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How secure the 2 layers of a Velbon Super Mag to each other?

 
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JimGnitecki



Joined: 12 Sep 2017
Posts: 28

PostPosted: Thu Oct 26, 2017 4:35 pm    Post subject: How secure the 2 layers of a Velbon Super Mag to each other? Reply with quote

I just got a used Velbon Super Mag slider. It has 2 separate pieces:

- The "top "layer which adjusts the camera position towards or away from the subject

- The "bottom layer" which adjusts the camera position to the left or right relative to the subject

Eitherone can be used alone, but of course for precise macro composition and focus stacking I'd like to use them simultaneously, as the designer intended.

I cannot figure out how to attach the two layers to each other! I suspect Imight be missing a piece or 2 of hardware.

I have 3 photos:

1. The top layer: shown with its bottom side up,which attaches to either the bottom layer or to a tripod head directly, with provisions to accept either a standard 1/4" or 3/8" bolt

2. The bottom layer: shown with its bottom side up,which attaches to a tripod head directly, with provisions to accept either a standard 1/4" or 3/8" bolt

3. The bottom layer: shown with its "top" side up, which is supposed to somehow attach to the top layer. Note that the 3/8" bolt protruding from the top is "captured" (via circlip and body of the bottom layer), but is NOT secured against rotating. So, there is no apparent way to make it thread into the top layer,and even if it did,note that the bottom surface of the top layer and the top surface of the bottom layer are NOT flat so they could not be properly tightened to each other anyway!

What am I missing here?

Jim G

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cube-tube



Joined: 10 Oct 2017
Posts: 107
Location: Durham, NC

PostPosted: Thu Oct 26, 2017 7:22 pm    Post subject: Reply with quote

I have a very similar slider. I believe that it comes with the smaller rail on the bottom. If you move the position of the small bottom slider all the way to the left, the hole in the bottom lines up with the screw, so you can screw it into the top rail. Alternatively, you can thread the smaller rail on top through the slit on the end of the larger rail, but then you need an adapter on the small rail if you want to attach it directly to the camera.
That's all assumption based on what I have.
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JimGnitecki



Joined: 12 Sep 2017
Posts: 28

PostPosted: Thu Oct 26, 2017 9:01 pm    Post subject: Reply with quote

cube-tube wrote:
I have a very similar slider. I believe that it comes with the smaller rail on the bottom. If you move the position of the small bottom slider all the way to the left, the hole in the bottom lines up with the screw, so you can screw it into the top rail. Alternatively, you can thread the smaller rail on top through the slit on the end of the larger rail, but then you need an adapter on the small rail if you want to attach it directly to the camera.
That's all assumption based on what I have.


THANK-YOU! I followed your instructions on moving the slide in the bottom layer all the way to one side,and then a hole did indeed line up with the 3/8" threaded bolt.In addition,that position also exposes the fact that the threaded bolt actually does have a recessed hex in it,that an 8mm hex-head wrench fits right into. That allowed me to tighten the bolt to secure the bottom layer to the top layer.

There is also a registration ridge of some sort in the sandwich somewhere,because when the bolt is tightened, the two layers are firmly registered to each other at exactly 90 degrees, so you have a true x-axis and y-axis separated by precisely 90 degrees.

The use of a 3/8"bolt with 8mm hex head,and the use of Magnesium metal for the two layers,also ensures that even by just tightening the bolt correctly- NOT over-torquing it - there is zero movement or deflection between the 2 layers.

The huge hex-shaped hollow "knob" you see on the underside of the top layer (right near "Made in Taiwan:) ) has at its other end (on TOP of the top layer) a standard 1/4"diameter threaded bolt that threads into the tripod hole in the base of the camera. Again,the use of this large diameter "knob",to which you cannot by design apply a tool, ensures that the slider is fastened securely- but not over-torqued - to the camera body.

This is a very slick design.

Too bad the previous owner lost any instructions that might have come with it.I was going nuts trying to figure it out.

Here's the punchlione: the previous owner never did figure it out,and never posted on a forum like I just did, so HE USED THE SLIDER WITH ONLY THE TOP LAYER! HE NEVER USED THE BOTTOM LAYER, SO COULD MOVE THE CAMERA ONLY TOWARDS OR AWAY FROM THE SUBJECT! He told me "I didn't need the sideways motion". Smile

I suspect he sold it to me at a low price because he really did want that sideways motion but never could figure out how to get it.Smile

Now I just need a Manfrotto quick detach plate,like the one already on the camera, to allow using the slider with my existing Manfrotto tripod and head

Jim G
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enricosavazzi



Joined: 21 Nov 2009
Posts: 1229
Location: Borgholm, Sweden

PostPosted: Thu Oct 26, 2017 10:39 pm    Post subject: Reply with quote

Judging from the pictures, it looks like the plastic bushings of the rails of the upper slider are loose, as well as the bolts attaching the rails of the lower slider to the frame. The end of one of these rails seems to have tool marks. Possibly both sliders have been disassembled in the past (or at least the lower one), and not tightened afterward.

I had one of these double rails in the past, and of all the cheaper rails I tried, this model was the one with the least wobble, play, or sag. Rotating the knobs was a bit hard, probably by design. Mine was new from the store, and it came with an Allen key for the connecting bolt. I don't remember if it had instructions, but probably there was a leaflet, or an assembly drawing on the box.
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JimGnitecki



Joined: 12 Sep 2017
Posts: 28

PostPosted: Thu Oct 26, 2017 11:00 pm    Post subject: Reply with quote

enricosavazzi wrote:
Judging from the pictures, it looks like the plastic bushings of the rails of the upper slider are loose, as well as the bolts attaching the rails of the lower slider to the frame. The end of one of these rails seems to have tool marks. Possibly both sliders have been disassembled in the past (or at least the lower one), and not tightened afterward.

I had one of these double rails in the past, and of all the cheaper rails I tried, this model was the one with the least wobble, play, or sag. Rotating the knobs was a bit hard, probably by design. Mine was new from the store, and it came with an Allen key for the connecting bolt. I don't remember if it had instructions, but probably there was a leaflet, or an assembly drawing on the box.


Enrico: Thank-you for your alertness! I did in fact discover this looseness in the 2 bolts attaching the rails to the frame.They require a special tool with 2 pins that engage 2 holes in the end of the bolt,to tighten them. Not having that tool, I was able to use the 2 ends of a miniature pair of model car building pliers to engage the 2holes to tighten the bolts! The previous owner had apparently tried to instead turn the bolts via friction on the bolt peripheries,which is what damaged the finish.

I also just now adjusted the bushings which you noticed,even in my tiny photos, were loose!

The action of this slider is indeed reasonably good. Like other users, I do wish there was some form of "measuring scale" on the frame to facilitate making fraction-of-a-millimeter focus adjustments when doing focus stacking1 Smile

By the way Enrico,I was recently able to take a 2 hour peek at a copy of your book (Digital photography for science Close-up photography, macrophotography and photomacrography by Enrico Savazzi).It is easily the BEST book on photography, let alone scientific photography, that I have yet found! Anyone on the forum who has not seen it has missed a real gem. It covers and explains EVERYTHING and does it extremely well. I think I will buy a copy asap despite the textbook pricing(necessary because it's print-on-demand because of the specialized market). It looks REALLY good.

Jim G
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ChrisR
Site Admin


Joined: 14 Mar 2009
Posts: 8496
Location: Near London, UK

PostPosted: Fri Oct 27, 2017 3:57 pm    Post subject: Reply with quote

I expect you've noticed the finer control on the shorter rail. That makes it better for closer stacking, which is one reason why they can get taken apart.Smile
They're OK, but I never liked the knobs.
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JimGnitecki



Joined: 12 Sep 2017
Posts: 28

PostPosted: Fri Oct 27, 2017 6:03 pm    Post subject: Reply with quote

ChrisR wrote:
I expect you've noticed the finer control on the shorter rail. That makes it better for closer stacking, which is one reason why they can get taken apart.Smile
They're OK, but I never liked the knobs.


I have not yet done any movement measurements, so had not detected the difference in the pitch of the movement screws! Thanks for alerting me.

I got no instruction sheet,and don't know where to get one, so all this is new to me! I read somewhere in an online forum that the larger diameter "outer" knob on each platform layer is for coarse adjustment, and the smaller diameter knob inside the larger knob is for finer adjustments. is this true?

I also wonder if the knobs can be marked with degrees, or changed to marked wheels, to make more precise movements possible.

Jim G
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