Finger Engine May 26, 2013 By Kaje at https://sites.google.com/site/lagadoacademy/home
A build log for this engine can be found here: https://sites.google.com/site/lagadoacademy/machining---lathes-mills-etc/build---finger-engine
These plans are a modified version of the NAMES finger engine plans which can be found at http://streffp-chs.wikispaces.com/file/view/FingerEngine-HSMArticle.pdf
Flywheel Shoulder screw Shaft Crank Set screw Connecting rod Post Lever Finger tab
Base
"finger-engine-by-kaje" © 2013 by Kaje at https://sites.google.com/site/lagadoacademy/home. This work is made available under the terms of the Creative Commons Attribution-ShareAlike 3.0 license, http://creativecommons.org/licenses/by-sa/3.0/.
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Finger Engine May 26, 2013 By Kaje at https://sites.google.com/site/lagadoacademy/home
Flywheel and Shaft Diameter 3” - 4”
NOTE 1 0.25 "
Mill flat 0.22” W
Center hole 0.250”
Shrink or press fit
0.563" (9/16) 1.75 "
Flywheel pattern (spokes, holes, solid, etc.) is irrelevant and is left to the preference of the maker.
Materials: Flywheel: aluminum, brass, bronze, etc Shaft: cold rolled steel, 0.25” diameter NOTE 2
"finger-engine-by-kaje" © 2013 by Kaje at https://sites.google.com/site/lagadoacademy/home. This work is made available under the terms of the Creative Commons Attribution-ShareAlike 3.0 license, http://creativecommons.org/licenses/by-sa/3.0/.
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Finger Engine May 26, 2013 By Kaje at https://sites.google.com/site/lagadoacademy/home
Post and Bearing Insert 0.67 " 0.38 "
Bearing Insert ~0.5 "
Drill and ream 0.500”
3.9 "
3.25 "
SIDE
0.75 "
Size for press fit in post
0.625"
Drill 0.375” deep and tap #8-32
0.5 "
1.24 "
BOTTOM 0.35 " 0.85 "
Materials: Post: aluminum, 0.5” thick Bearing insert: Bronze or brass NOTE 2
"finger-engine-by-kaje" © 2013 by Kaje at https://sites.google.com/site/lagadoacademy/home. This work is made available under the terms of the Creative Commons Attribution-ShareAlike 3.0 license, http://creativecommons.org/licenses/by-sa/3.0/.
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Finger Engine May 26, 2013 By Kaje at https://sites.google.com/site/lagadoacademy/home
Lever The drawing below is essentially the lever as it is shown in the original NAMES plan. The material is 0.250” thick aluminum. The raw stock (shown dotted line) is 0.750” W X 4.250” L. 0.375 "
0.800 " 0.25 "
0.5 "
Center hole 0.250”
0.125 "
0.75 "
0.25 "
1.75 "
1.625 "
0.2 "
1.875 "
0.65 " 4.25 "
0.5 "
Connecting Rod
Drill and counterbore for two #4-40 socket head screws
NOTE 3
Finger Tab
Drill and ream 0.250”
SIDE Drill 0.185 deep and tap for #4-40
2.926 "
TOP
3.45 " nominal NOTE 4 Material is aluminum 0.250” thick; make stock length longer to allow radius of ends 1/4”
NOTE 5 Material is brass 0.250” thick
"finger-engine-by-kaje" © 2013 by Kaje at https://sites.google.com/site/lagadoacademy/home. This work is made available under the terms of the Creative Commons Attribution-ShareAlike 3.0 license, http://creativecommons.org/licenses/by-sa/3.0/.
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Finger Engine May 26, 2013 By Kaje at https://sites.google.com/site/lagadoacademy/home
CRANKSHAFT The drawing shows the modified crankshaft. The material is 0.250” thick cold rolled steel.. 0.53 " Drill and tap #4-40 for set screw
Drill and tap #8-32
1.6 "
NOT TO SCALE 0.120 "
0.250” nominal
NOTE 6
Shoulder Screw (3 required)
1"
0.35 "
1.7 "
diameter 0.250”
Washers (3 required) NOT TO SCALE NOTE 8
0.375”
Material is brass or plastic, - outside diameter = 0.375” - inside diameter – 0.025” - thickness = 0.025”
0.281” Slot 0.06” W X 0.06” D
Thread #8-32
0.250 "
NOTE 7 Material is brass
BASE (not shown) SEE NOTE 9
"finger-engine-by-kaje" © 2013 by Kaje at https://sites.google.com/site/lagadoacademy/home. This work is made available under the terms of the Creative Commons Attribution-ShareAlike 3.0 license, http://creativecommons.org/licenses/by-sa/3.0/.
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Finger Engine May 26, 2013 By Kaje at https://sites.google.com/site/lagadoacademy/home
NOTES 1. The flywheel material can be almost any metal, although “heavier” (denser) is better (the original NAMES plans use a cast flywheel), to increase the angular momentum. By the same token, a larger flywheel is better than a smaller one, although I had good results with a 3” flywheel. The flywheel width is not critical, but if it is changed the shaft and bearing insert should be modified appropriately. The design of the flywheel with regard to holes, spokes, etc. is entirely arbitrary, and is left up to the creativity of the maker. The shaft is press or shrink fit into the flywheel. 2. The bearing insert is brass or bearing bronze, and is either press fit or shrink fit into the post. The insert is slightly wider than the post in order to provide a bearing surface for the crankshaft on one side and the flywheel on the other side; this eliminates the need for the shaft washers in the original plan. The insert is drilled and reamed 0.250”; the shaft should be turned and polished for a smooth fit in the insert. 3. The lever is modified from the original NAMES plan by providing a cut-out for the finger tab; in addition, the finger tab is mounted with screws from below instead of down through the tab. To make drilling easier, drill and counterbore the through holes for the screws in the raw stock before milling to shape. In this case I did not make a true counterbore, but rather approximated it with two different drill sizes. 4. The distance between centers for the connecting rod is critical. The ends of the rods are 1/4” radius nominal and are basically just milled for a good appearance. 5. The finger tab is made from brass 1/4” thick; the corners are rounded by filing, and a “depression” 0.150” deep is milled into the top surface using a rounded end mill. The piece is finished by smoothing with emery paper, followed by final polishing with a deburring wheel. 6. The crankshaft is modified from the original NAMES plan in two ways. First, and most important, the crank radius is increased to 0.350” (as compared to 0.250” in the original). Increasing the crank radius dramatically improves the ease of operation. Second, the crankshaft design is changed from a simple rectangle, and is made with heavier counterweighting; this not only improves the appearance, but I believe also improves operation. 7. The brass shoulder screws are slightly modified from the original, with a thicker head. The slot width is 0.060”, mostly because this is the slitting saw I had available; the top of the head can be left straight or given a slight chamfer (which I prefer). The length of the shoulder needs to be long enough to accommodate the width of the lever or connecting rod, and a washer, with just enough play to allow for easy rotation. 8. Washers can be made or purchased (#8 brass washer). However, they are very easy to make from plastic rod; I made mine from teflon rod, but nylon, UMHW, or any other flexible plastic would also work. 9. The base for the finger engine is nominally 5” x 5” x 3/4” thick; the bottom is drilled and counterbored for two #8-32 socket head screws to correspond to the screws holes on the bottom of the post. I made my base from red oak 4-1/2” x 5” x ~.7”, as that is what I had on hand. The exact dimensions are not critical, but the material chosen should be fairly heavy and solid, and should be sized to “contain” the engine for a good appearance.
"finger-engine-by-kaje" © 2013 by Kaje at https://sites.google.com/site/lagadoacademy/home. This work is made available under the terms of the Creative Commons Attribution-ShareAlike 3.0 license, http://creativecommons.org/licenses/by-sa/3.0/.
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