Rubber Engine Mounts - Listers vs. Small Engines

[Mikofox]

I read most of the posts regarding bolting down a Lister to a concrete slab or other heavy base and it makes complete sense.
It appears not many think it neccessary to have some kind of rubber shocks between the engine and the base.
My neighbor, who has used many Diesels during his mining career, argued that if they are bolted to concrete, the vibration, will destroy the engines internally. Is there anything to this?

I have had several generators with small 3600 RPM engines. All mounted with rubber engine mounts. My firepump has no mounts between the frame and engine, but some more or less effective rubber feet under the frame. 
What are the rubber shock mounts really preventing in a direct coupled high RPM generator application?

If I were to couple one of these 3600 RPM engines with a spider coupling (Elastomer Jaw Coupling) to an alternator, could both be bolted tight to a frame and then have some rubber shocks between the frame and the ground?

[GuyFawkes]

I read most of the posts regarding bolting down a Lister to a concrete slab or other heavy base and it makes complete sense.
It appears not many think it neccessary to have some kind of rubber shocks between the engine and the base.
My neighbor, who has used many Diesels during his mining career, argued that if they are bolted to concrete, the vibration, will destroy the engines internally. Is there anything to this?

I have had several generators with small 3600 RPM engines. All mounted with rubber engine mounts. My firepump has no mounts between the frame and engine, but some more or less effective rubber feet under the frame. 
What are the rubber shock mounts really preventing in a direct coupled high RPM generator application?

If I were to couple one of these 3600 RPM engines with a spider coupling (Elastomer Jaw Coupling) to an alternator, could both be bolted tight to a frame and then have some rubber shocks between the frame and the ground?

there's vibration and there's vibration....

your diesel mate is correct, _excessive_ vibration does end up as things like cracked crankshafts.

increasing the mass to be vibrated massively by bolting an engine to a ton of concrete will damp the vibes, but it won't remove the forces acting, so you're back to vibration or vibration.

I have never seen or touched a listeroid, so I can't say anything helpful about them, but I can tell you a genuine lister 6/1 sat on a smooth concrete floor can be started up, it might "walk" slowly and you might get a feeler gauge between the case and the crete when she "whumps" but that's it - obviously under load she'll whump more

so you need to work out if you got vibration, or vibration.....

I think I need to do another short video to give you guys some sort of baseline.

[kpgv]

I also think that, in the case of your "Startomatic", the dedicated cast iron "chassis" that they came with helps a lot.
Cast Iron being the key ingredient, as there is a definite "damping" it provides.
One more thing that we "Roid" owners don't get in the "kit", and need to compensate for.

Kevin

[WWIProps]

My first installation had  a wooden frame with angle iron support like the one shown on Georges website.  I used spring mounts from Grainger initially, it had significant bounce and vibe. 

I then took the same wood and metal frame and bolted it to the floor with the supplied J-bolts and 3 layers of truck tread donuts between the floor and the mount.  Less vibe but metal frame cracked and 3 of the 4 J bolts sheared off at the point where they exited the concrete floor.

Now I have a frame with two rails of 4" x 4" square tube steel held apart by 2" x 4" rectangular steel tube.  The steel was drilled, wood plugs put through the holes, and the ends were capped.  I then filled everything with concrete.  The engine and generator are firmly bolted to the frame.  New  3/4" J bolts were put in the floor and the whole assembly was bolted down on top of 3 layers of truck tire donuts.  It works great.  The little extra mass of about 150 lbs plus the stiffness of the material has really calmed the machine down.  Measureing at the bolt for holding the valve cover on I get around 1/32" of motion.  I am very happy with this new setup.

Scott

 

[Mikofox]

I'm still trying to find an answer for the question I had asked regarding portable generators.

I have had several generators with small 3600 RPM engines. All mounted with rubber engine mounts. My firepump has no mounts between the frame and engine, but some more or less effective rubber feet under the frame. So why can't the engine and generator head be bolted down solid to a frame and then dampened with shock mounts towards the ground or a base?
What are the separate rubber shock mounts under the engine and the far side of the head preventing in a direct coupled high RPM generator application?

[trigzy]

Maybe not a direct answer, but here it goes:

1) All my portable 3600RPM Gens have Rubber mounts all the way around.  (ie. On the engine and the genhead)
2) These rubber mounts greatly absorb the diesel bounce, and without them, I'd think the whole thing would want to walk away at a low RPM.
3) Most circuit breakers/switches/relays HATE vibration - you can bet your life they'll fail/open/weld shut faster if they are on something that vibrates.
4) A bare engine sitting on the ground wont want to walk to far at high RPM, but will jump around at a lower RPM.  This gets more proncounced as the load increases 

(Experiment: Put your car in 5th, slow down to about 200-600RPM depending on the car until you get some strange sounds - push accelerator to the floor - notice the strange sound/vibration is much more intense)
(Experiment #2: Watch a Transport truck accellerating, preferably when the driver is "just giv'n 'er"  The whole truck will rock to once side when power is applied, and the same is happening in smaller engines as well.)

The slower your accelleration/decellerations are, and the closer you stay to an engines designed RPM, the less the rubber mounts should be an issue.  As your gen goes from No-Load to Full-Load - they're would be a hesitation for it rock over to one side, and that's what the rubber mounts are for on the 3600RPM units.  Because of the large amounts of rotating mass in the Listeriods and the generators, and maybe some help from a slow governor, these generators dont seems to have as much of a problem.

The pumps dont have them because they are more of a constant load on the motor, that's why the manuals specify not to "hammer" the water system by rapid opening/closing of valves.

Steve

(Edited to fix inaccuracies caused by brain-farts)

[Mikofox]

Thanks Steve, some good points.
I'm going to couple a regular shaft engine with a jaw/spider coupling to a gen head that will be converted from one to two bearings. I intend to bolt the engine and head to a subframe and then dampen towards the main frame. I'll make sure the electrical panel goes either on the wall or main frame with some shock mounts. This will be a standby unit only, while I'm getting into the 12/2 project.