For years now I've been cycling to work in the summer months. It doesn't necessarily save any money, but it reduces my carbon footprint & gives me exercise. Being me, I can't simply buy a bicycle - where's the fun in that? Below is some data about the bikes I've built.
Local bike shops
I have a weird sort of love/hate relationship with bike shops. This has got much better of late - I let them talk all the patronising horsepoo, smile & thank them, buy the bits I need & then do the work myself (I particularly love being patronised by snotty nosed hippies..). My local shop in knutsford is actually pretty good - the chap there is an 'old head' who's helpful & able & can usually help me out with unusual services or components. But he's tied to particular suppliers so, for example, could not get the spokes needed for a wheel build for me. After 3 weeks I got the parts back from him, ordered the spokes on the internet & built the wheel myself the next day. The shop in Congleton can be good & cheap for new stuff and have been helpful recently. But in the past they have also done what I'd call dirty tricks (quoted one price to get the order but then tried to charge nearly £50 more!) so I'm always very on my guard when buying from them.
On the internet, I've used all the big name suppliers; these days I seem to mostly use chainreaction & SJS. Both these seem to be good value & be able to get stuff to your house the next day, which is outstanding service!
Internal Hub Gears
Since working on the greenpower electric cars, I've become a fan of the internal geared hubs. There are a few modern makes; the important ones are SRAM Rohloff and of course Shimano. All my bikes currently sport shimano 8 speed hubs, but I'll probably upgrade to an 11 speed on the road bike during the year. I think SRAM & Shimano offerings are pretty similar, but the Rohloff is the daddy - massive gear range, 14 speeds & even 13.6% gearing steps. Price well over £1000 - that would buy you 8 nexus 8 speed hubs! So why would a hub gear preferred to a derailleur?
1) simple chain line - one crank sprocket IN LINE with one sprocket on wheel.
2) gears all protected; system is reliable and maintenance & trouble free.
3) if I'm stationary in top gear & need to select 1st before setting off - I can.
Of course a derailleur also has its advantages:
1) weight - the hub gear is a 1.6kg lump in the middle of the back wheel. It does alter the weight distribution and feel of a bike. Total weight is not that much different however.
2) efficiency - there's no getting away from this. With a hub gear you will be working about 5% harder (c.f. a derailleur system in good condition). If you were racing there is no way you'd consider a hub gear.
My Road Bike
This came about when I managed to get an aluminium frame off ebay for £30. I'd long wanted to build up a road bike using one of the modern internal geared hubs that we used in the greenpower cars. I got a carbon set of forks for £40 and some ebay shimano 105 brakes for £18. Ebay also supplied a second hand handlebar stem for £40 (ouch).
Gear changer mounting: The nexus twist grip gear changer is mounted on an aluminium "mini handlebar" which I turned up and bolted to the handlebar stem. It wouldn't go on the handlebars themselves because of the bends and the thickness change in the middle. It has taken a while to get used to this (I'd previously had STI shifters). I tried to modify some STI brake levers to try to use with the hub gear but it just did not work. To get the right index spacing I had to put a ratio changer in the cable, so in the end the whole system was simply not precise enough to work the gear hub. Plus the STI shifters seem to have been engineered to "overshoot" in the direction of travel.
Chain Tensioner: The frame has vertical dropouts. SO - 2 options for tensioning the chain; eccentric bottom bracket, or a chain tensioner. An eccentric bottom bracket IS avaiable, but it's very pricey & has limited adjustment range. Chain tensioners are available cheaply enough, but ruin the simplicity and efficiency of the chain line. The final alternative is to run with a slack chain. I suspect this latter option would swiftly result in the chain jumping or coming off, so I put a cheap tensioner on.
Back wheel woes: I first built the bike up with a nexus red band hub. I got my local bike shop to build the wheel. It was laced 4 cross, because of their "spoke availability" issues. This wheel worked pretty well for a couple of years - I had it trued & a couple of spokes snapped, but mostly it was good.
Then I got a new "Alfine" hub. I replaced this in the wheel, used the nexus on my folder. I built up the wheel myself in the "snowflake" lacing pattern. And the spoke breakages started (more than 1 per 100 miles). So I relaced the wheel with a conventional 3 cross pattern. The spoke breakages continued. OK I'm a big bloke and the roads round here are full of potholes - but still, this is too many spokes snapping.
Finally someone pointed out - I'd laced it with the rim holes out of step - putting too large a bend on the spoke where it exited the nipple. So - relaced again, this time spokes on the right sides and laced with a 1 cross pattern. Ahh - at last - I've ridden a whole season with no breakages.... I'd still like to make a snowflake pattern wheel one day - maybe when I electrify my daughter's bike...
Overall: it's been a good bike, there's a few thousand miles on it now. The hub gears have been utterly reliable & actually loosen up when run in. I look forward to the ride home (15 miles of cheshire countryside) 3 days a week. It is surprising how infrequently it actually rains! I only get a couple of good "wettings" per year cycling throughout the summer months
My Folder: Raleigh 20 "stowaway"
I wanted a bike for hacking around town & to be able to put in the boot of the car (so I could cycle to work from the garage when the car needed fixing). I'd heard good things about the old raleigh 20 folders, the late Sheldon Brown (no less) said they were a favourite - when modified by putting more modern running gear on.... I bought one on ebay for £20. I was given some rims & used the old red band nexus 8spd hub gear off my road bike. I got some shimano 105 brake calipers again off ebay(£23), though I had to make brackets to space these correctly for the wheels (the original pressed steel brakes were huge things to go over balloon tyres), and I fitted a new bottom bracket with the square taper cotterless cranks (I had to remake the thread on this to make it fit the raleigh frame). I got a new mountain bike seat stem & cheap road bike saddle (Aldi - £6).
The result is a really nice bike, not very compact when folded, but goes easily in the boot of the car. It rides superbly, very rigid frame & quite efficient on 1-1/8" tyres. The nexus 8 gear system is utterly bomb proof & trouble free, and the chain guard means I don't have to mess with cycle clips or tucking trousers into socks. Unfortunately the frame is a slightly effete pinky purple colour so I get some stick ;^). Maybe I'll give the frame a lick of paint one year - black I think.
Electrifying a bike
I'm doing this project with my nephew Matt & brother Bill. If it works well, they might consider putting some sort of kit together. The plan is this:
1) use a BLDC outrunner motor for model planes: these are light, cheap, powerful and efficient
2) drive back wheel via a L.H thread freewheel on the other side of the rear hub to the normal derailleur block/cassette.
3) motor sits on seat stem with chain drive to wheel.
4) batteries are lithium polymer "pouch" cells (again from model plane world) in a saddle bag.
5) use commercial RC ESC (electronic speed controller) driven via a "servo tester" and handlebar twist grip.
Thinking about the kit aspect - there are so many ways for a customer to make a complete horlicks of the electrical side (including the lipolys doing the fireball thing, squashing their seat stems, chains coming off or snapping or folk getting parts of their body stuck in them, motors burning out, magnets coming off - the list goes on and on...) it might make more sense to supply a mechanical kit & let folk do their own electrical installation.
For a commercial kit, we'd have to target a smaller motor, e.g. there's a 470W outrunner on HobbyKing for just $14. This spins a bit fast (14krpm) so I'd propose primary 10:1 reduction via a small steel pinion on the motor driving a plastic gear on the layshaft. But, lets get the prototype going first!
Prototype electric mountain bike
Initial prototype will use various bits & pieces I had lying around. The motor is way too powerful - it's a 3kW outrunner. The ESC is a 50A/20V one, much too small for the motor, & I have a couple of 3S lipolys 2.2Ah 20C (i.e. good for 40A for 3 minutes.....) It will be interesting to see how it performs!
Gearing: The motor is good for 8000rpm, but with 20V available and kV = 200 I should get 4000rpm. I have geared 25:1 (5:1 from motor to layshaft and 5:1 from there to back wheel) which is 160 rpm at the wheel. The wheel is about 2m circumference so that's 320m per minute or 19.2kph, 12mph. So it probably needs gearing up a bit more - we'll see.
I put the electrics all together this lunchtime; the ESC did its "customisation" thing & then ran reasonably nicely - no smoke escaped, whole system operating; batteries, ESC, servo tester gizmo, motor. I reckon I'll have to make a wee circuit to power up and control the ESC (the servo tester gizmo is not a complete solution - it also needs a wee power supply). I looked up the servo interface & it looks like I can do something with a LM317 and a 555 timer. The 555 output is upside down so I'll have to stick a logic inverter on there too. A job for tomorrow lunchtime.
I made the main part of the drive yesterday, used a fly cutter on the lathe to make a nice plate to clamp on the seat stem. Now I have to taper two sprocket bosses to bolt on the ends of the 12mm layshaft & bingo, we'll be mobile. I asked Matt to get hold of a cheap cycle computer - when it's together I want to run it at 12mph on the level & see how long it takes to flatten the 2 batteries I've already got. I reckon they might be good for 6 miles or so.
The pictures show 1) the compression joint on the motor shaft, 2) the motor/layshaft module which will clamp onto the seat stem, 3) 2 batteries and a speed controller, 4) the left hand thread for a freewheel replacing the brake disc mounting on a hub built into a MTB wheel.
OK reality check: the handlebar twist grip is a "non-contact" design and therefore not a simple potentiometer. On test it appears to accept 5V power supply and output 100mV (throttle off) to 400mV (max power). This alters the design for the servo interface (which is 920us pulse [off] to 2120us pulse[full] every 20ms). Considering the motor speed controller output; it appears to drive motor current proportional to demand - which translates to torque control - excellent!
I finally got the sprockets from the laser cutters today. The 8mm one mounts nicely on the freewheel on the left side of the back wheel. The 6mm one fits on the layshaft as shown in the pictures. I actually have everything needed to get the bike mobile tomorrow (let's see how we get on...)
Well, I got the wheels turning but not exactly mobile:- too many things not quite actually operative for that; both wheels punctured (the front several times) and all the gear cables rusted. The frame is JUST big enough but it means there is no chain adjustment (I'll have to rig a tensionser)
1 week later..... We ran the bike today. First up, I spent some time knocking up a circuit to let the twist grip control the ESC, its a pretty simple circuit with 2 555 timers and a 317 voltage regulator; I'll put a schematic on here - easy enough to bash together on some veroboard. I used tome ancient RS components 555 demo boards which we unaccountably still had in stores at work! The first 555 is configured as an astable to provide a trigger pulse every 20ms, and the 2nd 555 uses the voltage output by the throttle twist grip to vary the pulse width of a monostable circuit from 1ms to 2ms. The 317 supplies 5V for the 555s, the twist grip and the ESC. It seems to take 12mA or so, so it stays cool.
I got a new derailleur cable and a chain tensioner from chainreaction, and duly adorned the bike with them, then started gaffer taping the various electrical bits to the frame. I'd had to make a new roller for the chain tensioner (out of nylon) as the stock item was 1/2" chain only. With the batteries finally connected, we got the beep - beep from the motor & twisted the throttle. The motor of course went backwards.... so we swapped 2 wires, pumped the back tyre up (It still had a slow puncture) and went for a ride! Impressions.... surprisingly good, brilliant in fact; smooth, quiet(ish) and no hints of any mechanical issues like chains slipping or anything, and good acceleration to 12mph as expected.
Would it take Matt up the 1 in 7 hill? yes it would. He took it up the hill a couple of times then along the more level road for a few hundred yards and back up the hill to the forge. Nothing was hot so I took it the better part of a mile along the road and back. By this time the rear was fairly flat and it couldn't pull my immense bulk up the hill. But - not bad for first time out and little 2.2Ah batteries. Next my brother Bill had a ride but the thing suddenly slowed a lot; - contrary to expectation the ESC had kept going when the battery voltage reduced leading to an over-discharge of one of the batteries (it was down at 6.7V compared with over 10 on the other one) and quite an alarming swelling of the side of the battery. Oops - $8 down the pan - never mind, here was a golden opportunity to see just how volatile and dangerous the li-poly batteries are; and what a lithium fire was like! So I attacked the battery with an axe. Again, contrary to expectation, there was no fire, no smoke, not even any discernable heating over several hours. I'll get Matt to overcharge it next week with a car battery charger & see what it takes to get one to spontaneously combust. I'd been assured that a small puncture would cause a fireball - maybe the batteries have to be charged for that to happen? Maybe these Turnigy batteries don't have the fireball characteristics? We'll see ;^)
You can see the installation in the pictures above, it's a tatty old 'rat' bike, I'm actually quite pleased with how it's all turned out, it's pretty neat and feels rock solid. Matt has some jobs for next week; fix the front deraillieur cable, fix the rear puncture, buy some bigger (5Ahr) batteries and a bigger ESC, adjust and fix the chain tensioner; then he should be ready to tackle Pendle Hill (maybe a rear mudguard would be nice to try to keep the road filth off the motor...)
OK the new ESC arrived; a 100A Turnigy Super Brain (!). The larger 5Ah batteries and the new controller work rather well. A Battery holder has been attatched to the drinks holder bolts and a big isolator switch added (also a small precharge switch and resistor to look after the big switch). The only issue is that the pillow block bearings seem to have come loose, allowing the layshaft to rock from side to side; - they'll have to be shimmed. The larger ESC showed a tendency to loose synch when taking up drive. We experimented with all the "beep codes" to try to make it better, altering the timing and the PRF, but the only thing that made a significant improvement was enabling the soft start. However, the soft start suits the bike very well and it starts and goes quite happily with me on it now.
For me: electric trailer for the folder
In order to make an electric bike - I didn't want to add all the weight to my road bike, and anyway it would not be a comfortable bike for electric cruising. And I didn't want the weight of the electric gubbins on my folder all the time either. The surprising answer might be to put the battery, motor and drive onto a trailer! So I'm going to make a one wheeled electric trailer for my folder.
1 16" wheel so it pushes straight & transmission is easy
use a steering column universal joint as the hitch - lets the trailer move side to side or up & down, but won't let it fall over
use a QR skewer on the UJ pinch bolt
use SLA batteries - cheap & the weight aids traction.
Most single wheel trailers use what's called a BOB hitch it clips on the bike back axle to pivot up/down and allows side/side movement by a pivot behind the back wheel. I found out about these after I started but I still think mine is a better system: 1) less bulky 2)with BOB system the sideways pivot must be much closer to the trailer wheel so it might be twitchy (very short trailer) 3) the hitch point height means that the tractive force is pushing the drive wheel harder onto the road.
With the success of the mountain bike drive, I'm using a RC outrunner motor, and RC ESC. I've ordered a 500W outrunner from hobbyking for $15, it's tiny but should give fairly good hill climbing ability at the 15mph max. speed. I'm going to use steel & delrin gears for the primary reduction - let's see how that holds up!
The pictures show the assembled frame and the trailer hitch part on the bike. I got a hub from chainreaction for £12 and have turned a freewheel thread on it.
I got a 1/2" sprocket laser cut and have bolted this onto the freewheel and ordered spokes, rim, tube, rim tape, schwalbe marathon tyre. I fit the hall effect throttle on the bike - this does get in the way of the gear lever/button a bit but I can live with it. So now I'm waiting for all the stuff I ordered from the far east, spokes, motor - of course it's chinese new year... I got some cyclic SLA batteries on order through Greenpower for £27 each, 2 off 20Ah. That's 480Wh of go juice. I believe an ebike uses about 150W at 15mph - which would be 3hrs, x 15mph = 45 miles. Interesting - should get me to work and home again with plenty of spare!
Just to make it extra crazy I spent £110 on 2x 20W solar panels. I mean to set these up as battery chargers. While riding they will be set up like a tent over the top of the trailer, but when I stop I can flip one of the sides up to make a 40W array all pointing south. Note that 4hrs of sunshine will put back all the electric I used going to work so hopefully I'll never have to bother with battery charging. Initially I'll just make a simple shunt regulator charger, but eventually I'll do a farty one with maximum power point tracking... when I have time....
OK - wheel is built (after a false start due to buying a rim with the wrong number of holes) laced X2 using 147mm spokes. Jackshaft is made and installed and the motor is here; I just need to make a motor bracket & that's the hardware complete.
Several weeks later and the ESC has still not arrived from HobbyKing. The motor is on, the batteries in place and most of the wiring done.
Long delay: - the ESC arrived, trailer wired up & tried. Immediate problem - it was geared way too fast. The motor kV was considerably higher than I was expecting & the high gearing meant that the drive was continually bogged down, overheating the motor and ESC. So I remade the layshaft sprocket to 11 teeth. First journey, went OK but the thing was bouncy and noisy. Bounciness reduced by letting lots of air out of the tyre. Noise: grin and bear it. Here is a video of it in action
The QR skewer trailer hitch clamp was not a success and replaced on the combination's second outing with a M8 fine bolt. This was more like a proper disaster, because the stainless steel nut had given the impression of tightening when in fact it had spalled, welding itself to the bolt and leaving the clamp loose. The loose clamp meant that the trailer developed quite ridiculous torsional oscillations under power - you could really feel it on the bike. At the destination I tried to remove the pinch bolt. NO chance, eventually I had to hacksaw the bolt head off with a junior hacksaw. So the trailer came home again in the back of my car. Third outing - this time with a new hitch pinch bolt, properly tightened.... Arrived at destination without incident. On the way home I noted that the torsional oscillation had returned, then the trailer fell over to one side as the trailer hitch failed. This was bad news - it was late at night, I was a mile from home with an utterly unmanageable bike and trailer connected by a broken hitch. I got them separated, cycled home then went to get the trailer in the car. Again. Since then I've fixed the hitch (welded on both sides now). I also bent the long hitch arm on the trailer so it is less close to the tyre and the UJ is not near its angle limit. These measures should fix the hitch issues. I might make an ally box to protect the gears and keep some of the noise in, although the noise has actually reduced significantly over the first 10 or 15 miles.
Appraisal of the trailer solution: to be honest it's not very good. The motor is too small so it's slow and a long hill would kill it. The trailer bounces on anything but a billiard table smooth road (and they don't exist). It has had a couple of problems but I put those down to normal teething issues.
Electric bike for me
Matt's bike is so good I decided to make one for myself ;^) Another reason for this is that I wanted to try a 2 speed gearbox idea where the primary drive to the layshaft is via a chain AND a pair of spur gears. These are both on sprag clutch bearings on the layshaft so reversing the motor will select one or the other. The installation should be almost as neat as Matt's, and not much more expensive: the extra expense is a reversing switch (£30), 2 sprag clutches (£30) and a pair of gears (say £40). So it's an extra hundred quid but I hope the benefits of gearing will make it that much better.
I've started converting my daughter's bike (which she never uses). It will cost about £300 in parts plus all the bits I will make or machine. I've already rebuilt the back wheel with a LH thread for a southpaw freewheel and a 7 gear cassette, and a 7 speed gear selector to suit.
I used the same system to put this drive together as I did with Matt's; a circular groove cut into a piece of 10mm thick ally plate to clamp the seat stay & everything bolts to the plate. It's a simple, effective and reasonably lightweight solution. I used an old Towerpro outrunner motor I had lying around. While I was making this I noted that Matt's bike primary chain was spinning so fast it had thrown out all its lubricant and was now really quite stiff. So I changed the design to toothed belt. First belt was HTD, 3mm pitch, 9mm wide. This actually worked for a short while but suffered increasingly from the belt skipping on full power. Now with 5mm HTD belt and larger radius pulleys it should be much better (I hope).
First picture shows electrical installation with reverse switch and power switch on the triangular panel and the batteries bolted to the drinks holder bolts. The second shows some of the wiring and motor assembly.
With a belt tensioner installed (see photo 3 above) the bike was "complete" & I tried it out running up the hill outside the Forge. It ran beautifully (if a little noisily), easily coping with the hill. Then suddenly drive failed on low gear. This seems to be a failure of the sprag clutch. I'll order a replacement and (at the same time) get a smaller sprocket on the back wheel for higher speed cruising. "endless sphere"'s "miles" came up with a torque spec for the clutch of 7.5Nm continuous with 2.5x overload. Now with my motor and reduction, the low gear is hitting it with 14.4Nm - so that would explain the failure. I'll replace it for now and look into whether there's room to re-engineer for a larger sprag (say 15mm) - might be possible.... I'm quite pleased with the overall neat and compact installation in photo3
I tested the range of the bike the other day - 4.4 miles on full chat. I will replace the knobbly tyres & repeat the test, (hopefully getting up past 5 miles) and to this end I've ordered 2 michelin slicks for it AND another 5Ah 6s lipo battery - I'll get to work on this thing yet!!! The bike is nice, quiet & civilised to ride.
Here's a vid of an ebike ride in knutsford.
I put slick tyres on the bike & the range went up to 4.8miles. I've bought another battery (should have bought 2....) and am making a double extra battery box to take the range up to 14 miles or so. The bike is feeling very solid now (apart from - on picture 3 above you can see I don't have an HTD belt, I have a 5mm pitch synchroflex instead - upshot is that I can't use full power in top...... I MUST source a proper HTD belt.....). I've done 30 miles or so on it now.
This is looking like a good way of converting a bike for RC motor use; the stock drivetrain (pedals deraillieur) is retained complete. The electric drive goes to the left of the back wheel via a freewheel on the wheel, so it wastes no (human) power when under pedal power. The reverse-select 2 speed transmission is simple and robust and uses just a few special parts, which are easily made on the lathe.
250 miles on it now: I had to replace the other 12mm sprag. I put 15Ah of LiPo on it and was able to commute to work on electric power (just) so I upped it again to 20Ah. Unfortunately winter use has killed the controller (no surprise there really) so I've ordered a new one - dear me $12.......
A year down the line.... The bike is still going strong. One cell of lipo has died so I replaced a 6s brick with 2 3s bricks (which I already had) - probably a better plan if cells just roll over like that. I took off the lower gear - I never used it, it made a lot of noise & wasted energy. The single gear is easily torquey enough to get me up any of the hills I ride.
Regarding legality - when the batteries are full, this bike exceeds the maximum speed limit (15.6mph) and when it's going uphill it exceeds the power limit (200/250W) So I'm making a small board to replace the control board which currently sits between hall throttle and ESC. This new board is smaller & has a speed and battery current sensor on. It should improve throttle feel as well as making the bike completely UK/EU legal. I will publish the design of this board on endless sphere, including the software. It looks as though it should be very cheap to make in quantity, less than £1, but at prototype quantities it's more like a tenner.
Electric bike drive through the gears
There are 2 ways of approaching bike electrification. 1) no gears. If you have a sufficiently powerful motor this can go up hills and reach reasonable speeds on the flat. But legally you're only allowed 200W. Without sufficient power you can only assist on hills or against the wind. With gears you can use the available 200w in all circumstances. You can have independent gearing systems for the electrical drivetrain (e.g. my 2 speed setup above) or use the gears already on the bike. The problem with this last approach is the need to take the motor speed (many thousands of rpm) down to pedal/ crank speeds (100rpm). One way of doing this is to use a harmonic gearbox. Having thought of the idea of using a chain type harmonic gearbox for ebike purposes, I just had to make one... I'll fit this to Rich's recumbent bike over the next few weeks.
No progress on this - the simpler and easier LHS drive above does all you need with much less expense and difficulty.
New Road bike
My old road bike has done a few thousand miles now - say 5000 - so, prompted by finding an 11speed alfine hub on the 'net for £300, I've started a new build. I bought an alloy fixie frame off ebay for £80 and some carbon forks from SJS (made by cannondale, no less) for £60. I am going to make it belt drive: I'll use the gates carbon belt and laser cut my own pulleys (sprockets) using the schlumpf system. The belt drive system has lots going for it but allegedly can skip when a heavy brute (e.g. me) stands on the pedals: to mitigate against this I'll use as large a sprocket set as I can and perhaps engineer an idler bearing to press the belt into its sprocket teeth where it joins the pulley on the wheel - dead easy to do (why doesn't everyone do it?) but not really necessary I don't think. I'll document on here as I go on - I think the belt drive system will be really interesting. As will seeing what ebay thinks my old bike is worth.. ;^)
I made 3 trial pulleys, differing amounts under PCD size. I also took a photomicrograph of the belt in order to best measure its geometry. All my "trial" pulleys were too big: examination and measurement of the belt picture suggests that the outside of the pulley should be 0.9mm below PCD size. By the way, the belt cost £74; the only way I could get one in UK was as a spare for a commercially available belt drive bike.
While I'm spending small fortunes: I bought a versa STI type shifter/brake lever for the alfine11 from the states (£162) and a brooks B17 black leather saddle (£52). I got a shimano deore hollowtech 2 crankset for £50 ish (I should get something back on ebay for the chainrings which I'll never use), a stem & handlebars for £13 each, and some mountainbike SPD pedals and tiagra double lever brake calipers (I needed long drop ones). So the only outstanding item is a seatpost for £18. Oh yes, I had to build up the wheels: that's 2 rims at £20 each and 2 set of spokes at £17 each. I make that just under a grand - by far the most expensive bike I've ever owned. It had better be good!
The frame has been cut to split the rear triangle and allow belt installation - this turned out pretty neat and should be plenty strong enough. When I've got the pulleys together I will work out dimensions for some stainless "non-turn" torque plates that will double as belt tensioners and hold the bearing that ensures the belt can't skip (it turns out these are not new and are called "snubbers").
OK, the bike is together now and is frankly a lovely ride - the brooks saddle is nice already (before "breaking in"), the alfine 11 + versa shifter seem to work beautifully, and the belt drive is magic carpet smooth. But I've only done about 5 miles.... When the clocks go back I'll start commuting & put some serious miles in.
Now after 1500 miles - the transmission has been a complete success - no issues at all & still as smooth & quiet as new. It has never skipped a tooth on the belt or a cog in the gear hub. There were a couple of "early life" issues with the rest of the bike: a crank arm fell off (literally - while I was riding...) so I now know how to correctly fit hollowtech II cranks. And the steering seized up, due to corrosion after a mistake in assembly - that was another interesting 'moment' I can tell you! The alfine 11 has been rock solid. A lot of folk seem to struggle with these, but mine's been perfect. Still no need for a snubber wheel.
Electric Trike design and build 1/3/13
The greenpower racecar that the Sandbach high school team race goes 122 miles at 30+mph on 20p worth of electricity. Compare that (it costs 0.16p/mile) with a petrol car (say 18p/mile) diesel car (say 12p/mile). Furthermore there's no tax, MOT, insurance and all the ancillary costs associated with motoring; so running such a machine at 15.6mph (for legal reasons we will come on to) we have a running cost reduction factor of over 100. That's how I want to commute.
And it's all possible and legal right now. If I make a recumbent tadpole trike and add electric assist I have a street legal vehicle which meets all those criteria. Looks like Mr Sinclair's C5 was a few decades ahead of its time....
OK - to details. It has to be open cockpit (windscreen = need for wipers, defrost, demist, glass - not practical).
Problem 2 - my feet are well over 340mm long. If these are on 170mm long cranks - I need a front faired box for my feet 700mm high (+ clearance on the inside) My eyes have to be safely above this so that I can see the road... oh dear, it's all getting high & unstable (not to mention ugly) And I want a fairing, 1) for aerodynamics and 2) to keep me warm/dry/clean. Solution - replace the cranks with treadles - this takes 300mm off the height of the front of the fairing.
This is starting to look as though it solves a lot of problems - you won't get cold (you can always pedal a bit to warm up), you won't get hot & sweaty (electric assist), you won't get wet through (fairing), you'll be aerodynamically efficient (fairing and recumbent position), you have no extra costs and very low direct costs. Better make one!
Final note - I want suspension on this. It's not for comfort, it's from experience with greenpower racing where we have no suspension - the cars need constant maintenance because they get shaken around so much. This will use rather greenpower- like technology, so I'll put some suspension on there to protect the main vehicle. I figure I'll make the front pair of wheels move up & down together (i.e. completely stiff in roll) so that steering links are simplified and (of course) the vehicle won't roll in corners...
1/3/13 - I've built the rear wheel - I took a shimano MTB discbraked bub & turned down the disc mounting toscrew a lefthand thread freewheel on. The electric drive sprocket is bolted to the freewheel. I got a load of stainless parts laser cut for the treadle system. I now have to buy some stainless tube & make the treadle unit. The treadles are connected by chains on ratchets; I've made the sprockets eccentric so it "gears up" as the pedals approach the end of the stroke - I'm hoping this will give improved feel & stop me from clattering the treadles against the end stops.