The premise of this book is that you can build a heat of the hand LTD Stirling engine without the aid of a machine shop, and without a lot of money. The tools listed here are the primary tools I keep handy in my tool box when assembling an engine. The process is more difficult than assembling a kit because it requires that you be able to manufacture your own parts from readily available materials.
Before you head to the store and start buying a bunch of tools, understand that there may be ways you can work around some of the more specialized items. For instance, you might be able to stop by a machine shop or an HVAC shop and have your aluminum parts cut for a small price, or even for free. This would eliminate the need for a nibbler in most of these projects.
Nibbler: (For cutting sheet aluminum to make the pressure chamber sides.) This is a tool designed to cut sheet metal without distorting it. Each of these engine designs requires two pieces of aluminum that are 6” by 6” square. Tin Snips have a tendency to bend and distort the metal as it is being cut, especially if the length of the cut is longer than the cutters on your snips. If you have a good set of tin snips and you can cut metal without bending it, then you can skip this tool. A nibbler can be purchased at better hardware stores for about $28. I got mine on sale at Harbor Freight for $5.
Possible workarounds: Metal cutting band saw, hacksaw, or a jig saw with a metal cutting blade. You might also be able to have your metal cut to size at a shop that works or sells sheet metal products.
I used the nibbler frequently when I was making engines that required round sheets of aluminum for the pressure chamber parts. I used it very little with these three designs because I purchased material that only required one straight cut to make both pressure chamber side panels.
Long Nose Pliers: (aka: Needle Nose Pliers) One or two good pairs of long nose pliers are indispensable for shaping small wire parts. If you have the ability to avoid the cheap tools, you should. The dollar store tools look just like the more expensive varieties, but they will bend when you try to shape high carbon music wire that is used in these projects.
Diagonal Wire Cutting Pliers: These are perfect for cutting soft wire parts, however for heavy wire cutting I like to use a pair of electrician’s pliers, and I use a file for cutting music wire.
Electrician’s Pliers: These are a great and versatile tool. They have long heavy handles and can cut through very tough material. They have large flat jaws that are good for working with sheet aluminum that needs flattening or straightening.
Sandpaper: I keep a sheet of 80 grit, 120 grit, and 220 grit within close reach while making all of my engine parts. Lay a full sheet on a flat surface and stroke small parts across the surface to shape and polish. This is another area where I recommend that you don’t skimp on quality. Good sandpaper looks expensive in the store, but it works so much better, and lasts so much longer than the cheap stuff that it is worth the extra expense.
If you will be working with acrylic (and you want to make it look extra nice) you should also have a variety of fine to very fine wet-dry emery paper in your collection.
Electric Drill and a Variety of Bits: If you are extremely careful you can drill all the required holes free hand. A drill guide or a drill press will greatly improve your accuracy and is recommended, but not required for these projects. A center punch is helpful for locating holes in aluminum, but is not recommended for use on acrylic sheet.
Drilling holes in acrylic will require the use of some modified or specialized drill bits. Regular wood bits cut at a sloped angle and have a tendency to be pulled into the material like a wood screw. This splits and cracks the acrylic. Drilling acrylic successfully requires the use of a bit that has a scraping action, rather than a cutting action. You can modify a standard wood bit to work well in acrylic, or you can buy specialized bits. Bits for masonry or glass use a scraping action to cut, and can be used in acrylic if they are sharp.
Digital Caliper: This is a tool that is very useful, but not required. We are building an engine that depends on close tolerances and precise measurements. Having a precision measuring tool helps in this regard. I picked up one on sale thinking it would be a novelty tool, but now I find I am constantly reaching for it. I am very sure I could build a Stirling engine without one, but sometimes you need an excuse to buy a new tool!
Utility Knife and Blades: A utility knife or an X-Acto® knife is helpful for cutting and trimming parts. I prefer the utility knife because of the stronger blade. Buy a pack of extra blades and change them often so that you are always working with a sharp knife.
Straight Edge: A 12 inch metal ruler will do the trick.
Square: It doesn’t need to be big. It can even be a small block of wood as long as it is perfectly square.
Ruler or Tape Measure: Most of the measurements in these plans are in fractional inches. You can use the scale of your choice. If you use something other than fractional inches you will have to do a little math to make the necessary conversions.
Coping Saw: A coping saw with a fine tooth sharp blade is a good way to cut the foam displacer by hand. But you can also use a utility knife, X-Acto® knife, a jeweler’s saw, or a jig saw. This tool is optional.
Cotton Swabs: Q-Tip or equivalent. These are great for swabbing up glue that oozes out in the wrong place. Also, you can rip the tip off and they make great stirring sticks for mixing epoxy.
Fine Tip Permanent Marker: Sharpie or similar type. A fine tipped Sharpie is handy when you need to mark directly on glossy surfaces that don’t take pencil or pen. But be careful because these marks are permanent.
Compass: This is the type for drawing circles with a pencil, not the gadget that points north! A simple dime-store compass will do the trick. It needs to open far enough to draw the outline of your flywheel.
Hammer: (For fine tuning your engine!) A standard duty claw hammer seems to be a handy thing to keep around. You may not need this, but it will be helpful if you need to flatten your sheet aluminum after cutting.
Adhesives: I use three types of adhesive: Silicone Glue, Epoxy, and Super Glue®.
The Silicone Glue is the same substance as Silicone II caulking compound except it is sold in a small handy tube that can be cut to provide a nice small bead of material. It is more expensive when packaged this way, but very handy. If you have made a pop can engine you probably used high temperature red silicone gasket compound. That is about the best silicone adhesive I have used, but the bright color is not pretty at all.
There are lots of choices when it comes to Epoxy. Drying times range from 5 minutes to 24 hours. (I have even seen epoxy recently that says it sets in 60 seconds.) I have been told that glues with longer curing times are generally stronger than the quick setting varieties. I have used both successfully. My opinion seems to change occasionally when it comes to picking my favorite variety of epoxy. There are some jobs where you really want more than 5 minutes to work with the glue joint. For those I will use a 30 minute or 60 minute epoxy. But for most of my work with these engines I really prefer the 5 minute variety that dries clear, or nearly clear. It lets you get a lot more work done in a day because you can glue some parts, wait 15 to 30 minutes, then start to use them. 5 minute epoxy really helps speed up your build time. If I can, I try to buy the epoxy that is sold in two separate bottles or two separate tubes. I find I have a lot of trouble with the epoxy that comes in the double syringe. It is difficult to get equal amounts of each part. And there is some cross contamination in the cap that causes the glue to go bad before I have used it all.
There are several kinds of Super Glue® also. The two basic divisions are gel and liquid. The liquid glue requires that your joint fit perfectly with no gaps. It will not fill a gap, and the glue will fail if your joint is not a perfect fit. Gel glues are designed to fill small gaps and are much more forgiving. If you can, buy your super glue at a model shop rather than at the dime store. They will have several varieties and will be able to offer advice on which glue is best for your application. The model shop will also sell a super glue accelerator that will speed up the curing process. This is especially helpful in dry climates.
Here is a good general rule for how to use adhesives in these projects: If you think you might need to take it apart to fix it, use silicone. If you are sure it can stay together, use epoxy. If you use silicone or epoxy on acrylic the surface should be roughed up with sandpaper or the glue will not hold for long. I make as few silicone joints as possible because they do seem to come apart fairly easy.
Acrylic Cement: While referred to as cement, it is actually a solvent. It is as thin as water. When applied to an acrylic joint it dissolves some of the acrylic material and then evaporates, leaving a transparent, welded seam.
Acrylic Tools: Acrylic can be worked with many of the same tools used for most woodworking projects. These projects will require that acrylic sheet be cut, formed, and drilled. You may be able to accomplish these tasks with tools you already have. See the chapter on Working with Acrylic for a detailed explanation. You must be prepared to safely cut and drill holes in acrylic sheet material that is 1/4” thick.
Heat Gun: Some of the designs will ask for small acrylic parts to be heated and bent. A heat gun works very well for this, but is not the only method available. Any heat source that can reach 300° to 350° Fahrenheit will work. A heat gun is also essential if you choose to make your own thermoformed diaphragms. A very hot hair dryer will sometimes meet the need.
Masking Tape: Tape will be used to hold glue joints while the glue sets, and to hold temporary assemblies together while parts are being shaped and fine tuned.
File: The best way to cut music wire is to score it with a file and then bend it and break it. Music wire is so hard that it can ruin a good pair of wire cutters or pliers.
Allen Wrench: There are several shaft collars on each engine. They are operated by a tiny Allen head set screw. If you put a piece of colored tape on the handle of the wrench (like a small flag) it will help prevent you from losing the tiny wrench on your busy workbench.
Infrared Thermometer: I purchased a cheap infrared “non-contact thermometer” from Harbor Freight for less than $20. It has proven to be a very valuable tool for measuring the surface temperatures of my engines when they are running. You don’t have to have one of these to complete these projects, but it is helpful in measuring your effectiveness.
Carpenter’s Sliding T-Bevel: A carpenter’s bevel is an adjustable gauge for setting and transferring angles. The handle is usually made of wood or plastic and is connected to a metal blade with a thumbscrew or wing nut. The blade pivots and can be locked at any angle by loosening or tightening the thumbscrew. It is a useful tool for building and mounting the pressure chamber, since it has some angles in it that are not square.
Soldering Tools: Building the crankshaft for Engine #3 calls for a sweat soldering technique that uses a propane torch. You can substitute a good epoxy for this step if you do not have access to soldering tools. The epoxy will not be as strong as a soldered connection.