eBrompton Build

[Woosh]

that's a truly outstanding job.

 

[saneagle]

I attached a roller wheel to the rear mudguard on the Brompton and fitted the mudguard in place with the titanium stays. It looks like this;

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The LitePro easy wheel extension bar (£11) which is the black aluminium bar just behind the seat post in the picture above, was needed to space the folded Brompton off the ground a bit. Without the easy wheel extension in place the front wheel of the folded Brompton touches the ground and you cannot roll it or easily push it under a desk. The other advantage of fitting the easy wheel extension bar is that when you pull the right wheel out the folded eBrompton does not fall over, which is good. See the pictures below;

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You can now push the folded Brompton around on the floor on the easy and mudguard wheels. The rolling is not as good as having a rear rack with wheels on which is really needed for pushing the Brompton around a shop fully folded with the handlebars down. With the mudguard wheel setup you can however fold the handlebars up and push or pull the Brompton around like a cart whilst holding the handlebars.

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Some more pictures;


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This eBrompton conversion when setup for every day use, which inludes having the mudguards, weighs in at 11.95Kg complete. Replacing the steel main tube and steering tube with titanium versions would cut the weight to around 11Kg, maybe one day.

The Electric Brompton that Brompton sell is advertised as base 13.7Kg, plus 2.9Kg for the battery.

Conclusion:

The main advantage of this DIY conversion has been the significantly reduced weight, which for us older human types definitely makes handling the folded Brompton a lot lot easier. My previous Swytchified Brompton was about 6Kg heavier than this conversion, too heavy for me these days. The other main advantage is that the battery\controller remains attached to the eBrompton when folded and rolled.

That red chainwheel has got to go. I don't care what your excuses are, it's positively offensive to any eye that has a sense of aesthetics. If you lived next door to me, I'd have to give you the money to get it fixed rather than have to see it every day.

 

[alemanyorks]

Why build an eBrompton ?

The Brompton is a good bike for shopping or commuting and short range leisure trips. The neatness and compactness of the fold is a compelling advantage, you wont have trouble taking it on public transport or storing it in a corner etc. Fitted with a decent set of ‘easy’ wheels and a rear rack you can take it into shops and push it around folded like a small shopping trolley.

I bought a standard 3 speed Brompton some 20 years ago which I used to get to the train station to commute into work in Bristol and Swansea. About 3 years back after retiring and being bored, I added a Swytch electric kit to the Brompton. The now eBike was just fine, great for shopping trips to avoid taking the car or meeting in town for a tea.

Recently I had been noticing how heavy my current swytchified Brompton was, its a little over 18Kg. I had wanted a lighter bike for some time and of course the new T-Line Titanium\Carbon Brompton at 7.45Kg looked appealing, even with the hefty price tag.

However, the T-Line Brompton has carbon forks so unlikely to be suitable for an electric front hub motor. There are no titanium front forks, maybe there will be sometime soon. I did ask, but the standard steel forks would not fit in a T-line.

I picked up a 3 year old 3 speed (Sturmey type hub gear) Brompton, in good condition, that had most all of the steel bolts replaced with titanium ones and other lightweight parts fitted too. It came with all the original replaced parts too, so a handy source of spares. After a bit of work, I had this Brompton down to 8.5Kg, not bad considering the all titanium framed T-Line is 7.45Kg.

One maybe not obvious feature of the Brompton is its popularity, particularly in the far East. As a result of this popularity there are lots of people out there making and supplying replica parts from the most basic to all the way up to replacement titanium frames and all compatible with the classic Brompton. Want carbon wheels ? Well there is a wide range to choose from. Multiple choices for gearing setups etc. Its a modders paradise.

For instance, whilst the Brompton folding pedal is good, its heavy. You can get a set of titanium axle pedals, right fixed, left removable for around £40 and a weight saving of around 200g. Want to replace all those steel bolts used in the brakes with non-corroding lightweight titanium ones, you can, several manufacturers makes sets of them.

One of the significant weight savings, over a standard 3 speed Brompton, is to fit the 2 speed derailleur rear wheel, this is some 600g lighter than the normal 3 speed Sturmey setup.

The ultimate aim of lightening up a Brompton was to convert it to an eBrompton. My experiences over 2-3 years using the swytchified Brompton were that 2 speeds was enough. Recently I realised I had been out on several Brompton trips with the rear hub key puller chain disconnected and I never noticed. So I figured a two speed would be enough. One of the almost standard mods you can do is to replace the standard rear wheel 2 speed cogs with a 3 speed setup, they use narrower cogs and an 11 speed chain. So more gears if you needed them. You can also by kits that replace the rear wheel with a 6\7 speed derailleur setup, so there are plenty of gear options out there.

So I have a 2 speed, possibly 3 speed Brompton, that is only 1Kg heavier that the single speed T-Line, and it cost less than half what a T-Line would be.

Here is the picture of the road ready Brompton ready for conversion. Most bolts and the bottom bracket are titanium, as is the front wheel axle. Titanium rear frame triangle and forks. Tanus puncture free tyre on the rear, Schwalbe Kojak tyre and Tubolito inner tube on the front. Carbon bars and lightweight brake levers.


View attachment 51142


How heavy would eBrompton be ?

I have the swytchified Brompton so I know how much weight a front wheel hub motor will add. I have spares of Julet cables, motor cables, KT controller etc to weigh so I estimate that an eBrompton conversion would add around 2.3Kg weight plus that of the battery. A 10S2P 7Ahr battery would be plenty for my needs and adds around 1150g in weight, so the potential conversion would add in total around 3.45Kg. The would take the weight of eBrompton up to just under 12Kg.

Next: Problems with handlebars

Really good job done there, were you ever worried that the hub motor may spin out of the titanium front fork without a torque arm fitted?....that's the only thing putting me off fitting a titanium fork to my brommie.

 

[StuartsProjects]

were you ever worried that the hub motor may spin out of the titanium front fork without a torque arm fitted?.

There are many conversion kits for Bromptons, I dont recall any reports of the hub motor doing a 'spin out' ?

Is there a conversion kit for a Brompton that uses a torque arm ?

 

[Woosh]

No. Your kit and mine have the same small antitorque washer.

 

[alemanyorks]

Well that's good to hear, I wouldn't be concerned with a steel fork and a small torque motor just thought Ti is a bit 'softer' and it could happen.

 

[StuartsProjects]

This looks familiar ......................

New Suitable for Brompton Bike Motor 74mm TBK-74AD 36V 250W 48V 250W Front Motor 28holes +16inch 349wheel Rim+Font Light - AliExpress 18

Smarter Shopping, Better Living! Aliexpress.com

www.aliexpress.com

And no they did not ask ......................................

 

[AndyBike]

That red chainwheel has got to go

Don't listen to these heathens. They're still living in black and white Victorian Britain

I think theres plenty room for a bit more anodizing.

Purple, blue, red all looks the part. You can never have enough anodizing.

Just a shame you dont have disc brakes. I've a nice set of new Hope X2/E4 calipers in purple, looking for a home.

I need to add the rest and sort my ano collection out. More purple, and orange to find a spot for.
Is black classed as 'anodizing' in the colourful sense of the word ? If so I've a fair bit of that to add too.

 

[StuartsProjects]

I do like a bit of colour.

I dont have hydraulics on the Brompton, but do on my other electric bike. The calipers for the hydraulics on that are 'titanium' coloured, so the finish lasts almost forever, the frame in the picture below is 20+ years old;





There are rumors that a 20" Wheel Brompton with hydraulics will be released soon.

 

[I893469365902345609348566]

There are Brompton forks for hydraulic brakes listed here.

 

[AndyBike]

I do like a bit of colour.

I dont have hydraulics on the Brompton, but do on my other electric bike. The calipers for the hydraulics on that are 'titanium' coloured, so the finish lasts almost forever, the frame in the picture below is 20+ years old;


View attachment 55066


There are rumors that a 20" Wheel Brompton with hydraulics will be released soon.

Heavens sake, those are old old old. Hope Enduro4 if im not mistaken(which im not)
They were decent brakes bitd, but pretty poor power by today's standards. Im on tech4 v4 on both my bikes. Which is probably in the top 5 power wise in the disc brake world. Comparable to trickstuff.
I ran Hope C2's bitd, which are pretty much comparable to something like the Hope V2 from 2010

The colour is just standard alloy colour.
But like all Hope brakes(and hubs) theyre still serviceable, and parts like pistons/seals are easily available. Pads too, as well as seals etc on the levers

The trick is to make sure you keep them clean. Wash off any road salt from winter as that eats alloy for breakfast

 

[AndyBike]

There are Brompton forks for hydraulic brakes listed here.

" Front Hope Race XCR Hydraulic Disc Brake, New Forks: £595 "

Theres no real need to use the XCR, which is pretty much ha racing brake and any Hope brake from any era over the last 20 years will fit and work just as well. With the exception of the newer Tech4 lever which will increase the power of any Hope caliper
The Race XCR is more expensive than even the latest tech4 (e4/x2/v4)

I just bought a pair of tech4 v4(f&r) for a total of £320 and i can stop me and the emtb with a combined weight of 120kg on just the front brake alone

The only brake in the Hope line up to avoid is the early (2002) Hope XC4. NEVER buy an XC4, as it is hub dependent and the rotor size is different and usually hard to come by.

 

[saneagle]

There are Brompton forks for hydraulic brakes listed here.

And they're 100mm, so any disc brake (or rim brake) motor, like the Q100/AKM100 would slot straight in. I wonder how much the forks cost on their own?

 

[AndyBike]

I wonder how much the forks cost on their own?

Some basic arithmetic of the Hope brake itself, which Brompton are saying is £295, subtracted from £595 means the fork looks to be £300.
Thats pretty pricey for a rigid fork.

There are Brompton forks available and theyre priced at £99, but they also do a titanium fork which retails between £350-400, so it could be one of those.

 

[I893469365902345609348566]

And they're 100mm, so any disc brake (or rim brake) motor, like the Q100/AKM100 would slot straight in. I wonder how much the forks cost on their own?

This titanium or titanium coloured one is £294.66? I've gone off titanium ever since it got screwed into my wrist.

Page Not Found - Aliexpress.com

 

[StuartsProjects]

You can buy the geniune Brompton made titanium forks, which are the ones I have, when in stock ......

https://www.condorcycles.com/products/brompton-titanium-fork?variant=41037174730

 

[I893469365902345609348566]

Are the genuine brompton forks 74mm? The titanium or titanium coloured ones on AliExpress claim to be 100mm, for disk brakes.

 

[StuartsProjects]

Are the genuine brompton forks 74mm?

Yes.

 

[lenny]

Boost’s Brompton-specific version of its electric bike conversion system adds 2.5kg to the weight of a Brompton.

First look | Boost’s new Brompton ebike conversion kit promises lightweight electrification

Conversion kit uses rear-hub motor and weighs 2.5kg

www.bikeradar.com

 

[jimriley]

Here's some pics of the little bag that fits the woosh controller. Aptonia Nutrition Bag