Pier - H beam/iron?

[malc-c]

On 24/10/2023 at 06:18, 900SL said:

I'm a structural engineer. What height pier and mount type/load?

Regardless of the type and cross section of the pier, it seems we all then use three M10 / M12 bolts or threaded rod with washers and nuts to secure a plate carrying the mount.  Doesn't this make the the thickness or design of the pier less important, especially as that second plate is often placed high enough to allow the fitting of the central bolt to secure the mount to it.  Granted the options are limited, either using a hole cut out of a length of pipe or box section or two plates, but I sometimes feel the size of bolt is often overlooked and the choice of bolt and its length makes the over engineered base a bit pointless?

[900SL]

2 hours ago, malc-c said:

Regardless of the type and cross section of the pier, it seems we all then use three M10 / M12 bolts or threaded rod with washers and nuts to secure a plate carrying the mount.  Doesn't this make the the thickness or design of the pier less important, especially as that second plate is often placed high enough to allow the fitting of the central bolt to secure the mount to it.  Granted the options are limited, either using a hole cut out of a length of pipe or box section or two plates, but I sometimes feel the size of bolt is often overlooked and the choice of bolt and its length makes the over engineered base a bit pointless?

I ran the numbers on this very issue over on CN

This analysis assumed 4 bolts, M16, 150mm between plates, 10 kg lateral load

https://www.cloudynights.com/topic/610052-for-those-using-rat-cage-design-for-those-selling-them-got-vibrations/?p=12694158

[900SL]

And here's an earlier post.. I have a low tolerance for 'smatterers' 😆 

https://www.cloudynights.com/topic/610052-for-those-using-rat-cage-design-for-those-selling-them-got-vibrations/?p=12693495

[david_taurus83]

29 minutes ago, 900SL said:

I ran the numbers on this very issue over on CN

This analysis assumed 4 bolts, M16, 150mm between plates, 10 kg lateral load

https://www.cloudynights.com/topic/610052-for-those-using-rat-cage-design-for-those-selling-them-got-vibrations/?p=12694158

I went for M16 bolts but 3 of them, as you day, 4 is difficult to level without warping the base. Also using a round brake disc and have left only enough room underneath to get a ratchet wrench in to tighten up the mount.

[tooth_dr]

3 minutes ago, david_taurus83 said:

a round brake disc

Was there a specific disc you used David? Is there any chance of a photo of the underside?

[david_taurus83]

59 minutes ago, tooth_dr said:

Was there a specific disc you used David? Is there any chance of a photo of the underside?

I think it was for a Golf. I searched for one that had a centre bore just large enough for the bottom of my AZEQ6 to fit into. What mount did you say you were going to use? I can send you the spare disc if you want it. I owe you a favour after all.

[900SL]

1 hour ago, david_taurus83 said:

I went for M16 bolts but 3 of them, as you day, 4 is difficult to level without warping the base. Also using a round brake disc and have left only enough room underneath to get a ratchet wrench in to tighten up the mount.

Cantilever deflection is a function of height cubed, so keeping the bolts short greatly reduces deflection 

[tooth_dr]

45 minutes ago, david_taurus83 said:

I think it was for a Golf. I searched for one that had a centre bore just large enough for the bottom of my AZEQ6 to fit into. What mount did you say you were going to use? I can send you the spare disc if you want it. I owe you a favour after all.

I bought a used NEQ6. I’ve dug out the welder here, see what I can come up with 😬 appreciate the offer and might still avail of it.  Cheaper than buying a lathe. 

[david_taurus83]

I'm taking my AZEQ6 off the pier and putting the AM5 on there to see if it guides better so will send you some pics tomorrow of how the AZ sits on there.

[tooth_dr]

3 minutes ago, david_taurus83 said:

I'm taking my AZEQ6 off the pier and putting the AM5 on there to see if it guides better so will send you some pics tomorrow of how the AZ sits on there.

Thanks David 👍🏼

[david_taurus83]

@tooth_dr Here's some pics. The PCD pattern on the flange on my pier isnt divisible by 3 so the 3 bolts are unequally spaced but its not an issue. I just made a template over the flange and put onto the disc and marked the centres before drilling. The bore of the disc is 65mm which is perfect for the AZEQ6. Not sure if the NEQ6 is the same. I also had to drill and tap for the North peg. An M12 bolt underneath then with a metal plate to bridge the recess in the disc holds it all down.

 

[tooth_dr]

43 minutes ago, david_taurus83 said:

@tooth_dr Here's some pics. The PCD pattern on the flange on my pier isnt divisible by 3 so the 3 bolts are unequally spaced but its not an issue. I just made a template over the flange and put onto the disc and marked the centres before drilling. The bore of the disc is 65mm which is perfect for the AZEQ6. Not sure if the NEQ6 is the same. I also had to drill and tap for the North peg. An M12 bolt underneath then with a metal plate to bridge the recess in the disc holds it all down.

 

Hi David. That’s very helpful. A small piece of rectangular bar, that’s what I couldn’t think of, but can see how its obvious now for holding the eq6 onto the disc. Thank you!

[david_taurus83]

27 minutes ago, tooth_dr said:

Hi David. That’s very helpful. A small piece of rectangular bar, that’s what I couldn’t think of, but can see how its obvious now for holding the eq6 onto the disc. Thank you!

No problem. Like I said, if you want the spare disc your welcome to it. I can even drill it for you if you can let me know the bolt pattern on your pier.

[900SL]

Very neat David. I think that would work with a Vixen SXD2 mount too. I'll check the drawing of the base in the user manual later

[tooth_dr]

Just wanted to continue the updates here.

I was gifted the DN pipe so beggars can’t be choosers!  The DN100 was a 2m length so too long.  I established the required length for my observatory - 1.06m - then cut the flange off one end and shortened the pipe accordingly.

Plan is to weld it up tonight.

 

 

[tooth_dr]

Hasn’t welded in my life until a few days ago, gave it a go and ended up with this.

 

 

[Mandy D]

I can't understand why you didn't cut the flange off at the weld, then put the shorter pipe into the flange like the original. It would have been much easier and a lot stronger than attempting a butt joint.

[tooth_dr]

7 minutes ago, Mandy D said:

I can't understand why you didn't cut the flange off at the weld, then put the shorter pipe into the flange like the original. It would have been much easier and a lot stronger than attempting a butt joint.

There are a couple of reasons why that didn’t happen 😊 but I don’t really feel like explaining myself.   I’m happy with my work but thanks for your feedback.

[900SL]

9 hours ago, tooth_dr said:

Hasn’t welded in my life until a few days ago, gave it a go and ended up with this.

 

 

That's pretty good welding for a novice!

Stick or MIG? 

[tooth_dr]

1 hour ago, 900SL said:

That's pretty good welding for a novice!

Stick or MIG? 

Cheers! I used a mig welder, gasless with flux cored wire.   Should have bevelled the edges of each pipe but lack of experience.

[900SL]

Nice job. Single V butt weld with 1mm root gap would work 😀 

Assuming the weld got a couple of mm penetration into the gap then you should be good, the mount doesn't impose much load on the joint, certainly nowhere near the weld capacity. Just check for any cracks, lamellar tears or fusion defects

 

Edited November 8, 2023 by 900SL

[tooth_dr]

@900SL I cant see the inside of the pipe as it's coated in a thick cement motor lining, but i was going to fill the pipe with cement once in place, to provide a final level of protection.