Jump to content

  •  

CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.

Photo

Pier Engineering - Part 2: example

  • Please log in to reply
34 replies to this topic

#1 speedster

speedster

    Viking 1

  • *****
  • topic starter
  • Posts: 860
  • Joined: 13 Aug 2018
  • Loc: Abilene, Texas

Posted 08 July 2019 - 04:58 PM

Howdy All!

 

Since we started the Pier Engineering thread, we've had a lot of private messages asking various questions so I'm posting an example since a pic is worth 1,000 words.

 

Below ground, this pier is 12" diameter, 5' deep and 10" diameter, 4' high, above ground.  The finished pier is nice, shiny, white PVC.

 

In the previous thread, we talked about the importance of pour concrete directly against undisturbed soil and never over-excavating a hole for a spread footing.  Here is the difference in actual numbers:  we have 0.44 arc-sec deflection with #5 lateral load at the top.  If we had not poured against undisturbed soil of the hole, we would have 2.43 arc-sec of deflection under the same load.  This method is much better, faster, and less expensive.

 

For the hole, rent one of these:

 

vsm IMG_2401.jpg

 

$45 for a half day and a 5' hole can be done easily in minutes.  12" auger with a 2' extension gets you to 5' depth.  One trick, when you put the extension on, you can't get the auger all the way out of the hole without wrestling.  The fix is to raise the machine by putting it on car ramps.  When done, 5 minutes cleaning out the bottom with post hole diggers.  No need to dig with them, just pick out the loose material left by the auger.

 

Pour 8" of concrete into the hole then set the rebar cage and press it in to 4" above the bottom of the hole.  This cage is four #3 and stirrups at the bottom, top, and the level of the form.  A stirrup at the level of the form lets you put a stick under it, resting on the form, and hold the height if the 8" at the bottom of pier is not stiff enough yet to support it.  Then, fill the hole, centering the cage as you go and consolidating the mix every 6" by tapping the top with the end of a 2x4.

 

vsm IMG_2402.jpg

 

When you get to the top of the form, put your form over the frame and level it.  Brace the top of it to keep it plumb.

 

vsm IMG_2405.jpg

 

The 2x2's the form is resting on are moved to the very edge of the pipe once it is aligned, shimmed, and plumbed.  This form is 10" schedule 40 PVC and is the finished surface of the pier.  It's wrapped in film to keep the concrete off of it and prevent scratches. 

 

This is the inside of the pier:

 

vsm IMG_2406.jpg

 

There is a 1-1/2" conduit for data and a 3/4" conduit for power.  Both exit the bottom below the floor and then go wherever they need to go.  The top stirrup is placed after the pier is placed and plumbed.  You notice 2 wood blocks on the left side.  These are embedded wood grounds for later attaching power strip etc., with screws.  They are attached with one screw through the pipe and later removed.

Pour the form to 10" below the top of the pipe, drink cold beverage, and I'll continue in the reply below since I'm about at the pic size limit.

 


  • OleCuss, ejd, mosentos and 2 others like this

#2 macdonjh

macdonjh

    Fly Me to the Moon

  • *****
  • Posts: 6,974
  • Joined: 06 Mar 2006

Posted 08 July 2019 - 05:21 PM

Very similar to what I did. 12" diameter for the full length (couldn't find 10" Sonotube), 6 ft below grade, 42" above. Rebar xage is 6 #3 with cyclone fence as the "stirrups". Overkill, I know. Power and data conduit exit the OD of the pier about 24" above the floor and I have project boxes over the conduit ends.

The Sonotube got wet and blew out where I cut holes for the conduit exits. Wrapping with duct tape mostly fixed that. I used a ru bing stone to smooth the face around the conduit later.

#3 speedster

speedster

    Viking 1

  • *****
  • topic starter
  • Posts: 860
  • Joined: 13 Aug 2018
  • Loc: Abilene, Texas

Posted 08 July 2019 - 06:10 PM

Continuing, the top of the concrete is stopped 10" below the top so we can get ready to set the plate and have nice fresh concrete to set it in.  This particular plate is for a CGX-L.  There is no need for a rat cage with its associated deflection.  

 

vsm IMG_2407.jpg

 

vsm IMG_2408.jpg

 

12" x 1/4" steel disc which is plenty stout and nicely trims the top of the pier.  Three 1/2" x 8" galvanized bolts with a deformed washer spot welded to the head to prevent rotation.  Fill the pier to 1-1/2" from the top and press this whole thing all the way down into the concrete until it hits the top of the pipe which should already be level or at least very close.  Check the level of the plate and use narrow shims to get it spot on.  Wood shims will be too thick if you've been careful so have some thin metal shims handy.  This one needed one thickness of Coke can in one spot to get it right.

 

The plate is $12 on Ebay and $20 to have a machine shop mill the holes in it.  Since it is installed level, it should need to further adjustment but, if it does, each bolt has 2 nuts below the plate.  These nuts are tightened against each other to make a stop that can be raised and the nut on top of the plate then tightens the plate against these stops.  We hold the top of the concrete 1-1/2" below the top of the pipe so the nuts can be accessed in case adjustment is needed.  

 

The is no adjustment for North.  The mount has a good deal of adjustment and the plate is set quite accurately.  A night after the hole is dug but before concrete is poured, set an alt-az mount directly over the hole, center Polaris, slew directly down until you can put a mark on some thing visible during the day.  In this case, we put a screw in a fence about 60' away.  When you set the plate in the wet concrete, aim it at the mark.  This plate has a N-S line scratched in it.  Sight down the line to the screw in the fence.  Your plate is now level and polar aligned.

 

This plate is specific to CGX and CGX-L mounts but the principle can be applied to others.  These are very stout and very simple to make.  Cut 3 little clip angles and drill slightly oversize holes for the mounting bolts.  Put a bolt through a mount hole and through a clip angle.  Thread a nut on the inside and tighten it up so the angle is flush with the bottom of the mount.  Dab a little JB Weld to attach the nut to the back of the clip angle.  Repeat for the other two mount bolts.  Then spread a little JB Weld on the bottom of the clip angles and set the mount, with clips attached, on the plate, centered and pointing north.  Next day, take the bolts out and lift the mount off.  Nuts are stuck to the clips and clips are stuck to the plate with JB Weld.  Weld the nuts to the clips and then weld the clips to the plate. 

 

So, we are left with this:

 

vsm IMG_2410.jpg

 

Leave it a week.  Then we'll remove the forms and remove the plate for painting.

 

The CGX-L does not come with a tripod.  Why drop $600 on a tripod when it's going on a pier?  But, if you make the holes for the 1/2" embedded bolts on the same pattern as your favorite tripod, you can pull the mount and plate off the pier and put them on the tripod.  This is not exactly a traveling mount but, if someone invites me to spend a month in Tuscon (hint, hint), I can take it if I want to.

 

Let's compare:

 

Concrete $63

Rebar $20

Bolts $12

Steel disc $12

Fabrication $30

10" PVC $90

Auger rental $40

Misc $33

TOTAL = $300, deflection 0.44 arc-sec

 

Compared to equivalent steel pier:

 

5' concrete pier in the ground $112

8" x 48" steel pier with equivalent deflection $800

Pier plate adapter $400

 

Certainly nothing wrong at all wrong with the steel pier scenario.  It's just $1000 dollars more for the same deflection.

 

 



#4 karambit27

karambit27

    Viking 1

  • *****
  • Posts: 883
  • Joined: 15 Aug 2013
  • Loc: Rochester, NY

Posted 09 July 2019 - 04:14 PM

Great thread. Thanks for posting. I can't seem to figure out a why to avoid a rat cage unfortunately. A 12" pier doesn't allow me to space the anchor bolts far enough apart to fit my mounts base plate within the bolt pattern while not having the bolts too close to the edge of the pier. The only solution seems to be mount a plate directly to the top of the pier and then a second plate that I can space the bolts far enough apart between the plates on to fit the base plate. I would keep the bolts between the plates as short as possible to just clear the anchor bolts. My base plate also attaches to the mount from the bottom of the plate so that access is required as well. My mount's base plate is 260mm or roughly 10.25 inches in diameter.



#5 nimitz69

nimitz69

    Mercury-Atlas

  • *****
  • Posts: 2,819
  • Joined: 21 Apr 2017
  • Loc: A barrier island 18 miles south of Cocoa Beach

Posted 09 July 2019 - 08:56 PM

My mount (EQ6-R Pro) also attaches with a center bolt from below but the solution is easy ... see my observatory build thread - DarK Matter Observatory build.  Basically I’ve drawn up a base plate that copies what the base plate of they mount looks like for the tripod. Then on the underside of the plate I’ve simply  included a recessed hole so that after bolting the plate to the mount it will still sit flush with the pier cap plate and you simply bolt the 2 together ... I’ve put some pics in the thread.

thhere are a bunch of CNC machine shops online that can mill the plate for you at relatively low cost.  No need to ever use the rat cage Design again ....



#6 speedster

speedster

    Viking 1

  • *****
  • topic starter
  • Posts: 860
  • Joined: 13 Aug 2018
  • Loc: Abilene, Texas

Posted 09 July 2019 - 10:51 PM

You can do a single plate for mounts with a center bolt.  Bolt the mount to the plate and then bolt the plate to the pier.  Bolt pattern for the pier bolts just have to be just enough outside the mount to get a wrench on them. 

 

You can also make a rigid spacer to access bolts.  This one connects a wedge to a pier.  It's 2 plates welded to a 4" x 4" x 1-1/5" steel tee.  Cables feed through the side of the tee and down through a conduit in the pier

 

IMG_2394 sm.jpg

 

The bottom plate has a 2" hole in it for passing cable.  The top plate has the 3 holes for the wedge and also a center hole for a mount that uses a center bolt.  For that style mount, you would bolt the unit to the mount through the 2" bottom hole using a ratchet with an extension.  Then bolt the unit to the pier.


Edited by speedster, 09 July 2019 - 10:57 PM.


#7 karambit27

karambit27

    Viking 1

  • *****
  • Posts: 883
  • Joined: 15 Aug 2013
  • Loc: Rochester, NY

Posted 10 July 2019 - 02:22 PM

Thanks. Luckily my neighbors actually run a machine shop that has CNC Mills and lathes so I am just going to have them work everything up for me. The plan is to put a recess in both plates to fit over the nuts and washer securing the bottom plate to the pier. Then the top plate then sits flush on the bottom plate and has plenty of surface to mount to and I can secure it in each corner via a knob with 3/8" bolt for easy tool less removal. As for the center bolt I will just thread the center hole of the plates and bolt it from the top. There's really no need to have the bolt underneath. The tiny part of the bolt head sticking up won't get in the way of anything.


Edited by karambit27, 10 July 2019 - 02:24 PM.


#8 nimitz69

nimitz69

    Mercury-Atlas

  • *****
  • Posts: 2,819
  • Joined: 21 Apr 2017
  • Loc: A barrier island 18 miles south of Cocoa Beach

Posted 10 July 2019 - 02:43 PM

pretty much what I'm doing as well ... the below pic is a wood mockup of the mount plate.  you bolt the plate to the scope mount via the hole in the center from underneath and then the outside holes on the plate are positioned to line up with the bolts sticking up from the pier top plate & you simply bolt them together, there is a recess in the mount plate so the 2 sit flush ... you can ignore the hole positions in the mockup as I was experimenting with different ideas.  my final design has 4 holes evenly spaced 2" from the edge of the pier ...

 

mount to pier plate1.jpg

 

 

 



#9 markm75c

markm75c

    Viking 1

  • *****
  • Posts: 960
  • Joined: 17 Sep 2009
  • Loc: Pittsburgh, PA

Posted 15 July 2019 - 02:40 PM

For the jigs to set the j bolts into the concrete, is everyone using 1/2" sheathing plywood, cut to the right shape/size?

 

What about the j bolts, looking at the lowes site i'm not sure what i'm looking for, 8" long 3/4" etc?

 

I tried looking for PVC at the big box stores like lowes, they only seem to stock 20 footers in the $350 range, nothing around 4 feet for $100 unfortunately, so i guess i may have to try to get away with a sonotube and route the pvc inside it for the wiring and data, assuming i dont run into the cardboard tearing issue.



#10 nimitz69

nimitz69

    Mercury-Atlas

  • *****
  • Posts: 2,819
  • Joined: 21 Apr 2017
  • Loc: A barrier island 18 miles south of Cocoa Beach

Posted 16 July 2019 - 07:48 PM

I liked the PVC idea but also couldn’t find anything for under $250 since you had to buy 20’ min.  I just ended up going with a sonatube.  The J bolts I’m using are actually called anchor bolts at lowes ... 10” long & 1/2” diameter.  I’m using the actual 10” dia 1/4” steel plate that will be mounted on the top of the pier for aligning the bolts.  Then my ‘mount to pier’ plate gets bolted onto that.  Many use a wood template but why not use the actual piece of steel that the bolts will mount to ...


Edited by nimitz69, 16 July 2019 - 07:49 PM.


#11 speedster

speedster

    Viking 1

  • *****
  • topic starter
  • Posts: 860
  • Joined: 13 Aug 2018
  • Loc: Abilene, Texas

Posted 16 July 2019 - 07:59 PM

hunt online for cut lengths of PVC.  https://www.rainharv...s0aAgpuEALw_wcB

 

If you have the actual steel plate, definitely use it for placing bolts in concrete.



#12 markm75c

markm75c

    Viking 1

  • *****
  • Posts: 960
  • Joined: 17 Sep 2009
  • Loc: Pittsburgh, PA

Posted 18 July 2019 - 11:20 AM

Silly question, but for the electrical wire that will go in the pier, does it have to be "electrical pvc conduit", ie: the gray stuff, i assume it does right and for in ground?



#13 speedster

speedster

    Viking 1

  • *****
  • topic starter
  • Posts: 860
  • Joined: 13 Aug 2018
  • Loc: Abilene, Texas

Posted 18 July 2019 - 12:28 PM

If there is an electrical inspector involved, the electrical stuff must be grey PVC conduit.  Otherwise, white PVC plumbing pipe works for conduit.  The differences between the two:  white is certified by NSF, grey is certified by UL, white cannot be exposed to UV, grey can be exposed to UV, white is pressure rated, grey is not.  Grey is stiffer and stronger but may contain additives not allowed in water piping so don't use grey for domestic water.



#14 Stevegeo

Stevegeo

    Apollo

  • *****
  • Posts: 1,120
  • Joined: 29 Jan 2019
  • Loc: Otisco lake. Marietta NY 13110

Posted 19 July 2019 - 08:33 PM

I'm following this thread closely as I am in the process of a new pier and pad for my observatory ..

 

I have a top plate made from a Smart car rotor,which  has three holes, 10in dia,  is about 16mm thick ,machinable and weldable .Another rotor on top of that,for alignment then drilled and tapped into the other the mount will attach to this with welded blocks.  I do this because down the road I may upgrade my scope of mount or both . Rotors are cheap , and very precise in run-out. I can level the top using the threaded jack screws. 

I like the ideas of conduit for cables . I am doing the same   , since my building already has a hole for the pier  dead center

I have only a few choices in doing a 4 ft pier inside my building...first would be make the pier stop flush with floor and add a filled steel pipe pier bolted to that...or finish the pier 4 ft  concrete, lift the building over it ..do able ..but great effort . Or cut a slot in the building and slide in place... very do able but again a lot of effort . The siding will have to come off  and plywood cut. A simple and easy alternative.

I do this because I am logging off more to South and east  taking out about 60 plus large trees over 90 ft tall . For a better view! Other thoughts since I'm moving my observatory , is a larger pad for a warm/storage room,  and maybe blocking the entire building a few feet off the pad .



#15 markm75c

markm75c

    Viking 1

  • *****
  • Posts: 960
  • Joined: 17 Sep 2009
  • Loc: Pittsburgh, PA

Posted 26 July 2019 - 07:10 AM

Another question on the pvc inside the pier

 

In my case as you know i reduced to a 10" width pvc pier.  Is 1.5" for the data and 3/4" for the power is still ok going down the middle (along with a 4 or 3 rebar cage), or is this taking up too much room being as i lost 2" in width?

 

I'm curious too, for the data pipe, have you ever tried to fish through display port or hdmi cables, i'd have to imagine even with that size that maybe the heads would get stuck or wouldnt fit, but something i was pondering as i'm thinking ill put a mini pc on the pvc tube.

 

Then the secondary question, i know you put a block behind the pvc to screw into, but is it really needed, couldnt you just screw directly into the pvc with just concrete behind, or maybe not since there might only be 1/2" of pvc to screw into b4 concrete?  Debating whether i should attach a piece of plywood to act as a way to hold things like the pc and other things on the side vs directly on the pvc, unless i just make the plywood sit on the floor and circle cut two pieces to go "around" the tube almost like clamps, unsure.  Thinking ahead anyway.

 

EDIT: i guess i could also skip the internal pipes altogether, many seem to prefer wires on the outside even tied to the pier, easier to get to when issues.

 

 

**The other question is on the framing for the footer.  Should that be sunk into the ground?  I'm thinking of only having a 2" footer (then the pvc either sunk into the footer 1" or just meeting it at the top during the pour), so this sounds like 4, 2x2s in a frame to me, but i'm not sure if maybe i should just use 3/4 plywood and sink 1" into the ground and seal off the corners somehow?

 

Likely pour is finally next weekend roughly.


Edited by markm75c, 26 July 2019 - 10:57 AM.


#16 nimitz69

nimitz69

    Mercury-Atlas

  • *****
  • Posts: 2,819
  • Joined: 21 Apr 2017
  • Loc: A barrier island 18 miles south of Cocoa Beach

Posted 26 July 2019 - 08:37 PM

I’m not going with any internal pvc inside the pier for wiring,  too much effort and I only have two cables that run off my rig anyway - one is a from my USB hub to my computer and the other is from my RigRunner to my DC/AC inverter box which plugs into a std wall outlet.  I’ll just attach them to the outside of the pier and if I ever need to change anything its easy.

 

if you want a 2” thick footer at the point where the concrete comes out of the ground 2x4 are the answer.  They are 3.5” high so you can easily secure them in the ground 1.5” & then get 2”of concrete above ground.  I built a 14” x 14” square 2x4 frame today which will do the same thing and form a nice solid base between underground & above ground concrete. I’m digging holes tomorrow & pouring concrete on Sunday ...


  • markm75c likes this

#17 markm75c

markm75c

    Viking 1

  • *****
  • Posts: 960
  • Joined: 17 Sep 2009
  • Loc: Pittsburgh, PA

Posted 27 July 2019 - 11:40 PM

I’m not going with any internal pvc inside the pier for wiring,  too much effort and I only have two cables that run off my rig anyway - one is a from my USB hub to my computer and the other is from my RigRunner to my DC/AC inverter box which plugs into a std wall outlet.  I’ll just attach them to the outside of the pier and if I ever need to change anything its easy.

 

if you want a 2” thick footer at the point where the concrete comes out of the ground 2x4 are the answer.  They are 3.5” high so you can easily secure them in the ground 1.5” & then get 2”of concrete above ground.  I built a 14” x 14” square 2x4 frame today which will do the same thing and form a nice solid base between underground & above ground concrete. I’m digging holes tomorrow & pouring concrete on Sunday ...

Good luck on your pour.

 

Yeah thats true the 2x4s should be perfect.  Once my lower plate is fabricated i should be good to go.  (i still cant decide on how high i'm making the ra/dec center point though, keep wavering, 53" is the wall and recommended spot but i keep feeling like for longer scopes someday maybe, going lower is a better idea, whole side topic).  So i need to decide on where to cut this 10" pvc pipe i have.

 

How are you doing the supports for the pvc?  Do you think its ok to screw 2x4's into the pvc as braces?  Will you have yours just barely touching the footer after you pour the footer?  Are you then just moving it in place, barely touching and pouring.

 

I also am unsure if i should have an 8 foot rebar cage from the bottom to the pvc pipe, or just put rebar to the top of the ground 2x4 frame and then have a second cage in the pvc



#18 nimitz69

nimitz69

    Mercury-Atlas

  • *****
  • Posts: 2,819
  • Joined: 21 Apr 2017
  • Loc: A barrier island 18 miles south of Cocoa Beach

Posted 28 July 2019 - 01:16 PM

I don’t see why you can screw the braces to the pvc.  How long a piece of 10” pvc do you have?  I couldn’t find anything except 12” diameter which I can’t use.  Where did you find it?  I was just going to use a sonatube.  My plan was to sit my rebar cage in the hole and pour concrete until I fill it and the footer. Then i’ll Put the sonatube over the rebar cage sitting on top of the footer and brace it with 2x4 making in plumb, then fill the rest of the tube, then set in my 4 anchor bolts using a template...  if necessary I may attach a 1x2 to the bottom of the tube sitting across the form to keep it from sinking into the concrete.  The Cardboard tube doesn’t weigh anything so it will probably not need it but the PVC tube might .  I made one single rebar cage that runs the entire length.  Once you set it in the hole and get some concrete around it it should be pretty stable and easy to keep centered



#19 markm75c

markm75c

    Viking 1

  • *****
  • Posts: 960
  • Joined: 17 Sep 2009
  • Loc: Pittsburgh, PA

Posted 28 July 2019 - 10:17 PM

I don’t see why you can screw the braces to the pvc.  How long a piece of 10” pvc do you have?  I couldn’t find anything except 12” diameter which I can’t use.  Where did you find it?  I was just going to use a sonatube.  My plan was to sit my rebar cage in the hole and pour concrete until I fill it and the footer. Then i’ll Put the sonatube over the rebar cage sitting on top of the footer and brace it with 2x4 making in plumb, then fill the rest of the tube, then set in my 4 anchor bolts using a template...  if necessary I may attach a 1x2 to the bottom of the tube sitting across the form to keep it from sinking into the concrete.  The Cardboard tube doesn’t weigh anything so it will probably not need it but the PVC tube might .  I made one single rebar cage that runs the entire length.  Once you set it in the hole and get some concrete around it it should be pretty stable and easy to keep centered

I got a 60" long pvc, ill probably cut it around 50" (10 inch below deck to the surface of this frame, which now sits really only 1" above the soil if that after doing it).. above deck roughly 39.5 targeted to reach 53" for the wall height of the nexdome (also the ra/dec intersection axis with scope on side/cw horizontal above floor).

 

I found the pvc at a local pipe and supply company, although i did find a source online here I almost used (online was around $130 shipped and local $65)

 

Yeah that will be my goal then, as noted in this thread, one long rebar cage.  Ill put some gravel, maybe 1/2" or 1" in the bottom of the hole.  I havent decided if ill try even a data pvc through the main 10" pvc yet or not, i'm leaning towards no and just strapping any power/data on the sides of the pvc.

 

Ill need to figure out why spray paint to use to spray it black when done though.

 

Here is a frame shot, as you can see its off center.  I could add another 2x4 on the right to center it, but concrete will still be there under the 2x4 because there isnt much wall on that side.  I guess ill have an off center (visually from above) pvc pipe, only i will know that, flooring over the footer.  If i move the whole frame, the right side most likely wont sit above anything but air, so kinda pointless doing that.

 

frameabove.jpg


  • kathyastro likes this

#20 nimitz69

nimitz69

    Mercury-Atlas

  • *****
  • Posts: 2,819
  • Joined: 21 Apr 2017
  • Loc: A barrier island 18 miles south of Cocoa Beach

Posted 29 July 2019 - 04:50 PM

Why it just make the form bigger?  I made mine 32” square surrounding the hole ... don’t forget to coat the inside of the 2x4s with something like a varnish or like coat on oil to make removing the form a little easier and don’t remove it until 24 - 48 hrs after the pour.



#21 markm75c

markm75c

    Viking 1

  • *****
  • Posts: 960
  • Joined: 17 Sep 2009
  • Loc: Pittsburgh, PA

Posted 31 July 2019 - 09:32 PM

Why it just make the form bigger?  I made mine 32” square surrounding the hole ... don’t forget to coat the inside of the 2x4s with something like a varnish or like coat on oil to make removing the form a little easier and don’t remove it until 24 - 48 hrs after the pour.


The right side of about 2.5" or more is actually just a wall of dirt, so technically i should just throw the 2x4 in there and itll be fine (hard to tell in the pic). Thanks for the tip on the oil.

I began making the bracing structure tonight. Ill add diagonals to hold the top, also made a square for the top.

What i cant quite do is cut the rebar. I thought maybe my band saw could do it, but no, dumb idea. Ill have to wait on my contractor relative to cut them to the right lengths and tie it all together. As of now Sat the 10th is pour date.

The other thing is the tube.. im not sure if i can make a symmetrical circle cut, because both the top and bottom are uneven, so i cant mark it all the way around evenly.

I dont know if this is bad to do but i'm leaving 3/4" in the concrete as seen here, where i've used 3/4 plywood to create a 3/4" high bottom on it:
bracetube.jpg

 

I guess ill just put one screw (3" deck screw) into each side on each brace into the pvc and tube.  I assume it should just unscrew whenever the concrete dries (and not get trapped in the concrete).


Edited by markm75c, 31 July 2019 - 09:33 PM.


#22 speedster

speedster

    Viking 1

  • *****
  • topic starter
  • Posts: 860
  • Joined: 13 Aug 2018
  • Loc: Abilene, Texas

Posted 31 July 2019 - 11:47 PM

Howdy Mark!

 

Screws WILL get trapped in the concrete.  No need to screw into the tube.  Pour up to the tube level, set your 2x4 frame if you haven't already, the set the tube through the frame to the concrete.  It may sink in a  half inch and that is OK.

 

If you leave the top box a little big, you can shim it to plumb once the bottom of the tube is set in the bottom frame.

 

Cut rebar with a metal blade in a sawzall, or with a grinder. 

 

Center the bottom box on the pier hole.  Don't worry about a void under part of it - concrete will fill the void.

 

No need to paint or oil any forms.  The 2x4 just holes the pipe.  The pipe is the form. 

 

To get a perfect mark around your tube:  take a piece of paper about 24" x 36" (perimeter of 10" pipe is 33") .  This can be any paper with a good edge.  Gift wrapping paper works fine. Wrap the paper around the tube and make the top edge of the paper meet where it overlaps around the tube.  Mark the top edge and  you'll have a line exactly perpendicular to the axis of the pipe.  If that doesn't make sense, let me know and I'll see about taking a pic.  Try it first - I think you'll see the magic as soon as you wrap the paper around the pipe.


  • markm75c likes this

#23 markm75c

markm75c

    Viking 1

  • *****
  • Posts: 960
  • Joined: 17 Sep 2009
  • Loc: Pittsburgh, PA

Posted 01 August 2019 - 09:44 AM

Howdy Mark!

 

Screws WILL get trapped in the concrete.  No need to screw into the tube.  Pour up to the tube level, set your 2x4 frame if you haven't already, the set the tube through the frame to the concrete.  It may sink in a  half inch and that is OK.

 

If you leave the top box a little big, you can shim it to plumb once the bottom of the tube is set in the bottom frame.

 

Cut rebar with a metal blade in a sawzall, or with a grinder. 

 

Center the bottom box on the pier hole.  Don't worry about a void under part of it - concrete will fill the void.

 

No need to paint or oil any forms.  The 2x4 just holes the pipe.  The pipe is the form. 

 

To get a perfect mark around your tube:  take a piece of paper about 24" x 36" (perimeter of 10" pipe is 33") .  This can be any paper with a good edge.  Gift wrapping paper works fine. Wrap the paper around the tube and make the top edge of the paper meet where it overlaps around the tube.  Mark the top edge and  you'll have a line exactly perpendicular to the axis of the pipe.  If that doesn't make sense, let me know and I'll see about taking a pic.  Try it first - I think you'll see the magic as soon as you wrap the paper around the pipe.

Brilliant, i hadnt thought of the wrapping paper idea.  I'll definitely do that.

 

I guess in your example above, you had put a piece of wood under the tube when placed on the footer area, in my case, i just assumed i'd sink it 3/4" (i need to get an exact height, so i can hit 53" above the deck with the pipe plus mount etc), i have 12" to the frame from the top of the deck in my measurement, so i've adjusted for 3/4" below that to know where to cut the pipe.

 

So in your case if you just let it sit directly on the concrete it only "fall in" about 1/2" ?  Wouldnt i be just as well to screw the wood box i have at the bottom into the pvc, but Not go into the void of the pipe, just into the plastic pvc part to act as an anchor, that way no screws get trapped and the whole thing can hover with 3/4 of it to be in the footer?  (thanks for pointing out fully screwing into the tube the whole way would result in a stuck screw)



#24 nimitz69

nimitz69

    Mercury-Atlas

  • *****
  • Posts: 2,819
  • Joined: 21 Apr 2017
  • Loc: A barrier island 18 miles south of Cocoa Beach

Posted 01 August 2019 - 06:32 PM


"No need to paint or oil any forms.  The 2x4 just holes the pipe.  The pipe is the form"

 

 

In post #19 the pic shows a rectangular form around the hole which appears he his going to have as a square footing between the above ground & below ground portions of the pier; since that would be filled with concrete, coating the inside of the form would make it easier to remove.  If its just a straight column and the 2x4s are just braces then I agree no coatings are required ...


Edited by nimitz69, 01 August 2019 - 06:32 PM.


#25 markm75c

markm75c

    Viking 1

  • *****
  • Posts: 960
  • Joined: 17 Sep 2009
  • Loc: Pittsburgh, PA

Posted 09 August 2019 - 09:47 AM

Here is my concrete prep update (pouring tomorrow):
 
After using this thread and a combination of others ideas ended up doing the rebar cage twice till i think i have it right.  On rev 2 i went with an $8 roll of galvanized chicken wire from lowes to use to hold it together plus rebar cross bars.
 
But, to also aid things, i initially pounded all 4 stakes into the ground inside a box so i could measure out the distances and set cross bars in addition.
 
Here is what that looked like:
rebarprep.jpg
 
I set the distance between the bars at around 4.5", this way I will be able to get a 2x4 down in there to mix up the concrete as its poured to prevent bubbles and air.
 
I ended up using both the rebar for holding it together and chickenwire:
rebarcage.jpg
 
I placed the 10" pvc frame that i made around the hole in the deck (the top wood i can attach 2x4s to the ones at the ground for support, though frankly i dont think they will be needed), i also only went into the pvc with deck screws but only to the point of just getting them into the pvc wall, not much on the inside:

pvcvertical.jpg
 
The bottom of the pvc pipe will be submerged 3/4" into the concrete footer.
 
I also added gravel to the bottom then used wire rebar holders and placed 2 rebar in the holders allowing for the center to come down the middle (i might need to add more gravel unsure).
**My concern here is that the horizontal ends of at least 1 or 2 of the end points are lightly touching the soil, which probably should be avoided, but maybe will be fine.  I'm also not sure if there is enough rebar in the footer, but i guess some is better than none or maybe i could toss a few bars in every few feet as it fills?
pierlowerrebar.jpg
 
I then moved the platform over the hole, centering it as best i can and lowered the rebar cage down in.
It works out to around 1.75" or more between the rebar and the sides of the pvc.  I have about 9" of jbolt that will be into the concrete which will end up just above the rebar cage.
cageintube.jpg
cageinhole.jpg
 
 
*When they do the pour, i'm unsure if they can shoot the chute directly over the pvc and pour from there down, first filling the footer then on up, or maybe start at the edges of the tube into footer directly, get it level then move up to the pvc?
 

Later I will use 220 grit sandpaper over the pvc, then an acetone wipe down, then Krylon Fusion Matte Black spray paint (2 coats) to paint it.
 
I'm unsure on when it would be safe to put the full mount and weight on the pvc pipe after the pour, but i think 2 weeks might be how long i will wait.  I know speedster mentioned 1 week previously, but is that 1 week then weight?  I've read online that it can actually take 28 days or more for it to fully cure?




CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.


Recent Topics






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics