General Category > General Discussion
concrete vs resilient mounting
mobile_bob:
I would like to submit the following for everyone's consideration, this post is not to suggest any
way over another of mounting an engine. It is basically the most coherent analysis of what has been discussed that I can come up with. I will try to break it down into components, sometimes simplistic and at other times a bit more complex, in the effort to try and pull the discussion together.
There are two opposing sides at play here, (1) the use of concrete as the only way to mount the engine, and, (2) an alternative method using steel and resilient mounts
In the following paper I will attempt to examine critically both positions, first stating the position
and then examining the position and determine support for that position.
A. "Mr. X supports the contention that lister only specified concrete as the material of choice for mounting the engine, "
To date I have seen no documentation as to why the concrete block was to be used, only that it must be used to support the warranty. By documentation I mean supporting engineering text that clearly shows the need for the concrete base, not advertising literature but the math and physic's to support its use. Lacking such documentation one cannot assume whether the use of concrete is mandatory or not from an engineering standpoint.
B. "Mr. X further contends that lister made no recommendation as to the use of anything other than concrete, and specifically that they never mentioned the use of resilient mounts."
Just as in (A) above I have not seen documentation that lister even tried resilient mounts.
Again without supporting documentation in engineering terms we cannot assume that the use of resilient mounts are inherently good or bad.
C. "Mr. X further states that the concrete block was an integral part of the design of the engine"
Here again to date I have seen no documentation that the concrete block was an integral part of the engine design. Further anything that is bolted rigidly to the crankcase becomes part of the crankcase for purposes of transmission of vibration, resonance, and vector analysis.
Examining the contention that the concrete block was an integral part of the engine design the engineers in their wisdom would have had to work out all the math/physic's of a number of parameters all based on the specific use of the concrete base.
The problem with this contention is the same engine crankcase was also used on the SOM wherein a cast iron base (which bolted to the engine block become part of the crankcase) is used as an intermediary component between engine and concrete block. The use of a cast iron sub frame would require differing physic's, vectors etc. to enable the concrete to still become part of the crankcase. This assumes the contention that the block of concrete was an integral part of the design.
It therefore cannot be an integral part of the design of the engine, because both engines whether mounted directly on concrete or mounted to the concrete via the cast iron base are the same engines, using the same castings.
So can we assume that the use of concrete as a mounting base is or is not the only way to mount it? No
Does it allow room to explore other possibilities of mounting? such as resilient mounts? Yes
Now the opposing side
(D) Mr. Y contends that much has changed technologically in the last 50 odd years
Mr. Y, needs to understand and accept that while technology has advanced the basic physics have not changed. Materials in some cases have changed, but cast iron is still cast iron today as
it was 70 years ago. Resilient mounts while made of better material today follow the same physic's they did back then. Very little is truly new, and practically nothing related to these engines is any different today than it was 50 years ago.
(E) Mr. Y contends that the engine can be mounted on a steel frame with resilient mounts
While anything can be mounted to anything else with sufficient effort, Mr. Y should be aware of the problems he will encounter in doing so. Should the engine be bolted to a substantial steel sub frame with quality components and then bolt the sub frame to the concrete base, technically he should have no problems or safety issues. Basically he will have a steel SOM base. Which arguably may be superior in strength to the original SOM cast iron base.
The problem however arises with the use of resilient mounts and the stresses that will be imparted back not only to the steel sub frame but to the engine block itself. Remember the steel sub frame is now part of the crankcase.
Resilient mount positioning will be critical, and should be in line with the plane of the crankshaft, not below the crankcase as is typically described by those wishing to use this method of mounting.
The question then arises on how to raise the centerline of the mounts to the same plain as the crankshaft centerline? This is where one can get into all sorts of trouble, this is where the highest stresses will be transferred. That being the transmission from the lower frame mounts to the risers. Presumably one would have to weld the frame risers unless he can have the side rails of the steel sub frame mandrel bent to raise the mount to the centerline of the crankshaft. These welds will have significant stresses imparted on them, and over the course of time will likely fatigue and fail if not properly designed and executed.
Also it is well worth noting that the engine will exhibit what is known as "critical speeds" which in stationary use the engine should not be running in. These critical speeds are evident when spinning up and down of the engine it passes through rpm ranges where the vibration and stresses are dramatically higher than at rated speed. Provisions have to be made to limit this mode of operation and to provide a measure of additional support for the engine while in the "critical" engine speed range. This adds another layer of complexity to the design.
in conclusion:
there is no clear evidence that the use of concrete is an integral part of the engine design, further there is no evidence that supports that it is the only way to mount it. Clearly the use of concrete has proven to be a time proven design, a safe design that works. It has proven to not have any detrimental effect on the engine and it could be argued that it has improved longevity of the engine, even though no studies have been done.
The use of a steel sub frame that is securely mounted to the concrete block should provide a safe and sufficient mounting for the engine, that is well within most DIY'ers capabilities. Also the use of relatively thin and dense pads should cause not adverse effects on either the engine or the safe operation of the engine, although not providing much in the way of abating the transmission of vibration.
The design, manufacture and use of a steel sub frame and resilient mounts should be possible provided that the design is well engineered and fabricated following accepted engineering standards. It is my conclusion that this may be well beyond the capabilities of the average DIY'er.
My hope in presenting this thread/post/paper is to cut through the feeling, thoughts and conjecture that has been prevalent in the discussion, and to narrow it to the basics at hand.
Again I am not going to suggest one method of mounting and engine over another. Should the end user of an engine not feel he understands fully the forces at play I would strongly suggest the use of either concrete direct mounting or a steel sub frame directly mounted to the concrete.
hopefully this will be accepted by all in the spirit it was written
I invite constructive criticism, thoughts and questions, and of course opposing views :)
bob g
Procrustes:
I don't get it Bob.
Without a doubt the technology has advanced since the age of the Lister. Kubota and others make excellent diesel engines which use convenient flexible mounts.
The designer of the engine we all revere plainly specified the use a concrete block. Does it make sense to revere the engine but regard as quaint the designer's installation instructions?
Hotater learned the hard way to use a block, and documented it clearly.
I guess in his passion Guy overstated the risk of out-of-spec mounts. Still, if you believe this old technology is still vital, why do you believe the mount is old fashioned?
Surely there's a place for alternative mounts, maybe in the majority of situations. How many of us are off grid? Of those, how many really need tens of thousands of hours out of these engines? If you want to do it right, though, it's hard to imagine a safer bet than following the manual.
mobile_bob:
Pro:
what don't you get?
maybe it is just late, and i am too tired, but you seem to be on both sides of the issue, or am i missing something?
i wrote a responce to your reply, but after doing so i scrapped it because you appear to be back and forth a bit..
please clarify, is there a problem with my original post?
specifically?
bob g
Procrustes:
--- Quote from: mobile_bob on October 04, 2006, 06:50:32 AM ---what don't you get?
maybe it is just late, and i am too tired, but you seem to be on both sides of the issue, or am i missing something?
--- End quote ---
You're right, my post was confusing.
What I meant was, I've read lots and lots of discussion about how to mount Listers, but IMO if you want to do it right, RTFM.
If you want to reap the fruits of modern technology, get a Kubota. They're wonderful, and easy to mount. If you want to pursue time-tested engineering, then do just that.
RA Lister's glory occurred at a time and place where one might expect to use a stationary engine for decades and to pass it along to kin and to run it for tens of thousands of hours. That's vanishingly rare in our place and time. If you won't run an engine for more than a few thousand hours, it likely won't make much difference how you mount it, so sure, take a shortcut -- but don't fool yourself that you're doing it right.
What I don't get is all the discussion about the right way to do it, the right way is plain as day.
I'd been holding off on making that post, but when this new thread opened I went ahead. I wish I hadn't now that I think it through though; I didn't say anything novel. Sorry for diverting your thread.
slowspeed1953:
Well here's what I think. It really doesnt fucking matter how you mount your engine as long as you are happy with the way you mounted your engine. Im sure Hotater has a true sense of pride in a job well done, it was a huge effort and hopefully satasified his fondest mounting desires.
Screw the manual's mounting reccomendation that shit is so damn antiquated at this point in time to me its not even funny. Ill mount my engine on what will stand my willie and statisfy my fondest mounting desires and that will be on a set of modern air filled industral mounts made for machines like hammer mills and other ultra heavy duty equipment. The added peace from a vibration free setup by far out weighs the minute chances of catastrophic simultanious multiple mount failures.
Peace&Love :D, Darren
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