Inertia Base

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Gold

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This is a inertia base I'm making for my lathe. When I moved into this space thirteen years ago the neighborhood was much quieter. Now there are idling trucks outside the building often. The building has foot thick concrete floors and I'm on the fourth floor so it wasn't much problem previously. Now it is. I'm using 80/20 T-slot framing to make the main frame. I'm using 1/4" mild steel angle iron for the brackets. It looks fairly simple and straight forward. It took me a long time before I was able to boil it down to the essentials. I've completed the dry run. I will install in in a couple of weeks when I have a chance. Here is a top view. The equipment feet are for the lathe.

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Here is a side view with the spring isolators.

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Making the brackets was the trickiest part. You can see I put the first mounting hole in a less than ideal place. I used the upgraded 1HP motor on the Tail Micromill to drill the holes.

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Gold

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I put in the second set of springs yesterday. The front right corner still isn’t right. I’m not sure why. The load seems so unbalanced but is turning out to want equally spec’d springs at each corner. Kind of embarrassing.
 

JohnRoberts

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That is the nature of fresh design, if something doesn't work, back up and make adjustments.

This far more interesting than the latest clone of XYZ.

JR
 

Gold

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That is the nature of fresh design, if something doesn't work, back up and make adjustments.

This far more interesting than the latest clone of XYZ.

JR
On a brighter note I had a success with replacing the foam isolation pads for the Lyrec motor discussed in here Reducing Ampex 440 wow/flutter on playback

The foam motor mount pads had dried out. Instead of spending hours looking for the right part I decided to try to punch my own. I sharpened a steel pipe and cut out the foam pieces. Then I thought that sorbothane would be a better material than closed cell foam.

i went to the sorbothane website and used their calculator to figure out the right hardness for the weight of the motor. The sorbothane is more difficult to cut. I got the pieces cut out.

I hadn’t maniacally leveled the motor so there was more vibration than usual. The sorbothane motor mount pads plus pads under the feet of the frame killed any vibration I could detect.
 

Gold

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The third set of springs came last week. I was able to put the new spring in the housing today. Works like a charm. Everything is level now and the floating aspect feels tight like it's correct. Most of the spring inertia bases I've run into have been loosey goosey. Including the one I was using at a different location next to a raised expressway. I'm glad I took the time to get this right.

I made a recording of unmodulated groove before I broke down the lathe to install this inertia base. Tomorrow I'll make another recording of unmodulated groove and compare the two. I noticed even with one corner propped up on a block and the rest of the inertia base floating there was increased isolation.

InertiaBaseFinal-1.JPG



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InertiaBaseFinal-3.JPG
 

cyrano

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Ah, it's a vinyl lathe...

Impressive and interesting.

I helped my cousin (who's a retired engineer specialised in lasers) build a similar setup for a laser measurement thing. We ended up using two inch thick steel plates with numerous holes and tennis balls in these holes. The problem was also vibration caused by traffic...
 

Gold

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Ah, it's a vinyl lathe...

Impressive and interesting.

I helped my cousin (who's a retired engineer specialised in lasers) build a similar setup for a laser measurement thing. We ended up using two inch thick steel plates with numerous holes and tennis balls in these holes. The problem was also vibration caused by traffic...
Twenty years ago I moved into a space in a record pressing plant that was half a block from a raised expressway. When I set up the lathe and played back unmodulated groove the rumble was so bad the meters were hitting +1dBu. I had a big problem.

I knew nothing about vibration isolation but I knew I had to learn. The spring isolators we got must have been spec’d for a lot of weight. We had a 1” steel plate and a 5” box of sand on it and it was still loose. It worked well enough to cut.

I ‘ve been thinking about the best way to do this for a while. Although it looks straightforward there were a lot of little decisions and details. The simplicity was the result of a lot of thoight.
 
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