A Tale of Two Helmets

You will recall from an earlier post that I was having some difficulty with my welding helmet.  It turned out not to be the helmet's fault.

Welding helmets come in a variety of styles, features and costs.  You can get an auto-darkening helmet for as little as $40.  I looked at one today that was over $500.  One needs to shop carefully.

The helmet on the left is the first welding helmet I purchased.  It was advertised as being suitable for TIG and, if I recall, was about $80.  It worked fine while I was learning to weld.  Most of what I was practicing with was 1/8" mild steel. In the learning process you start with thicker materials and work down. When I first started welding actual airplane parts I started having trouble with it "flashing" from dark to clear and back again.  Very annoying and not a good way to protect my eyesight.

It turns out that one of the specifications that affect the price of a helmet is how sensitive it is to the TIG arc.  That sensitivity is expressed in amps, as the amperage level that one is welding at determines the size and brightness of the arc.  The helmet on the left has a minimum sensitivity of 40 amps.  In welding aircraft parts one rarely applies more than 30 amps.  Therefore, the flashing. But the helmet would work fine if you are working on heavier materials, such as farm equipment.

The helmet on the right is the new helmet.  It is a Miller Digital Pro and it is about the minimum helmet I would acquire if I am working on airplane parts.  It has three sensors and is sensitive to TIG arcs down to 5 amps.  The kicker is that this helmet set me back about $250.

I really wanted a black one.  I am not that fond of the graphics, which are pretty tame here.  They can get quite wild.  But the local shop didn't have a black one and knocked a considerable amount of money off their tag price if I would take this one, the floor model.  I like to buy local if I can, and this worked for me.  At least it is not painted up like skull.

THE HELMET PROTECTS YOUR EYESIGHT. Get as much helmet as you need.  If you are working on heavier materials, or, at least materials that are not as light as what we work with building airplane parts, the $80 helmet would probably work just fine.  If you are working on lighter materials, as I am sure most of the folks visiting this site are doing or planning on, you are going to have to tighten your belt and loosen your wallet.

Hinge

Here is the completed aileron hinge:

The paint is a primer coat.  I haven't decided what color I am going to paint fittings.  Probably yellow.

The welding is gas.  Why you ask.?  Because it appeared that my welding helmet was still not functioning properly. So I did all the welding with oxy/acetylene, which can be done with simple welding goggles.  The welds are kind of ugly.  They are strong, just ugly.

I finally managed to talk to somebody at the distributor for my helmet.  It would have been "manufacturer" in the old days, but this helmet, as practically everything else, is made in China.  I explained the problem and what I had done to try and fix it.  They figured, given what I had done, that the helmet should work just fine provided I was welding at anything above 40 amps.  40 amps? This is aircraft welding.  I am rarely above 30 amps!

The upshot...my helmet is working just fine, it is simply the wrong helmet. What I really need is a helmet that will work down to about 5 amps, or maybe even less.  You guessed it. The 5-amp helmets are generally the top-of-the-line helmets.  The folks who make my helmet don't even offer one.  They recommended that I look at a Miller helmet.  Take the $80 I spent on my current helmet and multiply that by about 3.75.

Though I haven't actually run the numbers, I am beginning to get the feeling that I have spent more money on learning things than actually fabricating parts for the airplane.

The Saga of the Sons-in-Law

To begin with, the previously reported progress was a bit premature. I discovered that the aileron hinge I thought was complete was fabricated incorrectly.  I welded the bushing into the end of the tube and trimmed the tube around it.

It is not supposed to be that way.  As we go through today's post, I will demonstrate the way it is supposed to be installed.

Aside from mistakes resulting from mis-reading the plans, there have been production problems.  Drilling 3/8" holes, perfectly aligned, in the tubing proved to be a very challenging task.  There is a video on the EAA site that shows a gentlemen fabricating a v-block out of a couple of pieces of angle iron and then duct taping that to a piece of wood.  I believe this approach would work fine when drilling aluminum tubing, which is the case in the video.  It simply does not work when trying to drill steel tubing.

I discussed the problem with one of my sons-in-law who is an industrial engineer.  He described the method they use in his company.  It involves a basic v-block with a bushing attached to it to guide the drill bit.

I looked into this arrangement and found that it either required a rather substantial outlay of cash, or machine tools to which I have no access.

But applying the principal of keeping things rigid, I developed the following process, beginning with the acquisition of a pair of v-blocks, which took an inordinate amount of time getting here because they were coming from New Jersey at the height of the winter storm that hit most of the country.

Some of the photos I took today did not come out very well, so you will have to settle for narrative for the time being for some of the steps.  In some cases I will use the fuzzy photos.

The first step is to center the v-blocks in the drill press.  This is accomplished using an appropriately sized drill bit run into the center of the "V" and securing the vise.

In order to keep things rigid, and avoid a drill bit wandering around center before getting a grip, I used a center drill swiped from my Unimat (a small model makers lathe) to drill a pilot hole.  The center bit is designed to drill a countersunk hole in the end center of a piece of round stock for turning on the lathe.  It is a small bit with a fat body so that it does not flex and wander around.  I apologize for the fuzzy photo.

This pilot hole is centered 3/8" from the end of the tube to correspond to the outside diameter of the bushing.  Why would I choose that dimension?  Continue with the saga and you shall see.

The next step, without disturbing the alignment, is to enlarge the hole with 1/4" bit, which corresponds to the guide point on my step drill.

Once the top hole is drilled the bit is advanced to drill the bottom hole.  This is the place I took a bit of a chance.  The 1/4" bit is chucked in the drill press as short as possible to reduce flex, plus, I was hoping that the upper hole would help serve as a guide and steady rest for drilling the bottom hole.  It worked.  The top and bottom holes ended up exactly aligned.

After drilling the 1/4" hole I replaced the drill bit with the step bit.

And enlarged the top hole to the required 3/8".  I then flipped the tubing over, aligned the bottom hole (now on top) using the guide portion of the step bit, re-clamped it in the v-block, and enlarged the bottom hole.

The holes ended up perfectly aligned.  It seems like a lot of steps, but it really doesn't take very long.

The next step is to draw some lines extending the outside diameter of the hole to the end of the tube. What did we ever do before Sharpies?

And cutting out a slot whose width corresponds to the outside diameter of the bushing.

The reason this is done is because once the bushing is tacked into place, the ends of the tube will be heated up and bent around the bushing.  Below is the bushing ready to be tack welded in place.  It is cut long to facilitate welding.  Once welded into place it will be trimmed back to correspond to the outside diameter of the tubing.

And here comes the contribution of the second son-in-law.  As I was attempting to tack the bushing, my welding helmet would not work properly.  I have a self-darkening helmet. It darkened as soon as I struck the arc, and then promptly went back to clear!  It would oscillate back and forth.  I obviously could not use it that way and hope to hang onto my eyesight.

In discussions with another son-in-law, who happened to be visiting, he pointed out that the helmet is solar powered and perhaps all it needed was some recharging.  We shall see.  I have the helmet sitting in a window so it should have an opportunity to recharge while I am at church tomorrow.

Not wanting to abandon all progress, I tacked the bushing in using oxy/acetylene.  After I bent the ends around the bushing, I went ahead and finished up welding the bushing in place with the gas.

The above is the bushing finish welded, ground down to the proper length and reamed 0.250"

I had previously fabricated the brace, but I didn't have a useable bracket.  So I needed to make one of those up.  Here is the blank set up in my cheapy little Harbor Freight brake, which works quite well if you don't push it too hard.

Checking the first bend.

Set up for the second bend.

Checking the second bend.

And here are all the parts in the jig ready for tack welding.  We will see if charging the helmet works. I would rather tack this up using the TIG than the gas.

More as it happens.  Hopefully I am on the road to steady progress.