eBrompton Build

[StuartsProjects]

Ti Parts Workshop Titanium + Carbon Rear Rack for Brompton Bicycle

For Brompton A/C/E Line This rear rack offered the push-ability, fold-ability and stability to the Brompton. It works just the same way as the original rear rack. When unfold, it gives you the sporty and minimal design which featuring the lightest combination of titanium and carbon fiber...

www.fantastic4toys.com

If its for a Brompton it will most likely fit.

I have got a cheap alloy one here to try, its a bit shorter than that one above, and does weigh 161g versus 134g, but it was only about £20 versus the £250+ the carbon titanium ones can cost.

As long as the rack I have is long enough for shopping trolley mode, then thats OK. I dont need a full length rack for putting stuff on.

 

[guerney]

But I may change the brake cables to black so the electric cables blend in a bit more and are not so obvious.

I like your colour scheme. Hi-viz is preferable to the current general public's obsession with dark coloured bikes. I might go with yellow or red for the Espresso, was thinking silver to match the silver aluminium frame. Once thing's for sure, my cables won't be stealth black!

Pardon our interruption...

 

[guerney]

I have got a cheap alloy one here to try, its a bit shorter than that one above, and does weigh 161g versus 134g, but it was only about £20 versus the £250+ the carbon titanium ones can cost.

£8.51+ per gram! Deffo stick with the alloy.

 

[StuartsProjects]

my cables won't be stealth black!

I think mine will be, and I have a few other ideas for eBrompton stealth mode.

I could have had the motor in black but its not that big and in silver looks less like an eMotor wheel.

 

[guerney]

I think mine will be, and I have a few other ideas for eBrompton stealth mode.

Don't do this, it'll only add weight:

 

[StuartsProjects]

How to save 13.2g

The metal ring that you would normally use to hold the PAS disk together on a heavyweight eBike, weighs 13.3g.

The PAS disk halves seem stiff enough when pushed together and to keep the halves together without the heavy ring, I used a bit of spectra cord.

 

[jerrysimon]

Years since I posted here but nice to see people still converting Bromptons. I was one of the first on here using a lightweight Tongxin (almost silent) motor sourced and shipped from China in 2010.

I'm retired now but the steel one is still going strong. I now use prebuilt 4Ah 36v lawn mower batteries (have quality/safe cells in them and no sag with my setup) which you can pick up from ebay for around £40 and just make a connector to fit the battery. Back then we use to build our own batteries and I did that to keep them light and as I live in Cambridge (its very flat) I didn't need to carry a massive 10-12Ah one.

I also converted a Ti Brompton in 2012 with a very lightweight but subsequentally unreliable motor. Here are some pics of both bikes. I deconverted and sold the Ti years ago. This is my original steel brompton now 13 years old (upgraded with lots of newer Brompton parts). All the electronics and battery are in the front bag connected to the bike with an umbilical wire/plug. Back then we could legally use just a thumb throttle which kept it all simple.



The Ti which I think was around 11-12kg excl battery ?



PS if you want more info I will post details of battery and connector.

 

[StuartsProjects]

4Ah 36v lawn mower batteries

Could be interested, are they Lithium ?

And did you find the 4Ahr lasting long enough for local shopping trips etc.

Retired here too.

 

[jerrysimon]

Li-Ion. Hold on I will take a photo and post.

 

[jerrysimon]

There you go

Good quality/safe Li-Ion Samsung Cells with a BMS built in. You'll need a charger and make some kind of connector (mine is also fused) as shown. Made by Spear & Jackson. These are from an older model lawnmower sold by Argos. I have four purchased off ebay as lots of the lawn mowers are returned and ebay sellers buy up old/unused stock and sell bits on ebay.

 

[jerrysimon]

All my electronics go in one back pocket of the Brompton bag and the battery in the other (it just fits). This keeps everything light, the main bag empty.and means you can carry Brompton in one hand and bag in another

We had all the same issues you have found buying ready made up wheel sets re tyres so in the end build our own wheels

PS therer are newer versions of mowers and hence batteries around now.

 

[StuartsProjects]

We had all the same issues you have found buying ready made up wheel sets re tyres so in the end build our own wheels

Interesting to know.

I will end up with a 'spare' Motor wheel from the Swytch kit, so at some point in the future I might just buy a proper Brompton rim and teach myself wheel building.

And thanks for the pictures, there are hoverboard batteries around at 4Ahr - 5Ahr, £50 to £75 that come in a plastic case too. Might be worth buying one just to see how long its lasts.

 

[jerrysimon]

Meant to add in Cambridge (very flat) I get between 10-15 miles depending on wind. If I go further I just carry a spare. The motor is only 180w so not power hungry, draws less than 5-6amps max and mostly when I am pedaling less than a couple of amps. The solution would not meet requiments of people in much more hillier places!

 

[jerrysimon]

Interesting to know.

I will end up with a 'spare' Motor wheel from the Swytch kit, so at some point in the future I might just buy a proper Brompton rim and teach myself wheel building.

And thanks for the pictures, there are hoverboard batteries around at 4Ahr - 5Ahr, £50 to £75 that come in a plastic case too. Might be worth buying one just to see how long its lasts.

Probably Lithium Polymer which I used a lot in RC Flight (super light) but prefer safer Li-Ion cells on an ebike.

Mine are built into both the older and newer Brompton rims which is not difficult for radial builds, as long as you get the spoke length correct

 

[StuartsProjects]

Probably Lithium Polymer which I used a lot in RC Flight (super light) but prefer safer Li-Ion cells on an ebike.

No, they are 18650 Lithium Ion. Although given that they are for sale at £50 (delivered) in the UK, one might imagine they are made of no-name cells in the far East.

as long as you get the spoke length correct

If the ERD is the same, maybe the old spokes will fit.

 

[jerrysimon]

No, they are 18650 Lithium Ion. Although given that they are for sale at £50 (delivered) in the UK, one might imagine they are made of no-name cells in the far East.




If the ERD is the same, maybe the old spokes will fit.

The eletric hub will be much larger than the stock one, so very unlikely.

 

[StuartsProjects]

The eletric hub will be much larger than the stock one, so very unlikely.

The wheel with the not fully compatible rim on it, is the front motor wheel.

Spokes are around 147mm on a standard wheel, and about 112mm on the wheel I would re-rim.

 

[jerrysimon]

Yes on my 100mm hubs from memory, I think they are around 118mm. Radial builds are quite easy just lace up, bring up to tension and then work round keeping the rim straight and circular as you can. Loads of youtube videos show you how

 

[StuartsProjects]

Radial builds are quite easy just lace up, bring up to tension and then work round keeping the rim straight and circular as you can. Loads of youtube videos show you how

Do you know if there is anything special about the rim for one of these motor wheels ?

Looking at the spoke holes on the TBK 74AD Motor wheel and my Swytch motor wheel they do not look like they have been drilled to accomodate the more outward angle of the spokes.

 

[jerrysimon]

Do you know if there is anything special about the rim for one of these motor wheels ?

Looking at the spoke holes on the TBK 74AD Motor wheel and my Swytch motor wheel they do not look like they have been drilled to accomodate the more outward angle of the spokes.

All I recall (is was 13 years ago) the ones provided ready built from China use to have a generic 16" rim that had an ETRO of 305 whereas the Brompton rims are ETRO 349. The other challenge back then was the motors only came with 36h so could not be laced into a standard Brompton rim which was 28h. That changed later when they made us motors with 28h. As long as your motor is 28h you should be able to relace it up easiy in a stock Brompton rim

Again with the angles of the radial lacing somtimes we use to put copper washers on the spoke head (on the hub flange) to help seat them properly. The countersink on the hub flages were not machined very well. I suspect things are better now in terms of the hole drilling and counter sink on the flanges.