A Busetti On Ebay 60 Mile Range

[flecc]

I can see that, though like i said it was a front sprocket (chainring?) that was changed, i think the original was 37T changed to 41T, does that sound right?

This is perhaps a misunderstanding, the chainring hasn't been changed since there are no alternative ones.

The older Panasonic power unit that was discontinued in 2006 and used only on Panasonic, Giant Lafree and Flyer bikes used a 37 tooth chainwheel. The newer Panasonic unit that you have is always fitted with a 41 tooth chainwheel. These are not standard bicycle chainwheels, they are spline mounted unique items.

It's the motor's chain drive sprocket that has been changed, from the standard 9 tooth to an 11 tooth one. What that does is increase the cadence (pedal rotations) at cut-off and raise the cut-off road speed by over 22% so increasing consumption substantially, by more than 22% since the effect is not linear. Changing the gear you use will not help.

See my Panasonic Support Site for more information.
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[Biged]

No flecc, no misunderstanding.
I defiantly asked about the possibility of changing the rear sprocket and the mechanic defiantly suggested changing the front chainring instead.
I was not absolutely sure about the number of teeth but fairly sure 37T and 41T were the numbers mentioned, i have never got down and counted the teeth so have no idea what is there, i honestly can't have made these numbers up.
Tomorrow i will get down on my knees and do a bit of counting.
Will get back to you on this one?

 

[stevebills]

No flecc, no misunderstanding.
I defiantly asked about the possibility of changing the rear sprocket and the mechanic defiantly suggested changing the front chainring instead.
I was not absolutely sure about the number of teeth but fairly sure 37T and 41T were the numbers mentioned, i have never got down and counted the teeth so have no idea what is there, i honestly can't have made these numbers up.
Tomorrow i will get down on my knees and do a bit of counting.
Will get back to you on this one?

Most chainrings are stamped with BCD and teeth number

 

[NRG]

As Flecc said the newer Panasonic units have a 41T chainring I counted mine whilst cleaning the chain the other day. They are not your normal front chain ring being spline mounted onto a freewheel.

 

[Teejay]

If you look at the specs of the 2011 Agattu on 50 Cyles' website, it now sports a 35 tooth chainwheel and a 19t rear sprocket on the 8-speed, 16t on the 3-speed.

It isn't clear on the Pro Connect Disc (Alfine) spec sheet, so I rang 'em to ask and, rather to my surprise, I was told they too have the 35/19 set up as standard.

The 'S' models retain the 41t chainwheel, apparently.

 

[flecc]

It isn't clear on the Pro Connect Disc (Alfine) spec sheet, so I rang 'em to ask and, rather to my surprise, I was told they too have the 35/19 set up as standard.

This means they've changed from the 9 tooth motor sprocket to the 8 tooth on bith Agattu and Pro Connect models, which leaves cadence and legal assist speed unchanged from the 41 front, 22/23 rear setup.

The three standard Panasonic sizes are 8, 9 and 11 tooth.
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[tillson]

This means they've changed from the 9 tooth motor sprocket to the 8 tooth on bith Agattu and Pro Connect models, which leaves cadence and legal assist speed unchanged from the 41 front, 22/23 rear setup.

The three standard Panasonic sizes are 8, 9 and 11 tooth.
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Why would they do that? Reduce the size of the chain ring I mean.

I would have thought that a smaller motor sprocket (less teeth) would be more susceptible to wear.

 

[flecc]

Why would they do that? Reduce the size of the chain ring I mean.

I would have thought that a smaller motor sprocket (less teeth) would be more susceptible to wear.

I don't know, but it could be to facilitate a smaller cowling if desired.

Since the 8 tooth has been part of the range available since they introduced the new unit in 2006/7, other bikes have probably had a similar setup.

However, if it's EU/UK legal and using the 35/19 front/rear pair, it has to be the 8 tooth motor sprocket as said, all reduced by about 13.5%. If they've retained the 9 tooth, the final assist cutoff will be increased to 17.6 mph.
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[Cyclezee]

There are at least 2 sizes of chainring fitted by Kalkhoff, what I would call the normal size 41T and a smaller one as fitted to the small frame Agattu which has 26" wheels. I had one in my hands the other day whilst carrying out some maintainance and noticed it was smaller, but I didn't bother to count the teeth.

J hn

 

[Biged]

Right here is what i have.
I have been able to do a direct comparison with my wife's new Dover side by side.
First i did a cadence check in 8th gear.
Put a clamp on the frame in line with the pedal, backed up the wheel until the pedal touched the clamp to take out all slack, marked the wheel level with the chainguard, then keeping resistance on the wheel did a full rotation until the pedal came round to the other side of the clamp, not a full rotation but near enough and still accurate.

Agattu rear wheel rotation 3.25
Dover rear wheel rotation 2.75

Agattu chainring 41T
Dover chainring 35T

Agattu Rear spr 19T
Dover Rear spr 19T

Agattu motor spr 9T
Dover motor spr 9T

So can you tell me what's what?

Oh by the way my wife's Dover has the 28" wheels

 

[flecc]

Assuming the Agattu has 28" wheels which I would expect from your height, one of two things are true:

1) The Dover assists to cut-off by 17.6 mph,

2) or, the Dover unit has a different internal motor speed set electronically to keep the assist maximum down to 15 mph.

If the latter, why they would want to make two versions of the unit to achieve the same thing I've no idea, but I know the units in different e-bike makes do sometimes have circuit board differences.

As the power assist proportion reduces with speed on all units it can be difficult to tell when the cut-off occurs, but you should be able to detect if the Dover assists to a higher speed than the Agattu.
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[NRG]

This is all interesting stuff, I recently fitted the 11tooth motor sprocket to the PCS but assistance still continues to a speed higher than I normally ride at and so has little effect on range... I would like to lower it again but fear the 9tooth would be too low, is there a 10tooth version or would I have to look at changing the rear cassette?

 

[flecc]

I've only ever known Panasonic supply 8, 9 or 11 tooth sprockets for the newer unit.

There is a German language ebay seller offering a range of sprockets for the Panasonic unit in a range of sizes, but I don't have a current link and don't know if a 10 tooth was one of the range.
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[10mph]

I am finding this hard to follow. I perhaps mistakenly thought that the motor speed would be sensed in order to set the ramp down point and maximum speed. If that were true then the relation between the bike speed and the motor speed would be set solely by the motor sprocket, the rear sprocket, the gear ratio in the rear hub gearbox, and the wheel size. Increasing the chain ring from 35 to 41 teeth would then just reduce the cadence by 1-35/41= 15%. The way I read Biged's earlier post, that is what was done-

When i tried out the bike at 50cycles i mentioned the high cadence level in top gear and that i had seen that other riders had changed the rear sprocket to lower this, i asked 'what was their opinion'
Their mechanic said a better option was to change the front sprocket size and that the sprocket size had been reduced in the past, he said it would be a straightforward job to put the 'original' sized sprocket on during assembly at no charge. I agreed and this was done.

For the cutoff speed to be affected by the chain ring size the unit would surely have to sense the pedal rate. I believe there must be a pedal torque sensor so maybe this also provides a pedal rotation speed signal and if that rate signal where used by the controller then the cut off speed settings for the bike would indeed be changed.

Am I missing something?

Are there any circuit diagrams available for the motor and controller? Is it easy to pull the Panasonic unit apart to make one's own diagram and figure out how the controls work? I am not speaking of a just wiring diagram but schematics of the circuit boards etc.

 

[tillson]

For the cutoff speed to be affected by the chain ring size the unit would surely have to sense the pedal rate. I believe there must be a pedal torque sensor so maybe this also provides a pedal rotation speed signal and if that rate signal where used by the controller then the cut off speed settings for the bike would indeed be changed.

Am I missing something?

I don't believe that cut off speed is affected by the chain ring size. My understanding is that the motor sprocket and hence the angular velocity of the motor shaft is what determines the cut off. Increasing the size of the motor sprocket will therefore increase both the cut off speed of the bike and the cut off pedal cadence. The only sensor in the pedal shaft, I believe, is a torque sensor.

 

[flecc]

Yes, as Tillson says, only the motor sprocket and rear sprocket affect the road speed of power phase down and cut-off, the chainwheel only affecting the cadence. The torque sensor on the pedalshaft is just that, no speed sensing.

The old Panasonic unit had it's speed sensed by a Hall sensor on the outer edge of the circuit board reading a ring of magnets on the motor output gearwheel, but the current Panasonic unit appears to read it's rotation speed from the feedback of the motor Hall sensors which are on a sub-board alongside the motor.

There are no circuit diagrams available since the unit is a "repair by replacement" one, no repairs possible and no internal spares available. The circuit cannot be physically "read" since on both old and new units the boards are clear encapsulated and sealed into their crankcase halves, though some deductions are possible.
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[Biged]

Like i originally posted, but i cant seem to grasp with so many conflicting ideas, is that if the rear sprocket (19T) and the motor sprocket (9T) remain the same then the assisted speed is not altered?
If the chain ring size is altered then this only alters the cadence speed? This was what i wanted to obtain i.e. at 15mph cut off, my legs not flying round, but extra unassisted speed available downhill or on the flat if i was capable?
If i am still wrong, please explain it so an idiot can understand it.
The only way i can see any difference is if the speed is picked up from pedal rotation instead of motor speed

 

[tillson]

Like i originally posted, but i cant seem to grasp with so many conflicting ideas, is that if the rear sprocket (19T) and the motor sprocket (9T) remain the same then the assisted speed is not altered?
If the chain ring size is altered then this only alters the cadence speed? This was what i wanted to obtain i.e. at 15mph cut off, my legs not flying round, but extra unassisted speed available downhill or on the flat if i was capable?
If i am still wrong, please explain it so an idiot can understand it.
The only way i can see any difference is if the speed is picked up from pedal rotation instead of motor speed

If the motor sprocket and rear wheel sprocket remain the same, then the road speed at which the motor cuts out will be fixed. Altering the chain ring size will have no affect on motor cut off road speed. As you say, the chain ring just has an influence on pedal cadence alone.

Incidentally, I find a 41 tooth chain ring, 9 tooth motor sprocket and 18 tooth rear sprocket on an Alfine 8 speed a good combination. This does give a motor cut out road speed well above 15 MPH, but it keeps the pedal cadence at a sensible rate. The bike came fitted with 23 tooth rear sprocket originally. I found that I never used a gear lower than 5th and that pedal cadence was ridiculously high.

 

[flecc]

Like i originally posted, but i cant seem to grasp with so many conflicting ideas, is that if the rear sprocket (19T) and the motor sprocket (9T) remain the same then the assisted speed is not altered?
If the chain ring size is altered then this only alters the cadence speed? This was what i wanted to obtain i.e. at 15mph cut off, my legs not flying round, but extra unassisted speed available downhill or on the flat if i was capable?
If i am still wrong, please explain it so an idiot can understand it.
The only way i can see any difference is if the speed is picked up from pedal rotation instead of motor speed

It can be a little difficult to understand with a three way relationship that isn't intuitive. so you are not in any way an idiot.

The first bit you said is correct for the motor drive, the same motor sprocket and rear sprocket will always have the same assisted speed for a given gear and wheel size.

However, since the assist limit is set by the motor and therefore the rotation of the motor sprocket, different size chainwheels will rotate at different speeds. For example, choosing a fictitious number for convenience, if 40 turns of the 9 tooth motor sprocket is the point of 15 mph cutout, that 40 turns onto the chain will turn a 35 tooth chainwheel 10.3 times. (40 x 9 = 360 teeth, which divided by the 35 = 10.3 turns)

For a 41 tooth chainwheel, 40 turns of the 9 tooth motor sprocket will turn the chainwheel 8.8 times. (40 x 9 = 360 teeth, which divided by the 41 = 8.8 chainwheel turns.

Therefore, to get slower pedalling for a given assist speed, you need either a larger chainwheel or a smaller motor sprocket. Many like to do the opposite, get higher pedalling speeds so that the assist phase down does not start at 40 pedal rpm but allows faster pedalling for greater efficiency. To do that they use the 11 tooth motor sprocket which increases pedalling speed by 22%. For those like yourself who like slower pedalling, an 8 tooth motor sprocket with the standard 41 tooth chainwheel helps a bit, slowing the pedalling at any given speed by 11%.

However, the 8 tooth motor sprocket will also slow the assist limit road speed by 11% on your Agattu, so you'd need to reduce the rear sprocket by the same 11%. That 19 tooth would need to be changed to a 17 tooth.

N.B. Crossed with Tillson's post.
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[Biged]

From what i can surmise then is that the Agattu (including mine) was supplied with the 35T x 19T with 9T motor (same as the Dover)
I don't know if tillson has an Agattu but his was supplied with 41T x 23T with 9T motor, which he found too high a cadence. (similar ratio)
Mine now has the 41T x 19T with 9T motor as stated previously, only one tooth difference on rear sprocket from tillson, which we are both happy with.
Incidentally a 41T chain ring is now an accessory at 50cycles.