RTIII
1 kW
Hello All,
I've got a 48V, 500W Tongsheng TSDZ2 on the way and am preparing for the conversion. One issue that's come to mind is the gearing. I am using this bike for primary transportation and love the gearing now, though it has a lot of overlap in the gears - generally a good thing, but it has 10 speeds in total and the overlap of the two chainrings is considerable. ... The issue has to do with the fact that the TSDZ2 comes with a 42T attached to the crankset and I'll lose my 52T that's attached to my old crankset and I have to do something about it.
The bike is a Raleigh with 27" tires. Original gearing is: T52 main chainring and a 40 added, with the following cassette EDIT: OK, it's NOT a cassette, it's a freewheel! THANKS GANG, for informing me! ... To wit:
1: 28
2: 24
3: 20
4: 17
5: 14
I understand from reading up that the smallest here, at 14 teeth, is actually pretty good in the sense that 11 is a bare minimum (I have read), and more teeth help with regard to converting to electric because there's less stress per tooth - not that my 500W system is all that powerful. However, there is some room to go smaller if desired.
We know from experience (you can read on the main TSDZ2 thread here on this site) that the TSDZ2, without over-volting, gives a typical upper-end cadence of 90 Pedal-RPM, give or take a little. Some complain that they like a faster pedal-RPM but the TSDZ2 drops out assisting above around 90, so they have to get a lower voltage unit and over-volt it because the highest voltage unit they sell, 48v, has a built-in cut-off preventing over-volting by much - a 52V (nominal) pack is known to not work when fully charged!
I personally am not concerned about going over 90 PRPM. However, I used this data to calculate my speeds at 90 PRPM and came up with this table (if you think this table may be flawed, DO PLEASE point it out to me! I've never calculated bicycle speeds before, so maybe I factored in the gearing incorrectly - but it looks reasonable to me). To wit:
Speed Table, in MPH, Target Pedal RPM: 90 (the dots are to keep table alignment)
gear:..1....2.....3....4.....5
52T: 13.4 15.7 18.8 22.1 26.9
40T: 10.3 12.0 14.5 17.0 20.7
42T: 10.8 12.7 15.2 17.9 21.7
I see two things of import in that data:
1) The 40T and 42T are so close that I can consider the 42T an effective replacement for it. And;
2) Clearly, my top speed with assist will be limited to 21.7 unless I do something about it.
It appears from the images on the official web site that the 42T that comes with the TSDZ2 can have a second chainring mounted to it. Perhaps my solution is just to get a 52T that can be added to the 42T. Or, if it's easily done and not too expensive, a slightly taller gear might be a good choice - we can do 28 MPH legally on the streets here, so a little taller might be a good thing.
Optionally, I could change out the cassette...
I've never done either! A few questions:
1) Am I headed on the right track with the chainring idea, going to a 52T or taller?
2) Are cassettes a mix-and-match affair? That is, I can get ONE gear and swap it around maybe?
... And please point out anything else a newbie like me might need to know!
TIA,
RTIII
I've got a 48V, 500W Tongsheng TSDZ2 on the way and am preparing for the conversion. One issue that's come to mind is the gearing. I am using this bike for primary transportation and love the gearing now, though it has a lot of overlap in the gears - generally a good thing, but it has 10 speeds in total and the overlap of the two chainrings is considerable. ... The issue has to do with the fact that the TSDZ2 comes with a 42T attached to the crankset and I'll lose my 52T that's attached to my old crankset and I have to do something about it.
The bike is a Raleigh with 27" tires. Original gearing is: T52 main chainring and a 40 added, with the following cassette EDIT: OK, it's NOT a cassette, it's a freewheel! THANKS GANG, for informing me! ... To wit:
1: 28
2: 24
3: 20
4: 17
5: 14
I understand from reading up that the smallest here, at 14 teeth, is actually pretty good in the sense that 11 is a bare minimum (I have read), and more teeth help with regard to converting to electric because there's less stress per tooth - not that my 500W system is all that powerful. However, there is some room to go smaller if desired.
We know from experience (you can read on the main TSDZ2 thread here on this site) that the TSDZ2, without over-volting, gives a typical upper-end cadence of 90 Pedal-RPM, give or take a little. Some complain that they like a faster pedal-RPM but the TSDZ2 drops out assisting above around 90, so they have to get a lower voltage unit and over-volt it because the highest voltage unit they sell, 48v, has a built-in cut-off preventing over-volting by much - a 52V (nominal) pack is known to not work when fully charged!
I personally am not concerned about going over 90 PRPM. However, I used this data to calculate my speeds at 90 PRPM and came up with this table (if you think this table may be flawed, DO PLEASE point it out to me! I've never calculated bicycle speeds before, so maybe I factored in the gearing incorrectly - but it looks reasonable to me). To wit:
Speed Table, in MPH, Target Pedal RPM: 90 (the dots are to keep table alignment)
gear:..1....2.....3....4.....5
52T: 13.4 15.7 18.8 22.1 26.9
40T: 10.3 12.0 14.5 17.0 20.7
42T: 10.8 12.7 15.2 17.9 21.7
I see two things of import in that data:
1) The 40T and 42T are so close that I can consider the 42T an effective replacement for it. And;
2) Clearly, my top speed with assist will be limited to 21.7 unless I do something about it.
It appears from the images on the official web site that the 42T that comes with the TSDZ2 can have a second chainring mounted to it. Perhaps my solution is just to get a 52T that can be added to the 42T. Or, if it's easily done and not too expensive, a slightly taller gear might be a good choice - we can do 28 MPH legally on the streets here, so a little taller might be a good thing.
Optionally, I could change out the cassette...
I've never done either! A few questions:
1) Am I headed on the right track with the chainring idea, going to a 52T or taller?
2) Are cassettes a mix-and-match affair? That is, I can get ONE gear and swap it around maybe?
... And please point out anything else a newbie like me might need to know!
TIA,
RTIII