Saturday, November 12, 2016

Melting Metal at the Beach with a Hand Cranked Foundry Blower

I'd mentioned before that I wanted to try melting metal with a wood fire and manual powered air blower. I liked the idea since it sounded simpler than my oil burner regime and didn't require electricity.
I finally got an opportunity to try this when I received a blower for free at a garage sale. Apparently the previous owners had their house heater replaced, and the workers didn't want to throw out a perfectly good blower.
At first, I had the impression that the original housing would be to flimsy to bolt the required hardware to, so I decided to build a new one.
a free air blower from house heater

I used mostly leftover bed frame angle iron from the trailer project. To build the frame, I bolted the pieces together instead of welding in case I wanted to take it apart later.
drilling bracket
Laying out the frame.
layout of new blower housing
Marking the hole locations.
marking hole locations
Checking for squareness.
checking frame for squareness
Then for the bearing bracket, I used pieces from dismantled drawer slides.
blower frame with bearing brackets
I had to turn two bushings to hold the bearings.
turning bearing bushings
Boring the bearing bore.
boring bearing bore
I made both bushings from the same piece of material, one on either side. Here I am cutting it in half.
cutting bushings apart
Now turning the saw-cut faces.
facing bushing faces
Much smoother.
bushing faces faced
Drilling and tapping the holes for securing to bracket.
tapping mounting holes in bushings
And finally, tamping the bearings into the bushings with a brass hammer.
press-fitting bearings in bushings
The ends of the 1/2" rotor shaft had to be turned down to fit into the 12mm bearings which measured .472". These particular bearings were from the bicycle compressor after I took it apart. Now they get their second chance in building the bicycle powered furnace.
turning ends of rotor axle to fit into bearings
Drilling clearance holes in the brackets. Drilling through thin stuff like this with a large drill has the tendency to produce a non-round hole because of the drill wandering.
drilling clearance hole for axle
So who's selling the pentagon shaped drill bits?
Measuring where the set screw flat should be on the shaft.
measuring axle flat locations
Milling set screw flat and end flats for attaching drive train parts.
milling flats on axle
Trying a short crank arm on the shaft. Clearly this is not going to deliver enough air, so we'll need to step up the ratio.
blower with rotor and axle mounted
Removing the axle from a scrapped exercise bike flywheel.
removing hub from exercise bike flywheel
The crank and belt.
exercise bike drivetrain
The other crank arm had to be cut off in order to fit around the blower housing.
cutting one piece crank arm
Turning a new bottom bracket shell.
turning a bottom bracket shell
Using a round ended boring bar for the bearing contour. Honestly, I wouldn't be doing this if I had the correct piece of tubing sitting around (and the bearing cups from the one-piece-crank).
turning bearing recesses
Putting together the bottom bracket shell with the crank.
reassembling crank with new bottom bracket
Milling a flat on the bottom bracket shell to attach to blower. I then drilled and tapped 2 holes.
milling flat on bottom bracket
The drive train bolted on.
belt drive set up
A view of the bracket.
belt drive attached
Drilling more holes to make the tension adjustable. The slots were then filed afterwards.
drilling tension adjustment
Adding a belt tensioner as well. It's just a bolt that when tightened pushes the bracket to the left.
belt tensioner
Attaching the sheet metal skin. Actually, the most expensive part of this project was the bag of #10-32 screws for attaching the sheet metal.
sheet metal housing
I practically ran out of sheet metal in this project, and had to resort to taking apart some extra metal trays I had.
recycling some steel trays
I thought this thing was starting to look like it was made by the GLA from C&C Generals.
the foundry blower brought to you by the GLA
All done it seems, let's take it to the beach.
carrying blower on bicycle
Setting it up on a fire pit.
blower set up on fire pit
Starting the fire with a road flare.
starting fire with road flare
Soup can with melted aluminum in it.
aluminum melted in a tin can
After casting an ingot.
aluminum ingot poured at the beach
Part 2: Chain Drive Conversion
I was having issues with the belt falling off, so I decided to convert the thing to chain drive. Chain drive was actually my original plan, but I wanted proof that this thing would work before buying any extra hardware.
It turns out that the plastic belt pulley was not actually welded to the crank, but being held on with a hex-shaped boss.
removing belt pulley from crank
Fraudulent tack welds
Looks like I finally found a use for that 60 toothed gear. Plus, since it's aluminum, I'd never put it on a bike anyways....
50t gear vs 60t
50t on the left, 60t on right.
It appeared my only hope to attach this was to modify the crank to fit on the one piece crank bottom bracket.
turning crank arm
In addition to drilling a new hole, I had to turn a better diameter for chucking onto since there was barely any surface to grip onto.
crank arm chucked in lathe
Then using a triangular file, filing the hex. I thought the pattern looked similar to the Gangstarr logo. The crank arm almost didn't fit on the one piece crank since it was considerably thicker than a stack of sprockets.
filing hex drive
Then turning an 1.375"-24 adapter for the freewheel. Here it its next to the one for the belt.
freewheel hub adapter
All complete.
blower with chain drive

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