Now with additional comments following 2 week's use
Bikes with a single chainwheel and large numbers of derailleur gears (well, 7 or more anyway) seem to be rather prone to the chain falling off. Although AM7s and AM8s seem to suffer from this particularly, they are not unique in this respect, and I have had the same problem with other makes of bike with a single chainwheel. The front changer on a multi-chainwheel derailleur system obviously serves a useful purpose in helping to keep the chain in place, as well as shifting it from one chainwheel to the other.
Soon after the NS (New Series) Moulton was introduced, a small accessory
known as the chain keeper was added to the bike to prevent the chain coming
adrift on that model. A slightly modified version of this is now available
for the AM 7 and 8, and I have recently obtained one of these. It is very
easily fitted, simply fixing to the upright part of the rear triangle
alongside the chainwheel. A report on its performance based on the first 2
week's use follows the photographs.
Over the first week the chain keeper was used with the regular Stronglight 48 tooth chainwheel on the AM7. During that time the chain stayed where it should be - it has not been unknown to get through a week without the chain coming adrift in the past, but more often than not it would have misbehaved at least once during an upward change. In the past I have always taken particular care with upward changes to try to reduce the possibility of the chain coming off, whereas with the chain keeper in place no particular precautions were taken. During most upward changes I could hear the chain flick against the keeper, strongly suggesting that it was performing a useful task.
After the first week, the chainset was replaced with a 46 tooth Camapag one - I have been finding that I was making little use of top gear, and some extra reserve at the bottom end of the range is always useful. In addition, the AM7 seemed likely to be the bike used for a ride from Lands End to Broadstairs, at a leisurely pace with a fair load on board, for which lower gearing would be an advantage. The chain keeper had to be slightly repositioned to suit the smaller chainwheel, which took a matter of seconds, and the position was slightly altered during the next ride as it was rubbing against the chain in bottom gear. Once again there has been no problem with the chain coming off, and the chain keeper can be heard doing useful work during upward gear changes. With the chain keeper in place it seems easier to observe what happens to the chain while making upward changes - it certainly flaps about quite a lot, or would do if the keeper were not there to restrain it.
Overall then the chain keeper seems to have done its job so far, and has removed a major aggravation of using the AM7. Since it is a hand made device it is quite expensive, but well worth it. Something similar could probably be fabricated by many owners for themselves, providing they have the necessary skills, materials and equipment (do not attempt any work on a bicycle unless you have the ability to do it safely). If you have had problems with the chain coming off on the single chainwheel on the AM7 or AM8, or indeed any other bike, during upward changes, you may well find this chain keeper, or something similar, is a good investment.
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Last updated: 1 September 1999