9
Making a Sturdy Wood Tripod
Dec 20 2005 03:44 AM |
matt
in How to . . .
Discuss this article in our forums
Making a Sturdy Wood tripod out of a (flimsy / cheap / shaky) aluminium tripod.
I tried to make this article as comprehensive as possible, for the newbiest of beginners I could think of, so I made it out into paragraphs so you can figure out which parts you need to read and which you can skip. Most of the time I used metric measurements; remember that 25mm ~ 1”, and that anyway most measures I gave were for indicative purposes – you will adapt your dimensions to your particular needs.
Introduction
I’ve been an astronomer all my life. I’ve been a member of the CN forums for a couple years, and seemingly every week, veteran observers and beginners alike come in and complain about how shaky their scope’s mount is. Very often, it boils down to how flimsy the tripod is. The tripod is simply not the priority for most buyers. After all, as a teenager, I was dreaming of owning a C11 or C14 to knock the daylights out of my dad’s C8. I was never dreaming of a solid oak tripod with 3” cross section beams.
Solutions include: changing your tripod and/or mount altogether, as well as filling tripods with sand or concrete, hanging milk jugs under the tripod (like there is not enough stuff dangling around telescopes and our spouses are not making enough fun of us yet), and avoiding magnifications above 20x.
My favourite solution consists in a “makeover” of your existing tripod, by replacing the lightweight legs with beefier wooden ones, and adding stiffness by suppressing the moving parts of a standard tripod. The only part of the old tripod we are keeping is the tripod hub, because it’s rarely to blame, and it would be quite difficult to manufacture a new one (at least with my skills!). I make (the pictures in this article are from my third tripod) legs with an “H” pattern, because they offer optimum rigidity, just like the steel beams used in construction.
Design
There are two critical numbers you need to know when building your tripod:
- the width of the hub’s lug (w1 in my figures), which is the protruding part of the hub where the leg mates to the hub.
- the height of the tripod.
The first one is easy: you take a ruler, or ideally a calliper, and measure. This is important because it will determine the width of the centre furring strip of your legs (w1 in figure1), the one which is the “-“ in the “H”. It is important for this to be tight. If the lug is 36mm wide, and you have the choice between a 35mm wide plank and a 37mm wide one, take the 35mm. I’ll explain later why.
In my case it was 39mm; I took some 39x30 (w1 x t1) oak for the centre strip (the 30, t1, is not critical; you just want something narrower than 39mm, and wide enough to drive a screw through it (in the pictures the centre strip is awkward looking because I glued together three strips to get the proper width).
Then I found some 40x25 (w2 x t2) mm oak for the “|” of the “H”: again, precise measurement is not paramount; it just needs to be “wider” than the centre strip. The wider the strip, the stiffer the tripod.
Height of the tripod
Guys who have owned 22 scopes and 15 mounts can skip this one.
Not only can you make a good tripod, you can make a tripod which is good for you. This section is a little long, but with all the work you are going through, you might as well have it the right size.
Step 1: determine the height variation in eyepiece position with your current tripod.
Step 1.1.: point the telescope at the zenith; measure height of the eyepiece (say, 700mm)
Step 1.2.: point the telescope at the horizon, or as close to the horizon as you are likely to observe (either because of obstructions or because you know you never observe stuff close to the horizon), maybe 15° altitude (say, 1200mm)
Conclusion: the variation in height is 500mm in our case.
Step 2: determine your optimal observing height (assuming you use a chair)
Step 2.1: sit on your chair at its lowest setting, sit in a slightly crouched position (the position at which your eye is lowest, without causing discomfort) (ok, say, 900mm – 36”)
Step 2.2: sit on your chair at its highest setting, making yourself as tall as you can without causing discomfort (say, 1300mm).
So your eye’s variation in height is only 400mm, while the eyepiece can move 500mm (20”). You make up your mind on where you compromise. Let’s say we decide we want the lowest eye position to be 900mm (36”): we obviously need to make your eyepiece 200mm (8”) taller than your current one.
Step3: measure the height (not the legs’ length!) of your current tripod.
Let’s assume it is 1100mm: you need an 1300mm (52”) tall tripod (this succession of steps might seem a little dumb, but it’s easier than measuring the variation of your mount, especially if it’s a GEM. This procedure at least is fool-proof).
Step4: determining the angle of the tripod legs
I don’t have a secret recipe here. The angle is important (it’s a look-and-feel thing too: if afterwards you are always afraid to topple the mount over because the base is too narrow, or to hit a leg all the time because it is too wide, you will hate your tripod, and me in the process), the width of the base too (in my case, I use a Giro alt-az mount, so the centre of gravity is not above the centre of the tripod, so I need the base to be wide). For mechanical purposes, the stiffest angle is that at which your tripod and the ground make a “perfect” tetrahedron, so that makes the max angle. In practice that angle is quite, well, impractical because your legs will be all over the place.
You can “practice” with your current tripod to see what kind of angle you want, and measure the height vs. leg length ratio.
In our practice case, that means 1500mm legs (5’).
Now you can be a little creative. You make yourself a chart such as this one, to determine the shape you want to give.
The centre beam is in two parts; the upper one can be pretty short, it’s just for rigidity. The lower part can be made to be adjustable, with three screw-holes, meaning you can get it higher, for the day you purchase that f/15 refractor or want to observe standing. You also want the side beams, which bring most of the stiffness, to go quite low. Then you can be a little cheap and adjust the lengths depending on the lengths of the beams available at your hardware store. Hardwood is expensive, and you will have a hard time finding use for the leftover parts, so don’t be too proud to be a little scroogy. My experience shows that the bottom of the leg, as it’s a single piece of wood, is the part giving most of the instability to the system, so it’s best to keep the extending part short.
My recommendation is to use a vise or grips to hold the parts together and drill the “assembled” leg. Why? You are not a professional, so you are not likely to drive those holes perfectly straight, and having those holes unaligned is going to be a problem when you want to drive your screws – especially if you use hardwood, because the screw will have a hard time “nudging” its way down.
In my case my grips were not wide enough to drill all three beams at once, so I did them two by two.
The important tip here is: whatever you do, keep the tops (the part where it will mate with the tripod’s hub) perfectly aligned. This is where you have zero tolerance.
Don’t forget to drill holes for the bolts holding the tripod to its hub! By the way, you will probably need longer bolts than those of your current legs. Keep the old bolts to hold your old legs together. Drill those holes with your two side beams pressed against one another, and again with the tops aligned. Experience shows that if you have to “force” the bolts when you mate the legs to the tripod, you will have vibrations, and if the holes are too loose, you will lose stiffness and the legs and hub will wiggle.
Here it’s all the more difficult to make a straight hole because you need to bore a wide one (on mine: 8mm). Make a hole with a narrower drill (4mm), which will be easier to drill precisely, and use it as a guide for the large hole.
The accessory tray
Notice I had not discussed this part yet. My belief is that it’s better to decide where to place it once you have your tripod assembled: you have a better feel of what your tripod looks like (especially if the height and leg angle are very different from the original tripod), and where you want the tray to be. It’s also your last chance to adjust the angle of the legs.
Once this is done, you can tighten back all your screws, glue and varnish. I say glue but I actually never did that: I thought the legs were stiff enough, gluing would not add much and you can’t adjust your tripod later. Do it only if you are 100% sure you are never going to change a thing.
Woodworking tips coming from non-carpenters who learned them the hard way:
|
Executive summary: Benefits: - improved viewing stability - custom viewing height - strokes your ego into believing you can actually do something useful, and even quite pretty, yourself. Budget: circa 100 Euros (120$) depending on materials (softwood or hardwood), and s**** materials you might have. Workforce: 1 person Workload: 1 man-days Logistics: 1 trip to the hardware store Skills required: if you have both a left AND a right thumb, you qualify Reversible operation: YES. |
|
I tried to make this article as comprehensive as possible, for the newbiest of beginners I could think of, so I made it out into paragraphs so you can figure out which parts you need to read and which you can skip. Most of the time I used metric measurements; remember that 25mm ~ 1”, and that anyway most measures I gave were for indicative purposes – you will adapt your dimensions to your particular needs.
Introduction
I’ve been an astronomer all my life. I’ve been a member of the CN forums for a couple years, and seemingly every week, veteran observers and beginners alike come in and complain about how shaky their scope’s mount is. Very often, it boils down to how flimsy the tripod is. The tripod is simply not the priority for most buyers. After all, as a teenager, I was dreaming of owning a C11 or C14 to knock the daylights out of my dad’s C8. I was never dreaming of a solid oak tripod with 3” cross section beams.
Solutions include: changing your tripod and/or mount altogether, as well as filling tripods with sand or concrete, hanging milk jugs under the tripod (like there is not enough stuff dangling around telescopes and our spouses are not making enough fun of us yet), and avoiding magnifications above 20x.
My favourite solution consists in a “makeover” of your existing tripod, by replacing the lightweight legs with beefier wooden ones, and adding stiffness by suppressing the moving parts of a standard tripod. The only part of the old tripod we are keeping is the tripod hub, because it’s rarely to blame, and it would be quite difficult to manufacture a new one (at least with my skills!). I make (the pictures in this article are from my third tripod) legs with an “H” pattern, because they offer optimum rigidity, just like the steel beams used in construction.
Design
There are two critical numbers you need to know when building your tripod:
- the width of the hub’s lug (w1 in my figures), which is the protruding part of the hub where the leg mates to the hub.
- the height of the tripod.
The first one is easy: you take a ruler, or ideally a calliper, and measure. This is important because it will determine the width of the centre furring strip of your legs (w1 in figure1), the one which is the “-“ in the “H”. It is important for this to be tight. If the lug is 36mm wide, and you have the choice between a 35mm wide plank and a 37mm wide one, take the 35mm. I’ll explain later why.
In my case it was 39mm; I took some 39x30 (w1 x t1) oak for the centre strip (the 30, t1, is not critical; you just want something narrower than 39mm, and wide enough to drive a screw through it (in the pictures the centre strip is awkward looking because I glued together three strips to get the proper width).
Then I found some 40x25 (w2 x t2) mm oak for the “|” of the “H”: again, precise measurement is not paramount; it just needs to be “wider” than the centre strip. The wider the strip, the stiffer the tripod.
Height of the tripod
Guys who have owned 22 scopes and 15 mounts can skip this one.
Not only can you make a good tripod, you can make a tripod which is good for you. This section is a little long, but with all the work you are going through, you might as well have it the right size.
Step 1: determine the height variation in eyepiece position with your current tripod.
Step 1.1.: point the telescope at the zenith; measure height of the eyepiece (say, 700mm)
Step 1.2.: point the telescope at the horizon, or as close to the horizon as you are likely to observe (either because of obstructions or because you know you never observe stuff close to the horizon), maybe 15° altitude (say, 1200mm)
Conclusion: the variation in height is 500mm in our case.
Step 2: determine your optimal observing height (assuming you use a chair)
Step 2.1: sit on your chair at its lowest setting, sit in a slightly crouched position (the position at which your eye is lowest, without causing discomfort) (ok, say, 900mm – 36”)
Step 2.2: sit on your chair at its highest setting, making yourself as tall as you can without causing discomfort (say, 1300mm).
So your eye’s variation in height is only 400mm, while the eyepiece can move 500mm (20”). You make up your mind on where you compromise. Let’s say we decide we want the lowest eye position to be 900mm (36”): we obviously need to make your eyepiece 200mm (8”) taller than your current one.
Step3: measure the height (not the legs’ length!) of your current tripod.
Let’s assume it is 1100mm: you need an 1300mm (52”) tall tripod (this succession of steps might seem a little dumb, but it’s easier than measuring the variation of your mount, especially if it’s a GEM. This procedure at least is fool-proof).
Step4: determining the angle of the tripod legs
I don’t have a secret recipe here. The angle is important (it’s a look-and-feel thing too: if afterwards you are always afraid to topple the mount over because the base is too narrow, or to hit a leg all the time because it is too wide, you will hate your tripod, and me in the process), the width of the base too (in my case, I use a Giro alt-az mount, so the centre of gravity is not above the centre of the tripod, so I need the base to be wide). For mechanical purposes, the stiffest angle is that at which your tripod and the ground make a “perfect” tetrahedron, so that makes the max angle. In practice that angle is quite, well, impractical because your legs will be all over the place.
You can “practice” with your current tripod to see what kind of angle you want, and measure the height vs. leg length ratio.
In our practice case, that means 1500mm legs (5’).
Now you can be a little creative. You make yourself a chart such as this one, to determine the shape you want to give.
The centre beam is in two parts; the upper one can be pretty short, it’s just for rigidity. The lower part can be made to be adjustable, with three screw-holes, meaning you can get it higher, for the day you purchase that f/15 refractor or want to observe standing. You also want the side beams, which bring most of the stiffness, to go quite low. Then you can be a little cheap and adjust the lengths depending on the lengths of the beams available at your hardware store. Hardwood is expensive, and you will have a hard time finding use for the leftover parts, so don’t be too proud to be a little scroogy. My experience shows that the bottom of the leg, as it’s a single piece of wood, is the part giving most of the instability to the system, so it’s best to keep the extending part short.
|
Now is the time to cut your wood – no comment to add here. Then, choose which beams you are going to mate together to make the legs. This step is quite important as beams you purchase are seldom very straight. So see which parts fit best together. Then you mark where you are going to make your holes. |
My recommendation is to use a vise or grips to hold the parts together and drill the “assembled” leg. Why? You are not a professional, so you are not likely to drive those holes perfectly straight, and having those holes unaligned is going to be a problem when you want to drive your screws – especially if you use hardwood, because the screw will have a hard time “nudging” its way down.
In my case my grips were not wide enough to drill all three beams at once, so I did them two by two.
|
The little tricks here to make your tripod look handsome are: - on the “top” side beam (remember, the “|” of our “H”), make a little hole slightly wider to accommodate the head of the screw (otherwise, you will either have the head of the screw protruding, or have to squash the wood to also drive the head in the beam). |
|
|
- Adjust the drill’s length to avoid drilling the “low” side beam all the way. This way you will not have an “empty” hole. |
|
The important tip here is: whatever you do, keep the tops (the part where it will mate with the tripod’s hub) perfectly aligned. This is where you have zero tolerance.
Don’t forget to drill holes for the bolts holding the tripod to its hub! By the way, you will probably need longer bolts than those of your current legs. Keep the old bolts to hold your old legs together. Drill those holes with your two side beams pressed against one another, and again with the tops aligned. Experience shows that if you have to “force” the bolts when you mate the legs to the tripod, you will have vibrations, and if the holes are too loose, you will lose stiffness and the legs and hub will wiggle.
Here it’s all the more difficult to make a straight hole because you need to bore a wide one (on mine: 8mm). Make a hole with a narrower drill (4mm), which will be easier to drill precisely, and use it as a guide for the large hole.
|
Check out to see if you need to round off the top of the legs so they can fit near the hub. The easiest being to chip off the corner with a saw, then rounding it with a file. Check also how tight the legs mate to the hub’s feet. Ideally, it will be the right size and tightening the bolt will make it rock solid. Otherwise you can sand off a little of the “ | “s. It’s better to have to do that than to have the foot wiggling (you can try to fix that with washers or something, but in my case it proved quite un-efficient, and allowed for sideways movement of the tripod when I moved the scope sideways. |
|
First look You can now screw your legs together (don’t glue yet, and screw the “spacers” loosely). Mate them to the tripod. Tighten the screwing of the “spacers” Do the legs one by one. It will avoid mixing the parts, and if you make a dumb mistake, you will notice it after doing it only once, not thrice. Now you have a tripod. Looks neat, huh? It’s probably already stiffer than what you had. But there’s something missing: the spreader. On most tripods, the spreader is just three plastic bars that avoid the tripod from falling apart, it does not have much strength. Here we will make a one-piece, solid spreader, which will not only make our tripod into a stiff tetrahedron, but also serve as an eyepiece tray. |
|
The accessory tray
Notice I had not discussed this part yet. My belief is that it’s better to decide where to place it once you have your tripod assembled: you have a better feel of what your tripod looks like (especially if the height and leg angle are very different from the original tripod), and where you want the tray to be. It’s also your last chance to adjust the angle of the legs.
|
The spreader is obviously the most difficult piece to make. The inside shape does not matter much (it can be a triangle or a circle, as you like it), but the three outside pegs have to be at your best 120° angle. They have to be as close to the width of the “-“ as possible, again for stability’s sake. Then you have to drill the pegs sideways, as well as the legs. Ideally, you would have a second person helping you for a minute here, and you could pierce the peg and leg all at once (which, again, will help you put the bolt in and out- all the more because this will allow you to fold the tripod for storage). There you have two options (figure 2): either you have board thick enough to drill through it, or you have a thin board, and place a thick piece of wood under to drive the bolt through it. |
Once this is done, you can tighten back all your screws, glue and varnish. I say glue but I actually never did that: I thought the legs were stiff enough, gluing would not add much and you can’t adjust your tripod later. Do it only if you are 100% sure you are never going to change a thing.
|
Varnishing is not an emergency, but do it for the looks of your tripod, as well as protecting it against humidity; it also seems that varnish hardens softwood a little, making it less sensitive to little hits that would scratch / dent the wood. You now have a beautiful tripod, which is functional, makes viewing more comfortable for your eyes and spine. And it’s still mid-afternoon on Saturday: you still have time for a nap before observing. Keep your old aluminium tripod legs: they can come in handy when you go see that Eclipse in |
|
Required parts
|
Required tools Power drill with wood drill bits (duh) Handsaw or electric saw Wood files Philips screwdriver Tape measure Ruler or calliper Vice or clamps Gloves, earplugs, glasses |
Woodworking tips coming from non-carpenters who learned them the hard way:
- Watch out not to take on face value the dimensions of the wood you buy. If you buy a 2000mm plank and cut a 400mm piece, don’t expect the last part to be exactly 1600mm. It might well be 1595 or 1610. Same for the width: often, the dimensions are taken before the beam is sanded. So that 35mm cross section beam might turn out to be 33.5. Take your ruler with you to the store.
- If you have a 5mm screw, make your hole with the 4mm drill, not the 5mm. Otherwise the screw might not be tight in the wood.
- When you drill a piece of wood, keep a s**** piece of wood pressed under the drill part. It will avoid the wood on the backside to “explode” when the drill reaches the other side.
- Put those gloves on. It might just protect you from benign hurts, but benign wounds to your hands can get pretty irritating because they will get in the way of whatever you do, and take weeks to heal completely.
- Put those glasses on. You can have a tiny shard of wood flying into your eye, it will feel like a telephone pole. Last week I was taking some staples off a wooden case with pliers, and one staple “bounced” off and scratched my eyelid. I don’t want to know what would have happened if it had been half an inch off.
- Jon Isaacs, Neptune, sixtysomething and 13 others like this
0 Comments