As the expression tells:
This is very often true in engineering and the apparent simplicity of bicycle mechanic hide a lot of difficulties, as I discovered making a bike prototype (which incidentally was the first bike I assembled, so there was some serious learning in the process).
- Units conversion
- Screw threads
- Ball bearings
- Brake cables.
- Dérailleur/chain tensioner installation.
- Bottom bracket crank connexion
- Gear hub shifting
- Shifter installation
- The handlebar
- Handlebar bracket
- Chain retainer
- Reversed brake lever ?
- Cable guiding wire
- Seat attach
- Bicycle computer
- Helmet mirror
- Handlebar mirror
- Chain guard
- Crank and pedals
- Bottom bracket
- Steering spring
- Wood inserts
- Rear wheel frame retainer
- Seat bag
- The shelter
- Rear light attach
- Shimano plug for hub dynamo
- Phone support
- Buying online
There never was ‘official’ standards for bike mechanic, so the standardisation came from large adoption of equipment by bicycle manufacturers, often because a technology had some advantages over others, and stuff was designed in France, Italy, UK, Japan, USA so the origin are mixed and you will find dimensions in imperial or in metric or weirdly, as for steering bearing, a mix of the two.
1 inch = 25.4 mm: inches are symbolised by “. Sometimes for dimensions in millimetre, there is no unit at all (it is common practice to use mm in mechanic, but the official international length unit is the meter).
1”1/8 = 28.6 mm – Steering tube
Hopefully, this is mechanic and not piping and the tubes dimensions in inches are the REAL dimensions (beware if you buy piping tubes, they obey to another standard, e.g. 1” tube is effectively 1.33” say 33.7 mm, that is the fun of piping engineering…)
1 pound = 454 g or 1kg = 2.204 pound
Nowadays, most bike screws are ISO compliant but you will still find english threads on bottom brackets caps and steering tube.
To save weight, it was the tradition in bike mechanics that the bearings were integral parts of the mechanical elements (for steering, wheels and bottom brackets), so for minor wear, you just replace the balls, for higher wear, you replace the whole parts. You find nowadays more use of standard ball bearings which in theory ease replacement, e.g. to replace the bottom bracket bearings, you just change the cartridge bearings (often completely standard bearings) without replacing the shaft and caps. Such bearings are smaller and may theoretically be less strong but there was significant improvement in standard bearing manufacturing over the last decades which help compensate. The problem is that rust may lock bearings on shaft and replacement may in practice be more difficult than the old traditional system.
I choose to use a fork with a 1”1/8 tube, which is quite uncommon for 20” wheel forks
A 1”1/8 fork tube (28.6 mm) does have the top tube of said diameter, but the low part of the tube is larger (to ease installation) and have a diameter of 30mm, mixing imperial and metric dimensions. I discovered it because the hole I did in my frame was just 30mm and so my steering had huge friction and the bike was very difficult to ride – and this was my first go on a recumbent!
Semi-integrated bearings are called ‘Zero Stack’, and the external bearing diameter may have different values, however by chance for 1”1/8 fork, it does only exist one external size, which is 44mm.
When you are not that versed in bike mechanic you may assume that a brake lever can replace another and they are standard. They are somewhat standard, but there are TWO standards, one for road brakes, the other for V-brakes and they are totally incompatible as for the same lever movement, a V-brake pull twice the length compared to a road brake. It does exist costly accessories multiplying the pull to use V-brakes with Road levers but that add complexity and shall be avoided.
I used V-brakes and ordered a complete brake kit. Commonly brake cable kit are supplied with two cables but only one housing to be cut to have one rear housing and one front housing. You bet it, with a LWB the available length is way insufficient to have both front and rear housing, so you have to supply at least one more housing and depending yout set, another cable. The most important brake on a LWB is the rear brake, as the front wheel tend to lock if braking hard. The rear brake housing is a bit longer than traditional front brake and so it is even more important that usual to use high quality cables and housing, either PTFE lined (cable or housing) or polished cables. And as always, only stainless steel cables shall be used, forget those cheap galvanised cables and beware to the diameter as some manufacturers save marginal money by reducing cable diameter. A good cable set may cost three to five times more than a cheap one, but this is important. Don’t forget than even if you are not much athletic, old and riding slowly and peacefully (me!), a recumbent is much more aerodynamic than an upright bike and you can reach speeds you never experienced before when going downhill, even for relatively moderate slopes. And you WILL do, because it’s fun on a recumbent! Think you’re on a roadster.
The above drive us to have a close look to rims. If you use V-brakes on a recumbent, your rims may experience more energy dissipation than you may be used to, so even if that weight slightly more, double walled rims shall be preferred.
Screws to attach dérailleur are metric, 10mm diameter but with fine thread, not standard M10 thread. Fine thread is very rare, so taps are only available from bicycle shops. But, as problems to attach a dérailleur are common, there is a simple solution, it does exist inserts which allow installing a dérailleur by simply drilling a hole diameter 12mm. Beware, theses inserts came in two widths, one for a 5mm thick support and the other for 6mm thick support. I bought mine for 7.5 Euros in a specialised shop which sent them through letter at very low shipping cost (2.5 euros).
The cottered pedal connexion have hopefully disappeared (they were not reliable and tend to un-tighten with time)
If we set apart electronic gear selection, on most geared hub gears are selected by pulling a cable of a given value, knowing that the pulling value difference between each gear varies with each gear and with the hub model, so the gear selector is specific for each hub gear. It is so imperative to have an indexation on the command. There is an exception to that, the Rohloff hub gears did have the indexation set on the hub itself and so the command is made by two pull-pull cables.
Due to the under-seat position of my handlebar, I choose to have the rotating shifter on top, with cable exiting on top and making a cable loop. There is no noticeable added friction and the thin gear cable can accept such curve (look the radius on the hub mechanism) but the housing was initially not very well maintained and was creating troubles. Gear cables are thin compared to brake cables and accept reduced radius bends without too much friction but it is anyway recommended to use low friction cables and housing (you can use polished cables and PTFE lined housing).
However, I did face some troubles. To have the cable not contacting hand and wrist, I give the rotary shifter an orientation with the cable output quite to the outside of the handlebar so the down part of the housing will be well placed between the wrist and torso. That had exposed the shifter to rough contacts either with the ground or with other bikes when parked. This have moved the shield and displaced the cable outside its plastic guide, creating very serious indexation problems, which can be very dangerous for a geared hub. So I installed a stronger screw to better maintain the shield and rotated the shifter to have the cable output less exposed (see photo with bike parked in its shelter). To maintain the cable in proper position, I had to build a housing maintainer, done with an aluminium strip 20×2 mm with a handlebar tightening screw size M4.
I searched for a long time what I can use for handlebar. I finally decided for a ‘U-bar’ and bought the largest I found. It occurs this also is the one with the longer side arms which is quite practical for accessories mount (computer and phone support). It is very light, made in aluminium and came from Metabike. It doesn’t look very sturdy. I thought initially that an under-seat handlebar not having to support rider weight will be submitted to very low loads. In practice, the loads may be higher than expected. You push it down when seating. When climbing, you tend to pull it strongly. You push it when doing hard brake. I also use it to lift the bike for manoeuvering. Metabike does not have the reputation to make strong parts and it may be the weakest part of the bike, which can be a problem for such a critical piece.
Another solution which I foresee was to use a beach cruiser handlebar. It may be less practical than the U-bar but you can find one in steel if strength is a concern (Ergotec sell one which weight 880g, this is really heavy. Width is 700mm). However, you may have to add small extensions to attach accessories.
A third option is to use a strong flat mountain bike handlebar with vertical aluminium extensions, but I did not find sufficiently long extensions, so you may have to build connections from aluminium block (a bit like what I did for the handlebar bracket (see below), but with bracket going inside the extension tube.
For ease of manufacturing the first bracket maintaining the handlebar and axis shaft was made from oak wood.
When folding the rear frame, the chain is no longer tensioned. To maintain it on rear sprocket, you need to pull the chain by more than 180mm. I was not capable to devise a system to pull such chain length but with a geared hub (say single speed sprocket), there is in fact no need, you just shall retain the chain on the idler and on the sprocket, chain will remain in place on the chainring by gravity. Yet only the idler retainer is installed but the sprocket retainer will be done similarly with folded aluminium strip (25×2 or 30×3 mm).
Due to the position of my handlebar, an ordinary brake lever will be reversed and I was very cautious about it and questioned myself if it will be a problem. I researched ‘reversed’ brake lever, they did exist but only for road bike brake, they are absolutely impossible to find with the ‘pull’ of a V-brake.
Due to the possibility to fold the rear wheel frame, it is not possible to attach the brake and gearhub cable housing, so they move and tend to touch the chain idler. So I made a wire loop in 2mm diameter stainless steel wire to avoid contact with the idler.
There ara two kind of seats, the rigid ones and the meshed seats. Rigid seats tend to have the user sweat when weather is hot, while mesh seat breathe more. However, you can install breathing “pads” sold under the name ‘Ventisit’ which are originally made to be set under mattress in boats. They are a bit aggressive for clothing and may drive to quick wear of your shirts and pants. Rigid seats made in carbon fiber can be very light.
The typical rigid based seat are the one sold by Rans, but it is very costly (500 USD) and Rans have no representative in Europe. Another one is the Bachetta ‘Recurve’ for 275 USD and may be a bit easier to import in Europe. Both seats looks very similar but you find on forum a lot of people who much prefer one or the other and you may organise an exchange fair…
I got the opportunity to buy a used Rans seat, but with a too thin cushion. The former owner did add ‘ventisit’ pads which improves the situation, but that is not sufficient for my taste. I did experienced some ‘Recumbutt’ at the beginning but this seems to reduce as I became more experienced (overall 800 km at time of writing).
The seat is an old Rans model for Stratus LWB bicycle.
Seat tend to slide on its support when pushing hard and the clamps shall be firmly screwed. You need to write position marks on the frame (beware, if your clamps are not perfectly symetrical, the marks are not at the same position on right and left). Gluing a rubber strip may help to have a better grip and protect the frame.
It is not very practical to remove the seat from its support for transport because when reinstalling it, nothing maintain the clamps and you need to guide them by hand. A maintaining spring may help to retain in place the clamps when the seat is removed.
I was willing to have a seat with a foldable back but this is quite complex to devise with the Rans seat as it does only have on attach on the bottom plate. So I am thinking to a wood frame based seat.
Because they are reliable and the battery last for years, I prefer wired computers. However, the wiring length for most brand is typically 80 cm (31”) , which was insufficient for my handlebar mount. With below seat handlebar, the sensor shall be installed on the rear wheel.
I was warned by forum threads that on a recumbent, mirrors are required because it is too difficult to rotate your body. No problem, I have a mirror on my upright bike so I am used to, while I still rotate head and body when possible.
Though, where to install the mirror? Some say that this is not OK on handlebar because it rotates. This argument doesn’t hold much value, this is the same on any upright bike.
There was some suggestions to use a helmet mirror. The mirror is very near your head and as I have not much optic knowledge, I was thinking the focus distance was the distance of the reflected objects, not the mirror distance. Though, it seems it doesn’t work like that and that you shall focus on the mirror, at less than 20cm, this is only for young people. For those over 40, have no hope, it will absolutely be impossible to focus and the image will be very fuzzy. Plus changing focus from 100m to 0.2m quickly is not that easy and create a significant and lengthy distraction. Maybe the problem is elsewhere and the brain is troubled between the mirror frame and the mirror glass but in any case, that simply absolutely don’t work (for me, at least).
Then I installed a Busch and Muller Cyclestar mirror on the top of my left handlebar (for right riding). This is a sturdy mirror with many mounting options. The mirror is small (65mm) but is is convex and the covered field is larger than you may think at first. It worked but I bought another one of the same model with a larger mirror of 80mm diameter. This is really much much better and I am now happy with this mirror (this mirror is also convex). The small mirror was not a loss, it changed place from the left to the right of the handlebar.
It is really needed to use a chain guard if you want to avoid trousers being catch in your chain-ring. Note that on a recumbent due to the horizontal position of your legs exposing them directly to sun, you may wear trousers instead of shorts more often than on an upright bike to limit sunburns.
On recumbent, it is preferable to use shorter crank arms. Typically, the crank length is around 150mm, but can be lower if you have short legs.
Excluding high end mountain bike standard, there are fundamentally three standard on traditional bottom Bracket, The French, Italian and British. Nowadays, The British standard have became the norm and we are referring to it as BSA (British standard association) threaded bottom bracket. Most common width is 68mm (could be larger for mountain bike), the thread of the right cap is left-handed, 24 TPI (thread per inch) with an internal diameter of 1.37”, say 0.945 thread per mm, internal diameter 34.8 mm. The thread of the left cap is right-handed.
Because they are unthreaded, it is difficult to disassemble bottom bracket caps, so I made a ejecting tool with a splitted tube. You also may need two bottom bracket tools instead of only one to disassemble because the BB may turn freely in its support.
To stabilize my steering and improve low speed handling, I installed a fork spring.
To be able to attach parts, luggage rack and other stuff, I used M5 wood insert. The cheapest model made in zinc alloy which can be screwed with an ‘Allen’ key is the most practical because it is easier to be maintained perpendicularly to the wood part when screwing it. All these inserts are first installed before part or frame assembly to create the wood thread, then removed and finally installed when the resin is still liquid and the holes are impregnated with resin prior to insert screwing.
I quickly discovered that it might be useful to lift the bike to displace it, but with the folding rear frame, the rear wheel remains on ground till a very high lift. So I made a rear frame retainer in 2mm diameter stainless steel wire.
On a recumbent, you can’t use a backpack to carry stuff as I do since I am biking.
To have a larger bag (18 liters to 25 liters), you need to buy a specialized seat bag for recumbent at a larger cost. However, all these bags are don on the back top which in my case might be conflicting with the rear light also located on top of seat back.
My seat (Rans) don’t have flag support and I devised a system based on folded aluminium flat bar pinched on seat side tube. Unfortunately this was not sufficiently strong and I lost (and never recovered) my flag the first time I used it. I then bought a Burley trailer flag support and a standard bike flag (most bike flags are all identical with glass fibre pole 6mm diameter and plastic junctions).
Shimano hub dynamo was delivered with the wheel with an installed plug and no manual.
To navigate with a smartphone, I initially installed a German made Busch and Muller plastic phone support. It was slipping in rotation on the handlebar so I added rubber but I finally replaced this plastic support by a very sturdy aluminium one (Chinese made…), though this new one does have less flexibility for positioning. I had to file the right bottom support to be able to plug a charger wire in the phone (I produce electricity from the hub dynamo and use a 5 Volt converter USB2BYK).
Many things on such prototype bike are difficult to find and you have not many options to buy stuff but go online. The big problem is the online documentation is often scarce and very basic information is missing. By example, for more than 2/3 of the product proposed on online shops, you will not find the weight which is a bit insane for bicycle parts. Even for a utility bike, you shall be cautious of the weight. An utility bike is heavier than a road bike, but that does not mean that you shall not take care of the weight.
I opened a thread about the wood version of the Velassi on the BentRiderOnline forum (often abbreviated in ‘BROL’)