Chassis construction
The most basic chassis style is generally constructed from 75mm x 25mm RHS welded in a ladder configuration similar to the original car. Chassis rails generally taper in at the front when viewed from the top, but this may also differ depending on your chosen design.
You may be limited on what thickness of RHS you can get, 1.6mm is generally available but 0.9mm is better as it is much lighter without sacrificing strength, it is however not as widely available in Australia. Alternate materials and construction techniques can be used but must maintain similar strength.
More complex chassis designs can be fabricated from scratch if desired. A commonly seen construction technique is to use profile cut steel welded together to mimic the actual tribute car chassis profile. You can also use wood. Many of the original CycleKarts used wooden chassis. Generally they were constructed from ash as this was lightweight and very strong. If you are considering building your chassis from wood a good tip is to make sure that the sections of wood that you use are free from knots.
Wheel / Hub selection
The ideal wheels are the trusty postie bike wheels as found on the CT90 and CT110. You want the 17" versions.
It's worth pointing out that Postie bikes have a pretty strong following in Australia so you may find that they get snapped up pretty quickly. It also means that there are quite a few shops and wrecking yards that support them too. Reproduction wheels are also available but there are variations in quality (and strength) so make sure that you undertake some due diligence before purchasing.
There are also 17" pit bike wheels available online that generally come complete with tyres and inner-tubes which can be a good cost effective alternative, however the same quality considerations apply
The wheels are mounted to flanged hubs. Most builders in the US use universal go-kart / ATV hubs like the ones sold by Akuza Here . These are available in a 3 bolt and 4 bolt pattern. The wheels are drilled to accept the bolt pattern of the hub and bolted in place with a plate on the outside to sandwich the wheel hub in between. Ideally the hubs should sit snug inside the wheel hub recess to maximise strength. Where possible axles should pass all the way through the wheel hub to provide maximum support.
Traditionally the rear axle has one driven wheel and one free wheel. The driven wheel is keyed to the axle whereas the free wheel is not and is simply allowed to rotate about the shaft (with the aid of a little grease). Some builders elect to key both wheels when racing on loose surfaces, with one key easily removable for tarmac racing.
The front wheels are mounted onto hubs and have bearings within them.
Steering / Front Axle
The front steering is a very basic go-kart style that in its simplest form uses a lever arm at the bottom of the steering column to operate tie-rods that turn the front spindles. You can also use the rack and pinion style steering setups used on go-karts
The front spindles can either be made, or purchased and are mounted to a beam axle suspended from horse buggy cart seat springs. The size of the horse buggy seat springs is 610mm (24") X 30mm leaf 1/2 elliptics in 5mm thickness.
The front axle is made from 42mm O.D. tubing, and is dropped in the centre to accommodate the leaf springs. This can be easily done if you have access to a pipe bender or your local exhaust shop should be able to make up a part for you. An alternative is to use industrial handrail end loops, also known as a 'closure bend'. This provides a ready made bend that can be used. One closure bend will make one axle when cut in half and welded together. You can purchase these from safety shops.
So far we have not managed to find a source for horse buggy cart seat springs here in Australia. Generally regular trailer springs are way too heavy and stiff. The front end of a Cyclekart is very light and not enough to actually deflect a trailer spring. Otherwise you will need to purchase from the US, or get creative. Often batches of springs are made by CycleKart enthusiasts in the US and UK.
We are trying to find a local, manufacturer to make some for us but most auto spring makers don't deal with the thinner metal that is required.
Brakes
Brakes are a go-kart disc brake(s) fitted to the driven rear wheel(s) / axle only (no front brakes). These are available in both cable and hydraulic versions
Additional front braking is not allowed.
Drivetrain
The motor used is a 200cc, single cylinder, 6.5 hp Honda OHV engine (the GX200). There are various clones / copies of this engine available and it is commonly available as a small stationary / industrial engine in Farm equipment outlets. You can also buy them very cheaply online from China.
The motor is connected to the rear axle via a go-kart style torque converter and clutch arrangement by a chain drive. The drive ratio is 72 tooth main sprocket with a #40 chain
The torque converter arrangement commonly used is a Comet TAV-30 unit. There are various clone versions available online. You need to make sure that the unit you choose matches the output shaft size of your engine (generally 19mm or 3/4")
Alternatively an electric motor may be used in place of the GX200 provided that it does not exceed 48v / 3kW
Bodywork
The bodywork can be made from whatever you want, in whatever fashion you feel like or are capable of making. From the traditional Stevenson style basic square box plywood designs to more fancy and flowing renditions of your favourite 1920's cyclecar in hand formed aluminium. The choice is yours.
Generally the base of the seat extends below the chassis rails so that you sit lower in the car, this also helps to keep the centre of gravity low, which makes the car more stable. Take a look through the 'Inspiration' photo album to get some ideas. A Google search for 'CycleKarts' will also get a bunch of results too.
Shopping List
We've created a bit of a basic shopping list that will give you an idea of the components you will need. We recommend that you shop around to get the best price but it should give you an idea of what to search for. You can view it on the Parts sources page
Happy Cyclekarting !