Over the past two months we've covered the installation of a Vintage Air A/C system on my project '49 Chevy. Something you may have noticed missing were the louvers in the dash. The reason for this was because I didn't want to mount them under the dash where they'd be less effective at blowing air toward the driver and passenger's upper body, but I also didn't want to mount them in the dash, as I was hoping to maintain a period appearance inside the car. However, I finally decided to french them in the dash and make them as unobtrusive as possible.
I chose Vintage Air's Proline Rotary Vane louvers because I felt they were the most "retro" looking (if any aluminum A/C vents can be retro) and decided to make a hammerform to fabricate frenched housings that I could weld into the dash. Given that the dash is curved, I simply couldn't drill it and bolt the louvers in place anyway, so why not make a detail out of it?
Hammerforms are simple to make, and can be used to fabricate a variety of small panels. While I could have just welded a blind tube into the dash and ground the welds, doing the job this way allowed a nice radius to the edge of the hole in the dash, and made the welding easier. If you're going to make hammerforms, MDF is ideal, as it is available in various thicknesses, is easy to work with, and is strong. I used 3/4 inch plywood, as I only paid 20 cents for this offcut plus the hardware store had no MDF and I knew I'd only need to use it four times. However, MDF will last longer and won't split as plywood is wont to do.
To form the recessed sections...
To form the recessed sections in which to mount the louvers I purchased a 1 foot length of 3-inch-diameter mild steel tubing into which the Vintage Air Proline Rotary Vane louver would fit.
The end of the tubing was...
The end of the tubing was blanked off with a flat steel plate, which was MIG-welded into place. The welds were then ground and dressed.
This cover plate section mounts...
This cover plate section mounts in the center of the dash to the left of the speaker grille. Its curve matches the dash perfectly, making it a handy template to mark the curvature on the side of the 3/4-inch plywood used to make the hammerform.
Using nothing more exotic...
Using nothing more exotic than a 4-inch grinder with a softpad, a Surform, and 80-grit sandpaper on a block, the wood was shaped to match the curvature of the dash. While I'd usually use MDF, this plywood offcut from my local hardware store was ideal and should last the four times it needs to be used. As a bonus, the lines where each sheet is glued to the next made an ideal visual guide to getting the curve uniform.
I sanded the curvature of...
I sanded the curvature of the wood to match the dash cover plate, as seen here.
Obviously a compass and pencil...
Obviously a compass and pencil would be ideal to mark the hole to be cut in the curved section, but a 3-inch-diameter mini grinder softpad worked just as well, as it could be bent to match the shape of the wood.
Again, making do with what...
Again, making do with what was on hand, I used a 2 5/8 inch hole saw in a drill press to start the hole cutting because that was the largest size in my toolbox.
A 3-inch hole saw would have...
A 3-inch hole saw would have been ideal, but this way allowed me to sneak up on the final diameter using a drum sander in a battery drill. At least plywood is soft and easy to sand, as is MDF.
It didn't take long to enlarge...
It didn't take long to enlarge the hole until the tubing was a perfect fit.
Wanting to mark a line around...
Wanting to mark a line around the hole as a guide for sanding a radius, I taped an Allen wrench to a pen to ensure the line was equidistant from the edge of the hole around its circumference.
With the radius sanded by...
With the radius sanded by hand, the wooden form was clamped to another, larger piece of plywood and screwed in place. As the edge of the hole nearest the camera was pretty thin, and I knew it'd split when hammering the steel over it, I made a quick sheet steel brace to hold everything together at this point.
This is the completed hammerform,...
This is the completed hammerform, ready for use. This only took about an hour to make, and with a little thought and planning, similar forms can be made for a variety of tasks, such as taillight mounts and exhaust openings in rear pans or dash gauges. Your imagination's the limit!
The closed end of the tubing...
The closed end of the tubing was placed in the form and a Sharpie run around the circumference to provide a uniform mark for cutting.
I then followed the mark with...
I then followed the mark with masking tape, adding an extra 1/4 inch to provide a decent sized lip for final welding once the work was completed. Add too much and the piece will be harder to hammer over the form.
Though you can't see it, there's...
Though you can't see it, there's a reference mark on the outside of the tube (arrow) that aligns with the centerline on the hammerform, meaning the work piece can always be aligned. I cut a circle from 1/8-inch steel plate to fit inside the tube and clamped the work piece and the former to my bench, adding another clamp to stop it moving around.
I used this cheap, high-crown...
I used this cheap, high-crown faced body hammer to work the metal over the form-though a ball peen hammer would work just as well.
With the 1/8-inch plate keeping...
With the 1/8-inch plate keeping the base of the work piece flat, I gradually worked around the perimeter until the steel was shaped over the form. I had to move the clamp to access the front section, using a couple of thick washers to raise the clamp over the edge of the wood. The extra 1/4 inch I marked using the masking tape allowed a nice, but not too wide, lip for welding to the dash.
With the hammerforming done,...
With the hammerforming done, you can see how the work piece follows the curvature of the dash perfectly. A little dressing and filing of the lip to ensure it was flat and I was ready to move to the dash itself.
The hole saw and drum sander...
The hole saw and drum sander came out again to ensure the louver was a snug fit, this time using a rotary air grinder in order to spin the sander faster for steel.
Though I didn't want any modern...
Though I didn't want any modern components in my dash, I've driven this car without A/C and it sucked. I could have mounted the louvers under the dash, but I really wanted them pointing directly out at the passengers, like a modern car, so I decided to mount them with the top edge of the hole 1 1/2 inches down from the chrome molding that runs across the dash. This meant the headlight switch had to go on the driver side.
Again, the hole saw and drum...
Again, the hole saw and drum sander made light and accurate work of forming a hole into which the new section could be butt-welded.
The reference mark was transferred...
The reference mark was transferred to the outside of the work piece, allowing it to be aligned vertically. Here's the section tack welded in place.
Finish welded and ground down,...
Finish welded and ground down, I'm pleased with the results. While they're obviously A/C louvers, the brushed aluminum finish is more in keeping with the car than black plastic versions, which is why I chose the Rotary Vane in the first place. A little body filler and primer to smooth things out and they'll hopefully look "factory".