I am back project time again

[uptown47]

I'm maybe wrong but I can't see how measuring this so accurately really matters. All you need a figure that is 'roughly' correct. Then you can base future workouts on benchmark workouts that you have done in the past.

It might as well be onions and apples... you pedalled for 80 onions and burnt 100 apples.... the next time you ride you pedalled for 84 onions and burnt 110 apples... the hmi shows how many onions and apples you are currently on.

It doesn't have to relate to anything in the physical world as long as the values are consistently calculated and repeatable.

 

[Lancie1]

It doesn't have to relate to anything in the physical world as long as the values are consistently calculated and repeatable.

True, the calculations wouldn't have to relate to real calories. But if Peter wants to compare the energy used to eating a certain amount of candy or hamburgers, then it would be nice to at least be inside the ball park.

The front gear cluster has three different ring gears and the back cluster has nine ring gears, remembering that this is a mountain bike for hill climbing.

If I understand, then unlike most commercial cycle exercisers (that have only 1 gear but attempt to adjust and measure the work-resistance on the rolling wheel), you are using a real bicycle with gears, so that the rate of work done will change with the gear ratio.

In which case I don't think your method of calculating the gear ratio based on the relative speed of the pedals-versus-rear wheel will work very well. A rider can slack off on his pedaling speed (or not pedal at all) while still being in the same gear. When he coasts, it will cause your your gear-ratio calculation to be wrong.

What other method could be used to send the selected gear to the PLC? You could use a thumbwheel switch. Possibly the chain on the 3 front sprockets could be sensed with 2 or 3 prox switches. The rear 9 sprockets are probably too close for prox switches to be able to differentiate.

An alternative might be to just use the high gear, and then use some device as you said to apply resistance to the rear wheel, and calculate the calories needed to overcome the resistance at the one known gear ratio.

Actually doing some thinking here for once instead of just reacting, the work done at the rear wheel to overcome some force or resistance is going to be the same, regardless of the gear ratio. The gear ratio only controls how fast the work is done by the rider, not the amount of work. It is the same as climbing a hill. It takes the same amount of calories to get from the bottom to the top, whether you do it fast or slow. The only thing that changes is the rate of calorie burn, not the total amount.

Do you really need to know the gear ratio to calculate calories burned?

 

[blueyedpeter]

You are quit correct , I was more worried about the update rate the response the last time I tried this on a model the number stored in the register was less than impressive. It seamed to lag the application and was less than expected so it looked like it was measuring cubits or Lego blocks but not rpm .There might have been a problem with the input, so I thought I might get a second opinion on how to write the code.

 

[blueyedpeter]

your right about the rate of burn but i was concerned that while sitting on your blotter and pushing into each effort is some what different and your heart rate will let you know , if you have to get on your toes and run with it . And it is about rate of burn so i am not sure how i would differentiate between short sprints over a shorter time period verses a longer drawn out grind over a longer period. Both will get you in the end .

 

[blueyedpeter]

When you see these computrainers in action they are really impressive from an automation point, they have already GPS plotted famous bike rides and the load device on the back wheel loads up as if you were climbing a hill and when you are descending down a hill it turns into a motor and motors the back wheel.
BUT the really impressive part is that you can race other people in other parts of the globe and actually ride the equivalent of the tour de France.

 

[Lancie1]

. . .and the load device on the back wheel loads up as if you were climbing a hill and when you are descending down a hill it turns into a motor and motors the back wheel.

It seems that you should put most of your effort into perfecting the load device. If you can simulate the energy loading correctly, that will be a large part of simulating a real bike ride. For the other stuff, it comes down to using a bunch of input devices to monitor the gear ratio and the rate of rider energy expenditure in any 1-second period, not just the total work done over a longer period of time.

A DC motor/generator connected to a battery would be one way to simulate the load. When riding on level ground, if left engaged, the generator would provide a load that could be tailored to be proportional to the energy needed to propel the rider and bike weight. When climbing, it is accepting power at a ratio equal to the steepness of the hill, when descending, it runs as a motor and puts power into the wheel at the same rate as the slope of the downhill.

You could use PLC sequencer instructions to step through the different hill slopes, and the time period at that slope, for each ride.

 

[uptown47]

I presume, if you are talking about 'powering' the wheel as well as restricting it, then you are going to mount the bikes back wheel on some sort of roller and use that to power the wheel or provide resistance??

Originally I thought you were only intending on apply 'braking' direct to the rear wheel.

?

 

[blueyedpeter]

At one point in a post i mentioned that in the US you can buy a kit that retails for around $2400 US dollars and it is complete , but it not only creates resistance against the back wheel it motor drives it as well , the units that i have built up are magnetic only and generates load on the back wheel .

 

[GlennA]

I'm not trying to be a kill joy, but have you asked yourself is you are ready and willing to invest the money, time, and talent required to duplicate a $2,400.00 trainer ? Or will you be satisfied with a simple home-built unit ?

 

[blueyedpeter]

Your not a kill joy

You cant be any more correct if you tried glen , i would have to ask how many coconuts have fallen and hit me in the head recently , the answer is two many , but its not only about the trainer it was more about climbing a mountain , being more involved in plc work i just chose to build somthing and put my stamp on it .
And so why do people climb mountains any way .The veiw must be somthing , its a long way to go just to burn off a couple of million killojoules and take a photo when you get there.
Then there is the walk back to the car .

 

[Lancie1]

At one point in a post i mentioned that in the US you can buy a kit that retails for around $2400 US dollars and it is complete , but it not only creates resistance against the back wheel it motor drives it as well , the units that i have built up are magnetic only and generates load on the back wheel.

You need to look at how the new electric vehicles use regenerative braking to recharge the battery. With computerized electronic switching that monitors the power flow, when the vehicle climbs a hill, the motor/generator acts as a motor, when it descends a hill, the motor switches to generator mode and recharges the battery. Your bike should work similarly. The main difference between a DC motor and a DC generator is the direction of power flow.

 

[blueyedpeter]

The other control variable when using an alternator, would be that when you are generating power you need to increase field strength to generate voltage, and when motoring is required at times you need to weaken the field strength and just how much of either you would have to do would be a bit of a mystery .
And an average alternator can produce 70 to 90 amps, and in one instance it is load orientated ( current) and in the other it is speed orientated { controlled rpm) and both outputs are to be clearly defined.
Too much or too little, and then there’s the range of control.
And you could bet they would be both different.
You need too produce enough range to be effective in each application that the alternator will be used in.
So I am pretty happy with the magnetic units as they fit the situation closely but not exactly, and as I said before they were intended for a cycle, and as they were very manual and mechanical but they are now driven by a small electric motor and gear box for control purposes.