spider photo's

[Phizzy]

here are some photo's fo the spider
Phill

[Rod]

Hi Phill,

This is looking good. Guitar strings are definitely the way to go. My only question is how long is your spider hub? The taller it is, the larger the triangles formed by the wires and the stronger the spider. Yours looks quite short in the photo.

Good to see another wire spider being made.

Rod.

[bojan]

I see a problem: if ever motorised, you may experience vibrations, if the secondary assembly is not properly damped with some absorption material (like rubber foam).
In my case, it took me quite a while to sort it out - I ended up with rubber foam wrapped around spider anchor (at the secondary side), this was sufficient to dampen the vibrations induced by stepper PWM driver (in micro-step mode)

[Rod]

Hi Bojan,

My experience with a wired spider and a motorised scope has been fine. No noticeable vibration, quite the opposite in fact- it is extremely rigid. I think it is important that the spider be offset, as Phill's is and that the effective triangle be relatively large. A lot of spider's have the veins connect at 3 or 4 points on the hub which makes the spider susceptible to twisting.

If you have a look at Mel Bartels latest scope (trilateral mount) you will notice he uses a wired spider now too. I can't imagine him using one if he felt it was not compatible with a motorised instrument.

Rod.

[DaveGee]

Gtar string spiders are good! I've never had a problem with the ones in my 10". See... http://users.tpg.com.au/users/daveg/Cell.html
I made it so that each of the 8 legs could be adjusted so that precise adjustments could be made. I used 0.008" Gtar string wires.

[Phizzy]

Hi all
thanks for the info and kind words. I'm going to leave the height as is, for to moment, and see how it goes(seems plenty stiff). I may add argo navis encoders at some point but will not be motorising. The strings I have used are 0.66mm and are very stiff and hard to tighten so I am going to buy some thinner ones (approx 0.2 mm). Dave how did you make your adjustment pins (tensioniers)?? Its going to be a sanding and varnishing day today :(

thanks Phill

[DaveGee]

Hi Phil, They are made from M5 (by memory) stainless steel cap screws. They are a bit of a PITA to make.:P