|Newsletter - 2011 Archive|
Riding the Moulton AM-7 on a brevet
I noticed on the recent Vancouver Island 300 that one of the riders (Jacques Bilinski) was on an old Moulton AM-series “folding” bike [editorial note: Jacques and his Moulton were also at the LM-300a this past Saturday - Photo]. This reminded me of the AM-7 I rode back in the 1980’s, and the 400km brevet I had ridden on it.
Moulton’s AM-series bikes were the second generation of his popular “F-frame” bikes of the 60’s. The original Moultons did not fold up as many believed, but like the later AM’s, came apart, but more on that later. The first generation Moultons became quite popular and helped characterize the swinging London of that time, with its Mod fashions and Mini-Coopers.
The original Mini-Cooper figured prominently in the Moulton story. Dr. Alex Moulton was the man responsible for the rubberized cone suspension system used on the Mini. Not only was it one of the more prominent and ingenious features of this landmark vehicle, the ball-joint suspension reappeared in the revamped design of the Moulton AM-7.
The AM-7 (because it had a single chainring and a 7-speed freewheel) was a revolutionary bicycle back in the early 1980’s, a remarkable demonstration of engineering acumen. It was a complete redesign of the original folding Moulton. To make the frame lighter, Moulton replaced the large and bulky single main tube with a “birdcage” space frame chassis formed of triangles using smaller, lighter tubes. To make it even more practical, the frame was designed to come apart. The two parts were joined by a large central king pin tightened by a plastic knob. The cables for rear brake and rear derailleur had splitters inline which incorporated an ingenious bell housing.
Because of its stiff frame and its use of 17” wheels, the most remarkable feature of the AM-7 was its front and rear suspension, necessary to attenuate what would have been a harsh ride. The front suspension used a telescoping steerer tube, with the spring inside the head tube, and with trailing links that used polymer pads for damping. The rear suspension consisted of a hinge behind the bottom bracket that allowed the rear triangle to pivot, and the damping was the Mini’s rubberized ball and socket mounted at the back of the seat tube. It was actually more of a shock absorber than a suspension in back.
Component selection was where the AM-7 cheaped out. The bike came equipped with Euro-trash components: CLB sidepull brakes with their cheesy levers, Zeus small-flange hubs with 28 spokes laced radially in front and crossed in back to the 17” rims. Rear derailleur was Suntour, as I recall, as were the cranks. The bike came with drop handlebars and a cheap French stem.
I took delivery of a couple of AM-7’s back in the early 1980’s. One I put lots of miles on, including at least one 400 km brevet. The other I had ordered because someone else wanted to buy one, but that fell thru, so I ended up using it for spare parts. Which was a good thing.
The first thing I did with the new Moulton was to replace the handlebars, levers, and saddle with decent components. I mounted a Cinelli bar and stem with Campag brake levers, and replaced the saddle with the standard Cinelli #2 of the time, setting the bike up to correspond to my position on a traditional bike. The CLB brakes were replaced with Suntour or Shimano, but I left the gearing as it was. Because of the smaller wheels, you had to use the special cluster that came with it. State of the art in those days was a 7-speed freewheel still threaded to a hub (cassettes hadn’t been invented yet), spacing was 126 (the 7 cogs fit in the space of a standard 6-cog freewheel of the time), and the smallest cog had 9 teeth.
The bike came with fenders and racks, and if you bought the bags with it, you could actually take the bike apart and put it into the large bag that was designed to fit on the rear rack!
Although the bike handled well on the flat, and it was comfortable on bumpy roads due to its suspension, it did have a number of drawbacks. First, its long stainless-steel seat post had an annoying habit of slipping in the seat tube. It would slip no matter how much you tightened the seatpost binder. I even resorted to mounting a hose clamp on the post to prevent it from sliding, but all this did was to dent the delicate stainless steel post.
Next, there was no way to lock out the front suspension, although you could tighten down the spring as much as possible with a knurled knob at the base of the head tube, and you could tighten down the dampers on the trailing links. This meant that you couldn’t really stand up on climbs, because the front end would bounce like a pogo stick. The best you could do was to climb in a seated position, and reduce any upper body motion in order to stabilize the front end. And in fact, this was a good thing – it taught you how to climb efficiently in a seated position. The ugliest climbers in all of cycling are mountain bikers. Their upper bodies tend to bounce up and down as they climb. This is extremely inefficient and energy-sapping, and it doesn’t accomplish anything. In order to prevent the front end of the Moulton from pogoing, you had to keep your upper body perfectly still, saving lots of energy and focusing all of it into the pedaling stroke.
The next problem was the front hub. Most hub manufacturers will void their warranties if you lace the hub radially. The reason for this is easy to see in the winter, when you ride on salted roads. The salt corrodes and weakens the aluminum. Because the hubs on a 17” wheel are much close to the ground than on a standard 700C wheel, they are exposed to more water and salt. Before too long, the hub flanges get corroded to the point that the radial spokes rip the flanges apart. I broke more than one radially-spoked hub in one or two winters of commuting on the AM-7. The solution, of course, was to not use radial spoking. Tangential patterns will not rip hub flanges apart.
The 17” wheel size presented some problems. First, despite being optimized for minimal rolling resistance when paired with suspension, it is non-standard, so tires could only be sourced from shops that sell Moultons (Angle Lake Cyclery just south of Seattle was great to deal with; we didn’t have the internet at that time, so no looking for tires online). Because of their small diameter, they tend to wear faster than 700C tires. You can only get them in one diameter. And even innertubes are hard to find; try finding 17” tubes with Presta valves. I ended up cutting down standard tubes, using the larger Rema patches to seal the cut tube together (or unthreading the Presta valves from Michelin tubes that allowed for this, and installing the valves on close-to-17” tubes). Moulton did go to an ISO-standard wheel size later (20”), but this doesn’t help if you’re an AM-series owner.
I remember riding the bike in Vernon during the summer. I had visited the Grey Monk winery, which is located in a very hilly area near Vernon. Coming down one of the very steep hills, I had full braking force applied, and one of the innertubes blew out from the heat. Smaller rim = more revolutions of braking friction = more heat buildup/less heat dissipation = higher air temperature in the tube. And the bike was unloaded (I don’t ride with packs on the bike, though I may have been wearing a backpack for the winery excursion).
I did travel with the bike. I covered the 1984 LA Olympics for a Canadian cycling publication of the time. I flew into LAX with the bike in a duffel bag, and I rode everywhere with it. I recall that the clean-cut security guys in their snappy suits and discreet earbuds wouldn’t let me bring the bike into the velodrome grounds, even with my press accreditation. I had to leave it locked outside.
I forget how I had the bike configured for the 400km brevet I did on it. It must have had lights, and I was using a generator on my standard rando bike at the time, but I could well have used battery lights if there were a problem mounting the generator, or if I was concerned about the risk of overdriving the lights on a 17” wheel. I don’t remember much about the ride, other than having to be smooth on the climbs, and that it was nice floating over bumps in the road, especially when you couldn’t see them in the dark. I don’t even remember where I went, although it may have been to Marysville, WA and back.
And that was the major advantage, the suspension. The small light wheels and the front/rear suspension reduced the unsprung weight of the bike to the weight of the wheels. This allowed for very confident cornering, especially on bumpy turns. The lower the unsprung weight, the more the tires stay in contact with the road. This is why – on your standard bike – you raise yourself off the saddle and weight the outside pedal on a turn, not to “lower your center of gravity” as most ignorant “experts” claim (in fact, of course, you actually raise your center of mass by raising yourself off the saddle*), but to turn your arms and legs into springs so that the unsuspended bike itself becomes the unsprung weight, pivoting around the lower pedal. Result: when you hit a bump, the tires spend less time in the air, and therefore have less risk of bouncing/skidding on landing.
(* If you want to know roughly where your center of mass is, imagine yourself floating weightless in space, on your bike. Now imagine that you and the bike start to turn somersaults in this weightless environment. Your center of mass is the point around which you and the bike are rotating. So you can see that it is ludicrous to think that just by applying your weight to the downside pedal, you are somehow “lowering” your center of mass. Put your weight on the pedal as you rotate in space, and there is no effect on the location of the point around which you are rotating.)
I did have a run-in with Dr. Alex Moulton, CBE. During Expo 86, there was an International Human-Powered Vehicle Event held near Vancouver, and Dr. Moulton was invited to speak at the adjoining conference downtown. I was able to buttonhole him prior to his talk, and as nicely as I could, I pointed out to him some of his bike’s shortcomings previously listed. Being the typical arrogant Englishman who brooked no disagreements with his designs and did not suffer fools gladly, he was quite taken aback that anyone – least of all some mere colonial without even an engineering degree – should find fault with his marvellous invention, and took me to task in his ensuing speech. But I just characterized his behaviour as being symptomatic of the sunset of British technology extant at the time. Once-popular British-made sports cars and motorcycles were renowned for being sloppily built and for consistently leaking oil, and the Brits made no attempt to fix things. Why should their bicycle industry be any different? Hence, the demise of Britain as a manufacturing nation, and the decline of my interest in continuing to ride the Moulton AM-7.
Here’s how the AM-7 comes apart. Also note the internal spring located in the head tube, and the way the rubber-cone rear suspension works.
May 3, 2011