Worm gearbox for steering

Question

I'm planning on making a smallish off-road rover (15-25kg net weight) with 4-wheel steering and I was wondering if it'd be a good idea to use (self-locking) worm gearboxes for steering. I've thought about using planetary gearboxes, but self-locking gearboxes will help improve power consumption.

I've found this gearbox but it's not clear whether it's applicable to steering tasks. Here's the spec:

I have several questions and it'd be great if anyone could help:

1. As the 1:18 variant has a axial force of 250N, does that mean if the load is ~25kg, I'd need to have additional bearings and support for distributing the load?

2. The duty cycle is 20% at 5min. Is this generally adequate for steering? When steering in a straight line on off-road at low speed, the adjustment may be small but frequent.

3. A gearbox like that costs around $180. Are there more economical alternatives that are self-locking?

Any advice appreciated. TIA.

Answer 1

1. Axial (or thrust) force refers to the force applied along the axis of rotation, not the load that is applied to the motor. (This load would be a torque, anyways... not a force).
2. Probably fine for a tractor, not fine for a F1 racecar. This is a question you need to answer based on your application.
3. There might be. You can adapt drills with anti-backdrive pins to accomplish this (they are a planetary gearset). Example: https://www.chiefdelphi.com/uploads/short-url/k05tcmRrq5EsCc5xvPtZvbKd5DT.pdf

Other things to think about:

4. A typical vehicle suspension system has caster and kingpin angles such that the tires automatically re-center. This not only produces a desirable user experience (resistance in an even direction), but it prevents wheels from shaking at high speeds. You'll probably want to consider having this self-centering behavior which will produce higher load on your actuator.
5. Linkages matter. What sort of linkages are you connecting the steering to the gearbox via?