Aluminium tubing as dovetail?

[zhgutas]

Hiya guys and gals.

I'm thinking of mounting a second dovetail to my 200p to

1) use as a handle

2) mount a piggyback guider/camera when needed

3) use as quick attachment points for dob alt bearings when I'm finally done with the base

Now my scope came with the shorter SW dovetail bar, and I could probably use longer ones for the ease of mounting the bearings etc.

Though wanting to spare the ££, could I use rectangle aluminium tubing instead?

I've found two pieces lying around,

both 380X42X20mm , and 2mm wall thickness.

I'm pretty sure these are gonna be OK for dob mounting, but are they gonna be strong enough for EQ?

Cheers

Marius

[Peter Drew]

I've used this material for dovetails but I've added a row of M4 mushroom head screws along one edge that sit in the angled part of the dovetail. If you leave the rectangular section as standard there is a danger that it will not be gripped adequately.

[zhgutas]

well,tried it today (no scope of course!)

and it holds really well from sliding or lifting (could easily lift heq5), but it slips at the angled part if tilted..

alrighty then, back to a drawing board..

[NGC 1502]

The dovetail has angled edges so it doesn't fall out. Could you not try Peter Drew's

solution ? Sounds like a good idea to me.

Regards, Ed.

[yesyes]

I love doing DIY jobs. But I don't think I'd risk building my own dovetail bar. Most of the rather pricey equipment rests on that bar. If that slips while everything is mounted on top....

[Peter Drew]

The screws that I mentioned in my earlier post sit in what would be the gap at the dovetail position if a rectangular section was in use, forming an effective angled face. Just as safe as a genuine dovetail bracket and a lot cheaper . Having said all this, the strength of the rectangular tube section has to be adequate for the job.

[yesyes]

Any chance of a picture of that? ;-) I can't really picture this in my head..

[zhgutas]

I imagine it's something like this? (yeah, very skillful work with sketchup, I know ) the blue thingies represent screw heads btw.

[yesyes]

aaaahhhhhhh, everything suddenly starts making sense ..

Thanks!

[Peter Drew]

Many thanks zhgutas, your sketch shows exactly what I was trying to describe..

[barkis]

That's a good solution, as long as the screw heads are butted against the angled face of the clamp. If the clamp contacts the rectangular piece before screw head contact is made, then movement could be possible. Especially during a pier flip.

Ron.

[zhgutas]

tried this with a couple of screws today, really works! actually, even one screw makes a huge difference (I ain't gonna try my luck with one screw though,no ).

of course it would help having a full-length angled section on the mount as in my sketch, but heq5 effectively only gives two points of attachment on the angled side, both 2cm wide, so have to the get screws as close together as possible. gonna try that properly for sure. Thanks a lot Peter!