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Solid Aluminium Pier Extension


Mandy D
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With the planets getting higher in the sky and the imaging train on my RC6 getting longer, it has become difficult to get to the eyepiece of my DSLR, so I've decided that a pier extension for the Skywatcher 2" tripod is required. I have a piece of 4 inch diameter aluminium bar about 250 mm long  that is doing nothing so I figured it would do the job nicely and sit between the tripod head and my existing homemade mount adapter. Hopefully, it will be stiff enough! 😉 This afternoon I faced both ends of the bar and cleaned up the outside, but now I need the adapter, which is at home, for the rest of my measurements, so will continue this project tomorrow. I'm going to drill and tap each end of the pier at M12, machine a spigot on one end and a socket on the other to keep everything nicely aligned.

The photos show phase 1 of the project. More to follow!

Pier_Machining_01.jpg

Pier_Machining_02.jpg

Edited by Mandy D
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The Skywatcher 2" tripod I have has an M12 male thread and the Hercules mount has a 3/8" UNC female thread, so I previously machined an adapter to convert between the two, using a 3/8" stud in the top of the adapter. Now I just have to machine the two ends of the new pillar to match the spigot on this part and the recess on the tripod, drill and tap both ends M12 and fit a stud for the bottom of the adapter. Then the system can be used with or without the pillar and will allow compatibility with any 3/8" threaded photo equipment. If I fit dowels at the top and bottom, it can also be used with astro mounts. You can see the machined adapter under the Hercules mount in the photo.

AZ_Mount_&_Adapter.jpg

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Pier Project: Phase 2

I finished machining the pier this morning. The 65 diameter x 5 mm deep socket to receive the spigot on the adapter that goes under the Hercules mount caused some problems as I don't have a decent boring bar, so most of the cutting was done with a normal carbide tool, after drilling a 3/4" hole with a flat-ended drill. The finishing of the bore was done with a flimsy boring tool that vibrated all the time, so the maximum cut I could take was 5 thou. I really must get a decent boring tool. I have a nice tapping head, so tapping the M12 threads in each end was very easy at 40 rpm. I could have gone faster, but I'm always terrified of the tap shearing!

The photos show the machining process for the socket.

Pier_Machining_03.jpg

Pier_Machining_04.jpg

Pier_Machining_05.jpg

Pier_Machining_06.jpg

Edited by Mandy D
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Pier Project: Phase 2 - continued

More photos. These show the finishing process for the bore and tapping of the M12 female threads. Note the judicious use of card between the chuck jaws and the aluminium to prevent damage to the smooth finish. I learnt from machining the original adapter that aluminium marks all too easily!

Pier_Machining_05.jpg

Pier_Machining_06.jpg

Pier_Machining_08.jpg

Pier_Machining_07.jpg

Edited by Mandy D
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Just now, StevieDvd said:

At this rate I expect to see a diy Rowan AZ100 clone soon 😀

 

I'd love to, but I'm really not that skilled at machining. I am seriously thinking about how I might make a solid and effective AZ head, though, but doubt it will come to fruition. This pier took me to the limits of my machining skills and a bit beyond. It was a real learning curve.

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7 minutes ago, Alan White said:

I too love watching folks creating items, shows great imagination and skill.

Somehow I think it will be 'solid enough' to support far more than a telescope and mount.
That is a solid lump of a riser.


 

It is 7075 grade (high strength) aluminium alloy. It probably is overkill, but it was a lump of metal I had to hand and should give "adequate" stiffness in this application! ;)

I'm glad you are njoying the pictures. I will be posting some of the complete assembly on the tripod later and, if the weather ever clears, with the telescope mounted and pointing at the sky.

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Pier Project: Phase 3

Sometimes everything goes smoothly and without a hitch. Then there are those occasions when nothing does: Those days that engineers call "normal days"! This has turned into one of those days ...

As you can see from the last photo below, the pier fitted on the tripod perfectly and the adapter fitted on top of the pier. Well, at least, I thought it did, but then on closer examination there was a 0.5 mm gap between the outer mating surfaces. It had to be the M12 screw joining the two pieces that was too long. It really could not be anything else, could it? The socket on the new pier, into which the spigot on the adapter fits was at least a millimetre deeper than required to accommodate the spigot.

OK, no problem, just tap the hole in the pier a bit deeper and all will be well, I told myself and try a new screw. For some reason the new screw was binding on the threads in the adapter, so I ran the tap in again, but to no avail. I tried some M12 nuts on the screw and they spun up and down the thread without a problem. The old screw still went in fine, so I ran a different M12 tap in and eventually got the new screw to go in.

Great! Problem solved.

Nope! Still the same gap as before, so I measured the spigot and socket to check that I had clearance on the depth. Yes, I did. So I machined the socket a bit deeper as it still would not fit, as I was now running out of ideas. Would this cure it?

No, of course not, the socket was already deeper than it needed to be!

So, I took a closer look at the mating face on the adapter and found a 0.5 mm high burr all the way around it close to the spigot. Put it back in the lathe, machined it off, et voila! As they say en France.

I was hoping to get this lot assembled and photographed tonight, but it looks like tomorrow is the day for that, now! The photos show the pier assembled on the tripod as it was before I fixed the problem.

Pier_Machining_09.jpg

Pier_Machining_10.jpg

Pier_Machining_11.jpg

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If I was chucking a lump like that to machine the end I would have used a steady of some sort on the bar free end. I regularly counter-bore with boring bars held directly in the tool post and never get vibration so that might have been a factor? I have been using the Glanz bars successfully. This sort of bar https://www.chronos.ltd.uk/product/glanze-s12-k-pwunr-06-boring-tool-with-wnmg-06-insert/

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1 hour ago, Len1257 said:

If I was chucking a lump like that to machine the end I would have used a steady of some sort on the bar free end. I regularly counter-bore with boring bars held directly in the tool post and never get vibration so that might have been a factor? I have been using the Glanz bars successfully. This sort of bar https://www.chronos.ltd.uk/product/glanze-s12-k-pwunr-06-boring-tool-with-wnmg-06-insert/

Thanks. I'd been taking 20 thou cuts with a carbide tool when facing and roughing out the socket with no vibration at all. It was just the flimsy boring bar when I was finishing the bore. Having the tool below centre height certainly wasn't helping either, but I had no alternatives. The bar in your link looks like what I need and is certainly cheap enough.

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22 hours ago, Mandy D said:

If I was chucking a lump like that to machine the end I would have used a steady of some sort on the bar free end.

My reference to a steady was meant as a nudge to get the free end of the bar supported. If for any reason the cutting tool dug in then that bar could be out of that chuck before you could blink.

While I'm at it, spinning the bar between centres also a no-go without some sort of drive dog on the bar. If it stalls under cutting then the bar and drive centre burn. Not good. 

Just hints...................

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Pier Project: Phase 4

I finally found time to assemble this to the tripod complete with the Hercules AZ mount. I'm now just waiting for the weather to clear so I can get it outside and mount the RC6 on it to try the new Barlow and focal extender.

 

Pier_Machining_13.jpg

Pier_Machining_12.jpg

Edited by Mandy D
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Finally got a nice dry day and a bit of sunshine to test the new pier. With the RC6, focal extender and an extra 50mm of extension pieces plus a DSLR it was certainly not the weak link in the chain. With that load the Hercules mount is beyond it's sensible limit and would not actually hold the RC6 and D800 in the horizontal position with a single counterweight, but there was no movement in the peir.

 

Tripod_&_Pier_8168.JPG

 

RC6_Pier.JPG

Edited by Mandy D
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