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Building A Hargreave Strut

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#1 C11GPS

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Posted 23 July 2010 - 03:47 PM

In another thread I was asking about how to solidify my AR6 mount using a CG5 and got a great reply that makes alot of sense... adding a Hargreave Strut. Ive researched it a bit but cant find plans/insturctions. Can anyone help me out? Steve

#2 mclewis1

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Posted 23 July 2010 - 04:06 PM

Have a look at Steve Fisher's setup. link

His implementation is pretty straight forward. Another split tube ring, a couple of small turnbuckles, some mounting hardware to attach the turnbuckles to the each end and a rod or length of flexible cable. You could probably reduce the h/w a bit by choosing a rod that can be threaded to fit the turnbuckles directly, and maybe do away with one of them, that way it might even be a bit stiffer and offer some compression protection (rather than just the extension protection that a flexible cable would provide).

#3 Bob Myler

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Posted 23 July 2010 - 06:33 PM

See article entitled "The Hargreaves Strut" by Tom Dobbins in the September 2001 issue of Sky & Telescope. He gives you a materials list plus detailed instructions on how to assemble one. It's a relatively sophisticated, lightweight design incorporating 1/2" O.D. aluminum tubing, two ball and socket universal joints, two tubular standoffs, an SS conduit clamp, and of course, an extra tube mounting ring to fit your ota. Much of this stuff is available from McMaster-Carr and other supply houses.

Steven, if you are unable to find this article, PM me.

#4 Pedestal

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Posted 23 July 2010 - 09:49 PM

Tube end: The block underneath the heim joint is not vital, just handy. The tube clamp is ordinary off the shelf item. Most come with 1/4"x20 threaded hole, a bolt secures the heim joint. A classier solution would use a heim joint with a 5/16" or 3/8" hole and a proper sized axle bolt.

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#5 Pedestal

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Posted 23 July 2010 - 10:18 PM

The bottom end: Several ways to go here. The ASGT CW bar has a 6mm threaded hole for the toesaver. I wanted preserve the little 1lb Scopestuff CW, and handily, it also has a 6mm thrd hole on the back side so you can stack them. The aluminum piece was some scrap left over from another project. A few minutes with the table saw shaped it up. Drilled and tapped a 1/4"x20 hole to secure the joint. The rod is just a piece of hardware store 5/16" steel rod, cut to length and threaded with a die nut. All the bolts and such are SS, no rust worries.
Amazingly, I was able to find everything from a local hardware store, although I usually resort to McMas-Carr also for projects of this sort.
The critical thing is to be able to get the strut stiff-if it wiggles a bit, its not doing the job.

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#6 urbanMark

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Posted 24 July 2010 - 02:44 AM

Any rules of thumb about how effective a Hargreave Strut would be on a given setup?

#7 LeoLion

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Posted 24 July 2010 - 03:55 AM

Hi , You may find this link to Shevill Mather's use of the strut of interest http://picasaweb.goo...feat=directlink . Hope this is of use to someone !

#8 Steve Fisher

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Posted 24 July 2010 - 05:36 PM

Some great links and articles. I have used this setup on both my 6" f/12 and my 8" f/12. Pretty simple only takes these materials. I wrapped the threaded rod in heat shrink. It just looks a little cleaner.

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#9 Steve Fisher

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Posted 24 July 2010 - 05:41 PM

Any rules of thumb about how effective a Hargreave Strut would be on a given setup?


Hard to give you a "rule of thumb" but for me the addition is HUGE. Some have had more limited results but it makes my 8" f/12 very stable for visual use on a CGE. That is remarkable. :jump:

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#10 Pedestal

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Posted 24 July 2010 - 10:31 PM

Slick idea with the shrink wrap, I'm going to promptly steal it! I've been in a quandry on how to finish things.

#11 urbanMark

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Posted 25 July 2010 - 02:49 AM

WOw - an 8" f/12 on a CGE - that is impressive. Hummm....I wonder how big a refractor I could get on my G-11 w/ a Hargreave Strut...

#12 etsleds

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Posted 25 July 2010 - 02:34 PM

I've been considering this to stiffen up refractor setup, but had not been sure whether the strut works best loaded under slight compression or tension - my intuition would say compression.

Steve's setup is presumably under tension. Anyone have observations on effectiveness from trying both?

#13 Steve Fisher

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Posted 25 July 2010 - 03:12 PM

I've been considering this to stiffen up refractor setup, but had not been sure whether the strut works best loaded under slight compression or tension - my intuition would say compression.

Steve's setup is presumably under tension. Anyone have observations on effectiveness from trying both?


Now the strut helps me position my OTA in the rings. The first time I set it up with the strut I balanced the OTA perfectly in the mount. Then I cut the strut to the desired length. Now when I'm setting up I know that when the strut reaches from the ring to the toe plate that the OTA is in the right position. No guesswork for proper position in rings. Balances first time everytime.

Hook the strut hooks to the two eyes and tighten the turnbuckles till taught. Nothing past finger tight. You can feel when it is correct. It takes very little tension to complete the triangle.

This makes portable observing VERY doable with the CGE and the 8". There is some wobble when focusing but settles down is less than one second. To make it perfect it would require an electronic focuser. I'm not going to invest in one but it might help even more.

When balanced well the CGE doesn't even break a sweat. It thinks it has a small scope on it. :grin:






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