For common support issues, check below for SW1, BP1, or the original Twistweight Adapter. You may also reference the SW1 User Guide here or in the app. If you need additional help, please contact me at

SW1 Common Issues

Most SW1 support questions are due to problems with calibration. I plan to improve the calibration process, but in the meantime, perhaps some of the explanation will help.

Big picture, the SW1 is a spring-driven pendulum, and the phone app precisely measures the period of oscillation (time required for one cycle). The square of the period of oscillation is proportional to the moment of inertia of the pendulum, so by knowing the period of oscillation of two known objects (the two calibration rod configurations), the moment of inertia of a racquet can be determined from its period of oscillation. The calibration process “tells” the app how quickly these two known objects oscillate.

Measurement Group Checks

Three measurement groups: This check verifies that there are at least three measurement groups. The calibration process only considers the three latest measurement groups. The latest groups are displayed at the top of the list of measurement groups on the Measure page.

Counts: 1 and 3 equal and not zero: This check verifies that, of the three measurement groups, the first and the last groups each contain the same number (count) of measurements. For a standard calibration, the first and last measurement groups should contain one measurement of the fully-collapsed rod.

Counts: 2 equal to sum of 1 and 3: This check verifies that, of the three measurement groups, the middle group contains twice as many measurements as each of the other groups. For a standard calibration, the middle group should contain two measurements of the fully-extended rod.

Periods: 1 and 3 are similar: This check verifies that the measurements (the periods of oscillation or the time required for one cycle of oscillation) in the first and third measurement groups are similar. For a standard calibration, these groups should both contain measurements of the fully-collapsed rod, so they should be similar.

Periods: 2 greater than 1 and 3: This check verifies that the measurements (the periods of oscillation or the time required for one cycle of oscillation) in the middle measurement group are greater than the other two. For a standard calibration, this group should contain measurements of the fully-extended rod, so the periods should be greater than those of the fully-collapsed rod. For a calibration rod with removable weight, where calibration object #1 is greater than object #2, the check will be “less than” instead of “greater than”.

Calibration Results

After all measurement groups checks are satisfied, the Calibrate button will be active. When you tap it, the calibration results below the button are updated. The spring constant should be between 215 and 235. The Apparatus MoI should be between 5 and 15, depending on the size of your phone. If the calibration results are outside of these ranges, the likely cause is that the calibration rod was not fully-extended or fully-collapsed during the calibration measurements. When fully collapsed, the rod is 20 cm (8″) long. When fully-extended, the rod is 74 cm (29″) long. There are four internal sections (five sections, including the external section). Make sure that you’ve unlocked and extended all four.

When recalibrating after a “bad” calibration, the measurements of the calibration rod will be off. This is fine. The calibration calculations only consider the periods of oscillation, not the moment of inertia (swingweight) values.

Tare Button

Be aware of the Tare button. If you tap this by mistake, the measurement results will be skewed. The button is filled in when the tare function is active and just an outline when inactive. When the tare button is activated, the preceding measurement is subtracted from all subsequent measurements. The tare function is used with the twistweight and pickleball adapters.

Pickleball Adapter

If you’re using a pickleball adapter, make sure that you calibrate without the adapter. The calibration values are valid for the unadapted, 10 cm, measurement position. After calibration is complete, mount the adapter and tare it out before measuring a paddle.

If you’re using the 5 cm pickleball adapter, and your measurements are lower than expected, make sure that the adapter is installed into the SW1 cradle properly. The tabs on the bottom of the adapter should fit between the front and rear supports of the cradle. The adapter should be unable to slide in the cradle.

A top view of the SW1 with 5 cm pickleball adapter installed for visual reference

BP1 Common Issues

Unstable Scale Readings

A couple of customers have reported unstable scale readings when using the BP1. In one case, this was resolved after replacing the batteries in the scale. In the another case, I believe the culprit was static electricity. The BP1 has a fairly large surface that is in close proximity to the underlying surface. If these surfaces are electrostatically charged, the attractive or repulsive force can be large enough to affect the scale readings. This will generally show as a reading that drifts slowly over time, presumably as the static charge dissipates. A charge buildup is more likely to occur in a dry environment, such as when heating your home. You can dissipate the charges by running a damp cloth between the BP1 and the underlying surface and scale.

Truncated Values in the BP1 App

The inputs in the BP1 app for the Racquet and Loaded BP1 weight can become truncated, making them impossible to read, if the system text size setting is too large. I will attempt to make even larger text display properly in the next version of the app, but in the meantime, you can reduce the text size or disable features such as “Display Zoom” while using the BP1 app.

Twistweight Adapter Common Issues (original design, before November, 2023)

When oscillating a racket, the handle wobbles, or measurements vary a lot with small adjustments to the centering of the racquet. If the racquet is secure in the TWA, these issues both indicate that the racquet is not centered. Start by lining up the racquet with the center indicator of the TWA centered between the two center main strings, but you may need to tweak it slightly. When centered, the measurement will be at a minimum, and it will increase slightly as you move the racquet in either direction. I see this issue with one of my racquets, and it appears that the drill registration is slightly off. Note the location of the center dot relative to the strings of the top racquet in the photo below.