People say that Honu putters feel good at impact, using words like "smooth" and "pure".
To understand more about the way putters feel in you hands, we measured how putter shafts vibrate. That vibration is how "impact feel" gets from the putter head to your hands. Vibration speed is affected by factors like shaft stiffness and the putter head weight, but in this study we focused on the vibration direction. How much does the shaft vibrate along the target line - on-axis - and how much does it wiggle in other directions - off-axis - toward/away from your body, and up and down? Target-directed on-axis vibration helps you "feel the distance", while off-axis vibration is confusing and unpleasant.
Honu Putters measured vibration with the "3-axis accelerometer" in a smartphone. That accelerometer primarily senses gravity to know the orientation of the phone, so the display rotates when you hold the phone sideways. The accelerometer can also sense vibration to tell when you shake the phone. A simple clamp - made from the same bamboo that's in Honu putters - attaches a phone to a putter shaft, as shown below.
We recorded accelerometer readings for putts with a heel-shafted Odyssey putter and a Honu putter, uploading them to a spreadsheet for further analysis. This graph compares on-axis (target line) vibration to vibration in other directions.
The key lines are the "Jitter" ones, showing the percentage of undesirable off-axis vibration compared to good on-axis vibration. Notice how the Honu putter jitter (green line) peaks at 15% right after the initial impact, then quickly dies out. The Odyssey putter jitter (brown line) peaks at 35% quite a while after the initial impact, then lasts for a long time.
Since the Honu shaft is directly behind the ball impact point along the target line, most of the vibration is aligned with the target direction. With a Honu putter, the feedback you feel is pure, in the direction you want the putt to go.
The heel-shafted putter twists and turns, vibrating in several directions, because the ball impact, even when perfectly centered on the face, is offset from the shaft. The feedback is misleading.