Lister Engine Forum
Lister Engines => Listeroid Engines => Topic started by: jens on September 27, 2007, 01:32:26 AM
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WHOA there Jens--- The engine and the generator have to be ONE piece.
Different strokes for different folks when it comes to mounting. I like concrete and some like donuts. That's fine, but the donuts should be supporting a frame that hold the engine and generator head totally rigid between themselves. Otherwise the belt is sure to fail VERY shortly.
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Jens---
For a 20/2 engine I would think the lightest 'substantial frame' your could build would be 4" x 1/4" wall, box steel with round schedule 40 pipe bracing every foot.
I think the perfect 'portable unit' is an eight inch channel iron frame with the engine and genhead mounted to I-beam rails running lengthwise. Sit the whole works on a half inch rubber mat and then pour the whole frame full of concrete.
My next one will be exactly that.
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Jens--
Why not pry up the whole arrangement and put it on blocks to take the donuts completely out of the equation? Put a block in the middle, right under the engine.....
I'd be willing to bet your frame is too light and suffering from 'checkerboard flex'. That happens when too many squares make up a structure without diagonal bracing. One of the easiest ways to get this bracings is by using round pipe as cross members.
I think you have an engine that wants to jump up and down and you mounted it on a springboard. :o
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Jens
That Marathon generator spun as smooth as is possible before leaving the shop. They are spun up and load tested extensively at the factory before going out the door. Marathon should even have a record of the vibration analasis. It is my inclination to start questioning your home made pulleys balance, runout and or groove pitch as you were having problems with belt alignment and belt jumping/climbing right from the start. These serpintine drives are from my experience and my customers experience to be very easy to align and ultra smooth running. The amount of vibration you are talking about is going to do major damage to both the alternator and engines bearings. I would seriously try a different pulley and see how things run. As you are no longer running a tensioner the belt tension is now unforgiving and any osolation or runout will result in a major pulsation between the engine and alternator. I would also mount that engine on something as heavy or heavier than the engine and alternator combined such as concrete without dampeners. From the looks of your frame it is probably heavy enough to be sitting dirrectly on concrete but not beefy enough to be suspended at each end by dampeners. I don't think I would mount mine on dampeners at each end and it's made out of 6"x 6" 1/4" wall tubing. I will send you out a 7.325 pulley for 650 rpm at no charge just so you can try it and compare. No worries if it doesn't make a difference or you don't want it later I will pick it up next time I am on the Island. Let me know.
Troy
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Jens,
Do you have a link to a picture of your frame configuration somwhere? They are worth a thousans words!
Dave
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Jens---
How are you going to balance the flywheels without taking the piston and rod out to weigh them?? They have counterweights cast in and will be WAY 'out of balance' without the engine hooked to them.
Consider this---the engine might be about as good as it's going to get....take it off the trampoline and see how good it really is. You might have built in a problem without knowing it.
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I keep forgetting some people have extra cylinders!!
From looking at the picture....trampoline. I'd sit three 4x4s under it and crank it up to see where you are. The engine is in a perfect place to set up a spring action in the middle, in my opinion.
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Jens,
That is right...us 6/1ers and 12/2ers are external type guys. I would go get some modeling clay and do the mr x method and see if you can calm it down. The dampers should be fairly stiff. I can move my 6/1 maybe an 1/8" using my body weight. That heavy of a setup would need some real stiff ones!
Dave
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I've had good results with conveyor belting. It has tire cord embedded in it so it is very strong, but still cushions it a bit. I use contact cement to glue it to the bottom of my frame rails and with the weight of the engine it has held up very well. You don't need much, I use 3/8" belting, just enough to eliminate the hard frame from the hard floor. (otherwise it can "bounce" on the hard floor when it fires) It works pretty good for me. I'd use 3 pads on each side to allow the engine/generator to "adapt" to the profile of the floor. It usually works even better after it has taken a "set" after a few days. When I first installed my engine it had a tendency to pound against the anchors in the concrete and it was hard to keep the anchor bolts tight. With the conveyor belting under the frame I haven't had to tighten my hold down bolts in the past 4 years. The engine doesn't shake either!
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Jebs,
That package looks nice. The matrathon alternator looks very `expensive`. I really like the exhaust manifold you made which I see acts also as a bit of an expansion chamber. Nice work! As for the white paint? My suggestion is to take all the glamor photos of the finished plant now before you start using it! ;D The white does look nice though.
From the picture it is obvious to me that you have created a flex situation the way the generator is mounted which will offer little resistance to the pulley and opposite end of the alternator to nod up and down like a see-saw given the right mechanical excitation.
I would suggest that you make some end caps for the big box rails of the base and fill them with wet cement (regular sidewalk mix of gravel and sand which will cure into a heavy solid reinforcement). That will take a LOT of flex out of these main beams. If you have some rebar handy you could put that in there too. You will have to demount the hardware so as to have the rails vertical to do this. Use the rebar as a tamper to get the air pockets out as you fill, then just leave it in there. Cap the second end once the cement cures.
Those four small box tubings of the mount scheme for the Marathon head could benefit from being stuffed with a portland cement/ sand mix (no room for stones here) and a chunk of heavy rebar permanantly inserted within their length.
If you insert some large diameter round steel pipe (also filled with cement) as cross beams between the rails and up touching immediately below each of the engine mount box tubes, stitch welding them to those engine mount box rails and welding also at the ends to the main frame rails, that will help. In cunjunction with that you should also fill the two engine mount cross box tubes with cement. The result of this combo reinforcement will go a long way towards restricting the rotational vibration around the crankshaft which you are now seeing (top of engine swinging towards and away from the alternator.
Once you have done the mods I suggest your nice looking frame will look almost identical to how it looks now and will weigh twice or more as much. Placing the whole thing on a 3/4 inch thick rubber agricultural mat on a concrete floor may be all you need.
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Jens:
i have been hesitant to reply to this thread, but seeing how there has been some debate on the issue i would like to suggest the following
the rubber mounts on the engine end are "not" in the right position, they need to be moved outward substantially
and widened as well substantially.
optimally you want those mounts to be centered so that the center of the mounts are in line with a vector line formed by line from the center of each piston
through the center of of each crankcase mounting bolt and down to a terminus that is within the center of each rubber mount.
to illustrate, the left hand piston at top dead center, start a line at the center of that piston down through the centerline of the left crankcase mount bolt and continue down to the center of the rubber insulator.
where you have them now the torque action of the engine is transmitted mainly to the frame instead of into the mounts on the engine end.
i would expect that your movement at the generator shaft is quite high.
if you were to move those mounts under the engine as described, and add another crossmember with another set of mounts that coincide with
the other two vector lines from each piston down thru the inside crankcase bolts (those closest to the genhead), you would transmit the vibration more directly into the mounts and not have them diverted into the frame, also
the torque action of the engine would be far better contained and not transmitted to the generator, resulting in less movement.
i don't know if this is clear or not.
bob g
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at the risk of starting another 6 month debate :)
properly engineered mounting systems do not need to be massive in weight, (generally)
typically massive mounting systems are used to mask other issues, or used because they are more expedient,
cheaper, easier to fabricate and install onsite, by folks that either cannot or are unwilling to engineer a mounting system.
(now that is probably going to piss off somebody, but that is not my intent)
rather it appears that there will always be folks that will try to mount these engines on other than a ton of concrete, so
there will always be a need for an understanding of how to do it correctly.
ignoring this fact will not make it go away, so maybe we need to at least try to incorporate some engineering into these
light mounting systems.
we all now know pretty well how to mount them with a ton or two of concrete, that is well proven and understood to
just plain work.
what is unclear and rears its head over and over again is how to engineer a steel frame with some form of isolation,
this i for one feel needs much more analysis and debate.
but what do i know,, i am just an arguementative son of a %$#@&
bob g
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typically massive mounting systems are used to mask other issues, or used because they are more expedient,
cheaper, easier to fabricate and install onsite, by folks that either cannot or are unwilling to engineer a mounting system.
(now that is probably going to piss off somebody, but that is not my intent)
Hey, I resemble the later part of that remark.:) And I am Not pissed off at all. Expediency is exactly why I went with a high mass mount structure, AFTER establishing a good state of balance and rigidity in the base frame. It is well proven technology and quite affordable. Thirtyfour 60# bags of concrete can be had for as low as $68 on sale. Add a wood form, wheelbarrow, hoe, clean water(3QT per bag) and some sweat, and a 2000# base is well within most peoples abilities. If you want to be lazy, rent a portable mixer for the afternoon. In my case I already had a 1300# block that I sandwitched between my frame and a lower base plate that seems to be working well with my 6/1. I said it before, re-inventing the wheel can be fun, but R&D is time consuming and costly and I prefered to use what spare time I had available for this project on developing affordable heat recovery.
Jens if you search this forum for "resilient mount" or something such, you will find several pages of ummm "Discussion" on the subject that took place a few months ago. It includes I believe some math, theory and diagrams from both viewpoints.
Ron
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Ok, so much for that idea .... damn ... back to square 2 of trying to figure out how to reduce the overall frame vibration.
Any input on generator vibration from torque pulses - is there a need to worry about them? Should one install additional steel between the engine and generator besides the main frame to which they are both bolted ?
Jens
If, your gen head is bouncing around, without a belt spinning it, I'd stick it on a good solid 1/2" plate of steel, with adjustment slots on the plate. You don't want your expen$ive head frame to be torn apart because of resonances with the listeriod mounting frame.
If you get your 20/2 balanced nicely, even having a plate under your gen head, can't hurt anything I could foresee.
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I don`t know why so many people come on here and ask for technical suggestions, then when they get them they completely ignore them and end up doing it their own way anyhow and are usually disappointed with unsatisfactory results.
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jens--- If you have movement at the dog house then *somewhere* is the 'pivot point' of that vibration. the pivot is probably at a solid place and somewhere not as solid is moving. Figure out that point of rotation and install a brace to cancel it out.
Remember that troops crossing a bridge don't march....WEIRD things happen with the strongest of structure under rythmic loads.
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Well maybe I misunderstand what you have.
If the generator moves AT ALL, it is moved by action of the engine. It shouldn't. Something is to flimsey to hold it. Find out what that is and weld a brace to it.
I think the genhead is mounted to springboard and any movement in the engine is transferred and magnified until you can see it.
IF you're saying EVERYTHING that's connected together is moving the SAME amount.....then add weight.
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Hi I think you need to get rid of the rubber mounts. Probably the frame is not stiff enough.
I built my frame of 6"x6" timber. I don't see the kind of movement you describe. My frame is sitting on bricks in sand. The viberation of the engine running compacts the moist sand to a high density. The movement I see at the engine is fairly small and mainly due the a flex in the timber. I get belt slap from torque pulses when under load. If the belt is loose enough I can hear a short duration squeal when the belt slips as the engine fires.
The idea of mounting to a large mass of concrete has a lot of merit. Consider bolting your steel frame to a block of concrete.
Dennis
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Jens
Your choice of welding the cross tubes on top of the long end rails is still one area where you are going to experience flex. Triangles make rigidity, open squares do not. It is a simple fact that cannot be avoided.
Do you have a packing box like movers use? They arrive stacked flat and are assembled by first opening the 4 sided tube into a square, then folding the top and bottom flaps in and tapeing them in place. If you do, unfold the top and bottom so you again have the box tube, then push on opposite corners and see what happens. Lay it on it's side and set some weight on it and see what happens(especially when you push the weight in the axis perpendicular to the tube). Now fold and tape the top and bottom flaps shut and repeat these two simple tests. With the ends folded, you have material between the opposing corners and basically have formed 2 triangles that stiffen the structure. Your tube configuration is like the unfolded packing box, and allows movement of your engine and generator in the fore-aft axis... There is no material between opposing corners. This is one of the more valuable lessons tought by an erector set, that the lego generation typically misses out on.
I think you will find quite a bit more rigidity if you take a sawsall and cut the ends off of those 4 cross tubes, drop them down in between the side rails, and weld them all the way around. Due to the wall thickness, it is still not what I would call ideal, but it should be significantly stiffer in the fore-aft axis when assembled that way(mine sure is:). You could also cut and fit triangular gussetts to all the tubes on both sides and ends. You could also cap the ends with a long piece of heavy flat strap that is also welded to the side rails, but I think placing the cross tubes down between the side rails would be easier and take less additional material.
Look at it this way, You are not satisfied with it now, so you really have nothing to loose(except time and weld rod/wire) by cutting it up and experimenting with the steel you already have.
Good Luck
Ron
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Once more I'll suggest that you try Mr X's simple wheel chauking method. Balancing the wheels alone I woud expect to have accomplished nothing. The manufacturers don't control in the slightest the weights of the conrods and pistons. The Mr X method will greatly help to compensate for this problem.
If the Mr. X method doesn't do the job adequately, then I'd check to see if your two pistons and conrods, wrist pins, are grossly mismatched. I can't comment on the steel frame- mine is wood, mounted on rubber pads. But I can now set a glass of water on my valve cover with the engine under 70% load, no problem. The twin should be better if well balanced, I think. (I just have a 6/1)
Bruce M
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Sitting on wood should be OK, at least to get it way better than it is now. It's not like you're lacking in movement!
Chalk the wheel at about axle height- some of us will admit to using a 5 gallon plastic pail as the brace for holding the felt tiped pen to the wheel. :)
I found that "Sculpey" plastic modeling clay was a good temporary weight for testing, and that a few blobs of 4 oz were a good test weights. The clay goes on the inside of the rim, of course. I ended up with about 3.5 lbs of lead weights. When I got to the fine balancing, I quit marking and just tested. Your feet and a plastic container of water on the valve cover will suffice for the fine tuning. Just stop marking once you feel it's not making any difference, and just try moving your trial weight "around the clock".
Bruce M
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jens---
Balance the wheel that shows the most motion....that's the one that needs it next.
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Jens
The engine is not causing the vibration, only a small portion of it's mass is. Most of the engines mass is dampening the vibration forces. The resultant movement of that large mass can be very powerfull. I think if you had a real vibration problem, you would probably be afraid to run it as it would be trying to walk across the floor. The movements you describe sound harmonic in nature. In your current configuration, imagine the top of the 2 horizontal box tubes under your engine as one plane or plate. The top of the 2 tubes under the generator are another plane or plate. The top of the longer side rails is a single plane at a lower level. With un-triangulated tubes, these upper and lower planes are basically joined by vertically mounted leaf springs(side walls of the box tube) and no shock absorbers. By removing this spring and flex, as you noted, you will directly couple that much more mass to the engine to further dampen the resultant movement from an out of balance condition. In addition to the end gussets, you might also add some vertical plates(shear webs) perpendicular to the tubes out in the middle. This will help to stiffen/couple the upper and lower planes.
I guess what I am trying to say is that untill you stiffen the frame, you will have a hard time determining what movement is from engine vibration, what is caused by engine torque(movement allowed by flex) and what is driven from stored energy in the flexing frame.
Search back thru the balance threads, I know I, along with others have described how to performed the Mr-X method. One thing I found in my experiments was that the results were less confusing when you isolated forces. I took my initial measurements with the engine coasting and the decompression engaged. This was difficult, even with 2 people. I had my best results spinning up the engine with head and crankcase cover removed, using an electric motor. No power or compression torque effects, only pure spinning out of balance mass energy being applied. As Bruce mentions, a 5 gallon pail makes a handy marker stabelizer:). I also used a 1" dial indicator measuring th movement of the whole frame. I clamped it to a heavy bar of steel setting on the ground for fine tuneing. The needle arc in thousandths of an inch showing fore-aft movement is a little more subjective than how a water glass looks or how it feels to my hand. I also did this final testing with the frame setting up on 3/4" pipe rollers, as I reached a point where the out of balance forces had difficulty overcomming the mass and the friction with the concrete garage floor. When I was done, with my frame setting on 3/4" pipe rollers so it moved easilly in the fore-aft axis, I had around .005" of movement with the electric spinup. While still on rollers, I re-assembled and ran the engine. With the engine running, I had I think .015" fore-aft movement. This increase in movement was from torque and the only way to remove that was to not generate electricity. So the whole assembly needs to have enough rigidity and mass/friction to not move while generating it. With the frame back on the garage floor and powering a 3KW electrical load, the movement is bareley perceptible.
Ron
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Jens-
The top of the dog house is moving toward/away from the engine, right? Or side to side?
Remember you can't balance out the torque pulses, the mass of the flywheels is very high. When the engine starts compressing it twists the case one way, and when it fires it twists the other. Might try cutting some wood 2x4s to fit in between your upper square boxes, and hammer shims in to tighten them as much as possible. See which one falls out first, should show you weakest point.
To clarify 2x4 on end, parallel to the base rails, shims on the ends of the 2x4s. Might tie all the upper boxes together. I bet no matter how tight you get the ones between the engine and generator, they fall out before the engine gets up to speed.
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Here is what I see.
(http://listerengine.com/coppermine/albums/userpics/10083/Lister%20frame.jpg)
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There are probably an infinite number of ways of doing this successfully. However, there are a couple of fundamentals that you must do.
1) The structure between the engine and generator must be sufficiently rigid.
2) The weight of the structure that is between the rubber isolation mounts and the engine/generator should be as heavy as practical for your situation/objectives. The reason is inherent to F=MA. Larger Mass results in less Acceleration (and associated stand Displacement resulting from engine vibratory Force) that the rubber isolation mounts will ultimately see and then have to attenuate.
3) You have to know the vibration frequency that you want attenuate and the total weight of the stand (i.e., engine + generator + structure weights). Only then can you determine the number and characteristics of the rubber isolation mounts that you will need to use to achieve the desired vibration attenuation. Calculation information can be found: http://www.karman.com/selectvibro.cfm
Here's some photos of what my stand looks like. There are 8 total rubber isolation mounts. I can place glass of wine on floor a foot away from running engine and there isn't even the slightest ripple. My stand now sits in corner of my garage with about 1/8" clearance on three sides. Wheels can be installed/uninstalled as required to allow moving the stand to more optimal location for maintenance/overhaul.
(http://www.photolava.com/view/7wc0.html)
(http://www.photolava.com/view/7wc4.html)
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i would add one more critical component to the equation
that being placement of the isolators,
in my opinion they are in the wrong place as constructed
the ones under the engine need to be further out by maybe as much as a foot
and wider by nearly the same,,
this from what i can see in the pictures
where they are located they have very poor mechanical advantage or control of the vibrational and torque action applied to them
i spent a hell of alot of time argueing with GuyF about the possibility of using resilient mounts,,, and it took me a long time
to understand his concerns.
that being
if you want to build a resilient mount system, you must engineer it, if you don't your results will range from possibly good if you are extremely lucky
to absolutely dangerous and everywhere in between.
you setup is clearly somewhere between the two extremes.
time now to go back and engineer the system,, and see if what you have can be modified or if you will need to scrap it and start over again.
if i might suggest go back and look at how the oem lister was mounted to the block of concrete,, particularly the early version where ~625 lbs of concrete
was used. print out the drawings and use a straight edge to see how the vector lines work out
after doing so you will see where those rubber mounts should be placed.
this all assumes that the steel subframe assembly is very rigid! any flex and all bets are off, all your engineering will be off
because the flexing frame becomes part of the resilient nature of the mounting,, and there is no easy way to calculate
the action of a flexing frame and its contribution to your problem.
as much as i hate to admit it GuyF in many ways was and is correct, what looks good or appears to be intuitive often times just don't work!
your frame assembly while looking good is an example of what he was illustrating in 10k words or more :)
bob g
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Everyone always tries to re-invent the wheel, and it's always the same reasons, they want to do the job a wheel does, but they don't fancy using an actual wheel...........
Last year or the year before I posted pictures of the top AND underside of the cast iron start-o-matic base, full of transverse and longitudinal runners creating a load of cells, maybe a few inches a side in dimension.
Just because you don't have access to a foundry & patterns doesn't mean you can't do the same STRUCTURAL and MECHANICAL job with a stick welder, power hacksaw and a bunch of steel section.
Looking at http://www.pacificsun.ca/~jens/pic/public/_MG_7642.jpg
It is ORDERS OF MAGNITUDE too weedy, best advice is throw it all away and start from scratch.
Nota Bene.
If welding steel to approximate a cast construction in terms of properties, jens frame is (sorry) a classic example of how not to do it, it is nothing but straight lines and right angles, you need gusset plates in ALL the corners in all three axes for each corner, same as a casting, and it doesn't hurt to use a bit a crane jib type triangulation too, to compensate for the different material properties of steel and cast iron. Other thing is spot and straight welds are a waste of time, only a matter of time until the fail, the important part of the run is where it wraps around each corner at the beginning and end of each run, leave out this and you lose at least 50% of the potential strength and stiffness.
6" RSJ is, I suggest, the absolute minimum steel section to use for construction on the frame, with plenty of gussets and fillet plates, and a high current root weld that penetrates visibly to the other side of the plate, and remember to work your way around as you weld so the welding doesn't pull it all out of square.....
the frame is as important as a car chassis or a motorcycle frame, cut ANY corners and you dramatically affect performance, a car with a good chassis and crap everything else, like a bike with a good frame and crap everything else, will nearly outperform a car with a crap chassis and top of the line everything else.
Plan three times, measure twice, and cut once, else you'll end up with a sturdy frame with crossmembers in all the wrong places and have to start adding and cutting to actually fit the engine and head etc, how about leaving room to pull out and fit a drip tray without disturbing the engine and head? how about anchoring fuel, electric and other connections to the frame so they can't get pulled or damaged, how about mounting an inline racor type fuel filter / water separator on the frame, or belt guards, or jacking points, plan all these before you cut your first piece of steel, much less start welding.
the frame as pictured in the link above is basically scrap, sooner that is accepted and a new one made the easier things will go.
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Jens, My memory is badly impaired, but I do think I ended up with about 3 lbs (over a pound and a half on each wheel) opposite the external counterweights on my Metro 6/1. I can't remember the exact weights. There is no internal balancing on these models, the amount of weight required is substantial.
As Hotater suggests, start with the worst wheel. I tested with clay, and then added about 2/3 of the indicated weight, then went to the second wheel, and repeat.
I did use a dial guage, but it's not necessary for the initial balance during chalking and is not that useful if dynamic balancing with the engine running. I have no doubt that Ron's method of reving up the motor via electric motor works very well, with great precision, and a dial guage would be handy for that method. By all means, use that method if you prefer. I'm just saying that a "good enough for me" job can be done with the engine running at actual operating rpm. Ron's method would be more scientific and lends it self to measurement as opposed to using your feet and a cup of water on the valve cover as indicators.
You don't need to get so sophisticated on the marking pen stabilizer- but any sort of effective brace that lets you move the pen slowly to the wheel will suffice.
It is far easier and faster to do a pretty good balance one of these engnes with the Mr. X method than it is to explain it or defend it in a public forum. Far, far easier. Then you can address your frame and mount design issues as needed.
Bruce M
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jens--- If you have trouble with Mr.X method, go to any machine shop and ask the machinist to show you how he roughly 'indicates' a piece in a four jaw chuck......rest a pencil and run it in until it touches. Where the mark is is HIGH....adjust and re-try. Its' exactly the same thing.
BTW-- It'd be best to NOT put a belt on that engine until you get the movement sorted out. Under load vibration can become the Energizer Bunny on speed. I notice that you still have the same problem that you did on page one.....and still haven't addressed the solutions suggested then!
Are you just being stubborn??! ;D
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The Sculpy plastic modeling clay I used was useable at 650 rpm on a 24" rim, so your mileage may vary.
Rather than build something elaborate, I'd suggest just go buy some clay or plan on wasting some stickon lead mag wheel weghts. A search for "plastic modeling clay" shows lots of 1 lb boxes for under $2. If you use some carpet tape and the wheel weights upside down, then you can save the "good side" for your permanent attachment.
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jens---
I refer specifically to the bracing comments. ROUND pipe bracing, not square. The whole assembly is not rigid enough to absorb the energy it's being fed.
You don't make a house of cards stronger by adding more cards....you use TAPE......bracing.
For weights you can use 3M mounting tape temporarily. Solvents will eventually result in failure of the tape but it's good for hours on a milling machine or surface grinder.
For permanant application, form a lead strip of the proper weight and epoxy it to the inner rim so centrpedal force holds it there. Spread the weight OUTward....DON'T put a heavy lump in one spot.
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sailawayrb - your picture did not post, could you try again please ?
I tried to post photos, but haven't had any luck. When I click the Insert Image icon, it just puts following into post:
(http://)
In other bulletin board websites I use, you get an opportunity to browse to the location of photo on your PC and then upload it onto the bulletin board. Anyhow, if someone can walk me through the process, I would be happy to modifiy my previous post to include the photos of my stand.
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Bob--- THis forum has to have the address of the photo hosting site between the url brackets. Look up 'free photo hosting' for a LONG list of sites you upload your photos to and then use their url to point this forum's sofware to look for it.
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Bob--- THis forum has to have the address of the photo hosting site between the url brackets. Look up 'free photo hosting' for a LONG list of sites you upload your photos to and then use their url to point this forum's sofware to look for it.
Wow, that's pretty draconian, but I will give this a try. Thanks!
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you could try welding a rectangular plate to both sides, if you don't have a large U channel, but it may start flexing sideways, where a U channel would prevent that.
Plate should be tall enough to cover all of the square tube ends, down to the ground, full length and well welded.
I suspect the next weak area will start to flex then. Whats the phrase ? Polishing a t _ _ d ?
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jens---
The best you can do is set up a 'protocol' and analyze what works and what doesn't.
Start with a pound at the same position on both flywheels and keep a hand on the throttle bar to see how it acts....then change the position with the same weights and see how that reacts. Once you know *where* it goes start adjusting how *much* it needs.
Then by laying a sensitive finger on the engine's two sides, determine which one needs to be different.
One thing to remember-- It'll NEVER be perfect...ESPECIALLY if the mount is flimsy.... ;)
<the Devil made me say it.>
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The way I look at the situation, especially with the generator disconnected, if the engine stops shaking the generator will stop shaking.
Jens
Jens
You are still missing the point. THE ENGINE WILL NEVER STOP SHAKING! Even if it is absolutely perfectly balanced... For every action there is an equal and opposite re-action(Don't blame me, blame Newton). Every time the engine rolls around on compression, the wheels and crankshaft decelerate Since the piston is providing a braking force, the case tries to rotate in the same direction as the crankshaft(like a motorcycle doing a stoppie). As soon as the cylinder fires on the power stroke, the crank and wheels are trying to accelerate. This force being provided by the case means the case tries to rotate in the opposite direction. Watch this video closely. As soon as the engine fires, the rack being wide open and trying to accelerate the flywheels to the set RPM(high torque), the case wheelies on each power stroke. http://video.google.com/videoplay?docid=-2472879285322243628 Unless you never plan on running this really expensive boat anchor, that is the force your frame must withstand.
Ron
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Jens,
You should start by putting the weight opposite the line you marked on the flywheel, adding increments of 4oz. Restart, remark, add some more as indicated. Slightly leading the indicated placement (say 4" ahead in the direction of rotation on a 24" wheel) may help.
Start with either wheel, switch to the other after you've made some improvement on the first.
Starting a twin has got to be quite a challenge compared to the singles. If you don't have a starter of some sort maybe Ron's motorized approach is a better bet for you.
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Ya'll make an easy subject hard.
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Jens---
Back in history on this thread I suggested a 'box' of eight inch channel poured full of concrete. I think it would be nearly as effective to floor it and stack in sand bags.
Use PIPE for cross bracing!! Gusset all the corners in all directions.
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I just talked to a millwright and he said that conveyor belting is the thing to use. Rubber by itself will absorb shock but bounce back,
Mounts for the base could also be fashioned out of coveyor belting as well. It might be labour intensive,but well worth it.
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Jens.
Sand under vibration is like a liquid/gel it is not the same as concrete but at the same time maybe it is enough to remove the energy.
I have big heavy concrete block and for the second time i have broken fixing bolts.
and i am still trying to solve the problem maybe a sand filled sub frame will be a solution for me.
Greetings from Greece
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How about a base made entirely from conveyer belting.If one could obtain it cheap enough, a plant closure or a revamp of equipment at a plant.
Obtain about 50 feet of conveyer belting 36 inches wide or so and for example 3/8 inch thick. Next, cut it into 4 foot long lengths.
I know this would be time consuming! Obtain a good degreaser to clean the belting and get down to clean rubber. Buy 1 gallon of contact cement. Glue the 4 foot strips together so that you have 11 pieces making up a thickness of a little over 4 inches. This would then be sandwiched in between channel iron.
For mounting the engine and generator, 4 pieces of 4"channel,4 feet long with the hollow pointing down,top and bottom. 6"x 3/4" bolts every 12" or so. Distance apart would be determined by Listeroid mounting hole dimensions.
4 pieces of 6" channel ,5 feet long would be used on the outside for mounting onto the floor. Hollow pointing up at the top and hollow pointing down at the bottom.
Getting back to the 4" channel,it might be better to have the top pieces pointing up,and then weld pieces in for mounting the engine and whatever your driving.
This would be one huge vibration dampener. I can imagine 1 foot of 36 inch, 3/8 thick belting would probably 5lbs or more!
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The idea for a base made of coveyor belting and channel iron is that the rubber is one MASSIVE piece that absorbs shock. This is just an idea I came up with in a flash!!