The bow should move freely along the bow wheels, should contact the string blade with a slight pressure, and always have some rosin on it. (It will play without rosin, but sounds better with it.)
To check that the bow moves freely in the bow arm, attach the bow line holders and unhook the bow line from each of the bow hooks. Lift up on the servo rod to make sure the bow hair is not touching the blade, then move the bow back and forth by hand. It should glide smoothly and lightly with no binding, almost as if it weren’t even in the assembly.
Here’s another test if you want to take the bow arm off the violin. Hold the bow arm vertically while holding the bow extended fully above it. Let the bow go and it should smoothly run its full length down without stopping. (In the example on the left the bow wheels were adjusted too tight and there was too much rosin buildup on the bow hair wheels, therefore the bow didn’t move.)
If the bow is too tight in the bow arm, first take the bow out by loosening the Bow Idler Wheels (700540) and the Bow Hair Guides. The bow should be easy to remove from the arm at this point by sliding it out sideways from the wheels. As with all bows, do not touch the horse hair as it will pick up oil from your fingers and not function optimally.
Rosen buildup is normal on the entire bow mechanism. After removing the bow from the mechanism, clean the bow (not the hair) with a cleaning product such as 409 and a paper towel. Also clean as much of the bow arm as possible by first scraping off caked on areas of rosin, then with 409, trying to avoid the rubber wheels as much as practical. Try to avoid forcing rosin into the areas where the wheels ride on the axles.
Once everything is cleaned up (it doesn’t have to be perfect, but it is nice to see the gold plating once in a while) use an Exacto Knife to gently and carefully scrape the rosin off the 4 elongated Bow Hair Idler Wheels (700530). An excess of rosin on these wheels can cause the bow to move less freely than desired. Don’t overdo it with the cleaning as the rosin will come right back once the instrument is started up again.
Finish cleaning by putting a drop of thin oil (sewing machine or 3 In One oil) in the cupped end of each of the bow hair idler wheels, and in-between the wheel and retainer on each of the bow wheels, as illustrated on the right. (Note: Do Not Get Oil On The Bow Hair Wheels!) Do not over oil as the excess oil can get on the Bow Hair Wheels and transfer to the horse hair which would degrade the sound quality. After the oil is applied and has had a chance to penetrate through to the axle, clean the application area off with a Q-Tip to make sure that excess oil does not seep on to the bow hair.
Once the Bow Arm is cleaned and oiled, use a back & forth bow motion to carefully slide the flat bow hair back (sideways) in-between the Bow Hair Wheels the same way it came out. Then place the bow itself back over the Lower Bow Idle Wheels, lower the Upper Bow Idle Wheels down to meet the bow (but don’t tighten them yet), then swivel the Bow Hair Guides back into place and tighten them down. Make sure the Spreader Bow-Hair Guide (the one with the 3 pin-posts) spreads the bow hair evenly across. This keeps the horsehair from bunching up when the violin is played at an angle.
Finally, loosen the Upper Bow Idle Wheels so that the bow is free to “roll” back and forth along its full length. The bow is not the exact same diameter from one end to the other, so it is important that the wheels are adjusted to accommodate the bow at its “thickest” diameter. At this point there should be at least .010” of clearance between the bow and the wheels. The bow should be able to “rattle around” a bit between the wheels at its thickest point. The function of the bow wheels is more to generally guide the stick part of the bow than it is to constrain the bow. Once this condition is met, carefully tighten the Upper Bow Wheels down making sure that in tightening them they maintain their “loose” distance from the bow. There should be no drag on the bow as it moves back and forth. In fact, as the bow is pushed back and forth by hand with a slight downwards pressure against the Lower Bow Idle Wheels, the Upper Bow Idles Wheels should not even move. This is the ideal condition, and what we mean when talking about clearance between the bow and bow wheels.
Finally, replace the bow arm mechanism on the violin. Don’t forget to remove the bow line holders before turning the instrument back on. And it couldn’t hurt to wipe the ends of the bow hair wheels one last time to insure no oil seeps onto the bow hair.
There are 2 ways to set the bow angle. Automatically, using the calibration button inside the Cradle Base, and manually, using the turnbuckle servo rod adjustment attached to the left side of the bow arm.
After attaching the bow for the first time it is desirable to use the automatic calibration button to set the bow angle. There are a number of variables that can affect the bow’s angle in relation to the string driver, including servo height, servo position, servo arm placement, servo rod length and distance from bow arm to blade. Damage to the string driver can occur by simply attaching the bow arm and turning the unit on if the bow is too far out of calibration and pulls down too far. Starting with the automatic calibration will prevent such a situation and give you a good starting point from which to fine tune.
To automatically calibrate the bow angle, make sure the bow is properly mounted, bow line attached, bow line holders removed, and open the violin case. Next to the PC Board, at the far end of the case, is the bow calibration button. When the instrument is turned on and you are ready to calibrate the bow, press the button for a few seconds until the bow starts to move. When the bow starts to move, carefully close the case and let the bow self-calibrate.
After the bow angle has been automatically calibrated, it may be desirable to manually fine tune it by adjusting the servo rod attached to the left end of the bow arm. While playing a piece, back off on the adjustment until the bow is just off the string, then bring it back down until the desired about of bow interaction is achieved. Down = more bow interaction, Up = less bow interaction.