2Tim215

hand blower question

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Ok, I,m going back to charcoal and I built a box bellows - works nicely but has its issues. So I have decided to build a hand crank blower as they are almost impossible to find here and when you do, ridiculously expensive and have a question.

 

Does the impeller/fan need to be offset? My previous blower (that was stolen) wasn't and I read somewhere that it should.

 

Thanks

 

Tim

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Offset from what?

 

What issues are you having with your box bellows?  It would be a lot simpler to remedy what you have than start all over, imo.

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My old Champion hand blower from 1901 is nothing more than a gear box that turns the impeller.  The impeller itself is a series of flat paddles.

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Vaughn, the box bellows works like a dream - the issue being size - very big.

 

Kal, no problems with understanding how the whole thing works, I just read somewhere that if you offset the impeller you get better output. By offset I mean off center. Was just curious if this was true as I have never seen a blower with an offset impeller.

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There are lots of examples of home/shop made blowers in videos from 3rd. world countries on the net, the one that really sticks in my mind is a video of a fellow in Viet Nam who makes blowers from bicycles. The blower blades are slices of pop cans attached in the wheel rim running is a housing made from . . . cans. Some used the chain drives from two old bikes to gear the blower impeller up.

 

There are also good examples of vertical bellows some made by standing one barrel open end downwards in another drum open end up and filled with water. The inner drum has a simple flap valve to let air in and an outlet to the air supply line also probably with a flap valve. A lever arm to lift the inner drum and let gravity sink it sending displaced air to the forge. Need more blast put weights on the inner drum. It's an elegantly simple bellows with a reasonably small footprint able to supply quite a bit of steady air blast.

 

Frosty The Lucky.

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I think the OP is asking whether the impeller needs to be offset from direction of flow - i.e., a "snail shell" versus centered.  The answer is that the offset style blows with higher flow when the paddle is "pushing" in that direction but the centered type will blow equally well when the handle is turned in either direction.

 

I used to have a hand blower set up with two big v-belt pulleys to gain enough increase in speed at the fan.  I found an old blower housing that had been driven with a flat belt and used conventional pillow blocks and sheaves from WW Grainger to rig up the power train.  This was many years ago and I no longer have any pictures but it worked like a charm - put out plenty of blast - probably more than a Champion 400.

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Okay, that makes sense Harold.

 

No impeller blades don't HAVE to be shaped. Some are cupped, some are curved like scoops but I don't think it makes much if any difference in a hand crank blower. My champion 400 moves the same amount of air no matter which direction you turn the handle. One direction turns the impeller blades tangential to the air outlet and the other is of course the other direction. Same amount of air.

 

When I discovered it didn't seem to matter I couldn't believe it so I gave it a little test. I pointed the flex pipe so it pointed straight up and floated a light inflated ball on the air stream. Same cranks per second to float the ball.

 

I think what's happening in my blower is the blades actually make a low pressure zone behind them, draw air in from the center and there's no place for it to go but out the outlet.

 

I think it's more important for the impeller blades to fit close to the sides of the casing than have a particular shape. Of course that's just my thinking . . .<grin>

 

Frosty The Lucky.

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Frosty,

It's Hollis - not Harold - but I always liked that name so reckon I'll answer to either one. I also completely agree with your comment about having the fan blades fitting close to the housing as it's the only way to build pressure. Good observation...

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Thanks all. I am using a cast  volute from a centrifugal water pump that I was given that will work perfectly. At the moment I am busy with the drive train and "gearbox" with a 18:1 speed multiplication. This will be chain driven. Will post picks when done.

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Frosty,

It's Hollis - not Harold - but I always liked that name so reckon I'll answer to either one. I also completely agree with your comment about having the fan blades fitting close to the housing as it's the only way to build pressure. Good observation...

 

Hollis, got it. I know a H. Woolridge from Texas so coupled with the TBI I can blame it on the TREE! Now I'm wondering if THAT Harold IS in Texas. <sigh>

 

Oh NOW I feel soooooo smart, doing my final reread before hitting "Post" I see how you spell your name. Now I don't even have an excuse. <DANG!>

 

Frosty The Lucky.

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Hollis, got it. I know a H. Woolridge from Texas so coupled with the TBI I can blame it on the TREE! Now I'm wondering if THAT Harold IS in Texas. <sigh>
 
Oh NOW I feel soooooo smart, doing my final reread before hitting "Post" I see how you spell your name. Now I don't even have an excuse. <DANG!>
 
Frosty The Lucky.


It's cool, bro - no harm done - and you'd roar with laughter if you heard some of the handles I've been called over the years...like Wallace, Horace, Alice, etc. Nothing wrong with any of those names either - just funny how it gets butchered sometimes.

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A centrifugal compressor like forge blowers need to have a gap from the blade tip to the housing, the sides need to be as close as possible without rubbing. This forces the air to the outside then around to the single outlet. If there were multiple outlets around the circumference then the clearance could be tighter. If the clearance is inadequate and due to the single outlet you will actually have less airflow.

I replaced a set of blades on a champion 400 and the new ones I made were longer and the output was less than when it had some of the blades eaten 1/2 away by rust. I trimmed the new ones to match the original dimensions and airflow increased.

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Thanks. I have noticed that the blades were shorter than the housing space and wondered at this. The mind says bigger pushes more air but engineering it seems says otherwise. The less mistakes in this learning curve the cheaper.

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It's cool, bro - no harm done - and you'd roar with laughter if you heard some of the handles I've been called over the years...like Wallace, Horace, Alice, etc. Nothing wrong with any of those names either - just funny how it gets butchered sometimes.

 

Hollis I got. I've known quite a few, uncommon though the name may be. I missed how you spell your last name. Teach me not to read it all before opening my . . .er . . . start typing.

 

I don't imagine it'd be too easy to get you going about your name or variations, Frost has given me a lifetime's practice. I go by Frosty simply because it's easier to let people marvel at that than have to listen to some of the truly lame variants.

 

If we ever cross neighborhoods we ought to get together and swap Yearbook autographs. Nothing quite as lame as a high school kid trying very hard to be clever. Speaking of lame you might be surprised at how many folk can't spell Frost. <sigh>

 

Frosty The Lucky.

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