Lister(oid) Concrete Base

[veggie]

Thanks sailaway,

So, you poured a ~6 inch thick slab and then soft mounted the generator frame to the slab.
How does it perform? Did it control the thumping as you expected?
I would love to see a video of that unit running. 

I'll take some time to study your methodology and calculator.

Cheers

[Randybee1]

RandyBee1,

The isolators I currently use are made by Karman and were purchased through Acklands/Graiger.
Below is the drawing I made to incorporate the Karman isolator into my engine base design.

Also below is the softer "Navy" isolator I was intending to try on the listeroid.They are from Lord Isolators.

I should note that the Karman isolators were marginal in perforance. They did prevent my garage pad from cracking but they still allowed a thumping force to travel through the ground to my house.
In the case of Changfa type engines, the cylinder is horizontal so the combustion forces are sideways vs. vertical like the lister, so ground thumping is eliminated.

Veggie.... Much Appreciate the info. Randy B

[veggie]

Hey guys,

How's this for a generator base. Actual old Lister installation.
I looks like concrete mass (and lots of it) was the way of controlling vibration back in those days.

<click picture to enlarge>

[sailawayrb]

Thanks sailaway,

So, you poured a ~6 inch thick slab and then soft mounted the generator frame to the slab.
How does it perform? Did it control the thumping as you expected?
I would love to see a video of that unit running. 

I'll take some time to study your methodology and calculator.

Cheers

Yeah, someone contacted me and said you were working a problem I solved 20 years ago...  I don't waste my time on social media any longer but I figured I would help you.

I posted photos and a video on this forum 20 years ago, but it  looks like none of these exist anymore.  We are currently at our second home in NZ so I won't be able to post another video anytime soon. There is some minor rocking of the upper stand that engine and generator are bolted during startup.  However, once the engine reaches 650 RPM, there isn't any perceptive motion at all...and there shouldn't be if the isolation stand was properly designed. There also isn't any vibration transmitted to our southern OR shop at all.  And this was also the case for our previous Seattle area shop too since the isolation stand eliminated 96% as measured using a piezoelectric accelerometer vibration meter.  I constructed this additional concrete slab largely to raise the engine height for easier starting and maintenance.

This additional concrete slab is a 6 foot long x 4 foot wide x 8 inch thick pre-tensioned and highly reinforced concrete slab base resting on a 1.5 inch thick dense rubber isolation pad in corner of our southern OR shop floor and it eliminated the last 4% of vibrational energy that the original isolation stand we had in our Seattle area shop didn't.  More details and photos may be found here if interested:

https://www.borstengineeringconstruction.com/Lister_Engine_Photos.pdf

Bottom line, one needs to specifically design an isolation stand for the specific setup which includes the locations and weights of everything on the stand and the disturbing frequency which is 10.8 Hz for a 650 RPM Lister 6/1.  20 years ago I built this calculator to help those capable and interested in doing this:

https://www.borstengineeringconstruction.com/Isolation_Stand_Design_Calculator.html

Anyhow, all the best and good luck with your project!

Cheers,
Bob

[sailawayrb]

Duplicate post Deleted

[veggie]

Bob, thanks for that explaination.
Just to be clear ... you did not anchor the system to the shop floor?
It's just resting on the rubber isolation pad, correct ?

Nicely done !   

[sailawayrb]

Bob, thanks for that explaination.
Just to be clear ... you did not anchor the system to the shop floor?
It's just resting on the rubber isolation pad, correct ?

Nicely done !   

Correct.  Didn't anchor it to floor in either location. There's no need if the isolation stand does its job.

[veggie]

Bob,
The calculator and instructions were very helpful. Thanks
You did some great work with your system. A most impressive installation.
The issue am having is twofold.
1] I can't find data on my various insulators for in/lb load ratings in order to use the calculator so I had to estimate.
2] I plan to run the engine at 375 rpm constantly charging batteries. A speed of 375 rpm gives me an excitation frequency of 3.125 hz and the majority of the isolators I have access to all have a natural frequency of 7hz to 8hz.

All the guides I have studied recommend that isolators should have natural frequency of approx. 0.5 that of the excitation frequency in order to force them into the proper performance zone..

Natural Frequency vs. Excitation Frequency:
For effective vibration isolation, the natural frequency of the mounting system (where the engine is attached) should be significantly lower than the engine's excitation frequency.
Frequency Ratio:
Aim for a frequency ratio (excitation frequency / natural frequency) greater than 1.5 to 2, to ensure the vibration isolation system is working in the vibration reduction area.

So I have a mismatch problem for my low speed application.

Trial and error with soft mounts is a lot of work when mounting a 6/1, so I am still considering a solid mount with a 1600 lb base block as recommend by Lister.

I also invite other users to pipe in here and let us know what worked for you ( whether a solid mound or a resilient soft mount) What worked for you ?

[Hugh Conway]

Veggie
I have my listeroid mounted to a block of concrete About 3' W X 6'L X 1'D on top of that are two  8" X 8" Fir beams. The mount bolts go through the fir beams and into the concrete. The engine and generator are mounted to a heavy welded up frame that is lag bolted to the fir beams. You could still feel the vibe in the surrounding area. That set-up a fair job for 11 years until I finally got around to balancing the flywheels using the method that was posted here by Butch many years ago.
Now there is no vibe to be felt and you actually can put a glass of water on the stamped metal valve cover while it's running and the glass stays there!
So, perhaps good balance is the key....it is at least very helpful......though Lister advocated the use of a large and heavy block of concrete as a base.
Cheers
Hugh

[BruceM]

I concur. Using 38AC's balancing method is fast and effective. So much less work and expense than designing a base for a jackhammer.

[veggie]

I concur. Using 38AC's balancing method is fast and effective. So much less work and expense than designing a base for a jackhammer.

Please expand on that BruceM. Even a balanced Listeroid has vertical forces from the power strokes.
What mounting method did you use for your balanced machine?

In my case I am mounting just the engine (not a generator frame). My alternator is mounted on the engine.
I could construct a small heavy wood beam frame or a metal frame if having a slightly bigger footprint would aid in the prevention of the "rocking" forces created with bare engine mountings.

[veggie]

Here is what I am thinking of doing if I rigid mount the engine (picture). Although I would prefer to soft mount it.
I could be over thinking this installation, but as I noted earlier, the engine has just been removed from the previous installation because of thumping forces making noises in the house. This new application is located off grid but it's still beside a cabin (5 feet from the building wall) so I wanted to make it as quiet as possible.
It is located close to the building due to the limited wire size and distance for a 24 volt system.
The engine alternator will drive a DC-DC charger to charger a Lifpo4 battery bank.

From the discussion in this thread I am concluding that there are two options:
1]Soft mount close to the building and eliminate most ground thumping
2]Rigid mount far away from the building where thumping would not be an issue
It's just the nature of these engines.

Oh, and option three ... rigid mount beside the building and tolerate any thumping 


The issue with soft mounting the engine is that you have to get it right (type of isolator) or the engine jumps and bounces. This is why I was asking any who had luck "soft" mounting their Lister to pipe in an explain how it was done.
Simply using any rubber mount without knowing it's characteristics could create situations like this... which could be destructive to tubing and other components over time.
https://www.youtube.com/watch?v=SbqWkVC84bQ

[BruceM]

If you add counterbalance until you just barely start to see fore and aft movement, that will be the ideal weight if you are looking for minimum vertical force.

I had built a temporary wood frame for my Listeroid, which I mounted on 1" thick rubber pads (grooved and glued in place with gorilla glue) on a thickened shed slab- 10 inches thick under the engine area.  Without balancing, despite the rubber pads, it audibly shook the whole steel sided and roofed building and you could feel it through the ground 10 away from the building.  I then used the wheel marking method, which took an entire afternoon of fiddling.  Then I could sit a cup of water on the valve cover and just see some rippling.  On my next engine project for a neighbor I used 38ACs method of matching the flywheels and getting the counterweight centered on the keyway first before adding counterweights.  This made it SO much faster and easier. Maybe 20 minutes to that perfect balance where fore/aft movement is just barely starting and a cup of water is used for the final balancing. The beauty of his method is you just add/subtract counter weight equally on both wheels, and then observe the balance.  It is only a question of too much or too little and you will be using the cup of water pretty quickly.

The only reason for a big slab of concrete is if you'd like to raise the engine for ease of service.  Or you have failed to understand 38ac's simple method.  It's brilliant.

For your new post- I'm not a fan of low voltage systems for just the reasons you state.  But there, balance will be very important.  Some sort of soft mount may help, the ulitmate being sailawayrb's properly engineered system. You will still have sound issues with valve clatter, and will need an earth muffler of some sort.  I like the leachfield exhaust method in a dry location as it also gets rid of exhaust smell.

[veggie]

Thanks for that explanation BruceM.
I too prefer the high voltage systems but in this case I want the freedom of running the engine at any speed I choose. Also I no longer have access to steel and welders in order to build a new generator base for an AC alternator. So I thought I would try the integral Engine/DC-alternator design.
My GM90 type listeroid is different than yours. The GM90 engines have a counterbalanced crankshaft and the flywheels do not have counterweights cast into the periphery like yours. The Wheels are uniform casings and have been factory balanced with drill holes in the outer ring. How well were they balanced I think I will have to remove them to find out.
If I find that they are unbalanced then there is a good chance that I can use a more simple rigid system after they get balanced.
If they are already balanced quite well, then I will continue to research methods of isolating the thumping.

This picture shows the 20" flywheels (not 23" used on 6/1 Listeroids)
Also you can see the elastomer vibration isolators that do a marginal job of reducing the thumping.

[sailawayrb]

Bob,
The calculator and instructions were very helpful. Thanks
You did some great work with your system. A most impressive installation.
The issue am having is twofold.
1] I can't find data on my various insulators for in/lb load ratings in order to use the calculator so I had to estimate.
2] I plan to run the engine at 375 rpm constantly charging batteries. A speed of 375 rpm gives me an excitation frequency of 3.125 hz and the majority of the isolators I have access to all have a natural frequency of 7hz to 8hz.

All the guides I have studied recommend that isolators should have natural frequency of approx. 0.5 that of the excitation frequency in order to force them into the proper performance zone..

Natural Frequency vs. Excitation Frequency:
For effective vibration isolation, the natural frequency of the mounting system (where the engine is attached) should be significantly lower than the engine's excitation frequency.
Frequency Ratio:
Aim for a frequency ratio (excitation frequency / natural frequency) greater than 1.5 to 2, to ensure the vibration isolation system is working in the vibration reduction area.

So I have a mismatch problem for my low speed application.

Trial and error with soft mounts is a lot of work when mounting a 6/1, so I am still considering a solid mount with a 1600 lb base block as recommend by Lister.

I also invite other users to pipe in here and let us know what worked for you ( whether a solid mound or a resilient soft mount) What worked for you ?

I also fully concur that mounting a 6/1 on a massive block of concrete is the easiest and time tested approach.  If I didn't need to originally operate our 6/1 inside our attached garage in a housing development where stealth and safety were critical, that's likely what I would have done. 

With regard to the 6/1 engine design, Lister was pretty ignorant relative to machine design engineering knowledge and application today.  Lister compensated for their knowledge shortcomings by designing massive engines mounted on massive concrete.  I felt that unbalancing the fly wheels to compensate for an unbalanced piston arrangement wasn't the best approach...or in more simple-minded terms, two wrongs don't make a right...  In fact, I dynamically balanced our 6/1 fly wheels in a similar fashion that car wheels are balanced today...with the objective of reducing vibration and increasing component life.  And with component life also in mind, I didn't want the forces created by the 6/1 unbalanced piston arrangement to remain locked within the engine by concrete either.  So, with all this in mind, being a mechanical engineer and given our original location requirement, a resilient engine mount provided the required solution and was relatively easy for me to successfully accomplish.

Anyhow, that's what I did and my rationale for doing it.  As detailed in the previously provided links, I had to put the isolators in series (i.e., a two tier, 8 total isolator design) to achieve the required isolation performance given the specifications of the available isolators.  So just know that it is always possible to design a proper isolation stand by using some combination of isolators in series or in parallel.  But yeah, an isolation stand does require math and much more thought than pouring lots of concrete.  For better or worse, that's how my mind works and what I have done my entire life.  If you want a headache, give this a read sometime...

https://www.borstengineeringconstruction.com/AIAA-74381-139.pdf

All the best however you proceed!

Cheers,
Bob