An almost finished dobsonian mount

[slowflow]

I picked up an unmounted 12' telescope last week & started making the mount on Sunday. Just could not help myself & had to try it. During a break in the weather last night I got 10 minutes of cloud free sky looking through a wet window & still was pleased to see the 2 stars of the southern cross pointer. It was really exciting, this is my first telescope. :D Other bits are drying in the garage now, hopefully it will be finished this weekend.
i am having trouble sourcing virgin teflon in Aus, does anyone have a source that is reasonable in quantity and cost? Thanks

[barx1963]

Hi Barry
Scopestuff in the US is one source I know of. The link is here http://www.scopestuff.com/ss_ts31.htm

Malcolm

[gary]

Hi Barry,

Congratulations on your mount and your first telescope!

Teflon is a Dupont brand name for a type of plastic known as PTFE.
We purchase some of our engineering plastics from Dotmar here in Sydney -
http://www.dotmar.com.au/ptfe.html
You could give them a try to see if they have some suitable off-cuts or perhaps put a query on the ATM forum.
Someone might even have some spare pieces.
See http://www.iceinspace.com.au/forum/forumdisplay.php?f=17

Best Regards

Gary Kopff
Mt Kuring-Gai NSW

[ZeroID]

I wouldn't worry about it being Teflon to be honest. I used some of that box strapping plastic with the moulded in fake webbing effect. Stapled it at either end of the half circle and it works a treat. It is less affected by dirt or contamination with the slightly raised knobbly surface it has and has the added advantage of not only being freely available but free ...
Doesn't seem to suffer from 'stichion' problems either.
Try it while you wait for your teflon to arrive.... then sell the teflon on ... :lol:

[mental4astro]

Looking good Barry! :D

You can also get sheets of Teflon to the size you need from Cut to Size Plastic (http://www.cuttosize.com.au/). Calculate how much you'll need and order twice as much - this will deal with cut loss and any errors you may make leaving some backup material. That is unless you want to keep some up your sleeve for any other projects that come up. I've found these folks very obliging and helpful!

You can easily cut and machine the stuff yourself - its as soft as the plastic from an ice cream tub. Doing it yourself will also save you a packet! Just ordering the sheet to your dimensions will be less than a quarter the price of getting them to cut and machine the bits for you.

Quantities? The rule of thumb for Teflon is:

15pounds per square inch

This requires you to weigh the OTA and craddle assembly first to calculate how much you'll need for the altitude bearings. Convert the kg to pounds (lb) and divide this by 15. You'll get the total area of Teflon you'll need. The actual pad dimensions is then the quotient when the gross area is divided by 4.

For the azimuth bearings you'll need to add the weight of the rocker box to that of the OTA and craddle. You then go through the same calculations for the total area and then divide this by three for the three pads you'll be needing.

Cost? From my last dealings with Teflon sheet from Cut to Size Plastics I got a sheet of 250mm X150mm X3mm thick for around $60. This was two years ago. I've made at least five dob mounts from this, including for my 17.5" dob, and I've still got stuff left over for a few more.

Barry, show us the finished product when it's done!

Mental.

[brian nordstrom]

:D Hi Barry PM'd you on a piece of teflon I have left over from an ATM of mine .
Brian.

[brian nordstrom]

:thumbsup: Hi Barry , I PM'd you on the teflon , I have some for you .
Brian.

[Matt Wastell]

Looks great!