Anchoring Threaded Fasteners In Bedrock With Epoxy

Sounds like you know what you are doing to me...
Del
_{(I took pity 'cos you had no replies. Glorious sunny weather here in the UK)}

Good luck with your project. I've got my own observatory with a permanent pier anchored onto a 3-foot deep concrete pad. The largest scope I use on it is a 10-inch Newtonian, but I could probably put a 16-inch scope on it (someday...).

In your case, I was wondering if using epoxied bolts is the best way to go. I don't have any experience with epoxying a bolt into stone, but I have seen people used expansion bolts made for concrete and stone. Here are a couple of links you might want to look at.

http://www.h-b.com/images/submittal/stoneanchors/sleeve-exp-bolt.pdf

http://www.boltdepot.com/anchoring-products.aspx

Again -- good luck!

I've used an epoxy made by "Hilti" (a company from Lichtenstein) for similair anchoring

projects. The set up time is about 1/2 hour, and the heat lamps and glass shards

would not be needed.

I've done this in brick,stone, block, and concrete, and always with positive results

Check it out,I am quite certain the "Hilti" epoxy is available in Canada.

Good Luck

GA, Kay. These construction epoxies are the hot setup for tying in rebar to existing concrete foundations. The fellow who repaired my house foundation after the Loma Prieta earthquake was a sharp engineer who knew what he was doing. He drilled 5/8 inch holes 6" into the concrete for 1/2" rebar and then filled them with a product just like the Hilti product. The shear strength of the epoxy alone was enough that at 6" deep the rebar would break first before the epoxy would shear. The mixed epoxy was fairly low viscosity so it readilly flowed into a horizontal hole and a little modeling clay at each end formed a nice reservoir that kept it from leaking away.

That all said I don't understand why our OP doesn't employ the principles of dynamic vibration isolation in constructing his telescope foundation. This approach is standard operating procedure for precision optical tables as well as mechanical metrology calibration labs. Hard igneous and metomorphic bed rock is a wonderful transmitter of vibrations from all kinds of sources such as nearby machinery, vehicles on roadways, radio and TV sound sources, far away trains and even human footsteps. I have to believe that sophisticated amateur astronomers have already worked out the practical design details for such foundations. I'm not sure what is the right material for the "spring" part of the isolator. Maybe some kind of low density foam?

Ed Weldon

Look into (coal) mining roof bolts. When I was involved, there were two approaches--one was a mechanical expansion anchor, the other was an epoxy approach.

The epoxy approacy used long cylindrical plastic "bags" with separate longitudinal sections for the two portions of the expoxy. The bolt hole was drilled (don't remember the diameter, probably somewhere around an inch to inch and a half, plastic bags were inserted to fill the hole, then the roof bolting machine (which also drilled the hole) used its hydraulic lift (we were bolting the roof) to push the bolt into the hole while spinning it to mix (and heat) the expoxy. Then the bolt was held in place for 1 minute, at which point it was considered cured enough to hold, but it may have cured more after that point.

My only concern would be that we always used the bolts in an underground mine which maintained year round temperatures of around 68 degrees F--you're in a significantly colder environment.

By the way, epoxy roof bolts are basically rebar (with the little bumps on the shaft) with a (hex or square, I forget which) bolt head and, hmm, what to call it--sort of an integral washer) formed unto one end. IIRC, we used roof bolts ranging in size from 30" to 8', depending on the strata of the roof above the coal seam. I seem to remember that longer bolts were available.

If the expoxy approach doesn't sound good, the mechanical roof bolts might be a good choice (available in similar lengths, but could be cut to shorter sizes).

Your local Home Depot, Lowes or similar should have twin cartridge epoxy made for mounting rebar in poured concrete. I suspect poured concrete and bedrock are similar enough for this to be a good option to consider. I think my local store has epoxy from "Simpson Strong Tie" but that is probably just due to their current business deals. My locally available epoxy is two large cartridges and some sort of a spiral spout that will mix the two "on the fly". Just squirt it in the hole (using the special spiral mixer spout), stick the rebar in and wait about 20 minutes.

I have bought the two tubes and mixed it by hand for very small jobs like hurricane hardware in an exterior wall. I was always happy with the result but do have two comments:

1) It is pretty expensive. Years ago I think I paid US$25 for two tubes.

2) For small jobs it is easy to be casual and get it on your hands while working with it. When it "kicks" it gets VERY HOT and it does it VERY FAST. If you have it on your hands you will be surprised at how fast you can spit.

Also, being a "code approved" method of mounting the rebar might be helpful when dealing with customer(s) and/or code people.

Bruce

PS I am in Florida. You might want comments from someone in the Great White North just in case things are different up there.

This is probably going to sound sophomoric, but here goes anyway. Since you have what you are calling solid bedrock, if you can find a level enough spot that is reasonably flat, why not simply bond the concrete base or "pier" directly to the bedrock, depending of course on the composition of the stone, a "hot" alkaline mix should be able to grout the concrete base to the stone in a two step pour, even simpler than drilling and anchoring. I suppose you might want to experiment on a small scale (say about 4" diameter) first, and see if you can easily dislodge it. If the 4" version cannot be dislodged (even if you embed a 2-3 ft length of rebar in it, then you have something.

Quote, This is probably going to sound sophomoric, but here goes anyway. Since you have what you are calling solid bedrock, if you can find a level enough spot that is reasonably flat, why not simply bond the concrete base or "pier" directly to the bedrock, depending of course on the composition of the stone, a "hot" alkaline mix should be able to grout the concrete base to the stone in a two step pour, even simpler than drilling and anchoring. I suppose you might want to experiment on a small scale (say about 4" diameter) first, and see if you can easily dislodge it. If the 4" version cannot be dislodged (even if you embed a 2-3 ft length of rebar in it, then you have something. End Quote

On smooth rock, with hard freezes/thaws many times during the season, I do not feel this would survive very long.

I'

Ive used concrete lag shield anchors before so I'm not quite sure why I got so attached to the epoxy. I'll go with these thanks.

My commitment is to replicate the scope exactly as it was built shortly after World War Two. This is not out being done out any attachment to it's design but simply because her father designed and built the scope before he died and I want to maintain it's authenticity and protect the symbolic importance.

In 1947 anyone with a 6 inch Newtonian had a huge scope! The optics of the replica will be modern but by today's standards (my newt is a 16") very modest.

The pier is novel.

He used the bell housing from the left side of a pre-WW2 Ford rear axle!

As you can see, it looks as if it were purposefully made for holding a telescope. 65 years later, I successfully obtained one in great shape on e-Bay!

It's the bolt pattern on the flanged end of the bell that is driving this mounting choice. There are ten 3/8 inch bolt holes on an 8 inch BC so I'll use 10 3/8 threaded rods to anchor it.

I learned something while exploring the web sites some of you suggested. One does NOT use brass nuts with hot dipped galvanized steel! Live and learn.

The use of concrete lag shield anchors allows me to use longer threaded rods than some of the alternatives and the price is right.

The concrete pad is less a structural element and primarily to provide a stable, level pad.

I engineered the complete design of the replica in Solidworks mechanical design software.

Flanged 2 inch ball bearings with a 1 inch bore are a press fit into the welded cluster of 2 inch steel pipe that form the German Equatorial Mount. The loads are very modest so tapered roller bearings won't be needed.

A rendering of the Solidworks final assembly model was inserted along side an old photo of the original scope. I need to tweak the sizes a little but we are close.

I thank all of you for the generous support.

This scope means a great deal to her and pleasing her means a great deal to me.

Thanks for supporting a very important project with a great deal of personal meaning for both of us.

Laughing Jaguar

I feel left out. I don't have any telescope stories.

This keeps bugging me. The mount looks permanent and I don't see any provisions for protecting the telescope from rain, snow, bugs, nesting birds, etc. How is the telescope protected when not in use? Is it just covered?

Bruce

Hi Bruce.

No self respecting astronomer is going to leave his mirror unprotected.

With small scopes, over-the-top clamps are opened and the entire optical system is lifted out of the cradle and moved in doors.

With really large scopes, the primary cell is removed bringing the main mirror with it and that is brought indoors. The tube is then covered, often with a shower caps and a tarp to seal off the interior from the creepy-crawlers.

Laughing Jaguar

In mining we often use a water proof grouting material, this search will show you many ideas. Often the grout costs less than the epoxy, but you may have to buy a 50 pound bag or?.

grouting bolts

Ed Weldon asked: ". . . . . I don't understand why our OP doesn't employ the principles of dynamic vibration isolation in constructing his telescope foundation."

That's a very valid point Ed. You must remember that:

1. this scope is not for my use.

2 It's built for my friend whose love of her father is the driving factor here, not her love of astronomy

3. The place is remote and there is no pedestrian or vehicular traffic to introduce the vibrations.

Initially it was my intention to replicate the pier and footing using the same methods I use to build or my own mount for a 12.5" F-8. Or the pier installation I designed for the clubs observatory.

In my cases the walk area was soft grass and the likelihood of vibrations to a pier sunk six feet down onto bedrock unlikely. It was embedded in 180 pounds of Portland cement.

The club's pier is on a 16" column of cement embedded 7 feet. The pedestrian pad is concentric with the pier but a gap with a radius of 1.5o feet isolates the two and is filled with soft rubber to prevent pedestrian traffic from causing vibrations. It has been tested to 450x power without a problem.

I've already designed a floating pad made from two pieces of plate and welded together that float on a pattern of springs and are damped by high hysteresis rubber .

If needed the scope will mount on that and float and there is sufficient mass to do the job. The general consensus is that it won't be needed

Laughing Jaguar

LJ -- Pretty slick your experiences. Looks like you guys are way ahead on your game. I think I'll have some fun exploring the subject on the Internet. I imagine like most amateur endeavors the enthusiasts like to discuss their technical tricks, especially how they turn prosaic materials to new applications. ..........Ed

You might try an anchor made by Simpson Strong Tie all you have to do is drill a 1/2" hole and thread the anchor in place with a wrench or an impact. In testing with these anchors we have maxed out our hydraulic gage at 25.000lb before the fasteners let go. and when they did the fastner came out with a 6" plug of 4500lb concrete attached. The fastener did not let go the surrounding material did. We use these anchors to attach safe's to concrete floor's and so far in the last 7 years we have not lost a customer's safe. We have had several attempt's to steal them but so far non have been taken to the best of my knowledge. One good plus to these anchor's is that if you need to remove them you just get your impact out and remove them, and replace them when you are done making a repair. As simple as that with no loss in holding power or loss of anchors.They come in many length's from 3" up to I believe 12". Hardened steel with a Zinc Chromium finish it should last a very long time in the elements.

The Epoxy we use to retrofit earthquake prone, or failed foundations is SET, by Simpson, as mentioned above here--Calc'ed out by Cal. Building codes--Easy to use, 1 gun, two chambers, with a twist-mix nozzle--Fool proof, and reasonably cheap--Tougher than nails--In wet areas , we use a stainless all-thread--Careful with those, as all stainless is not alike-Some are brittle and some are malable--HAve questions about the vibration systems, as we also have built isolated sound studios, that have to be tested with Oscilloscopes, for sound and vibration transfer, across many frequencies----I would opt for a single post, with 360 degree gimbaled, adjustable in many different planes and vibration mounts, that isolate the instrument--The least amount of contact with the substrate, the better-- But the only telescope I have are some birding glass, and a real good 7x50 set of Marine binocs, that are isolated by an old pair of hands , that often have a beer in them--In that respect, I am afraid I am useless for your project--Thanks much for greasing the many wheels on this thread, and let us hear how it all works out!

Jag, you may also want to check out another Simpson Strong-Tie product. It's a relatively innovative concrete anchor that actually threads into the pre-drilled hole like a bolt! It even looks like a hex-headed bolt, but has slightly tapered threaded tip. Threads are somewhat coarser then UNC threads. Yes, that's correct, the anchor bolt threads cut right into the surrounding material. I don't know if they'll cut into rock or not, but it maybe worth a try. They come in all sorts of lengths and standard diameters....I believe that they even come in metric sizes as well!

I forget the actual product name, but I'll have to go down into the basement later today to check out my stash of them and get back to you. You may be able to find the product name on the Simpson website.

I bought my box of 'em very cheap on Ebay...about 50% less than what the big box stores were asking for them. It's a very simple design (Patented), and easy to ratchet into the receiving hole.

I'm going to use them in lieu of standard J-anchors to anchor my future DIY 2-story steel-framed toolshed/storage building to the floating Alaskan RC Slab....

BTW, nice scope!

Another name is TAP-CON--Same product, different name--Use them for all of our interior wall plates now, rather than the old Hilti, 22.Cal concete shot nails--Make sure to put a little bees wax on the threads and use a hammer drill with a hex nut adapter--Get one stuck, or galled, you will not be a happy camper.. We have had them break in shear, but very infrequently-More of a fluke...

Just remembered the name of the Simpson product I mentioned above:

Titen anchors....they come with standard hex-head or with a hex-headed coupler where you can thread in a steel hanger or rebar.

Do not forget to take a tube. Needs to be small enough to fit in your holes. You will use this tube to blow out the dust and debris from your holes. You can use your mouth as a soource of compressed air (keep one end of your tube clean). Get a tube long enough to make a turn-you do not want your face in line with the hole axis, as when you blow the dust will shoot straight out and get in your eyes.

1. Most of the Hilti and Simpson ,etc are for hang down and/or inside, protected loads. 2. The application should be protected from water/moisture ingress from gravity and capillary action. 3. Once installed cover with a polybutyl such as Sika Flex or 3M 5200 Fast over the epoxy and slathered onto the bottom of the base before bolting. 4. after the set time for this adhesive (a few days) get a baby jar(one each) of two part polyurethane white paint and paint over the bead of adhesive. 5. This protects the adhesive from UV. Not forever, but damn close.

LJ,

You're very well advised by most here, partic. the 'Captain' and others in that vein.

If I were writing the spec for your job I'd have written in to use stainless steel long thread embedded 150(mm) which will facillitate the use of a security device to at least slow down the tampering by miscreants. ( Some bastard WILL do it. It's a great shame that parenting has lost out to 'can't be bothered')

Like, once you've got the nuts snugged down a QUICK strike of arc weld above them will do it. In this it's just fortunate that SS heat transfer rate is not partic. high.

Hilti epoxy embedment process is good, although you need to be mindfull of the advice on the pack as to temperature of application, at the time of application.

Ramset is good also.

I've used hundreds of thousands of both these without a failure. Appropriate lubrication of the treads when using stainless steel fasteners is ESSENTIAL.

If you're using an incompatible material to be fastened down, nylon washers and insulating sleeves are available from good fastener outlets. This won't, obviously allow arc weld securing of the installation though. A severe bruising of the threads would do it though, and if you had to remove the installation at some time in the future the application of a small disc grinder will fix that.

The advantage of chem-set fasteners is that they can be easily placed EXACTLY where they need to be.( My best example of this is when I had to fasten down, to concrete, a manifold to a thrust block with 104 x 20mm SS bolts. There was only 1mm tolerance available in the whole 8metres)

Drill run-off in rock and masonry is common, particularly with inexperienced operators.

Just a few thoughts.

Hope they are of help.

Cheers,

Stu.

My buddy moored his 10 ton boat in Georgian Bay using similar techniques. He sells rock drills etc. to the mining industry. He purchased five rocks in the area. Since these were too small to build on he purchased at auction a large 45 foot house boat.

the 48"wide floating docks were anchored to the rocks by drilling 3/4" holes for eye bolts that were set into the granite rocks. Each floating dock weighed in excess of 500 pounds and the boat displaced 10 tons Despite many storms over the years not one anchor bolt pulled free. In summer the sun warming of the rocks may get it too hot and your catalyzed epoxy may cure too fast. I suggest you drill a hole then measure temp at bottom over night to check but I do not recall my friend needing heat lamps overnight to effect a cure of the epoxy..

The rock east and north of Georgian Bay is pure shield rock, some of the oldest and hardest rock found on earth. Bruce Peninsular is an escarpment tilted upward by plate tectonics and you will find some shale or sedimentary rock in places mixed with shield rock. I find sleeping on either bloody hard even if one type is supposedly softer than the other.

Duck-in-the-pond may have more detailed infor since he has boaterd and anchored there more than I

To all who contributed so generously. . . . . thank you!

I am going to make use of expanding anchors and lock things down with stainless steel threaded rods and brass nuts.

Prior to pouring the shallow cement pad, I will paint the fasteners and their anchor holes with a suitable sealant to help prevent moisture from penetrating.

No point in stressing the rock with freezing water when the temps drop.

I've chosen to dispense with the rebars.

Then I'll pour a cement pad, just thick enough to create a level area for the pier.

I'm signing off.

A most appreciative

Laughing Jaguar

One more try: http://www.bonstone.com/materials/BondingGranite.htm

The above is for bonding granite counters to concrete, and does not appear very temperature sensitive, etc. I have no data for the pull out expected if anchors are bonded using this product. Since you are installing in a remote area and have to hand carry (I suppose) everything to the site, the best practice will be to do the job using materials that weigh less. If you went for a volume of epoxy material sufficient to build the entire base of the pier, I suppose you could still drill and set bars, then build up the base in epoxy rather than concrete to provide a level platform to bolt to.

mining operations have used this system for years as a method for anchoring roof boots. the ambient mine tempeatures in pennsylvania are around 50*f. if done correctly, the bond should be be as strong as the bolts. contact the manufacturer for the correct technic.

One advantage of Phillips/RedHead/Hilti expansion anchors is that the drilled holes are smaller and thus quicker. (No need for extra diameter to accommodate a lag shield or epoxy layer.)