Cycling UK Forum

Nearholmer wrote: ↑16 Sep 2022, 4:03am Anyone have a copy of BS1727:1971 as amended up to 1978?

From what I can glean, that properly defines the meaning of “maximum continuous rated power” as used in the EAPC regulations.

I still have some limited access to the standards I used to work on. Unfortunately that doen't include other standards referred to by those standards. The latest UK/EU standard I've got is BSEN 15194:2009. That standard says:

The maximum continuous rated power shall be measured according to EN 60034-1 when the motor reaches its thermal equilibrium as specified by the manufacturer.

The latest EAPC standard of any kind that I have is ISO/TS4210-10:2020. That standard says the same with a bit more detail:

The maximum continuous rated power shall be measured at the driven wheel of the EAPC in accordance with IEC 60034-1 when the motor reaches its thermal equilibrium as specified by the manufacturer.

(Apparently IEC is where CEN gets its electrical standards.)

Both standards allow that the power can alternatively be measured at the output shaft of the motor, in which case the result is reduced by a factor of 1.1 to consider measurement uncertainty and 1.05 to include transmission losses, unless the real values of those losses can be determined. (So your 250W bike might actually have a 289W motor.)

And both standards apparently leave it to the motor manufacturer to decide what is the continuous rated output of the motor. So put yourself in the position of a motor manufacturer. You want to put the best spin (sic) on your product, so you'll rate it as powerful and efficient as you sensibly can. No point in rating it as a 750W motor if it takes 1.5kW to run it at that level, because even if it can dissipate 750W of heat okay, nobody wants to waste that much electricity. Sensibly you'll rate it towards the higher powered side of the efficiency peak. That's borne out by everything I've found so far in the general literature on DC motors. Such as this page about how to read performance curves, where under Rated Performance it says:

To find the rated or nominal operating performance of a motor / gear motor, the first step is to locate the peak efficiency point

I think some people may be suggesting that some manufacturers respond to the E-bike regulations by rating e-bike motors as 250W when they are not only capable of delivering a whole lot more power, but also more efficient whilst doing that! Were that motor to be marketed for any other purpose it would surely be rated at the higher and more efficient power. Maybe there's something in IEC 60034-1 that calls that out for the cheating it surely is. Or maybe not. We just don't know.

Maybe another requirement needs to be added to E-bike standard that: the motor shall not be capable of exceeding the continuous rated power output without some loss of efficiency.

Nearholmer wrote: ↑14 Sep 2022, 6:34pm As a word of warning, there are several different kinds of dc motor, with different characteristics. I think, but am by no means certain (it’s probably explicit in there somewhere if followed through to the data sheets), that the website link is dealing with permanent-magnet motors, and I think the low efficiencies are because the motors are quite small, and the gear-trains attached to them incorporate multiple stages of speed reduction, but again I’m not totally certain.

Admittedly Carlton Green's link to ISL Products is information from a supplier of small DC motors for low power applications. E-bike motors are clearly much larger with more torque and fewer rpm, especially when they're ungeared hub-motors, but are nevertheless the same species: permanent-magnet DC motors.

Here's an article about e-bike motors. The first graph, that I'll copy below (apart from the fact that it's plotted the other - more sensible - way around, with higher speed to the right) is the same general shape as that from ISL products.

I'm afraid this is more of an e-moped hub-motor, but it should come as no surprise that most of the stuff on the internet comes from Americans sharing ideas for re-invention of the motor-bike whilst pretending it's still some kind of pedal cycle! It's fair to say however, that this isn't really a 750W motor. That's the peak output power. From the first link you may have learnt that continuous rated output of a DC motor is defined at or near peak efficiency, about 28mph according to this graph, from which we can see that this is a 400W motor. Still something of a moped, but it'll do for illustrative purposes.

Ignore the thick red 'power requirement' line, that's just an estimate by the article's author as to how much power it might take to push a bicycle along a flat road subject to unknown assumptions about tyres, frontal area etc. Your mileage may vary! Look instead at the thin, dark red line for input electrical power: see how it increases dramatically as the speed of this wheel-hub-motor is reduced, by a hill for example. At its peak output this motor consumes a massive 1.5kW, with half of that going into heating up its windings! No motor will stand that for long before it's literally toast! Consequently, DC hub-motors cannot simply be connected to a battery and let loose on the road, for fear that the rider will attempt an awful long and steep hill that burns it out. (Some early e-bikes were nevertheless made like that, I tested and toasted one in no more hilly a place than little-old Guildford!) So they're connected via a controller that stops the current exceeding a certain level, at which the motor should not overheat provided the weather isn't too hot already and the hill isn't too long.

It's a pity the author didn't add a line for torque to that graph, but if you've read the other link you'll know that current increases as speed decreases, in proportion to the demand for more torque. The battery voltage is constant, so input power is proportional to current and the dark red line is a good-enough proxy for torque. It follows that limiting input power/current also limits output torque to the corresponding level, so if that hill gets even steeper you'll be hoping the controller also has a walk-assist mode!

Here's a link to another American mopedist's article that shows how limiting current affects the torque of actual hub-motors. I apologise for the title and tone of that article, which is clearly a dig at how the EU limits motor power by specifying a continuous rated output. You now know that is NOT a futile exercise. It's defined as that power when the motor is most efficient, and whilst the motor may supply more power than that sometimes, that'll only be a bit more power and only when the bike is going relatively slowly. Okay if you hook up a higher voltage battery the motor will produce more speed and power, but the EU standard is for a complete bike, a defined package of motor, battery and controller. Anyway, the article has a lot of interesting graphs. You can take it as read that a 250W motor will have similar curves, but on different, more human scale.

Bonzo Banana wrote: ↑12 Sep 2022, 8:48amI don't think you understand mid-drive motors, the torque figure they give is at the crank, so if they say 95Nm maximum torque that is what is delivered at the bottom bracket.

Where's your proof? I've been all over Bosch's website looking for where it says that, but it doesn't. BB-drives are supplied to bike manufacturers for use with a gearing system for which Bosch specifies the parameters - or else it would be possible to use the motor at illegally high speeds.

So until proven otherwise, I will continue to believe that when the specification of a bike - like this Focus Jarifa - says Bosch Performance CX Smart, 85 Nm, 250 W, they mean that's what you get at the wheel, not the BB.

Bonzo Banana wrote: ↑12 Sep 2022, 8:48amIf you have 1:1 gearing then allowing for a small power loss through the chain of lets say 2-3Nm you would have 92Nm if both the front chainring and rear cog were 32T lets say. Higher gearing on the bike allows lower torque and higher speed.

You may know something about motors but when it comes to gears I'm your grandmother, okay? The example you provide conveniently gives the same torque (near enough) at the BB and wheel. But the 1-by transmissions of e-bikes generally do better than that, in the case of the Focus Jarifa MUCH better. Its bottom gear is 36/51, which (ignoring transmission losses which we both know are very small for chain drives with large sprockets) would convert 85Nm at the BB into a massive 120Nm at the wheel!

Here's a nice little formula I worked out earlier, that tells how steep a hill you can get up with an e-bike on motor torque alone, no significant rider input. (The mysterious '803' is what comes out of combining the conversion factors from inches diameter to metres radius, kg to Newtons and fractions to percentages.) I'll write it big since people might find it generally useful.

Gradient (percentage) = 803 × Torque (Nm) / Wheelsize (inches) × Total Weight (kg)

The Focus Jarifa has 29in wheels in my size and weighs 24.5kg. I weigh 70kg so with clothing etc lets call that 100kg. With 85Nm at the wheel that means I could ascend a 24% (almost 1:4) gradient without actually pushing the pedals; which sounds reasonable, with a bit of actual pedalling one should get up just about anything. With 120Nm at the wheel however, I'd ascend 33% (1:3) hills just as effortlessly. From what I've seen of high performance Bosch-drive e-bikes, on our local Peak District hills, users DO need also to pedal quite hard to ride anything THAT steep!

So there's another reason I'm sticking to my supposition that when Bosch qoutes a maximum torque, they mean that's the most you'll get at the wheel with the kind of gearing they expect the bike manufacturer to fit. And why would they claim any less?

Bonzo Banana wrote: ↑12 Sep 2022, 8:48amThere is no free power the reason mid-drives deliver more power at the crank is because of the small high rpm motor going through cogs and sometimes belts to achieve that. The real benefit mid-drives have if they have both the controller board and motor housed in one unit so they can create a very high current pathway between the two which is more difficult with hub motors and the controller board converts higher voltage to lower voltage with more current to drive the motor more strongly at lower speed. You don't get anything for free though mid-drive motors still draw very high currents from their battery to achieve their very high torque figures.

I'm afraid you seem to be confusing power with torque. Mid-drives deliver more TORQUE at the crank than simple hub-drives deliver at the wheel, because most of the time the rider will be in a much higher gear than bottom, in which the crank turns less than half as often as the wheel. True, they utilise smaller motors that spin faster and are geared down to crank rpm, so what? The losses and mass of gearing are fully offset by the greater efficiency and lighter weight of such motors. I don't buy your theory that hub drives are penalised by the length of cable. What penalises hub motors is their lack of gearing, that makes them less efficient at low speed and ultimately less effective for hill-climbing. I should like to see a hub motor combined with automatically shifted internal gears (a simple three-speed epicyclic would do, if wide-enough ratio). Such a unit could have the advantages of both systems.

Bonzo Banana wrote: ↑12 Sep 2022, 8:48amThis video should help you understand the eu legislation with regard wattage and how its completely ignored by the major players. I've used this video as the person who presents it is a major author of ebike books and literature. Surely there is no debate here its very simple to understand that even allowing for peak figures close to 800W is a long way from 250W.

I don't need a video to help me understand the EU Standard that I helped to write! But thanks for the video. It shows very well that we got it right. The EU legislation results in e-bikes that behave pretty much the same as average bicycles, as ridden by most people, in countries where most people DO ride bicycles - except uphill, where e-bikes are significantly faster. It also shows that American legislation, on the other hand, results in e-bikes that for no effort reach speeds attainable only by sport cycling enthusiasts using super-lightweight bicycles. The presenter as good as admits that American e-bikes really are electric mopeds. Americans argue that e-bikes need this level of speed in order to mix safely enough with traffic on America's cycle-un-friendly roads. Be that as it may, when speed comes that easy it gets used more carelessly than when it comes only in response to hard pedalling. Result: bikepaths and trails all over the USA are being closed to e-bikes.

What IS the debate here? It's about whether a motor of rated output 250W is enough for modest speed up steep hills. Clearly it is, so long as it has the benefit of gearing, in order that it may perform as efficiently at low speed, as it does at its rated speed. I readily accept that a DC motor with a rated output of 250W, may output more than 250W when it turns more slowly than its rated speed. Because I have studies the performance curves of DC motors (that are very different from AC motors by the way). That is how I know the implication that mid-drives are cheating by outputting 800W must be nonsense. I think someone is confusing output power with the figures for electrical INPUT power consumption displayed by the consoles of some e-bike controllers.

ChrisF wrote: ↑22 Aug 2022, 9:47pm I've decided to go without the front panniers. I didn't have much weight in them (less than 8kg between them including the bags themselves), they look bulky in the photo but it's all light stuff.
I've now added a small handlebar bag, which when empty weighs 1kg less than the low-rider rack and two empty panniers.

Good idea. For me also front panniers are an 'if needs must' addition, but I never tour without a handlebar bag - with shoulder strap and on a quick-release bracket. That bag has my camera and other valuables in it and always comes with me when I park the bike - even if I'm not going far from it.

Another criticism of bike-packing setups is that the bags all attach with too many straps to facilitate taking valuables with you when leaving the bike. It's a packing philosophy that probably best suits those who just ride, eat and sleep, who seldom stop en-route and who avoid populated places.

Bmblbzzz wrote: ↑21 Aug 2022, 5:37pm

CJ wrote: ↑17 Aug 2022, 9:04pm Jack the Rack is another of those bits of bikepacking nonsense that pop a small amount of cargo into or onto something that weighs quite enough already empty! This one's 700g without any bag to put stuff in. Add that and the cargo/container weight ratio will barely be 5:1. Regular carriers with panniers are typically 10:1.

Well I'm sure that's possible... but my Carradice Super C's weigh about 2kg (I think 2.2kg is the official figure) and though I'm sure they could hold 22kg and I probably have carried that much in them on occasion, I'd not want to tour with that weight. So it's a theoretical capacity rather than totally usable. That said, I do realize they are some of the heaviest panniers (I think Ortliebs are a similar weight but many brands are lighter) and would agree that generally, "bikepacking" luggage has low cargo:container and high price:cargo. And maybe that's why bikepacking's gift to all cyclists is the "revolutionary" TLS packing system!

Tubus Fly carrier (420g) and a pair of Ortlieb Frontroller+ panniers (1440g) total 1.8kg (after discarding surplus screws and unnecessary shoulder straps) and provide a most reliable, 100% waterproof luggage solution with 18kg and 25 litre capacity. QED. And lighter is possible if you have the money. Heavier is also possible by making worse choices. Or you can have just as light for less money by sacrificing durability and waterproofness. I use front panniers in this example because if you're using the 'TLS' system, that's all you'll need. But if that's not enough, you now have a handy carrier top to strap that bundle of extra 'S' you left at home then had to buy en-route, when the weather turned out worse than expected!

Regular panniers, ie those sold as 'rear', have an even better cargo/container ratio due to the economies of scale. Swap frontrollers for bigger, simpler, cheaper backroller city bags and another 80g makes space for 15 more litres! Put these on a Tortec Velocity alloy carrier, weighing 560g and nevertheless claiming the usual 25kg capacity, and you have a very capacious system costing only £108 from Tredz with a 12:1 cargo/container weight ratio. So I think 10:1 is really quite easy to achieve.

Bonzo Banana wrote: ↑20 Aug 2022, 12:59pm ...something like a Bosch mid-drive motor despite its 250W rating could have more sustained peak as high as 800W.

"Could have" you say, but does it? What's your source? And why would the manufacturer of a mid-drive unit let it draw that much extra current, risking over-heating the motor and draining the battery, when he can rely on the gearing of the bike to amplify the torque as necessary for hill-climbing whilst keeping the motor spinning at a more efficient rpm?

Bonzo Banana wrote: ↑20 Aug 2022, 12:59pm However the point is a 250W direct drive motor will probably only have torque of about 30Nm peak compared to something like 90-100Nm for mid-drive.

Can we assume that here you are comparing the stalling torque of an ungeared hub-motor system, with that produced at the rear hub by a mid-mounted motor when bottom gear is engaged? So that would be due to more sophisticated gearing, rather than a greater excess of power.

Bonzo Banana wrote: ↑20 Aug 2022, 12:59pmIf you take the view that peak current should be no more than twice the nominal rating of the motor i.e. 250W so 500W then just about every mid-drive e-mountain bike would be in the crusher as illegal.

Proof?

ChrisF wrote: ↑21 Aug 2022, 1:39pm There wasn't any wobble or anything, it all felt very stable, just hard work turning the bars.
The Mercury has drop bars, which are of course narrower than straight ones - perhaps that's part of the problem.
20220819_102500.jpg

Stable but heavy steering is how it is. The low-load concept puts the combined C of G of the panniers on or very near the steering axis, so they have a neutral effect on the steering geometry (whereas the up-in-front CG of 'normal' front panniers pulls the steering the same way as you lean) but the fact that each individual pannier's mass is some distance away from that axis nevertheless adds a lot of turning inertia to the system. It gets more like steering the heavy front wheel and fork of a motorbike than a bicycle. It still steers okay, but requires more forethought, you need to plan your line around a corner and can't just flick the tyre around a stone anymore. If it's any consolation, up-front panniers add just as much inertia too, and then try to sharpen the curve you'd planned through the corner!

From your photo, those front panniers look just as big as the rear. I recommend much smaller ones in front and see that the specification of your carrier says no more than 14kg total. I'd not want to put more than 10kg on it. The fork-end brackets look a bit weedy and for alloy tube it doen't look very fat. I'd also like a closer look at how that front loop is attached to the side-frames. The best designs continue the front loop down to the fork-end attachments. One of the nasty failures I've seen was another that didn't, but simply attached it to the top front corners of the side frames. Like yours, it was attached in two places each side, which should impart some bending stiffness, but evidently not enough.

hoogerbooger wrote: ↑18 Aug 2022, 4:33pm {picture of Raleigh catalogue}
So do I get an apology ? or do I need to sue Raleigh ?

I think you'll find a line in Raleigh's catalogue something along the lines of "We reserve the right to tweak the specification, to deal with supply problems etc". In this case they probably got complaints about how the abovementioned plate makes Blackburn's original low-loaders look ugly and difficult to fit quite a lot of panniers onto, both of which are fair comment. The substitute was probably cheaper, looks neat and fits most everything. Just maybe it's not quite as tough.

Cowsham wrote: ↑17 Aug 2022, 6:49pm There's no way on God's green earth you'll find me spending 60 quid on a handlebar rack. £90 is utter madness.

I'm right with you there!

Jack the Rack is another of those bits of bikepacking nonsense that pop a small amount of cargo into or onto something that weighs quite enough already empty! This one's 700g without any bag to put stuff in. Add that and the cargo/container weight ratio will barely be 5:1. Regular carriers with panniers are typically 10:1.

Cowsham wrote: ↑24 Jul 2022, 11:08pm I used this recently -- cheap and effective

https://www.ebay.co.uk/itm/144352016031 ... media=MORE

I needed it to fit suspension forks with no mudguard, caliper or pannier fixing points.

I used pipe clamps to fix to the lower fork my bike has disc brakes. This method worked very well.

Pipe clamps for a front rack...?

Yeugh-h-h-h-h

And on a suspension fork, where the rack is unsuspended mass so gets shaken even worse than on a non-suspension fork (that forces the tyre to do all the suspending)...?

I'd say you were very lucky.

hoogerbooger wrote: ↑23 Jul 2022, 6:37pm As an illustration, even with non-flapping bags/items on the front:
P3270122.JPG
My Blackburn alloy low riders failed in Tibet, shaken to death on bumpy roads...

hoogerbooger wrote: ↑23 Jul 2022, 6:37pm As further illustration, I have previously posted the bodge I ended up with to get me to Katmandu:
P4100021.JPG

That's not a Blackburn low rider. I can't be certain what brand it is, but I had one like it (may still have it in storage) with those distinctive brackets (that Blackburn never had anything like) crimped onto the top rail. The rear rack in your first picture looks like a Tortec Expedition, (NOT a great design, lacking the structural triangulation of the legs that made Blackburn so much better than anything before) so maybe the front is an old Tortec model.

ANTONISH wrote: ↑30 Oct 2017, 8:26am When I go on a club run there are many and various inflators available but my frame fit Zefal HPX pump is always in demand.

Likewise my Topeak Road Morph with gauge: easy pumping to a full and certain pressure. It fits instead of a bottle cage. Not sure if Topeak also do a below/beside-cage mount. As my carbon road/gravel/touring bike has three sets of bottle mounts, I don't need that.

For those who knew Doreen Leheup of Nottingham:
https://www.cyclinguk.org/article/doree ... -1926-2022 (obituary by her daughter Helen Juden on CUK website)

In addition to which, she was the best mother-in-law one could wish for!

SA_SA_SA wrote: ↑21 Jul 2022, 11:59am

CJ wrote: ↑20 Jul 2022, 12:31pm Put luggage on the front if you must, but be very careful how you do it ........ So think twice before simply strapping stuff onto your forks .....
...
Even purpose-made front luggage carriers are not necessarily safe. In my 31 years as CTC Technical Officer and private work as an expert witness I've seen the unfortunate results of some very inadequate designs...

Does this mean that low rider designs that are based on an old fashioned 3 (+n) point front carrier style, such as the new?ish? tubus expedition ( https://www.tubus.com/en/products/front ... tion-front ) and others are a better bet for easy proper fitting: I always wondered why this wasnt done in the past, as surely such designs are easier to fit on bikes without mid fork eyelets?

I wouldn't let speculation about how idiot-proof the attachment may be, put me off a thing that's safe when attached properly. Because I'd attach it myself and do not believe myself to be an idiot! Unfortunately that applies also to some who are idiots. And a few of them apparently work in bike shops! That being so, I think low-load front carriers where the two panels are joined to one another are more idiot-proof than the totally separate 'custom' design. And those where the joining together is permanent even more so.

When considering the number and locations of attachment points, the further apart they are in at least two-dimensions, the better. A good criterion would be the surface area of the shape made by linking those points. So a bottle cage, two points in a straight line, is not good and hardly improved by adding a third in line. A line has no area at all, so the fitting has very little resistance to rotation about that line, which has a strong tendency to loosen the screws. Now consider a single panel of a custom low-rider: three points with only the width of a fork blade separating two of them. The area is a very thin triangle: better than a line but not by much. The two mid-fork attachments will experience large shear forces in response to any shaking of the load and such to and fro forces tend to turn the heads of screws in a loosening direction unless they are very tight indeed. Revert to the classic low-rider with hoop over the wheel and now you have four widely-spaced points making a nice big rectangle. The safetly of that design depends very much upon the bending stiffness of the hoop and its attachment to the side panels. Designs where the hoop merely joins the top-front corners of the panels are at least slightly dodgy in my book. Vetta made one like that which once spectacularly stopped a tandem! Better that the hoop continue down to the fork-ends I reckon. Add a whole front carrier structure above the side panels and of course you have a fifth attachment and a very stiff joining together, but at what cost in extra weight? As for the old-fashioned above-wheel front carrier, three points in a triangle is pretty good and it's an easy structure to stiffen with bracing struts here and there, but do you really want all that weight out front and pulling your steering around? There are certainly a lot of factors to consider.

Put luggage on the front if you must, but be very careful how you do it, as anything that can become caught in a front wheel is liable to stop it going round. You would be amazed at how much damage can be done to the front of a bicycle - not to mention it's rider - by something as innocuous as a towel in a plastic bag! So think twice before simply strapping stuff onto your forks and think again after giving it a darned good shake and a few really strong pulls this way and that toward the wheel. Then ask yourself one question: Do I feel lucky?

Even purpose-made front luggage carriers are not necessarily safe. In my 31 years as CTC Technical Officer and private work as an expert witness I've seen the unfortunate results of some very inadequate designs (there still is no techincal standard for front carriers - only rear - so it's up to every designer to make their own more-or-less educated guesses) and wrong fitment of sound designs - by supposedy qualified bikeshop mechanics no less! Some of the riders suffered life-changing injuries. So I would not put any front rack on any bike of mine or my loved ones, that comes from a manufacturer with anything less than an excellent record for similar products. And I would not let any person fit it without long experience of not only cycle mechanics but also cycle touring.

Some of the recent 'bikepacking' solutions look well dodgy to me. But as CTC no longer has anyone collecting and analysing feedback from touring cyclists, about what equipment works for them and what doesn't, it's unlikely we'll ever really know.