Powermeter
 

Ok you laughing stock. I decided to spend few minutes thinking about possible design for cheapo power-meter.

1. I'd build it into bike pedals.
2. I'd use load sensors that are being used in digital scales. They cost peanuts while providing good accuracy.
3. Each pedal would have 2 sensors measuring pressure orthogonally so that the resulting force vector could be calculate later by cycle computer.
4. Each pedal would have built in single Ant sport unit to transmit data from sensors and a small battery to power it up.
5. I did not do any research for Ant capable head unit but since the existing ones cost about $100 retail consider this as a price ceiling.

If made nicely I think that the whole thing should be around $300-$500 retail.

Pros: Continuous measuring of force for each leg independently.
Cons. Need to manufacture own pedals.

Now rip it apart

1. Someone is already working on it... I don't remember the name but it's been vaporware for a while
2. I'm not sure that would handle torque from different angles. Pulling up? Do you have any idea how much force goes through the pedal? On my ride today my max torque was 1800lb-in... that's 264lbs of force. I don't know if those kinds of sensors can handle that much load. I know my kitchen scale only goes up to a few pounds...
4. I don't think the Garmin would be able to handle to signals... I'm not sure if that means the ANT+ protocol can't handle it though. You may need to combine signals from both pedals and retransmit it. Also, power is torque x cadence so you also need something that can measure cadence.
5. 100??? What ANT head unit are you looking at that is $100?

Well as I said I spent few minutes (less then 5 I think) so I have no idea if someone is working on it.

2. Orthogonal is the keyword here, you measure vertical/horisontal push/pull, from that data you can extract true force vector. 264 pounds is nothing. Those can handle much higher loads.

4. Garmin will not be able to handle those directly. I was talking about having your own head unit. If one wants to use Garmin then either Garmin's firmware has to be updated, or extra ant unit with small controller has to be added to convert all signals to a single power value. It is easier I think to produce one's own head unit but yes communicating to Garmin would have great advantages since it does much more then just measure power and it looks to me that Garmin is well on it's way to become bike computer of choice for people with money.

Found it Here

So this could be something interesting, not for me though ...

Isn't that exactly what you are trying to do?

btw, this and this are what I was thinking of...

If Brim Brothers can make it work, it would be a great solution for multiple bikes, even tandems.

And build it into shoes, not pedals, and it's even more versatile.

Biggest problem I see is the up force, but perhaps you could compensate for that in the calculations.

+1 - nothing really to add, but there are definitely people who have been experimenting. Doesn't mean there is no room to look into it further.

The concepts of using the sensors in the shoe inserts (not a great concept IMHO) and in the pedals have already been patented.

LOL. Nice links ;) "Not for me" part means that I just did some mental exercise but I am not really interested in making powermeters

"We would like to take this opportunity to thank all our customers who placed Pre-Orders"

wonder if their customers got refunds