The Seagull Part III: Sandblasting

This year I used a tool that I have never used before with any of my projects: a sandblasting cabinet, or glass beading machine. These sorts of machines come in handy for removing rust and paint off metal objects in a short space of time. Sandblasting leaves you with a nice smooth piece of metal, ideal for painting. If old paint is not removed, new paint may flake off and you can see old paint under the new. I don’t own one of these items but I was able to use one that belonged to the grandfather of a friend of mine.

Above: The sandblaster (0r glass beading machine).

Above: Inside – the red plastic piece is the sandblaster (the gun).

Above: The crankcase before sandblasting.

Above: Lower half of crankcase after sandblasting.

How it works:

There are several components to the machine that I used: the sand/glass mixture, the cabinet itself, the sandblaster and the compressor. The cabinet is the big metal box which holds the sand/glass mixture. Connected to the gun is the compressor. It takes in air and then pumps it through a hose to the gun at extremely high pressure (above 80 psi). The magazine on the gun contains a generous amount of sand. As the air flows through the gun it carries the glass/sand mixture with it and blasts from the barrel of the gun at an incredible speed. The operator has to be able to hold the gun while sandblasting, so there are two black gloves which are fastened onto the metal box and won’t come out. They protect the operator’s hands from the tiny sand particles racing around inside the cabinet. There is a little window at the top of the box so you can see where to aim the gun.

Operating Procedures:

  1. Fill the sandblaster with sand
  2. Turn on the compressor
  3. Place the soon-to-be-blasted piece
  4. Close the lid
  5. Start blasting!

Sandblasting is very effective when you have a rusted old motor like the Seagull. Old rust is gone is a matter of minutes, depending on the size of the piece you are sandblasting. Sandblasting it also very fun!

Advertisements

The Seagull Part II: Taking it Apart

A few months after last year’s final 4-H fair I got to work on restoring the Seagull. I began at the beginning: taking it apart. There was a lot of rust, dirt, and the gearbox behind the propeller was full of an ominous looking sludge. I looked like a drop of seawater had gotten in at some point, it’s a good thing there was oil in there or the corrosive salt water would have rusted the gears.

Above: The gear box after I drained most of the sludge.

After dismantling the gearbox, I removed the flywheel. The flywheel was stuck tight and it took a lot of hammering (and patience!) to get it out. I spend a five hours hammering, tapping, prying and levering on it, and eventually it gave way. Why the hammer? On small motors the flywheel is bolted onto the crankshaft, which is usually tapered. Hammering gently on the flywheel while a helper pulls up will loosen it from the tapered end.

Above: A hammer is a useful for removing flywheels. Don’t get rough!

Above: One end of the crankshaft. Note the taper.

Many of the bolts were stuck and rusted which made it difficult to take them out. When this problem comes up, be very careful. The last thing you want to do is break a bolt. On British Seagulls the bolts are all Whitworth sizes – somewhere in between metric and imperial – but not quite a perfect fit on either of these sizes. Whitworth wrenches aren’t something you can find at your local Canadian Tire store and buying replacement bolts is difficult too; regular hardware stores don’t carry anything that fits. It’s best to go to a specialist.

Now I had an awkward combination of problems: jammed bolts and tools the wrong size. Eventually, by combing through my grandfather’s tool room I found a bit which fit quite well onto the desired bolt. I carefully loosened the bolt by slowly pushing the rachet back and forth. This can break the corrosion holding a bolt in. I levered the ratchet back and forth, gently, loosening all the rust and dirt around the head of the bolt. Whether it takes one minute or one hour, take your time with this process. You don’t want to break anything!

British Seagulls are water cooled: Water from the ocean is drawn in and forced up a pipe by an impeller to the block, where it fills a chamber that encircles the piston. On my Seagull this water chamber was heavily clogged with rust and it was obvious no water was going anywhere. In the photo below the engine head is removed to reveal the four inlets from which you can access the water chamber. This is handy because through these inlets you can see and clean inside the water chamber. The rusty material blocking these inlets is the rust.

Above: The block, note the water chamber inlets. There are four inlets, one on each side.

Above: The inlets to the water chamber – much more visible after sandblasting.

Above: The crankcase. It splits in half, making it easier to take the cams and piston out.

Next, I’ll talk about the fun part: Sandblasting!