Axles, suspension and gearbox
We have been riding full of suspended trikes and quads for almost 20 years, but 50 mm travel is often already sufficient. Some solutions have even yielded up to 100 mm of travel. The 24" wheel has proven to be the optimum between size and rolling resistance. Since all trike models should be below 1.00 m in width, the installation space on the front axle becomes scarce, even if the hand drive is also added. Suspension and wheel suspension should therefore fit in this.
a) Trike with two front wheels
The simplest type of suspension can be realized with a rubber buffer (approx. 50 mm diameter). However, the buffer has only one suspension travel of typical +- 10 mm, so that it has to be installed with a lever extension of about 1:4 in order to reach a travel and more on about 50 mm. Even greater forces occur in the lever mechanism, so that it must be sufficiently stable. However, the whole can be integrated compactly into the frame of a truike.
A "Mc Pherson" wheel suspension recreated with the car shows the next photo. For this purpose, one half of an MTB teletype forklift with about 60 mm of suspension travel was converted so that it leads the front bearing and thus the front wheel together with a steering knuckle below.
With a trike with just one rear wheel, almost everything from commercially available bicycle parts in the rear axle can be realized. A swingarm made of a spring-loaded 26" MTB, for example, is attached to the trike frame including the swing bearing. Instead of the original shock absorber from the MTB, two rubber buffers were installed in diameter about 50 mm below the seat level against the frame. This means that the rear wheel achieves a travel of about 80 mm due to the lever conditions achieved in this way.
A modern 10- or 11- gear chain shift then offers enough gear ratio with low weight.
Front wheel with rubber buffer suspension and 24" wheel
Front wheel with "Mc Pherson" wheel suspension from a half teletype forklift
26" rear wheel with swingarm and rubber buffer suspension
b) Trike with two rear wheels
A trike with only one front wheel can easily be realized on the basis of a 20" wheel in a corresponding teletype fork (50 mm travel at 50 kg load). To ensure that the tangle's front zone is easy to see, only a 20" bike is used here. We use a mechanical cantilever brake, which also serves as a parking brake when parking. A hub dynamo can also be integrated to supply the trike with luminous flux.
To keep the rolling resistance of the wheels of the rear axle small, a rigid but spring-loaded rear axle is used. On a triangular axle frame, which is centrally located on the frame with an articulated head and is guided by a Panhardt rod, a special differential gear system sits to drive the two wheel axles. It has a typical 9-speed pinion set (e.g. 11 to 33 teeth with freewheel ). The chain is placed on the pinion only with half a campered gear lever. The chain tension continues to be a second assembly in the direction of the bottom bracket. Between 9-speed pinion set and differential, a 2-speed planetary gearbox is integrated in the housing, which can be operated by the steering handles. It has three positions:
High speed: 1:1 translation for normal driving speeds,
Neutral: The connection is delivered to the pedal and rope hand drive, which does not rotate backwards due to the two cable free-range rollers to push the trike backwards. In addition, the chain circuit can be switched freely in the stand with a few pedal revolutions to any new gear.
Low speed: 2.5 : 1 ratio for longer gradients or hard-to-drive terrain sections
20" front wheel in a teletype fork
rigid rear axle with triangular frame, 10 gearshift and 2-speed differential gearbox
Differential housings in detail (out of 9-speed pinion set with lever and planetary gearbox with differential in housing)
Two modified suspension springs from the Simson Moped S50 were used to suspend the rigid rear axle. The hydraulic shock absorber was adopted unchanged, the spring was peeled off and designed for lower preload. About 80 mm of travel is reached. The rear axle can be loaded with at least 100 kg.
On the rigid rear axle frame, one or more hub gears can also be easily assembled as an intermediate gearbox. An example of this is shown by the adjacent photo with an oil-lubricated 11-speed Shimano Alfine hub and a 3-speed SRAM hub as well as differential. There are chain shooters between the hubs. The overall ratio of such an arrangement is about 1: 9, and also allows driving in heavy terrain. However, it is estimated that only an overall efficiency of about 80% is achieved. This rear axle weighs around 15 kg together with wheels. However, it is meaningfully used, for example, in a quad with an auxiliary electric motor, where the weight is not so decisive.
Suspension of the rear axle with two spring units from the Simson S50 (black), whereby the spring and the preload were weakened.
Rear axle frame with 11 gear hub shift (Shimano), 3 gear hub shift (SRAM) and differential
c) Bicycle Quads
For a quad one need only some of the above solutions need to be combined. However, it is clear that the quad will become the heaviest vehicle of all, and can quickly reach a weight of around 50 kg. You will be compensated for the great weight with an enormous spring comfort when driving in difficult terrain.