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CEM120 Concrete Pier suggestions or steel only?

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#1 markm75c

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Posted 11 July 2019 - 09:18 PM

I wasnt sure if this should go under observatories or mounts..

I've decided on the cem120 for my nexdome build, but the next step for me is creating the concrete pier.

I'm not sure that a 10 or even 12" concrete pier would work well given the bottom of the mount's design: (appears to be 8.26 squared)

a88de34e5aa9f5fe9b52cc4257af4fab0bfb2114

 

I think it was suggested that only a steel pier with square plates on top might work (i was hoping to just go the sonotube route)

 

So i'm asking if anyone with the cem120 on a pier has done concrete and how did you go about securing it to the top?

 

Thanks in advance


Edited by markm75c, 11 July 2019 - 09:18 PM.


#2 DuncanM

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Posted 11 July 2019 - 09:55 PM

I wasnt sure if this should go under observatories or mounts..

I've decided on the cem120 for my nexdome build, but the next step for me is creating the concrete pier.

I'm not sure that a 10 or even 12" concrete pier would work well given the bottom of the mount's design: (appears to be 8.26 squared)

a88de34e5aa9f5fe9b52cc4257af4fab0bfb2114

 

I think it was suggested that only a steel pier with square plates on top might work (i was hoping to just go the sonotube route)

 

So i'm asking if anyone with the cem120 on a pier has done concrete and how did you go about securing it to the top?

 

Thanks in advance

 

You pour your pier and then set J bolts into the cement and bolt a circular aluminum or steel plate to the j-bolts, with an inch or two of clearance between the plate and pier top. Then drill four holes in the plate to match the CEM120 bottom plate and bolt it onto the plate. 10in sonotube has a diameter of 254mm. You can have a circular plate with four evenly spaced 10mm j-bolts  at 115mm from the centre. The CEM120 bottom plate will then sit on the plate inside the 4 j-bolt attachment points and can then be bolted into place. Designing the circular plate with a 10in sonotube is tight but 12in tube is no problem at all.



#3 Chuckwagon

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Posted 12 July 2019 - 12:01 AM

Use a 12" tube and a 12" adapter plate.  If you want the square base to be inside the diameter of the pier (no pointy edges poking out) it needs to be 12".  The diagonal of the base plate you showed is 296.98mm, and the diameter of a 12" circle is 304.8mm.  Just about perfect.  :)



#4 amoncayo

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Posted 12 July 2019 - 12:02 AM

Hi,

 

When I built my sonotube concrete pier, I chose 12" diameter. I built it before I had my CEM120 and had an Atlas EQ-G on it using a plate from Dan's (http://www.pierplates.com/). When I bought the 120, I also ordered iOptron's pier adapter plate. It was drop-shipped to Dan and he drilled/tapped appropriate holes to allow is to mount onto the original plate that came with the EQ-G plate adapter. Aside from raising the mount a bit over an inch, I have not noticed any penalty in stability, etc. while using the mount with the extra plate.

 

My concrete pier had only 3x 5/8" J-bolts installed in it. I used a plywood template/form to level and hold the J-bolts in place until the concrete cured. I placed them at even 120 degree separation on a 4" radius.

 

Al

 


So i'm asking if anyone with the cem120 on a pier has done concrete and how did you go about securing it to the top?

 

Thanks in advance



#5 kisstek

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Posted 12 July 2019 - 12:16 AM

Look at the photos in the other pier thread that just got started:

 

https://www.cloudyni...x/#entry9494402

 

He uses a steel tube for the pier but you could use concrete instead. If you use a steel tube, filled it with sand or concrete to keep it from ringing like a bell.

 

Whichever you choose, use a double plate design as the adapter for the CEM120. Note that the bolt holes for attaching the CEM120 to the plate are not the same bolt holes that attach the plate to the top of the pier. That allows you to adapt to whatever size column you decide on. It also allows you to change the top plate when you get the next mount. Or the mount of the astronomer who buys your house because you already have an observatory.

 

I urge you to plan ahead for change.



#6 dapalmer

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Posted 14 July 2019 - 09:28 AM

You can make a wooden template and drill some holes in the same hole pattern as your mount base plate. The template needs to be bigger than the sonotube so that it can rest on top of the tube. After pouring the concrete, insert your L - bolts in the desired pattern using the template as a guide. You can use a few washers as spacers at the edge of the sonotube to keep the template slightly above the concrete so it is easier to remove or make the template big enough that you can tap it off with a hammer. Be sure and smooth  the top of the concrete with a trowel before lower the template for final set.



#7 CharlesW

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Posted 14 July 2019 - 10:45 AM

Pour an 18” diameter pedestal about 6” above your floor level. Figure out how tall your pier needs to be. Software Bisque makes the best 10” steel pier for the money, about $650, up to 48”. They will also make custom piers but the lead times are a little longer.



#8 markm75c

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Posted 14 July 2019 - 11:36 PM

Use a 12" tube and a 12" adapter plate.  If you want the square base to be inside the diameter of the pier (no pointy edges poking out) it needs to be 12".  The diagonal of the base plate you showed is 296.98mm, and the diameter of a 12" circle is 304.8mm.  Just about perfect.  smile.gif


My biggest issue is finding the "plate" material. I see many are using I think 0.25" thick or maybe 0.5 inch thick? aluminium, but are finding it at random places. I suppose if i cant find a source locally i should just try some ebay or amazon sources.

I think there needs to be at least 2 inches clearance from the J bolts to the edge of the 12" adapter/cement to prevent issues. So not only is this cem120 mount square, about 8.25x8.25, but now i have to have the holes beyond this area for the jbolts and still have 2" from the edge, i guess its all doable, maybe 1" over on the template make the holes for the bolts, making sure i leave 2" from the edge.. of course all this once i find the metal material

Its holding up the show on pouring concrete etc.

You can make a wooden template and drill some holes in the same hole pattern as your mount base plate. The template needs to be bigger than the sonotube so that it can rest on top of the tube. After pouring the concrete, insert your L - bolts in the desired pattern using the template as a guide. You can use a few washers as spacers at the edge of the sonotube to keep the template slightly above the concrete so it is easier to remove or make the template big enough that you can tap it off with a hammer. Be sure and smooth  the top of the concrete with a trowel before lower the template for final set.


I guess i could cut a 13 or 14" disc and draw a 12" circle on it, then draw by hand the mount template in the center, then pick 4? random spots on the perimeter for the jbolts and i'd be ready to pour (leaving about 2" space between the wood and the 12" pvc pipe?)

Edited by markm75c, 14 July 2019 - 11:36 PM.


#9 markm75c

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Posted 14 July 2019 - 11:38 PM

Pour an 18” diameter pedestal about 6” above your floor level. Figure out how tall your pier needs to be. Software Bisque makes the best 10” steel pier for the money, about $650, up to 48”. They will also make custom piers but the lead times are a little longer.


I've considered the steel pier route. I'm trying to save a little cash by just using a sonotube or $100 12" pvc pipe (which ill run electrical and data down through and out).

Most of the software bisque piers i saw were for different mounts?

The ioptron ones though, those seems to be about $480 which isnt bad.

Either way, i would have to make a jig for the template of this pier would i not, before pouring the concrete if i went that route (or masonry bits and bolts later but i'm nervous about that).

#10 markm75c

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Posted 14 July 2019 - 11:39 PM

I'm concerned too about not already having the cem120 mount in hand, as i dont know if its mount plate is smooth on the bottom or if it will need any holes riveted or shaped differently. Hoping for some cem120 user input on that or maybe a real picture of the base plate on the cem120 would be great.

I suppose in that scenario worst case i'd just have to get new metal and redrill, since the jbolts would already be sticking out of the cement pier at that point (or for changing mounts later if i did). (One plate solution)

#11 DuncanM

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Posted 14 July 2019 - 11:44 PM

I'm concerned too about not already having the cem120 mount in hand, as i dont know if its mount plate is smooth on the bottom or if it will need any holes riveted or shaped differently. Hoping for some cem120 user input on that or maybe a real picture of the base plate on the cem120 would be great.

I suppose in that scenario worst case i'd just have to get new metal and redrill, since the jbolts would already be sticking out of the cement pier at that point (or for changing mounts later if i did). (One plate solution)

The CEM120 baseplate is smooth and you can use the iOptron template as it's very accurate. Other than placing the four bolt holes in your mounting plate, you only have to worry about leaving enough clearance for the CW shaft but that shouldn't be a concern for your latitude.



#12 markm75c

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Posted 14 July 2019 - 11:51 PM

The CEM120 baseplate is smooth and you can use the iOptron template as it's very accurate. Other than placing the four bolt holes in your mounting plate, you only have to worry about leaving enough clearance for the CW shaft but that shouldn't be a concern for your latitude.


Ah yes when you say clearance for the CW shaft (i havent done gems yet), you mean so it doesnt strike the pier? Any idea how i would simulate that without the mount in front of me or be sure? I didnt want a huge rat cage space on the top of the pier, like 2", but if that was cutting it close, i assume it means i extend this space between pier and plate?

Does placement of the 4 bolts matter on the plywood jig, just pick 4 corners of the circle basically (2" from edge and not into the square of the mount template)?

Seems easy enough so far.

#13 Chuckwagon

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Posted 15 July 2019 - 01:38 AM

My biggest issue is finding the "plate" material. I see many are using I think 0.25" thick or maybe 0.5 inch thick? aluminium, but are finding it at random places. I suppose if i cant find a source locally i should just try some ebay or amazon sources.

Have you looked at Dan's Pier Top Plates?  I'd bet Dan would be willing to work with you to get you something that would work with the 120.

 

Also, look at what Rainer (Real14) has done with his 120's.  https://www.cloudyni...0ec2/?p=8748466

 

There are many ways to get a good setup for your mount.  :)



#14 DuncanM

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Posted 15 July 2019 - 02:47 AM

Ah yes when you say clearance for the CW shaft (i havent done gems yet), you mean so it doesnt strike the pier? Any idea how i would simulate that without the mount in front of me or be sure? I didnt want a huge rat cage space on the top of the pier, like 2", but if that was cutting it close, i assume it means i extend this space between pier and plate?

Does placement of the 4 bolts matter on the plywood jig, just pick 4 corners of the circle basically (2" from edge and not into the square of the mount template)?

Seems easy enough so far.

Page 22 of the manual has a side view of the mount, and you can get a good idea of the clearance needed for the CW shaft:

 

http://www.ioptron.c...Instruction.pdf

 

for your latitude.

 

The height of the rate cage is not really an issue, rather it is the diameter of the mounting plate; it can't be too large or the CW shaft would strike it. The mounting plate only needs to be large enough so that the j-bolt nuts can clear the CEM120 bottom plate and allow for 4 mounting holes to be drilled it it. Naturally, you want those four holes to align the mount to true north.



#15 markm75c

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Posted 15 July 2019 - 11:45 AM

Page 22 of the manual has a side view of the mount, and you can get a good idea of the clearance needed for the CW shaft:

 

http://www.ioptron.c...Instruction.pdf

 

for your latitude.

 

The height of the rate cage is not really an issue, rather it is the diameter of the mounting plate; it can't be too large or the CW shaft would strike it. The mounting plate only needs to be large enough so that the j-bolt nuts can clear the CEM120 bottom plate and allow for 4 mounting holes to be drilled it it. Naturally, you want those four holes to align the mount to true north.

Would it be a better idea to actually go with two plates, one flush with the top of the pvc pipe, jbolts coming up out of that, then into a second plate 2" above that for the actual mount,

vs..

Just one plate maybe 2" above the pvc pipe? (still feels like i'm guessing here on the way to insert into the wet cement if one plate).

 

And on the jig, i guess the plywood doesnt matter much? ie: this sheathing for about $17 for a 2x4 panel should be good enough to cut even a square that is say 14"x14" with the hole patterns in it ?  Im guessing i could buy the same sheathing to make a box for the concrete that is likely to be 14" high out of the ground above the hole ill be digging 4' deep (18-24" round or square or round to the top then square at the surface).



#16 Whichwayisnorth

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Posted 15 July 2019 - 12:22 PM

Cement is more stable than metal.  I found this blog when doing a google search for cement telescope pier and it looks like a winner to me.

 

 

http://darkerview.co...rdpress/?p=2719



#17 DuncanM

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Posted 15 July 2019 - 12:46 PM

Would it be a better idea to actually go with two plates, one flush with the top of the pvc pipe, jbolts coming up out of that, then into a second plate 2" above that for the actual mount,

vs..

Just one plate maybe 2" above the pvc pipe? (still feels like i'm guessing here on the way to insert into the wet cement if one plate).

 

And on the jig, i guess the plywood doesnt matter much? ie: this sheathing for about $17 for a 2x4 panel should be good enough to cut even a square that is say 14"x14" with the hole patterns in it ?  Im guessing i could buy the same sheathing to make a box for the concrete that is likely to be 14" high out of the ground above the hole ill be digging 4' deep (18-24" round or square or round to the top then square at the surface).

 

I'm not up on cement versus metal piers. I went with steel piers bolted to a thick concrete pad. I would suggest, however, that if you have a concrete pad that a stiffened tripod sitting on the pad is really all you need and that you'll derive no additional benefit with a pier. I went with piers because I have 3 mounts in an 8ft x 16ft roll-off and I needed to free up as much floor space as possible, not because thought the piers to be intrinsically superior.

 

I'm guessing a single plate is just as good and easier to fabricate. You can use full length ready rod rather than J-bolts because the ready rod will substitute for rebar.



#18 markm75c

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Posted 15 July 2019 - 02:33 PM

Have you looked at Dan's Pier Top Plates?  I'd bet Dan would be willing to work with you to get you something that would work with the 120.

 

Also, look at what Rainer (Real14) has done with his 120's.  https://www.cloudyni...0ec2/?p=8748466

 

There are many ways to get a good setup for your mount.  smile.gif

 

I looked briefly then saw the rough price appeared to be $550 for the plate (vs about $480 for an ioptron pier) and opted to not go that route.



#19 markm75c

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Posted 15 July 2019 - 02:36 PM

I'm not up on cement versus metal piers. I went with steel piers bolted to a thick concrete pad. I would suggest, however, that if you have a concrete pad that a stiffened tripod sitting on the pad is really all you need and that you'll derive no additional benefit with a pier. I went with piers because I have 3 mounts in an 8ft x 16ft roll-off and I needed to free up as much floor space as possible, not because thought the piers to be intrinsically superior.

 

I'm guessing a single plate is just as good and easier to fabricate. You can use full length ready rod rather than J-bolts because the ready rod will substitute for rebar.

 

I still need to figure out the rebar portion for the dig/tube, i guess 4x #3 rebar at least to the 14" above ground level then 4 feet of it inside the pvc tube with hoops tied with (zip?) ties around it every so often and maybe some extending down into the 14" above ground square.

 

What i'm not sure on is what bolts i should be looking for at lowes, i think 3/4" of some kind with the nuts and washers.  Or 1/2" by 8" long (assuming i dont use the full length ones)



#20 DuncanM

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Posted 15 July 2019 - 02:44 PM

I still need to figure out the rebar portion for the dig/tube, i guess 4x #3 rebar at least to the 14" above ground level then 4 feet of it inside the pvc tube with hoops tied with (zip?) ties around it every so often and maybe some extending down into the 14" above ground square.

 

What i'm not sure on is what bolts i should be looking for at lowes, i think 3/4" of some kind with the nuts and washers.  Or 1/2" by 8" long (assuming i dont use the full length ones)

These guys should be able to supply any metal that you need and they'll cut plates to any spec as well, IIRC:

 

https://www.metalsup...com/pittsburgh/

 

1/2in or 12mm should be fine for bolt size.

 

They also sell steel tubing, so you could buy two steel plates and a tube and have a welder make you a pier.



#21 markm75c

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Posted 15 July 2019 - 03:24 PM

These guys should be able to supply any metal that you need and they'll cut plates to any spec as well, IIRC:
 
https://www.metalsup...com/pittsburgh/
 
1/2in or 12mm should be fine for bolt size.
 
They also sell steel tubing, so you could buy two steel plates and a tube and have a welder make you a pier.

Thanks that could be the ticket on the pier plate.
 
Though for instance on their aluminum page there are quite a few to pick from:
https://www.metalsup...aluminum-plate/
 
ie: Aluminum 6061, 2024 etc and thicknesses, if going aluminum anyway.  Seems they offer a square option, dont see a circle but i can inquire once i narrow it down.

EDIT: I'm thinking it might be the 0.250 AL 6061T6 PLATE selection

Edited by markm75c, 15 July 2019 - 10:51 PM.


#22 markm75c

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Posted 15 July 2019 - 10:44 PM

Also.. i found this pvc pipe to use for the pier possibly, i think its the right pvc and the price seems right at 75 shipped



https://www.rainharv...s0aAgpuEALw_wcB

 

 

Im thinking these are the right length jbolts if enough threads too:

 https://www.homedepo...GAB1/202090707 


Edited by markm75c, 15 July 2019 - 11:16 PM.


#23 Chuckwagon

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Posted 16 July 2019 - 12:13 AM

I looked briefly then saw the rough price appeared to be $550 for the plate (vs about $480 for an ioptron pier) and opted to not go that route.

Wow, they've gotten quite a bit pricier since I bought mine.  :)  Bummer.



#24 markm75c

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Posted 16 July 2019 - 01:09 PM

Well i decided to sketch the whole thing out and now this looks really tight for one plate and 12" circle?

 

jbolts x 4 at about 1.8" from the edge and the edges of the mounting plate close to the edge (not sure how critical that part is)?

pierplatedrawing1.jpg



#25 Chuckwagon

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Posted 16 July 2019 - 02:22 PM

Well i decided to sketch the whole thing out and now this looks really tight for one plate and 12" circle?

 

jbolts x 4 at about 1.8" from the edge and the edges of the mounting plate close to the edge (not sure how critical that part is)?

Use two plates.  :)  One that adapts the base of the mount, and one that adapts the top of the pier.  3 j-bolts in the pier (easy leveling) at 120 degree spacing 2" from the outer edge of the pier, and 4 connecting bolts (you can use a bushing, or sleeve to set the distance between plates) between the bottom and upper plate, with the mount base directly attached to the upper plate.




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