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Old 08-26-2017, 09:04 PM   #1
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Default Getting There . . .

Don't know if you don't try - [Bogs]

Thinking of making a Finger Engine, not a lot of parts involved, parts seem to revolve around the flywheel - Can't be a plain Jane, just wouldn't look right.
Curved Spoke would be nice - And that's how the fun started, after a few try's that need not be mentioned, switched over to Arduino GRBL to run the X-Y.
More hours than care to remember later, from gcode what? to arc tangent to two circles, say what later ['member something some 50+ years back, you will use this math later] Finally got a reasonable looking flywheel mockup.


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Old 08-27-2017, 06:11 AM   #2
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Lovely piece of work there Foozer.

I loved making finger engines over the years and made many gifts for friends.

Unfortunately there are two rules that must be followed.

The first is that you must get the geometry correct for them to work efficiently and you must get enough weight into the flywheel rim to store your finger pressure input to allow it to gain speed to keep the 'engine' running.

Here is one of 3 that I made, and although it worked fairly well, it just didn't have enough inertia to make a nice running machine, not only was it difficult to start in whatever direction I wanted, finger control made it rather difficult to control.



The cure was to insert heavy weights into the flywheel rim. Once this was done to all three engines, they worked perfectly.



I do hope that this helps.

If you need any further assistance, please be quick as the chest cutters want to take one of my lungs out in the very near future.


John


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Old 08-27-2017, 06:16 PM   #3
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Originally Posted by Blogwitch View Post
I do hope that this helps.
John
Have followed your postings all over the years. Have a couple pieces of 4.75od x 4.25id DOM steel pipe so was thinking [first sign of insanity] to make a web and fit it in. Have a grade school friend that last year had a tumor removed from his brain. It and the associated seizure's came back, he decided to not go under the knife again, just going to enjoy the time he has left living rather than spend the time worrying about dying. So this little planned gizmo is intended to be a toy for him to putt with. His meds tend to chuck his memory out the window so at times everything is new to him.

Off to check the setup and fab another mock-up . . .

Robert
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Old 08-27-2017, 09:17 PM   #4
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If you can put a steel tyre on it, it will help no end. The more weight you can get to the rim the easier the engine should be to run.

The only reason I told you about getting a hurry on was that any time after this Tuesday, I might not be with you any more, and won't be able to help anyone.

I will try to find my diagram that explains the geometry to model finger engines, if that is stuck to for both horizontal or vertical engines, they should work perfectly..


John
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Old 08-27-2017, 11:09 PM   #5
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John: Good luck with the surgery, hope you will be back soon spreading your wisdom.

John

ps: from someone who has been to the edge before.
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Old 08-27-2017, 11:35 PM   #6
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I have eventually found my working out diagram for finger engines, and if they are made to this formula, THE ENGINE WILL WORK.

The main critical bit is the length of centres on the con rod, it is the hypotenuse of the right angle triangle formed by the centre line of the crank and the vertical pivot of the finger crank. So when the main crank is at top or bottom dead centre, the finger input shaft should be standing vertically.



I hope I haven't confused you too much

John

PS, thanks W, but it doesn't look too good, something to do with all my other problems,.50/50 are the best odds they will give me..
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Old 08-27-2017, 11:44 PM   #7
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John,which dims are the starting point(determined by the size you want)
and which are then calculated to suit.If you get my drift.I very much hope
that you will be able to answer this in a few weeks time.All the best Barry
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Old 08-30-2017, 06:34 AM   #8
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After a few mock-up trials got the numbers and sequence down, now to try it in metal. Bogs, hope your upcoming adventure follows along the path of the latter mock-up and not one of the former...
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Old 09-03-2017, 07:11 AM   #9
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So did another, this time out of 0.250 AL, definitely not the same as cutting wood. Lets see, 4 minutes per pass, 5 passes per segment, 5 segments. Least it came out reasonably well and didn't go flying across the room. Now to dig up a piece three quarter thick, make the adjustments gained from this exercise and see what happens. Plan is to fab the web, fit it into the ring see how she does . . .


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