Hobbing a worm gear Part 1 and Part 2

[kinetic (Steve)]

Here is a shot of the pan-tilt mechanism guys. Same as pic in post #136.

The 60:1 gearbox reduction is the heart of my GEM RA axis.
The smaller 120:1 reduction is the RA axis reduction of the Scooter GEM
in combination with the worm set also shown.

All up, very well built and slightly over-engineered , like most good quality
US stuff. What you want for the guts of a good drive system.
Steve

[kinetic (Steve)]

Towards the end of an imaging set last night the
DEC axis jumped out of mesh.

The cause???

I think the cause may have been flexure of the counterweight
shaft which made the gear drive slightly out of mesh for
quite a while.
This might be due to the CW shaft being only 16mm rod.
Most of the weights are at shorter extensions most of the time.
Because I have added an ED80 recently to ride atop the OTA, the weight set
has been further down the CW shaft, as much as 4" further than
it's normal position. This may have been enough flex to drive the DEC
worm slightly out of mesh.
Solution...make the CW shaft from something more substantial maybe.

As a temp fix I spun the chewed out worm gear section to a 'retirement'
spot 180° away from the mesh point. Greased up and back in business.
As the DEC axis functions mainly in Push TO mode, the only section of
DEC that I ever seem to use is a narrow bit for slight corrections
either side of an imaging field. (In GOTO mode I would have to rely on the
entire worm gear circumference though).

Steve

[kinetic (Steve)]

Dec axis all fine now. Here is a set tonight showing how well
she tracks in RA. This is Rho Oph close up at 1524mm FL and
a frame set of ALL frames stacked. Seeing was suprisingly good.
There was no guiding or corrections in half an hour of tracking
centred on Rho.
You can see the PE/ drift in the box where a hot pixel shows the worm
cycle. PEC was turned off.

Steve