Resilient mounts.........bouncy bouncy!

[George A]

I successfully moved my 6/1 generator to the shop yesterday with aid of "Gerty", my ancient and wheezing fork lift. I rolled it into its final position and used my home made jacking gear to raise it slightly, remove the casters and then lower it into its resting place. Before lowering however, I placed two wide strips of horse trailer matting (3/4" recycled tire material) under each runner. I double checked all of my measurements to make sure it was square to the walls, then spun 'er up.

Now, when mounted on the casters and on a concrete floor it had behaved itself very well, so what happened next really surprised me.

With the first firing impulses, my ordinarily calm Listeroid began moving so I shut it down. The entire assembly.......engine, generator, radiator and control box (probably close to 1000 lbs).......had moved almost 2" with the first few strokes of that big piston! Once it settled down to its normal rpm's it decided to stay put, but it sure wasn't what I had in mind.

So, I'll jack it up again and put some pipe rollers under it to move it back to position. Then those horse mat strips are COMING OUT. I'll start it again and see if it still has any "wanderlust", but I have a feeling I should lag screw it to the floor (heavy planks) to keep it in one place.

Moral of the story? The only way to find out if something is going to work is to try it.........but have a backup plan. 

[mike90045]

I too, had tried a stall mat.  Very tough rubber, no give to a human foot, but without a tether, mine wanted to walk too.  Ended up using some hardwood flooring strips (1/4" oak) under the runners and then clamping the tops to bolts epoxied into the concrete.

[George A]

Good solution! Unfortunately, my shop floor is 2 x 8 tongue and groove planking, laid over 4 x 6 beams, 3' on center. It's a heck of a stout floor and holds a lot of machinery, but I think something like a lag bolt would strip out over time. Can't get easy access to the underside in order to use bolts either, SO, I decided to try something else....

I'm going to weld up some 2" angle iron to form a "U" shape that will wrap around the end of each of my runners. These angles will be lagged to the floor in at least six places each. The problem isn't hopping really, it's that during initial start it wants to move across the floor several inches. By containing the runners I hope to "corral" it until it settles down to its normal running rpm.

If that fails I'll cut down through the floor, build a form and pour about a yard of concrete!  

[BruceM]

If you score thick rubber on both sides with a saw blade, gorilla glue will then suffice to hold it in place to wood or metal.  I used some 3/4" thick pads under my wood frame, glued to floor and frame. Worked fine, still no problem many years later.

The fear about lag screws failing is overrated. My lags holding the engine to my temporary (Douglas Fir) wood frame are still holding fine and haven't needed tightening since a hundred hours of running, now near 3000 hrs.

Failed bolts/lags are what you get when you ignore a jack-hammering, out of balance machine, instead of correcting the external balance.

Just my 2 bits.

Best Wishes,
Bruce

[xyzer]

George,
These Listeroids had a 2X4 runner on each side and a lot of work went into getting balanced. They originally would shake my 5000lb Kubota if I tried to hold them in place with the bucket. After I got them to behave I found moving them brought on the movement you described. Shuffle off to wherever then find a spot to settle down and then no problem. They can't be setting uneven on the corners. If the floor is not flat it will do it. With the cast iron piston and the extreme weight to keep it from hopping it takes to the edge of shuffle. I would recommend fastening to the floor no matter how well it behaves. A runaway or large speed variation may take it to the next county.

https://www.youtube.com/watch?v=eOxPXGn6BWo&feature=relmfu

[George A]

Thanks for the advice guys............my Vidhata seems to run quite well balance wise (thank God), without any effort on my part. As for lag screws, my problem is more to do with sideways motion than vertical "pulling" of the fasteners, so if I have to lag it to the floor I'll do so. If you have an engine that "hops" badly they're probably going to pull loose eventually.....but I doubt if they'd ever actually shear. In other words, reasonable balance is the key here. If you have an engine that behaves badly at normal rpm's in the first place, no amount of fastening is going to be really satisfactory.

The tip about a level floor is a concern here and I'm glad you brought it up. Even though I made a concerted effort to make my floor level, I did find one corner that required metal shims. The "containment brackets" I described will keep the machine in one place and also hold the shims.

Anyway, today is Sunday and our steel supply is closed so I'll buy the angle tomorrow and get the brackets welded up, then report back in a day or so.

[ronmar]

Yep, if there is an inconsistency in the base to floor contact, it will walk due to the torque pulse alone interacting with the contact points, it will be worse if it is not at optimum balance😋

Mine runs fine setting atop a horse mat, but it also has about 1200# of concrete between the mat and the engine frame...  This gives a lot of surface area to engage the mat material, but I found when I re arranged my generator room to add another generator, I found that my floor was not as level in the new location and I picked up a little movement(didn't walk but wobbled).  I had to move it out of the way and do some work on the floor to get that squared away.  The problem with resilient mounts is that too much or too little are options:). Mass makes things less sensitive

[George A]

Well, I just finished a frustrating afternoon learning what NOT to do. I went down an bought some 1/2" lag screws, drilled into my floor and bolted that baby down tight. Then I fired it up. To my astonishment it stayed in place but vibrated enough that I could see my floor moving at one corner of the frame! I dropped the rpm down to around 525 and most of the nasty motion went away.

At this point I really considered using a smaller generator pulley just to keep the rpm's down, but then I'd probably have governor problems on top of the horsepower loss.

I finally decided to put my casters back on. When I initially tested this whole rig in my garage....on the casters....it behaved very well, so why not just put them back on and see what happens? This took about two hours of jacking and reattaching the things before it was ready. I fired it up and it seemed to be okay at first, then started the infamous "kangaroo" dance. I hit the fuel cut off and sat down for a while to ponder.

My original test runs were done in my garage, with a CONCRETE floor. Although the generator was on casters, the concrete gave a smooth, firm surface. Even though the floor is very slightly sloped for drainage it sat in one place. Hint: the floor had no "bounce".

Okay......now the shop floor.
First of all it's not level where I set the generator......had to shim one rail end about .035" or so.
Second, it may be a dandy wooden floor capable of supporting great weight.....but it's still flexible. So any repetitive vertical motion is "amplified" minutely  until it mimics a trampoline, and the engine starts hopping. I would imagine the action would get so bad the whole thing could leave the floor an inch or so.

I'm going to fall back and regroup. I considered cutting a hole in the floor and pouring a yard of concrete, but there might be another option. I have a small driveway approach pad behind the shop and the rig might be happier there, ensconced in its own little shed!

LATE PM UPDATE: It's the floor.......no doubt about it now. I rolled the entire unit to a portion of the shop floor that is known to be reasonably level and rigid (or so it seems). After starting, the engine came up to speed and seemed to be doing better..........then I felt a slight thumping begin under my feet and within seconds the engine was dancing to its own beat. I shut it down and rolled it back into the corner.

Tomorrow I'll fire up 'ol Gerty (fork lift) and move the Listeroid out to the concrete pad behind my shop. I'm really curious and want to start/run it again while it's sitting on the slab with just the casters. It might make all the difference in the world and all I have to do is build a small shed. Stay tuned!

[BruceM]

It's pretty easy to adjust the balance for your final floor and operating rpm.  Lot's of old threads on it, see the Mr X method for the rough balance.

An hour with a box of clay should do it.   4 oz increments work well.

[38ac]

The power pulses during start up, operating power pulses and running balance are three separate issues. As you have found what the engine is sitting on can have a considerable affect upon "reasonable" balance and power pulses. This is why when we are balancing in the shop we set the engine on a small steel wheeled cart, if it sits well there its going to sit anywhere. Any type of moving mount is going to magnify imbalances at Listeroid operating RPM, not smooth them
When boiled down to the simple you have two choices, mass under the engine, or engine balance.  Not sure how good your engine balance is but as with the other posters I am a fan of getting the balance right if for no other reason that stresses on the engine are increased by many times when an unbalanced engine is forced to sit still on top of a ton of concrete.  The pounding also is transmitted to the ground where it continues to annoy the sensitive.
  These videos will give you something to shoot for as they show what can be accomplished with balance. The engines will sit still unless placed on a slope and heavy load is applied (power pulses are another matter) You will notice just a bit of shake in the DES engine but look under it, this engine now sits perfectly still on my buzz saw frame.

Butch
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[George A]

Butch, you summed it all up. My engine runs VERY nicely on it's wheeled cart when sitting on a hard (concrete) surface....very much like your DES...and that's with the generator fully loaded, so it's not a balance issue. Once placed on that wooden floor, the engine pulses quickly became magnified, each one feeding off the others, until it started it's hopping routine. The only analogy I can come up with is to place a running Listeroid on the head of a snare drum....seems firm enough, right?....then stand back.

After some measurements last night, my generator won't fit on the pad behind the shop without blocking the wife's riding mower access to the yard  . So, it looks like I'll take the whole rig back to the garage where this saga started, HOWEVER, that may be a blessing in disguise. There is an existing (abandoned) electrical feed from inside the garage to the main panel on the back porch. Rigging up an electrical inlet for a generator plug in the garage and a circuit breaker lock out should be a snap. In case of need my new "portable" Listeroid generator can be wheeled out, fired up and plugged in within minutes.

In any case I really appreciate the comments and suggestions from everyone. I realize now that I was trying to reinvent the wheel and all of you have been quite patient with the whole process. I did learn however.........!  

Thanks guys.

[38ac]

George,
If it was easy they would have sold Listeroids at Home Depot .

 Takes a special breed of which you are one!

Butch

[Tom]

Wow what a ride. Glad you've got it worked out. Yea the power pulses are a whole nother issue. My CS6/1 runs fairly smooth under load and moves around a bit while lightly loaded. George, another option if you still would like to use that wood floor is to build a heavy timber frame on the floor that will transfer the load directly to the joists instead of just bouncing on the floor.

[BruceM]

Resonance with the supporting structure can be a real shocker.  My engine/generator which was pretty well behaved on my wood base on a sidewalk during initial testing, with just a little tendency to scoot.  When moved into my dedicated 10'x10'engine shed, with 10" of concrete under the same engine frame, and some 3/4" rubber pads under it, the whole building would shake and the metal siding buzz.

Changing the counterbalance weight solved it- you just need to retune the balance to stop the bounce.

I'll bet with about a pound of clay you could get it to sit nicely on that wood floor, but I hope you enjoy it wherever you decide to make it a home.  Congrats on getting one of these wee beasties put into service!

Best Wishes,
Bruce