I see. Did you see my point about the throttle? Do you agree that it would not be any good for a "Stoke Monkey" set up?
"stokemonkey" my Tongxin?
- Thread starter kitchenman
- Start date
I am not sure,
If you get the pedal sensor , it would only work when you pedal ( that´s fine).
But if you haven´t got a throtle how are the rpm of the motor set?
You would like it run always close to highest efficiency point but how is this achieve?
If you get the pedal sensor , it would only work when you pedal ( that´s fine).
But if you haven´t got a throtle how are the rpm of the motor set?
You would like it run always close to highest efficiency point but how is this achieve?
My motor/controller is restricted to 2 speeds: low speed/high torque and high speed/low torque. I mainly use high speed/low torque. So in the following video when I turn the pedal the motor starts to spin and as its not under any load I would expect to be close to achieving 175 revs:
STREET MACHINE STOKE MONKEY CHAIN GUIDE TEST - YouTube
When I am riding then I try to make sure that I am in the correct gear for the road conditions and "help" the motor to be at its highest efficiency point.
Thats all well and good hitting its highest rpm limit. But it will also be offering the least amount of torque to the rider. If you wanted it to keep going you've have to get it back down to 100 rpm to get it to really pull you along. But then I guess your cadence would slow down so your not in your own effcieny curve.
D
Deleted member 4366
Guest
You can do it with any bike computer. It's better if you already have a little disk magnet like those ones that are on the back of little badges or fridge magnets. Stick the magnet onto the motor sprocket or use a bit of bluetac to stick it to the aluminium somewhere. Hold the computer sensor in position while the motor rotates and it'll measure the speed. If it's a cheap one that only shows MPH, you'll have to do some maths: divide by the wheel circumference (in miles) and multiply by 60 to get rpm. Some computers give you the cadence (rpm) directly.
Great! .. I have a a wireless cateye that is currently installed on the Spirit. I'll use that. Hopefully I can install in properly so I can monitor my rpms during my commutes ...
Continuing from Dave's method with a cheap one, a 20" diameter wheel would give a virtually correct reading, so fine tuning for that or another wheel size by using the computer's wheel size setting in millimetres may cancel the need for maths.
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It makes no difference, Dave's maths is to cancel the internal maths of the computer, dividing by the circumference cancels the internal wheel setting and the times 60 turns the hours of mph into minutes for rpm.
The 20" wheel computer setting is 62.8" circumference, then divided by 60 = 1.047
That gives an rpm reading just 4.5% high.
If you use the millimetre wheel size setting in the computer instead of 20", you can fine tune out that 4.5%
A setting of 1524 mm will give perfect accuracy, so get as close to that as the computer permits, maybe 1525 mm is a setting step.
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The 20" wheel computer setting is 62.8" circumference, then divided by 60 = 1.047
That gives an rpm reading just 4.5% high.
If you use the millimetre wheel size setting in the computer instead of 20", you can fine tune out that 4.5%
A setting of 1524 mm will give perfect accuracy, so get as close to that as the computer permits, maybe 1525 mm is a setting step.
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Thats interesting.. If this two speed are the max torque and max efficiency will be great!
As you can see in stoke monkey official website this is the "sweet" zone , where you want to operate you motor ( the curves for tonxgin may be little different but the concept is the same)
Clever Cycles » Blog Archive » Motors and bicycles
i will contact tongxing to see how the controller can work.
i think the best way will be a pedelec sensor combine with a throttle that remain in the position you set it. That combine with a rpm computer (as you are planing) so you can tune it.
On the other hand if you set correctly your sprocket / chainring so your usual cadence meets the RPM of the motor on the sweet zone, you haven't got to control to much your throtle, isn`t it?
Yes. Thats what I think I'm doing. WHen I fit my cadence computer I hope I can confirm this! ..
Ok. I have installed my cateye and programmed my computer with TWO circumferences. One that Flecc suggested (1524) and one suggest (1670) at the following link:
63xc.com--How To | Cadence
The results with the rear wheel raised in the kitchen:
Cirumference, Slow Speed, High Speed
1670, 175, 212
1524, 160, 192
As my motor is rated at 175 rpm guess the top figures are correct.
Having some teething trouble. My "cadence" computer is wireless and was not positioned correctly or securely! ...will sort it out in time for the return trip. Here are my photos:
This is much better:
I found having a rpm computer most useful. It confirmed what I had hoped. It also helps to focus and hit the "sweet spot" . During the ride home it seemed I was mainly in the range 160 - 190 rpm. As my gear ratio is 1:2 then that equates to cadence of between 80 - 95. At the end of my ride (which was only 8 miles due to my main chain snapping) my average rpms was 160 and my max rpms 267 which I find a little surprising as the highest I noticed while riding was about 210 rpms ... I may need to get the camera on the computer and get the evidence ...
D
Deleted member 4366
Guest
You could get a very accurate measurement of your cadence from the camera. All you need to do is count how many times your foot goes round every minute. That's much easier to do after the event from a video than iy it is while riding. Sometimes I measure my cadence from my bike computer clock while I'm pedalling at a steady rate. As soon as the minute changes, I count until it changes again. It's nearly always 70 +/- 2.
Nice set up! Regarding your max rpm, could it be that during a short acceleration you get a "peak" value for rpm which is giving an unreal value for rpm? I am guessing...
I have talking with tongxin sells and they told me you can get a pedal sensor + throttle or pedal sensor + display with buttons.
With the throttle there is an "auto" function available so after 8 seconds enters in autopilot and you don have to hang the throttle anymore.
The display with buttons shows the battery status and you can set the speed to 6 different positions.
I think the display is the better option. ( Also with brake sensor to stop the motor if you are braking)
Pd. I am getting used to pedal with the recumbent , at first my legs "hurt" when I climbed.. but everyday is better, i am improving...
The 1524 circumference setting I calculated should be correct and the 175 rpm nominal of the motor falls almost exactly centre of the 160, 192 you showed for that setting. The 1670 you adopted is possibly the reason for your high reading, since it's way above what calculation indicates is necessary.
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