I have been converting and upgrading ebromptons for over 3 years now. Here is my latest super light M2L-X with a very low assist lightweight (not the Tongxin/Nano motors mentioned which I have already tried) and has the same carry weight 11.5kg as a stock M3L. This motor is about 1.4kg and is not much bigger (about 98mm across) than a dynamo. I have now done over 5000 miles in three years on my daily commute Brompton econversions.



This is the flickr set http://www.flickr.com/photos/4505157...7630015987898/

As stated there are loads of pedelec posts covering this, some of them mine, plus on the yahoo Brompton forum this was covered extensively very recently.

Note the stock Brompton e conversion has been put on hold with no firm date of when they will go to market. I had extensive discussions with them with mine above and it is clear they will not come to market until they are 100% sure it will work reliably.

As stated it does require a certain amount of skill to undertake conversions depending on if you get someone to do the whole conversion, buy a kit or as I do now source all the parts individually direct from China and build your own wheels. The latter is by far the cheapest option and costs me about £250-£300 including a small battery. Getting someone to do it for you can cost almost as much as the original bike in some cases!

Here are the two motors I have tried.





Jerry