As of right now, we have only briefly discussed how friction will be taken care of. I mentioned using Teflon pads inside the slider to minimize friction between the two sliding tubes, with integrated grease fittings/nipples. I think this is a good idea, but I am skeptical as how it would hold up over time. Also, the channels for the shock pins will need sort of bearing in order to minimize friction and reduce wear.
Tyler made this CAD of the slider with coilovers based on what are group had sketched up by hand. After looking at it, I think it has potential but needs some critical improvements. The pins that support the shocks, and subsequently the entire cabin are in single shear, and would likely have a high fatigue rate if mounted in this way. At the very least, we need to come up with a way to put these connections in double shear, for safety and longevity. Also, for the channels, it would be good to have a means of closing off the sections around the pins with some sort of move-able seal, so that debris does not enter the slider causing increased wear on the slider.
Now that our team has decided on a suspension configuration, we can now begin to look into what components will be needed to make this system work. I began to focus this week on the active part of the suspension, namely the actuators. For our 1/4 scale model I made a conservative estimate of 500lbs for the weight of the cabin and its occupants (2,000lbs full scale).
The way we have isolated the suspension from the cabin control system means the actuators must support the full weight of everything beneath the bogie. The plan is is use 3 actuators in total, 2 of which will be used to control the angle, and all 3 will contribute to the leveling of the cabin as it approaches the loading platform. With this design, the actuators are a critical safety component, as they will be under constant load, with frequent impulses. This is concerning because the entire safety of the system is predicated on the quality of the actuators. That said, with the right actuators the shouldn't be a problem.
However, with a limited budget, it may be difficult to find the perfect actuators for our needs. In theory, each actuator only needs to support about 1/3 of the load, but when a factor of safety is included, this number will likely increase significantly. After some research, I have found actuators that can support loads close to what we need, the problem is the size. For example, I found actuators that can support 400lbs, but are far too large for our application.
I think with more research I should be able to find something that fits our needs, though it will be a challenge to balance loading, size, weight, and cost.
Here is a link to some promising options: https://www.firgelliauto.com/products/heavy-duty
