Level Wind Mechanism - HELP!

I have put together a Level wind mechanism that uses a 1" steel bar 40" long
with a helix cut into the bar in opposite directions. At each end of the
bar the counterclockwise helix joins up with the clockwise helix. I am
using a 'key' that fits into the helix to travel along the shaft when the
shaft is rotated. The travel speed is about 12 inches per second, and I am
carrying about a 15 pound load on the key mechanism.
I am finding that the key (presently made of brass) wears down very quickly
(about 1000 cycles) and suspect that it may be due to two reasons:
1) The rapid change in direction hammers the key on the end of the spline
2) The key is not positively, centered in the spline when it reverses
direction, and during travel along the bar.
This causes the key to wear prematurely. I am tempted to build a steel key,
but fear that then the double helix bar will wear or fail, and it is fairly
expensive.
Has anyone had any experience that they would like to share on projects of
similar nature?
Thanks in advance,
Andy
snipped-for-privacy@triacengineering.com
Reply to
Andy K
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Do a goole search for amacoil. It uses a skewed ball bearing on a hardened shaft to give variable back and forth travel. Don Warner
Reply to
Don Warner
Andy K wrote: Has anyone had any experience that they would like to share on projects of similar nature? ^^^^^^^^^^^^ Printing presses use a similar device to drive the oscillating rollers. They use a steel follower in a steel groove, and get very long life. However, the loads are mostly inertial, where the roller reverses direction.
Could you relieve the follower of the radial load by running the shuttle along a track, parallel to the scroll-shaft, so the tension is not transmitted to the contact between the follower and the groove?
Could you put collars on the ends of the scroll-shaft, so the shuttle hits there, and relieves the delicate follower of most of the banging?
Reply to
Leo Lichtman
You could try making the key out of aluminum bronze instead of brass. I have some brass "things" that tend to wear rather quickly. I built them back up with TIG and Ampco 200 aluminum bronze. The difference is amazing. The aluminum bronze machines nicely, is much harder than brass and works well as a low friction match with steel.
Ted
Reply to
Ted Edwards
Did a job several years ago with the same "slamming" problem at each end. Is the helix constant in pitch right to each end? If so, change the pitch every few degrees so it is reduced on approach and increased on exit, ramping down and ramping up. i.e. assume 1.0 pitch, every 5 deg lose .1, so your pitch would go 1.0 to .9 to .8, etc. until it goes flat at turnaround point.
michael
Reply to
michael
Maybe a system like this would work. Two parallel lead screws geared together so the rotate in opposite directions. A traveler with a pair of halfnuts or chasers is mounted on a third smooth non rotating shaft. When the traveler reaches the end of one shaft it disengages and rocks over to grab the other reverse turning leadscrew. some kind of trigger and springs keep it engaged. Hey it's like 4 am and I didn't work out all the details. But I light try this since I have some long acme threaded rod and ground shafts.
Reply to
dann mann
How about placing sprockets at either end of the 40 inch run. Mount a link chain (motorcycle type) between the two with a single extended link pin protruding below that carries a suitable guide through which the cord, rope, cable, or whatever can be threaded. Drive one of the sprockets from the winding gear-train and you'd be off to the races. (In theory)(^:
Bill D
PS That's a bit fishing reel!!
Reply to
William G Darby
--What he said. Also google on the Uhing Rolling Ring Drive mechanism, upon which this thing is based.
Reply to
steamer

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