Lister Engine Forum
Lister Engines => Listeroid Engines => Topic started by: George A on January 25, 2016, 01:39:53 PM
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I know I should probably do a search on this first, but I wanted to get some quick opinons/information...
I have a "vintage" 2500 watt Root and Kurtz brush generator belted to my Vidhata and so far I'm fairly happy with it. When test running it though I noticed "Lister flicker" due to the engine power pulses as described here several times. It seems to be mostly in ordinary incandescent bulbs more than CFL's or LED lights. Had I known about the phenomenon when I ordered my engine years ago, I would have specified the heavier flywheels......but no, I liked the "antique" look of the spoked wheels ::).
Would a more modern generator with voltage control, such as a 3 KW ST unit, reduce this? Even a little bit?
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Hi George, My 15KW ST head is powered by a Chinese horizontal, it flickers at a faster rate than yours, ;D
I am a far piece from a generator expert but I did try one of the AVRs that wires into the harmonic circuit. As far as I could tell it didn't do anything to reduce flicker so I removed it. I think you will find that weight, either on the crankshaft or generator shaft is the ultimate fix
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We use very heavy solid pulleys on the generator side to help offset/reduce the engine power pulses.
dieselgman
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Okay guys, I thought mass might be the solution as no AVR would be fast enough. My generator pulley is a 7 3/4" serpentine pulley from a GMC 350. I machined a simple adapter to fit the shaft, so I'll redesign it to incorporate a heavy flywheel behind the pulley then try it. It just so happens that I have a nice heavy stainless steel disc that's not employed right now.......
Thanks!
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@George A
Seems the heavy flywheel was a Lister solution. The Dursley startomatic generator pulley weighs in at about 80 pounds! Uses 2 v-belts
Cheers,
Hugh
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I also have spokes in my flywheels on my 6/1. I couldn't use my shop heat/light lamps with it as the flicker bothered my epilepsy pretty badly, so I did some work on trying to fix it. I could not find heavy flywheels so designed my own AVR specifically for flicker reduction. It works adequately for my 250watt each heat lamps, below 100 watt bulbs still have bothersome flicker.
I agree that heavier flywheels and more mass on your generator will help greatly; someone measured their SOM flywheel unit with a low pass filter circuit I made to look at flicker objectively, and just the SOM flywheels worked as well as my custom AVR running on my ST3.
An AVR on the harmonic winding will do very little for flicker; there isn't enough excess power on the harmonic during the compression stroke to compensate for the voltage drop.
For flicker compensation electronically, the ST-3 would be preferred, as it has less inductive lag in responding to field coil current increases. You must then use the mains output for excitation instead of the harmonic, so that excess power is available during the compression stroke.
I have a simple version of my AVR that I published publically that can be used, which has a PCB (layout available) or could be wired by hand. It costs about $80 to have 3 boards made (minimum order) due to the setup charges. Send me a message if you want it.
I can't recommend CGG's AVR for flicker reduction sans harmonic; I tried it on my new neighbor's setup and it was pathetic; the unbalanced load made the ST-3 moan and vibrate, and it could not start motor loads, and put a big load on the generator head. On questioning Tom, it seems he was aware of this pathetic performance yet having no other solution, offers it. His AVR does work fine on the harmonic, and is a good value for that application. I suspect it might actually work if configured on the 240V mains output (balanced), but he has zero documentation for it and I don't want to fry my neighbor's unit experimenting. In my own system, I have a 400 watt toroidal step down transformer to 120VAC which provides excitation from the mains. This is not as good as the harmonic in starting motors, but it will start my washer (1/2 hp) when the well pump (1/2 hp submersible) is running, so is adequate for my needs.
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Probably a dumb question here...but I am trying to learn for my future shop setup.
Wouldn't a line conditioner take care of the flicker problem, as well as smooth things
out for electronics? ???
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1) is there any caution about so much flywheel weight that the crank/con rod would suffer when the cylinder fires, and it's hammering on 500# instead of 200# ?
2) Line conditioners can't do anything about the frequency wobble of the power stroke.
They might be able to steady their output voltage. Your eye sees the brightness variation of the bulb, and that's from the voltage getting a kick as the engine accelerates from the power stroke.
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I tried one of the Sola saturated transformer-regulator units on 60 and 100 watt bulbs before I designed my anti-flicker AVR. It did not help at all. It seems they can't really cope with the combination of variable frequency as well as voltage.
I should mention that my "fast" AVR for flicker reduction does not do true RMS voltage regulation. It is not useful if you are driving a very bad PF load, such as a big non-PF corrected switching battery charger.
I tried one but the analog RMS IC's are all too slow to allow the 650 rpm-5 Hz compression/power cycle correction.
It would be technically quite reasonable to use a modern 16/32 bit microcontroller do the RMS calculation in real time with results every half wave, or even quarter wave. It is also technically reasonable for this controller to anticipate the next compression/ power stroke quite accurately, so that the lag in response caused by the ST rotor inductance can be anticipated and compensated for (predictive leading correction applied). But there are so few of us with slow speed engines these days that there is just no market for such a thing.
I really do wish we could get SOM clone flywheels from our Rajkot importers!
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Hi Bruce,
I have done the calcs for loading and stress etc, if you can find a second set of flywheels off a CBW machine, balance them and install outboard of the existing wheels, it would make quite a difference.... the only problem is getting enough shaft available for a crank-handle.... (Waiting for my 2nd set flywheels to arrive....on order....)
Cheers
Ed
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Hi Bruce,
I have done the calcs for loading and stress etc, if you can find a second set of flywheels off a CBW machine, balance them and install outboard of the existing wheels, it would make quite a difference.... the only problem is getting enough shaft available for a crank-handle.... (Waiting for my 2nd set flywheels to arrive....on order....)
Cheers
Ed
In my copy of the original Lister manual, they caution about placing pulleys as close to the flywheel as possible in order to reduce belt strain on the bearings. That's only the strain of a drive belt. Just how big an auxiliary flywheel do you think is possible without pushing the limits of Indian design/materials? I'm not being snide or anything, just really curious.
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Hi George,
If I take the calcs from my "out of balance" flywheel and work the forces out - 300g @ 300mm Radius @ 750rpm - I get an imbalance force of around 60kg shaking things around.... Now I can't remember exactly what the integral mass of the balance weight was that was cast into the rim of the non CBW engines, but it was, if I remember correctly, a hell of a lot more than 300g.... consider as well, that a belt can easily be tensioned way past 60kg (30kg per side) to give a very large radial load to the crank (Hence the "mount as close inboard as possible stipulation")....
Now, If I remember, the flywheels on my beasty are around 80 to 100kg or so each... so from a practical viewpoint, as long as reasonably well balanced, the forces are well within the limits, I would say....
As a rough estimate, I think the weights on the "cast in's"were around 4Kg as cast in.... @650rpm and 300mm Radius, the force is around 550kg... A balanced flywheel at double the distance from the bearing could weigh in around 275kg max to give around the same bending moment to the crankshaft.... Maybe I am wrong, use with caution, check my numbers....etc, etc, etc.....
What do you think?
Regds
Ed
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The no counter weighted flywheel outboard is a good idea, Ed. Alas, I only have room on one side, as I have a big outboard pulley on the non-IP side to run an air compressor, and I don't want to give up my ''manual reversion'' (hand crank) on the IP side.
Sure would be great if Rajkot would do some SOM type flywheels, preferably rated for up to 850 rpm so I could switch to propane/spark ...
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I have seen old pictures of installations where a CS was equipped with two flywheels on one side so that procedure had Lister's blessing in at least some applications. The SOM type flywheels are a LOT heavier than the spokes. Personally I would have no problems adding one flywheel to the non-cranking side.
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The DES 8/1 flywheels are a bit heavier than spoked. Just with that weight an the the higher rpm compared to my 6/1, but about the same hp on propane, it starts two- 0.5 hp motors at the same time without strain.
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Hey Bruce,
Lose the pulley, just run the inside of the v-belt on the outside of the flywheel.... I run up to a surge of 30A to 40A at 220v, ie 7 to 9kw on 2 belts and a double sheave pulley on my gen head... Belts haven't flipped over once yet, and I have only had to adjust tension once at around 1500 hrs or so....
You will of course have to change the pulley size on your compressor possibly, unless your big pulley is within 10% or so of your flywheel size, or your compressor can handle the extra revs....
Another big plus, for me anyway, is the easy removal of the belts... no de-tensioning, just creep them on or off the edge of the flywheel...no tools required.... Lazy works for me.....
Cheers
Ed
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I wholeheartedly agree with the use of vee belts running flat on the flywheel, Ed. On the 8/1 clone propane conversion I just did for Jeff G., we use a single B belt driving the ST-3. Works like a champ, no slipping or chirping on motor starts, no tracking issues, and quite cheap. I tried it as there were a much wider range of pulley sizes available and it would make changing engine rpm and pulley cheap. Now I'm "sold" on it and I think the serpentine belts aren't worth the bother unless you find a bargain. The belt tension for vee belts is substantially less, which can only be good for bearings.
My two stage compressor has it's cooling fan cast into it's cast iron drive pulley, so it would be difficult to change the driven end diameter. Could be done by adding a separate fan, of course, but in truth I've managed to get my flicker problems down via custom AVR to where I can live with it.
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Well, after thinking about it I'm not really sure an auxiliary flywheel on my generator shaft may be a good idea after all. That generator armature shaft was in horrible shape when I got it.....bearing seized and it kept running, scoring a big fat groove in the shaft. I welded it up, straightened it in my lathe and turned the excess weld off. It's accurate and strong enough, but the shaft is only 3/4" with a single row ball bearing (new) so it's not really beefy enough for a massive weight.
The only other solution that comes to mind is another flywheel on a jackshaft between the engine and generator. Although it would make the whole unit larger it would be an easy way to add rotating mass with no strain to the mechanical components. Playing around with different pulley ratios would be easier too. I know where there's a junked hay press with a cast iron wheel of around 400 lbs. or so....
Nah, next year. The lights don't flicker all THAT bad!
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I mounted 2 brake drums onto the crankshaft of my 6-1 Metro. The drums were off the front of a 1 ton van so pretty heavy, stopped the flicker and could be used as pulleys at some point in the future. Turned the hub to fit a taper lock bushing. I first tried a 70 pound flywheel on the generator shaft but that wasn't enough and the belt chirped on the power stroke. More mass on the crankshaft is the way to go. Leland
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I mounted 2 brake drums onto the crankshaft of my 6-1 Metro. The drums were off the front of a 1 ton van so pretty heavy, stopped the flicker and could be used as pulleys at some point in the future. Turned the hub to fit a taper lock bushing. I first tried a 70 pound flywheel on the generator shaft but that wasn't enough and the belt chirped on the power stroke. More mass on the crankshaft is the way to go. Leland
THAT is an excellent idea! First of all the raw material is readily available and cheap. Second, the two drums are distributing the increased load between the bearings AND evidently add sufficient rotational force to help smooth out any fluctuations. On top of that, they can serve as additional flat belt pulleys if need be.
Where did you find the taper lock bushings? Were they the correct size or did you have to machine the centers?
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I thought the SOM flywheels were more than double the weight of the spoked, with most of this at the rim. Those must be some seriously huge, heavy brake drums? How about a photo, Leland?
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Somewhere I saw someone had taken a flywheel and crankshaft out of a gas engine car (junkyard parts). They cut the end off the crankshaft where the flywheel mounts and bored a hole in the center to mount it on the CS crankshaft. I think they may have used a taper lock bushing for the mounting, but I don't remember exactly. Then put the automotive flywheel on this "adapter" that they built. It also provides a ring gear that you can use for electric start if desired - you just need to mount the starter in the right spot (and make sure it rotates the right direction).
Be aware that a flywheel with teeth is slightly more dangerous than a smooth flywheel!
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Great.........as if I don't have enough good ideas already ::). It just so happens I have a couple of model A Ford flywheels in my pile, complete with ring gears. Anyone familiar with them knows how heavy they are................
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I wish SOM flywheels were easy to come by because they would look better and add a lot more mass than what I did. But it's fun for me to re-purpose car parts for other uses. I like to hit the U-Pull junk yard when they have sale days because I always need something anyway. These brake drums were off the front of about a '70 Dodge van and not too common because most people popped the few extra bucks for disc brakes. The front drums are a better shape than disc brake rotors due to the mass at the outer edge. Also seemed better than a few engine flywheels I looked at for the same reason although a couple of flywheels might be enough mass if you chose well. I'd guess the drums weigh about 25 pounds each and just one seemed to cure the flicker as I also have a real heavy pulley/flywheel on the generator shaft. The area where the outer wheel bearing sat was a good size to turn a taper to fit an inexpensive taper lock bushing from Surplus Center. The 2" ID bushings are pretty cheap from several online bearing supply houses also but I don't remember what they cost. Brake drums or rotors for the rear axle would have a hole in the center that would be too big for a bushing. At some point I will adapt an automotive flywheel to bolt to the lug studs so I can use an auto starter on the ring gear instead of the belt drive thing I have now. I hurt my spine about the time I started playing with this CHP stuff even though I've been wanting to do it since I was about 10 years old. I haven't been able to finish the install; or a lot of other projects. I had fusion surgery and my spine has never been right since so I don't get much done in a day, or a year. I've been wanting to make a video to show how much my engine hopped before I added weights to the flywheels, haven't got to that yet in almost 10 years, maybe I can post a photo a little quicker. At the rate I get things done it could take a week or two until I can get to it.
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M61hops, I can sympathize. I blew a disc in my lower back in 2008 and developed a spinal stenosis later in 2014. Needless to say, my working days were over and after two surgeries I went to a disability status until I reached 65 when Social Security took over. It's been quite a ride! I can still crank my Listeroid, but I'm awful careful these days.
Thank you for that very accurate description of the brake drum conversion and the information about the taper lock bushings. Ironically, my stepson is a certified mechanic here in town so keeping an eye out for certain parts is easy. I'll have a talk with him today at lunch and we'll see what "inventory" is available........:)
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6/1 startomatic engines still have pretty bad flicker. My parents have one and the flicker seems just as bad as with the regular flywheels. I believe the only solution is to run the power through a battery bank and use an inverter. That's my plan with my Witte generator whenever I can get around to building it.
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Sometimes adding a large DC capacitor across the brushes/voltage regulator output + & - leads will dampen variations in excitation. The circuit could be resonating with the firing pulses? It's not going to cost very much to experiment.
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That's an interesting comment about the SOM's...........after all, I've never SEEN one in operation and simply assumed that Lister solved the problem with the heavier flywheels. Maybe not so much and we're beating ourselves silly over a problem with no resolution?
As for a capacitor across the output, I have two in my Root and Kurtz but they're for radio suppression and have no effect on the pulses whatsoever. Now these capacitors go from each output leg to ground and are, of course, for AC use. My generator has a separate DC excitation commutator........maybe that's where you meant?
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AC oil filled capacitors across the 120/240 output is a good idea to produce leading current to carry electric motor's lagging current without loading the alternator with reactive current. Won't make a lick of difference to flicker.
What I was thinking of was a Large DC capacitor across the DC excitation circuit . If the excitation voltage is hunting, the cap will smooth out those swings in Excitation current and thus smooth swings in output AC voltage .
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Subjective evaluation of flicker is highly variable, because things like incandescent bulb wattage and other factors play a role. Some people can see flicker much more so than others.
The SOM flywheels improve flicker only as much as my fast correcting AVR does... based on measurements with my low pass filter and an oscilliscope. With my AVR I can now tolerate my 250 watt light/heat lamps for my shop which previously gave me partial seizures. I can switch back and forth on my AVR to stock harmonic or AVR via 1 switch, and I made an RC low pass filter so I could measure the 5.5 Hz variation in AC peak voltage via oscilliscope. It is dramatically improved.
A responsive AVR could also now be applied to the SOM, something not very practical at the time of their design. This would add that much more to voltage regulation, and I suspect even I, with epilepsy, could tolerate 60 watt bulbs with both SOM flywheels and my AVR with mains excitation.
For most people, just changing to LED lighting which regulates LED current via a small switching supply will totally eliminate flicker. This is the simplest solution for people who can tolerate LED lighting. I can't.
As for B&D's suggestion of big electrolytic capacitors on the excitation side- sounds good but absolutely not helpful. If "smoothing" the excitation current was going to work, there would already be no problem as the rotor has huge inductance (a few henries) and is a highly effective filter in itself. The underlying problem is that the engine speeds up during the power stroke, and slows down during compression. This causes a big change in voltage out with a constant excitation current. Because the frequency is varying, this requires large and rapid changes in the excitation current to try and maintain voltage output. This is complicated by the lag in response by the rotor's inductance. The correction is always too late, so only so much can be done without a much more complex electronic solution. (A microcontroller would be required to anticipate the correction- a fairly complex bit of real time control.)
The simple solution is to switch your lights to something self regulating. If you must use incandescent bulbs, then a fast AVR and/or heavier flywheels/generator pulley ala the SOM is what you need. The smaller the bulb wattage, the harder it will be to get the flicker down to tolerable. The two tools available are adding rotation mass and electronic voltage regulation.
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Hi DirtbikePilot, I'm surpprised by your statement, does the generator have a heavy flywheel type pulley on the shaft? I thought that would cure my flicker but the belt chirped on the power stroke even though I tightened it as much as I dared. The speed variation problem is very interesting and I've thought about it a lot bringing up even more questions. Mostly I wonder if there is a point of diminishing return from adding too much rotating mass since the combustion event only lasts so long and the rod bearings only have X amount of resilience. At some point do you lose overall power output from the crankshaft? Then with using an alternator to charge a battery bank the engine can speed up but can the batteries absorb the extra pulse of power? Which way is more efficient overall? If I was off grid I'd have a battery bank and my 'Roid would run an alternator with DC output. I don't have the engineering smarts to calculate all the ways to deal with this issue but I do have a lathe with taper attachment. Yes George A, blown discs in the low back will change your life. I was planing to go on SS Retirement this year but just got a letter from SS saying that I'll have to wait a few more years! Major bummer for my finances! Somebody needs to invent something like silicone that can be injucted into the discs and then set up. I keep looking at this tube on my workbench and wondering how to get it to go through a needle! And now there is a crackdown on Dr.'s prescribing Oxycodone that was the best pain control I had. I spent the last year inside because too many kids steal grandmas pain pills to get high. Yay insurence companies in charge of health care! If anybody out there gets told you need holes drilled in their spine bones, I'd say don't do that!