I think I need to balance my Vidhata.........but..........

[George A]

I've moved my Vidhata back to its original spot in my garage, on a good concrete floor. Having watched it run and read a bit more about balancing, I think it would benefit from at least checking the balance and maybe see if I can get it to run smoother. It's not bad now, mind you, but I think it can do better (38ac's videos make me jealous!).

I'd like to try carefully weighed bits of modeling clay but need a process to follow. I've used the search phrase "Mr. X" and "balance" as suggested, but all I can find are references to the process and not the process itself. Can someone give me a link to the correct post or point me in the right direction? Thank you in advance!

[Hugh Conway]

Mr. X
http://listerengine.com/smf/index.php?topic=35.90
Reply #95

I would suggest this link too: from 38AC. Detailed and clear instruction
http://listerengine.com/smf/index.php?topic=6158.0

Cheers,
Hugh

[George A]

Thanks Hugh.....

[M61hops]

Hi George!  I don't want to be a kill-joy but the problem might be the wood floor.  You might try and run some 4x4 posts down to a footing in the earth under where you want the engine to sit.  I spent several hours trial and error balancing my 6-1 Metro.  It was a real bad hopper and I tethered it with bungee cords and used a 1" travel dial indicator to get it as smooth as I could.  It now "thumps" the earth for about 3' around where it sits.  I can feel every power stroke in my feet.  I plan to someday make a larger frame and fill it with a few hundred pounds of concrete to give some mass to the genset and then set the whole thing on a rubber mat.  I've got the dynamic balance as good as I could get but I need to somehow soak up the shock of the combustion event.  I had a similar problem with a 6hp Chang-fa engine, the whole genset jumped to and fro from the power stroke until I added a 100lb steel plate to the frame.  I don't know if I'm just unlucky or if all small single cylinder diesels want to move from the combustion event  !  My 2 cents for today...                                   Leland

[George A]

Hi Leland!

Actually, I moved the engine back to its original home on the garage floor for now. In order to brace the shop floor I'd have to cut down through it and then probably box it in for a concrete pour (no real crawl space, close to the ground)....but that's in the future, if it happens at all. It seems to be happy in the garage corner and is handy to an electrical feed to our main panel to boot.

At this point I just want to see if I can improve the balance at all and, at worst, I might have to tether it just to keep it from walking (rolling). My frame is pretty light compared to some on here...just two 3" I beams with 2" x 4" box tubing cross pieces and heavy duty casters underneath it all. It actually works quite well on the concrete surface, with only modest vibration which I hope to reduce in order to reduce the strain on the engine components if nothing else.

I'm still in the experimental/learning stage at this point and having more fun than is legal!

[BruceM]

I would suggest that Leland probably has flywheels which are badly mismatched.  That would make the Mr X method difficult, if not impossible.  If you have a steel frame on concrete, you also can't use the Mr X method without putting some sort of thick rubber or carpet matting under it as it is depending on movement of the engine.  

I like the Mr X method and have used it successfully, but I recently converted to  38AC's method listed above. The Mr X method can take a lot of time and requires skill and patience, depending on how screwed up your flywheels are.  It will often get you a rough balance pretty quickly, but it seems your engine may already be there.

Read carefully 38ac's method and ask any questions you need answered.  38ac's method saves a lot of time and frustration, even though it does require flywheel removal and making a simple jig for static measurement and then matching of the flywheel weights.  After this, however, you need only add weight in 4 oz increments evenly to both flywheels, either at or opposite the flywheel counterweights.    

Regarding your wood floor, I would first get the balance as good as you can where it is now, and then if you prefer to relocate it to the wood floor,  re-tune the balance (at or opposite counterweights, evenly on both in 4 oz increments) to avoid resonance with the wood floor system.  We do have a couple members with CS's in wood boats, so this is not unreasonable to achieve.

Here's a photo of my version of 38ac's static balance jig:










 

[George A]

Good advice Bruce.......I'll study 38ac's method again. I was hoping to avoid removing the flywheels (don't we all?) but in the interest of proper engine rebuilding it is justified. What the heck, I have the facilites, so why not? Guess I'd better look into a gib key puller!

By the way, I like your balancing stand. Should be adequate enough for the job at hand.

[Gippslander]

+ 1 for 38ac's balance method . It works great and you don't need a precise level stand to do it . I used a tin can and added weights to the can , some bolts and nuts . Be patient and recheck it a few times to make sure you have it correct Mike

[BruceM]

For the trial dynamic balancing using 38ac's method (with actual base and floor system, at desired rpm and load)  I like Sculpy brand plastic clay, which sticks inside the rim nicely.   

[George A]

Okay..........I've made a decision (drum roll).

After watching my Vidhata very carefully while running, I've come to the conclusion that any vibration is being caused by the base that I built. It was never intended as a permanent solution, just something I could roll the engine around on while playing with it. I've already described it in another post, and frankly, when sitting on the casters it only has four small points of contact with the floor. Any slight springiness in the frame compounds the tendency to vibrate up and down. When sitting on certain level spots on the garage floor it doesn't bounce......just sits there making electricity. Get one of those casters in a low spot and the tendency to hop a bit kicks in.

As I also mentioned before, the engine appears to be quite well balanced and I think I'm letting my imagination get away with me when I start to worry about "ultra balance". It runs just about as nice as 38ac's in his videos AFTER balancing. Sometimes a guy can get lucky!

So, I'm going to frame up a box on top of my garage floor, measuring 4.5 feet long by 3 feet wide and 10 inches deep. According to an online calculator, that works out to a minimal weight of 1496 lbs. worth of concrete, and I might make it 12 inches deep....1995 lbs. Before pouring, the surface will be cleaned and one of those horse mats cut to fit in the bottom of the box. A rebar cross hatch will be installed about three inches up from the mat and the hold down bolts (3/4 inch by 16 inch) will be anchored with the ends bent under the rebar. There will be eight bolts, two on either side of the existing frame cross members. The concrete will be poured around the rebar/bolts and leveled. Several days will be allowed for curing and the engine/generator assembly lowered on top with my fork lift. Steel wedges will be placed under the cross members to keep the frame level, about 1/2 inch above the concrete, and then a rich sand/cement slurry poured in, forced under the cross members and leveled. After that cures for at least a week or more, steel cross straps (3/4 inch by 2 inch) will be placed over the bolts so that each frame cross member is pulled down firmly....a "four grunt" tightening sequence.

This arrangement has several benefits....
1.) Mass......what the Lister book calls for
2.) Serviceability......the entire engine/generator package can be removed and fork lifted out if necessary.
3.) Height......cranking will be a no stoop exercise and all components can be reached from a standing position.
4.) No permanent change to the existing floor. The entire block can be fork lifted out if necessary by running chains through the bolts.

Opinions? Suggestions? Laughter?  

[mike90045]

.... Several days will be allowed for curing and the engine/generator assembly lowered on top with my fork lift. Steel wedges will be placed under the cross members to keep the frame level, about 1/2 inch above the concrete, and then a rich sand/cement slurry poured in, forced under the cross members and leveled. After that cures for at least a week or more......

I'd let the concrete wet cure for a month if possible, before placing the engine.    A week (of proper wet cure) gets you the minimum strength, but as long as it's wet, it will continue to strengthen.
 The J bolts should NOT contact the rebar - they should clear each other by half inch.  Grease the threads of the J bolts, put a fender washer on them and a nut, maybe a spacer, to keep them from sinking down into the wet concrete.  Maybe a wooden jig the shape of your engine frame, to precisely locate the J bolts.
And you should be sure to vibrate the concrete in, so it flows around the rebar nubs and all the corners.

 Packing a sand / cement slurry is not the same as bedding grout, and may turn to dust

I used some oak flooring strips as an interface buffer between my steel frame and the concrete.  I like to think it dampens the noise a bit and maybe keeps the steel from pounding the concrete to dust.

[George A]

Good point on the concrete.....it takes 28 days to reach full strength and I guess I can wait that long. After the engine is positioned, the grout will take an additional three days minimum, according to the manufacturer....a longer, stronger cure than the normal stuff which cures in a few hours. I should have mentioned that the grout is a standard type for setting machinery and has a non shrinking additive, unlike plain sand and cement available when old engines were set in place.

Thanks for the tip on the J bolts too and yes, I had planned to have them in a wooden "template" to keep their positions straight. Using that method they won't need washers to support them while the crete is drying.

I don't have a vibrator so my only option is to use a wooden stake and punch the heck out of it while it's being poured. Come to think of it, the local contractor might loan me a vibrator so I'll have to talk to him.