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How not to build a pier footer!

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#51 JerryWise

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Posted 14 February 2008 - 04:44 PM

Good plan Scott.

#52 JimHawkins

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Posted 17 March 2008 - 09:25 AM

Looks like your "Concrete Contractor" was a real JERK!!@!

I'll be building on a pre installed PAD with an isolated PIER (18feet down). Lucky to have found it.
Jim

#53 Spoonsize

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Posted 17 March 2008 - 10:43 AM

UPDATE! UPDATE!

We need an update from "da-man" Scott!

#54 mikey cee

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Posted 17 March 2008 - 10:44 AM

Now if that is a normal dimensioned pier above ground that thing is going to be proportioned like a "stringbean". You'll be way to close to seismic activity that deep! :smirk: :grin: :grin:Mike

#55 DeanS

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Posted 17 March 2008 - 10:55 AM

I agree that testing before you cut is important. Once you cut, well, its cut.

I have never been convinced that a pier that moves up and down can be perfectly rock solid, although I have seen many high end imagers use them. Setting up the same scope on a tripod next to it would sure help eliminate some things.

You had mentioned a heater with fan making the views soft. I am assuming you tested this with fan only and no heat? Even a small amount of heat rising up thru the dome will deteriorate the seeing, and even a large persons body heat can make a noticable effect too. And using the LX200 at 400x is also really pushing the limits of that scope and I can see that the heat would easily effect that. A good reason to try it out side too as someone sugggested.

Lots of testing to do and I think you are on the right track with your list above. I still would look into a solid 1 piece pier with your coming equipment.

My concrete pad has an area under the center dug out about 6' x 6' x 3' deep and I have bolted 2 piers about 6' apart over this area. But the main floor area is about 12" thick with the 'walls' turned down 3'. The only issue I have is closing or opening a door to hard or quick which may cause the guide star to jerk but other wise I walk around while imaging with no problems.

Here is a link to a pic of my pad being rubbed down.
http://www.doghousea...oncrete pad.jpg

Good luck.

#56 Paula E

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Posted 17 March 2008 - 09:46 PM

UPDATE! UPDATE!


Heh, it has been a while! I should have lots of well documented test results to give you. But really I have only one - my lx200 seems pretty shaky all on it's own - I just thump it slightly, anywhere on the fork, and it vibrates like crazy.

In my defense:
1. We had several weekends of just amazing weather - and I spent my testing time observing stuff. :p
2. I got word that my new scope and mount were finally on the way, so my motivations to experiment on the lx200 were diminished.

I did setup my new scope and mount on a pier-tech vibration isolation platform:

Posted Image

The platform is quite interesting. It's basically spring-like coils of what appears to be some sort of stainless steel cabling. (Vito at Pier-tech refers to them as "heliacal isolators.")

Unloaded, the platform is quite rigid. As you apply weight to it, the isolators compress slightly. The platform still feels pretty solid - but if you apply sufficient force, for example bumping your head on the scope in the dark like a big klutz, the scope and mount will sway slightly for a moment, and then dampen down quickly. I suspect that any sort of vibration from the dome, walking around, dome drives, etc. probably aren't going to get through this thing. However, it seems to be possible to make the scope sway if you impact it. (A strong wind would probably do it too - it was really windy last night, 15-20 MPH winds, and with the shutter facing somewhat into the wind, the scope would sway slightly, although never for very long. (The conditions last night were bad enought that I really couldn't tell much about the performance of this thing one way or the other.) It acts like a shock absorber though.

I hope to hookup a camera to the scope to test this out soon.

#57 DeanS

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Posted 18 March 2008 - 08:20 AM

Glad to hear it may have been false alarm and the isolator looks like it should really do the job.

I had assumed earlier that you were familar with the LX200 mounts, but what you experienced is normal for them. On a wedge they are even worse which makes them a challenge to image with. That is why the AO-7 is so important on them.

Get us some pics of the complete set up, I an interested in the new scope too!

#58 Pedestal

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Posted 18 March 2008 - 02:16 PM

Very interesting design, Scott. And looks like it will do the job. How much weight do you think you will have on it?
Hubert

#59 Paula E

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Posted 18 March 2008 - 05:16 PM

It has ~360 pounds on it. I'll try to formulate a much better report, and take some better pictures, this next weekend.

#60 Paula E

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Posted 26 March 2008 - 04:39 PM

Just wanted to give a brief update - sadly, the isolation platform hasn't solved my vibration issues, at least not yet.

I had a friend helping me with the polar alignment of my paramount last weekend, and even at ~150x, it was very obvious at the eyepiece when one of us moved around the dome. At ~250x, even pretty slight movements, like shifting my chair, were pretty evident. The isolation platform dampened out these vibrations rather quickly - but they were still obvious.

I've been talking to Vito at Pier-tech about this, and he thinks stiffer isolation coils may well fix this, so that's what we'll try, I suppose. I agree with his assessment - there is a LOT of weight on this platform, and it's not exactly evenly distributed - its much heavier on the north side of the mount, obviously.. If that doesn't fix the problem, then I guess it'll have to be cutting the floor. (Vito has been extremely helpful throughout this entire process - I can't stress that strongly enough.)

You might be asking yourself the rather obvious question now: "Geeze why doesn't he just cut the dang floor and be done with it?!?"

Well, aside from the horrible, horrible mess that this will create, since I have the dome working quite well right now, I am reluctant to mess with it much. If I have to, I will, but given the fun I had getting it to this point, I don't want to muck with it unless I just have to.

Anyway, I'm 100% sure that mechanical vibrations from the floor of the dome are being transferred rather efficiently into the pier. It would seem that I messed this floor up rather badly! :(

#61 greg

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Posted 27 March 2008 - 02:00 PM

You might be asking yourself the rather obvious question now: "Geeze why doesn't he just cut the dang floor and be done with it?!?"

Well, aside from the horrible, horrible mess that this will create, since I have the dome working quite well right now, I am reluctant to mess with it much. If I have to, I will, but given the fun I had getting it to this point, I don't want to muck with it unless I just have to.

Anyway, I'm 100% sure that mechanical vibrations from the floor of the dome are being transferred rather efficiently into the pier. It would seem that I messed this floor up rather badly! :(


It's good that you have taken the time to diagnose this problem and tried to find an easy way out.... but in the end I suspect you are just going to have to fix it the right way. :O)

I would just get a few rolls of duct tape , a roll of plastic, take an hour or two and build a nice plastic inclosure right out the doorway, also run a strip of plastic around the outside of the dome where it rotates on the walls so no dust that comes out the door can work it's way back into the clean part of the Obs... remove the scope and pier, use a shop vac during, and after your done cutting. Put on a cheap painters suit, tape your ankles, wrists, and neck, use eye protection and a good respirator, and fix this problem...
Most of the fail out should remain in your plastic inclosure, hose down the outside of the Obs, totally clean plastic inclosure, then pull down the plastic inclosure, pull down the outside strip, and clean up should be minimal.

I've had to cut and grind on a lot of fiberglass boats where the fine fiberglass dust had to be contained. Fine fiberglass, like concrete dust, works its way into everything, so spending the time to prep the site pays off during clean up time.

Wish we lived in the same area because I would gladly help you with this project!

I look forward to your progress in solving this problem, and thanks for taking the time and pictures to document your project.

Greg

#62 greg

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Posted 27 March 2008 - 02:21 PM

I almost forgot ....While your at it.... I would cut a 3"X3" trench over close to the pier and move that power closer to the pier where it's supposed to be. I'm sure you can isolate it so it doesn't transfer vibration from the pad to the pier.

I would trip over that thing every night...
:crutch:

:penny: :penny:

Greg

#63 Paula E

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Posted 27 March 2008 - 02:58 PM

Thanks Greg, those are good suggestions. I'll keep the group posted as stuff happens. I suspect it will be a couple of weeks before I have anything else to report. It'll take Vito time to fix up another isolator for me, and I won't be able to make it out to the dome on the weekend of 4/5 because I'm taking my son to visit the college he's going to attend.

#64 Paula E

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Posted 29 March 2008 - 02:48 AM

I'm also going to examine how I mounted my pier this weekend. (At least as best I can without removing the scope and mount.) I begin to wonder if I screwed up something basic - like the pier itself isn't bolted down tightly, and just shakes.

I am finding it difficult to believe I'm having this much trouble on a concrete floor. Sure, it's not isolated - but I could mount this on a wooden deck and have it be this shakey!

#65 Paydirt

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Posted 29 March 2008 - 05:40 AM

Hi Scott if you put a webcam in the scope and view it live from somehwre else (I mean like remote) does the shaking go away? I used to try to observe with my scopes out on a concrete patio and the image shook like crazy no matter how careful I was with every thing. All nuts and faseners done up tight and all. You just cant observe on such a way and not get shaking in the ep. I think chopping your pier away from the slab will fix you problems for sure. Good luck dude thats the coolest set up I think I have ever seen!!!

#66 Pedestal

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Posted 29 March 2008 - 09:02 PM

Scott, probably a silly question, but did you put anything between the pier and the concrete? A piece of wood, for instance?
Hubert

#67 Paula E

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Posted 30 March 2008 - 01:28 PM

Scott, probably a silly question, but did you put anything between the pier and the concrete? A piece of wood, for instance?
Hubert


No, pier bolts down to a metal plate that is inset into the concrete and anchored by j-bolts. The j-bolts screw into the plate, and the tops of them are used to hold up the pier:

Posted Image

#68 Pedestal

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Posted 30 March 2008 - 04:13 PM

Scott, one thing I'd put on my "to do" list would be to grout (with non-shrink grout) the area between the plate set in the 'crete and the plate your pier mounts onto.
Hubert

#69 Manny Myles

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Posted 30 March 2008 - 05:42 PM

Scott K
Out of idle curiousity what type of metal is the base plate in your last picture made of?
m2

#70 Paula E

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Posted 30 March 2008 - 09:19 PM

Scott, one thing I'd put on my "to do" list would be to grout (with non-shrink grout) the area between the plate set in the 'crete and the plate your pier mounts onto.
Hubert


Just to keep crud out from under there, or for some deeper purpose?

#71 Paula E

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Posted 30 March 2008 - 09:20 PM

Scott K
Out of idle curiousity what type of metal is the base plate in your last picture made of?
m2


I believe it's anodized aluminum.

#72 Manny Myles

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Posted 31 March 2008 - 06:10 AM

Thanks for the info on the metal type and this is related to the non shrink grout.
Cement reacts with aluminum so you would have to protect the alum from the grout, not sure if the anodizing would help protect it but I would not take the chance.
What the exact reaction is I'm not sure of but I distinctly remember having to seperate the 2 materials with plastic sheeting to keep the 2 from fighting late at night.
m2

#73 1965healy

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Posted 31 March 2008 - 10:01 AM

Scott, did you ever remove the expansion joint felt from around the pier footer? In your most recent posted photo it looks like it's still in place. Still having vibration issues? Removing that stuff may help a little.

#74 Pedestal

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Posted 31 March 2008 - 10:53 AM

Scott, one thing I'd put on my "to do" list would be to grout (with non-shrink grout) the area between the plate set in the 'crete and the plate your pier mounts onto.
Hubert


Just to keep crud out from under there, or for some deeper purpose?

Mostly to keep moisture out. It also is a vibration dampener. Given Manny's remarks, proceed with some caution-however it already appears to be in contact with the cement, so it may be a moot point. (As an aside, I don't see any great structural purpose in the plate in any case)
Hubert

#75 Paula E

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Posted 31 March 2008 - 02:18 PM

Scott, did you ever remove the expansion joint felt from around the pier footer? In your most recent posted photo it looks like it's still in place. Still having vibration issues? Removing that stuff may help a little.


Yeah, it's still in place, I kind of forgot about it, to tell you the truth. If I remove it, I'll have a 4"-5" deep groove running around the pier plate, like so:

Posted Image

Should I fill that in with caulk? (Well backer rod / caulk, because it's a little deep.) Does the little groove around the pier plate pose any sort of problem? You've basically got 400 lbs or better resting on a 1'x1'x4" deep concrete platform. This is connected to the rest of the concrete forming the pier footer and floor.

Sorry for the stupid questions - I really don't have a background in construction at all.


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