Durable Wheel End Drive for Amphibious Vehicles

Navy SBIR 24.1 - Topic N241-001
MCSC - Marine Corps Systems Command
Pre-release 11/29/23   Opens to accept proposals 1/03/24   Now Closes 2/21/24 12:00pm ET    [ View Q&A ]

N241-001 TITLE: Durable Wheel End Drive for Amphibious Vehicles


OBJECTIVE: Design and develop a new or improved drive axle for the Amphibious Combat Vehicle with greater durability when subjected to operation in an amphibious environment.

DESCRIPTION: The United States Marine Corps is fielding the Amphibious Combat Vehicle (ACV) designed to operate over harsh off-road terrain and in oceans and rivers. The ACV currently uses traditional Constant Velocity (CV) Joints on the wheel end drives that require excessive maintenance because they develop holes and tears in the inside and outside CV Boots. The Marine Corps is interested in innovative approaches to develop a more durable wheel end drive. The design must protect the current CV Boots, replace the Boot with a more durable material, or redesign the wheel end drive joint so that it does not require a grease filled boot covered joint.

Proposed concepts should:

- Address the ability to function in extreme operating environments which include but are not limited to -40 degrees Fahrenheit (°F) to +120°F, hot desert blowing sand, full salt water immersion, operation to and from the beach in surf zones up to 6 foot Significant Breaker Height (SBH) and mud (soft soil of 30 Rating Cone Index (RCI)) which includes suspended abrasive items such as rocks, gravel, sand, and coral.

- Allow for terrain traverse with combined 3 g-force (G) vertical and 0.7 G horizontal load on suspension station, racking load at diagonal corners for 1 G vertical load, North Atlantic Treaty Organization (NATO) tree impact (5" tree at 32 kilometers per hour (kph)-8365 pound equivalent static load), and fatigue loads for 30 year vehicle life.

- Allow for a maximum of 4,350 newton-meters (NM) of torque, a maximum angle of 40 degrees (short duration), and a maximum rotation speed of 2,682 RPM.

- Support steering in the forward and reverse directions on 40% side slopes and ascending, descending, starting, and stopping on a dry hard surfaced longitudinal slope up to and including 60% grade in both forward and reverse direction.

PHASE I: Design a more durable wheel end drive in consideration of the operating environment in which the drive system will be exposed. Demonstrate, via modeling or testing, the feasibility of the concept(s) in meeting Marine Corps’ needs and establish that the concept can be developed into a useful product for the Marine Corps. Feasibility will be established by material testing and analytical modeling as appropriate. Provide a Phase II development plan with performance goals and key technical milestones that will address technical risk reduction.

PHASE II: Develop a scaled prototype for evaluation. The prototype will be evaluated to determine its capability in meeting the performance goals established for the Marine Corps’ amphibious vehicles. System performance will be demonstrated through prototype evaluation and modeling or analytical methods over the required range of parameters. Evaluation results will be used to refine the prototype into a design that will meet Marine Corps requirements. Working with the Marine Corps, prepare a Phase III development plan to detail the strategy for transitioning the technology for Marine Corps use.

PHASE III DUAL USE APPLICATIONS: Support the Marine Corps in transitioning the durable wheel end drive system for Marine Corps use. Working with the Marine Corps, integrate the prototype wheel end drive system into a vehicle for evaluation to determine its effectiveness in an operationally relevant environment. Provide support to the Marine Corps during test and validation to certify and qualify the system for Marine Corps use. Develop manufacturing plans and capabilities to produce the system for both military and commercial markets.

This technology is directly applicable to large military vehicles such as the Marine Corps ACV.

Successful development and characterization of a durable wheel end drive system has direct application to various military and commercial applications such as amphibious rescue vehicles. Reductions of weight and complexity in the suspension can be of substantial value.


  1. MIL-STD-810G Environmental Test Methods and Engineering Guidelines. http://www.everyspec.com/MIL-STD/MIL-STD-0800-0899/MIL-STD-810_13751/
  2. MIL-STD-889B Dissimilar Metals.http://www.everyspec.com/MIL-STD/MIL-STD-0800-0899/MIL_STD_889B_955/
  3. Description of a flex joint/Giubo. https://en.wikipedia.org/wiki/Giubo

KEYWORDS: Provide a minimum of six key words separated by semicolons. Drive; axle; constant velocity joint (CV Joint); boot, Giubo; amphibious


The Navy Topic above is an "unofficial" copy from the Navy Topics in the DoD 24.1 SBIR BAA. Please see the official DoD Topic website at www.defensesbirsttr.mil/SBIR-STTR/Opportunities/#announcements for any updates.

The DoD issued its Navy 24.1 SBIR Topics pre-release on November 28, 2023 which opens to receive proposals on January 3, 2024, and now closes February 21, (12:00pm ET).

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Topic Q & A

1/8/24  Q. The description of a traditional CV joint can be interpreted a few different ways. Does the ACV have a traditional ball joint CV, or is it a different style CV joint at both the hull side and wheel-end side of the drive axle shaft?
   A. The ACV has a traditional CV joint design, similar to many other commercial and military vehicles.
12/10/23  Q. Q-1) Is the CV boot generally damaged by: "An amphibian Environment" vs. obstacle contact(s)?
Q-2) Is it the front axle boots that are being damaged (only) or equally the next-to-front axle also?
Q-3) Do the vehicle maintenance personnel think that the boot problem related more to "range of angular alignment" or pinching/stretching issues?
Q 4-5) Would a solution that advocates a station mount change get adequate review or get rejected? Could a non-mount solution and a station mount design change bot be presented and justified in the same proposal and get review of both as a fix requirement?
   A. A-1: We have seen issues with damage from foreign object debris as well as seized bearings due to corrosion, so the answer is that the boot is damaged by both obstacle contact and being operated in an amphibious environment.
A-2: We have seen damage on boots on all axles, but the foreign object debris damage is primarily seen on the first 2 axles. The corrosion issues are present on all axles, not just the front 2.
A-3: This was an initial consideration, but after further investigation, it does not appear to be due to either of these factors.
A-4-5: From my perspective, we are open to all potential suggestions - I can't speak to whether a station mount change would be rejected or not. All submissions should have adequate reviews by our team. I do know there will be challenges in dealing with our Prime Contractor and their sub-contractors, and the challenges will only increase the more components are impacted.
12/06/23  Q. Q-1) Is the "durable wheel end drive system for Marine Corps use" being sought for a specific amphibious Vehicle, or for a notional future vehicle?
Q-2) What vehicle application?
Q-3) Do you prefer a CV Boot fix or a total suspension station improvement (along with propulsion/power compliance issues being addressed and resolved?
   A. A-1: A specific Amphibious Vehicle
A-2: The Amphibious Combat Vehicle (ACV)
A-3: CV Boot fix is preferred instead of a total suspension station improvement.

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