It uses an accelerometer sensor at the grip end of the club to calculate club head speed.
He’s loving it however we’ve noticed that the reported swing speed looks very high. He was radar tested a few months ago and his swing speed was around 78mph. He might have improved, but…
The Mobitee PIQ sensor consistently shows his swing around 105-115mph! That speed would put him up with the PGA Pro Tour players!!!
He is using a 38 in. finished club length Driver. I believe a standard Men’s driver is 45 in.
Can anyone help me figure out how I can calculate the actual club head speed given that the club is 7 inches shorter than a standard club?
By the way I’m prepared to discover that this is maths that a 6 year old could figure out!!!
How does it know when ball contact would be made? Possibly the swing is faster past the sweet spot. I would guess about 84% of what a standard driver would read.
Presumably the “sensor” is a gyro + accelerometer. Accelerometer tells you how fast the grip is moving, and the gyro tells you the angular speed. Add the linear velocity of the grip + rotational velocity of the grip x length of the club, and you get the velocity of the head.
But without knowing the separate measurements, it’s impossible to correct for the length of the club. It’s not a fixed percentage error. The best you can do is assume (approximate) that the velocity of the head is much greater than the velocity of the grip, in which case you can ignore the velocity of the grip and just apply a 38/45 correction factor.
Are you sure the software doesn’t allow you to input the length of the club??
Wouldn’t the club head speed be at its maximum as it hits the ball? It must be accelerating all the way up to the collision, and then lose a fair amount of kinetic energy in the collision.
Thanks for the responses so far - the PIQ/Mobitee sensors have no way of knowing impact speed or smash factor - hence they can only give actual distance measurements if you walk to the ball (via GPS)
Some other systems (like Zepp) DO allow you to edit the club length to allow for ladies/juniors clubs, however at the moment the Mobitee system doesn’t - hence why I was trying to see if there was a way to manually calculate based on the club length and reported speed (which assumes 45inch length) - if Zepp does it using almost identical hardware - surely it must just be a calculation…
Is there any chance the readout of your machine is set in kilometers per hour instead of miles per hour? 78 mph is 126 or so kph, so the difference you are citing is in the ballpark of the conversion from imperial to SI.
But as I said earlier, just because it’s a calculation doesn’t mean it can be reversed. In this case you have Vh = Vg + L x Wg, where Vh is the velocity of the head, Vg is the velocity of the grip, L is the length of the club and Wg is the angular velocity of the club (measured at the grip). To recalculate for a different L, you have to know Vg and Wg separately. You can’t backtrack from just Vh.
The closest approximation you can make is to assume Vh >> Vg, in which case Vh = L x Wg. So in this case you can make the correction (Vh2 = Vh1 * L2 / L1). In other words, multiply the readout by 38/46.
Thanks, I think my relatively innumerate brain can understand that, so 100mph could be approximated to 88mph…
Sounds about right, thank you for the explanation scr4, my 11 year old will be gutted to hear that he is in fact NOT swinging as fast as Rory McIlroy , however he is (probably) swinging faster than 3 months ago!
I think you will have to do manual as suggested above. From the FAQ at the website:
“Club speed is measured in miles per hour how fast your club head is traveling at the point it impacts golf ball. Value is calculated from hand speed measure with standard club height (base on which club you are using).” Bolding mine.
scr4, why do you think the sensor needs to take a separate measurement of angular velocity?
The required data are the speed at the sensor, along with two fixed distances - from the center of rotation to the sensor, and from the center of rotation to the club head. The speed of the club head is just the speed of the sensor scaled up by the ratio of these two distances.
Although this assumes that you don’t add much velocity to the clubhead by turning your wrist. Maybe that’s not a reasonable assumption?
Ignoring wrist action, the adjustment you would need to make is as follows, with all distances taken from the center of rotation which I assume is somewhere mid-chest (I’m not a golfer):
(a) for a full-length club held by a full-sized human, estimate the distance to the end of the club, and divide this by the estimated distance to the sensor position near the grip.
(b) for your son holding his club, do the same thing.
Adjust the speed by the ratio (b)/(a)
The values (a) are the lengths that the device is assuming to make its calculation. Of course, if you can find those assumed numbers directly in the manual, of course you don’t need to measure them.
That would be true if the entire club was rotating around a fixed point, but I think it’s more complex than that. See this photo for example. There is quite a bit of wrist motion involved. Approximating this motion as a rotation around a fixed point wouldn’t be very accurate. Besides, the head moves much faster than the grip, so it wouldn’t be very accurate to measure the linear speed of the grip and extrapolate that to the head speed.
You could make measurements using an iPhone in slow-mo video mode (240 frames per second). Put a calibrated grid in the plane of the swing so that you can measure how fast the club is moving by the change in position in each frame.
, however he is (probably) swinging faster than 3 months ago!