Optimizing range for lightweight electric Bromptons

[polyphasic]

This is a thread for discussing long-range lightweight Brompton kits. The goal is to be able to carry a lightweight Brompton while not in use while maximizing the distance the electric assistance provides while cycling. Bottomline, how do we optimize on the assistance to create an optimal speed and distance with minimal carrying weight. In short, less energy for greater distance at 15-22mph.

 

[polyphasic]

I'm posting a reply to my thread for the sole reason to not direct a conversation solely on my initial thoughts on range as I'd like for this thread to expand beyond my current state of thinking. In other words, please don't let what I'm about to say steer the thread to one thought. Unlike my older sister, I do not go into tantrums when conversations deviate from my initial post. I'm completely new to the electric bike scene so my thinking might be completely moot for a veteran behind an electric bike, however the central thought should stay in the parameter of optimizing range/speed. I'm not interested in the American youtube clips of going highway speeds on an ebike however speeds up to 25mph do peak my interest, however I have to reserve that interest as I'm speaking to an audience that has 15mph as a limit. I'm not interested in heavy bikes as I want a folding bike to carry over far distances. Clearly more experience e-cyclists will have more perspective/experience on range than someone who is completely new to electric kits such as myself.

With that said, I'd like to first start off with asking JerrySimon approximately how many times are you forced to stop along your work route on average? Assuming you have a stock 50 tooth chainwheel, what's your average speed or average time? How consistently are you above the assistance limits of the nano, i.e. going over 14mph through pedaling? One of the contentions regarding the AtoB estimates is that the riders are pedaling over 14mph thus not using power but solely using human energy of pedaling. Assuming most Bromptons are equipped with 50 tooth chainwheels.

I'll put this in perspective. In Manhattan, approx. 20 blocks or 5-10 avenues equal a mile. That's a lot of lights per mile (@ $245 for each strictly enforced light a bicyclist runs, you will be a good bicyclist and stop. Run two in a row, $490...can quickly add up....ask Peter from nycewheels. )

So nycewheels estimates with pedaling that the crystalyte 209 would take you exactly one 5 mile trip with a 2.3Ah battery, which has me wondering if this estimate is solely based on a NYC mile of numerous stops and goes. I live in NYC metro in the Stepford plains of Connecticut, so my mileage would be significantly higher if this were the case.

Oh and if anybody can provide a historical reference behind the laws that limit cycling to 15mph in Europe, then I'd greatly appreciate it. I believe there is an argument behind safer speeds at higher mph on city streets. At the very least NYC argues that the reason the speed limit in NYC is 30mph is because 80% of pedestrians hit survive at that speed whereas at 40mph pedestrians are killed 80% of the time. Now I mention this because in suburbia the speed on back road in the average vehicle is generally 30mph, so to put the cyclist at risk at 15mph seems backwards from the data available.

 

[eddieo]

You want to go faster for longer well to me that means a heavier bike.... Its a case of horses for courses (the right vehicle for the job)

Many dont take to much notice of lights in UK, more interested in own safety, and like to get away from charging traffic.....

I admire your J walking laws, pedestrians in UK think nothing of walking out blindly into traffic like zombies on a mission..they are a real pain

UK/EU law means e bikes escape legislation as long as 250 watt max and restricted to 15.5. I'm fat and relatively unfit but its enough power for me......You need more? buy a moped and get licence/insurance etc...is my view

I know you can have 350 watt bikes in some states in USA, but I thought E bikes were banned in NYC?

 

[flecc]

Oh and if anybody can provide a historical reference behind the laws that limit cycling to 15mph in Europe, then I'd greatly appreciate it.

I know of no published reference now, but the basis of the speed limits in Japan, the UK and the EU in all cases was what was considered to be normal cycling speeds for utility cyclists, excluding sport cyclists who are considered not to need assistance.

The Japanese law is the strictest, based on an assumption that a normal cycling speed is 15 kph (9.4 mph). Therefore they require that power continuously phases down from that point and ends completely by 24 kph (15 mph). The result of that is very weak assistance by about 12 mph. You can read more about that in my article on the operation of the original Panasonic system on this link.

The original UK law considered normal utility cycling speed to be 12 mph, so the speed limit power cutoff for electric-assist bikes was fixed at that at the outset. There was no power phase down prescribed and throttles are allowed. However, the EU policy of transport harmonisation meant consistency with Europe, so in 1987 that limit was increased to 15 mph, roughly equivalent to the EU's 25 kph limit. The prospect of allowing such fearful speeds scared parliament sufficiently to introduce a lower age limit of 14 years as well at that time, unique to the UK within the EU.

And as you will have derived from the above, the EU view on normal cycling speed is 25 kph (15.6 mph), but their law which also exists in parallel here in the UK requires power to phase down as it approaches the cutoff speed (but no slope gradient or point of phase down start prescribed) and control by pedalling, no power allowed without pedalling.

Currently our UK regulations and the EU regulations are under review and changes will appear in about a years time, when it's expected that UK and EU law will be very closely aligned.
.

 

[polyphasic]

You want to go faster for longer well to me that means a heavier bike.... Its a case of horses for courses (the right vehicle for the job)

Many dont take to much notice of lights in UK, more interested in own safety, and like to get away from charging traffic.....

I admire your J walking laws, pedestrians in UK think nothing of walking out blindly into traffic like zombies on a mission..they are a real pain

UK/EU law means e bikes escape legislation as long as 250 watt max and restricted to 15.5. I'm fat and relatively unfit but its enough power for me......You need more? buy a moped and get licence/insurance etc...is my view

I know you can have 350 watt bikes in some states in USA, but I thought E bikes were banned in NYC?

I guess my line of thinking was say you bought the nycewheels bike with a top speed of 18mph. If you fitted it with a 54 tooth chainwheel, then you could pick up on the momentum created by the crystalyte 209 in top gear and give the motor a rest in the same way a 50 tooth Brompton does in Nano tests.

Yes, electric bikes are illegal in NYC, yet it's rarely enforced.

I'm not interested in a debate of whether over 15mph equates moped. I probably made a huge mistake by asking for the historical reference behind the 15mph law, so I take full responsibility for the conversation going in that direction. Please don't let that skew the conversation to a debate over the European limit. There are plenty of threads on that, however I would be interested in discussions of maximizing speed with an electric bike using human power with the assistance of the motor.

My line of thinking was using momentum created by the cutoff point of these 180-250 watt motors which seems to be around 15.5mph (or 18mph for the U.S. crystalyte 209) then using human power above that.

I was at the New Amsterdam Bike Show a couple of months ago. There was a product called speed-drive (mountain-drive, high-speed drive, etc.) by schlumpf innovations which is an internally geared crankset. [video=youtube;p_9CRMgDbRA]http://www.youtube.com/watch?v=p_9CRMgDbRA[/video] (Alles ueber Schlumpf Innovations: Wasserpumpe, Einradnaben, Fahrradantrieb. Hersteller & Entwickler.) out of Switzerland which used the gearing range of both the derailleur and a hub-gearing system creating a gearing range as huge as a 67t chainring through simply hitting a button. It's an $800 system and the owner seemed to think it would work on a Brompton. Whether it would, I have no idea.

At any rate, I'm not talking about creating a Brompton at crazy speeds. I've seen enough youtube clips of highway speed electric bikes to make me want to push for regulation here in the states. I would love to see average speeds between 15-25mph on suburban/rural roads (and certain areas in the city) where those speeds would be safe (or even safer) and responsible as with any road bike. Clearly the motors cutoff at some point, most cutoff below 15mph. The nycewheels bike I believe cuts off below 18mph, so what I'm talking about here is more human power than electric I suppose. Yet at the same time, I do wonder how many more miles a person could crank out from the battery guzzling Crystalyte 209 with the right crank equipment in place (all of this likely is assuming we're on a flat terrain).

 

[polyphasic]

I know of no published reference now, but the basis of the speed limits in Japan, the UK and the EU in all cases was what was considered to be normal cycling speeds for utility cyclists, excluding sport cyclists who are considered not to need assistance.

The Japanese law is the strictest, based on an assumption that a normal cycling speed is 15 kph (9.4 mph). Therefore they require that power continuously phases down from that point and ends completely by 24 kph (15 mph). The result of that is very weak assistance by about 12 mph. You can read more about that in my article on the operation of the original Panasonic system on this link.

The original UK law considered normal utility cycling speed to be 12 mph, so the speed limit power cutoff for electric-assist bikes was fixed at that at the outset. There was no power phase down prescribed and throttles are allowed. However, the EU policy of transport harmonisation meant consistency with Europe, so in 1987 that limit was increased to 15 mph, roughly equivalent to the EU's 25 kph limit. The prospect of allowing such fearful speeds scared parliament sufficiently to introduce a lower age limit of 14 years as well at that time, unique to the UK within the EU.

And as you will have derived from the above, the EU view on normal cycling speed is 25 kph (15.6 mph), but their law which also exists in parallel here in the UK requires power to phase down as it approaches the cutoff speed (but no slope gradient or point of phase down start prescribed) and control by pedalling, no power allowed without pedalling.

Currently our UK regulations and the EU regulations are under review and changes will appear in about a years time, when it's expected that UK and EU law will be very closely aligned.
.

Interesting historical info. I probably will regret though asking about it as I see I've steered the conversation towards these speed limit laws. Sigh, but thank you for this information. It's interesting nonetheless.

I'm sure it could go way back historically. I recently learned about NYC in the 19th century. H

ow electric charging stations were around. The speed limit in NYC was 8mph in 1895, 4mph while turning. The first person to be arrested and imprisoned for speeding in the U.S. was a NYC cab driver behin​

d the wheel of an electric car going a crazy speed of 12mph in 1899. In 1899, 90% of taxi-cabs were electric and one-third of automobiles in NYC were powered by electricity. This 1909 vehicle went 110 miles on a charge at 25 mph was considered fast and furious. I'd love to be sporting a moving phone booth in 1909. Now I've really steered the conversation off course, lol. Dang it!​

[video=youtube;O9vC3S8MJPY]http://www.youtube.com/watch?v=O9vC3S8MJPY[/video]​

 

[flecc]

Back on course.

The range of any electric assist bike can be optimised at any required level merely by adjusting the cut-off speed in relation to the rider's ability in terms of endurance and strength.

The A to B formula of a known very strong rider on a bike he is well used to, the Brompton, coupled to a low 13 mph cutoff showed that with a 48 mile range.

At the other extreme, the early eZee Torq which cutoff the assistance at 22 mph gave many owners, including me, only 15 miles range from it's 36 volt 10 Ah battery.

 

[polyphasic]

Back on course.

The range of any electric assist bike can be optimised at any required level merely by adjusting the cut-off speed in relation to the rider's ability in terms of endurance and strength.

The A to B formula of a known very strong rider on a bike he is well used to, the Brompton, coupled to a low 13 mph cutoff showed that with a 48 mile range.

At the other extreme, the early eZee Torq which cutoff the assistance at 22 mph gave many owners, including me, only 15 miles range from it's 36 volt 10 Ah battery.

haha, thanks for bringing it back on course. Let's go with that eZee torq of 22mph. I'm going to make the assumption that someone that opted for the 54 tooth chainwheel would get more range and speed than someone that opted for the 44 chainwheel option. Any ideas of what the typical speed is for a 44t, 50t, 54t chainwheel on a Brompton for flat terrain? I never can find the page that I like so much that talks about gear range and speeds.

But this page has the Schlumpf Brompton gear calculator. http://xldev.co.uk/bgc.html

The Schlumpf speed drive example is similar to a 67 tooth yet the chainring size is less than 5 inches (124mm). So it's like a 40t chainring size that gives a gearing range that would normally require a 67 tooth chainring size.

I may have those numbers wrong above because I'm so new to this I feel like I'm talking out of my rear...nor am I certain how that would affect cycling speed on flat terrain, but I wonder whether it'd help extend range even on a eZee torq kit by making the bike easier to pedal at higher speeds. Does that make sense?

 

[eddieo]

I had a go on an E bike with that two speed Schlumpf drive last year, same as in your video above.... you tap the crank with your heal to change, and while it sounds odd it actually worked very well and range was spot on for a two gear system. I tried it in my local reasonably hilly area and could have lived with it I think.....

Although more then happy with my XT set up

on my " best folder" thread, link to german site where chap fitted 11 speed Alfina hub gear to a Brompton

 

[polyphasic]

I had a go on an E bike with the two speed Schlumpf drive last year, you tap the crank with your heal to change, and while it sounds odd it actually worked very well and range was spot on for a two gear system...

Yeah, it seemed pretty amazing at the bike show. They had one on display to test ride. I didn't get on it, but I watched enough people and talked to the owner which all seemed pretty convincing. Looking at this Brompton Gear Calculator, it appears if you had a Schlumpf high-speed drive with a Sturmey Archer XRF8(w) 8 speed hub, you'd not only have 16 speeds, but you'd have a gear inch range from 45 to 462 inches. Pretty remarkable considering a stock 6 speed brompton with the standard 50 tooth has a gear-tooth range from 33 to 99.

Adding the Schlumpf high-speed drive alone would increase the gear range from 33 to 252 inches, yet at $800 it's expensive.

The Sturmey Archer XRF8(w) is $170 and would double the gear range from 99 inches to 181. http://www.treefortbikes.com/product/333222358452/716/Sturmey-Archer-S80-XRF8.html

XRF8(w) doubles the highest gear and the Schlumpf multiplies that by 2.5. I'm curious as to how fast that would make the Brompton...seems like a downhill adventure to me. Almost too high of gear-inches for flat terrain, no?

http://xldev.co.uk/bgc.html

The heavy rohloff would be amazing in mountainous terrain...28 speeds, but that is off topic for the purpose of flat terrain...it just looks remarkable though to see there are so many options for gearing with such a broad range.

So maybe just maybe the gearing could increase range more than anything else on flat terrain. I'm not sure, just thinking out loud.

 

[flecc]

Yes, that makes sense polyphasic, getting the cadence to suit a rider does make it easier to maintain certain speeds.

The soulbikes calculator is probably what you need, it accepts chain wheel and rear sprocket sizes with wheel size entry below, and the Analyse readout gives road speeds and cadences:

HPV Drivetrain Analyzer / Gear Calculator

P.S, Although the Schlumpf works well, it as accepted to be a bit inefficient, with added drag.
.

 

[polyphasic]

Yes, that makes sense polyphasic, getting the cadence to suit a rider does make it easier to maintain certain speeds.

The soulbikes calculator is probably what you need, it accepts chain wheel and rear sprocket sizes with wheel size entry below, and the Analyse readout gives road speeds and cadences:

HPV Drivetrain Analyzer / Gear Calculator

P.S, Although the Schlumpf works well, it as accepted to be a bit inefficient, with added drag.
.

Oh wow, that calculator is intense. Hmm, drivetrain inefficiency appears to be around 3%.

So that 8 speed Sturmey Archer looks like it's about 4 pounds (about 2 pounds heavier than the 6 speed by Brompton)

I noticed the single and 2 speed by Brompton has a top gear inch of 69 for a stock 50 tooth chainwheel, the 3 speed at 79 and 6 speed at 99 gear inches. So I guess the 6 speed is technically faster than a 2 or 3 speed. That may have an impact on range for these Nano bikes.

This is an interesting thread regarding the Schlumpf. Appears I just need to do some googling on the topic and stop talking out loud so much here. Brompton & Schlumpf High Speed Drive? [Archive] - Bike Forums

 

[jerrysimon]

With a two speed setup and 54T main (12T rear) my Brompton has a top gear of 74"

This gets me up to about 23+ mph before I begin to spin out, though of course I have long since switched off assistance at around 15-16mph before that.

The other 16T rear gives me 56" in first, which is fine for starting off and the odd hill round Cambridge

Regards

Jerry

 

[polyphasic]

With a two speed setup and 54T main (12T rear) my Brompton has a top gear of 74"

This gets me up to about 23+ mph before I begin to spin out, though of course I have long since switched off assistance at around 15-16mph before that.

The other 16T rear gives me 56" in first, which is fine for starting off and the odd hill round Cambridge

Regards

Jerry

The mph before spinning out is very helpful information. 23mph+ is a great cruising speed, so maybe I'll convert my 6 speed back down to a 2 speed. I'm feeling rather confident that I likely won't need the lower gear inches that the 6 speed provides with the electric assistance, but I won't know about the upper limit of 99" until I get kit installed and experiment on hill climbs. I ordered both the 50t and 54t so that I could see which one I liked better.

I'm sure pedaling technique is everything for a pedelec, seems throttle has more techniques.
http://www.electricbike.com/increasing-range/

 

[shemozzle999]

I recently fit the Brompton BWR rear hub to my 6 speed Brompton to help reduce the cadence at the top end speed, which was fine, but found the steps between are too great for assisted travel.
I shall be reverting back to the old Sram setup I removed and will probably go down the 54T crank route instead, as well.
I very rarely visit the low speed gears on an assisted bike, apart from starting off.

 

[polyphasic]

I recently fit the Brompton BWR rear hub to my 6 speed Brompton to help reduce the cadence at the top end speed, which was fine, but found the steps between are too great for assisted travel.
I shall be reverting back to the old Sram setup I removed and will probably go down the 54T crank route instead, as well.
I very rarely visit the low speed gears on an assisted bike, apart from starting off.

Hmmm, interesting. It appears the SRAM 3 speed has a range from 46" to 87" on a 50T.

So a BWR on the rear 13 sprocket would give you

40.6

63.7

99.7

And the SRAM on 50t would be:

46.5

63.7

86.6

It does seem like a marginal change in the top end, but I guess you were looking for something greater than 87". It appears a 54t on SRAM would bump that up to 94".

Oh and I was incorrect when I previously said the BWR goes to 99" on 54t, it's 108". I'm not really sure what these numbers mean in the real world of riding the bike...I shall see those soon enough.

 

[flecc]

I'm not really sure what these numbers mean in the real world of riding the bike...I shall see those soon enough.

Using your numbers, in general cycling terms, an 86" top gear is a fairly typical utility cycling one, a 99" is a touch on the high side, and a 108" is definitely high.

Referring to that 22 mph assist eZee Torq that I mentioned earlier, the prototype had a 132" top gear which was far too high, the production version a 122" gear which was still a bit too high for most at it's 22 mph cruising.

 

[jerrysimon]

Maybe I am just slow but I have to admit it took me ages to get my head round these gearing ratios and as you say the best way to understand them is to fit them and try them in a real life situation.

For me 23mph is way more than cruising speed. You guys must have bionic legs!

Although 74" is ok in top, I think for me 80" would be optimum. However I am not prepared to sacrifice weight gain by fitting a hub to my two speed Brompton. Higher cadence helps give me a little workout too if I feel I need it

Regards

Jerry

 

[jhruk]

I'm sure pedaling technique is everything for a pedelec, seems throttle has more techniques.
5 Easy Ways to Increase Your Ebike Range Up To 50% | ELECTRICBIKE.COM

Yes, as with a gas vehicle driving style is an important factor in your power consumption. Gentle acceleration, anticipation, avoiding stopping, limited use of full throttle, will all make a big difference.

On a throttle controlled electrically assisted bike your battery range is solely dependant on how much assistance you call for, by using the throttle. The battery will give you a set amount of power assistance, but how you use it is entirely up to you. This may sound rather obvious but if you only use it for help on the hills, and can pedal unassisted on the flat, your battery will take you a lot further than if you use it all the time to maintain a higher speed.

My experience is that consumption will vary over the course of a journey. I will often travel many miles on mine before realizing I haven’t switched it on yet, which would give a very large range indeed. However the last few miles of long trip are a rather different matter and my average consumption over those last miles, when I’m most tired, would suggest quite a short range.

Although I guess the Crystalyte and Tongxin motors have similar efficiencies I would expect the Crystalyte would in practice give you the least range, largely because you will be more tempted to use its higher speed to increase your average.