Agattu gears, and where do I connect an ammeter?

[10mph]

I measured the gears on my 3 speed Kalkhoff Agattu today:
1st gear 45 inches
2nd gear 60 inches
3rd gear 80 inches
(All are distance moved forward for 2 radians revolution of the pedals, ie for 1 pedal rev divided by pi)

Then in order to check the sprocket sizes I took the plastic chain cover off: one bolt on the inside at the back, then the cover eases forward off two clips at the front.
This is a view of the chain side with the chain guard removed. Note my Panasonic drive was made 17 Dec 2010.

Using the sprockets sizes marked on the picture and the rear wheel circumference I worked out the rear hub ratio to be:
1st gear - 0.79
2nd gear - 1.04
3rd gear - 1.38
From what I have previously read about the Inter 3 hub the second gear should be direct 1:1 drive so my measurements agree with this within 4%.

I am very happy with these gears for my normal biking at 10 mph, but if ever I wanted to clip along a bit faster as I needed to last Monday night when keeping up with two push bike riders travelling at over 15 mph, I suppose the best thing would be to reduce the rear sprocket from 16 to say 14.

While I was inspecting the crank area I noticed a mysterious hole marked in the upper right of the picture, with connectors behind a flexible plastic sheet. Below is a close up picture, where you just make out an empty 4 pin female connector. I could also make out a 3 pin connector also not plugged in and the back of a third connector.

What are these connectors lurking under the plastic which obviously keeps the water out? Can I use them to gain access to what the electronics is doing?
I want to find out how I can fit an ammeter shunt to measure battery current. I don't suppose there could be a built in shunt and all I have to do is to connect plug in to the right connector, and then reseal the hole against water ingress?
I have not taken the plastic covers off the other side yet to see if a shunt could be installed there at the battery socket.
How do people fit ammeters to Kalkhoff's implementation of the Panasonic motor system?

 

[tillson]

I am very happy with these gears for my normal biking at 10 mph, but if ever I wanted to clip along a bit faster as I needed to last Monday night when keeping up with two push bike riders travelling at over 15 mph, I suppose the best thing would be to reduce the rear sprocket from 16 to say 14.

I may be wrong, but I was under the impression that 16 tooth was the smallest available. You may have top increase the chain wheel size to achieve the desired higher gearing.

 

[iaing]

You can get a rear sprocket with any number of teeth - 11 in my case. There are many threads on the site giving details, here is one: http://www.pedelecs.co.uk/forum/electric-bicycles/6076-agattu-11-tooth-sprocket.html?highlight=KALKHOFF+SPROCKET

As regards the ammeter bit, not a clue.

Iain

 

[tillson]

You can get a rear sprocket with any number of teeth - 11 in my case. There are many threads on the site giving details, here is one: http://www.pedelecs.co.uk/forum/electric-bicycles/6076-agattu-11-tooth-sprocket.html?highlight=KALKHOFF+SPROCKET

As regards the ammeter bit, not a clue.

Iain

Your link refers to motor sprockets, not rear wheel sprockets. I'm fairly sure that rear sprockets don't come smaller than 16 tooth.

 

[tangent]

You can get smaller sprockets than 16T, but not dished ones. It may be possible to fit non-dished sprocket to a 3 speed hub. I tried fitting a 15T non-dished sprocket to a Nexus-8 hub and found that the chain rubbed against the hub. You may get away with this on the smaller 3 speed hub though.

Alternatively, replace the chainwheel with a 41T one. These are available from 50 Cycles.

 

[tangent]

Regarding fitting an ammeter, one method is to gain access to the wires leading from the battery mount contacts and the circuit board. You may be lucky and find that there are spade terminals or similar that you can unplug and route through your own power meter. On my Lafree I had to cut the wires. I then soldered 3.5mm bullet connectors to these wires so that I could route the current and provide power from external batteries.

As your bike is new I would consider very carefully before cutting any wires though as this may invalidate your guarantee.

 

[Biged]

Change your chainring for the 41T, thats what i did on my Agattu. You lose a bit of range because your assistance continues to a bit higher level but thats the only drawback.
I had mine changed by 50cycles before i took delivery, it was their mechanics suggestion when i said i would like a lower cadence at higher speed. Its a standard part 41-tooth Front Chain Ring

 

[flecc]

Yes, you change the chainring to 41 tooth to be able to go faster with your own effort, change the motor sprocket from 9 to 11 tooth for the motor to drive it faster, or change both to enable all-round faster performance.

Changing the motor sprocket will reduce the range of course, due to the motor driving at higher speeds as well.

The additional connections are sometimes* one, for the optional "walk-alongside" thumb throttle which only operates up to 6 kph, and two, for the simulated low voltage lighting. This latter can only be used with 6 volt tungsten filamnt bulbs, not LEDs under any circumstances.

* I can't guarantee these are your connections since the models change. The "walk" throttle connection will definitely be there, but the other may not necessarily be lighting.
.

 

[iaing]

Your link refers to motor sprockets, not rear wheel sprockets. I'm fairly sure that rear sprockets don't come smaller than 16 tooth.

Whoops! You are absolutely right. Have checked my post (and older ones) as well as the bike and it is an 18 tooth rear sprocket I fitted. Can't think where I got the 11 tooth idea from.

Iain

 

[JamesC]

I measured the gears on my 3 speed Kalkhoff Agattu today:
1st gear 45 inches
2nd gear 60 inches
3rd gear 80 inches
(All are distance moved forward for 2 radians revolution of the pedals, ie for 1 pedal rev divided by pi)

Then in order to check the sprocket sizes I took the plastic chain cover off: one bolt on the inside at the back, then the cover eases forward off two clips at the front.
This is a view of the chain side with the chain guard removed. Note my Panasonic drive was made 17 Dec 2010.
View attachment 1980
Using the sprockets sizes marked on the picture and the rear wheel circumference I worked out the rear hub ratio to be:
1st gear - 0.79
2nd gear - 1.04
3rd gear - 1.38
From what I have previously read about the Inter 3 hub the second gear should be direct 1:1 drive so my measurements agree with this within 4%.

I am very happy with these gears for my normal biking at 10 mph, but if ever I wanted to clip along a bit faster as I needed to last Monday night when keeping up with two push bike riders travelling at over 15 mph, I suppose the best thing would be to reduce the rear sprocket from 16 to say 14.

Hi 10mph
Thanks for your interesting writeup on measuring the London marathon.

Apologies if the following overlaps with your research on the Kalkhoff Agattu C3, but it may be useful. Much has been written here since the Kalkhoff ebikes were launched 3 or 4 years ago, and much of the information is set out clearly on Flecc’s website.

However, the early bikes with Nexus hub gears were supplied either with the Shimano 7-speed hub & 22T sprocket (Agattu) or the Shimano 8-speed hub & 23T (ProConnect), both using the 41Tooth Panasonic chainwheel.

Very little has been written about the Nexus 3 speed hub which has only appeared recently on the Agattu ebike. I am assuming that the hub is the Shimano SG-3R40 (Parts List here) with a shield over the splines in place of the optional roller brake.

Nexus hub gears, including the 3 speed, are normally fitted with Shimano dished sprockets; the following teeth are available 23, 22, 21, 20, 19, 18, 16 and the part numbers for each of them are shown under item 26 on the parts list.

I have always found Petra Cycles to be good for Shimano parts in general; 50cycles will have the Shimano parts most commonly used on the ebikes.
Petra links for SG-3R40 Nexus Inter-3 hub / Revo shifter (doublecheck what is fitted) and Nexus sprockets.


The Panasonic chainwheels are unique Panasonic parts and available only from 50cycles or other ebike suppliers such as Onbike or TriSportingGolla in Germany.

AFAIK only the 41T and 35T chainwheels are available, but they cover your needs very well.


The late Sheldon Brown’s website is an excellent source of data for hub gears (your 3 speed hub is discussed here), and the Hub Gear Calculator makes it easy to compare various setups.

I use 41T front chainwheel and 19T rear sprocket with the Shimano 8 speed hub on my Agattu with 700x38 tyres defining the wheel size. (41/19 and 35/16 being almost identical ratios)

I agree that your best options on the 3 speed look like 35/16 for measuring hilly courses or 41/16 for the flatter courses.

SB gear calculator gives the following gear inches:

............8 speed..........3 speed............3 speed
.............41/19.............35/16...............41/16

1............31.1
2............38.0
3............44.1...............43.8
4............50.2......................................51.3
5............59.0...............59.8
6............72.1......................................70.0
7............83.7...............81.5
8............95.2......................................95.5

Quite likely that you will need a longer chain (+ 3 links) to fit the 41T chainwheel, and you will need to doublecheck that the bigger chainwheel fits under the latest chainguard.

I have tried a larger motor sprocket, but have come to enjoy the low cadence of the standard 9T (I am 61 and like to be able to ride up all hills when away from the flat country around Peterborough). The Panasonic drive takes much of the pressure away from the knees, so a low cadence is not inflicting much damage.

Your picture of the Panasonic drive on the C3 Agattu highlights the new chain tensioner / wrapper using 2 jockey wheels – 1 fixed and 1 spring loaded. The version on the earlier bikes just has the single spring loaded wheel.

It may be possible to store sufficient slack with your arrangement to handle either the 35T or the 41T chainwheel ??

James

 

[10mph]

JamesC: Many thanks for your very clear information. Your table of ratios shows very well the different ratios of the 3 gear and 8 gear models, and as you say the 41T chain wheel is the way for me to go to get a 17% speed increase for work above 10 mph on a flattish measurement job. That would have been useful last Monday night and also if I ever have to chase these fit younger riders again!

There does seem room under the chain guard to take the 41T chain wheel. I have just had a look and the gap at the point I can easily see is 22mm, the radius of the chain on the 35T sprocket looks to be just under 70mm.

I suppose I could buy a longer chain if it does not fit and fiddling with the links is too messy.

I think I will get the 41T and practice changing chain wheels, but there is no great hurry for this. My next measurement later this week is a very short loop in North Wales - I dont really need to take the pedelec rather than the push bike for that, but the organiser has threatened to get me to measure while I am there a longer trail on Anglesey in the Newborough Forest. At least I am not going to be asked to measure the mountain race on Snowdon.

Just to confirm: the part number of the Shimano rear hub on my Agattu is SG - 3R40, and yes, I have Flecc's excellent web pages carefully bookmarKed and refer to them frequently.