Posting the following in case there is anybody else out there with a Skywatcher observing chair. Graman started this thread and devised a clever solution to modify the chair and make it less “lethal”. I have done the modification on my chair.
This type of observing chair seems to have a design fault, and relies on a seat that uses a pair of friction rollers to adjust and hold the sitting height. The problem is that the seat can suddenly perform a “posterior vertical displacement flip” resulting in one’s rear end hitting ground zero – possibly painful.
To work properly and safely, the sliding seat requires a force to be continually applied to the front edge. That force then prevents the seat from losing traction and dropping down the support tubes, hitting a dead stop at nearly ground level. The chair originally had a long spring attached to the front of the seat and to the foot of the chair. When the chair height was adjusted, spring tension kept a force on the front of the seat holding it in place. The original spring setup was pretty poorly designed and eventually became too stretched and inadequate to do the job.
I have modified my chair, and the attached photo shows the modification that Graman devised and it works well. Two vehicle spotlight clamps with heavy rubber bushings are secured to the outside tubes, and then two extension springs are attached from the front edge of the seat to the clamps. The seat and clamps are then moved up or down the tubes with the springs providing tension to hold the seat friction rollers in place. Probably not too many of these chairs out there, but thought I would post this in case anyone else has one.
The springs are from Bunnings and have the designation C-219 size – about $4.50 each. The clamps are via Amazon (search for SUZCO Spotlight clamps) and cost $15.95 for the pair which includes assorted rubber bushings and four clamp bolts.
Pics herewith
https://i.imgur.com/jeQT9Ejl.jpg
https://i.imgur.com/8QgDWS4l.jpg