Elmer's Grasshopper Engine
A new work in progress, this Grasshopper Engine has a lot of moving parts. Most of them are aluminum beams. I have a reasonable amount of aluminum stock but most will need to be cut from larger pieces and milled to size.
The first item I decided to make was the main column.
It started out as a slab rough sawed from a slug of my stock
It was first milled to the finish thickness, width and length. A few more hours at the mini-mill and it turned out pretty decent.
Next items were the main column fork and the brass valve forks. As a model builder I never throw anything away when it comes to stock. I had a rough piece of aluminum and a little 3/4" long bit of brass that I will use to make the forks.
As the pictures show those bits were just the ticket. I bolted the column for to the column to test the fit. The screws will be replaced with socket head bolts for a better look after I get my hardware list completed for this project.
The back column is a little more ornate. I wasn't real sure just how I wanted to approach it. I decided to drill holes that will form the radius of the cut outs.
I then drilled the two 3/32" holes through the width of the stock before cutting it to shape. The flat sides were set on parallels to keep the cross holes square.
It took some time to bring it to it's finished shape. I also made the beam tonight. It's in the scrap box. A simple piece, I just wasn't reading the print correctly. We'll try it again.
To take a little break from the milling I made the flywheel next. The stock came from an eBay buy of 3" O.D. X 7.1" long aluminum bar end. It may be the last piece cut from it because it's getting too short to hold in the band saw vice.
The first picture shows the stock faced to the 1/2" thickness. After turning the undercuts in the faces the spokes were cut out. I already showed my method of making a spoke flywheel on my Beam Engine build page, so I won't do it again here.
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The next thing on the list was to make the main bearings. The plans call for 5/16" stock. Again I don't have it. I do have a beat up old piece of 3/8, so I'll make them from it.
The two blocks were milled to the finish overall length, width and thickness, then the bottoms were drill and tapped for mounting to the base. They were bolted tightly to the base. I left them rectangular at this point to make it easier to grab them in the mill vise to drill the bores for the crankshaft.
Drilling them assembled will keep the bores in line. Be sure to match mark them when you take them off so they go back on in the same positions. I didn't have a 1/4" reamer so I drilled the bores .030 undersize then drill reamed them with a 1/4" drill bit. They came out to be .252" that will work just fine.
A little more mill work and they're done, almost.... They still need some polishing and and cleaning up, but they're well on their way. The second picture shows all the parts I have made so far loosely assembled for test fit.
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Next part was the crankshaft. A broken tap in the throw slowed this down a little.
Getting it out took some time, but it did come out without any damage to the threads.
The crank pin screw and shaft were both pretty basic. After pressing the shaft into the throw the crankshaft is finished.
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On a previous build I made a little error in making the cylinder. I didn't offset the stock properly and the valve surface flat was .030" too short. I decided to use that cylinder for this model. To make up for the .030" I will make the valve plate .030" thicker.
All the sizes were good, all I had to do was drill and tap the holes for the heads and steam chest.
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The lower head for this model was something I wasn't all that sure of how to approach. It's 5/32" thick with a 1/2" boss 1/32" high to pilot into the bore of the cylinder. All I have is 5/16" stock so it will take some doing.
First an oversize square was cut out of the stock on the band saw. I milled the edges square to the finish size and trued up the faces to give me something to indicated to for flat when I chucked it up in the lathe. The extra thickness gave me something to indicate to for centering it in the 4 jaw. It was then faced to the .156" thickness and the 1/32" boss was turned to fit the cylinder. I made a shallow center drill mark in the center after turning to make it easy to find center to drill the bolt circle on the mill. The bolt circle was drilled and countersinks cut it's done.
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The piston, connecting rod and fork were next on the list. Because it has to be fit to the rod I also made the outer head tonight.
The outer head is the same as on the Mine Engine so I won't detail it here. The connecting rod is simply a piece of 3/32" welding rod threaded 2.5MM on both ends. The plans call for a 3-48 thread, but since my model tap & die set is metric the 2.5MM is the closest match. The fork was milled from a small block of brass from the scrap box and the piston needs no explaination.
As of tonight it's at this point.
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The Steam Chest is one of the most entertaining parts to make on Elmer's engines. I may have documented it before, but it's worth running through again.
When I make them I start by milling a block of aluminum to the finish width, thickness and length. Then it goes to the lathe and is chucked up in the 4-jaw to turn the ends and drilling of the holes. The open end it tapped for the packing nut. After that it's back to the mill to cut out the middle pocket, drill the mounting holes and drill and tap the side hole.
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The valve rods always give me trouble. The one end it turned to .062" and it can be a little tough to cut if the tool isn't perfectly on center. Another issue is the slot in the one end. I decided to try something different this time.
I mounted the arbor of a Dremel abrasive cut off tool in the mill and centered it on the part. At .050" depth of cut per pass it worked perfectly! I then shifted it up and down to get the slot to the proper width. The end result was far better than any other method I've ever tried. Safety glasses are a MUST for that process!
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I spent a full afternoon finishing up the small parts that remained. It's Done.
Nice little engine, and it ran fairly well on the first attempt. After it's timed properly I'll post another video.
