re:worm drive -> rack and pinion

Lawrence,

Interesting thought. And the quick/slow (responding post) is
something I'll remember for later...

Now, as to your question:

Many things CAN work, but compared to what?

I'm understanding "ready rod" to be what I would call "allthread".
(standard hardware store threaded rod).

If so, the gain from this technique will be the cost difference of
ready rod vs. rack. Also, Rod may be easier to "mount", esp. in short
lengths (just "stretch" it between two holes appropriately
positioned). However, this will be offset by:

1)The time to make the "pinions".

2)The fact that worm gears are not designed to be rack/pinion. This
means the thread form (vee) will not carry anywhere near the load of
the acme rack, and the alignment between "worm" (pinion) and "gear"
(ready rod) will need to be MUCH more precise than std. 20 degree
pressure angle rack/pinion. And Loads will tend to "push apart" the
two pretty easily since the angle involved is 30 degrees.

(It's worth noting here that if you are designing a rack/pinion
machine, alignment(to eliminate backlash) will be helped by using the
older standard of 14.5 degree rack/gear)

3) The poor quality of most ready rod threads. Pitch variations/ bad
plating/ etc. (there's a REASON these things are cheap!

So, with the multitude of other options (rack/pinion, leadscrews,
belts, chains, cables, etc) you have available, I'd let this one sit,
unless you are looking for the fast/slow of that other post. Even
then, I'd think hard first. For the reasons laid out above.

On the other hand, if "ready rod" was acme threads... and I used
an "acme" gear (no real need to have the "worm style wrap-around"
threads, but you COULD) this would, IMO, be worth looking into. What
is the cost difference between acme "threaded rod" and "Rack"???

Hope this helps.

Ballendo

>I was wondering if anyone has tried making smaller diameter wheels
>that could be used as a pinion running on a threaded rod "rack". I
>am thinking of something in 1" pd wheel that would mesh with a 5/8"
>piece of ready rod...
>Lawrence Glaister