Science Teacher Needs Help With Lever idea.

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Science Teacher Needs Help With Lever idea.Hey, got an odd question. I want to make a lever to teach about force and simple machines. I want to make this from metal. I gave my wooden set up away in a teacher workshop (what can I say, she was a cute teacher..). I want to make it so the fulcrum is 2 feet from the load (a person seated in an old tractor seat). The effort arm (the arm you push down) I want to make in three or four 4’ sections. I want the section idea for storage and to illustrate leverage (the more sections you add the easier the effort). Here are my two questions:1.What size and thickness square tubing would you recommended for the effort arm? I’m assuming a load of about 225lbs2.What size tubing would you recommended for the “collar/sleeve” for each section to slide into?  ( I want a tight fit)
Reply:Rather than complicate matters with extendable lever arms what about a moveable fulcrum?A 12ft 65mm box sectionFucrumin from edge   Ratio2'                            5:13'                            3:14'                            2:16'                            1:1These ratios  you can explain why clocks are in 12's and degrees in 360's rather than base 10 . Early civilizations used base 12 and 60 .Just an ideaA good guess is better than a bad measurement
Reply:Brett That is sort of how the wooden one worked. I have a car not a truck and I do workshops all over the place on weekends so I need something that I can collapse.Cool Idea
Reply:Reebs, you can get ID/ OD tube to do this with. If you use 1.5"x.120 wall tube, you can make sleeves to go inside with 1.25"x.120. All you would need is a 9" piece for each sleeve. 6" extended out, and 3" inside fixed, either with welds or bolts. If you make each sleeve and receptor tube the same, you can interchange them easily to add the length right now quick, with only a push pin to secure the tube sections. The 1.5" will be plenty strong enough, yet still light enough that you won't kill yourself carrying it around.And then, after so much work...... you have it in your hand, and you look over to your side...... and the runner has run off. Leaving you holding the prize, wondering when the runner will return.
Reply:Originally Posted by RojodiabloReebs, you can get ID/ OD tube to do this with. If you use 1.5"x.120 wall tube, you can make sleeves to go inside with 1.25"x.120. All you would need is a 9" piece for each sleeve. 6" extended out, and 3" inside fixed, either with welds or bolts. If you make each sleeve and receptor tube the same, you can interchange them easily to add the length right now quick, with only a push pin to secure the tube sections. The 1.5" will be plenty strong enough, yet still light enough that you won't kill yourself carrying it around.
Reply:Or a cheap knock-off of the Rojodiablo design:  I suppose, threaded pipes and couplings would work too.
Reply:Originally Posted by denrepOr a cheap knock-off of the Rojodiablo design:  I suppose, threaded pipes and couplings would work too.
Reply:I got distracted...Yes I was going to suggest a 2" NB with 1 1/2" NB sleeve .I  add my approval to the above suggestions.I would weld the sleeve to the first one though have say 6-9" in and 6-9" out.Good luckA good guess is better than a bad measurement
Reply:How about robbing the extensions out of a HF porta-power?They must have a ton of "returns".
Reply:if your going to use the tubes as a sleeve, match drilling will help things work as desired.
Reply:for weight sake.  I would look at rectangular tubing with 1/16 wall.  Use bolts weld-on brackets for making it  portable.