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The worm housing, supporting material will
be made entirely of metal and of adequate cross section to avoid all
flexure. The problem is that there is quite a space to make up between
the top surface of the 10mm support plates and the bases of the worm
housings. As can be seen by the height of the oak blocks in the images in previous posts.More on this later as my ideas coalesce into solid metal. Not rushing in produces dozens of different thought experiments before the precious [sic] metal stock is even touched. My present, favourite idea is a bar with a sturdy, vertical pivot at one end. Screw adjustment at the far tip will provide maximum leverage and sensitivity of fit between worm and wheel.
Interestingly, the RA worm housing needs to be lifted by about 66mm above the support plate for the worm to mesh correctly with its wheel.
I wonder whether the motor could not become a solid part of the support structure? The image shows the belt not quite tight enough with 5mm of packing between the motor and worm housing. 5mm channel, or angle, would fit between them nicely.
First I need a vertical face to screw the motor onto something. There are cutaway corners to the black body to allow long tools to reach the fixing bolts/screws/nuts. Though rods with threads could be mounted in the cutouts to support the motor from the opposite end. Motor support is usually from one end flange only just behind the pulley. Though this has some complications.
I have assorted plate including 10mm and 5mm, and some angle and channel. Though 5mm thick material between motor and worm housing doesn't leave any room for any other material under the motor. If I use angle profile under the motor that leaves no room for some means of support between the motor and worm housing. I shall have to think about this carefully. It seems a shame not to use the motor for solid support of the worm.
I still need worm depth of engagement adjustment even if the two become one solid unit. It would be better to have the motor protected by the worm and wheel if possible. A single plate could act as a bulkhead for the motor fixing screws and one end of the worm housing. Sadly, Beacon hill have been very mean with the worm shaft free length beyond the housing. If I push the pulley out any further [5mm] there is little or no shaft left to hold the pulley safely in place. As can be seen in the image inside the large pulley bore even though the pulley is pressed tight against the worm housing.
Perhaps I could counter-bore a much thicker joining end plate. Say 10mm tick with recesses for both pulley bosses? Thicker material would have enough room and strength for an upward facing pivot screw through the base support plate for worm mesh adjustment. The motor would be very firmly held down to the base plate once the pivot screw was tightened. The screwed mesh adjustment would take place at the far end of the worm and motor. This will keep it safely out of reach of the belt and pulleys.So far the worm housing is still only supported by one end. Now I need two overlapping angles in a squared 'Z' form to fix the worm housing down just inboard of the motor. The motor itself would rest directly on the 10mm main supporting base plate.
One angle profile would fit between motor and worm housing with the other leg turned downwards. Countersunk screws would join the worm housing to this top piece of angle. Both vertical legs of the angle profiles will be bolted firmly to each other. The lower piece of angle will rest on the base plate and will only be bolted firmly down once the worm mesh is set precisely. The angle section resting on the base plate will needs slots to allow some linear screw movement for worm meshing.
Some adjustment of the motor relative to the worm housing might be beneficial for belt tightness adjustment. Ideally the motor has to move away from the worm and wheel because the worm must mesh with the wheel. Not easy to achieve if the two are fixed to a face plate with recesses for the pulley bosses. Reaching the pinch bolts for the pulleys would need attention. Holes for a hex key? A slightly shorter belt would tension better with both worm and motor coincident. I have some 5mm channel which might tie the motor and worm more tightly together.
Adding an idler wheel [or bearing?] for belt tension adjustment to the front plate would be very easy. That would leave the position of the worm housing relative to the motor a much freer choice. See rough drawing above for the general layout.Posed shot of the unfinished motor plate.
Note the 6mm space between worm housing and motor ready for the support angle profiles.
I made the motor plate oversize [80mm x 120mm] out of a scrap of 5mm aluminium. This required a 36mm hole for the protrusion on the front of the stepper motor and a 32mm hole for the 34t pulley boss on the worm. I didn't have any drills or hole saws of the correct size so I bored the large holes in the 4-jaw chuck in the lathe. Hole saws would have been the best and quickest way to do these, preferably slightly oversized for clearance. I also drilled the four small, fixing holes for the RA stepper motor and clamped it temporarily.
Now I need to narrow the plate near the top to make room for the wormwheel and then drill some small holes to fix the end of the worm housing to the motor plate with screws. Then make the two nested angles in 5mm aluminium. I shall use Nyloc nuts and stainless steel screws to ensure these don't work loose. Though the motors are supposed to get quite hot in use. Which might suggest an alternative locking method. The close proximity of so much bare metal should help to act as a heat sink.
Click on any image for an enlargement.
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