Help for balancing

Mounting the balancer on a machine base
The balancer mounts with 1/2-13 bolts into 5/8 inch t-slot nuts. Keys built into the bottom of the uprights and main base are sized to fit the 5/8 inch slot in the machine table. The fit of the keys will vary as a result of the manufacturing tolerance of different machine bases. There can be as much as 0.005” slack in the fit of the keys on some tables. To obtain accurate alignment, push or pull the upright or motor base so it will square up against the side of the t-slot.

Connecting cables
Make sure the cables are routed in a way that gives them clearance from rotating parts. Connect the cables to the computer and secure them with the small retaining screws. The small cable with the round connector attaches to the left side of the motor speed control box.

Encoder wheel adapters and thrust control system
The slotted wheel with a black hub is the shaft position encoder wheel. Adapter tubes are used to properly mount the encoder wheel to a shaft and are retained with a mounting stud threaded into the crank. A knob threads into the crank adapter stud to retain the encoder wheel. The adapter should be aligned with the crank snout so it will run true when spinning. If a harmonic balancer is installed, there will be a small amount of bore remaining to align the adapter. The white beam mounted on the encoder head fits in the groove of the encoder wheel hub. This provides thrust control for the shaft and allows you to position the shaft at the best location. Place a very small amount of oil in the hub groove.

Rotary encoder positioning
Secure the encoder head at a position that puts the thrust control beam on the approximate centerline of the shaft.

Belt placement and tension

Machine software settings
Shaft RPM is the speed the machine will reach before sampling the shaft. 500 rpm is the normal setting. You can increase the speed for higher sensitivity when the shaft is fairly well balanced, or lower the speed for large or highly unbalanced shafts.

Left or Right Lag compensation is used to fine tune the balancing machine to make the displayed unbalance point match the actual heavy point on the shaft.

Weight of empty bobweight is used by Bobweight Assist to calculate the amount of weight to place on the bobweights. This value must be the weight of an empty bobweight including all mounting and disk retaining nuts.

Sample Quality of 1 is used if you have a slow computer and want the machine to acquire shaft data more quickly. A setting of 2 is normally used. If you don’t mind increased shaft sampling time, use a setting of 3 for maximum accuracy and repeatability.

Right upright must be set to Reversed when you need to flip the right upright around to allow a more narrow spacing between the uprights.

Weighing parts
For balancing mulit-cylinder engines, the parts need to be weight matched. Find the lightest part of a certain type, like the lightest piston, and remove material on the other parts until all the parts are the same weight within a tolerance of 2 grams or less. For racing engines the tolerance should be 1 gram or less. Connecting rods need to be weight matched on each end. Weight match the big end of all rods and then match the total weight of all rods by removing material from the small ends. A rod weighing fixture is required to find the big end weight of a connecting rod. For the proper bearing weight to use in the Bobweight Assist, enter the weight of a pair of bearing inserts, the 2 halves of the bearing used in 1 rod.

Bobweight calculation
Click the Bobweight Assist button or press B on the keyboard to display the bobweight calculation page. Enter the weight of each part and the program will automatically calculate the total bobweight after each entry. The default engine type is a V-8. Click the Select Engine button if the bobweight is for a different engine type. Make sure the Empty Bobweight displayed matches the weight of your bobweight. This is the weight of an empty bobweight including all journal clamping and disk retaining nuts.

Reciprocating and rotating weight percentages
Different engine types use different reciprocating and rotating weight percentages for bobweight calculation. A standard V-8 engine uses 50% of reciprocating weight, 100% of rotating weight, and has 2 cylinders per bobweight. V-6 engines can vary greatly because of the manufacturers design. A V-6 may use 36.6% of reciprocating weight, 100% of rotating weight, and have 1 cylinders per bobweight. You can select the engine type in Bobweight Assist and the software will set the percentages for you, or you can manually enter the values.

Proper placement of bobweights on crank

Storing, retrieving, and printing bobweight information
Bobweight information for each job can be stored on the computer and recalled at a later time. Windows 95 and later uses long file names, so you can be very descriptive with the name you give the file. This is very helpful when you have a lot of jobs stored. You can also have sub-folders to group different types of jobs so it will be easier to find them.

Overview
When the shaft is properly placed on the balancer you should rotate the shaft manually to make sure there is adequate clearance of all rotating parts. Check the belt tension and make sure the tension arm nut is tight. Use a small amount of oil on the delrin V-block bearings and in the groove the thrust control beam fits into. Make sure no person is near the machine before spinning the shaft. Always keep safety in mind and remember that rotating power equipment is dangerous.

Power switch
The motor power switch is located on the right hand side of the motor speed control enclosure. For safety reasons, make sure this switch is in the OFF position at all times except when you are spinning the shaft. The switch can be used to stop the motor in case of emergency when you are away from the computer keyboard.

Balancing speed
500 rpm is the normal speed used for spinning a shaft. You can increase the speed for higher sensitivity on small shafts or when the shaft is fairly well balanced. A lower speed is used for large or highly unbalanced shafts. Some shafts may give better results at a certain speed. For example, a certain shaft may cause inconsistent readings at 500 rpm, but it may work very well at 600 rpm. This is an unusual condition, but surface finish of the journal, shaft size and weight, etc. can have an effect at certain speeds.

Correction radius
The correction radius is the distance from the center of the shaft to the area you will be removing or adding material to balance the shaft. For example, if you are balancing a crankshaft with 6 inch diameter counterweights, set the radius to 3.00 inches. If you are drilling in an existing hole on the left side, measure the distance from the center of the shaft to the bottom of the hole and enter this dimension for the left radius by clicking the left Radius button.

Correction plane offset
Set the distance between uprights to match the inside to inside edge measurement between the uprights. This assumes the contact patch of the delrin V-block bearing is centered over the inside edge of the upright. If the bearings are set up differently, use the measured distance between the center of the contact patch of the bearings on each upright. Measure the distance from the contact patch center to the point on the shaft where the correction will be made. Enter this dimension into the plane offset. If the plane offset is a point between the uprights(inboard correction), you use a positive number. For a point that is not between the uprights(outboard correction), use a negative value. The arrows on the display will move when you change the offset values and be positioned to show where the correction plane is located.

Add/Remove material
Click the Add/Remove button to alternate between ADD MATERIAL and REMOVE MATERIAL modes. Use the remove material mode when you need to remove material from the heavy side of the shaft to bring it into balance. The add material mode is used when you when you need to add some type of weight to the light side of the shaft to balance it.

Spinning the shaft
After the shaft is properly set up, roll it through one complete turn to verify all parts of the shaft have adequate clearance for spinning. Check the belt tension and make sure the motor tension adjustment arm nut is tightened. Move the motor power switch to the ON position and step clear of the machine. Click the Spin button or press S on the keyboard. The machine will automatically spin the shaft to approximately 150 rpm and perform a shaft unbalance check to make sure if it is safe at the planned final shaft speed. Next the machine will increase the shaft speed until it reaches the desired sample speed or the lowered safe speed if the shaft is very unbalanced. After the shaft reaches the proper speed it will acquire the unbalance data and shut down.

How to interpret the readings
The readings of the shaft unbalance have 3 components. Two values, unbalance grams and degrees, are computed from the data collected during the spin. Radius is the value you set as the correction radius for adding or removing material to balance the shaft. If you are drilling to remove material and balance a 14 inch flywheel the radius could be set to 6 inches. This would make your drilled area 1 inch from the outside edge of the flywheel. If the display says 17 grams at 247 degrees you would need to rotate the shaft until the display says “Shaft Position 247”. This places the heavy spot at the top. Now you know to remove 17 grams 6 inches from center at the position that is straight up. If you change the radius to 3 inches, the display will read 34 grams. Both readings show an unbalance of 102 gram inches. The smaller the correction radius is, the more mass you have to remove to get the same result. The formula for unbalance is grams times inches of radius, or for example 102 grams X 1 inch = 17 grams X 6 inches. Also, as noted before, the machine reads position in degrees referenced from the top of the shaft. This makes the heavy point line up with a drill bit if the balancer is mounted in a machine with an overhead cutting tool, such as a milling machine.

Setting shaft zero
Roll the shaft to the position you want to be zero degrees, then click the Zero Shaft button. The display will now read 0 degrees at this new position.

Drill Assist
The Drill Assist window tells you how deep to drill the shaft to make it balanced. Radial compensation is used if you are drilling toward the center of the shaft, like drilling the counterweight of a crankshaft. This automatically adjusts for the effective radius decreasing as you drill. If you drill a 3 inch radius counterweight 1 inch deep and re-spin the shaft to find you need to drill more, you need to set the radius to 2 inches because your radius was decreased by 1 inch when you drilled the first time. The software will use the new 2 inch radius to calculate the proper amount to drill. If you are not drilling radially, such as drilling the face of a flywheel, turn radial compensation off.

Balancing strategies
Some crankshafts are a challenge if you do not want to use heavy metal to add weight to the counterweight. The unbalance point may be just off the edge of the counterweight where it cannot be drilled. The external weight, flywheel or harmonic balancer, can be modified by drilling or welding on extra weight but this is not recommended. If you modify the external weight, then if the harmonic balancer or flywheel ever have to be replaced, you will have to balance the new part to match the one you are replacing. The owner of the engine may not be aware of the modified part for various reasons and will likely install a replacement part only to end up with an unbalanced engine. One way to gain more effective counterweight is to drill in the rod journal. Many times the factory that made the crankshaft or engine has already drilled one or more rod journals. If the factory hole does not go completely through, you can usually gain several grams by drilling it deeper. If you drill a journal that has never been drilled before, you can remove a lot of weight, but be very careful to drill at the proper place or angle to avoid intersecting one of the oil passages that exist in this area. If the spot you need to drill is just off the edge of the counterweight, sometimes you can drill one of the middle counterweights. Try to drill a spot beyond the point that is unbalanced so you can roll the unbalance point up onto the end counterweight. If you want to move the unbalance point of a shaft to a different position, you can drill in a position away from the direction you want the unbalance point to move. For example, you have a shaft that is 20 grams unbalanced at 100 degrees, but 100 degrees is near the edge of the counterweight and you don’t want to drill there and chance having the heavy point roll closer to the edge where you cannot drill. You want to drill at about 60 degrees, which is closer to the center of the counterweight, but this will roll the heavy point past 100 degrees and off of the counterweight. If you drill at 110 degrees, which is very close to the edge, you reduce the unbalance to 7 grams and the heavy point is now at 80 degrees. The more you drill at 110 degrees, the more the unbalance point will move away from the point you are drilling. Now you can drill a very small amount at the new position, say 70 degrees, and complete the balancing. These basic methods will work for any type of shaft, and are helpful when you can only modify the shaft in specific areas.

Acceptable Unbalance
For race engines an unbalance of 2 grams or less is considered to be properly balanced. Street engines should be balanced to 4 grams or less.

Erratic readings
There are several things that can cause inconsistent readings:

Oil holes, slots, etc. that run on the V-block bearings of the machine will “bump” twice per rotation as the shaft spins. Use the thrust control to position the shaft to a smooth area.

Some shafts have a fillet radius where the journal diameter steps up to a larger size. This radius may not run true to the bearing surface resting on the balancing machine. If the V-block bearings of the machine are allowed to rub against this radius, the balancing machine will read the runout of the fillet radius as well as the unbalance of the shaft. Use the thrust control to position the shaft away from the fillet radius.

Make sure there are no loose parts on the shaft or bobweights.

A flywheel that does not fit the shaft tightly will cause improper balancing. A 30 pound flywheel shifted .002” from center will cause 27 gram inches of unbalance. 30 pounds X 454 grams per pound X .002 inch = 27.24 gram inches. A properly tensioned belt and well lubricated shaft/V-block will give better results.

Machine will not spin
No Hardware Found means the program can’t communicate with the balancer interface board.
Make sure the board is properly seated in the motherboard slot.
Try a different slot.
A jumper on the board has a default setting of 0-C, move the jumper to C-1. Exit and restart the program after moving the jumper.

The fuse may be blown.
Make sure the motor switch is in the OFF position before opening the fuse holder.
Always replace the fuse with the same current and voltage rating.
Power switch in OFF position.

Program window size, font size
The program screen size is based on a display resolution of 640x480 pixels. If your computer display is set to a high resolution it will cause the balancer program window to be much smaller than the screen. If the system font is scaled to more than 100% the balancer program will adjust to a larger size. To make the balancer program fit the screen, adjust your computer display properties to 640x480 pixels.