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Dane Lance

Power hammers and cement slabs

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Hello!  Newbie here and I have questions concerning power hammers.

I've read/heard elsewhere that you can't really run a power hammer on a cement slab as it will crack it?  Is this true for all power hammers, or only for those over a certain weight?

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You can safely run most mechanical hammers up to 50 pounds ram weight on a 4" slab with no problems as long as there's a solid base under the slab.  You can run larger hammers on a 4" slab if you "float" them on a timber raft of 4x4s bolted together.  Up to a point, of course.  Anything over 150lbs needs an isolation pad/separate foundation slab for best performance.  How big depends on the hammer.  If you're buying new the maker will have plans for this.  If you're buying used, you might be able to find recommended sizes somewhere.

 

How big a hammer are you asking about?  Something like a 25lb Little Giant can be run on almost any surface once bolted down to keep it from bouncing around the shop, while a Nazel 5B needs a block about 5 feet wide by ten feet long by three feet deep, preferably mounted on short heavy springs, with a 1" gap filled with rubber around the sides.

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The big hammers like Nazel pretty much all had separate foundations.  OTOH, my homebuilt 50# has been on a platform of 4x12 timbers since 2000 and never cracked the floor.

 

So the answer is, it depends.  It depends on the weight of the hammer, the construction of the floor, and the construction of the base, and probably other things I haven't thought of.

 

Geoff

 

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Thanks guys!

I'm not in a hurry for a hammer, but when/if I go that route, I'm thinking something light.  Before I go with a hammer, I want to get a press and I'm considering converting a log splitter.  I know, it's not optimal, but I just can't justify the price of a commercial forging press.  This is, after all, a hobby.  

 

I'm not sure what you'd call the technical term for it, but  I figure the press will do the grunt work, hand hammering to straighten, and then a light power hammer to smooth it out, if that makes sense.

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It's been a few years but there was a WIP on installing some huge industrial power hammer in a barn where the smith had to put in a five foot thick rebar reinforced isolated bed to mount the hammer on to keep it from shaking the barn down.  I always have wondered what happened with that setup.

 

Doug

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I have a friend who bought a 300# Beaudry to put in his shop.  Even with a separate 10x10x10 pad of concrete and RR ties, it would make stuff jump off the bench when it hit.  Scary!

 

Geoff

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A big one, I think it was 3ph.  It was about as big around as a beer keg.

It was like this one, but a 300# not a 150#

See the source image

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Didn't Salem Straub rebuild one of those recently?  Nice hammers, anyway.  My 50lb Star sits on a raft of 4x4s anchored to the slab, and while it doesn't make stuff jump my wife does say she can feel it 20 feet away and not on the same slab.  Hammers are noisy and shake stuff, it's the nature of the beast. Presses are noisy and don't shake stuff,  but they're so much slower than hammers at drawing out.

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While I do live in the country, I sort of have neighbors.  Not sure how well they'd like a lot of pounding from a power hammer every weekend.  Then again, their kids blast around on really loud ATVs almost every day.  

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It's not that they will hear it, as much as feel it.  The sound travels through the ground in the sub sonic range.  It's a low frequency pulse.  My hammer is 250 feet from the house and you can sort of hear the thump.  It's "only" a 50#er, a big hammer makes a bigger thump.

 

Geoff

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My 88 lb self contained hammer has a metal base that it was supplied with the hammer and I have it bolted directly to the concrete. My shop is an  attached 2 stall garage and I have shaken things off the counter in the kitchen.my pad is a good 4-5 inches thick and I haven't had any issues with cracked concrete. My 85 lb hammer I built was on a bundle of landscape timbers and 2x12's a d I had it in 3 different garages and never cracked any of the cement pads.

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22 hours ago, Alan Longmire said:

Didn't Salem Straub rebuild one of those recently?  

I think so.  He had some videos up of it running.  Drool....

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