PVC Oscillating Steam Engine

When I was in school and studying engines I always thought it would be fun to build a simple steam engine. In the years since I have built several simple oscillating steam engines that have run on compressed air. This one is built of simple products that can be found at the local hardware store.

• 1 - 1' length 1/2" CPVC pipe
• 1 - 1' length 1/2" PVC pipe
• 4 - 1/2" PVC Tees
• 1 - Small piece 1/4" Luan underlayment 1' x 1' will be plenty
• 1 - length 3/16" wooden dowel rod
• 2 - 7/8" Steel Flat Washer
• 2 - 3/16" Fender Washer (fender washers have a larger outside diameter than regular washers - these are about 3/4" outside diameter)
• 1 - 1/2" threaded PVC plug
• 1 - 1/2" CPVC cap
• 1 - 1/2" threaded PVC connector
• 1 - 1/2" thread x 3/16 barb adapter
• 1 - #6 x 2" tapered head machine screw
• 4 - #6 washers
• 2 - #6 nuts
• 1 - 2" trim nail
• 1 - Clear Epoxy (I used the one made by Gorilla Glue)
• (Optional) Super Glue

I spent somewhat time trying to find that perfect material to use for the piston. Finally I decided I had to make my own. Here's how I went about it. I cut a length of 1/2" CPVC pipe about 3/4" long. Next I took the pipe cutter I was using and split it lengthwise. Then I took a penetrating oil and sprayed the inside of the pipe well with it - this I figured would keep the epoxy from adhering to the pipe. Also as you can see in the second picture I put clear packing tape down on the board that the mold was setting on - I figured that the epoxy would not bond to that either. The rest was simple I filled the mold with epoxy and came back 30 minutes later - the results were satisfactory. To remove the newly molded piston I simply inserted a putty knife in the vertical slit I had cut in previously spread the pipe apart and presto - the epoxy plug popped out!

Take the 7/8" washer and place a piece of clear packing tape across the back. Next turn the washer over and carefully center a 3/16" fender washer in the center as shown in the picture. Now with the tape holding the washer spaced satisfactorily place a even bead of epoxy around the joint of the two washers. Repeat the same steps on the remaining two washers to create the second half of the flywheel. Set them aside to dry and we will come back to them.

Cut a piece of 1/2" CPVC 4-1/4" long. Next cut a piece of luan 1" wide and 2" long. Take a small drill bit and drill a hole centered from side to side and 1/8" away from the one end. Then take the #6 machine screw and thread it through the hole. The goal it to have it fit snugly in the hole if the hole is a little large add some glue to keep the machine screw in place. Now epoxy the luan parallel to the pipe 1-1/2" away from the end. This this piece of luan will later provide us with a flat side for part of the valve. And the machine screw will add the hinging action to our steam engine.

This is relatively self explanatory. Cut three pieces of 1/2" PVC 11/2" long and use them to connect the four tees to create the main frame as shown in the first picture. Start with the center two tees. Apply glue to the end of two of the tees then apply glue to one of 11/2" long sections of pipe. Slide them together and before the glue dries lay it sideways on your workbench and apply even pressure on both tees as shown in the second picture. This ensures that the tees are glued together squarely. Next glue the end two tees on to create a sturdy frame.

Cut two pieces of 1/2" PVC one 2" long and one 3" long. Cut a notch approximately 1/2" deep in the top of the 3" piece this will be for our wooden mount to slide into. Next drill a hole just larger than the 3/16" crankshaft 1-3/4" up from the bottom of each piece of pipe if you use a 3/16" drill bit you may need to clean it out to make it slightly larger than the dowel rod. These holes will be for our crankshaft to ride on. I used a drill press to drill these holes as it is crucial to make sure that they are square. However a handheld drill will work fine as long as you are careful to make sure that you drill as squarely as possible. Lastly add these risers to your frame. I do not recommend gluing these as you may need to adjust them slightly to allow the crankshaft to rotate freely.

This step requires that epoxy that you applied to the flywheel be cured. So if you just made up the flywheel you may need to sit back and watch the epoxy dry. Once it is dry take a five inch section of dowel rod and feed it through the first riser then add both halves of the flywheel and feed the crankshaft on through. Now you are ready to add the cam part of the shaft. For this cut a piece of luan 3/4" x 1-1/4" you will also want to dogear the corners on the one end. Now drill a 3/16" hole on the end that you did not dogear and pound a 2" trim nail through the end that you dogeared.

This is a relatively easy step. Simply cut a length of dowel rod 3" long. Then drill a hole in the center of the piston that we cast out of epoxy. Then apply a little glue and slide the dowel into the piston. Now you will want to check to see how freely your piston fits into your piston sleeve. I needed to pinch my dowel rod on my piston into a drill and rub the epoxied piston head against sandpaper until it was turned down enough to slide freely in my piston sleeve. Once it slides freely in the piston sleeve you will want to drill a small hole near the very bottom of the dowel rod. This hole should be just larger than the trim nail that is used on your cam shaft in the previous step.

This part is created from luan again, cut a piece 1-1/2" x 4-1/4". Then drill a small hole 1/8" down from the end and centered sided to side. Then drill a large hole 1-1/4" from the same end and centered (3/4") from side to side. For this hole I did not have the proper size of drill bit for my 1/2" plug to fit snuggly in the wood, so I used a smaller drill bit and reemed it out to the proper size to fit the 1/2" PVC plug. The 1/4" luan underlayment that I am using for this project is very forgiving and the 1/2" PVC plug was able to cut it's own threads and pulled in nice and snug. Now attach the wooden riser in the slot in PVC riser using either super glue or epoxy. As you can see I drilled a small hole for pressurized air to come in and a small slit for exhaust air to escape. I drilled the hole using about a 1/8" drill bit. The slot was created using a dremel rotary tool with a 1/8" ball head.

First dry fit the piston and piston sleeve. Then to make sure of proper placement of the hole in the piston sleeve take a piece of lead from a lead pencil and place it in the hole that you drilled in the PCV plug in the previous step. Now rotate the crankshaft while holding the lead all the way against the luan in such a way that it lets a mark when the piston moves back and forth. Now slide the piston back off and there should be a small arc on luan attached to the piston sleeve. Drill a hole on the left edge of that mark. Then reassemble the entire piston assembly placing four washers between the piston assembly and the wooden riser, one washer on the back side of the riser and using the two nuts jam them against each other to prevent them from working lose. Do not pull the nut to tight against the luan or the assembly will not be able to move freely.

As you can see in the previous photos I used the 1/2" coupler to couple my barbed fitting to the end of the 1/2" PVC plug that is sticking through the luan riser. Then I pushed the 5/16" tubing onto the barbed fitting and used the other barbed fitting to thread to our air hose quick coupler. This step can vary quite a bit depending on how your air hose assembly is set up.

First turn the regulator on your air compressor down to about 20 pounds. Then turn the air on and give your flywheel a gentle spin. If you have done everything correctly your engine should spin to life. If not don't despair. It may just need a minor tweak to get it running. Let a comment and I would be glad to help you!

Also remember the principles of the engine and don't be afraid to make your own spin of it using more PVC or less PVC, more wood or less wood, copper or brass. I would love to see what your imagination can come up with.