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There seem to be a few Upshur builds going on at the moment, including mine. Ive been thinking for a while now about how best to handle the flywheels. After researching the Internet, Ive found that 3.5 flywheels with the required hub size and thickness are hard to come by. Taking that into consideration and the fact that I got into this hobby to learn machining techniques and help keep the ol brain synapse gaps firing, I decided it best that I make them myself. What follows is how I went about doing that using a Harbor Freight 7 x 10 mini lathe and mini mill (known to some as Chinese Crud ;D), coupled with a small sprinkling of ability and a large helping of enthusiasm. Compared to other this-is-how-I-did-it threads on this forum, this one is very basic and is geared toward someone who has never made a flywheel of this type before.
Ingredients:
3 dia. aluminum rod cut to 1 length (hub)
Mild Steel A513 Type 5 DOM Tube 3.5 x .375 x 2.75 cut to 1 (rim) 2 ea.
1 dia. aluminum rod - mandrel
For hit and miss, its good to have some flywheels with some heft to them to keep that momentum going between power strokes. Ideally they would be made fully of cast iron or steel. However, short of making a plate to mount the solid disk on, I could not think of a way to grasp the 3.5 diameter wheel on my small lathe so I could bore a hole in the center for the crankshaft/ mandrel. Unfortunately, the jaws on the mini lathe 4 chuck stopped just short of opening far enough for this purpose. So it is for this reason plus the fact that milling good-sized chunks of steel on smallish hobby equipment can be a pain in the a$$, that I opted to go with an aluminum hub pressed into a steel rim. The 3 aluminum hub is small enough to hold in the chuck jaws to bore the center hole and the steel rim adds the weight Im looking for. I ordered the cut steel rims from Online Metals at a cost of $3.65 ea.
Only one steel ring shown here but you need two.
I started by cutting two pieces of 3 dia. aluminum rod to about 1 in length. I dont have a horizontal band saw so I drug out my trusty battery-powered Ryobi Sawzall complete with good-sized metal cutting blade. If you have Ryobi +1 battery-powered equipment you know that using certain tools will drain the standard 18V battery quickly. For this chore, mine lasted about 3 minutes before it ran out of poop. I slapped in the Lithium Ion 18V battery ($$$) to finish the job. It had just enough charge to cut through. It took about 10 minutes total.
Using the outside jaws, the chuck on the mini lathe fell just short of opening far enough to encompass the 3 diameter aluminum.
Using the lathe, I trimmed the inside of the jaws enough to where they would grab the work piece and maintain engagement with the chuck gears. There was still plenty of meat in the jaws, so no worries about weakening them.
The hole for the crankshaft is .3125 so I drilled to .250 and modified a boring tool to fit inside. I bored instead of drilled the final hole size to ensure the hole was straight. If I had a higher quality lathe I would have drilled slightly undersize then reamed the hole to size but with this H.F. mini lathe, the tailstock is a weak point. It does not sit securely on the ways and can be tweaked by hand to present itself at different angles to the work piece, resulting in tilted holes. This is my impetus for a new lathe one day.
Drilling the 1/4" hole, followed by boring (not shown).
It should be noted here that a tapered bore can be used if one intends to secure the flywheel using a tapered bushing instead of grub screws. There are several threads in this forum regarding this. Dick Upshur mentions in the plans that the grub screw method is a possible weak point in the design and suggested drilling a blind hole in the crankshaft for the grub screw to nest into. For now, Im going with the grub screw scenario, two for each flywheel. I may have to go back and install bushings later but well see how it goes.
I made an aluminum mandrel that fits to the crankshaft hole and allows me to use the inside jaws to hold the work piece with no impediment to sizing the wheel diameter for press fitting inside the steel rim. I can also flip the wheel around now to face and shape both sides.
To make the mandrel, I took a 1 dia. aluminum rod and trimmed part of it down to fit the crankshaft hole in the hub. I drilled a hole through the mandrel center and threaded it internal ¼-20 so I can use a bolt to clamp the wheel down against the mandrel shoulder. The length of the shoulder is just short of the hub depth to allow the bolt to press and hold the wheel secure against the flat of the mandrel. Its also important not to leave a fillet at the mandrel shoulder to allow the hub to be pressed 100% flat against it. If you dont watch for this, the flywheel will likely wobble upon turning. DAMHIKT.
I mounted the disk on to the mandrel and skimmed the diameter to about .001" more than than the I.D. of the steep pipe piece.
I pressed the two pieces together using a high tech pressing tool. Manly-man muscle power is used for this chore. No wimps allowed.
Mounted on the lathe:
Back view showing the mandrel:
The grub screws go in the hub that faces outside of the wheel relative to the engine block. The plans call for extending the hub .125 out past the edge of the rim. I didnt see a way to drill a tap hole straight down into the hub without the rim overhang getting in the way. Im sure theres a method to do this or else the plans wouldnt have been drawn this way but being new to the hobby, I dont know what it is. I extended the hub out to around .200 so it would stick out past the rim a bit more, allowing the drill bit to clear the rim.
When mounting the hub on the mandrel, I used a flat washer with the same diameter as the hub (.625) with the ¼-20 bolt. This made it easy to reference the hub diameter. Using a carbide-tipped tool bit, I faced the side of the wheel to the proper depth relative to the hub. I started with a HSS tool bit but it was not up to the job once it hit the steel rim. I did switch to a 60 degree pointed HSS bit to finish the final shape of the aluminum portion of the hub.
I flipped the wheel around and did the same thing to the other side. To finish up, I beveled the steel edge of the rim and used some Scotch Brite to give the wheel its final finish.
Next I marked the positions for the six .75 holes that go through the wheel. For this, I mounted the RT on the mini mill. I have a small 3 jaw chuck that mounts directly into the center hole on the RT so the mandrel is automatically centered to the RT. To center the RT to the mill, I used a cone-shaped center finder lowered into the hole in the end of the mandrel (for the ¼-20 bolt) and watched how the edges of the cone section lined up with the straight section of the center finder main shaft. Its very easy to see and feel any offset this way and only takes a minute to line everything up.
You can see the cone is offset from the shaft, easily adjusted.
I zeroed the X axis DRO and stepped the table to the radius point for the hole placement relative to the center of the flywheel. I rotated the RT to the zero degree mark, put a center drill in the mill and pressed it into the aluminum wheel to make a small mark. I spun the RT 60 degrees (360/6) and did the same for the remaining holes. I did not want to actually drill the holes with this setup because it is not sturdy enough for a .75 dia. hole.
I used my Grizzly DRO to make the offset before marking the hole locations.
Marked hole locations.
To make the holes I mounted the wheel securely to some 123 blocks, drilled a .200 hole followed by a .375 hole and bored to the finished hole size using a boring head.
Looking good. Now if I can just get MB to send me his spare parts, I can finish it.
Trout.
See MB and Zee.... I am doing something, however slowly. *beer*
Ingredients:
3 dia. aluminum rod cut to 1 length (hub)
Mild Steel A513 Type 5 DOM Tube 3.5 x .375 x 2.75 cut to 1 (rim) 2 ea.
1 dia. aluminum rod - mandrel
For hit and miss, its good to have some flywheels with some heft to them to keep that momentum going between power strokes. Ideally they would be made fully of cast iron or steel. However, short of making a plate to mount the solid disk on, I could not think of a way to grasp the 3.5 diameter wheel on my small lathe so I could bore a hole in the center for the crankshaft/ mandrel. Unfortunately, the jaws on the mini lathe 4 chuck stopped just short of opening far enough for this purpose. So it is for this reason plus the fact that milling good-sized chunks of steel on smallish hobby equipment can be a pain in the a$$, that I opted to go with an aluminum hub pressed into a steel rim. The 3 aluminum hub is small enough to hold in the chuck jaws to bore the center hole and the steel rim adds the weight Im looking for. I ordered the cut steel rims from Online Metals at a cost of $3.65 ea.
Only one steel ring shown here but you need two.
I started by cutting two pieces of 3 dia. aluminum rod to about 1 in length. I dont have a horizontal band saw so I drug out my trusty battery-powered Ryobi Sawzall complete with good-sized metal cutting blade. If you have Ryobi +1 battery-powered equipment you know that using certain tools will drain the standard 18V battery quickly. For this chore, mine lasted about 3 minutes before it ran out of poop. I slapped in the Lithium Ion 18V battery ($$$) to finish the job. It had just enough charge to cut through. It took about 10 minutes total.
Using the outside jaws, the chuck on the mini lathe fell just short of opening far enough to encompass the 3 diameter aluminum.
Using the lathe, I trimmed the inside of the jaws enough to where they would grab the work piece and maintain engagement with the chuck gears. There was still plenty of meat in the jaws, so no worries about weakening them. The hole for the crankshaft is .3125 so I drilled to .250 and modified a boring tool to fit inside. I bored instead of drilled the final hole size to ensure the hole was straight. If I had a higher quality lathe I would have drilled slightly undersize then reamed the hole to size but with this H.F. mini lathe, the tailstock is a weak point. It does not sit securely on the ways and can be tweaked by hand to present itself at different angles to the work piece, resulting in tilted holes. This is my impetus for a new lathe one day.
Drilling the 1/4" hole, followed by boring (not shown).
It should be noted here that a tapered bore can be used if one intends to secure the flywheel using a tapered bushing instead of grub screws. There are several threads in this forum regarding this. Dick Upshur mentions in the plans that the grub screw method is a possible weak point in the design and suggested drilling a blind hole in the crankshaft for the grub screw to nest into. For now, Im going with the grub screw scenario, two for each flywheel. I may have to go back and install bushings later but well see how it goes.
I made an aluminum mandrel that fits to the crankshaft hole and allows me to use the inside jaws to hold the work piece with no impediment to sizing the wheel diameter for press fitting inside the steel rim. I can also flip the wheel around now to face and shape both sides.
To make the mandrel, I took a 1 dia. aluminum rod and trimmed part of it down to fit the crankshaft hole in the hub. I drilled a hole through the mandrel center and threaded it internal ¼-20 so I can use a bolt to clamp the wheel down against the mandrel shoulder. The length of the shoulder is just short of the hub depth to allow the bolt to press and hold the wheel secure against the flat of the mandrel. Its also important not to leave a fillet at the mandrel shoulder to allow the hub to be pressed 100% flat against it. If you dont watch for this, the flywheel will likely wobble upon turning. DAMHIKT.
I mounted the disk on to the mandrel and skimmed the diameter to about .001" more than than the I.D. of the steep pipe piece.
I pressed the two pieces together using a high tech pressing tool. Manly-man muscle power is used for this chore. No wimps allowed.
Mounted on the lathe:
Back view showing the mandrel:
The grub screws go in the hub that faces outside of the wheel relative to the engine block. The plans call for extending the hub .125 out past the edge of the rim. I didnt see a way to drill a tap hole straight down into the hub without the rim overhang getting in the way. Im sure theres a method to do this or else the plans wouldnt have been drawn this way but being new to the hobby, I dont know what it is. I extended the hub out to around .200 so it would stick out past the rim a bit more, allowing the drill bit to clear the rim.
When mounting the hub on the mandrel, I used a flat washer with the same diameter as the hub (.625) with the ¼-20 bolt. This made it easy to reference the hub diameter. Using a carbide-tipped tool bit, I faced the side of the wheel to the proper depth relative to the hub. I started with a HSS tool bit but it was not up to the job once it hit the steel rim. I did switch to a 60 degree pointed HSS bit to finish the final shape of the aluminum portion of the hub.
I flipped the wheel around and did the same thing to the other side. To finish up, I beveled the steel edge of the rim and used some Scotch Brite to give the wheel its final finish.
Next I marked the positions for the six .75 holes that go through the wheel. For this, I mounted the RT on the mini mill. I have a small 3 jaw chuck that mounts directly into the center hole on the RT so the mandrel is automatically centered to the RT. To center the RT to the mill, I used a cone-shaped center finder lowered into the hole in the end of the mandrel (for the ¼-20 bolt) and watched how the edges of the cone section lined up with the straight section of the center finder main shaft. Its very easy to see and feel any offset this way and only takes a minute to line everything up.
You can see the cone is offset from the shaft, easily adjusted.
I zeroed the X axis DRO and stepped the table to the radius point for the hole placement relative to the center of the flywheel. I rotated the RT to the zero degree mark, put a center drill in the mill and pressed it into the aluminum wheel to make a small mark. I spun the RT 60 degrees (360/6) and did the same for the remaining holes. I did not want to actually drill the holes with this setup because it is not sturdy enough for a .75 dia. hole.
I used my Grizzly DRO to make the offset before marking the hole locations.
Marked hole locations.
To make the holes I mounted the wheel securely to some 123 blocks, drilled a .200 hole followed by a .375 hole and bored to the finished hole size using a boring head.
Looking good. Now if I can just get MB to send me his spare parts, I can finish it.
Trout.
See MB and Zee.... I am doing something, however slowly. *beer*
