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E bike recommendation

On road, off road, Mamils, Club rides or just share your routes and tips
scotia
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Re: E bike recommendation

#192341

Postby scotia » January 10th, 2019, 10:52 am

I should stress that my experience (as a 74 year old) in Scotland who wants a foldable e-bike that will be happy with a bit of off-road travel probably does not match the requirements of the original poster - and I think Colin's advice is sound.
Just one question - I have always used rim brakes (as on my current e-bike). From an engineering point of view, the rim seems the most appropriate place to apply the maximum braking force, rather than on a small disc in the wheel centre. Am I missing something? Are disc brakes as effective as rim brakes?

Watis
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Re: E bike recommendation

#192349

Postby Watis » January 10th, 2019, 11:30 am

scotia wrote:I should stress that my experience (as a 74 year old) in Scotland who wants a foldable e-bike that will be happy with a bit of off-road travel probably does not match the requirements of the original poster - and I think Colin's advice is sound.
Just one question - I have always used rim brakes (as on my current e-bike). From an engineering point of view, the rim seems the most appropriate place to apply the maximum braking force, rather than on a small disc in the wheel centre. Am I missing something? Are disc brakes as effective as rim brakes?



IANAE (I am not an engineer) but it seems to me that the larger swept area of a rim brake allows for more braking force for the amount of force applied on the brake lever and also that this allows for finer braking control.

I worked this out for myself when I saw a Buell motorcycle for the first time. These have a large diameter rim mounted disc but the same principles would apply.

Watis

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Re: E bike recommendation

#192445

Postby jofc » January 10th, 2019, 3:51 pm

Just to wade in to several bits of discussion on here:

Quite a few years ago I encountered discussion on best wheel sizes & efficiencies.
My original feeling was that big wheels = more efficient - but apparently its nothing like that.
Bigger wheels = heavier & more angular momentum and e-bikes are supposed to be limited to 15mph
Here is an example of what I mean: https://www.livestrong.com/article/1420 ... s-bicycle/

My conculsion were that wheel sizes were not a massive factor in efficiency.
You need to pick your own balance of wheel size & tyre to suit you.

As for brakes:
I firmly believe that you should be able to do all your own cycle repairs. So I favor rim brakes as they are easy to fix & parts are easy to come by.
Now I know you can also wear the brake pads very easily if you just slam them on & hold them.
The Mrs found out on our first cycle camp/touring trip we did.
She had brakes on all the way down Dover hill, and the next day I had to replace the pads.

I have colleagues who swear by the disk brakes on their mountain bikes, but then end up with their expensive bikes sat in their shed because the oil leaked and they have no idea how to repair it.

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Re: E bike recommendation

#192491

Postby colin » January 10th, 2019, 5:06 pm

Scotia wrote
Just one question - I have always used rim brakes (as on my current e-bike)


Except for my days on a motorbike I have only used rim brakes, on the roads rim brakes are fine but then I use the best quality cantilever brakes which are easy to keep well adjusted as the design allows for spring tension to be adjusted on both arms, V brakes are great but almost too powerful for road use.
I have two bikes an old fashioned touring bike and a 26 inch wheel touring bike with mountain bike gearing and drop handlebars, I use that bike for tracks and good trails but the mud and grit gets ground into the rims and I have had a few rims collapse with wear, if you don't keep removing the tires it can be difficult to guess how much aluminum is left . That is the main argument for using disk brakes which is to preserve rims, on roads it's not such an issue in any case my road wheels are hand built and I specified the toughest touring rims as I ride a lot and value longevity and durability over speed.
V brakes will stop a bike on the steepest of hills but at the expense of putting an awful lot of pressure on the rims, today some rims are available which are supposedly able to withstand the high pressure grinding of V brakes in wet grit and as my 'of road ' bike won't take disk brakes it's those toughened rims that I will get when my current ones wear out.
So the short answer to your question is that disk brakes avoid excessive rim wear, but there are many designs which may bring their own problems ,some are hydraulic using brake fluid to push out pistons , after my experiences with the disk brake on my motorbike I would never put such things on a bicycle, just too much hassle and expense. Cable operated disk brakes should be straightforward to maintain but check reviews to research performance issues.

scotia
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Re: E bike recommendation

#192896

Postby scotia » January 11th, 2019, 9:59 pm

As you will probably have gathered from my previous posts, I am enjoying my outings on the e-bike. Today I tackled a route that climbed 100m over a distance of 1km, with several of the stretches at a significantly higher gradient than the mean - but I managed - just! In the steepest sections I snaked back and forward across the road (a very quiet side road to a radio mast) to reduce the gradient. Until now I wondered why anyone would require the lowest of my 8 gears - now I know why.
Coming down was a bit exciting - and involved a lot of brake application.

staffordian
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Re: E bike recommendation

#192898

Postby staffordian » January 11th, 2019, 10:09 pm

scotia wrote:As you will probably have gathered from my previous posts, I am enjoying my outings on the e-bike. Today I tackled a route that climbed 100m over a distance of 1km, with several of the stretches at a significantly higher gradient than the mean - but I managed - just! In the steepest sections I snaked back and forward across the road (a very quiet side road to a radio mast) to reduce the gradient. Until now I wondered why anyone would require the lowest of my 8 gears - now I know why.
Coming down was a bit exciting - and involved a lot of brake application.

Apologies if you've already mentioned this, but I wondered if when travelling downhill, the E bike has any regenerative capability, to recharge the battery, or do you only have conventional friction braking to slow you down?

scotia
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Re: E bike recommendation

#192905

Postby scotia » January 11th, 2019, 10:43 pm

staffordian wrote: Apologies if you've already mentioned this, but I wondered if when travelling downhill, the E bike has any regenerative capability, to recharge the battery, or do you only have conventional friction braking to slow you down?

No my e-bike has no regenerative capabilities. So I came down the hill with significant pressure on the back (rim) brake, and occasional aid (on the steeper parts) with my front (rim) brake. At 74 I lack the daredevil spirit of my youth when I may have attempted the descent without braking!
Steep hill climbs drain the battery, so regenerative braking would be a desirable (but probably expensive) addition.

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Re: E bike recommendation

#192998

Postby colin » January 12th, 2019, 1:04 pm

Scotia wrote...
So what improvements could I hope for?

A brief look at the specs for your bike shows that it comes with 1.75 inch tires, if you are riding mostly on paved roads then these are too wide, narrower tires give better rolling efficiency with less drag but you need to check that the rims will take narrower tires. my 'off road' bike which I use on the sort of stony tracks you could drive a car on has 1.5 inch tires , my road touring bike has 28mm wide tires, I can ride the 28mm tires on gravel tracks just as easily but they are uncomfortable because there is no dampening of shocks.
A quick look at Halfords web site shows these tires are available in a range of widths for 20 inch wheels

https://www.halfords.com/cycling/bike-p ... ke-tyre-20.

The 1 and 3/8ths would still be good for the sort of tracks I imagine you would ride but be more efficient on paved surfaces.If you ride on roads mostly you might try the 1 1/8th size if they fit your rim width , bear in mind that the narrower over all circumference will alter the gearing meaning more but easier revolutions of the pedals will be required to travel at the same speed. As always make sure you keep tires up to the recommended pressure. I would not change anything else, you have V brakes which will stop you on any descent you might encounter, if you have difficulty keeping brakes properly adjusted then ask at a bike shop if some 'in-line' adjusters would make the task easier. If you have an outside tap then wash the rims regularly.

Happy riding

colin
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Re: E bike recommendation

#193185

Postby colin » January 13th, 2019, 10:37 am

scotia wrote: Today I tackled a route that climbed 100m over a distance of 1km, with several of the stretches at a significantly higher gradient than the mean - but I managed - just! In the steepest sections I snaked back and forward across the road (a very quiet side road to a radio mast) to reduce the gradient. Until now I wondered why anyone would require the lowest of my 8 gears - now I know why.
Coming down was a bit exciting - and involved a lot of brake application.


Actually it sounds like you might benefit from changing the gearing. If when you are cycling as fast as you can on the flat you find yourself to be in 6th gear, (that is you still have 2 harder gears to keep you pedaling when going downhill) then you might sacrifice one of those higher gears for an extra lower gear by changing the front chain wheel for a smaller one with less teeth. Ask at Halfords.

scotia
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Re: E bike recommendation

#193328

Postby scotia » January 13th, 2019, 11:54 pm

colin wrote:Actually it sounds like you might benefit from changing the gearing. If when you are cycling as fast as you can on the flat you find yourself to be in 6th gear, (that is you still have 2 harder gears to keep you pedaling when going downhill) then you might sacrifice one of those higher gears for an extra lower gear by changing the front chain wheel for a smaller one with less teeth. Ask at Halfords.

Thanks for the advice - but I'm (more than) happy with my current top speed!
The reactions of my (adult) children to a septuagenarian out on a bicycle have been somewhat robust. I hate to think what their comments (and possibly actions) would be if I told them I was modifying the bike to go faster. My son has already threatened to remove my pedals.
Back to an earlier point - yes the 1.75 inch tyres are not optimal for on-road cycling, but they are reasonably suited to the modest off-road cycling up farm roads and country tracks which I carry out.

scotia
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Re: E bike recommendation

#193331

Postby scotia » January 14th, 2019, 12:09 am

staffordian wrote:Apologies if you've already mentioned this, but I wondered if when travelling downhill, the E bike has any regenerative capability, to recharge the battery, or do you only have conventional friction braking to slow you down?

As I responded earlier, I don't have regenerative braking, but your query set me looking at the possibility. Several articles on the web suggest it is not really a practical option. The Lithium Ion battery can only accept a modest charge rate without damage, so it would restrict the amount of energy recovered. The best case is coasting on a long down-hill with a modest gradient. On steeper gradients the charge rate would need to be limited - so the energy recovery would be poor. The computed figures, based to a number of different scenarios indicated a 3% to 10% (unlikely) extension of battery life.

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Re: E bike recommendation

#193388

Postby staffordian » January 14th, 2019, 10:57 am

scotia wrote:
staffordian wrote:Apologies if you've already mentioned this, but I wondered if when travelling downhill, the E bike has any regenerative capability, to recharge the battery, or do you only have conventional friction braking to slow you down?

As I responded earlier, I don't have regenerative braking, but your query set me looking at the possibility. Several articles on the web suggest it is not really a practical option. The Lithium Ion battery can only accept a modest charge rate without damage, so it would restrict the amount of energy recovered. The best case is coasting on a long down-hill with a modest gradient. On steeper gradients the charge rate would need to be limited - so the energy recovery would be poor. The computed figures, based to a number of different scenarios indicated a 3% to 10% (unlikely) extension of battery life.

That's interesting, and makes me wonder how EVs overcome this problem. Regenerative braking of a relatively heavy vehicle must surely produce quite concentrated bursts of energy, but presumably there is more scope for better charge regulation in a car, and there are far more cells over which the charge can be distributed.

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Re: E bike recommendation

#193420

Postby colin » January 14th, 2019, 12:21 pm

scotia wrote:
colin wrote:Actually it sounds like you might benefit from changing the gearing. If when you are cycling as fast as you can on the flat you find yourself to be in 6th gear, (that is you still have 2 harder gears to keep you pedaling when going downhill) then you might sacrifice one of those higher gears for an extra lower gear by changing the front chain wheel for a smaller one with less teeth. Ask at Halfords.

Thanks for the advice - but I'm (more than) happy with my current top speed!
The reactions of my (adult) children to a septuagenarian out on a bicycle have been somewhat robust. I hate to think what their comments (and possibly actions) would be if I told them I was modifying the bike to go faster. My son has already threatened to remove my pedals.
Back to an earlier point - yes the 1.75 inch tyres are not optimal for on-road cycling, but they are reasonably suited to the modest off-road cycling up farm roads and country tracks which I carry out.

You misunderstand me Scotia, changing the front chainwheel (if that is possible) for a smaller one with less teeth will lower the entire gearing range , thus making it more efficient for you and the battery when going uphill, your overall top speed on the flat will be slower, not faster.

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Re: E bike recommendation

#193500

Postby UncleEbenezer » January 14th, 2019, 6:22 pm

staffordian wrote:That's interesting, and makes me wonder how EVs overcome this problem. Regenerative braking of a relatively heavy vehicle must surely produce quite concentrated bursts of energy, but presumably there is more scope for better charge regulation in a car, and there are far more cells over which the charge can be distributed.

Gyroscopes have been used for a long time in electric vehicles to recover energy from downhills or controlled braking and use it to climb or accelerate. From distant memory[1], examples ranged from milk floats to passenger vehicles in some less-wasteful countries.

[1] of learning about it in school in the '70s.

scotia
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Re: E bike recommendation

#193501

Postby scotia » January 14th, 2019, 6:25 pm

colin wrote:You misunderstand me Scotia, changing the front chainwheel (if that is possible) for a smaller one with less teeth will lower the entire gearing range , thus making it more efficient for you and the battery when going uphill, your overall top speed on the flat will be slower, not faster.

Yes - you are correct - I'm not at my brightest when responding around midnight!

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Re: E bike recommendation

#193502

Postby scotia » January 14th, 2019, 6:32 pm

UncleEbenezer wrote: Gyroscopes have been used for a long time in electric vehicles to recover energy from downhills or controlled braking and use it to climb or accelerate. From distant memory[1], examples ranged from milk floats to passenger vehicles in some less-wasteful countries.
[1] of learning about it in school in the '70s.

A big flywheel! That should make turning corners interesting :D

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Re: E bike recommendation

#193580

Postby 9873210 » January 15th, 2019, 5:26 am

First and foremost regenerative braking is braking. Often the generated electric energy is simply dissipated as heat, recovering some or all of the energy is nice, but often secondary.

Diesel electric trains use regenerative braking and run the current through a resistor grid on the roof. Electric lift trucks often have a large power resistor, and in any case if they use lead acid batteries the recharge is about 10% efficient, so effectively the battery is mostly a resistor. The advantage here is that the electric braking is more reliable and lets you dump the heat away from delicate components. It also means any mechanical brake can be much smaller than a full service brake.

On a ebike using a couple of 100W headlamps to sink the energy would have it's charms. It would save the rims and pads, and be useful when descending at 30+mph.

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Re: E bike recommendation

#193673

Postby scotia » January 15th, 2019, 12:06 pm

9873210 wrote:On a ebike using a couple of 100W headlamps to sink the energy would have it's charms. It would save the rims and pads, and be useful when descending at 30+mph.

My vote would be for a handlebar heater. In a Scottish winter, travelling fast in cold air down a long hill, it would be a pleasure to feel some warmth thawing out my numb fingers.

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Re: E bike recommendation

#193675

Postby colin » January 15th, 2019, 12:09 pm

I don't think it should be that complicated to recharge an e bike on downhills, perhaps using a cheap dynamo with a voltage regulator but instead of wiring it to a headlamp wire it to the battery? This would slow the bike down a little on descents but if two dynamos were used one either side of the front wheel rim the slowing effect would be stronger. But then a lever on the handlebar like a gear shift lever would be needed to mechanically flick the dynamos away from the rims at the bottom of hills otherwise the battery would be draining just to charge itself.
Or what about a charging cycle suit made from solar panels? The motorists couldn't ignore you then!

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Re: E bike recommendation

#194363

Postby 9873210 » January 17th, 2019, 7:42 pm

If you just want a little bit of drag then charging a battery would not be too complex. However in some circumstances the brakes need to handle more than 1000W. For a ebike sized battery this is going to qualify as fast or very fast charging and is where things get tricky. For most battery chemistries fast charging needs to be tightly controlled. If you violate certain constrains it will damage the battery or even cause what the data sheets describe as "energetic self disassembly".


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