tree needles and leaves. It works good on cleaning out the gutters as well.

What brand is this? Would it literally pick up a pile of loose dirt/gravel?

I checked out craigslist already but didn't see anything but worn out cheap brand crap. I'm looking for lots of power.

[Treemonkey1000]

This is a Homelite Model UTO8111A. I don't remember the CC's of the motor. They make more powerful ones. Echo and Stihl probably. It will blow gravel. The tip of the hose is flattened out some to help aim the airflow better. It isn't the top of the line but it works well for what I need. The exhaust from the engine is even purged into the airflow.
Jim

[RonMar]

The backpack blower/vacs will vacume dirt and gravel, but it is not advisable as whatever is vacumed passes thru the blower impeller(usually made of plastic) and will eventually damage it. The Stihl handheld blower/vac I have, has a little chopper blade bolted on in the center of the impeller to shred leaves and grass to reduce the volume that is added to the bag...

[Treemonkey1000]

Good point Ron. This backpack blower just blows out air and doesn't pick up stuff. I will blow it into a pile if I need then shovel it.
Jim

[Number21]

Hmmm...I'm still wanting to build a vacuum with my 6.5hp engine...but I DON'T want the trash to be sucked through the blades...kind of like a shop vac.

What if I build my own 4 blade impellar using a 2x2 backbone and some 1/4" plywood blades. The inside corner of the blades could be cut on a 45* angle, much like some electric blowers I've seen? Obviously it would have to be balanaced, but I don't trust my welding at 3600RPM...

[Treemonkey1000]

You could just strap a shop vac onto your back. Drive it with a little 2 stroke motor...