Sunday, December 21, 2014

Easy Bake Paint Oven

I have a lot of small parts to paint ranging from engine cylinders, rudder bars, and exhaust manifolds to small fittings.  Because I tend to get time to work during the winter I can't hang the parts outside to cure the paint.  I found that black engine enamel will get to about 125 degrees F hanging in the hot sun.  It seems to cure fairly hard at that temperature.  Rather than save all my parts to paint in the summer I decided I needed an oven.  For some small parts I've used the kitchen oven by heating it to 325 degrees, turning it off and the quickly hanging parts in it.  I just leave them until the oven is completely cooled.  It works for some small parts, but I really needed something a little bigger.  I was playing with Rowan my grand daughter and her Easy Bake oven when I realized this is just what I needed for painting parts.  It bakes small cakes and cookies by using a 100 watt light bulb as a heat source.  I figured if I used 4 100 watt bulbs in a metal box and insulated it I should be able to get it to somewhere above 125 degrees.  If I can get it to 250 degrees that would be great.

I haven't finished it at this point but I have enough done for it to start to make sense.  The next posts should be shorter as I get more done.

I had a sheet of 18 gauge galvanized steel which I was going to use to make a Gas Tank for the NINE.  I found a used tank which will need a minor repair to be serviceable, so I don't need the steel.

I drew my cuts and bends for the main box on the sheet and cut it to length.

To form the bends it would have been nice to have a 4' brake.  Instead I used some 2x4's and c-clamps.  I clamped it to the deck railing to support the clamped area while forming each bend.

I used another piece of 2x4 and a 6 lb. sledge hammer to form the bend.  You just have to keep working the hammer along the bend and bend it a little at a time and it works fine.

The ends are formed to a "C" or "J" shape by doing the outer bend first and then the inner bend for each end of the sheet.

Next the 2 back corner bends were made by the same process, except you can't clamp the middle well.

Our basic oven shell.
Next was the top and bottom ends.  The process is about the same but I used pieces of 1x4 clamped in a wide vise with c-clamps at the ends to hold it tight.  The panels are 20" x 23-3/4".  I made the short bends first and cut the blocks to 23-3/4" so they could make the long bends after the short ones.
I used a smaller block and mallet to form these bends.

They made nice bends.

The blocks fit nicely between the 2 side flanges to make the front and back bends.

I punched a 1/4" hole in each corner centered on the bend lines.  It makes a nice clean corner.

With the boxes formed I punched rivet holes about every 2" along the sides and back.  The front just hangs free.

I clamped the bottom or top in position so the front flange was even with the main box.

Rivet holes were drilled through the main box and steel Pop Rivets installed.

Holes were cut in the bottom for the light wiring and mounting holes drilled for the electrical boxes.  I used 4" ceiling boxes so the screws which hole the lights to the box also hold the box to the oven.

I made a card stock pattern for the legs to work out the dimensions.  I wanted them strong enough to not bend easily and to have a surface where adjustable feet could be installed.

The pattern dimensions were used to lay out four legs on a piece of the 18 gauge steel.

There are more cuts and holes then you might guess but as the bends are make you'll see why.

The first bend, up and down the middle, was done with the 1x4 blocks of wood in the vise with some extra clamps for tightness.

Again the block and mallet were used to form tight bends.

The next bend, inner foot plate, was done in the vise with the block and mallet.

The pilot hole, for the adjustable foot nut, was only punched in the outer layer because I knew I would never get the 2 layers well enough aligned for the hole to stack up correctly.

For the outer foot plate bend we're back to the 1x4 blocks and a clamp, all held in the vise so I can pound the bend with the block and mallet.

To make the foot plate stiff, both layers have a flange along the open edge.  The sheet metal pliers were used to form the inner bend first.

After bending the leg was turned right side up and the pliers pounded down to tighten the bend.

The outer layer was bent in the same way to almost 90 degrees.  The first flange is in the way to bend it all the way to 90 degrees.

The pliers were then placed to clamp both layers and the outer layer hammered down to tighten the bends.

You have to move the pliers to work the full length of the bend until it is all tight and square.

Next the flanges on the sides of the legs were formed by bending a little and the moving the pliers to slowly work the full bend to 90 degrees.

These flanges stiffen the legs so they won't buckle.  OK, it's overkill, but it was easy to do.

With the sides formed the leg is ready to add the nut for the adjustable foot.

The center of the inner foot plate was punched and the hole drilled to 5/16" diameter.  A clamp holds the inner and outer foot plates tight through the following processes.

The edge of the hole was chamfered with a 1/2" drill so the nut would set tight to the leg.

The nut was riveted in place with 3/32" Pop Rivets.

The inner and outer foot plates were riveted together.  You probably can park a truck on this thing now.

The adjustable foot just screws into the nut.

To attach the legs I made a template for the rivet holes.  The end hole was punched and the template clecoed in place.

The other end was clamped into position.

The other end hole was punched.

This end was clecoed and the rest of the holes punched in the cabinet.  This process was repeated for each side of each leg.

A leg was clamped in place and 2 holes drilled.

The template was then clecoed to the leg and the rest of the holes punched using the template so they would match the holes in the cabinet.

The legs were clecoed in place and riveted on with  steel Pop Rivets.

The legs came out great.

High temperature wires were run in the boxes and the boxes loosely screwed in place.

The switches were wired so each switch operates one light.  That way lights can be turned off to maintain a desired temperature if needed.

I don't plan to insulate the bottom initially to allow all this to stay cool, which is part of the reason for the legs, to let air circulate.

The light fixtures are for use with a 100 watt bulb in barns, etc.  They have a glass globe to protect the bulb.  The globe is protected by a cage so hopefully nothing will fall and break them.

The globe does not have a gasket.  I believe a little leakage is good so that as the air heats it can escape the globe.  I also expect the leaks in the oven and rising hot air will prevent paint vapors getting in the globes to cause an explosion.  Even so the box will be tipped back just enough to hold the doors shut.  I also plan to have 4 doors, 2 on the lower half and 2 on the upper half so if there is an explosion the doors will easily fly open without doing any harm.

To hang parts in the oven, I made 2 racks an upper fixed rack and a lower adjustable rack.  For the upper rack I used 2 baking cooling racks held below the top with eye bolts.  They are setting on the top to mark the location of the eye bolts.

The eye bolts had to be pried open to allow the rack to be installed.  Once everything was in position the loops were squeezed back closed to make the rack more secure.

It hangs about 1/2" below the top.  If needed the bolts can be re-adjusted to lower it.

For the movable rack I used the rack from our microwave oven which died while I was making all this.

I drilled 5/16" holes in the sides to allow the rack to hang from 1/4" threaded rod.  The ends of the rods are blunted for easier insertion into the holes.

The rack hangs from the rods with "S" hooks which are held in position on the rods with a nut tightened on either side of the hook.

The threads on the rods assure the rods won't slide in the holes.  To make sure enough rod sticks through the holes 2 nuts are jammed together 1" in from one end.

You stick the other end in first and then the end with the nuts.

If the nuts are tight to the wall you have 1" sticking out of both walls.

I then made a shelf to set on top of the movable rack to effectively shorten the box for smaller loads.  I'll insulate the top of this shelf.

I still have to make the doors and insulate the box.  With no insulation and a cloth covering the bottom half opening, I was able to heat the box to 125 degrees.