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Beefing Up Hollow Aluminum Tripod Legs

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20 replies to this topic

#1 CollinofAlabama

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Posted 12 October 2015 - 09:55 AM

If you’re mount setup seems a bit too wobbly in the wind, well this West Texan might have the answer. This will not make a woefully inadequate mount suddenly fine, but it should help someone whose mount is almost capable enough, but not quite.

 

People write on CN that this is self-evident, and after reading this article you may agree, but I like pointing out the obvious. Hope someone finds it edifying.

Click here to view the article



#2 Greg-O

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Posted 12 October 2015 - 11:09 AM

Thank you for posting your article. While this may indeed be "self-evident" to many of us, we must never forget where we started from. My own experiences date from the pre-internet days starting with a cardboard tube 3.5-inch Newtonian reflector on a plastic alt-az head and three wobbly pressed steel legs for a tripod. I would have loved to have had some advice on what I should do next, but there wasn't anything in my area except some Time-Life books on the stars and planets at the school library.

 

There are innumerable kids out there with well-meaning parents who bought them Christmas Trash Telescopes at a big-box store and dashed their imaginations with poor optics (usually the eyepieces were the weakest link) and a poor mount (usually the legs were the weakest link). My niece received one such telescope, a 70mm Celestron alt-az, with awful eyepieces. I gave her some mid-power Plossls and a star diagonal and she has really enjoyed her telescope since then.

 

We must never forget that there are budding astronomers out there of all ages who need some advice from time-to-time and look to websites like Cloudy Nights for help on what to do next.


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#3 DocFinance

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Posted 12 October 2015 - 03:16 PM

Thanks for posting this.  I think most of us KNOW that we need to beef up the weight on the lower end of the tripod, but we usually don't think of ways to do it easily.  This should be helpful for many folks.


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#4 Eduardo Costa

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Posted 12 October 2015 - 03:17 PM

Hi! You can use small marbles and sand to fill the legs, like a Gorilla Pad inflexible. Marbles will be more heavy and better stability. Sand will cushion small displacements.


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#5 CollinofAlabama

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Posted 12 October 2015 - 05:03 PM

Greg-O, you're absolutely right.  That's why I made this post.  I wanted people unfamiliar with mount modification to know that they have it easily within their power to add some heft to their existing mounts.  Like I wrote, it won't make a totally overweight load mount work, but if folks just need a little more umf, this might keep them happy.

 

As for sand, yes, one can use sand, but I don't like the idea of sand leaking out.  I like to make sure there's plenty of pressure against the side supports and top to bottom, to prevent creaking and rattling.  The rebar works VERY well.  It's heavy.  My first effort just used the wooden dowels, and although they help, they are greatly enhanced by the rebar.  Oh well, we live and learn.



#6 Ken Sturrock

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Posted 12 October 2015 - 10:56 PM

Glad this was posted as an article on the front page where it will be easily found.


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#7 Jim Davis

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Posted 13 October 2015 - 10:07 AM

I was thinking of adding some lead weights to the bottom legs of my Vixen Porta II. I have not really had a stability issue with it yet, but I am always afraid of someone bumping into it in the dark and knocking it over.


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#8 Astrojensen

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Posted 13 October 2015 - 03:36 PM

Has anyone tried filling the legs with cement? 

 

A friend of mine replaced the round 50mm thin-walled stainless steel legs of his EQ-6 with 50mm 5mm wall thickness steel pipe! It became monster heavy and monster stable. 

 

 

Clear skies!

Thomas, Denmark



#9 Gregklu

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Posted 13 October 2015 - 09:32 PM

I do not understand your descriptions.  You mention steel rebar and you mention wooden dowels.  Do you use both?  If so why?  You make no mention of stability difference. Is this exercise worthwhile?



#10 CollinofAlabama

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Posted 14 October 2015 - 06:59 PM

Gregklu, uh, I guess you're right.  I did this first with just wooden dowels, and, of course, with wood, you can cut it to the exact size.  With rebar, it comes in set sizes, and, if you're like me, sawing a 3' piece of rebar down to 2'-6" size (or whatever it actually is) is nigh impossible.  The larger, center piece of wood is pretty taxing with a hand saw, and that's as tough as I'd like to tackle.  Now, for folks with a steel press or some other such facilities, this is a piece of cake, but for average joes, getting rebar to the exact right size is simply not possible.  So how does one get the stability of steel rebar?  Well, you use wooden dowels to fill the small difference between the 2' rebar piece (or pieces).  That's why the wooden dowels are important.  They fill the void between the plastic caps and the rebar, which would otherwise smack up against the insides of your tripod leg posts, possibly damaging them, definitely shifting their weight making them dangerous to move.  Plus they'd make quite a clatter.  The upgrade I outline above does not do this.  It makes the legs heavier, sturdier, but not too heavy.  It also doesn't cause unseemly outcomes.  The weight, though heavier, doesn't shift when moved, because the components inside, if done right, do not jiggle about.  They also should cause minimal to NO sound.  And they shouldn't leak.  At least this has been my experience.  Don't skimp on the workmanship.  Do it right and you'll be happy.  I hope my instructions, with all this in mind, results in tripod legs with more heft, but also will not degrade the asthetic of ownership.


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#11 Gregklu

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Posted 14 October 2015 - 07:55 PM

Ahhh!  All is clear now.  Thanks for the update.


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#12 Unknownastron

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Posted 16 October 2015 - 10:59 PM

Rebar is not really hard to cut.  Anything that holds it solid while you cut with a hacksaw will do.  Holding it in a vice is best but if you don't have a vise clamping it to a table with a c-clamp with the part to cut off sticking out over the edge will do.  It takes a bit of effort with the hacksaw but just go slow and steady and no problem.  Power tools make it easier but if you only have a few pieces to cut the hand-powered hacksaw works fine.

I don't mean to criticize as this is a good article and I am sure it did improve the tripod a lot for little money.

Clear skies and clean glass,

Mike



#13 Chaz659

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Posted 20 October 2015 - 07:19 PM

Just thought I would give another option that doesn't require much effort at all.

 

There is another simple option for those flimsy aluminum tripods, especially if it's the wind that's making your set-up "wobbly". It's only drawback is it must be used on ground, not on a paved surface or cement slab.

A simple yard stake, like many people tie their dogs to, secured into the ground directly beneath the mount, centered between the legs. Then take a few bungee chords, or small ratchet straps and secure the whole set-up to the handle of the stake. It not only nearly eliminates the shimmy the wind might cause, but it also makes the scope nearly impossible to knock over.

On a slab or the sidewalk, a 5 gallon bucket half filled with dirt or cement, a cinder block, etc. can replace the yard stake. Bungee chords or small ratchet straps for securing the scope and again, you're good to go.

 

Total cost, maybe $15.00. No muss, no fuss.


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#14 mayidunk

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Posted 21 October 2015 - 01:49 PM

A "quick-'n-dirty" way you might consider to stabilize a lightweight mount is to just hang a weight from the bottom of the mount, within the legs of the tripod.  A plastic milk jug filled with either sand or water can be quite convenient, and allows you to adjust the amount of weight needed so that you don't risk overtaxing the mount.  If the thought of a swinging weight is an issue, just add a length of string from the weight to each of the legs to keep it centered.


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#15 Cathal

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Posted 23 October 2015 - 07:17 PM

It's not necessarily just extra mass that improves the performance of a tripod. For a lot of the tripod improvements, it's the fact that the added material has greatly differing mechanical properties and resonance frequencies and this effectively makes the legs a composite material. Sand absorbs vibration as the grains move along each other dissipating vibrations, and the lack of solidity is why that works so well. Any leakage should be easily resolved!

 

Using dissimilar materials is a good idea. If I was using wooden poles inside the aluminium legs, I would try to get the wood solidly attached to the inside of the legs along as much of the leg as possible, to better utilise the damping properties of the wood.

 

I don't think that using steel rebar is an effective use of added mass from an engineering standpoint. Changing the legs for thicker walls doesn't have as much added benefit as you'd expect, especially when considering the extra mass involved. Better return for the investment with other materials, or making a composite.

 

Adding weight under the centre of the tripod reduces the amount of flexure that the tripod undergoes as well as removing any play that exists between contact points. The lowered centre of gravity does have a small effect. This also changes the resonant frequencies in play.

 

Another very useful way of reducing the "ringing" effect that aluminum legs can suffer from, is to fill the legs with polyurethane expanding foam. Lightweight and excellent at damping vibrations, as well as adhering well to the aluminium along its length. This was my planned improvement to the LXD75 tripod I had, but I sold that mount before putting that into practice.



#16 bluedandelion

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Posted 28 October 2015 - 01:29 PM

Here's an aticle by Gerhard Dangl. There are many mods described for the EQ6, but there is one for leg mods midway. This is similar to what Thomas (Astrojensen) descrbes in his post above. I have done this myself and the tripod is really stable now.

 

http://www.dangl.at/...t/eq6/eq6_e.htm

 

Ajay



#17 Robrj

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Posted 28 October 2015 - 05:49 PM

How about bb gun ammo?  6000 bbs at Walmart for $7.  That's about 5 lbs.  It wouldn't leak out like sand might.  I knew some guys that would put them in the handlebars of their motorcycles to reduce vibration.



#18 mattyfatz

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Posted 01 November 2015 - 07:51 AM

I used bb's. Here is how I got it work.

1- spray a small amount of insulation foam (like great stuff) at the very bottom of the legs, by the feet. Use a piece of surgical tubing to get it all the way in.

2- wrap the bb's in plastic grocery bags with packing tape to seal. It works better if you try and form a long skinny tube shape out of the bag.

3- stuff it in the legs, leaving the top two inches open.

4- spray foam the top to seal it in.

***** the foam will expand out a bit, so wait for it to dry, then cut it flush with a sharp knife.

 

The method described in this article is superior to the bb method though. The wood / rebar combo adds structural integrity, where the bb's only add weight.


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#19 RichA

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Posted 11 November 2015 - 01:38 AM

I sealed and filled the legs of one with sand.  It doesn't stiffen it up much, but it damps vibration.  Only drawback is increased weight.



#20 Howie1

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Posted 16 November 2015 - 03:29 PM

Here's an interesting idea for y'all ... if I had the will, desire and such I'd fill the legs with C or D cell rechargeable batteries in a tight fitting postal cardboard tube. The weight kinda wouldnt matter then you're saving on carrying around separate batteries. And of course, the batteries would power the mount n such. And of course, the weight/batteries would still stabilise the legs. ???!!!???

cheers



#21 Howie1

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Posted 16 November 2015 - 03:30 PM

Oh, and further to my post above, I wouldn't use those rechargeable batteries that heat up n explode n such if I stuffed them in the legs! :)




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