Author Topic: PRELIMINARY DRAWING - 21' Tall Tilting Mast  (Read 775 times)

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Offline kbellis

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PRELIMINARY DRAWING - 21' Tall Tilting Mast
« on: November 25, 2018, 01:46:33 PM »
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Is there a structural engineer in the house? If by any chance there is, please red line the attached drawing and forward it with any comments to me directly - thank you very much.

There is still more work needing to be done on the attached drawing of
the tilting mast, but should be enough for a structural engineer to
determine adequacy for withstanding category 5 winds.

Happy Thanksgiving, left overs still!

Kind regards,

Kelly

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V. Kelly Bellis, PLS
17 Union Street
Ellsworth, ME 04605



Offline Cutty Sark Sailor

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Re: PRELIMINARY DRAWING - 21' Tall Tilting Mast
« Reply #1 on: November 25, 2018, 02:15:55 PM »
I can't speak to Cat 5 winds, but this tilt, built on a Davis tilt-mount and attached to fence, has done fine since 2011 with highest 73mph recorded... guy wires are NOT technically correct but work fine....Vue ISS, Blitzortung E Probe assembly, Hikvision 2032 camera on mast... right hand fibergalss 21' has 2 Blitzortung E field probe assemblies mounted... no guy wires.. it's fiberglass 'kite' pole, and does fine swinging in the breeze... heh..
« Last Edit: November 25, 2018, 02:20:50 PM by Cutty Sark Sailor »
 

Offline kbellis

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Re: PRELIMINARY DRAWING - 21' Tall Tilting Mast
« Reply #2 on: November 25, 2018, 02:35:59 PM »
Sweet!

How often do you wrangle with the guyed mast for maintenance on your PWS?

Offline kbellis

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Re: PRELIMINARY DRAWING - 21' Tall Tilting Mast
« Reply #3 on: November 25, 2018, 02:41:53 PM »

Offline bks97

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Re: PRELIMINARY DRAWING - 21' Tall Tilting Mast
« Reply #4 on: November 25, 2018, 02:43:32 PM »
Here is the link to a photo and description of a 24-ft folding mast I built last spring using 4x4 treated posts and an old telescoping TV antenna pole.

https://www.wxforum.net/index.php?topic=34234.msg348930#msg348930

Offline kbellis

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Re: PRELIMINARY DRAWING - 21' Tall Tilting Mast
« Reply #5 on: November 25, 2018, 02:58:23 PM »
Nicely done Bill! Though I'm totally unclear what the creature at the end of the wind vane might be.

I'm guessing that lowering the anemometer isn't as frequently done as the main bits on the lower mast?

Offline Cutty Sark Sailor

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Re: PRELIMINARY DRAWING - 21' Tall Tilting Mast
« Reply #6 on: November 25, 2018, 03:00:38 PM »
Sweet!

How often do you wrangle with the guyed mast for maintenance on your PWS?
Yearly....change batteries, etc...  I need to pull it down and make slight adjustment on the camera angle... just too lazy... I guess it takes an hour total to tilt and clean ISS and any other normal maintenance... ... I could do the cam in about 15 minutes max, just to lazy to do it right now
 

Offline bks97

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Re: PRELIMINARY DRAWING - 21' Tall Tilting Mast
« Reply #7 on: November 25, 2018, 03:43:46 PM »
Nicely done Bill! Though I'm totally unclear what the creature at the end of the wind vane might be.

I'm guessing that lowering the anemometer isn't as frequently done as the main bits on the lower mast?

If I understand what you are referring to, the photo makes it look like there was a bird or something on the anemometer propellers when I took the picture.  But itís just the propellers.

I havenít had to fold the mast yet, but if necessary it is a simple job of unhooking the guy wires, removing one bolt, and lowering it.  As long as the anny does its job, the mast will stay up.  I could extend the antenna pole up another 4 feet or so if I wish to do so, but Iím not convinced it would make much difference. 

Offline Mattk

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Re: PRELIMINARY DRAWING - 21' Tall Tilting Mast
« Reply #8 on: November 25, 2018, 04:27:57 PM »
To begin with that plan is unreadable at a reasonable scale to read and view, resolution is simply not good enough and neither is a PNG file.

Offline kbellis

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Re: PRELIMINARY DRAWING - 21' Tall Tilting Mast
« Reply #9 on: November 25, 2018, 04:31:18 PM »
That's just the thumbnail; download the PDF. That's linked in the first post above.

Offline Mattk

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Re: PRELIMINARY DRAWING - 21' Tall Tilting Mast
« Reply #10 on: November 25, 2018, 06:06:15 PM »
Much better. Note I am not an engineer but having done similar things I will make the following comments

21' of 1-5/8" will have way too much flexibility, in a Cat 5 breeze the station would basically be destroyed on top of that
1 * 3/8" pivot bolt and lock bolt is a little light on? Also no redundancy if a single bolt fails
1/2" foundation bolts ?? For 5-6 metre tapered gal poles I've simply standardized a 20mm (3/4") 233mm PCD, nothing has fallen over yet

I may put an anemometer on such a structure/design but wouldn't contemplate a complete station. Just my thoughts.
 

Offline kbellis

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Re: PRELIMINARY DRAWING - 21' Tall Tilting Mast
« Reply #11 on: November 25, 2018, 06:25:43 PM »
Thanks for looking Matt. I'm not an engineer either and was why I was asking if there was one on this forum.

The steel pipe is schedule 40 with 0.14 wall thickness supported by (2) 0.375 stainless steel bolts. If I understand correctly, you're suggesting a third?

Offline kbellis

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Re: PRELIMINARY DRAWING - 21' Tall Tilting Mast
« Reply #12 on: November 25, 2018, 06:27:15 PM »
What is PCD?

Offline Mattk

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Re: PRELIMINARY DRAWING - 21' Tall Tilting Mast
« Reply #13 on: November 25, 2018, 07:50:26 PM »
Pitch Circle Diameter, just a simple tern to define the diameter of a circle that passes through the centre of the bolt holes.

To me any bolt is a single point of failure, from what I see you have 1 bolt basically as a hinge and another securing bolt, I would have another securing bolt, or do you have another securing bolt, in that case yes I would want 3 if your intent is Cat 5, big ask.     

Offline kbellis

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Re: PRELIMINARY DRAWING - 21' Tall Tilting Mast
« Reply #14 on: November 25, 2018, 11:16:55 PM »
Thanks for the follow up and the meaning of the term PCD.

Though it was not intended, the bolt layout conforms to the formula for PCD, coincidentally. I fail to see the relevance as the moment of rotation about the vertical axis is nearly zero.

Additional bolts between the pivot and bottom lock bolts sounds like a good idea.

Thanks again for your help.

Kind regards,

Kelly

Offline the beteljuice

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Re: PRELIMINARY DRAWING - 21' Tall Tilting Mast
« Reply #15 on: November 26, 2018, 01:28:23 AM »
You have guys - good !
the beteljuice used to have a 30 ft mast that required two sets of guys and it could still wobble / oscillate in a strong wind !

Most tilt designs I have seen rarely pivot or bolt through the mast. Typically the mast is secured to a 'cradle' (welded or U-bolts depending on materials used), and it is the cradle that is hinged and also able to be locked in the upright position.

... just a thought.
Imagine what you will KNOW tomorrow !

Offline kbellis

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Re: PRELIMINARY DRAWING - 21' Tall Tilting Mast
« Reply #16 on: November 26, 2018, 06:48:27 AM »
Yes, I've had and still have reservations about piercing the wall of the pipe particularly at the most stressed location. Again, I'm a land surveyor, not an engineer and was why I was soliciting comments from any interested structural structural engineer.

Welding the HDG steel pipe is certainly possible, though it will interrupt the zinc-polymer coating and introduce another set of galvanic-related problems. An isolated compression sleeve at the pivot point could accommodate what I understand you are suggesting.

I expect the idea, once it might ever be properly tuned up, will be prohibitively expense. More on that after I've met with the steel fabricators later today.

Offline kbellis

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Re: PRELIMINARY DRAWING - 21' Tall Tilting Mast
« Reply #17 on: November 26, 2018, 06:55:10 AM »
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This guyed mast wasn't for a PWS, but rather a temporary transmission tower as an UHF experiment with a 1-watt radio.

 

anything