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Maff help

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    Im looking into turning my hand pump into a powered unit. Ive got several ideas on how I would like to do it. I just want to get some numbers nailed down before I shell out any cash on parts.

    Putting my pump on a cheapo bathroom scale it takes around 180 lbs to pump that thing on the hard end. It might be less but that is what it takes if I go slow on the stroke so I can clearly see the numbers scale up. The stroke is 16 inches. If I decide to go with a radial device the arm would be 8 inches long. What torque am I going to need at the shaft to turn that arm?

    Oh, that amount of force is only needed at the last couple inches of the stroke. So if the arm at that point is almost inline with the piston stroke would say a 200 in lb of torque do it?


    Max torque would be around 80Nm (whatever that is in king’s body parts measuring beats me). But that is only in “worst case” when arm is horizontal. Actual max. torque is lower.

    But 80Nm is BIG torque. Very BIG. It’s about the torque you have in small family car. So you need gearbox to lower the torque and slowdown the pumping cycle. Something like 1/100 or more might do it. The pump should be slowly operated. 1 stroke per 2-3 or even 5 seconds so that it’s not heating up.

    I recall that someone posted similar project some time ago here. Would be easiest to copy that.


    80nm = 60fp


    The gear reductions Im looking at are rated in “in lb” not “ft lb”. Whats the conversion on that? 12 X ? And I agree, metric would be so much easier than what we have now but we cant even get folks to all speak the same language so converting to metric is probably way down the list of things to do.


    X12 So 720 inchpounds



    Here’s a link to martin’s red neck compressor.


    Yeah, Ive seen Martins before and the vid. What happened to the video anyway? Im looking for a bit smaller footprint and something that wont need a leash on it ). Cost is a big issue as well.


    Google will convert any (that I’ve tried anyway) measurements.

    Some things will convert easily using just abbreviation, other things need the full name

    Just enter what you have and what you want in a search string


    “1 m in ft”

    “80 newton meters in foot pounds”

    quote Shadoh:

    What happened to the video anyway?

    I started with all the maff/trig. first. It got WAY out of hand in a hurry
    and I soon forgot the most basic rule–KISS (Keep It Simple Stupid)! I then decided to sketch just the basic geometry/dimensions and started throwing something together. That unit is butt-ugly and I laughed my ass off when I hit the switch but hey–it worked! The 1/2 electric motor would over heat so I upgraded to a 5 HP gas job–it just IDLES through 200Bar!!!



    Thanks Martin

    The shifter hanging off the side is the coolest part ).


    No-the coolest part is FREE! :mrgreen:


    Well, free to you maybe ). Not everyone has 100 bucks of free steel plus 50 bucks in hardware plus a 60 dollar motor plus a transmission laying around ).

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