Driver Selection

The purpose of this page is to discuss the implications of driver dimensions and help in selecting the drivers for MS16.

Driver Dimensions

1. Hip-to-Head

This dimension is significant because an increase in waist to head height would mean an increase in canopy height, and as an increase in frontal area (and therefore drag force).

based off of these rough calculations,

A four-inch increase in waist-to-head height (going from 5’8” to 6', for example) will result in approximately a 5% increase in drag force, if we assume drag coefficient remains constant. This will be more noticeable if we decrease the car's overall width.

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Additionally, the roll cage height would have to be increased, adding extra mass.

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Extra rollcage weight

Based on these calculations, adding 10cm to the height of the rollcage would add at least 1.2kg of weight in tubing. This number will probably end up being larger, since the moment arm during a rollover is longer meaning the rollcage will have to be reinforced.

The overall center of gravity of the car must also be considered - raising the height of the driver raises the center of gravity. We must ensure that it still stays within the tip table bounding box.

There is also a minimum waist to height of around 42cm (driver eyes must be over 700mm from ground).

2. Hip-to-Shoulder

The higher the shoulders, the higher the body of the chassis (everything thats not the rollcage) has to be. This increases chassis weight and frontal area. This has more effect if we are minimising aerobody width and height.

3. Hip-to-feet

The longer the waist-to-foot distance, the longer (or taller) the occupant cell of the chassis will have to be. Not accounting extra supports this would entail, it would cost about 860g per 10cm of length.

3. Shoulder Width

The wider the shoulders, the wider the occupant cell, the more material, and the wider the car. Egress will also be more difficult and more thought will have to go into designing it.

4. Weight

Any weight over 80kg will be directly added weight to the car. For drivers under 80kg, bllast will be added to the car to bring the driver+ballast weight up to 80kg. Drivers must lift their own ballast, so they must also be able to comfortably lift their weight subtracted from 80kg.

Note as well that the more ballast a driver has, the lower the cg of the vehicle (assuming the ballast box is bellow the driver.

5. Adjustability

The higher the difference between the tallest and shortest driver on the roster, the more adjustable the vehicle will have to be. This might mean adujstable pedals, adjustable steering column etc. It also may not be possible to adjust the seatbelt for a height range of more than 2”.

6. # of available drivers.

Currently there are 3 eligible 6' drivers and 4 eligible 5’10” drivers. Eligible in this case means that they are under 80kg.

For future drivers, note that the average height in Canada is ~5’7” (for 20-39 year olds). Average male height is ~5’10”. I haven’t been paying attention to stats but I’m fairly confident that it will be more likely that we get more drivers in the 5’8”-5’10” range than the 5’10” - 6” range. (Canadian Health Measures Survey: Cycle 2 Data Tables: Table 22 — Measured standing height, by age and sex, household population, Canada, 2009 to 2011 (statcan.gc.ca)

Finally, consider that taller people generally weigh more and have broader shoulders, meaning they have a higher chance of being eliminated as a driver anyway.

Implications

A taller driver will most likely mean a heavier car with higher drag, although not by a huge amount. Wider shoulders (or body in general) will also mean a heavier car with higher drag, although probably not by a huge amount. The weight of the driver basically has to be under 80kg.

Conclusion

The car is almost guaranteed to be less optimal if it is built for taller, wider people. That being said, we are a relatively tall team and a chassis made to accommodate 6” drivers will accommodate for almost everyone on the team. If members are more motivated to work on the car if they can drive it, accommodating them could benefit the team in the long run. It should be noted that there is tolerance built into occupancy cell, so basically everyone would be able to test drive the car if it was designed for a 5’9 driver, they just wouldn’t pass regs. It is highly recommended that every driver is within 1-2inches, regardless of chosen height. This means that if we design the chassis around a 6” person, the minimum height that could drive would be 5’10”.

Regardless of which height we decide on, one group of people will not be able to drive.

Decision Matrix

Data entries are either -1, 0, or 1, relative to the status quo

Note that weights were not added because relative impact is hard to calculate and it is already exceedingly clear which option is better from a technical standpoint.

Although this is meant to be a purely technical discussion, we understand that there are emotions tied to it, but it should be noted that 100% of leads who participated in our survey voted to cap the height regardless of their eligibility.