Electric Bike Conversions

Jun 20, 2005
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Has anyone converted their bike?
There are rear or front drive motors or bottom bracket ones. Being street legal is important. I consider taking out liability insurance too.
Not surprisingly the batteries cost nearly as much as the motor and ancillaries. There are plenty of videos and info available.
I intend going for it but would love to hear from anyone who has done it. Plus any pit falls discovered on the way.
 
Mar 8, 2009
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We used to have 'summats' similar, I rode one of these in the 50;s (my dads), Replace 'mini motor' with electric motor and away you go. That's progress!
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Nov 11, 2009
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We used to have 'summats' similar, I rode one of these in the 50;s (my dads), Replace 'mini motor' with electric motor and away you go. That's progress!
View attachment 1343
My dad had one of those, then changed it for a Cyclemaster with engine in the wheel. At weekends he would take me on the back into Northamptonshire and all around the Peak District and other Midlands areas. Mum being at work.

769330FF-4AC6-47C3-B1D3-21B85B4C67C2.jpeg
 
Jun 20, 2005
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My dad had one of those, then changed it for a Cyclemaster with engine in the wheel. At weekends he would take me on the back into Northamptonshire and all around the Peak District and other Midlands areas. Mum being at work.

View attachment 1344
A teacher had one with the two stroke mounted on top of his front wheel. At 15 I did up a rusty old Raleigh Runabout.
 
Nov 16, 2015
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Dusty Dog, here is a photo of one of the bikes, a mate has built, it has a range of over 60 miles and top speed of about 35 mph. In Off road mode. .
I don't think that is quite what your after though.
sm_DSCN2653.JPG
 
Jun 20, 2005
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That’s similar to what I had in mind. Central bottom bracket motor. The battery is the expensive bit. Not seen a battery like his🤔🤔
 
Apr 20, 2009
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Is it a project you are after Dusty?

Why not consider one direct from shop, I have one but may be you want to keep cost down, I was informed the bottom bracket motors were better than the wheel mounted one's. Halfords at the time were only doing the wheel motors so I went to an independent supplier.
Similar to this one but a lesser model I wouldnt justify that price!!
 
Jun 20, 2005
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There are a number of off the shelf conversion kits available to fit onto an existing cycle.

https://electric-bike-conversions.co.uk/
Clive ,
the ones you quote are fine but are twice the price of most diy versions. The real cost is the battery. The cheap motors are axle driven . But according to the populous the best all rounder is a crank driven unit. That means you lose your front triple clangers!
 
Jun 20, 2005
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Kev
I want to convert my own bike just to increase the range because my knee is knackered. Not so much speed but a bit of assistance up the hills
 
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Mar 14, 2005
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Most of the replies so far cannot be classed in teh UK as a bicycle.

To be classed as an electric bike - Here's what GOV.UK says about them



"You can ride an electric bike if you're 14 or over, as long as it meets certain requirements. These electric bikesare known as 'electrically assisted pedal cycles' ( EAPCs ). You do not need a licence to ride one and it does not need to be registered, taxed or insured.
Electric bikes: licensing, tax and insurance


What counts as an EAPC
An EAPC must have pedals that can be used to propel it.
It must show either:

  • the power output
  • the manufacturer of the motor
It must also show either:
  • the battery's voltage
  • the maximum speed of the bike
Its electric motor:
  • must have a maximum power output of 250 watts
  • should not be able to propel the bike when it's travelling more than 15.5mph
An EAPC can have more than 2 wheels (for example, a tricycle).
Where you can ride
If a bike meets the EAPC requirements it's classed as a normal pedal bike. This means you can ride it on cycle paths and anywhere else pedal bikes are allowed."



If you have a powered bicycle that does not conform to the above, its classed as a moped, and must be taxed and insured, and of course you must wear a safety helmet.
 

JTQ

May 7, 2005
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Whilst, the UK Government's Webpage does state:_"
Its electric motor:
  • "must have a maximum power output of 250 watts"
That appears not to be the industries or converter's interpretation of the law on which it is based, the "norm" interpretation is the "maximum continuous power output is 250 Watts".
In itself a massive cop out in that really the maker can put whatever figure they want on the "continuous" rating labelling their kit can stand, and basically under any conditions. The outcome is many "legal" commercial bikes have motors that peak above 250 Watts, and I hazard a guess near every conversion kit.

EDIT: I have found the legislation relating to "continuous" HERE . chapter 1, Article 1 (h). Quoting, with my emphasis: -

(h) cycles with pedal assistance which are equipped with an auxiliary electric motor having a maximum continuous rated power of 0,25 kW, of which the output is progressively reduced and finally cut off as the vehicle reaches a speed of 25 km/h, or sooner, if the cyclist stops pedalling,

Now out of the EU we can do whatever we want to bring into UK law, however those penning the reference quoted by the Prof, wrote that in a sloppy fashion by missing out the critical word "continuous", that is in the legislation.
------------------------------------------------------------------------

I have "looked", though went proprietary, at doing a DIY conversion, particular issues I found needing attention are:-

With rear hub geared drives the shaft is a larger diameter, and the hub width is greater than "conventional". So the chain stays need splaying, and the dropouts need adequacy to be enlarged, not something aluminium frames readily accept. Plus then you can encounter drive line off set between the crank ring and rear sprocket.

With crank drives, again drive line off set can be challenging, here as the whole power goes through the chain, the issues of living with an out of line drive are increased.

As asides: -
Most DIY conversions will have a simple cadence based, as opposed to torque sensing or complex blending of the two, motor control system. The finesse of the control system being an area the major commercial brands invest heavily in to achieve the "character" of their products.
For hilly area use the crank drive motors have an advantage in not only the rider, but importantly the motor can benefit from a selective gearing system, hub motors typically whilst geared only have a unique ratio than needs to suit riding on the flat or climbing hills.
 
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Jun 20, 2005
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As I said in my OP being street legal is a mandatory consideration. The maximum speed of 25km/h is achieved electronically irrespective of the motor power. 750 watt max rating seems the most popular. Crank mounted only supplies power directly related to the physical pedal rotation. The batteries are interesting. Inside the pack are a number of small single cells , similar to an AA size linked. Samsung are the favourite. I guess this system is how EVs do,it. For me the EB is just to help on the hills and extend my cycling range. BTW ŵe always wear a helmet, madness not to!
 

JTQ

May 7, 2005
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As I said in my OP being street legal is a mandatory consideration. The maximum speed of 25km/h is achieved electronically irrespective of the motor power. 750 watt max rating seems the most popular.

If the motor is labelled as 750 Watts, it is not "street legal".
 
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Did they have a pedal moped called a Velosolex in the UK. I also seem to recall that in the fifities or earlier there was a manufacturer in the UK that also had a similar type of moped with pedals.
 
Jun 20, 2005
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I agree. But as pointed out the laws are somewhat ambiguous ie must have a max power output of 250 watts. But then I read the larger motors are restricted to this lower power out put for road use. It is then possible to buy a little “box” from the USA that removes the limiter!
The racing bike boys cruise at 20 mph all day. My desire is just a bit of help on the long drag hills. Not speed. I will look at the 250 watts again . But at the end of the day it is the battery which is more important for range and durability. Thanks to all for your thoughts so far.
 

JTQ

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The law is not ambiguous, it very clearly states :-

(h) cycles with pedal assistance which are equipped with an auxiliary electric motor having a maximum continuous rated power of 0,25 kW, of which the output is progressively reduced and finally cut off as the vehicle reaches a speed of 25 km/h, or sooner, if the cyclist stops pedalling,

The issue is that that wording opens the door for the motor to have any maximum rating the maker likes to give it, the only restriction being what "he" puts on the label as its "continuous" rating.
I assume the legislator did not consider how "devious" some makers might be to plicate the part of the market that wants grossly over powered pedal bikes?

Just ensure the motor maker's label, not some after market label, states nothing more than a 250 Watt continuous rating.
 
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Nov 6, 2005
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I agree. But as pointed out the laws are somewhat ambiguous ie must have a max power output of 250 watts. But then I read the larger motors are restricted to this lower power out put for road use. It is then possible to buy a little “box” from the USA that removes the limiter!
The racing bike boys cruise at 20 mph all day. My desire is just a bit of help on the long drag hills. Not speed. I will look at the 250 watts again . But at the end of the day it is the battery which is more important for range and durability. Thanks to all for your thoughts so far.
Isn't there, or maybe wasn't there, a regulation limiting the electric assistance to speeds up to 15mph - so that any faster had to be pure muscle power.
 
Nov 11, 2009
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Isn't there, or maybe wasn't there, a regulation limiting the electric assistance to speeds up to 15mph - so that any faster had to be pure muscle power.
Prof quoted it from the UK Gov site in his post above. No motor power above 15.5mph.
An alternative could be to insert servo motors into Dusty's new knee and a battery pack in his waist bag.
 
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That’s right chaps.15.5 mph max .Thereafter the motor must cut out. The ones I’ve been looking at only offer electric assistance when the pedals turn. No pedalling no power.I shall investigate the proprietary machines at the big bike stores. However their prices are hefty. A 250 watt central mounted unit with battery diy can be done for £600 or less. Three guesses where they come from 🤔🤔🤔
 

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