What happens above 15.5mph?

Electrically assisted bikes, trikes, etc.
Geoff.D
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What happens above 15.5mph?

Postby Geoff.D » 23 Aug 2017, 5:00pm

I have little knowledge of electric motors, but I've been enjoying the thread about conversions.

Looking at websites I keep coming across suppliers saying "If you ride above 15.5mph then a motor is not for you", or words to that effect. This puzzles me somewhat. I could more easily understand "If you can't ride above 15.5 then a motor is for you....."

In the main, along flat roads, I footle along at 12-14mph on my bike, and 11-13mph on the trike, both being recumbents. But as soon as the gradient starts going downhill, my speed increases easily and 20+ isn't difficult on slight slopes. At 6% downhill I'm freewheeling at 30mph, and steeper than that I get adrenalin rushes right up to 50+.

I'm interested in a conversion (even to an upright hack) in order to do my regular trips into town to shop; visit the health centre; socialise; etc. without having to overcome the two 15% climbs and arriving there all sweaty and dishevelled. But I'm loathe to lose the ability to cycle above 15.5mph, or enjoy the adrenalin rushes on the downslopes. I'm approaching three score years and ten....and I want to maintain as much excitement as I can !!

Can someone explain what effect the 15.5mph limit has on the bike's ability to move above that speed? Can the motor be divorced from the normal drive, so that the only hindrance is the added weight? What happens to the drive (or resistance to pedalling input) when the battery is discharged? What else should I be asking, and would be useful to know?

Toffee
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Re: What happens above 15.5mph?

Postby Toffee » 23 Aug 2017, 5:18pm

The 15.5 mph is the limit to which the motor is allowed to power the bike. If you are able to pedal faster or coast downhill then that's ok.

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Dean
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Re: What happens above 15.5mph?

Postby Dean » 23 Aug 2017, 5:40pm

You travel back to 1985.

Geoff.D
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Re: What happens above 15.5mph?

Postby Geoff.D » 23 Aug 2017, 7:07pm

Toffee wrote:The 15.5 mph is the limit to which the motor is allowed to power the bike. If you are able to pedal faster or coast downhill then that's ok.


Toffee, are you saying that above 15.5mph the bike behaves just as it would without the motor, apart from the added weight?
Or does the motor cut out, leaving a drag? In asking this I'm thinking of an internal combustion engine. If I throttle back to zero, or switch it off completely, the engine is a drag to forward motion, unless it's disconnected from the wheels (i.e. out of gear, or the clutch is released).



Dean wrote:You travel back to 1985.

:D If only!

Bonefishblues
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Re: What happens above 15.5mph?

Postby Bonefishblues » 23 Aug 2017, 7:11pm

Dean wrote:You travel back to 1985.

...and indeed tish.

hercule
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Re: What happens above 15.5mph?

Postby hercule » 23 Aug 2017, 7:38pm

The motor (crank drive) on the Kalkhoff I have in custody (see, I'm not admitting to owning an ebike :lol: ) just gradually fades out at the top end of its assistance. You can of course pedal on and go faster without assistance, but on the higher power levels it feels as though you're on a tandem and the stoker has just taken her feet of the pedals ... no particular stokers in mind, of course!

Where I particularly notice the cutoff is coming down a slight gradient at maybe 20mph, the road flattens out a bit and you put in more effort to maintain the same speed. Then you suddenly feel that you're pedalling something of considerable mass - I miss the lively response of a lightweight nonpowered machine. Of course the Kalkhoff is a sturdy utility bike, it might not be such an issue on a lighter machine.

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meic
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Re: What happens above 15.5mph?

Postby meic » 23 Aug 2017, 10:54pm

One person with a hub motor does claim that there is noticeable drag from the motor at higher speeds, just noticeable not major. It seems to more than cancel out the extra weight as my none motorised bikes general descend a little bit faster than the electric motored bikes who I ride with.
Yma o Hyd

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squeaker
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Re: What happens above 15.5mph?

Postby squeaker » 24 Aug 2017, 10:00am

From the little I've read (and I'd appreciate more reliable info.!), I get the impression that some systems eg geared hubs freewheel better than others eg some direct drive hubs, as the former incorporate a freewheel. The assist should taper off, rather than hit a brick wall, but again systems may differ, in the same way that they start providing assistance.
I suggest you ask the relevant questions to the supplier about any particular system that you are interested in.

PS: of the two bikes I've tried, one was rather abrupt in its assist, especially starting off, the other pretty much seamless, other than the speed that the old legs were propelling me up the hill in question (not expected on a rather upright 'dutch' style roadster)!
"42"

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[XAP]Bob
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Re: What happens above 15.5mph?

Postby [XAP]Bob » 25 Aug 2017, 12:35pm

There are a couple of possibilities... the most common is that there is a freewheel in place, so the motor (gradually) stops providing assistance, and then you are left with an additional freewheel.

However if your device offers regenerative braking - it will need to have some power delivered to the motor to prevent it from applying a driving force (in either direction)


On mine I have a motor that freewheels above 15mph - so it's added weight all the time, but a power boost when I am travelling relatively slowly (like uphill) - for the vast majority of the time on my commute the motor does me no good whatsoever. Make it snowy and I suspect that that will change significantly though...
A shortcut has to be a challenge, otherwise it would just be the way. No situation is so dire that panic cannot make it worse.
There are two kinds of people in this world: those can extrapolate from incomplete data.

Geoff.D
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Re: What happens above 15.5mph?

Postby Geoff.D » 25 Aug 2017, 6:14pm

Thank you hercule, meic, squeaker and Bob. Real life experiences are very useful, and the info interesting. Obviously I need to find myself in a place that has a dealer, and blag a test ride.

[XAP]Bob wrote:On mine I have a motor that freewheels above 15mph - so it's added weight all the time, but a power boost when I am travelling relatively slowly (like uphill) - for the vast majority of the time on my commute the motor does me no good whatsoever. Make it snowy and I suspect that that will change significantly though...


Bob, I can imagine that one difference in commuting with electric assist is arriving less dishevelled. But, given that you typically ride above 15.5mph, what is the overall saving in time? I guess this depends on traffic, road conditions, etc, but have you come to a conclusion in overall terms?

Phil Fouracre
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Re: What happens above 15.5mph?

Postby Phil Fouracre » 27 Aug 2017, 2:31pm

Everyone seems to be making this more complicated than necessary! Nothing happens, motor legally has to assist at no more than this speed, after that you just have a heavier bike to shove along! I've fitted four kits on tourers and mtbs, no problems whatsoever - they were all ungeared and brushless, claimed to have minimal drag when unpowered, which I'd agree with.
Never attribute to malice that which is adequately explained by stupidity

Geoff.D
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Re: What happens above 15.5mph?

Postby Geoff.D » 27 Aug 2017, 8:46pm

Phil Fouracre wrote:Everyone seems to be making this more complicated than necessary! Nothing happens, motor legally has to assist at no more than this speed, after that you just have a heavier bike to shove along! I've fitted four kits on tourers and mtbs, no problems whatsoever - they were all ungeared and brushless, claimed to have minimal drag when unpowered, which I'd agree with.


Nice, Phil. Thanks. :)

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[XAP]Bob
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Re: What happens above 15.5mph?

Postby [XAP]Bob » 29 Aug 2017, 10:29am

Geoff.D wrote:Thank you hercule, meic, squeaker and Bob. Real life experiences are very useful, and the info interesting. Obviously I need to find myself in a place that has a dealer, and blag a test ride.

[XAP]Bob wrote:On mine I have a motor that freewheels above 15mph - so it's added weight all the time, but a power boost when I am travelling relatively slowly (like uphill) - for the vast majority of the time on my commute the motor does me no good whatsoever. Make it snowy and I suspect that that will change significantly though...


Bob, I can imagine that one difference in commuting with electric assist is arriving less dishevelled. But, given that you typically ride above 15.5mph, what is the overall saving in time? I guess this depends on traffic, road conditions, etc, but have you come to a conclusion in overall terms?


I am faster on the non assisted raptobike than my fully commuting set up trike... But that's not a sensible comparison (Raptobike is a different beast entirely and is not set up as an all weather transport device).

The thing I can say is that if I get the day badly wrong (which I have done once) then the motor is an absolute godsend. I bonked a little over halfway home (had been tired already) and the motor allowed me to get home in a sensible timescale.

In terms of 'overall saving' I don't know - but there will be a bit (not only does it mean I am significantly faster uphill (and therefore spend less time at this 'less reduced' speed) but I am also slightly fresher for the flats...
I still arrive at work needing a shower - but in 45 minutes that's not a surprise (40 on the raptobike)
A shortcut has to be a challenge, otherwise it would just be the way. No situation is so dire that panic cannot make it worse.
There are two kinds of people in this world: those can extrapolate from incomplete data.

irc
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Re: What happens above 15.5mph?

Postby irc » 30 Aug 2017, 12:22am

A bit of thread drift here but why 15.5mph? EU law being the obvious answer. While many unfit cyclists or cyclists with some sort of disability will benefit from E-bikes the cost/benefit ratio is less clear cut for most cyclists. Downhill or on the flat we would be doing 15mph or not much less anyway.

A boost that cut out at 20mph? Now that would be worth having. As it happens I've just test ridden one. On tour in California I came across a Trek event in Santa Cruz where they were doing test rides of their E-bike range. There were two classes - 250W power and 20mph cutout and 350W power and 28mph cutout. Both road legal in the USA.

I tried out a hybrid style bike with 250W and 20mph cutout. A bit like magic. Going up a slight hill against a moderate breeze at 19mph. Power came in very smoothly and predictably.

If a 20mph E-bike was available in the UK I'd consider one as an option as I'd be getting a boost in speed for most of a commute rather than small parts of it. Any chance of a UK law change post Brexit? Probably not.

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willcee
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Re: What happens above 15.5mph?

Postby willcee » 30 Aug 2017, 6:19pm

Yesterday I had a call from a young friend,a teck guy that used to be cyteck go to guy locally with Halfords, he was amidst a trike coversion of a Kalkhoff E machine,I called on him at his home workshop to see the beast..It belongs to a chap in his mid forties who had health issues recently, and was losing his balance, he hoped temporaraily.. in fact crashed the ebike some weeks ago without bike damage but his ribs suffered!!.. I asked what the dongle on the rear chainstay was for, ''thats an override dongle thingymabob which fools the speed cutout of the motor , this dude goes out on this dutch style KalK with the fast clubmen in a local club and hangs on at the back like a terrier to a bone'' ..those guys would be coming in with a 23 mph average!!! and no way would I who has worked and ridden on that type of ebike want to hustle 30kgs on bendy country byways..so with common sense and a bit of internet scouring you can get more than 15.5 mph for more normal type cycling and no one need know if you take care..I'll get a pic up of the completed trike when its sorted... will