## 2 Materials and Methods
### Testing
#### 2.4.1 Early Qualitative Evaluation  
At this moment, the first group of qualitative field tests have been carried out to assess drivability, looking at the device from the carrier's point of view, although with some delay due to the pandemic situation. These tests were carried out by a group of expert designers and some members of BrAL (Brixia Accessibility Lab) and were performed in a park and on some simple mountain bike trails nearby (Figure 7). There were always two carriers, from a pool of three people who worked on the wheelchair development, alternating in their role (both in the rear and front positions). In these tests, the passenger was a non-disabled person.  
These kinds of tests have the purpose of giving technical information about the wheelchair behavior, as an actual vehicle test. They come in a pre-engineering phase as completion of the prototyping phase; therefore, a high number of carriers are not required, rather it is required that the carriers know the phenomenon on which they must make a judgment. For this, the three designers who worked on the development of the wheelchair were chosen as carriers and can be considered as actual test drivers [20; 21; 22; 23].  
1. In reference to the considerations on the use of the device as discussed in [11] (relating the wheelchair design choices to its scope of use), nine types of maneuvers and routes were chosen to characterize the drivability and the balance of the device single step (the step is approximately 150 mm high), Figure 7a;
2. long curve;
3. tight curve;
4. flat path on grass Figure 7b;
5. grass track with ups and downs, Figure 7d;
6. uphill mountain track (with deep potholes both dry and muddy);
7. downhill mountain track (with deep potholes both dry and muddy) Figure 7c;
8. uphill hairpin bend (with deep potholes both dry and muddy);
9. downhill hairpin bend (with deep potholes both dry and muddy).  
Figure 6: Prototyping and testing phases of the Gölem project.  
These nine types of tests were chosen between typical maneuvers that carriers may encounter during trekking activities on trails. Two routes were identified: maneuvers 1 through 4 were performed on the easy path represented by the lawn of the university parking lot, while maneuvers 5 through 9 were performed on a more MTB demanding trail.  
Figure 7: Cont.  
In general, in trekking wheelchairs, the role of the two carriers is different and well defined: the front carrier tows the wheelchair, the rear carrier maneuvers, contributing less to the pushing effort, being more focused on equilibrium. From a technical point of view, it should also be noted that, in our prototype the rear bar can be configurable in two versions: (1) configuration with steerable handlebars; (2) configuration with the handlebars rigidly connected to the frame, with a pivoting rear wheel (\"caster wheel\"). The steerable handlebar has been designed to obtain increased maneuverability in tight bends. In current commercial solutions, the rear bar is only rigidly connected to the frame. For this reason, in this first series of qualitative tests the prototype was tested only in the configuration with steerable handlebars. This was conducted to verify the effectiveness of the new proposal (steerable handlebar) for the functions of drivability and balance. The qualitative tests carried out involved alternating three carriers in the front and rear positions and assessing their feelings about drivability and balance. Drivability is meant as ease of maneuver (e.g., tight bend, wide bend) and balance is meant as the effort required to keep the device balanced.