# Real life engineering problem-vibrations

DyslexicHobo
I work at a LAN center, and we recently got an In The Groove arcade machine. (http://www.freewebs.com/bhsddr/In%20The%20Groove%202%20dedicated%20cabinet.jpg" [Broken])

It's great, but the only problem is that there is a basement underneath us, and the building is fairly old. When people play on it, the vibrations from them stomping on the pads shakes everything in about an 8' radius. This is causing some of the PCs to be nearly unplayable.

What would be a cheap and effective way to stop the vibrations, if any? Also, if we were to put something under the pads to stop vibrations, it'd be best if it were under ~6" high.

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## Answers and Replies

Gold Member
I don't know what that machine weighs, or how much force is applied by the stomping. You could try putting small-block Chev valve springs between the legs and the feet, but they might be too stiff.

Mentor
How about a platform on a waterbed mattress on the floor? Alternately, one of those matresses that advertises on TV showing a glass of wine not tipping over while a bowling ball is bounced right next to it?

jaap de vries
How about a platform on a waterbed mattress on the floor? Alternately, one of those matresses that advertises on TV showing a glass of wine not tipping over while a bowling ball is bounced right next to it?

I always wondered who would watch those!

I don't know what that machine weighs, or how much force is applied by the stomping. You could try putting small-block Chev valve springs between the legs and the feet, but they might be too stiff.
Even though they may be stiff, you are still adding compliance on top of the floor which is already moving, which is something the OP doesn't want. The thing to do is to somehow stiffen the floor structure from below in the basement. Do you have access to the floor joists from below? I would sister some extra floor joists to the existing ones in the area. You may also have to look at a temporary support post or two under the floor as well. They are pretty cheap and you can get them at a Home Dept or the like.

http://www.hammerzone.com/archives/framecarp/supplement/floor/joist1/sister.htm
http://www.ashireporter.org/photos/get_tiny_photo.aspx?s=580&p=2006_02/alcan.gif

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DyslexicHobo
Even though they may be stiff, you are still adding compliance on top of the floor which is already moving, which is something the OP doesn't want. The thing to do is to somehow stiffen the floor structure from below in the basement. Do you have access to the floor joists from below? I would sister some extra floor joists to the existing ones in the area. You may also have to look at a temporary support post or two under the floor as well. They are pretty cheap and you can get them at a Home Dept or the like.

http://www.hammerzone.com/archives/framecarp/supplement/floor/joist1/sister.htm
http://www.ashireporter.org/photos/get_tiny_photo.aspx?s=580&p=2006_02/alcan.gif

Wow that's a really interesting idea. I think we might be able to get access to the basement. No one really uses it; it's just filled with cobwebs and dust. I'll definitely bring that up to my boss. I don't really think he'll want to do something that expensive or tasking, but it may be good if nothing else works.

Right now we decided to put some high-density gymnastics foam under it, but the only problem now is that it feels very springy. Some people who play on it complain a little, but it isn't quite unplayable.

Thanks for the suggestions!

Also- a question about the spring idea. Would it make any difference if we got 4-8 high-tension springs and put one under each foot, or if we took many lower tension springs and sandwiched them between two boards?

It seems like they would do the exact same thing, but I wasn't sure if they would both tilt the same amount or not. Also, instead of springs I was thinking that rubber would be a better solution.

Code:
############
OOOOOOOOOOOO
# = plywood
O = rubber mat

Would this work well? We're trying to make it as cheap as possible while making it feel to the players as nothing is different (we have some very picky people who are very skilled at this game, and they will only settle for the best!).

Thanks! :D

Edit: Oh yeah, the pads weigh about 75lbs each, so 150lbs total (just a guesstimation from when I helped lift them) that will be supported without taking into consideration the weight of the person(s) playing.