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Wood Tripods

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#26 herrointment

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Posted 12 November 2013 - 05:06 PM

"I wanna see some more. I too like wood. I want to see some details of the attachment points, pivots, and mechanisms for height adjustment."
Here's a LINK to a tripod build I did a few months ago.

#27 don clement

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Posted 12 November 2013 - 05:22 PM

So, what scope do you have mounted on your Houston-Fearless?
Jon


I have had a C14 and an 8" F/10 Max Bray Mak-Cass mounted on an equatorial mount I made that sits on the Houston-Fearless tripod.

Don
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#28 brianb11213

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Posted 12 November 2013 - 05:36 PM

My own experience suggests that a wood tripod is a real improvement over an undersized metal tripod but that a rock solid metal tripod is best, vibrations don't have a chance to begin.

Possibly - but a "rock solid" metal tripod is going to be several times the weight of a well designed, well made wooden tripod with the same vibration resistance. The point here is that metal tends to "ring", composite materials like wood damp vibrations far more effectively and grained composites (wood) are at least as stiff as metal of the same cross section when the force is directed along the grain. Most woods float in water, few solid metals do.

#29 SteveG

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Posted 12 November 2013 - 06:12 PM

You'll notice the surveyors tripods, the Houston Fearless, and the renowned Rob Miller tripods all share something in common......

#30 Jon Isaacs

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Posted 12 November 2013 - 08:02 PM

Possibly - but a "rock solid"metal tripod is going to be several times the weight of a well designed, well made wooden tripod with the same vibration resistance. The point here is that metal tends to "ring", composite materials like wood damp vibrations far more effectively and grained composites (wood) are at least as stiffasmetal of the same cross section when the force is directed along the grain. Most woods float in water, few solid metalsdo.



I have to disagree... One rarely sees a serious AP rig on a wood tripod and AP is far more sensitive to vibration and flex than visual. The point of a metal tripod is stiffness.. did you ever try to ring a metal tripod? They don't ring very well...

As far as density, metal tripods are not built from solid steel or aluminum, they are carefully designed structures. Ever see a wooden bicycle... They are not light...

Jon

#31 roscoe

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Posted 12 November 2013 - 10:59 PM

I suspect the reason one seldom sees a serious AP rig on a wood tripod is that they are hard to find.

As for a metal tripod ringing, think of wind chimes.....or baseball bats. Metal tubes ring quite nicely..... and indeed hollow wood tubes ring much more than solid wood (though it tends to be more of a clunk than a ring)

I believe the major reason that tripods come with metal legs nowadays is that metal is fast and easy for a manufacturer - order, cut to length, install end fittings, put in box.

Wood also needs to be cut to size, but then needs a few coats of finish, it's more fragile - it can be dented - and it can warp or twist if not carefully selected. That's not the preferred high profit, low hassle manufacturing model.
R

#32 StarStuff1

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Posted 12 November 2013 - 11:01 PM

Here is an extra tall tripod made from off the shelf red oak from a big box store for a fellow club member. It turned out well.

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#33 don clement

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Posted 12 November 2013 - 11:30 PM

Possibly - but a "rock solid"metal tripod is going to be several times the weight of a well designed, well made wooden tripod with the same vibration resistance. The point here is that metal tends to "ring", composite materials like wood damp vibrations far more effectively and grained composites (wood) are at least as stiffasmetal of the same cross section when the force is directed along the grain. Most woods float in water, few solid metalsdo.



I have to disagree... One rarely sees a serious AP rig on a wood tripod and AP is far more sensitive to vibration and flex than visual. The point of a metal tripod is stiffness.. did you ever try to ring a metal tripod? They don't ring very well...

As far as density, metal tripods are not built from solid steel or aluminum, they are carefully designed structures. Ever see a wooden bicycle... They are not light...

Jon


I agree. Metal tripods can be built as rigid and light as any wood. I built a six element all metal tripod that is every bit as rigid and "rock solid" as my Houston Fearless but weighs only 10 lbs. At present I use this tripod for AP with a 5” F/10 Mak-Cass and can even lean on it with no noticeable vibrations viewing with an eyepiece. Each of the six tripod elements is made with a tapered closed metal tube. Each element is connected to the tripod triangular body using spherical rod ends. The whole tripod is preloaded against the metal cylinder using multi strand SS aircraft cable from leg to leg : not to a center rod. Wood is not needed for dampening because the whole tripod is very stiff and rigid and there are less vibrations to begin with. Also because of the high stiffness of this tripod the natural frequency is high and vibrations dampen out quickly negating the need for high dampening material like wood. No ringing with this metal tripod ;-)

Don

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#34 brianb11213

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Posted 13 November 2013 - 04:05 AM

I believe the major reason that tripods come with metal legs nowadays is that metal is fast and easy for a manufacturer - order, cut to length, install end fittings, put in box.

Wood also needs to be cut to size, but then needs a few coats of finish, it's more fragile - it can be dented - and it can warp or twist if not carefully selected. That's not the preferred high profit, low hassle manufacturing model.
R

Indeed.

As for "serious" AP rigs ... there may be a good reason for preferring metal here. Weight is not much of a concern as the thing doesn't need to be moved. Metal doesn't warp with humidity changes, wood does, and the warpage (though not affecting the strength, stability or vibration resistance properties) may well result in the polar axis alignment needing to be continually readjusted.

Wood is also a near ideal material for tubes for longer focus Newtonians, but not for shorter ones because of very high sensitivity to collimation errors inherent in the optical design.

#35 don clement

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Posted 13 November 2013 - 10:36 AM

As for "serious" AP rigs ... there may be a good reason for preferring metal here. Weight is not much of a concern as the thing doesn't need to be moved.


If a "serious" AP rig doesn't need to be moved then there is no need for a tripod. While observing on the Mt Wilson 60" a couple of weeks ago I actually put my feet and weight onto the OTA to stabilize myself while peering through the eyepiece with no resulting vibrations or image shift. But then that was a "serious" AP rig weighing a mere 22 tons. BTW I understand Hubble had to cajole the 60" with his body weight when doing "serious" AP. For the transit of Venus in 2012 a rare event for June up here in the San Bernardino mountains occurred: it was clouded out. I had to drive down to the desert for clear skies and stopped just in time for the transit at the parking lot of the Yucca Valley California Welcome Center. I set up my "not so serious" AP rig with 10lb tripod (BUMP) and got a few shots of the transit. Sometimes weight and portability do count when doing AP. That's where a lightweight, stiff, and vibration free tripod comes into play.

Don

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#36 Jon Isaacs

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Posted 13 November 2013 - 01:42 PM

As for "serious" AP rigs ... there may be a good reason for preferring metal here. Weight is not much of a concern as the thing doesn't need to be moved.



Again, look around at your typical wooden bicycle... it's not a lightweight in comparison to a steel or aluminum bicycle. Proper structural design allows a metal tripod to be very stiff, look at those 2 inch SS legs on the Celestron tripods. Equal weight in wood will not be anywhere near as stiff.

The reason that the Vixen legs and the Hands on Optics legs provide an improvement for some tripods is that they are replacing some undersized and not very well designed extruded aluminum legs that have a variety of issues... But take that same tripod and add some 1.75 inch or 2 inch diameter Stainless legs and it will represent another step up in freedom from vibration.

Another example of solid metal tripods, professional photographic tripods...

Jon

#37 don clement

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Posted 13 November 2013 - 02:43 PM

replacing some undersized and not very well designed extruded aluminum legs that have a variety of issues...
Jon


One of those issues is the open structure of the extruded aluminum legs. Just replacing the open structure with a closed tube of equal diameter and thickness increases the stiffness many fold. For example a steel tube of any specific length, with 1" O.D. and wall thickness of 0.065" is 156 times stiffer than an identical tube with a slit running its entire length.

Don

#38 brianb11213

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Posted 13 November 2013 - 07:39 PM

Proper structural design allows a metal tripod to be very stiff, look at those 2 inch SS legs on the Celestron tripods. Equal weight in wood will not be anywhere near as stiff.

Sorry guys but 2 inch tubular SS legs (not extended) under a HEQ5 mount supporting a FLT 110 = loads of vibration and an unacceptable damping time (over 1 sec). Throw away the legs & substitute Berlebach Planet, far less vibration & damping time under 1/4 sec. True the Planet leg set is about twice as heavy, but a light wobbly tripod is far less use than a heavy reasonably stable one.

I h8 tubular stainless legs ... they bend and they ring. IMHO the main reason the commonly supplied rectangular section alu alloy legs are even worse is that the accessory tray fails to add any bracing.

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#39 don clement

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Posted 13 November 2013 - 08:34 PM

IMHO the main reason the commonly supplied rectangular section alu alloy legs are even worse is that the accessory tray fails to add any bracing.



Of course the accessory tray fails to add any bracing. Follow the lines of force in a tripod and the best way to brace is from leg to leg at the extremities. Not though a center rod either. Three element tripods also are lacking despite large diameter elements. That's where the six element tripod is way more rigid. Again follow the lines of force a look at designs such as the six element that use the least bending forces on each element and maximize elements in tension and compression. Bending moments can cause vibration and then dampening materials are needed e.g. wood. IMO the six element tripod design is the best
with cables running from the extremities of each leg to leg- not through a central rod or accessory tray.

Don

#40 George9

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Posted 13 November 2013 - 08:55 PM

Of course the accessory tray fails to add any bracing. Follow the lines of force in a tripod and the best way to brace is from leg to leg at the extremities. Not though a center rod either. Three element tripods also are lacking despite large diameter elements. That's where the six element tripod is way more rigid. Again follow the lines of force a look at designs such as the six element that use the least bending forces on each element and maximize elements in tension and compression. Bending moments can cause vibration and then dampening materials are needed e.g. wood. IMO the six element tripod design is the best
with cables running from the extremities of each leg to leg- not through a central rod or accessory tray.

Don


Along the same lines, I find that the best stability is gotten by sinking the tips of the legs into the grass rather than relying on a cable. My AP/Baader tripod is perfectly rigid when sunk into the ground. Then you effectively have six triangles holding it rigid. The accessory tray is irrelevant to stability. Even the aftermarket braces don't add much because their attachment point on the tripod leg is not that stable. The only thing I added was a cord between pairs of legs just so it was easier to line up the accessory tray attachments. And rubber feet for when I store it in the house (I see that's now an option).

George

#41 OneDaveT

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Posted 13 November 2013 - 11:05 PM

Here's my AstroTech voyager head on an Oberwerk tripod


http://www.cloudynig...?Number=5078547

#42 Jon Isaacs

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Posted 14 November 2013 - 05:36 AM

Throw away the legs & substitute Berlebach Planet, far less vibration & damping time under 1/4 sec.



Put that on the Houston-Fearless and there would be no damping time, no vibration.. And the Houston-Fearless is actually lighter.

It's also worth noting that the Berlebach upgrade was more than just the tripod legs, it was also the tripod hub (wood right?) The hub itself is much larger in diameter, this provides much greater rotational stiffness. The reduced damping times might not be due so much to the legs but rather to the improved hub design.

Jon

#43 hottr6

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Posted 14 November 2013 - 11:25 AM

You'll notice the surveyors tripods, the Houston Fearless, and the renowned Rob Miller tripods all share something in common......

Um..... 3 legs? A triangular head? They keep things out of the dewy grass?

:question:

#44 Old Dinosaur

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Posted 14 November 2013 - 11:31 AM

I guess I like them all.
5 wood.
5 metal.

#45 roscoe

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Posted 14 November 2013 - 12:01 PM

They keep things out of the dewy grass?


Yep, your knees............ :jump:

#46 SteveG

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Posted 14 November 2013 - 12:22 PM

You'll notice the surveyors tripods, the Houston Fearless, and the renowned Rob Miller tripods all share something in common......

Um..... 3 legs? A triangular head? They keep things out of the dewy grass?

:question:


I believe Jon answered with the technical term "six element tripod design". Note the very wide stance where the legs attach to the hub.

#47 JonNPR

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Posted 14 November 2013 - 01:35 PM

Dave, did you need any special adapter work in order to mount the head on the Oberwerk?

Jon

#48 hottr6

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Posted 14 November 2013 - 02:28 PM

You'll notice the surveyors tripods, the Houston Fearless, and the renowned Rob Miller tripods all share something in common......

Um..... 3 legs? A triangular head? They keep things out of the dewy grass?

:question:


I believe Jon answered with the technical term "six element tripod design". Note the very wide stance where the legs attach to the hub.


Gottit, but I would argue that many tripod designs have "6 elements" (actually, it is really 9). The awful tubular legs have only 3.

Perhaps a key feature of the more expensive designs (except surveyor's tripods) is the triangular nature of each leg, like a crutch. As you noted, the components of each leg are wide apart at the hub, but the components come together at the feet.

#49 don clement

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Posted 14 November 2013 - 03:46 PM

Of course the accessory tray fails to add any bracing. Follow the lines of force in a tripod and the best way to brace is from leg to leg at the extremities. Not though a center rod either. Three element tripods also are lacking despite large diameter elements. That's where the six element tripod is way more rigid. Again follow the lines of force a look at designs such as the six element that use the least bending forces on each element and maximize elements in tension and compression. Bending moments can cause vibration and then dampening materials are needed e.g. wood. IMO the six element tripod design is the best
with cables running from the extremities of each leg to leg- not through a central rod or accessory tray.

Don


Along the same lines, I find that the best stability is gotten by sinking the tips of the legs into the grass rather than relying on a cable. My AP/Baader tripod is perfectly rigid when sunk into the ground. Then you effectively have six triangles holding it rigid. The accessory tray is irrelevant to stability. Even the aftermarket braces don't add much because their attachment point on the tripod leg is not that stable. The only thing I added was a cord between pairs of legs just so it was easier to line up the accessory tray attachments. And rubber feet for when I store it in the house (I see that's now an option).

George


I use my six element tripod on asphalt sometimes so digging into grass is not always an option. The aircraft cables that are connected leg to leg on the six element tripod I built don't just attach but there is a tensioning that preloads each leg ( made of two elements ) to a center bolt that bears on the upper ring. This preload also takes up any play in the spherical rod connections and makes for an almost solid feel with no measurable vibration issues and therefor no need for additional dampening. In fact this 10lb tripod is as stiff and rigid as any tripod of similar dimensions and in fact is more rigid than my Houston-Fearless when the legs on the Houston-Fearless are extended any amount at all. The leg extension basically defeats the six element design of the Houston-Fearless and adds three lengths of unsupported cantilever tubing. Note there is no wood used in my six element tripod because there is no need for dampening the structure being very sound from the start. IMO the addition of dampening is an afterthought or band aid fix to poor tripod design methods.

Don

#50 George9

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Posted 16 November 2013 - 12:31 PM

I get it now. The tensioning should work well. George






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