SW stock 2" Crayford on my 190MN mod

[Gtech]

I've found the stock 2" Crayford on my 190MN a bit weak in supporting heavier 2" EPs and dSLRs, so not having the cash to indulge in a Moonlight just yet (spent too much already) I decided to pull it apart.

The main problem being draw tube tilt when tightening the screw lock.

I initially thought this was down to slop in the draw tube but after a few hours fiddling I found there was more to it.

The Crayford spindle carriage is by default set too far from the draw tube (for light duty  purposes). This means that when you put addition pressure on the PTFE lined V block via the tension screw, it slightly bends the spindle up against the draw tube which is then counter rotated when you tighten the screw lock which causes the draw tube to tilt.

I initially tried honing  the draw tube flat to give smoother operation, but still had tilt (~1mm).

I then removed the V block and placed .4mm washers between the block and the tube housing. This lifted the V block closer to the draw tube, negating the need for excess tightening of the tension screw. I also loosened the carriage spacer grub screws in order to tighten the 4 carriage mount screws, moving the spindle closer to the draw tube.

The end result is less slop in the draw tube and significantly less tilt (0.15mm) when locking the tube. The spindle now rotates with less friction since the tension screw does not need over tightening to compensate for heavier loads (Canon 5D2).

I finished off with a collimation check and now wait for clear skies to do some image tests.

[laser_jock99]

Good investigation.