|The roads leading up to Lancaster University are a little rough, and those on the Campus were terrible. So much so that riding a bicycle without suspension gets dangerous. Suspended bicycles exist, but tend, as with most bicycles in British shops, to be aimed at sporting use. What you actually need is a couple of inches travel on both back and front. In addition, if you have suspension you can run hard tyres, and have small wheels to get the rotating mass down a bit.
I was going to build something, but, as it happens, such a machine already exists. The Moulton is a lovely little machine. Unfortunately a new one costs about £1400, and you would have to spend a fair amount to get a proper gearbox and brakes on it. However, they have been in production since 1962, and old F-framed ones can be bought for £50.
The photograph to the right shows the dismantled Moultion MkI I bought from my cousin. It is not in good condition, but after nearly 50 years, and from the wear of the wheel rims it has been used for a good deal of that time, one wouldn't expect it to be. A great guide to the F-frame Moultons can be found here.
The Mk.I Moulton F-frame front suspension, and in fact all Moulton F-framed bikes, had an arrangement of sliding splines to allow movement and steering. The exact components for which are featured in the topmost photograph to the left.
The guide to the F-frame front suspension is accurate, and gives good advice. However, for the very early MkIs what appears to be a slotted machine screw holding the steering tube and rebound spring in is not a screw at all. I don't know what it is, nor have I any idea how they got it in there, but it is not threaded at all. The only way of removing it is to drill it out. I used an expendable drill silver soldered into 12" of hex bar, and a guide bush made from some scrap brass to keep it on the non-screw head.
This allows you to separate the steering tube and forks, but the drilling process makes a mess of the rebound spring guide tube. As that is welded in the only option is to drill that out as well. I used a 16mm long masonary drill in an SDS drill, and just used it to remove the guide tube. This leaves you with a severly mangeled assembly seen here in the centre photograph to the left.
Designing new components, and machining them up, is relatively easy compared to getting it all apart. The replacement rebound spring tube was machined from solid, and is seen on the bottom photograph in the top left corner. Reassembly is a pain as it has to go back together in exactly the right order, but it will go back together if you follow this guide, with additional information from this guide.
The only problem I now have is which grease to use to lubricate the rebuilt forks. In there is steel, aluminium, rubber, and nylon, so the lubricant has to be something which won't rot the rubber or nylon. The guides recommend Molyslip, or some grease used for car CV joints. I may try some formulation such as Morris K76 Red Rubber grease.
|The rear suspension was in a slightly worse state than that of the front. All the problems of seized bearings, and fatigue cracking seen in this guide were present. So far I have silver soldered a patch across the fatigue cracking to spread the loads, and so act as a repair, and I have added in some 3mm plate to spread the suspension load further across the arm. The Mk.Is were brazed, and so I stuck with a compatible method for attaching more metal. You might have problems if you tried to weld and didn't remove the pre-existing braze, which in the case of my swinging arm would entail dismantling it completely.|
|The original 16" Moulton supplied wheels, despite thick chrome plating, had worn through. A local plating company were unable to do anything with them, so I decided the best course would be to replace the rims with modern 16" Brompton items. This has the advantage that they're reasonably cheap, and have tyres available for them.
A Shimano Nexus 7 gearbox was bought. It looked like a bargan at the time, but getting hold of the ger changing assembly took some time, but the real problem was that the rims had 28 holes, and the Nexus 7 had 36 holes. A solution had already been worked out by Benjamin Lewis over at the great Sheldon Brown's site. I had to modify Benjamin's design because the Moulton spokes are very much shorter than normal bicycle wheel spokes, and don't fit well. The main revision was to the crossed pair on either side of the main groups of three spokes. The picture to the left has been generated from a .dxf file available here which I created using Librecad. The layers in the .dxf file will give you a much better idea of how the spokes are arranged, and which holes have no spoke, than any picture can.
The mechanics of spoke making are relatively simple. Go here for a guide. All you need are the dies to impress the threads and some standard spokes. A lathe helps to hold it all in line. Here the threading die was held in the tailstock, and a spoke which had been cut to length held in the 3-jaw. The headstock spindle was turned by hand crank. It takes a bit of getting used to, and it takes a few passes to impress the thread to full depth, but you soon get the hang of it.
The problem with the spoke pattern is that there are three different lengths to cut per side (the Nexus 7 is highly offset). I tried calculating all the lengths, but kept getting the calculations wrong, so in the end I assembled the wheel with the radial spokes (left image), then measured the length of the next set of spokes to go on. This worked reasonably well.
As each set of spokes go in the wheel should be roughly trued. Here I employed a jig made from the rear forks of a skip recovered bicycle. The jig has the drop-outs with an adjustable gap which allows pretty much any bicycle wheel to be mounted on its hub and axle. The wheel can be spun, and any large deviations from true can be easily corrected from the inside.
Finally a DTI can be put to the rim to true up the wheel. I usually go for about 10 thou runout and concentricity if I can, although 40 thou would probably be fine. Bicycle wheels don't seem too critical.
|Its pretty much the same drill for the front wheel as the rear. Again the wheel is highly offset as it has the disk on it. I went for a cable operated disk for that long downwards hill on the way home. Many years ago I had a cable operated disk brake on a motorcycle, and it was rather unimpressive. The same is not true of the same setup on a bicycle. The brake is powerful and controllable, and just about right on this machine. I can unreservedly recommend disk brakes on bicycles.|
The original drive train was simply an extended chain. The heavier chains used in the 1960s seem to have had a greater resistance to lateral flexure. These days bicycle chains are lighter, and designed to flex their way around multiple chain wheels and sprockets in a derailier system. The consequence is that no modern bicycle chain will hang on, and as soon as I started to ride the thing it fell off repeatedly.
My solution was to use a lay shaft and run two chains. The problem was that the first chain needed a tensioning device, so I put it eccentric with the shaft about which the swinging arm rotates. Rotation of the swinging arm shaft tensions the first chain, then the rear dropouts tension the rear chain in the conventional manner. It is a bit of a fiddle to setup, and you have to leave a surprising amount of play in the chains to compensate for swinging arm movement, but once done it works well. It also allows you to gear the whole train up as the Nexus 7 is really designed for 26" wheels, and needs to be a bit higher as the box is on a 16" wheel.
The only problem so far has been the eccentric. Initially I didn't manage to get it strong enough, so it bent - image on left. It has been sorted by using a piece of EN45 as the eccentric plate. The two shafts are the same.
The chainguard is really worth having. I notice that manufacturers no longer fit them as standard, but if you ride daily without wanting to mess about with trouser clips and things chainguards are best.
|This Moulton feels pretty much like any other bicycle, and rides reasonably well. It has occasional problems with the complex chain arrangement, and some problems with rattles and uexpected sounds. The gears work well, although the Nexus 7 feels as though it has a loose bearing at the moment, and the front brake is brilliant. So far it is a decent commuting bicycle, and it is now at a suffient stage of completion to dismantle and do all the aesthetic bits. A new paint job, new bars, and tidy up some of the less good welds will be done in the next few months. I shall post new photographs then.|
The first bicycle I had at Lancaster was pulled off the metal scrap heap at North Berwick Recycling Centre. It was a men's mountain bike with a crossbar too high for my legs, worn out derailleur gears, and conventional bicycle brakes which use the wheel rims as a friction surface. The crossbar had obvious problems, I could only get about five gears from a potiential fifteen, and the brakes didn't work in the wet, which with the Lancashire weather was dangerous. I never took any photographs of it, but as soon as it became obvious that I would be cycling on a daily basis I went looking for a new bike.
What I wanted was a low crossbar, proper gears, and brakes which stood a chance in the rain. The lycra gussetted brigade who staff Lancaster's boutique bicycle shops seemed fixated on carbon fibre racing machines with derailleur gears, high crossbars, and brakes which acted on the wheel rims. I was told that a bicycle of my specification did not exist, and indeed could not exist. After pointing out that several perfectly good braking and gearing systems were availible for bicycles I was told that there was no demand for such abominations.
Finally I went to Halford's Bike Hut on the off chance they might have something sensible in. They did, only one mind, but something which fitted my specification. It was a Carrera Subway, and cost about £400 which is about the minimum for a worthwhile bike these days. It has a nice low crossbar, Shimano roller brakes, and a Shimano Nexus 8 speed gearbox on the back.
The only maintanance it had was the odd squirt of lubricant into the brakes and onto the chain, and the annual re-indexing of the gears, which was really easy. This bicycle was ridden everyday come rain or shine, and we get a lot of rain here, so I tended to use spray Waxoyl on anything likely to corrode. It looked terrible, and you didn't want to touch it, but the treatment worked really well. Occassionally I had to take apart the roller brakes, these are a bit of a job. Here is a reassembly guide.
Unfortunately this bicycle is no longer functioning. The Shimano Nexus 8 speed gearbox died on the very last day before the end of Michaelmas Term 2012. Apparently the Nexus 8 is prone to sudden failure. It has done five years of daily commuting, being left outside, and virtually no maintainance, so it has done reasonably well and I've been very happy with it. The Moulton is now my only functioning bicycle.