jerrysimon

This is my wheel. On the TopBikeKit website it says their motor is 1.6kg which is impressive. Are they quiet ?

I hope I am not hijacking this thread just say I use to post several times every day on this forum for years when I was learning this stuff. If you are interested here are my Tongxin 36v, 180w, 260RPM, 28h motors. Not sure if you can still get them. They are only three wire not hall sensored. The beauty is they have steel roller bearings inside not gears so are vertually silent when running. I use to purchase them in pairs as it was cheaper direct from China for shipping. No Paypal back then, so we paid up front directly into accounts and often waited 6 weeks for delivery with no guarantees! The Chinese to English transulation often ended up confused hence we ended up with motors with roller brakes on them, wrong number of holes etc etc. It got better and the sellers always delivered and were honest. It really was an act of faith sending them money. They were 80mm widebetween shaft bearings, 120mm diam and needed spacers to stop the forks fowling, so the Brompton forks needed to be spread about 8-10mm and fork cutouts widened for the larger motor shafts! Just over 2.1Kg, maybe new ones are much lighter now ? PS just re-read thread and looks like the ones you are using now are a little bit lighter. When we fitted these they were at least 0.5kg lighter than the equivalent traditional geared motors. Maybe the ones now are also higher than powered ? These draw about 2 amps when you pedal assisting on the flat and a max of about 6-7amps (set) when you are going up a hill. There's only one in Cambridge! With the controllers back then we could re-program it to ensure we kept the current down and stopped them slipping on their clutches etc.

If you want to learn how to build wheels then 16/20" is the place to start. Plenty of youtube howtos and info on line. Small wheel builds are easy. I had to learn as 13 years ago it was impossible to get anyone to do electric hub builds for Brompton/small wheels. Radial makes it even easier. Years ago we did posts on here about how we learnt. I can now do large wheels including rear wheels/dishing etc. I am not an expert, but have built loads for my various bikes which have performed perfectly well. Here is a few builds I have done on the Brompton wheels. From left to right SRAM auto change 2 speed which was on my Brompton for a while. Two speed rear Brompton wheel and a radial front on a double walled Brompton rim.

Looking again at SJSCycles it appears some Brompton rims are only suited for rear/hub builds and as the spokes are crossed I guess that is why the angles are more and thus the holes drilled at an angle. They specifically say not for front wheels/two speed rear wheels or radial built wheels. As I said as long as the spokes on the electric motor hub are built radial, straight drilled holes would be fine. I guess you could use the double rim Brompton front wheel rim shown below, but to be honest all mine are single walled and have lasted years. https://www.sjscycles.co.uk/rims-tape/brompton-16-x-1-38-349-standard-drilled-double-wall-rim-silver-28-hole/ We did also use the Sun CR18 double walled rims but they were a nightmare to get Marathon Plus tyres on!

Last post today We use to use these which are single walled but obviously now you can get better double walled ones for the Brompton. Back then all Brompton rim holes were drilled straight whereas now, for the rear at least, I think they are drilled at an angle. https://www.sjscycles.co.uk/rims-tape/16-x-1-38-349-standard-drilled-single-wall-rim-silver-28-hole/

When we first built them we use to lace them up 1X but soon realised that radial lacing was sufficient (strength wise) for such small wheels. This also made the spoke angle and building more managable/simple As you can see on the wheel in the front of the picture (black Brompton) this was a 36H motor hub. Back then we managed to get the last few 16" ETRO 349 wheels that were drilled 36h. That was one of the first wheels I ever built, but as I said later we got motors with 28H which made everything much easier.

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.

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

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

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

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!

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.

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.

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

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.