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Will powerhammer crack slab?


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For some reason reading that I am thinking 12" at a minimum. Can you tell me the weight of the hammer itself? I'm sure someone here will know for sure. Can depend on the soil compaction in your area as well.

Btw, this is for the area immediately under the hammer only. The entire shop does not need to be that. Just make sure of where you really want it. pour it under and 6" to the outside and then put in a break yourself. should really cut down on the vibration to the shop.

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chief mcgee - Just for instance, The Little Giant 100lb hammers recommended foundation plan is 39" wide x 58" long x 36" deep. The recommended shim between the hammer and the concrete is - 3/8"-1/2" cork or rubber belting. When I figure out the exact spot my 100lb LG will go - it will get a footing like that. - JK

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I was in a shop that had a 4" slab and a 50# LG and after six months of pounding the entire floor had hairline cracks. After another six months the entire slab was being replaced. If you only do ocassional forging you may get by with putting your hammer on wood but if you are a production shop I strongly suggest that you have a seperate foundation for the hammer.

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Make sure you go with 4000 lb concrete and use rebar and wire under the the area the hammer will go, wire and rebar is cheap and either make it a seperate footing or cut a break around it but probably the best would be it's own footing 24" deep, poured prior to the rest of the floor and then put expansion joint around where the rest of the floor will pour up against it.

Just my opinion, I havn't too much power hammer experience but I do have a bit of experience with concrete.

welder19

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You want a substantial foundation like JK has outlined above and poured with rebar and expansion joint all around like Welder19 says. Also you want to have your hammer bolted down, either set over J bolts poured with the foundation or bolted into something set flush or below the surface (like pipe with nuts welded inside.)

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Chief Mcgee - Mass is everything and isolation is wonderful. I first set a 50 lb Little Giant on a 5" slab with wire in it......four months later one of the fasteners had pulled a 10" chunk of floor up with it. The next step was to pour a footing of 24 x 36 x 24" deep - hammer runs like a dream setting on this with 2 inches of hardwood block and a rubber pad. My Nazel runs on a 2 1/2" steel plate (with hardwood and rubber under the anvil) on top of an 8" floor........works - but lots of shock transfer(would be better isolated). My air hammers run on 2" plates with rubber pads under them and work well. The difference in a mechanical and an air hammer is linear guides verses toggle links on a spinning flywheel = off center spinning weight. My advice is to go with a heavy plate like mentioned above -or go with a poured foundation(prefereably isolated from floor by board perimeter). An other option is a wood bunk foundation (but it tends to burn with drops)

Ralph

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I would be wary of putting 2" of rubber under it, it will bounce - which is annoying to say the least, but will also result in a vertical hammering motion on the holding down bolts which will cause them to rip out or fail in no time.

If you are trying to attenuate the vibration I could write a thesis on it ! - the trick is plenty of mass, and having no point of your isolated interia block in contact with the surrounding ground - the vibration will find the contact point and transmit. If you google 'Fabreeka' it may show some isometric views of inertia blocks for a few ideas.

Sit down if you ask them for a price on any of the materials though :)

you can get away with a fairly thin slab, if you have a large contact area between the hammer and the slab - we scrape the timbers between hammer and slab to give as near 100% bedding as we can (think of a small contact area like a fullering die, it will break down the concrete / metal very quick !)

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Some power hammers need a substantial footing some don't. Rating of hammer weight is not the factor that determines this. I can't explain it as well as the Phoenix Power Hammer page does but it has to do with total mass. My tire hammer weight is about 1000# total with an anvil and base plate weight of about 600#, but is only a 35# hammer. I have no special footing but it does sit on a pad made from 2 x 4s laid flat with a 2 x 2 frame to contain the base. It sits on a standard thickness garage floor (residential construction: circa 1975) No ill effect so far.
Phoenix says even their 500# needs no special footing but again it has to do with total mass. Check out this link for better explanation. Phoenix Forginghammers : What is Cast Iron Fever? It mainly scoffs at cast iron hammers but the important idea is about the anvil mass so read the whole thing.

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that page is a load of total, complete bobbins (the cast iron fever bit) I would trust that no more for foundation advice than I would trust me for knitting advice.

If you dis-credit yourself on one piece of advice information / , how can you expect people to trust you on others ?

(John, @ Johns Hammer emporium, perveyor of some of the finest cast iron (well over 20,000 of em, still industry standard best) Massey hammers... )) -

(im not saying they are bad hammers, but tell me how many of them have been double shifted, tool steel forging for 50 years and still going strong....:)

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I would also call an admixture company that works with concrete, They have all kinds of additives to make concrete work better in different situations. My neighbor has a huge kiln (6, 3" burners) you can walk in it. They mixed some kind of cement especially for the weight and heat. Worth the research.

FP

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My 3b nazel sits on a wood base on my 5" slab floor. It hasn't cracked the floor yet, but I also don't use it every day. it does however pound the floor hard and you can feel it in the house 50' away.

I think alot of it depends on what the ground under you slab is like. At my old shop you couldn't feel the hammer 10' away standing in the shop with the hammer sitting on the same wood beams.

I'm going to be digging a pit and doing a proper foundation soon. Want to use it more often and don't want the neighbours fine china falling of the shelves.

I'm looking at using something like a concrete septic tank. Then using thick rubber bought from an industrial rubber supply place, then either forming a concrete block on top, or possibly a steel box filled with sand compacted and a steel floating cap on top (easy to remove if I ever move to a new shop/house, I had a friend who spent big $$$ on a foundation for a 400lb denmore hammer that had to move 2 years later).

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Chris, The best thing to use is an 'isopolymer cork' along the base, and a void filler (expended polystyrene will do) alternative strips along the base of your 'septic tank', then line the walls of your pit with a void filler, and a capping strip around the top with the cork material.

Seal it all up with duct tape and pour the inertia block. This leaves a 'floating' inertia block when the viod filler disintergrates.

Ive acheived measured 98% virbration attenuation on 3 ton (ram weight) hammers using this technique, its a 10th of the cost of 'spring box' foundation, the absolute best!

The 'cork' can be bought from Fabreeka, or James Walker ( TICO pads) - they charge you mega bucks if you get them to design the foundation (and they disclaim all liability as far as effectiveness goes :mad:, but the materials arent to dear if you know what your asking for.

Hope this helps a little.

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that page is a load of total, complete bobbins (the cast iron fever bit) I would trust that no more for foundation advice than I would trust me for knitting advice.

If you dis-credit yourself on one piece of advice information / , how can you expect people to trust you on others ?

(John, @ Johns Hammer emporium, perveyor of some of the finest cast iron (well over 20,000 of em, still industry standard best) Massey hammers... )) -

(im not saying they are bad hammers, but tell me how many of them have been double shifted, tool steel forging for 50 years and still going strong....:)


To dis-credit MYSELF, I would have to admit I'm wrong ;), so let me clarify. I have no special footing under MY hammer to prevent cracking, because I don't feel it was necessary. The wooden pad MAY be serving that purpose, but that is NOT why I use it. I use it to contain the hammer as, because it is home made, it has a slight balance flaw I haven't cured yet. The pad with the frame seems to help keep it from "walking" in use. There was no threat of the floor cracking, that I could see, before the pad was used. (That was the original issue right? Not, which power hammer is best.) I know the phoenix link is mostly sales hype, and I don't care if its a good hammer or better or worse than cast. Perhaps it was a bad example, in retrospect. I simply wanted to relay the anvil mass issue. I thought that was what I said in the original post. I also said SOME hammers need a foundation, some do not. After re-reading the Phoenix page I have found that on their largest hammers, (1000# +) a footing is, indeed, required. I also agree that if you do pour a footing it needs to be isolated because if it were simply poured thicker under the power hammer than the rest of the floor, it would probably crack around the thicker area, isolating it anyway :)
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Dodge, sorry mate, I wasnt saying one hammer was better than another - it makes no odds to me, 99% of my works in industrial forging - I was just suggesting ways of minimising collateral damage from a hammer! I dont know what the biggest size of Phoenix hammer that has been made is, but suspect its a lot smaller than 1000lbs

The page just annoys me slightly because a) a heavy hammer frame does not make a good hammer, since it aint anvil mass. (a big flame cut is cheaper than a pattern and casting)
Cast Iron can be a superior material for a hammer frame as it deadens the vibration shock loading to the bearings etc in the machine, as we know, steel rings! - specifically calling my companies products 'past it' is beyond a joke, with over 140 years in production, and our machines making many of the parts for eurofighter, JSF airbus A380 etc :o

Steel makes a good anvil, a cast iron power hammer block works much like a cast 'blacksmiths' anvil with steel top, i.e very effectivly. rant over :)

Chris, I use James Walker Group - Machinery mounts (the TICO s pads)

this page has some good info

Fabreeka

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  • 3 months later...

When considering the specs supplied by Little Giant, bear in mind the concrete technology was not quite what it is today. A more shallow isolated footing can be used. And I have cracked 4" thick concrete with a 50 and 100lb LG the first ten minutes or so of operation. It kind of spiderwebs the concrete. It's kind of fun watching the dust jump around till the hammer starts to do it's little dance. Building a new shop now out of an old church. So down where the baptismal font was located is now a great spot for power hammers.

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Can depend on the soil compaction in your area as well.


a point that may not have been stressed enough so far, the concrete is but an intermediary for the force of the hammer, what the soil (or dirt) does over time has a great deal to do with the mass the slab needs to be.

a range that stretches from bedrock requiring no slab to a swamp requiring a concrete boat :P

in the event you have (or someone reading this later) a very poor soil to work with
a very promising foundation technology that is rapidly growing is called rammed aggregate piers
(the main trade name being geopeir) the link explains the concept and its seeing rapid adoption in the construction trades, but its also something that many a smith might be able to replicate on a slightly smaller scale :p
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