Brompton Electric Conversion Advice please

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Steve O'C
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Brompton Electric Conversion Advice please

Postby Steve O'C » 24 Mar 2019, 4:46pm

Friend of mine came round today on his Bromptom that he has converted to an Ebike by adding this front wheel.
IMG_20190324_142737965.jpg

Was slightly surprised to see that it was radially spoked. Is this OK?

rualexander
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Re: Brompton Electric Conversion Advice please

Postby rualexander » 24 Mar 2019, 7:18pm

Radial spoking is fairly standard on normal Brompton front wheels I think.

Steve O'C
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Re: Brompton Electric Conversion Advice please

Postby Steve O'C » 24 Mar 2019, 7:44pm

Radial spoking is fairly standard on normal Brompton front wheels I think.


Sure, but my concern was to do with the transmission of the torque from the motor to the rim via radial spokes.

rualexander
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Re: Brompton Electric Conversion Advice please

Postby rualexander » 24 Mar 2019, 8:39pm

Fair point, but Brompton Electric also seems to have radial spoking, https://www.google.com/search?q=brompto ... D_8gjpjd7M

Brucey
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Re: Brompton Electric Conversion Advice please

Postby Brucey » 24 Mar 2019, 8:44pm

the torque isn't that high (like brake torque is) and it isn't 'pulsy' (like pedalling torque is) so it is probably going to be OK. It might be better to build even x1 but if this makes the spokes go into the rim at a funny angle it is a question of choosing the lesser of two evils.

BTW I thought the whole point of a folding bike was that you could carry it. Most e-bike conversions near enough double the weight, don't they?

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

Steve O'C
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Re: Brompton Electric Conversion Advice please

Postby Steve O'C » 24 Mar 2019, 9:10pm

Thanks for the reassurance. You are right the bike isn't light. His previous Ebike was stolen from outside his flat so he wanted something that he could bring inside at night.
Steve

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RickH
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Re: Brompton Electric Conversion Advice please

Postby RickH » 24 Mar 2019, 10:03pm

Brucey wrote:BTW I thought the whole point of a folding bike was that you could carry it. Most e-bike conversions near enough double the weight, don't they?

I think the official Brompton kit is quite neat with the battery in the front bag. That means you can even up the load by carrying the battery/bag on the other side.

nez
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Re: Brompton Electric Conversion Advice please

Postby nez » 24 Mar 2019, 10:07pm

Brucey wrote:the torque isn't that high (like brake torque is) and it isn't 'pulsy' (like pedalling torque is) so it is probably going to be OK. It might be better to build even x1 but if this makes the spokes go into the rim at a funny angle it is a question of choosing the lesser of two evils.

BTW I thought the whole point of a folding bike was that you could carry it. Most e-bike conversions near enough double the weight, don't they?

cheers

No the real point of a folding bike is the folding - on trains, in the boot of the car, under your desk, in the forepeak of a boat. They're not much fun to carry. I write as someone who has owned a brompton for more than 20 years

pwa
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Re: Brompton Electric Conversion Advice please

Postby pwa » 25 Mar 2019, 5:46am

It depends what you are doing with the bike. If you intend lugging it around the Tube the additional weight would be a real burden, but if the bike only gets lifted off the ground at home it could be okay. While they aren't heavy for what they are, even a standard, non-electric Brompton is not easy to carry far.

Brucey
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Re: Brompton Electric Conversion Advice please

Postby Brucey » 25 Mar 2019, 9:52am

the folding action of a folding bike is a given; that is why they are, er, called 'folding bikes'.

Arguably there is no point in a bike folding if you can't then carry/lift the thing, even a short distance; only rarely can it be wheeled (eg half-folded) to where it needs to be.

Most folk carry at least 15lbs of 'stuff' when they are commuting etc, which means that once they are asked to lift a folding electric bike too they are toting the thick end of 60lbs total. Lots of people can't (or won't willingly) manage that in one go and would need to make multiple journeys up and down stairs etc.

Personally I'd choose to pedal a bit harder (i.e. not have the electric assistance) if there was much lift/carry at either end; after all the point is to make life easier, isn't it?

FWIW a (legal) conversion would enable you to manage ~15mph average speed (less if there are lots of traffic lights). IIRC a similar amount of effort to (say) walking enables a cyclist to travel on a flat road at about 12mph. Even if you ride for several miles each way, or it is really quite hilly, you would be hard-pushed to be more than five minutes slower by pedalling yourself and you don't then have an electric boat anchor to lug about at each end, or the faff of keeping it charged up, etc.

BTW I have a idea that electric bike conversions appeal to a certain type of person who finds cycling 'hard work' because they don't know how to use the gears properly and/or do the most basic maintenance. Hence some e-bikes are sold with no variable gearing ( that kind of user wouldn't use it anyway) and they appeal to folk who would otherwise be riding bikes with tyres that are half-flat, chains that are rusty, brakes that rub etc; these things are no longer a concern to them because the electric motor takes the brunt instead....

cheers
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S2L
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Re: Brompton Electric Conversion Advice please

Postby S2L » 25 Mar 2019, 10:46am

The wheels of a Brompton are massively overbuilt... given the size, they could be OK with 16 spokes, but they have 28. I don't think radial lacing in this case will be an issue at all

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Gattonero
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Re: Brompton Electric Conversion Advice please

Postby Gattonero » 26 Mar 2019, 10:55pm

S2L wrote:The wheels of a Brompton are massively overbuilt... given the size, they could be OK with 16 spokes, but they have 28. I don't think radial lacing in this case will be an issue at all


No, they are just built right as standard.
The problem with the motor is due to the large flange, you have to choose the less of the two devils, and crossing such a short spoke would be really bad in many ways.
It is by riding a bicycle that you learn the contours of a country best,
since you have to sweat up the hills and coast down them.
Thus you remember them as they actually are...

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Gattonero
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Re: Brompton Electric Conversion Advice please

Postby Gattonero » 26 Mar 2019, 10:56pm

Steve O'C wrote:Friend of mine came round today on his Bromptom that he has converted to an Ebike by adding this front wheel.
IMG_20190324_142737965.jpg
Was slightly surprised to see that it was radially spoked. Is this OK?


If you observe the original Brompton Electric, the forks have been noticeably beefed up, even if the motor is "only" 250w (I think) there is a fair amount of torque going on there. The standard dropouts and axle size are way insufficient in the long term for the use of a motor.
It is by riding a bicycle that you learn the contours of a country best,
since you have to sweat up the hills and coast down them.
Thus you remember them as they actually are...

Greenbuilder
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Re: Brompton Electric Conversion Advice please

Postby Greenbuilder » 27 Mar 2019, 8:15am

I've converted a couple of Bromptons to electric for friends. Both using Nano motor kits.
The radial spoking works fine, the rims look very strong.
The battery on the newer kit was a 4aH Bosch, like that from a large Sds drill. It fits in an adapter in the front bag. Carrying the the folded bike in one hand and the bag in the other is quite manageable.
They are probably the best folding electric bikes I have seen.

Barks
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Re: Brompton Electric Conversion Advice please

Postby Barks » 27 Mar 2019, 8:28am

Brucey wrote:the torque isn't that high (like brake torque is) and it isn't 'pulsy' (like pedalling torque is) so it is probably going to be OK. It might be better to build even x1 but if this makes the spokes go into the rim at a funny angle it is a question of choosing the lesser of two evils.

BTW I thought the whole point of a folding bike was that you could carry it. Most e-bike conversions near enough double the weight, don't they?

cheers


Data from Brompton’s website for their own models - 2-speed: 13.7 kg (16.6 kg total with battery)
6-speed: 14.5 kg (17.4 kg total with battery. This is around 1-2 kegs extra for the bike (depending on model) plus 2.9 kg for the battery.

While obviously heavier, as the battery easily comes off any carry is with bike in one hand, battery bag in the other which helps balance up. That said, I rearely carry my [normal] Brompton anywhere, it’s either wheeled around as a bike or on the rack wheels when half folded. The only time it is fully folded is to put a train, bus or into car and just a few metres carry. But if you NEED electric assist, carrying any bike even that distance might be quite a challenge. One often overlooked advantage of folders though is ability store easily particularly in office, flat or apartment. Horses for Courses really