Balance in the Listeroid design
There are few subjects that one could spend as much time on as balance in these engines. I remember the one Prakash 6/1 I had in the shop that ran so nicely on a 120 pound steel frame, and would run a generator without being tied down. Another owner of one of these engines claimed his was like a jack rabbit on steroids in his shop when he started it on the pallet bottom. It came out of the same container.
There are dynamics at play here, and we can see in our minds eye the immense amount of torque provided by even one power stroke (rack open). If the engine is not tied down, the engine case will want to rotate, as there is a contest under way, will the next power stroke cause the case and crate bottom to rotate, or the flywheel to increase in speed?
It can be a dangerous thing to start and run a stationary type engine that is not tied to a proper frame period!
Another factor to consider is the physics of a one cylinder engine, we realize that this is not a situation where the best of balance can occur. If we study an opposed twin, it is quite easy to counter the reciprocating piece with it's twin and 'counter balance'. With the single cylinder design, we have a single piston, and a weight or mass that we add to a point in the flywheel or crank to attempt to 'counter balance' the piston and rod. Due to the fact that these two masses can not be kept opposite each other as they go round and round, we see that we can only mitigate this imbalance to a certain degree.
There are single cylinder engines far more elegant, and the old Chinese singles (however crude they are considered) are examples of engines with counterbalance shafts. When we look at the mechanics of this balance shaft it is no more than another weight that is coupled to the crankshaft via gears as it attempts to further 'counter' the piston+rod mass and it's counter.
The fact that the Lister types do not have balance shafts should tell you that these are NOT smooth running engines, and that all of them will benefit from being tied to some timbers, steel rails, a concrete slab or something similar.
You can note the difference between balance problems, and poer stroke torque by slowly increasing flywheel speed, use just enough rack to increase speed. If you can get the engine to operating speed and hold it constant, there should be little if any fuel burned during the power stroke, as the engine becomes 'slack' you will see what is balance and what is caused by the power stroke.
If we 'scale up' a single, we can see that the mass of the piston and the counter will become greater if the materials are the same. This can and does create even more of a problem to mitigate as balance goes. BUT the bigger danger is not understanding the huge amount of torque created by the power stroke of an engine that might make as much as 20 hp at 1000 RPMs! This is huge, and can cause the engine to rock and buck as the power stroke comes in.
There are a good number of variants, and we must take into account that aluminum pistons are often used in the variants to get the weight down, and make it easier to counter this weight. There may be other factors that make the use of this metal more attractive, but it is outside the scope of balance.
With the understanding that there are two very different forces at work here, one being the power stroke, and one being the balance, we can proceed. We would all like a smooth running engines, and if this is really the most important factor for you, get an opposed design, and if power stroke concerns you, get as many cylinders as you can afford.
The next thing to understand, may take a little faith, or you can just order a 40 foot container of engines, and run each of them yourself to learn it first hand. Out of one batch of Prakash engines, we had one run very smooth, the next no where near as good. I was so impressed with one, I took a video of it, and put it on the CD to demonstrate what is possible.
Over the course of time, I have learned that is is only the extremely foolish that would make an assessment of a company, or their engines based at looking at only one. To compare one brand to another having seen only one engine of each brand is also foolish.
It has been the case with Metros, Prakash, Fu King, GM90s, Vidhata, Lovson, and others, some are better balanced, some are not. if you have seen one of them, you've seen next to nothing.
What we do know is there are a few folks that have Listers that are not considered real smooth runners; take Mac McQuaid's old 6/1 CS, he's had it for sometime now, and to be around it, you'd think it plenty smooth. It has many hours of running on it, and is well mannered only because Mac mounted it to rail road ties, and buried them flush to the ground. This makes the best bed for a really big single, or a less than well balanced 6/1.
So next time you hear someone talking about balance, you might already know more than they do. Anytime you run one of these engines where it is not tied to a good frame, you take an unnecessary risk.
As for the so called "Balanced" engines, I can tell you about two Ashwamegh 25/2s that Scott Emery (Marine Diesel Engineer) and I checked out. After I had decrated one, we thought about starting it on the pallet bottom, considering the 180 degree crank, and noting the drilled holes in the flywheels, we decided to give it a try. It ran, and it was smoother than we had anticipated, still, we were very careful to back off the Gov spring and start raising RPMs slowly! The sound of these twins is music in deed. When Scott took delivery of his own Ashwamegh engine, a serial number away, he was quite certain that his engine was NOT as smooth as what we had run in the shop. Of course we do not suggest smooth, we are talking in comparison. Although less than scientific, this reflects on the manufacturer and their methods, if they don't tell you what they will balance to, what will you be expecting? As of this day, the general determining factor as to whether an engine passes or fails is it's ability to run for a certain period of time, and to have carried a load of a specific amount. Until a company in India publishes a spec, what can we expect?
Before I close, I will tell you of the worst balance experience ever! It's not a new story by any means, but one I will not forget. I had inspected and run a good number of Vidhata singles, and found them to be better than average, cheap fuel lines, junk filters, junk gas tanks, but the rest looked pretty good. After reporting my findings, there were some additional engines ordered and a couple of Vidhata 12/2s went to Canada. Not long after their arrival, I got a call from the owner, they had fired an engine and all hell happened. The owner very calmly explained that the flywheels had been placed wrong. Since this is a 180 degree crank, that means the counter weight was following the piston on each side! One can only ask how Vidhata managed to test this engine without noticing, but we come to expect India to care less about these things, and I doubt that it has much to do with money paid; as I know the person ordering paid a premium, and even asked if there was more he could do to assure quality??
As you might guess, the owner was only slightly inconvenienced, and had the Gib keys out and wheels swapped; but as unfortunate as it is, this is NOT the end of the story. Several days later, I got a second call, the pleasant voice with an British accent greeted me warmly, and then explained that he had found two left hand flywheels on the 2nd Vidhata! My heart sank, not only did we have a second problem, there might be another engine out there with two right hand wheels on it! After rambling on at length with apologies, the caller interrupted and said. "This may be bloody well easy to fix; we'll just turn this one wheel 180 degrees, and cut a new key way aye?". A few days later, there was another call, all was running fine, and running on veggie oil to boot! You may have already guessed, this was John Ferguson, and his good Friend Ernie, they now have more experience with twin Listeroids than anyone I know, and what makes them more valuable to our community is their long term veggie experience. Give these two a hammer, and they'll fix just about anything. Ask their opinion, and it won't be based on one brand, one week, or one experiment! Yes, these are older guys, and it takes them a good long time to form an opinion, personally, I think those are the best kind.
All the best,