- The worm shaft retaining rings are too tight causing the worm to 'bind'
- The worm/gear is too tight in the worm gear
- Mis-alignment of the worm carrier causes the worm to 'bind'.
The first two reasons are covered in the links provided. The last I found during the testing of the sprin-load attachment and found that if the bolt under the 'pivot' is tightned the worm/gear bind. If your mount exhibits this behaviour either leave that screw a bit loose or put some shim-stock between the motor-casting and the worm carrier at that corner.
Now, adjusting the worm/gear engagement on the HEQ5 is a pain as one of the setscrews is under the power/hand-controller panel. Here's a tough job that helps with single thumbscrew adjustment. To do this loosen all three screws, loosen the spring tensioner so that everything is loose and then turn the screw in to tension the spring and tighten the three silver capscrews. It's that simple; the implimentation is NOT.
Utilizing the genius of Dave Rubenhagen (again) a plan was put into effect. This would entail:
- Putting a pivot in the worm carrier near the gear-end of the worm.
- Attaching a fixture to the mount casting that would allow a spring to be tensioned.
Then he fired up the lathe and fabricated the pivot. This was made of brass and was sized to be pressed into the worm carrier, in essence becoming a part of the carrier. The bottom of the pivot protruded about .095" from the bottom of the carrier and was sized slightly smaller than the body of the pivot. The pivot also had a 'shoulder' at the top end so that it could be positioned accurately. When this was done the pivot was pressed into the worm carrier; it's tight, and if it ever had to be removed it's a machining job.
Then Dave made an aluminum 'bar' that would be screwed onto the motor casting and overhang the worm carrier. The holes in the bar were drilled and holes in the casting drilled and tapped. Then the bar was screwed to the mount using 6-32 stainless cap-screws.
The next step was to drill through the over-hang and into the worm carrier. This hole was 1) be tapped for the adjustment screw and 2) opened up in the worm carrier to accept a spring.
With the spring in place the worm carrier was positioned on the motor casting with the RA shaft/worm in place. The pivot kept the worm carrier registered in place. Two of the silver capscrews were inserted with JUST enough tension to keep the worm carrier settled while allowing it to pivot easily. Then the spring was inserted into the hole in the carrier and the adjustment bar screwed to the motor casting. Turning the screw in tensions the spring. It makes selecting a worm engagment REALLY simple.
With sufficient tension the worm can be turned with a thumb and finger.
Perfect (almost) worm engagement
- Set some (a bit heavy) tension on the spring
- Loosen the three silver capscrews so that the worm is pushed into the gear.
- Tighten the three silver capscrews
- Flip the gear on the worm shaft upside down
- Turn the gear with your thumb until you find a tight spot
- Loosen the three silver capscrews
- Loosen the tension on the spring until it's just barely pushing the worm into the gear
- Carefully... a tiny bit at a time... tighten the three capscrews until snug
- Re-flip the gear on the worm shaft.
Now your engagement should be set about as perfectly as you can. You MAY still have a mil of play at the loose spots, but that's about as good as it gets. If you want to set 'perfect' tension at any other spot just loosen the silver cap-screws, give the carrier a couple of light taps and re-tighten; the spring will bring the worm into the engagment you want.
During this process I found that my worm and gear were not perfectly aligned (not a rare occurrence). I discovered this while tightening the screw in the pivot. The worm transfer gear should move slightly when it's in place with good worm engagement. While tightening the screw I found that the worm became 'bound'; backing off freed the worm up. So I experimented with shims of different size until I found that the lead from a 1/8W resistor was about the right one. Dave had some .015" shimstock that he cut a hole in and now the shim sits around the pivot. The worm runs free. Of course, if the worm tightens up when the screws away from the gear are snugged, shim that side.
Truing up the motor casting on the end-mill
Drilling the dowel hole (reamed to size later).
Note the worm carrier is solidly in place.
The motor casting showing the dowl hole .100" into the casting.
This aligns with the hole in the worm carrier.
Turning the dowel.
The dowl pressed into place. It protrudes enough to seat in the motor casting.
Truing the adjustment block.
Drilling/tapping the adjustment block holes on the motor casting
Aligning the adjustment hole over the worm carrier. The hole in the block will
be tapped for a 6-32 cap screw. The hole in the worm carrier will
be opened up to accept a spring.
The adjustment block in place and semi-finished. The brass piece is the tail of a .015" shim. I discovered a worm/gear misalignment during this mod.
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