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Small, model sized worm gear reducer

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  • #16
    Good post Brian, I have one that looks identical saved from a Buick Regal , been going to see if I can turn it into a small winch for cocking a 150 lb. crossbow.
    James

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    • #17
      Hmm- beware- I took one out of a buick riviera, looked similar- those things get hot quickly. If you're not using the motor though, this isn't something to worry about.
      I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

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      • #18
        We used a motor like that on a robot projec (FIRST), and found out a #25 sprocket meshes well with the motor output. It worked really well - 72 tooth sprocket and that motor makes a lot of torque.
        When I get Time... I'll...

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        • #19
          The crankshaft on my engine was just a tad too short to put a pulley on. It stuck out about .28" from the edge of the flywheel, which was enough to get a .093 dowel pin through for my electric start adapter, but no room left for a drive pulley. Today I took a peice of 7/8" dia. 1018 mystery metal and machined a "crankshaft extender". Its bored 3/8" to slide over the end of the crankshaft, and is dowelled in place with a .093 roll pin. The large diameter has a groove cut for on o-ring drive belt, and the other end is turned to 3/8" dia. and cross drilled for the starter roll pin.
          Brian Rupnow

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          • #20
            It gets curiouser and curiouser---The machined and split hub has a clamp bolt which locks the hub onto the driven gear. The 5/16" diameter bent rod is pinned into position in the hub. There will be a 1.5" diameter brass ball with a 5/16" hole through it to slide over the rod, and a set screw to lock it in place at various distances out from the center of the hub. once I get the mounting bracket made up, the gear reducer will mount so that the pulley groove in it lines up with the pulley groove in the crankshaft extender that I put on the hit and miss engine. Then when I put an o-ring drive belt on it, and if I'm very very lucky, the brass ball will slowly rotate on the end of the arm. The axis of rotation will be horizontal. that means that whenthe 5/16" rod "arm" is swinging from bottom to top, the engine should be "under load" and should fire every cycle. Once the brass ball passes over the 'top" and starts back down, gravity will assist it, taking the load off the engine and hopefully letting it go into "miss" mode. I chose to use a worm gear so that the weight of the ball would not "back drive" the engine as it is on the downswing.
            Brian Rupnow

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            • #21
              Brian's next project?

              Well, he has this sow's ear and SWMBO needs a silk purse...

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              • #22
                Here are a couple of (from my point of view) interesting videos of the hit and miss engine under a variable load. It definitly does go in and out of hit and miss mode. However, its not CONSISTENTLY going in and out. Part of the reason for that is that my o-ring drive belt slips a bit, right at the crucial moment when the engine is supposed to be working its hardest to lift the weight. ---in fact, in one of the videos you can see my hand helping the weight "over the hump". Also, the fact that there is considerable tension in the drive belt (o-ring), means that there is some load on the engine all the time which imposes some load even when the weight is in the downswing side of its arc. The engine certainly doesn't lack for power. There are a couple of fixes for this belt slipping issue. I could go to a larger diameter pulley on the engine, which would give a larger contact area with the belt, but the slippage appears to be happening at the pulley on the gear reducer, not the engine. (All pulley systems slip a bit, its just not visible at high speeds). The better solution would be to substitute a pair of light sprockets and a roller chain for the o-ring drive and pulleys. A chain drive has a double advantage---zero slippage, and practically zero tension related drag on the engine. In the middle of one of the videos you can hear the chime that my wife rings to call me up to dinner!!! I have a two way speaker system between my office/test bench and the main floor of the house. The ratio between the engine crankshaft and the output of my worm gear reducer is about 137:1----not because I needed that much torque multiplication, but because I wanted things to happen in a slow enough time sequence that you could see and hear what was happening. As I started my preliminary testing, the first few weights I used were to puny for the engine to even notice that it was under a load. By the time I got to a load heavy enough to make the engine set up and take notice, the o-ring drive belt began to slip. I'm enjoying this, and it is very interesting.---Brian

                Last edited by brian Rupnow; 03-03-2011, 07:51 PM.
                Brian Rupnow

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