Do Nano and Swytch electric upgrades threaten forks?

[bonzobanana]

Maybe I am a bit German here but I do not consider this a valid statement and am also wondering on what foundation you think that hub Motors for a Brompton are not that "powerful". The Brompton fork is not designed to take any torque at all as on a human powered Brompton you would not have torque on the fork. You have a huge range of different motors from Crystalite direct drives to geared motors like the Tonxin models, that are used in most retrofit kits today. They do have a nominal power of "just" 200-250 Watts but can vastly go beyond that in certain situations. The amount of torque they produce is most of the time not even layed out in the datasheets of the motors.

Steel forks on the other hand are vastly different, too: From a massive fork of a BMX bike or a cargo bike over slim elegant models on Racebikes to cheaply build forks on bikes from a hardware store. There are dozends of different steels, each with their individual properties. There are well crafted and badly crafted forks. There are different fork designs. Just because the fork ist made of steel this means exactly nothing.

Do you have any experience with a retrofitted motor in a Brompton? Are you an engineer with experience in bicycle fork design and specification? Most retrofit motors just use the existing dropout to keep the motor's momentum unter control - clearly nothing that the Brompton dropouts were designed for. There is a reason why torque arms exist: https://ebikes.ca/product-info/grin-products/torque-arms.html
And on the other hand there is a reason why forks for disc brakes are stronger and differently designed from forks for rim brakes. There is way more to consider than just the dropouts as forces from a motor (or a disc brake) onto the fork are obviously completely different from no forces onto the fork...

So generalisations do not work here, neither with motors nor with forks. There are a lot of bikes with steel forks where I never ever would fit a motor.

Practice seems not to have shown massive issues - still this is a bet because probably no one ever really checked the Brompton forks regarding the use of a motor from a solid engineer's perspective including tests, measurements and reviewing desingns and materials. Apart from Brompton themselves - and they changed the design of their fork for the electric version. As this rises cost this says something: They probably wouldn't have done it w/o a reason. So it is probably a valid assumption that current retrofit motors typically do not overload the fork under normal circumstances (that's what the practice shows but no one takes warranties for that) but that on the other hand the fork is probably used beyond it's spec, technically within the stretched safety zone buffer and this seemed not to be safe enough for Brompton themselves (thus they designed a stronger fork for their Electric).

There are definitely steel forks I wouldn't want to use with a hub motor but my point was more about the material steel being more dense and being better to deal with the torque of a hub motor on the dropouts especially a small geared hub motor which might only produce up to 45Nm or less and be relatively low speed. People fit 2000w hub motors to the dropouts of aluminium frames which are much softer, often they have to fit torque arms to prevent the dropouts getting chewed up. It's pretty much always easier to fit ebike kits to steel frames and forks where as aluminium and carbon fibre need much more consideration and sometimes reinforcing.

Lets not forget that having a front hub motor means going up hills is now a 2 drive system with the driving force shared between two wheels. This can reduce the flexing in the frame itself as the rider doesn't have to work so hard. There are positives to a hub motor on the fatigue on the frame itself its not all negative. Sharing the driving power between the two wheels can be a positive thing.

I understand your points and I accept many of them but I guess my point is in the scheme of things steel frames and forks typically are much easier to fit ebike kits too safely compared to other materials.

The cheapest nastiest ebike I know which before pandemic pricing was sold at £299 is the Assist ebike at Halfords. It has quite thin high tensile steel forks that are nothing special and a front hub motor and the bike has a total load capacity of 160kg including bike weight, luggage etc. The forks don't appear to be any different to the forks fitted to the same frame when it has a hinge fitted in the middle and sold as a basic non electric folding bike. I think the spoke count has increased to 36 spokes though.

Lots of people who fit ebike kits to steel frames and forks don't even bother with torque arms even when fitting very high wattage hub motors that produce torque between 100-200Nm.

 

[berlinonaut]

The cheapest nastiest ebike I know which before pandemic pricing was sold at £299 is the Assist ebike at Halfords.

It is impossible that a brand new ebike for GBP 299 ist anything else but trash from factory. Even a non-ebike for that price would have to make a lot of compromises and for the money you would have a hard time finding a motor kit alone that works (and you won't be able to find one that has at least acceptable quality).

Lots of people who fit ebike kits to steel frames and forks don't even bother with torque arms even when fitting very high wattage hub motors that produce torque between 100-200Nm.

I do have my doubts here. The most powerful legal mid-motors in the 25kph range produce like 95NM, most way lower than that. And those need more torque as they are using the bike's gearing, so what arrives at the wheel is way less. A typical quality direct drive motor for the rear wheel is rated to about 40 NM. Even the Neodrives RS 45kph motor that is rated to 500W (and 1200W peak) is rated to 40NM: https://www.neodrives.com/de/antriebssystem/z20-rs/z20-rs-heckmotor/

People fit 2000w hub motors to the dropouts of aluminium frames

When I was a boy my understanding of mechanics was: As long as it physically fits it will work. A couple of destructive experiences later I had learned that this is untrue. Seems that there are people who still have to learn that lesson. To their luck the power ratings of those motors you mention a probably often plain phantasy. A fool with a tool is still a fool.

 

[Tenkaykev]

Steel is the right material for a hub motor, typically the way a hub motor damages a fork is twisting within the dropouts but that is more an issue for softer/weaker aluminium or carbon fibre where it hasn't been strengthened for force to be applied in such a way. These little hub motors that go into Brompton ebike conversions I don't think are that powerful. Yes the forks are being used a little beyond their expected use but steel is a material that is very abuse-able.

View attachment 665339

Saddle’s a bit low.

 

[bonzobanana]

It is impossible that a brand new ebike for GBP 299 ist anything else but trash from factory. Even a non-ebike for that price would have to make a lot of compromises and for the money you would have a hard time finding a motor kit alone that works (and you won't be able to find one that has at least acceptable quality).

I do have my doubts here. The most powerful legal mid-motors in the 25kph range produce like 95NM, most way lower than that. And those need more torque as they are using the bike's gearing, so what arrives at the wheel is way less. A typical quality direct drive motor for the rear wheel is rated to about 40 NM. Even the Neodrives RS 45kph motor that is rated to 500W (and 1200W peak) is rated to 40NM: https://www.neodrives.com/de/antriebssystem/z20-rs/z20-rs-heckmotor/

When I was a boy my understanding of mechanics was: As long as it physically fits it will work. A couple of destructive experiences later I had learned that this is untrue. Seems that there are people who still have to learn that lesson. To their luck the power ratings of those motors you mention a probably often plain phantasy. A fool with a tool is still a fool.

I've seen those Assist ebikes out and about, I saw a couple on them riding here in Yeovil, they were going up a mild hill too. I think its one of the top sellers at Halfords for ebikes obviously due to price. Also being based on a folding bike frame that doesn't fold its smaller than other bikes so they get more in the shipping container. It's going to be fully certified as Halfords are very exposed (they take one pound in every four spent on cycling in the UK and have an estimated 40% marketshare for bikes). They are absolutely huge in the UK. The battery is very low capacity of course and it is single gear. I've seen some forum threads about them and most seem reasonably happy. I'm not sure about that bike but most Halfords bike have a lifetime guarantee on the frame and forks. I think the idea that they are somehow chancing it is not realistic. When you look at bike recalls there has been pretty much none for Halfords despite their huge level of sales. It's not like Decathlon where there has been a large amount of recalls possibly related to their much lower weight limits or many high end bikes which typically sacrifice strength for lightness and sometimes sacrifice too much strength. I'd have more confidence riding that Assist bike for strength than many Tern or Dahon bikes. The point is you don't get many recalls on high tensile steel bikes or bikes fitted with high tensile steel forks.

Obviously with regard high wattage hub motors they are not legal used in the UK or Europe unless licensed as a electric scooter, moped or motorbike. However a huge amount of hub motors are sold in other markets with huge wattage. Even in the UK some people chance it with ebikes with hub motors up to something like 3000W possibly more and these still fit to conventional bike frames. A direct drive hub motor given only 250W might be 30-35Nm peak torque but a larger more powerful hub motor given over 10x that will obviously produce a lot more torque and the windings will be changed to produce torque rather than speed as the wattage goes up I would of thought. Those so called legal mid-drive motors you mention use up to 800W when producing that much torque, 95Nm. The 250W rating is a farce the EU legislation seems to be made overly biased in favour of mid-drive motors in how it is written which is what many European brands produce. It's just another type of tariff of sorts in order to reduce hub motor sales and Chinese products. Same issue with forcing a pedelec type system when in most markets ebikes use throttles as their main power control which is cheaper and safer. When a Bosch motor draws something like 23-25A from a 36V battery that is not 250W (24x36). The point is give a hub motor similar power and it will happily produce similar torque especially geared hub motors and give it 2000-3000W obviously it will produce a lot more torque again. It's perfectly legal for a farmer for example to use a 3000W ebike on his own land of course I very much doubt everyone buying such a ebike has such land.

https://www.ebikeschool.com/myth-ebike-wattage/

 

[berlinonaut]

I think the idea that they are somehow chancing it is not realistic.

Just because something is crappy from a craftsmanship perspective or of low quality it does not need to be unsafe or unreliable.

Obviously with regard high wattage hub motors they are not legal used in the UK or Europe unless licensed as a electric scooter, moped or motorbike. However a huge amount of hub motors are sold in other markets with huge wattage. Even in the UK some people chance it with ebikes with hub motors up to something like 3000W possibly more and these still fit to conventional bike frames.

As said before: A fool with a tool is still a fool. I'd say most of the people using these motors are absolutely not knowing what they are doing and have a total lack of understanding of materials.

The 250W rating is a farce the EU legislation seems to be made overly biased in favour of mid-drive motors in how it is written which is what many European brands produce. It's just another type of tariff of sorts in order to reduce hub motor sales and Chinese products.

The legislation is way older than the mid-motor trend and at the time of the legislation and thereafter there were a lot of European brands producing hub motors - some still do. In Germany i.e. Heinzmann and Albers. Bosch did take over wider parts of the market (which I personally find unpleasant) but not due to the legislation but due to the quality of their drives for one, the ability to invest massively and to scale qucikly second, their general experience in building stuff third and last due to the fact that they were able to make deals with most mainstream manufacturers fifth. But until they came to a dominant postition took years and years (if I remember correctly they entered the market only at around 2010 and at that time Panasonic mid motors were dominant). Mid motors in general have advantages when it comes to steep hills (which helps against Geman Angst ) and many of the competing companies suffered from reliability problems - namely BionX ruled themselves out of the market this way, starting from a market leader position. Today, apart from Bosch there is a massive share in mid motors from Shimano as well and outside Europe apart from the Chinese Yamaha is dominant, they even sell their own bikes (and announced only a couple of weeks ago that they now want to seriously start conquering the European market). Bafang produces all sorts of motors and is trying to gain traction in the higher level markets, coming from the budget low end bit of the market. So I'd say the situation is way more complex than your analysis suggests.

Also I do not see an issue with the 250 Watts permanent while peak power can be higher. It is a bit tricky to objecitvely measure that, but a normal rider is in no way able to produce 250Watts of permanent power output and on the other hand in certain situations like on grades or when starting over more power is necessary. In opposite: I see the legislation as a generally pragmatic and useful ruling. The one thing I dislike (and I dislike this heavily) is the limitation to 25 kph. In the US the rating for the same class is 32kph - owning an oldfashioned BionX rear direct drive that can be switched between both modes I can state from experience that 32 kph is way more practical and useful in daily traffic (and I'd also say more safe) - but unfortunately illegal.

Same issue with forcing a pedelec type system when in most markets ebikes use throttles as their main power control which is cheaper and safer.

I would doubt that. The whole idea of an e bicycle is that you have to pedal. Throttles avoid that. This is then a moped, not a bicycle. There used to be petrol vehicles like that (google for "Saxonette") and - equal to bike with throttles w/o PAS - they needed an insurance. This was back in the 80ies. And you'll find examples ranging back to the 50ies for that.

The UK are - sorry if that may sound rude - a bit of a developing country when it comes to electric bikes. Many continental countries like the Netherlands (or Benelux in general), Austria, Switzerland, Germany and many others hopped on the ebike book a decade earlier. This has consequences in terms of experience and knowledge. I am always baffled when I read tests on UK news sites about ebikes about how incompentent they judge about motor steering and many other technical aspects in comparison to continental sites.
A simple PAS is a poor low end solution, only choosen because it is cheap. A torque sensor is a totally different world and so much better (if you are not disabled in a special way) but most in the UK do not even know that it exists, let alone about the differences. You can clearly see this in discussions about Brompton retrofits vs. factory: Almost nobody mentions this, but many praise the Swytch which is really as trashy as you can get...
You can btw. w/o issues legally combine a throttle with a PAS or a Torque sensor. It just needs like 3€ more worth in material, a controller that is able to deal with it and the competence to program the controller accordingly. Seems to complicated for most kit-offerings...

Coming back to the Brompton: Comparing retrofit kits with the Brompton Electric is often apples vs. oranges the way people do it and this often does not lead to a good outcome.

 

[Tenkaykev]

Also I do not see an issue with the 250 Watts permanent while peak power can be higher. It is a bit tricky to objecitvely measure that, but a normal rider is in no way able to produce 250Watts of permanent power output

This is something that I had to deal with from time to time when I worked in the Electric motor repair trade. A customer would bring in a motor that had failed due to overload. It might say 1KW for example on the data plate, but with items such as industrial equipment there is a Duty rating ." S1" is continuously rated, that means, the motor will happily provide 250 watts for as long as required. This rating goes all the way to S10 with various restrictions on the amount of time that you can use the maximum power without forced cooling and /or rest periods. A 250 watt continuously rated motor for example may well be capable of delivering 400 watts or higher for a period of time without issue, but not continuously.

 

[ExBrit]

Would agree. "Not good enough for Brompton" could also mean: They did the mandatory ISO test with the original fork and did not pass. It could also mean: They just wanted to be safe, even that there were no issues during the test. It could even mean: They wanted a differentiator from the competition an thus enforced the fork though there was no technical reason for that - with the benefit that potential retrofit kit buyers would feel unsafe and rather buy a enforced original Brompton Electric instead of retrofitting a kit.

It just occurred to me that Brompton might think the average weight of an electric rider is likely higher than the average weight of a non-electric rider

 

[Schwinnsta]

Would agree. "Not good enough for Brompton" could also mean: They did the mandatory ISO test with the original fork and did not pass. It could also mean: They just wanted to be safe, even that there were no issues during the test. It could even mean: They wanted a differentiator from the competition an thus enforced the fork though there was no technical reason for that - with the benefit that potential retrofit kit buyers would feel unsafe and rather buy a enforced original Brompton Electric instead of retrofitting a kit.

I think we all can agree that they did not consider front-wheel drive on the non-electric, and that they did consider it for the electric.

 

[a.twiddler]

So, would the fork for the electric version be available as a a spare part for someone who wanted to play it safe if doing a conversion, and would it be significantly different or more expensive compared to a standard steel fork?

 

[ExBrit]

So, would the fork for the electric version be available as a a spare part for someone who wanted to play it safe if doing a conversion, and would it be significantly different or more expensive compared to a standard steel fork?

The video mentions they beefed up the stem too.

 

[bonzobanana]

Just because something is crappy from a craftsmanship perspective or of low quality it does not need to be unsafe or unreliable.

As said before: A fool with a tool is still a fool. I'd say most of the people using these motors are absolutely not knowing what they are doing and have a total lack of understanding of materials.


The legislation is way older than the mid-motor trend and at the time of the legislation and thereafter there were a lot of European brands producing hub motors - some still do. In Germany i.e. Heinzmann and Albers. Bosch did take over wider parts of the market (which I personally find unpleasant) but not due to the legislation but due to the quality of their drives for one, the ability to invest massively and to scale qucikly second, their general experience in building stuff third and last due to the fact that they were able to make deals with most mainstream manufacturers fifth. But until they came to a dominant postition took years and years (if I remember correctly they entered the market only at around 2010 and at that time Panasonic mid motors were dominant). Mid motors in general have advantages when it comes to steep hills (which helps against Geman Angst ) and many of the competing companies suffered from reliability problems - namely BionX ruled themselves out of the market this way, starting from a market leader position. Today, apart from Bosch there is a massive share in mid motors from Shimano as well and outside Europe apart from the Chinese Yamaha is dominant, they even sell their own bikes (and announced only a couple of weeks ago that they now want to seriously start conquering the European market). Bafang produces all sorts of motors and is trying to gain traction in the higher level markets, coming from the budget low end bit of the market. So I'd say the situation is way more complex than your analysis suggests.

Also I do not see an issue with the 250 Watts permanent while peak power can be higher. It is a bit tricky to objecitvely measure that, but a normal rider is in no way able to produce 250Watts of permanent power output and on the other hand in certain situations like on grades or when starting over more power is necessary. In opposite: I see the legislation as a generally pragmatic and useful ruling. The one thing I dislike (and I dislike this heavily) is the limitation to 25 kph. In the US the rating for the same class is 32kph - owning an oldfashioned BionX rear direct drive that can be switched between both modes I can state from experience that 32 kph is way more practical and useful in daily traffic (and I'd also say more safe) - but unfortunately illegal.

I would doubt that. The whole idea of an e bicycle is that you have to pedal. Throttles avoid that. This is then a moped, not a bicycle. There used to be petrol vehicles like that (google for "Saxonette") and - equal to bike with throttles w/o PAS - they needed an insurance. This was back in the 80ies. And you'll find examples ranging back to the 50ies for that.

The UK are - sorry if that may sound rude - a bit of a developing country when it comes to electric bikes. Many continental countries like the Netherlands (or Benelux in general), Austria, Switzerland, Germany and many others hopped on the ebike book a decade earlier. This has consequences in terms of experience and knowledge. I am always baffled when I read tests on UK news sites about ebikes about how incompentent they judge about motor steering and many other technical aspects in comparison to continental sites.
A simple PAS is a poor low end solution, only choosen because it is cheap. A torque sensor is a totally different world and so much better (if you are not disabled in a special way) but most in the UK do not even know that it exists, let alone about the differences. You can clearly see this in discussions about Brompton retrofits vs. factory: Almost nobody mentions this, but many praise the Swytch which is really as trashy as you can get...
You can btw. w/o issues legally combine a throttle with a PAS or a Torque sensor. It just needs like 3€ more worth in material, a controller that is able to deal with it and the competence to program the controller accordingly. Seems to complicated for most kit-offerings...

Coming back to the Brompton: Comparing retrofit kits with the Brompton Electric is often apples vs. oranges the way people do it and this often does not lead to a good outcome.

Many high tensile steel frames are manufactured by the most advanced equipment including robots, the manufacture of steel frames and forks is extremely advanced. When you look at factories like fuji-ta (world's largest bicycle manufacturer by volume who supply complete bikes to many brands plus frames and forks to many assembly plants) it is the steel side section of the factories that have the robots. Steel has the lowest fault rate at the factory and failure rate by customers.

My point about the legislation is mid-drive motors like Bosch and Brose seem to push the wattage of their motors well beyond 250W and get away with it which hub manufacturers would never get away with. Lets not forget Bosch were heavily involved in dieselgate providing the manipulative technology that knew when it was being tested and changed its emissions. They are not a company that embraces honesty and integrity. From what I've seen of the certification it is very poorly written.

Obviously a throttle in itself is just a power control it doesn't have to be unconnected with pedalling but in most markets twist and go throttles are legal including the UK until we adopted the inferior EU legislation. On cadence sensor ebikes you can ghost pedal to have the same effect as a twist and go throttle, you basically put the bike into a very easy gear and then twist the throttle to pretty much get the bike to move but there is a delay between the bike sensing the cadence and also stopping its much safer with a twist and go throttle which is why its the standard control in most ebike markets. I've seen torque sensor ebikes compared to twist and go ebikes in the US where they import some Bosch type ebikes and end customers have found the Bosch ebikes to be inferior in how they operate, they prefer the throttle and this doesn't relate to the motor type as many mid-drive motors sold in the US also have throttle controls and you can have both on the same bike and choose between the two. I certainly agree a torque sensor is better than cadence sensor but for me a throttle is by the far the best way of controlling power on an ebike you just use it when you want it and can adjust the power to exactly the level you need at that point, moving away from junctions on a hill etc. It's safe and enables weaker people access to ebikes, elderly, partially disabled or people recovering health as well as being the best power control in urban situations mixing it with larger vehicles, no lag in use absolutely ideal. Certainly no reason to legislate against it. I have no problem with torque sensor ebikes being sold I'm not trying to restrict what people can use rather allow people to have the right product for them. Torque sensing is right in some situations like off-road where you really wouldn't want to be controlling a throttle with intense off-road courses. Twist and go throttles are safer, cheaper, more reliable, more accessible for riders there is no reason to legislate against them unless you are trying to make a unique marketplace more awkward to oversea competitors and then when you factor in the so called legal ebikes from Europe are a lot more powerful than the legal ebikes from outside the EU unless they follow a EU design philosophy of mid-drive with torque sensor.

Saying that I've seen a huge number of videos from the EU where people have fitted ebike kits that are throttle based and twist and go. It seems like many countries the awful EU legislation is ignored by consumers and the police. We shouldn't have legislation that is anti-consumer.

 

[berlinonaut]

So, would the fork for the electric version be available as a a spare part for someone who wanted to play it safe if doing a conversion, and would it be significantly different or more expensive compared to a standard steel fork?

I'd assume they'd be available as a spare part but unfortunately probably not freely. At least in the UK frame parts are only available for fitting at a Brompton dealer and I could imagine that with special parts for the Electric Brompton might only deliver them against a proof that they are indeed used on an existing Electric. This is what i.e. Bosch does with it's motors: While in theory you could (mechanically as well as electrically w/o problems) exchange your existing Bosch drive for a better version (i.e. the cargo version) this is not possible as Bosch will only deliver against proof of an existing motor of the same series.

For the Electric, fork, main frame and stem are all three listed as specific parts for the Electric (in parallel to "normal" parts), so Brompton seem to have changed all three. Funnily enoug the fork for the Electric is slightly cheaper than the standard fork:
70€ for the Electric: https://www.vlerickfietsen.be/nl/brompton-electric-voorvork-glansgelakt vs.
80€ for standard: https://www.vlerickfietsen.be/nl/brompton-voorvork-staal-zijdeglans-greater2018
Main frame (including the torque sensor bottom bracket) - surprisingly cheap: https://www.vlerickfietsen.be/nl/brompton-electric-hoofd-en-voorframe-inclusief-bb
Stem (surprisingly expensive in comparison to the main frame): https://www.vlerickfietsen.be/nl/brompton-stuurkolom-en-pen-h2-type-electric

 

[berlinonaut]

My point ...

Barely anything I would agree with and lots I heavily disagree with. But no point in having this discussion and furthermore not at all relevant to this thread. We should agree to disagree.

 

[bonzobanana]

Barely anything I would agree with and lots I heavily disagree with. But no point in having this discussion and furthermore not at all relevant to this thread. We should agree to disagree.

Nothing I've written is debatable there as far as I can tell all factual, my conclusions about the motivations of EU legislation while often stated in forums by lots of different people are just opinions there has to be reasons for the appalling legislation but the rest of the information is factual.

 

[berlinonaut]

Nothing I've written is debatable

I'd say this statement is debatable. Apart from the fact that in forums basically everything is debatable, even facts. Including the question wether the facts are actually facts. That's one of the main reasons why forums exist and what causes the traffic in forums.
But as this debate would be completely off topic for the thread and could furthermore easily escalate w/o delivering any value to anyobody I neither see a point in this discussion nor am I willing to have it. That's why I wrote:

Barely anything I would agree with and lots I heavily disagree with. But no point in having this discussion and furthermore not at all relevant to this thread. We should agree to disagree.