Creating a kayak paddle power meter

Hi everyone,

I'm a total beginner in electronics and programming, my last and only experience dates back in high school when I did like to repair and soldier headphones wires and so on.
At the moment I'm an Olympic coach in kayaking, and a running and biking enthusiast. Both these last two sports improved a lot in the last years with the introduction of power based training.
I know a company which is already selling kayak power meters, but I don't want to make any back engineering.

I'd like to know if it is possible to measure the strain on a kayak paddle shaft, convert it to power, and send the informations to a bluetooth connected sport watch.

I figure out I'll need a board: Arduino (nano 33 BLE or similar?), strain gauges, battery... and a big help!

My optimal specifications should be: Wattage measure (Force*Speed), bluetooth reading on a sport watch, induction charging, and fit everything into a 26mm inside diameter carbon shaft, sealed to keep everything waterproofed (reason why I'd like an induction charger)...

Hope my project will interest you, and I must thank you in advance for your help!

Bets regards

First thought is a load cell in the paddle.
Experiment where and how to place

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Hi,

Thanks for your answer.
I was thinking to position two strain gages inside the shaft, at the hand position as it will be where the force is applied, and probably where the most bending is occurring.

Second thought is about power, and the P=F*V relationship, is the V measure possible to obtain from the built-in accelerometer?

Thanks!

I'm way out of my league on the calculation, but water would seem to be somewhat of a constant. so the force needed to move water, or the paddler, would increase with applied pressure.
the pressure would be less if the energy applied was less.

Is there a different formula or maybe a variation that would fit this condition with just force applied and time ?

Interesting story on the news tonight, that the preferred paddles are made in Taree! :sunglasses:

Interesting thoughts, I’ll dig deeper in the formulas a bit later I think. I first have to figure out which hardware I have to order… yes, I’m a total beginner!

From the start of the chain I need strain gauges, an arduino board to transmit the informations to a « reader », and a power supply. Do I need an amplifier between the gauge and the board to make the signal stronger, or is the amplifier built in the board?

All the best, thanks all!

Most strain gauges come with a amp board/module. That is required and works with the output.
Should be cheap enough to get a few in different ranges

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I wonder why a commercial version of this product sells for 2,900 NZD (about 2,000 USD)...

I wonder too!

I ordered everything and I’ll try to make it. I’ll keep you informed if it works and how it works.
Thanks for infos!

Got a link?

https://shop.onegiantleap.co.nz/

(no doubt took a fair bit of R&D by people who are not total beginners in electronics, programming, mechanics of materials, dynamics...)

Hi,
That shop doesn't give anywhere near enough info about their product.
What data rate?
No example of a readout or screen shot.
How much mass does it add to a regular paddle?
How long on a single charge? etc etc

I'm not saying its dodgey, but they don't seem top know how to sell their product very well!!!

Tom... :smiley: :+1: :coffee: :australia:
PS. Cost so much because they can, niche market. R & D costs. Covid costs.

There's more info on their main website (not the shop).

Regarding cost: yeah. It was a rhetorical question....

If you have to ask you can't afford.

I am guessing lots of professional athletes want the best and donors want first place.

Very small price to pay.

I could see MIT work with the rowing team to make something like this.
Lots and lots and LOTS of testing

Hi all, thanks already for the help you gave me.
I'll order batteries and a inductive charger, and I was wondering if that flex sensor could work (inside the shaft): [Long Flex sensor : ID 182 : $12.95 : Adafruit Industries, Unique & fun DIY electronics and kits]

All the best, speak to you soon!

Is the shaft already hollow?

It will need sufficient length at each end fixed into the shaft to obtain an accurate assessment of the flexion.

If you want to try that type of sensor, look for one with a better datasheet...one that has resistance vs curvature data. I assume you have done at least a little "mechanics of materials" analysis so that you know what ballpark the shaft curvature will be in. With that information, you can decide whether it makes sense to try that sensor.

For starters, try googling flex sensor resistance vs curvature.

Yes the shaft is hollow, and it will bend of approximatively few centimeters when paddling at full power.
I'll try googling a little bit more to understand flex sensors, and find which one fits best.
Thanks for answering!

deflection <> curvature <> angle of bend

I suspect the curvature is quite small and the angle of bend in a flex sensor of reasonable length will be unusably small.

Do the numbers....