DRIVE GEAR & WORM question

I'm restoring and old small tractor...
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I need to make the stearing... I have a worm and drive gear... But...
Turning the stearing wheel CW. with the worm on the end of the shaft
make the drive gear turn CCW looking at it from the top down... My
question is can I buy a worm set that runs the drive gear Cw when the
worm is turning Cw ??? Would a reverse tread worm work that way ???
PS... Does any buddy have a standard twinn engine for sale???
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Hey Kevin,
I think I understand what you want to do, but I can't say I fully grasp what it is you are saying, as I don't understand how you determine "looking at it from the top down" causes CCW rotation. But the answer is yes, if you can come up with an "opposite-hand thread set" to what you have now.
But why not just use the set you have, and locate the worm on the opposite side from where you have it now. Only simple explanation I can come up with is:
Draw a snowman, on paper, made with just two different sized "snowballs", of significantly different sizes, with the smaller one on the top. Now make the bottom one REALLY "skinny". That would be what you now have, where the smaller ball represents the threaded worm, and the larger "skinny" one represents the driven toothed worm gear (often called the "worm-wheel"). Now imagine or assume turning the smaller top one clock-wise causes the contact juncture at upper edge of the bottom one to turn AWAY from you, and note that direction somehow. Now draw the same snowman thing "upside down", so the small "head of the snowman" is at the bottom of the drawing, and the "skinny" part above it. Turning the same smaller one again (now at the bottom of the larger skinny one) in the same clock-wise direction as before will cause the contact juncture of the driven worm-gear to turn AWAY from you again, but note that this driven worm-gear is now rotating in the opposite direction from the previous way.
The example(s) above will be shown to have a left-hand thread. If it were actually a right-hand thread on the worm (small ball), the contact juncture(s) would rotate TOWARDS you in each case, but again that would be opposite way in each of your drawings.
It takes some looking at a just a worm-gear to determine what hand it happens to be, but it is very easy to see on the worm itself. One thing that does happen is that the "thrust" caused by turning the worm changes with it's rotation direction. This may not affect you, because you would be rotating in both directions for steering, and so will require handling thrust in both directions anyway.
Take care.
Brian Lawson, Bothwell, Ontario.
Reply to
Brian Lawson
Brian. You are correct about just turning the set upside down. However, there is the problem of lubrication. You want the worm to always carry the lube upwards towards the gear. Unless they set is fully encased and filled pretty well with lubricant. In most steering gears, the gear is only a small part of a complete gear, a "sector" because the required motion is quite small. Brian needs to study the steering system on a more modern tractor. Perhaps even take it apart. Or just use it on his old tractor.
With only the single picture of the tractor, we can't see much about the steering components, but looks like a standard tie rod connecting the front wheels. Somewhere there also needs to be another lever arm to connect one wheel to the steering gear he is trying to create. He also needs to determine where his gear set will be mounted. Under the axel, behind the axel, or in front of the axel. Or will there be another long connecting rod with the steering gear mounted in the "cockpit".
Brian needs to describe the actual geometry of the tractor's steering.
Best regards, Paul, KD7HB
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