How did you get 1524 flecc? Is this speed formula not applicable: (circ x rpm x 60)/100,000 = kph
"stokemonkey" my Tongxin?
- Thread starter kitchenman
- Start date
From my original post:
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.
You can see that if the 20" is converted to millimetres ( x 25.4) it's just over 1595. So I just took the 4.5% excess from that to get the 1524.
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.
You can see that if the 20" is converted to millimetres ( x 25.4) it's just over 1595. So I just took the 4.5% excess from that to get the 1524.
So. In my "maths" brain I have now installed the following:
Formula is: CIRC/60 = RPM where CIRC is in inches
Top get RPM =1 we need CIRC = 60 inches which when converted to mm is (60 * 25.4) = 1524 mm
Ok. I took the advise of d8aveh and put a bright yellow spot on the hub, shot a min or so of footage and played it back in slow motion I used slow speed mode and counted 170 ... Doing the high speed test next ..
High speed = 202 ..
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What?Dead in the middle of your two previous figures, there's diplomacy for you!
lol ... your going to have to formulate that mathematical analysis for me (again! ) ... I'd say its nearly in the middle. ... or is it malcolm in the middle! ... (looking round for the lunchtime sherry so you'd better be quick cause in about 2 mins this is all going to get even more hazy) ...
All very well maintaining. Wheres your evidence? .. Here's mine:
TONGXIN RPM TESTING - YouTube
Notice the chain movement? ... Thats probably not a good thing .. Umm.. .
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My evidence is only in the maths balance, equalising the sides of the equation to reach one to one readout from the pulses. If the cycle computer is doing it's job, that 1524 setting should give an accurate count of revs per minute. Any other setting will give either higher or lower readings than the actual revs per minute.
It wouldn't surprise me if the computer readout isn't accurate, I notice 10mph uses a mechanical counter for his marathon course ride distance checking to ensure absolute accuracy, rather than trusting to electronics.
It wouldn't surprise me if the computer readout isn't accurate, I notice 10mph uses a mechanical counter for his marathon course ride distance checking to ensure absolute accuracy, rather than trusting to electronics.
D
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Alan, I take my hat off to you sir. That motor arrangement is brilliant. i never thought it would come out so good,
I think that must be it. Would be interesting to try different computers and see how they vary ..including a pure cadence computer .. anyway, based on my video results I have now entered 1621 which I think is probably giving me a more accurate reading. This mornings average was 160 rpm with a max of 233 rpm ..
Thanks Dave. I am really pleased with the results I am getting and there are still things that need refining so there is always something to think about.. No freewheel, no brake sensor! , battery housing could be better not to mention messing about with fairings, canopies and cameras ....
Steele, I would recommend getting a cadence computer. This will really help you with your hill climbing. With correct gear changing and the right cadence (for you) your legs should not hurt at all. I am "born again" having fitted my cadence computer. If I want my legs to hurt then I can simply change gear now. i.e I am in control of the bike. Its not in control of me! ...
Also, Do you have a head rest on your seat? If not, I would recommend getting one. If you find yourself having to push the bike for any reason it really is very useful. The balance of the bike is such that you can do this:
http://youtu.be/6I7QHWi1J3E
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Based on the videos I worked out that I would need to enter 1621 as the circumference which is what I have been using for the last few rides. However, I realised that I had not checked this by raising the back wheel. I've just done that and 1621 produced a result of 161 and 194. Through trial and error I have now set the circumference to 1730 which is giving me a result of 170 and 205 which is pretty close to my video rpms. ...
Thanks Alan for you suggestions,
In fact I have a head rest, and besides supporting my head it help me to realize when I am not relax on the bike , because when I am "stress" my head is not on the head rest.
Regarding the cadence, I am improving I realized that I was using the smaller sprockets than I think base on the position on the bar end shifter. I thought I was on bigger sprockets that really was. Now I just try to spin fast and don't look at the sprocket.
In fact I have a head rest, and besides supporting my head it help me to realize when I am not relax on the bike , because when I am "stress" my head is not on the head rest.
Regarding the cadence, I am improving I realized that I was using the smaller sprockets than I think base on the position on the bar end shifter. I thought I was on bigger sprockets that really was. Now I just try to spin fast and don't look at the sprocket.
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Hi Steele, I have just checked my "stokemonkey" sprockets again and I have 16t on the motor and 38t on the front chainring. I may have told you different before! ...
One simple way to have some idea of the accuracy of your cadence readings would be to cycle at a cadence of one revolution per second (or turn the cranks once per second with the rear wheel off the ground) and see if that works out that your pedals are doing 60rpm. If you turned the crank by hand whilst watching a stopwatch to give you an idea of how fast one turn per second is perhaps? Interesting to read of your adventures Alan. By the way the cramp you mentioned on your other thread is due to the alcohol!
Thanks for the tip and reminding me of my alcoholism! .. (not really!).. and sorry to any alcoholics who may read this...)
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