rear-mounted differentials

[URracing]

Just curious about setups I've seen where the diff is mounted off the rear bulkhead of the frame, directly behind the motor. Reason obviously is to reduce overhanging components in the frame and suspension in reducing weight and complexity. I know a couple of teams get away with attaching their rear a-arms to the sub-structure that the diff is housed in but on the other hand, I've also seen teams angle their rear a-arm link on a FORWARD angle since there is little or no frame rail present rear of that bulkhead. To me this is multiplying your forces through that a-arm linkage exponentially - sort of like an over-center locking mechanism of such design. Just curious how those teams made out in design and whether or not the components stood up to the physical testing on the track.

I cannot recall but I thought the rules state somewhere that the driveline is supposed to be in-line with regards to the vertical and horizontal planes crossing through the center of the differential (static loading). This means you cannot even bring the drive shafts out to the upright on a forward angle either - even though I've seen that too.

I could use some enlightening on this matter since I did not find any accurate info that is previously posted on this forum in regards to this matter, yet I would like to gain a further understanding of this concept.

[URracing]

Just curious about setups I've seen where the diff is mounted off the rear bulkhead of the frame, directly behind the motor. Reason obviously is to reduce overhanging components in the frame and suspension in reducing weight and complexity. I know a couple of teams get away with attaching their rear a-arms to the sub-structure that the diff is housed in but on the other hand, I've also seen teams angle their rear a-arm link on a FORWARD angle since there is little or no frame rail present rear of that bulkhead. To me this is multiplying your forces through that a-arm linkage exponentially - sort of like an over-center locking mechanism of such design. Just curious how those teams made out in design and whether or not the components stood up to the physical testing on the track.

I cannot recall but I thought the rules state somewhere that the driveline is supposed to be in-line with regards to the vertical and horizontal planes crossing through the center of the differential (static loading). This means you cannot even bring the drive shafts out to the upright on a forward angle either - even though I've seen that too.

I could use some enlightening on this matter since I did not find any accurate info that is previously posted on this forum in regards to this matter, yet I would like to gain a further understanding of this concept.

[drivetrainUW-Platt]

Cornell 2007 did all the above...pretty sure they know what they are doing from their track record or wins

[MacGyver27]

Some driveshaft angle is sacrificed with this design but it is worth the increased rear weight bias, and decreased overall complexity. The result of forward canted a-arm links is a mild increase in a-arm load. However, without a rear bay, the chassis is effectively shortened and effects on compliance are negligible compared to other factors.