Trike simplified steering linkage

Continuing the tadpole trike front suspension project, here are recent posts:

• Trike 320 rear fork large gap fixed — June 21, 2024
• Trike hinge for steering arms — June 20, 2024
• Motrike 320 rear shock mounted with ordinary bolts — June 16, 2024
• Trike Mark-3 swing-arms constructed — June 14, 2024
• Trike 320 frame rear fork large gap — June 13, 2024
• Recumbent trike front suspension Mark-3 — June 01, 2024
• Ackermann steering compensation — May 31, 2024

...that last link describes a fairly sophisticated steering linkage mechanism, that provides Ackermann compensation and handles the shock-absorber suspension.

However, that linkage is complicated, and for now I just want to get the trike to a rideable state as soon as possible. So, have figured out a linkage design that is very simple and makes use of what is already available.

There are four tie-rods from the trike; the two shorter ones I will use. Also will attach them to the existing mount points on the arms-frame. This diagram shows how it goes together:

As using the existing tie-rods and arm mount-points, it requires the knuckle-levers to be extended, as shown in red. The red lines are parallel to wheel direction and there is a 15mm offset where the tie-rods are attached.

There are all kinds of compromises.

There is Ackermann compensation, but not perfect. The lower-left curve is a 2m radius, the outer curve is a 2.4m radius. Circles are concentric. If the steering is turned so that the outer wheel is following the 2.4m radius, the inner wheel has turned a bit too much; 1.55° too much.

Turning a larger circle, 3.2m inner radius and 3.6m outer radius, the inner wheel turns 0.9° too much.

Another compromise is that the steering arms swivelling is limited by the seat. This is going to limit turning to about a 2m radius. I guess can live with that.

If a wheel hits a bump, the tie-rod will cause the wheel to turn in or out slightly. I think that the tie-rod can be connected such that the wheel will turn slightly inward with a small bump, and slightly outward with a bigger bump. That situation would be improved with longer tie-rods; however, the other two that I have are too long, and I couldn't figure out how to fit them in, at least not without a huge amount of extra construction.

The only thing required to construct is the knuckle-lever extensions, that I will probably do on Monday.

Pretty much definitely will be wanting to modify this steering design later, but this will get me out onto the road quickly. I'm looking forward to experiencing how much the compromises affect the actual riding handling.

The SolveSpace design is here, with false ".gz".  

Tags: light