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Wire spider tensioners, simple-light-cheap

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29 replies to this topic

#1 Bob4BVM

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Posted 28 July 2016 - 09:58 PM

Part of my dob rebuild is a new UTA.

Looking at lots of spider options here on CN.

Think I am going with wire, here is my plan for the tensioners.

WAY less $$$ than guitar tuner heads...

 

Nothing is to scale in the dwg, just a concept sketch

 

PICT6317s.jpg


Edited by Bob4BVM, 28 July 2016 - 10:29 PM.

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#2 Joe1950

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Posted 28 July 2016 - 10:25 PM

That's nice. I read an article by someone who did a similar arrangement, but I like your's better. He was thrilled with the performance. The wires can be as thin as .008" I believe. He didn't even paint the wires black to keep them as thin as possible. You can even get black strings.

 

Good idea.



#3 Jeff Morgan

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Posted 28 July 2016 - 11:28 PM

Your plan looks quite similar to this one:

 

http://www.reinervog...ng/2_Hut_e.html



#4 Oberon

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Posted 29 July 2016 - 02:20 AM

At a mere 56c each for a guitar head there isn't a LOT of room for saving cost.

 

http://www.ebay.com/...BYAAOSwPcVVzpkV


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#5 mark cowan

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Posted 29 July 2016 - 02:55 AM

True, the only reason to build this part are (a) because you wanted to (b) to make it fit better in the upper cage (or ring) ( c ) for the weight savings on an ultralight  or (d) because you want 100% corrosion resistant hardware.



#6 Oberon

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Posted 29 July 2016 - 05:05 AM

Good decision though to build a wire spider. Build it right and it will outperform the standard commercial spiders in almost every way, and be quicker and cheaper. Obviously the threaded rod method works but I'd strongly encourage use of guitar machine head tuners; they are cheap and extremely effective.



#7 m. allan noah

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Posted 29 July 2016 - 07:07 AM

I'm using something similar in a scope I am building now, with a couple differences. 1. Use a nylock nut instead of separate jam nut. 2. keep the head on the screw so that if the wire breaks, the screw cannot fall out of the UTA. A variation I considered was to drill an axial hole thru the screw, and pass the wire thru the screw to a crimp on the outside.

 

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#8 Bob4BVM

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Posted 29 July 2016 - 12:11 PM

Your plan looks quite similar to this one:

 

http://www.reinervog...ng/2_Hut_e.html

 

Yes, nice !

Thanks for that link Jeff, lots of great ideas there !

Bob



#9 Bob4BVM

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Posted 29 July 2016 - 12:17 PM

I'm using something similar in a scope I am building now, with a couple differences. 1. Use a nylock nut instead of separate jam nut. 2. keep the head on the screw so that if the wire breaks, the screw cannot fall out of the UTA. A variation I considered was to drill an axial hole thru the screw, and pass the wire thru the screw to a crimp on the outside.

 

allan

 

Yes, i'll use locknuts as well. Also will add a small flat washer under nut and divise a way to hold the stud from rotating while turning nut.

 

As for the axial hole, that'd be a clean look but I don't think i'd have the patience to drill tiny holes thru the length of 8 small screws ! :)_

 

CS,

Bob



#10 Bob4BVM

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Posted 29 July 2016 - 12:23 PM

Good decision though to build a wire spider. Build it right and it will outperform the standard commercial spiders in almost every way, and be quicker and cheaper. Obviously the threaded rod method works but I'd strongly encourage use of guitar machine head tuners; they are cheap and extremely effective.

 

To me the tuners are a lot more complicated to mount.

And with their mounting brackets are quite a bit heavier.

And finally, they look like, well ...they look like guitar tuners ! :)   ( I play guitar, so nothing against tuners, TEHO :)  )



#11 mark cowan

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Posted 29 July 2016 - 03:03 PM

Yeah I agree with all that.  Tuners just look wrong, exactly the opposite of how they look right on the guitar.   :shrug:

 

I've used old scrap ones for mockups of wire spider layouts (here shown with dental floss for wires):

 

angled view.jpg

 

 

 

 



#12 jtsenghas

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Posted 29 July 2016 - 07:38 PM

A similar method that won't require drilling the screws would be to use drilled head cap screws. These are available in a variety of materials including stainless. They are designed for being wired for safety against unscrewing on machinery. In this application the head can face inwards and the nut outwards, also protecting against falling hardware if a wire breaks. 


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#13 Bob4BVM

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Posted 29 July 2016 - 07:43 PM

A similar method that won't require drilling the screws would be to use drilled head cap screws. These are available in a variety of materials including stainless. They are designed for being wired for safety against unscrewing on machinery. In this application the head can face inwards and the nut outwards, also protecting against falling hardware if a wire breaks. 

Good idea, I have used those on other projects.

Plus the head will give me something to grab when tightening the nut for tension


Edited by Bob4BVM, 29 July 2016 - 07:44 PM.


#14 RAC

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Posted 29 July 2016 - 08:01 PM

I've done mine like this so then you can pivot them around to align all the wires. It's been about a year and I've never had to ever change any wire settings. It's all rock solid. I'm using thin E strings with a 4" secondary in a 20" f3.8 scope.

wirespider.jpg


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#15 Oberon

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Posted 29 July 2016 - 09:18 PM

Ditto. And by choosing black I lost the appearance of a guiter tuner out of place.

 

But when it comes to style, each to his own.  :imawake:

 

gallery_217007_4913_59828.jpg


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#16 mark cowan

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Posted 29 July 2016 - 10:43 PM

An advantage to stealth hardware for tensioning is people are much less likely to fiddle with it, though.  And it can be made cheap, easy. and reliable with a little ingenuity.


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#17 Bob4BVM

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Posted 29 July 2016 - 11:39 PM

An advantage to stealth hardware for tensioning is people are much less likely to fiddle with it, though.  And it can be made cheap, easy. and reliable with a little ingenuity.

Whoa, I never thought of that little issue !

I do a lot of star parties for local schools, the kids like to touch everything on the scopes !!!  :-]



#18 mark cowan

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Posted 30 July 2016 - 12:32 AM

It makes even more sense because most wire spider strings are rarely in need of adjustment once set up properly.  You'll have to deal with people keeping their hands off the wires but that's easier than a knob that screams "turn me!" :lol:



#19 Bob4BVM

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Posted 30 July 2016 - 01:14 PM

It makes even more sense because most wire spider strings are rarely in need of adjustment once set up properly.  You'll have to deal with people keeping their hands off the wires but that's easier than a knob that screams "turn me!" :lol:

 

For sure, thanks again for the warning Mark ! :)

CS,

Bob



#20 Oberon

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Posted 10 March 2017 - 11:14 PM

Here is a simple design for your consideration...

gallery_217007_7272_44020.png

This design solves Bob and Mark's dislike of guitar tuners looking out of place, or attractive for little fingers, whilst retaining their ease of use (with a tool) for very fine convenient adjustment in six axis. Cheap, convenient, fast, intuitive, no lock nuts or lock-screws.


Edited by Oberon, 11 March 2017 - 12:00 AM.

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#21 Jeff Morgan

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Posted 11 March 2017 - 12:14 AM

So the purple bracket moves up or down with the turning of the 75mm screw, sliding along the tube.

 

I would imagine this requires cutting the wires fairly close to their required length. Limited travel.

 

In your experience, is a lot of "extra" length of wire, or length of travel, required?



#22 Oberon

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Posted 11 March 2017 - 12:30 AM

As drawn there is plenty of adjustment, you won't have any trouble with the wires if you've set the secondary up in a jig prior to running and tying off the wires.

Also, there is just as much adjustment with this method as with any eyelet style, such as the OP, and its a little less likely to intrude on the beam. Only a guitar tuner style is better that way.


Edited by Oberon, 11 March 2017 - 12:43 AM.


#23 jtsenghas

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Posted 11 March 2017 - 07:22 AM

This design solves Bob and Mark's dislike of guitar tuners looking out of place, or attractive for little fingers, whilst retaining their ease of use (with a tool) for very fine convenient adjustment in six axis. Cheap, convenient, fast, intuitive, no lock nuts or lock-screws.

I LIKE that. This variant of the original post could be executed very neatly for appearances, doesn't require any extra holes in the UTA, and sets the wire angles at very controllable directions. The hole locations in the UTA rings could be marked and drilled last to match the holes in the sliding members after an initial install for offset vane arrangements whose angles are a little more complicated in plan view. Of course, any twisting forces on those sliding members if the wires are not in the same planes as the axes of those tubes would be trivial anyway. 

 

One thing I like about this design that may not be readily apparent is how it helps with the use of UTA baffles. The wires wouldn't have to pass through such baffles and tuning could be done from above and below the UTA with a screwdriver, even if one or more of those adjustment screws are just inside of truss attach points. 

 

Good thinking! 


Edited by jtsenghas, 11 March 2017 - 07:44 AM.


#24 jtsenghas

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Posted 11 March 2017 - 07:40 AM

This method could also be used in conjunction with screw eyes to attach wires to specific heights on the UTA tubes, such as in Mark's mockup in post 11 above. In that case, the wire would attach to the sliding member parallel to the adjustment screw and even less screw range would be needed because wire length changes would 1:1 with screw adjustments just as they would be with guitar tuners.


Edited by jtsenghas, 11 March 2017 - 07:42 AM.


#25 Oberon

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Posted 11 March 2017 - 08:03 AM

 

This design solves Bob and Mark's dislike of guitar tuners looking out of place, or attractive for little fingers, whilst retaining their ease of use (with a tool) for very fine convenient adjustment in six axis. Cheap, convenient, fast, intuitive, no lock nuts or lock-screws.

I LIKE that. This variant of the original post could be executed very neatly for appearances, doesn't require any extra holes in the UTA, and sets the wire angles at very controllable directions. The hole locations in the UTA rings could be marked and drilled last to match the holes in the sliding members after an initial install for offset vane arrangements whose angles are a little more complicated in plan view. Of course, any twisting forces on those sliding members if the wires are not in the same planes as the axes of those tubes would be trivial anyway. 

 

One thing I like about this design that may not be readily apparent is how it helps with the use of UTA baffles. The wires wouldn't have to pass through such baffles and tuning could be done from above and below the UTA with a screwdriver, even if one or more of those adjustment screws are just inside of truss attach points. 

 

Good thinking! 

 

 

I thought of it while looking at the OP image, and initially sketched it up thinking I was offering a variation on the theme. Then I realised I has misunderstood Bob's sketch, I was looking at it wrong.


Edited by Oberon, 11 March 2017 - 08:07 AM.



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