Sold tube to truss

dannat (Daniel) · #1 29-03-2010, 08:51 AM

Anyone got links for modifying a solid tube to truss style dob?

mental4astro (Alexander) · #2 29-03-2010, 10:24 AM

Hi Dannat,

Just how truss do you want to go? Reason I asked is I just ripped the components of my solid tube, focuser, spider, mirror and cell, and made the truss design fit them. If you want to just chop your solid tube to make it something like the SkyWatcher collapsibles, then that's something else. I'm guessing that's what you are after.

mercedes_sl1970 · #3 29-03-2010, 06:14 PM

Hi Daniel

You could have a look at Stellafane.org - it's great inspiration. However, it is hard to find detailed plans as so much depends on what you have at hand. As Alex says, you almost have to fit what you want to what you have.

Alex's scopes are great inspiration (well so-so I guess!!) - so too some good threads with Ian Ogilvie (stringscope) and Chris (scopemankit).

Good luck

Andrew

hikerbob (Bob) · #4 29-03-2010, 10:27 PM

"chop your solid tube to make it something like the SkyWatcher collapsibles"

Oh for an aftermarket kit to do just that.

Bob

dannat (Daniel) · #5 30-03-2010, 07:03 PM

yes i just want to cut 50cm out of the tube so i can get it into the car

alexch (Alex) · #6 31-03-2010, 01:14 AM

I had my 12" chopped 2 weeks ago and it worked great. We used hand saw to cut the tube just above the Alt bearings. Then bent the square aluminium tube to make two circles of the OTA diameter and pop-riveted them to the OTA. The two pieces are secured with nuts and bolts. Pretty basic but works well.

The square aluminium tube is from Mitre10 at $10 a piece.
I attached a few pictures I took today. A friend of mine has photos of the whole process in his camera so I will add those when I can get hold of them.
In the meanwhile if you have any questions - just ask.

Alex

mental4astro (Alexander) · #7 31-03-2010, 10:58 AM

Clever mod, Alex.

Steffen · #8 31-03-2010, 11:33 AM

That is a clever mod! Did you have trouble keeping the assembled tube square (straight)?

Also, may I ask what's at the end of that strap that hangs out of the PVC tube?

Cheers
Steffen.

alexch (Alex) · #9 31-03-2010, 11:57 AM

Quote:

Originally Posted by Steffen

That is a clever mod! Did you have trouble keeping the assembled tube square (straight)?

Not at all. To make a reasonably straight cut we put a nail in the vice and scratched the tube by rotating it. The end result was straight enough.

Quote:

Originally Posted by Steffen

Also, may I ask what's at the end of that strap that hangs out of the PVC tube?

Cheers
Steffen.

This is the Argo Navis stalk with the encoder cables hanging out.

Steffen · #10 31-03-2010, 01:33 PM

Thanks!

Cheers
Steffen.

bmitchell82 (Brendan) · #11 01-04-2010, 12:49 AM

theres a guy here on the forum named Doomsayer, he has done alot of work in this area, you should drop him a PM.

At the end of the day its all about what kind of finish you want.!

dannat (Daniel) · #12 01-04-2010, 10:02 AM

Alex, great work -just what i'm after...
does the Al tubing sit flush with the tube ends?

Also in the second pic which has the letter A's drawn on - it looks like the pop rivets are parallel to the tube - or am i looking at it wrongly? thanks daniel

alexch (Alex) · #13 01-04-2010, 04:26 PM

Quote:

Originally Posted by dannat

Alex, great work -just what i'm after...
does the Al tubing sit flush with the tube ends?

Also in the second pic which has the letter A's drawn on - it looks like the pop rivets are parallel to the tube - or am i looking at it wrongly? thanks daniel

Yes the aluminium square is flush (maybe 1 or 2 mm out somewhere) with the tube end.

The vertical pop-rivets hold the joint together, I think we used a rolled steel pin but you can do it by sliding a smaller square inside or even a strip of metal underneath and pop-rivet it.

To bend the Al square we used a 12" diameter pipe which was in the garage and a wooden block, then bent the Al square around the pipe. As it springs out a little the resulting diameter was almost perfect. The Al square is quite flexible so you can adjust it later easily. I guess you can find a suitable tree somewhere.

I will get the pictures of the whole process online but it won't be until next Friday.

Hope it helps,
Alex

mercedes_sl1970 · #14 01-04-2010, 04:30 PM

That's a great modification.

Andrew

alexch (Alex) · #15 10-09-2010, 12:45 PM

more pictures (took me a while to get them online)...

ZeroID (Brent) · #16 12-09-2010, 07:51 AM

Hey, nice 'How to" Alex. I note you have access to a good workshop but that kind of mod could be done with very simple tools in any garage.

Or as you say, a tree ....