FAQ #304
Driveshaft through USM

Last Updated On 2020-10-16 11:35:52 ET by

adrive7

Question
Can a longitudinal driveshaft run through the longitudinal USM in order to meet powertrain guarding rules?

If all other thickness and strength requirements were not compromised throughout the system's integration, would this be acceptable?
Answer
A tube could be used to meet the protection rules, however if your intention is to sleeve ALC, consider the following:

Sleeves should not exceed half the tube diameter they are installed in, and the wall thickness should generally match; understanding small corrections may be necessary to accommodate commercially available tube and faster dimensions.

For example:
1.25"OD x .065" fitted with a .625"OD x .065" sleeve would yield a fastener through-hole of .495"; boring this to .500" would be reasonable.
1.00"OD x .120" fitted with a .500"OD x .120" sleeve would yield a fastener through-hole of .260", reasonable for a .25" bolt.

Please also remember the ALC is required to be continuous, (B.3.2.6); and actually sustains a significant amount of damage during competition.
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Rule Numbers
2021:B.3.2.11 
2021:B.9.6