Cadence and finding the 'sweet spot'

[Mussels]

Hi poppy: Try this link CYCLING PERFORMANCE TIPS - foot syndromes

That's a good site, if I read it right then I should be on a high carb diet. I can live with that.

 

[Danny-K]

Just curious, but if we could alter the size of the front chain wheel, wouldnt that have an effect on the cadence that the motor wheel sees?

John

Nope, the motor will see the same cadence whatever the size of the chainwheel/ring. If you have access to a bike fitted with a triple chainset, stick a small piece of sellotape on one of the teeth on the outer largest chainring and likewise in the same exact position way down on the tiny inner chainring. Now rotate the cranks backwards and watch both pieces of sellotape - both arrive 360 degrees later at the same exact location at the exact same time - it's impossible for them not too.

What I think you are thinking off, is the reduced wattage needed by the rider to turn the cranks if that rider fits a smaller chainwheel, and conversely a greater amount of wattage if a larger chainwheel is fitted, (assuming the same velocity is required from the same rider on the various sized chainrings).

 

[Blew it]

Danny

Have a think about what your saying above.

A few thoughts of my own.

The only speed that the motor "sees" is the road speed. Neither it or the wheel into which it is laced has any idea of the speed of the crank axle up front. Except of course the signal from the pedelec sensor on the crank axle.

The speed of the crank axle in relation to the road speed (cadence) is entirely governed by the diameter of the chainwheel.

Heh! your certainly getting your monies worth out of that Salisbury. Can't be bad!

All the best

Bob

 

[flecc]

Just curious, but if we could alter the size of the front chain wheel, wouldnt that have an effect on the cadence that the motor wheel sees?

John

Nope, the motor will see the same cadence whatever the size of the chainwheel/ring.

Sorry Danny, that's normally correct, but not on the Panasonic unit in question. That unit measures the rotation of the motor chain drive sprocket and therefore the chain speed to determine the chainwheel cadence. A smaller chainwheel would mean a higher cadence for a given chain speed.

Academic though, since the chainpath and relationship with the small 9 tooth motor sprocket makes the chainwheel size critical, and it's a very non-standard chainwheel anyway.

There is another way to increase the cadence on these units, using a larger motor chain drive sprocket and correspondingly increasing the rear hub sprocket. Using an 11 tooth motor sprocket would increase the maximum power roll off point cadence from 40 to 49 for example.
.

 

[JohnInStockie]

hmmm, so increase the size of the motor sprocket to 11 teeth, and drop the rear to say 16 teeth. That would increase the cadence at which most assistance would be provided, and I assume that the ratio of 9:11 vs 23:16 (or 18:16) needs to be very similarly compensating....

I suppose that this would take a while to get used to, and would adversely effect battery range too, but it would be an interesting experiment...

John

 

[Danny-K]

...Except of course the signal from the pedelec sensor on the crank axle... The speed of the crank axle in relation to the road speed (cadence) is entirely governed by the diameter of the chainwheel.
...Heh! your certainly getting your monies worth out of that Salisbury.

Yes, that's as I understand it. So increasing or reducing your cadence whatever the chainwheel fitted is what governs the motor's performance - yes?

If you change the chainwheel to a smaller one, it's hoped you would either improve or maintain your cadence where previously the rider had failed to do so on a serious hill climb and thus climb it more easily now.

- The Panasonic motor as Flecc points out is a different kettle of fish.

'Monies worth out of the Salisbury'? Well yes, after tonight's quick outing, (just got back in), I'm finding the Salisbury is getting faster and faster, it feels like it's doing it all on it's own. Had a funny moment on the return trip though - with 2 lights out of 3 still healthily showing the motor went into shut-down similar to when it's on it's last legs of discharge. All of a sudden the slope I was pedalling up became very heavy and slow. Stayed like that all the way to the top - with two lights still fully glowing!!!. Crested the top and the third light flickered back on and full power was returned.

Frightened the life out of me. I assume it was having a 'software moment'. New batteries/chargers and motors flashed through my mind for a couple of moments - somebody tell me they do that sometimes.

 

[flecc]

hmmm, so increase the size of the motor sprocket to 11 teeth, and drop the rear to say 16 teeth. That would increase the cadence at which most assistance would be provided, and I assume that the ratio of 9:11 vs 23:16 (or 18:16) needs to be very similarly compensating....

I suppose that this would take a while to get used to, and would adversely effect battery range too, but it would be an interesting experiment...

John

I accidentally misled you John, typing reducing the rear sprocket when it should have been increasing. The enlarged motor sprocket would need an enlarged rear sprocket to retain the same motor drive road speed relationship. The enlarged rear sprocket would increase the cadence in relation to road speed as well of course.
.

 

[flecc]

Frightened the life out of me. I assume it was having a 'software moment'. New batteries/chargers and motors flashed through my mind for a couple of moments - somebody tell me they do that sometimes.

This is sometimes due to a loss of efficient electrical contact at the junction of battery and bike, but another common cause is cell tiring. Lithium cells can suffer chemical exhaustion when in sustained high discharge conditions, simply unable to keep up sufficient current delivery, The moment the load is reduced or removed, the cell recovers, signalled by the meter lights returning.
.

 

[Danny-K]

This is sometimes due to a loss of efficient electrical contact at the junction of battery and bike, but another common cause is cell tiring. Lithium cells can suffer chemical exhaustion when in sustained high discharge conditions, simply unable to keep up sufficient current delivery, The moment the load is reduced or removed, the cell recovers, signalled by the meter lights returning.
.

Thanks for the info Flecc. I've noticed the occasional rattle from the battery in it's bike housing compartment; intend trimming the edge with some kind of rubber tubing to tighter fit the battery, (car door rubbers etc.,) maybe if bumpy enough ride, it can lose full contact with the connections. Then again I was enjoying myself so much tonight at traffic light crossings I was whacking the throttle wide open to get a sharp take-off in between light changes ahead of the traffic, so possibly cell exhaustion too.

 

[JamesC]

Sorry Danny, that's normally correct, but not on the Panasonic unit in question. That unit measures the rotation of the motor chain drive sprocket and therefore the chain speed to determine the chainwheel cadence. A smaller chainwheel would mean a higher cadence for a given chain speed.

Academic though, since the chainpath and relationship with the small 9 tooth motor sprocket makes the chainwheel size critical, and it's a very non-standard chainwheel anyway.

There is another way to increase the cadence on these units, using a larger motor chain drive sprocket and correspondingly increasing the rear hub sprocket. Using an 11 tooth motor sprocket would increase the maximum power roll off point cadence from 40 to 49 for example.
.

Flecc
I am grappling with why the change from a 9 to 11 tooth motor sprocket needs to be accompanied by an increase in the rear hub sprocket.

Don't you get the same effect by selecting one gear lower, and allowing the new motor assist speed to lift the rider's input to the higher cadence, which restores the original road speed.

James

 

[flecc]

Flecc
I am grappling with why the change from a 9 to 11 tooth motor sprocket needs to be accompanied by an increase in the rear hub sprocket.

Don't you get the same effect by selecting one gear lower, and allowing the new motor assist speed to lift the rider's input to the higher cadence, which restores the original road speed.

James

Yes of course James. I was only stressing the need to correctly change the rear sprocket to retain all former relationships except the chainwheel cadence increase.

Most would prefer to do as you say for the extra speed, though that does mean the cadence in relation to road speed when in top gear hasn't been changed.
.

 

[Blew it]

Danny

Sounds like the Salisbury had a little "hissy fit". Like the man said, "Lithium batteries are very obedient, they will quite happily bring about their own destruction in trying to please their masters".

Hope your not working tomorrow, there's a weather slot in the afternoon in the West, I'm taking the newly aquired Mistral out for a spin.

By the way, I was spotted riding home the other day with straw sticking out of my tyres like an electrified Wurzel Gummidge, My street cred's gone right down the tubes, and it's all your fault!!!

All the best

Bob

 

[Danny-K]

Sounds like the Salisbury had a little "hissy fit". Like the man said, "Lithium batteries are very obedient, they will quite happily bring about their own destruction in trying to please their masters".

Hope your not working tomorrow, there's a weather slot in the afternoon in the West, I'm taking the newly aquired Mistral out for a spin.

By the way, I was spotted riding home the other day with straw sticking out of my tyres like an electrified Wurzel Gummidge, My street cred's gone right down the tubes, and it's all your fault!!!

All the best

Bob

"By the way, I was spotted riding home the other day with straw sticking out of my tyres like an electrified Wurzel Gummidge, My street cred's gone right down the tubes, and it's all your fault!!!"

LOL! Laughed like a drain when I read that!

- Don't tell me you've had yet ANOTHER puncture? (Hope you were just joking.)

Nope working tomorrow - it's Friday I want well-behaved weather for, and it looks likely. I'm off out on business on a 32 mile round trip and I want to test out the Salisbury on it. I 'only' get 27 miles to the gallon/charge so will be turning off power on the easy bits going there to see if I can manage the whole lot with minimum energy. I've cycled that trip by pushbike many a time, but an e-bike with dead battery, and no ultra low gear fitted - yet, (planned for near future), is another matter.

P.S. Been reading up on the Mistral - sounds quite impressive, (although if one has to have a hub motor I'm a rear-hub-motor-only man). Hope you can post a review of how you find it.

 

[Blew it]

No worries, it's rear hub motored. More later.

G'nite

Bob

 

[Rod Tibbs]

Hi there. I have now had my Mistral for around four months and I am absolutely delighted with it. It is about the cheapest 36 volt bike on the market and once you have written off the joke dynamo as useless, you begin to realise what damn good value it is.

There are two Pedelec settings and a throttle override which I regard as a 'must have.' In this area we have some long flattish straight country roads and bowling along on those with throttle only is a great pleasure. I read all the glowing stuff about Agattus and the rest but until they get round to offering a throttle setting (OK I know about the regs on the continent etc) then I am afraid they are not for me.

I am getting around 20 miles to a charge, although I have never pushed it to its limit, and I tend to use Pedelec only on hills and switch to some throttle maybe downhill and then on the flat.

I also find the rear carrier very useful and use two panniers in which I keep puncture repair kit, some simple tools, bottle of water and a folding umbrella under which I can hide if struck by a sudden and total deluge.

The six gears seemed limiting at first because my old bike had 24 but in reality the lowest gear gets me up hills quite happily and the top gear enables me to knock along around 20 ish.

Look forward to hearing more of your experiences.

Rod