Jump to content
I Forge Iron
Antoine M.

Little giant foundations, vibration question.

Recommended Posts

Hi all!

I just moved to a new house and I have to move my 100 pouds little giant.

My old shop was about 60 feet from the house and built on heavy clay soil. I went with a full blow foundation, 4 feet deep with a rubber mat (the one for cows).

My wife could feel the vibrations from the hammer in the house albeit not vey hard, but she knew when the hammer was running.

 

Now, the soil is sandy with a fair proportion of small rocks, round ones like river rocks, drains really well. The big difference is that my new shop is an old garage attached to the house. I mean right next to it.

I'm planning to cut the cement floor to isulate the hammer and go with cement again (Still four feet? Could I go for less?).

Should I be worried about excessive vibrations? The house is an old house (1827) and I'm a bit worried for the stucture and the comfort of the familly... Is there another option than cow mats to dampen the vibrations? Looking for inputs!

 

Thank's!

Share this post


Link to post
Share on other sites

Welcome to IFI, @Antoine M. Glad to have you. You might want to head over to the Introduce Yourself page and let us know who you are, but be sure to READ THIS FIRST!

Regarding your question, I don't have any experience with this myself, but if you search the forum*, there are many good threads about power hammer foundations that should get you headed in the right direction.

 

*Don't use the forum's own search feature, which isn't very good. If you do a web search (with Google or the like) and include "iforgeiron.com" as one of your search terms, you'll probably find what you're looking for.

Share this post


Link to post
Share on other sites

Soils vary such a great deal, as does the amount of moisture that can be around....just to add some extra variability. So it can be difficult to provide you with the perfect antivibration solution.

 

The above caveat out of the way, I'm a huge fan of using an isolated inertia block. Dig a big hole;

put a reinforced slab in the bottom (35 MPa is good);

put up some side walls that do not touch the edge of the bottom slab (this is to stop the surrounding soil from collapsing in);

put some vibration mitigating matting on top of the slab;

construct a suitable form for an inertia block (you mentioned that you previously had 4' deep concrete and I assume that it would have been slightly larger than the hammer's base, that would probably be a reasonable starting dimension, making sure that it does not touch the side walls);

you can either pour this in situ or if you have easy access to lifting gear you can do it elsewhere, you can also make allowance for hold down bolts (really long T-headed bolts work ace) and adjustments to working height;

Now you should have your inertia block sitting on some antivibration matting, which is sitting on the slab at the bottom of the hole. The hammer base (or standard, depending on yoir lingo) then needs to have something to sit between it and the concrete top of the inertia block. Lots of people use sawn boards, I'm a huge fan of using what we call form ply here. 3/4" thick is all I've used, it is just there to help bed the cast hammer base onto the concrete and even the 5cwt has not crushed it. I also use the ply to cover the void between the existing floor and the inertia block.

Lots of people just cut the slab around the base of the hammer, especially for smaller hammers. Sometimes the soil mechanics gods are smilling upon you and the vibrations are not travelling around the neighbourhood , but wuite often this is not the case. 

If you look on this site for any posts on about this subject by Alan Evans or JohnN you will be well on your way to mitigating those vibrations and broken crockery.

 

Justin

Share this post


Link to post
Share on other sites

Oh, it is also sometimes a good idea to include an option for a sump pump in the bottom of your inertia block hole.

Learnt that one the hard way.....

Justin

Share this post


Link to post
Share on other sites
3 hours ago, AnvilAntics said:

Learnt that one the hard way.....

The hammer floated?

Share this post


Link to post
Share on other sites
7 hours ago, JHCC said:

The hammer floated?

I hate it when that happens, don't you? On a slightly more serious note there's a Blacksmith called Jake the Mad Russian lives on the Yukon River who almost had his 25lb. Little Giant carried off when an ice jam caused the Yukon to flood. It was the floating ice that was carrying off the heavy stuff but the only reason his shop wasn't carried off completely was because he had so much iron besides his anvils, power hammer, vises, etc. all chained together and anchored up the bank a ways. 

Sorry for the digression, I'm like that you  know.

Welcome aboard Antoine, glad to have you. If you'll put your general location in the header you might be surprised how many of the gang live within visiting distance.

Clay is a good conductor of vibrations, sand not so. The problem with sand, especially alluvial sand as indicated by round rocks in the mix, is it doesn't compact solidly and wants to shift under load and vibration. Not a big issue if you can afford to make a good base for the foundation. How much time, money and work do you want to put into setting up IN the garage? You are talking about cutting out a space in the slab, excavating either to a suitable soil or far enough a good base will stabilize the hammer. 

This gets straight into the old, "Good, Fast, Cheap,Pick two" saying. If you do the work by hand you can probably do it for a few hundred bucks in tool rental but the concrete could be an issue depending on how large a block you want or need.  A 100lb LG needs a good foundation, do you have a copy of, "The Little Giant  Powerhammer" by Richard Kern? Hold onto your hat Antoine, here's what the book calls for. a 100lb. LG foundation.

Reinforced concrete foundation block, 58" long x 39" wide x 36" deep. Anchor bolts sunk (it's hard to read) approximately 23" or 2.3' into the block through steel plates. The top 6" of the anchor bolts are set in 1" dia x 6" long steel pipe sleeves and then up through the hammer base to receive washers and nuts. The anchor bolts of course have to be laid to match the holes in the base. Yes? Okay, that's about a yard and a half of concrete, figure figure approx 6-7k lbs. 

You'll need to cut a hole in the existing slab about 1" larger on a side to allow the the material to isolate the foundation block from the slab, 1/2" ground contact treated plywood may be acceptable but is a code issue, you'll have to check. Once you've cut the floor slab, I recommend a saw rather than jack hammer, a smooth straight edge makes isolating the foundation much easier. You'll still need to break it up to get it out.

I can't tell you how much deeper you'll have to excavate without being able to check out the soils myself but a reasonably safe bet is excavate a minimum 1' deeper than the bottom of the foundation block. Fill with D-1 or if that's not a classification used where ever you live use crusher run 3/4" minus. Crushed aggregate will compact hard and not shift. Do NOT add a bunch of water when you compact, that's not a proper way to compact, no matter what the old guy at the gravel pit or driving the dump truck or whatever says. You only want enough moisture to act as a lubricant, too much displaces fines in the aggregate and leaves voids when it drains. 

What you compact with will determine how thick the lifts are. A "lift" is a layer of soils added to the base. If you're using a hand tamper 4" lifts and beat it till the tamper bounces. You can go with 6" lifts if you want to man handle a plate compacter in the hole run it till it's skating and bouncing like crazy. You can go with more than 6" lifts if you use a "jumping jack" compacter but they can get away from you and mess up the excavation.

Once you disturb the existing grade you'll need to replace it with compacted aggregate. To this end I highly recommend you form up the excavation as soon as you have it dug. Bury or soil contact treated plywood in a open bottomed box and staked deep will hopefully keep the excavation from caving in. Just leave it when you pour, if it rots out in 50 years who cares, it can be the isolation strip too. Right? 

Okay, that is your excavation, compacted base and form. Tie your rebar and if you really want to go with the long anchor bolts and plates, support them in place by tie wiring it to the rebar. Make a template to position them properly at the surface. I cut and clamped a piece to the bottom on the hammer base and drilled through the anchor holes. If you wish to go whole hog including the 1" pipe sleeves drill the holes so the sleeves are held in position with the bolts. 

The book calls for a 3/4" cork or rubber mat between the base and foundation block so give your anchors enough length.

I'm not a concrete guy, I was a foundations guy, worked in the lab, did aggregate designs and for the last 20 years working for Foundations Materials was a driller. Anywho, the above is a general description of accepted foundation, soils preparations it may be very different where ever it is you live. ;)

Frosty The Lucky.

 

 

 

Share this post


Link to post
Share on other sites

Thank's for the help and sorry for not getting back to you guys sooner; moving can be quite intense!

Well it's quite an involving project! I'm not sure if I really want to go trough it. I've been thingking alot and as a knifemaker, I don't know If I absolutely need this hammer and the money of building such a foundation might be better put in an hydraulic press for the type of work I do...

PS. If I break any rules of the forum please tell me!

 

Offer for 100 lb Little Giant moved to the tailgating section.

 

Share this post


Link to post
Share on other sites
On ‎23‎/‎08‎/‎2017 at 3:21 AM, JHCC said:

The hammer floated?

Sorry for not replying earlier, am very sad that you are selling your hammer.

I did not wish to make it seem difficult or expensive to install a hammer. There are so many different ways to do it, so many different scenarios and so many different outcomes. I was trying to describe what had worked best, in reducing transmission of vibration, for me in a couple of hammer installations.

 

Below is a "back of the envelope" sketch of what has worked really well for me. Please note that it is not to scale and the space between the inertia block and the pit wall is not as big as sketched...oh, the 300mm for the foundation pad is variable depending on hammer size and it id better to have the reinforcing x2, one closer to the base and the other closer to the top of the pad.

Trying to separate the hammer from the rest of the world is the name of the game. It doesn't have to take massive holes and massive amounts concrete.

 

On the unanswered floating hammer question......it didn't quite float but when in operation it did seem that way. The hammer was a 7cwt Alldays and Onion. It was installed very similar to the "sketch", but instead of isolation matting under the inertia block there were 5 (maybe 6?) mounting blocks that I was lead to believe were for either mounting large diesel generators on ships or in basements of hospitals. When the hammer was in use, it used to feel like it was rocking back and forth, but without too much transmitted vibration. On one occasion after some particularly heavy rainfall, we had someone from a neighbouring workshop comment that whenever we used the big hammer, they had water shooting up their wall........ There were some concerns about undermining of foundations, but it was worked out that the inertia block was working like a big diaphragm pump. Sump and a pump were installed. But when you were using the hammer it did feel like you were floating.

2016-08-20 11.41.33.jpg

Share this post


Link to post
Share on other sites

Hi All. 

I know I'm replying to a dormant thread.  The "back of the envelope" sketch above is making pretty good sense.  I'm not sure what one would use as anti-vibration matting.  I recently got a rubber mat at a farm supply that was sold as a stall mat.  

What I'm looking at installing are two hammers, one is a recently constructed tire hammer, and the other is a 50 lb little giant -- still with some work to do on refurbishing, but there is hope.  So, both are in the same general size range.   I gather that the diagram above was drawn with a much larger hammer in mind.  

My initial thought was to just bolt the tire hammer to the shop floor and see what happens. My shop is the pretty typical 30 x 40 metal building on a concrete pad.  I bought it from the previous owner, so I wasn't there when it was built.  I've drilled through the floor for mounting bolts for other purposes, it seems to be about 4" thick. 

Just a few days ago I was forging with a buddy (this is still forging by hand, the hammers are not installed) and just using a 2 or 3 pound hand hammer on the anvil, and noticing stuff falling off a table maybe 20' away. So thinking about this and scaling up the size of the hammer from 2 pounds to 50 or 70 makes bolting to the existing floor seem like possibly not such a good option. 

The soil here contains a lot of clay, or I would say the topsoil is thin and the subsoil tends towards clay.  I'm not a soil expert! In fact I'm retired from teaching math and some physics, so installing heavy machinery is somewhat out of the range of things I know much about.  

So back to the drawing above.  The idea of isolating the hammer inertia block from the surrounding floor and soil makes a lot of sense.  Any input or thoughts are welcome. 

Thanks,

John Dilsaver

Sparta, MO

 

Share this post


Link to post
Share on other sites

Hi John,

If you remember how BigBlu 155 is mounted at ESSA, it sits on a one inch thick stall mat. When the building was built either the architect or contractor messed up and put the isolation pad in the wrong place for it, at the other end of the building away from the forges. The floor where it sits now is the standard  4 inches thick and Blu is bolted down with anchor's. After using a while the floor started to crack around the hammer and a square around Blu was cut with a concrete saw to isolate it and make it free floating. It's been working fine since then no more cracking.

Randy

Share this post


Link to post
Share on other sites

John: The problem you have isn't the hammers, I have a 50 lb. Little Giant on the 6" slab in my shop. At full speed my hammer barely ripples coffee in a cup in the shop. 

Mine doesn't shake anything because I built on glacial til, a lateral moraine to be more specific. Unconsolidated soil doesn't get more dense or hard without turning back into stone. Nothing like a couple few thousand feet of ice rumbling over it for a couple few thousand years to compact soil eh?

Your issue is what's known as FS soil, Frost Susceptible. Clayey soils are very susceptible to liquefaction when disturbed. Little moisture <10% is enough for it to pump up, become plastic or even liquefy. Hand hammering causing things to fall off shelves anywhere in the shop means the sub soils are probably at or close to their liquid limit. 

I'm thinking you need to make a dedicated foundation for your hammers though it's not usually necessary for a 50 but you have to have competent soils and I don't think you do.

Isolation mats are typically wool felt, it has good compressive strength and doesn't conduct vibrations well at all. That's a last detail though. 

The best I can do from here, without a test hole or two maybe even a soils lab test is make general observations and suggestions. The best thing you could do is drain the soil, clayey soils will compact to concrete density if almost dry, say 1.5% - 3% moisture but draining clays is a PITA. Surround the building with a "French Drain" and a clear channel down hill. Or if there is permeable soils deeper, a couple "dry wells" might do the trick. Clay is impermeable, water can't flow through it so it's absorbed till it's pudding. However if disturbed or there is enough water clays are nearly colloidal it only settles out of water very VERY slowly and will stay at or above it's liquid limit until the water is removed. You can do an experiment by putting a cup of your soil in a quart mason jar, fill it 3/4 full of water and shake till it's dissolved. See how long it takes to settle out and if the clay ever settles enough to not be liquid.

Clay is a real PITA. You need to isolate your foundation from ground and surface water, hence the "French drains." Deep trench lined with a geotextile and filled with drain rock. A dry well is a deep hole lined with geotextile and filled with drain rock.

Might as well put both hammers on the same block, they aren't that big, you'll need to excavate, hopefully to a permeable layer. If water can flow away from your hammer foundations you're golden. If not, the deeper the better and let them spread a LITTLE as you go down, wider at the bottom than the top. Do NOT get silly and bury yourself in a cave in!!:angry: 

You need to get down where it starts drying out if you can roll some between your palms and it crumbles good if it forms rolls keep digging. Forming rolls between your palms in this field test shows it's at it's plastic limit, shake it and it'll become plastic. 

If you can put a marble size piece in your palm and vibrate it by gently bumping your wrist with your other fist and it slumps or gets shiny and water runs out the soil is past it's liquid limit. Shake it and it will liquefy under you this is a B A D thing. Envision buildings laying on their sides after major earthquakes BAD. The vibration from a power hammer will turn the soil into pudding. Things falling off shelves to hand hammering sounds like past it's liquid limit to me.:o

Dig till you have competent soil conditions. If you reach permeable soils, sand, gravel, etc. a bucket of water drains into the soil in a couple minutes you can stop digging. Now is fill time, lay geotextile so it covers the bottom and up the sides, you can fold it, stitch it, duct tape it, it's all okay so long as you don't cover it with plastic. You want to form a sack, nothing fancy just a sack.

Geotextiles allow water to pass through but filter out fines like clay particles. Once you get water to flow through your foundation silt wants, yes WANTS to infiltrate and fill the voids and in no time the foundation is impermeable. You make a bag with the geotextile and lay drain rock on the bottom a foot should be enough. UNLESS this hole is >6' deep, them make the drain rock a couple feet thick. Drain rock doesn't compact really well so don't get carried away with it. 

This is your drain bed under the hammers. Fold the geotextile over the drain rock, you really need to keep fines out of the drain. From here up you want to lay compactable soil gradations, in lifts that can be compacted hard with whatever tools you have available. If you have a plate compacter 12" - 18" max per lift and compact it till it bounces. Use VERY little water during compaction no matter what some knothead says about pouring the water to it! Mud won't compact and when the moisture drains away it's no longer compacted. Yes? If the compacter doesn't bounce make the next lift shallower, you want it to bounce.

If you're using a jumping jack compactor you can lay thicker lifts but they're pretty unsubtle compacters and not great for a finish grade. Think lumpier finish.

I'd call the fill good between 8" and 12" of the slab surface. Make the last 12" of fill 1" minus crusher run, this can be compacted like concrete and your poured concrete block happy to stay right THERE. This last layer is your "sub base" and your concrete is going to lay directly on it so the top of this lift when compact is your desired block thickness below the existing floor level. Yes?

8" - 12" of concrete is more than enough, don't be stingy with the rebar but don't get crazy. lay the bottom layer maybe 2" off the base on a 12" or 24" grid, tie it with iron wire where it crosses. The next layer of rebar in the same size grid but rotate it 45*. 3 layers for 8" is over kill but not too and dandy for 12".

Before you pour your block lay the felt isolation around the hole so the concrete pad and the hammer blocks don't touch. Wool felt should be available at the concrete plant or supply. You might have to ask around. go ahead and glue it to the floor slab if it doesn't already have an adhesive side. Double sided tape works nicely.

Please bear in mind I live around 3,000 miles away, haven't worked in the soils lab in 40 yrs. nor geology section in about 25 yrs. I don't have a soils report let alone test results so this is just educated speculation. 

If you start digging and run into something weird give me a shout or call a soil test company. The State DOT soil lab works for you, you can call them and ask questions. Bear in mind they don't have to put up with you if you're a pest. However, most lab techs (Lab rats in the vernacular) rarely mind something to break up the monotony of shaking samples, doing Proctors, etc.

If nothing else they can recommend books and publications and they can't really deny you general soil information for your area, if there's a major road nearby you might find lab reports and construction recommendations. This is a BIG good thing.

If you can get a lab report and constructions recommendations I can be a LOT more helpful.

Yeah, I worked for Alaska DOT HQ materials, foundations and spend a while as a lab rat. No sane person would accept my signature on a foundation recommendation but I have a general handle on the subject. It's no accident MY house and shop are built on glacial til. ;)

Frosty The Lucky.

Share this post


Link to post
Share on other sites

Randy and Frosty, thanks for your quick replies.

Randy, I didn't know those details of Big Blue down at ESSA.  That's interesting.  Just thinking about the hilltop ESSA's shop is on and the fairly level karst area I'm in, my situation may not be quite the same.  My first thought was to just bolt them to the slab and have at it.  - I guess I might still try that, but seeing how things were bouncing with just my buddy and I hand hammering kind of got my attention.

I've had some drainage work done around the shop, essentially a french drain with an underground pipe draining to the highway drainage ditch, all done about 18 months ago.  This was to address the fact that the land on the east side of my shop is a few inches higher than the shop concrete slab floor and with heavy rain the water would pool on that side and actually stand on the shop floor.  Not good. The drain I had put in has helped a lot.  Water never stands against the building now.

Frosty, thanks for your information.  I'm thinking I'll be starting to dig soon.  I found an extensive soil survey of my county online, but haven't really made a lot of sense of it yet.  

Frosty, I read your advice about the french drains and draining downhill and kind of have to chuckle.  The ground right around my building isn't absolutely level, but it's pretty close.  I've had drainage problems for all the 27 years I've been here.  Also, the drainage that does exist in my immediate area is all karst.  There's not a surface stream that goes anywhere.  It's all sinkholes, water drains into them, and in most cases drains out quickly, but in some sinks it pools and drains away very slowly.  Here in my area this summer has been unusually wet.  The ground is wetter than average, no crunchy grass in August to temporarily pause the lawn mowing season this year!

I'm going to try to make some sense out of my county (Christian Co, MO) soil survey.  I have a class over a John C Campbell in a few days, looking forward to that.  It may be a couple weeks before actual digging.  I have a youthful friend or two I may be able to draft for help . . .

Thanks again for your thoughts and I'll post more as I know something!

 

John DIlsaver

Sparta, MO

 

Share this post


Link to post
Share on other sites
16 hours ago, johndilsaver said:

I guess I might still try that,

Seeing as I'm a guy that follows the path of least resistance, that's what I would do. Bolt the tire hammer down with a double layer of stall mat beneath it and have a go. If it shakes stuff off the benches then cut a hole and start digging. You're not out much labor by trying it first.

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.


×
×
  • Create New...