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The Delta Factor ^{}

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- Posted by: Dan
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Chronocurl allows you to characterize your Delta Factor, but what is it and why exactly do you need to know about it? Read our latest blog article to find out!
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We had Dean Gemmel at the club earlier this season for his great sweeping clinic Brush like a Badass. He went through the pitfalls of interval timing (timing between back line and hog line) and how subpar delivery technique will affect readings to the point of being almost meaningless.

We haven’t progressed that far since the first use of stopwatches for interval timing almost 20 years ago. We still struggle with the same reliability issues and unless teams stay together long enough to learn the intricacies of their respective deliveries, they usually rely on pacing and hog-hog times.

The whole point is that for most curlers, the amount of time required to match delivery with teammates outweighs greatly the benefits. After all, one has to get the team together and throw draws and split time them *ad nauseam* until you get a sense of how much the guy actually push pulls or drags!

However, it’s pretty clear that if the whole team has similar delivery, using split times is a no brainer. It reduces the amount of error and gives confidence to the sweeper.

What we think at Chronocurl is that by having quick access to quality data on how the player actually performs, we have better chance at fixing issues related to push-pull or drag, match deliveries or at least get very clear insight on what to expect from each players.

**The Speed**

So what goes on with the deliveries that makes split times inaccurate. Well first we need to understand that split timing is used to estimate the speed of the curling rock at the hog line. But, as we pretty much know from driving cars around, speed is not measured in seconds, it is measured in distance by unit of time (km/h, miles/h).

Therefore a good way to measure speed of rocks is to divide the distance between two lines by the amount of time it took for the stone to travel that distance. A shorter time means faster, longer time means slower, but one has to understand that the speed calculated is an average.

Let's use the following example to illustrate the pitfalls of that method:

A race car driver is going to see his mother, who has the tendency of being worried about her son. Before he leaves home, to reassure his mother, he always gives a call so she knows when to expect him. She's well aware of how much time it should take him and if he ever shows up too early, things won't go well.

Being a smart guy, and addicted to speed, our guy races the distance and arrives an hour early into town but instead of going straight home he spends his extra time drinking a coffee and buying flowers for her. When he shows up, everything is fine and he has a great evening.

All the information about the actual speed during the travel has been averaged out and lost, only remains a split time between two points which happen to be what his mother expected. He could have been driving slow coming in the driveway or fast, there's just no way to know from the time and distance alone.

The delivery is pretty much the same, basically, you can get the time for the whole travel of the player from back line to hog line but it will not give you the speed of the rock at the end. Mother is hoping that the player is not hiding some bad secrets such as correcting his hack push with some sneaky knee rub on the ice or some arm extension just before the hog line.

You can ask pretty much any coach, and all will say that good players don’t correct their shots (well at least not too much), they slide properly from the get go. It’s just too much pressure to self-correct while drawing the button for the win in Brier finals; thinking while sliding for victory (or loss) is not an option. So how can you tell, as a coach, if your players are having issues with drag or push-pull?

You can certainly look at their delivery, but what if you could actually get a number to quantify how much they're correcting their shots.

**How Chronocurl gives you data**

Chronocurl can give you two pieces of information. First it can give you the speed of the rock at one particular location. It will do that using the amount of time it takes for the rock to cross the beam, it will give you the average speed of the rock over 12 inches (or the diameter of the rock). Second, it can time stamp the events, which means that if you have two instruments it will give you how much time it took for the stone to travel from one instrument to the other.

These values are crucial to determining what we call the Delta Factor. The Delta factor is just as if your mother was Chuck Norris, it pretty much knows what speed you drove coming into town and compares it to the time it took you to go from point A to point B. Nobody can hide from Chuck Norris.

More seriously, how do we calculate the Delta factor and what is it exactly.

The Delta factor is the difference between a normal split time, one that would normally be obtained with a stopwatch during a game, and the actual speed of the rock at the hog line.

As we’ve discussed previously, speed is the only way to evaluate how fast an object is moving, but since the information available in a game is time between two lines, we need to convert that speed to some number that is in seconds.

The most intuitive way is to use the distance between the lines use for the split time and divide it by the speed (ex. 60 miles at 60mph takes 1h). This calculation is just an estimation of how long it would have taken the stone to travel that distance at the speed recorded at the hog line, not a real split time with drag push and pull artifacts.

Once you subtract that time based on speed with the actual split time you get the Delta Factor.

**The Delta Factor**

The Delta Factor should remain constant for a player over the range of draw weights, meaning that he should never push or pulls and should not modulate his slide distance or drag to adjust weight. Any correction, even minor ones will change the Delta Factor.

Practicing with Chronocurl gives you that number instantaneously and tells you and your coach when you cheat, but the greatest advantage one gains from practicing with Chronocurl is the ability to compare Delta Factors with other teammates. If player A has a delta factor of 0.20s and player B has a delta factor of 0.10s, you know that during a game player A will appear to have split time 0.10s higher than player B.

For players with stable delivery, Delta Factor can be assessed in one practice over the whole range shots, this put a team on the fast track to match their delivery or at least gain awareness rapidly on tendencies each player has.

The Delta Factor can also help you to diagnose your delivery. For example, imagine a player that has practically no drag at the beginning of a practice and end up with lots of drag at the end. Not knowing exactly what the problem is, the player could get frustrated thinking he’s not making the shots, when in reality, his sliding leg getting tired had him lay lower increasing drag from the trailing leg. A good analysis of the progression of his Delta Factor during a practice would send him to the gym to increase his leg strength.