Motorised Binochair design for 100mm binoculars

[Mr H in Yorkshire]

Over the years I have struggled to use my 100mm aperture straight-through binoculars for high altitude targets. On a tripod or even a parallelogram mount high elevation viewing is literally a pain in the neck, but the bulk and 20 x mag really demands some form of support. The solution is an alt-az binochair. The ultimate purpose of a binochair is simple: to enable the observer to comfortably keep their eyes at the eyepiece sweetspot in any chosen part of the sky. I have made (and abandoned) 3 chairs previously but I have gained a clear idea of the problems in the existing body of designs. 

The problems
Body weight redistribution:  A rigid seat has an included angle of 100 degrees or so. When used for high altitude targets, as the seat back approached horizontal, the bodyweight redistribution made me slide upwards and my knees want to meet my face. On a lounger seat with the back lowered enough for zenith viewing, I found I would slide down relative to the binoculars. There is also the risk that if the centre of mass moves too far out of balance the chair can topple over, as has been reported. 
Viewing alignment at different elevations:  The axis of the skull's pivot on the spine is about in line with the ear lobes. Unless the pivots of the frame holding the binoculars coincide with this, the eyes and the eyepieces will follow different arcs. The mismatch does not have to be excessive before needing to adjust the bino's up/down and possibly fore/aft too.

It occurred to me that if I could 'wear' my binos as if they were my glasses, the adjustments would not be needed. Could this be possible with something that weighs about 16lbs? 

The key elements of the design.

1) The frame which carries the binoculars also carries the head rest, the observer's head does not touch the seat back. The frame is made to pivot about the head/spine rotation axis as exactly as possible - a position found by videoing my head nodding up and down. 

2) The seat and frame are mechanically connected by a 'four-bar' linkage (see diagram below) so that as the seat elevates, so do the binos.

Importantly the linkage is arranged so that as the seat elevates through 45 degrees, the frame also moves through 45 degrees relative to the seat. For the observer, the binoculars move from horizon to zenith for a head tilt and a body position change of only 45 degrees. Limiting the movements to 45 degrees avoids any problematic bodyweight displacement, and doesn't strain the neck. The head rest provides constant support through to the zenith and maintains the head in exactly the right viewing position in any part of the sky.

I also balanced the user/seat/binoculars setup carefully, by temporarily locking the binos at about 45degrees and climbing aboard while the setup was suspended at different points along the frame, using a plumb bob to find the c.o.g. As the rig is balanced like this, there is no need for counterweights, springs/bungees or outrigger legs. As there are no 'on the fly' adjustments, the seat construction is clean and simple.

The entire rig was designed from the start to be easily transported in a old Yaris, cars don't come much smaller than that. 

The seat sits onto trestle forks (alt axis) that are hinged to a base frame. The 4-bar frame to seat connectors fit over short pins on the fork extensions. The fork unit locates on a 'ground ring' comprising a bicycle wheel (azimuth axis) fixed to a hollow steel ring beam with adjustable legs. The trestle locks on the hub with the quick release skewer. The altitude drive, a butchered linear actuator, and the azimuth drive are both rapidly detachable. Near the ends of the fork legs are hard nylon rollers which ride on the wheel rim and take all loads directly to the ring beam. Despite using only 20mm box section steel in the forks, the overall structure is such that any disturbances are damped within a second or two.

For transportation, after the binoculars have been removed, the altitude drive and seat-frame link arms are unpinned and the seat is lifted off; the forks are folded flat and the fork unit detached from the ground ring. The seat base and the bino/headrest frame fold in against the seat back, compacting the chair. It's not quite IKEA flat pack but it all fits a very modest sized car boot and the operation takes only a few minutes.

The binochair motion is controlled by a joystick switch unit and can be driven freehand, or directed to selected targets using encoders. The altitude encoder is mounted directly to the binoculars and is actuated by a pendulum. The azimuth encoder is offset from the wheel hub on a sprung arm and is connected by a toothed pulley and belt. The encoders and interface comprise the electronics part of the 'DobsonDream' DSC kit from AstroGadget in the Ukraine.

The disassembled binochair in the car.

The ground ring/azimuth drive.

Folded altitude forks attached to azimuth unit.

Alt Az unit opened.

Seat attached to alt az unit.

Frame/seat link arms attached - binochair fully assembled.

Seat elevated (4 bar links colour coded)

Binochair design condensed.rtf

[PeterW]

Wow, very few have tried and fewer succeeded in this type of mount. Well done and a thank you for making your experience  available to others… and welcome to SGL!

 

Peter

[Peter Drew]

An interesting and well executed design.  As an enthusiastic builder of large refracting binoscopes I have wrestled with the problem with mounting them over the years.  I have built several versions of chairs that carry the observer as well as the binoscope with varying success, my main problem, as yet unresolved, is isolating my heartbeat, this produces an annoying "tick" to the view at the higher powers that binoscopes are capable of.  As a result, I have reluctantly reverted to parallelogram mounts.  I also build "reverse" reflecting binoscopes that don't have the overhead neck ache problem, I have also recently fitted the Celestron StatSense Explorer system to my 300mm model but not yet had the opportunity to use it.    🙂 

[markse68]

That’s awesome! Does it really weigh only 8kg? Are you running the Azimuth drive belt around the bike wheel and the motor travels with the seat? Have you got a video of it in operation? Great work Mr H!

Mark

[Rusted]

Congratulations. Your observing chair is ingenious and very well thought out.

I think I would have gone for a pair of quality mirrors [optical flats] for a compact, "look down" altaz set-up.
Despite suffering from image reversal and inversion. Dewing of the mirrors would probably require heaters.

[ollypenrice]

Brilliant.

I've also thought about this but never done anything about it. My thinking went along simpler (ie cruder) but bulkier lines - a wooden Dobsonion binocular chair.

Olly

[westmarch]

Just Wow!  That is one of the most elegantly designed and constructed rigs I have seen. 

Thanks so much for sharing. 

John

[old dave]

Bloody hell!!!

[Mr H in Yorkshire]

7 hours ago, westmarch said:

Just Wow!  That is one of the most elegantly designed and constructed rigs I have seen. 

John

Thanks for the appreciative comments. It has been very satisfying, firstly to analyse the problems in 'traditional' binochairs, and then to find a solution. I originally thought up the linkage usage 15 years ago, at that time I had an full suspension bike and the rear sus uses the same mechanism. It's taken a while (and much metal cutting) to finally create.

[Mr H in Yorkshire]

To any that I have not messaged my thanks, being new to this forum I did not understand how to respond directly to comments, I don't want to give the impression of ignoring anyone. I am glad the chair design has been so well received, any ideas involved that may help other constructors, you are most welcome to adopt and adapt.

After Christmas, when I have some spare time I will post a video of the chair in action. Happy Christmas.

[GrumpiusMaximus]

I would be absolutely delighted to see a video of this in action, it's absolutely fantastic.

[Mr H in Yorkshire]

Hi Grumpius, it's on my to do list. I thought about breaking it into two for file size. One of assembling and connecting the parts and another one just driving it around. My grandchildren love riding in it too! I can't say how soon because my poor wife has just broken her arm and we are a bit preoccupied. Cheers

[cajen2]

I hope you've patented the design....I wouldn't mind betting it could be a commercial success! 

[GrumpiusMaximus]

1 hour ago, Mr H in Yorkshire said:

Hi Grumpius, it's on my to do list. I thought about breaking it into two for file size. One of assembling and connecting the parts and another one just driving it around. My grandchildren love riding in it too! I can't say how soon because my poor wife has just broken her arm and we are a bit preoccupied. Cheers

All the best for a speedy recovery to your wife.

[Mr H in Yorkshire]

11 hours ago, cajen2 said:

I hope you've patented the design....I wouldn't mind betting it could be a commercial success! 

Hi there,

Thanks for that but I am much happier to share this design in the community than try to commercialise it. It costs a fortune to patent something and it would require a substantial engineering analysis and there are numerous other complications involved, just not for me. The only real innovation is the 4-bar linkage and anyone can use that.

[Rusted]

A patent requires a unique factor to become registered as an invention or breakthrough.
30 years ago I developed a linkage geometry. Which gave "girder" forks [for a mountain bike] 180mm/7" travel.
A chat with a patents office advisor, on the phone, quickly ended any hope of my "cashing in" on my "invention."
 

[Mr H in Yorkshire]

9 hours ago, Rusted said:

A patent requires a unique factor to become registered as an invention or breakthrough.

Hi Rusted, from a old friend of mine who had a sizeable scientific equipment company I understand that existing and known 'inventions', even something as simple as a screw threaded rod, if used in a novel situation, could be patented, so the 4-bar linkage, unless already patented or registered as prior art in some way, qualifies. However, making the design universal needs a whole engineering study and would probably require all the up/down in/out adjustments that I wanted to do away with. This chair is designed to fit ME but wont fit someone 6' 6" or 5' 3" because their pelvis to eyeball distance is different. It can be adapted, I actually made the seat base up/down adjustable initially  but then thought why bother. I could probably overcome the engineering issues but there are so many complications , let alone an investment way beyond my means, involved in making a business product hat it just is not worth it to me.

PS my son has given me back an original PST that I bought him for his 18th, I'm going to parallel mount it with a very old 90mm meade SCT with solar filter for H alpha and white light viewing. All that's needed is some daylight, the Yorkshire weather has been vile for weeks now. Is this atlantic weather clouding you out too.

[Rusted]

11 minutes ago, Mr H in Yorkshire said:

Hi Rusted,

<snip>

PS my son has given me back an original PST that I bought him for his 18th, I'm going to parallel mount it with a very old 90mm meade SCT with solar filter for H alpha and white light viewing. All that's needed is some daylight, the Yorkshire weather has been vile for weeks now. Is this atlantic weather clouding you out too.

You make perfectly valid points. I was generalising.

The PST + 90 sounds like a good plan.
PSTs are notoriously variable in image quality. You may be lucky and get a really good one.
Then begins the downward spiral into poverty and lunacy. As H-alpha solar gets under your skin.
You discover that  PSTs can be taken apart and added to much larger telescopes!!
You can probably see where this is going.

[Coco]

Superb! Cannot think of a better way to enjoy the evening.

[Paz]

Wow that is a great bit of kit. I have wondered sometimes about a binoscope or binoculars in a contraption like a gun turret from a world war 2 bomber (or the millennium falcon!).

[DirkSteele]

This is one of the coolest things I have seen on this forum. In a day dream I thought about something like this for my 4” class triplets but it never moved passed the daydream stage.

[Mr H in Yorkshire]

@Coco @Paz @DirkSteele

Thanks all for those very appreciative comments, I'm a bit surprised by the sudden recent interest.

I'm actually working on a trailer based successor to the fold-up lightweight version, and I had hoped to have some stuff to post but I'm having some problems with the az drive, so may be a while yet. As my wife says, this is about the journey, so what if the path is long!

[Albir phil]

On 23/12/2022 at 00:08, Peter Drew said:

An interesting and well executed design.  As an enthusiastic builder of large refracting binoscopes I have wrestled with the problem with mounting them over the years.  I have built several versions of chairs that carry the observer as well as the binoscope with varying success, my main problem, as yet unresolved, is isolating my heartbeat, this produces an annoying "tick" to the view at the higher powers that binoscopes are capable of.  As a result, I have reluctantly reverted to parallelogram mounts.  I also build "reverse" reflecting binoscopes that don't have the overhead neck ache problem, I have also recently fitted the Celestron StatSense Explorer system to my 300mm model but not yet had the opportunity to use it.    🙂 

 

[Albir phil]

That's a great design well thought out . I to like Peter have built some large reflecting binos and always never seem to get a good comfortable position.your design looks like it could be.Great job👍

[Mr H in Yorkshire]

@Albir phil Glad to heat that. It fulfils my specific design ideas, including lightweight / portable. As Peter says about heartbeat, it is detectable but not unacceptable due to the low magnification. It would need a different design for anything higher. I have some ideas to eliminate the problem in my next project - a 'double' seat, the inner one suspended from the outer, and deep pneumatic cushioning for a start.