Solution for heavy slow vehicles

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 The Relative-Motion Engine (RME) increases in-cylinder MEP and cycle work at lower RPM, allowing the engine to deliver the same or higher torque with lower mean piston speed. 

This shifts the traditional design constraints around the connecting-rod ratio (L/r): heavy-duty engines normally require long rods to support low-speed torque and durability, but with RME’s higher pressure-based torque, designers can safely shorten the rod without losing performance or increasing wear. The result is improved packaging, lower engine height, reduced friction and inertial load, and greater freedom to optimize NVH and manufacturability—while staying fully within conventional engine physics and validation metrics. 

• RME increases MEP and cycle work at lower RPM, raising torque output without higher piston speed.
• Higher MEP at low RPM reduces dependency on long dwell near TDC (a major reason heavy engines use high L/r).
• Lower RPM → lower inertial loads and side forces, making shorter rods mechanically acceptable.
• Torque delivery becomes less sensitive to L/r changes because pressure-based torque increases.
   

• Packaging: shorter block height, easier chassis/hood integration.
• Mass reduction: shorter rods → lighter rotating assembly and reduced block structure.
• Reduced friction: optimized geometry lowers skirt and ring loading.
• Lower cost: simpler rod forgings and block architecture.
• Improved NVH: modern piston design and lower RPM reduce noise/vibration despite shorter rod geometry.
• Durability preserved: lower mean piston speed offsets typical L/r penalties.
   

Heavy-Duty Engines (Trucks, Off-Highway):

• Maintain or increase low-RPM torque while reducing engine height.
• Opportunity to simplify block/crankcase and shorten rods without durability compromise.
• Enables taller gearing because torque curve shifts downward in RPM.
• Potential to reduce cylinder count while maintaining gradeability.

Mechanical studdies showed how the Relative-Motion Engine (RME), when applied to a heavy-duty 12–13L class engine, enables shortening the connecting-rod ratio (L/r) without compromising torque, durability, or side-loading limits. The conclusions below come from a comparative analysis of conventional vs. RME operating conditions using standard slider-crank mechanics.

The key point is simple:

RME maintains or increases torque at significantly lower RPM.
This reduces inertial acceleration to the point that a shorter rod becomes mechanically acceptable and often advantageous.
 

A representative 13L engine geometry is assumed:

• Bore: 130 mm
• Stroke: 160 mm → Crank radius r = 80 mm
• Conventional rod length: 300 mm → L/r ≈ 3.75
• Candidate short rod: 260 mm → L/r ≈ 3.25
   

Conventional engines reach peak power around 3,500–4,000 rpm.
RME targets similar wheel power at ~1,800–2,000 rpm because each cycle delivers more work.

Peak piston acceleration scales with:

apθ = -rω^2(cos⁡θ+r cos⁡2θ /L) 

Using representative values:

• Conventional engine @ 4,000 rpm: ≈ 17,800 m/s²
• RME engine @ 2,000 rpm with shorter rod: ≈ 4,600 m/s²
   

Result:
RME peak piston acceleration is ~26% of the conventional engine, even with a shorter rod.

This directly reduces:

• bearing loads 
• pin/boss stress
• skirt loading
• fatigue accumulation
   

Rod-angle geometry increases side load when L/r decreases.
At 10° ATDC:

• L/r = 3.75 → rod angle ≈ 2.65° → tanφ = 0.046
• L/r = 3.25 → rod angle ≈ 3.06° → tanφ = 0.0535
   

Geometry alone → ~15% higher side-load factor.

However, inertial force is proportional to piston acceleration.
Since RME reduces acceleration to ~26% of baseline:

Fside,inertial≈0.26×1.15=0.30F_{\text{side,inertial}} \approx 0.26 \times 1.15 = 0.30Fside,inertial​≈0.26×1.15=0.30 

Net effect:
Inertial side load in RME is ~70% lower than in the conventional 4,000 rpm case, even with the shorter rod.

Because RME operates at lower RPM with higher mean effective pressure (MEP), the engine produces higher torque at lower speed.
This offsets the torque sensitivity typically associated with reducing L/r.

Meanwhile:

• lower piston speed reduces friction,
• reduced acceleration lowers inertial stress,
• side-loading remains within limits for liners, skirts, and bearings.
   

Therefore, shortening the rod becomes a valid optimization option for:

• packaging (lower block height)
• weight reduction
• simplified rods and crankcase design
• improved vehicle integration
   

For a 13L heavy-duty engine, reducing L/r from ~3.75 to ~3.25 is mechanically feasible and potentially desirable under RME operating conditions. RME’s low-RPM, high-MEP behavior compensates for the geometric increase in rod angle, resulting in:

• ~26% of conventional acceleration,
• ~30% of inertial side-load,
• no loss in torque, and
• improved packaging and efficiency opportunities.
   

We recommend beginning feasibility studies for shortened-rod architectures in heavy-duty applications where RME is under consideration.