Phase 1, Engineering Validation

A Proposal for
Backstack

Backstack is a premium weighted training backpack designed for strength training, rucking, hiking, and functional fitness.

Provisional

01 — Background

Background

BodyRax Ltd is a new United Kingdom fitness brand founded by Luke Farrow, preparing to launch its first product, Backstack. Backstack is a premium weighted training backpack designed for strength training, rucking, hiking, and functional fitness. Unlike a conventional weighted vest, the product carries standard Olympic weight plates on a rigid internal frame, with the load positioned high on the back to improve comfort, posture, and load distribution and to reduce strain on the lower back.

The product is built around a rigid structural spine that carries the weight, a plate mounting carrier that takes standard Olympic plates and allows quick add and remove, a central screw adjustment mechanism that sets the fit to the wearer, a padded waist support belt, and an adjustable shoulder and cross strap harness. The current prototype rates to 30kg of plates. Resistance band and accessory attachment points are part of the design.

Luke has a working prototype that he is happy with, shown in the images and videos provided. CAD was produced by another company approximately one year ago. Luke has decided not to re-engage that company and prefers to hand over the physical prototype and measurements so that our engineering team rebuilds the CAD to a manufacturing-ready standard. He is also considering design changes, principally simplifying or replacing the current fold-down adjustment rod, potentially with a fixed rod or an off-the-shelf threaded part, to reduce cost. Any agreed changes are folded into the CAD rebuild.

C2W and Shield Works have been engaged to rebuild the engineering basis of the product, assess it independently for manufacture, identify the right suppliers, and map the pathway from the current prototype through to qualified mass production. This proposal covers Phase 1 of that program, titled Engineering Validation, following the discovery calls held with Luke this month.

This proposal is marked provisional. The scope and fee set out below are firm. A dedicated Engineering Review Call between Shield Works R&D and Luke is proposed as a no-cost gate before project confirmation, to align the Phase 1 emphasis against the real engineering priorities, principally the structural spine and adjustment mechanism and the rod simplification. See Section 10 for the suggested sequence.

02 — Preliminary Read

Our Preliminary Read on the Product

Ahead of Phase 1 engagement, our team has reviewed the brief, the discovery call notes, the intake form, and the images and videos of the prototype. No CAD has been provided and none will be reused, so our engineering work starts from the physical prototype. The following is not the full Phase 1 output, but it is the position from which our work will start.

2.1 Where quality, cost, and timeline are actually won or lost

In our view, the following engineering areas drive most of how a weighted training backpack of this type performs, costs, and scales. These are the areas our Phase 1 work will prioritise.

Structural spine and load path

This is the central technical question on the product and is set up as a standalone engineering workstream. The spine carries up to 30kg of plates high on the back, which puts significant and repeated load through the frame, the plate carrier, and the mounting interfaces. Material selection (metal alloy, reinforced polymer, or a hybrid), section design, fastener and joint strategy, fatigue life under repeated loading, and a sensible safety margin all determine whether the product is safe, durable, and economic to make. Getting this right is the difference between a premium product and a warranty problem.

Adjustment mechanism and the rod redesign

The product uses a central screw mechanism to set the fit, and the current fold-down rod is the part Luke wants to simplify. Whether the adjustment becomes a fixed rod, a screw-in rod, or an off-the-shelf threaded component is both a cost decision and a usability and durability decision. Phase 1 will assess the options, including standard off-the-shelf parts where suitable, and recommend a direction that holds up under load and repeated use while reducing cost and assembly time.

Plate mounting and retention

The plate carrier must accept standard Olympic plates, hold them securely under dynamic movement, and allow quick and safe add and remove. The retention method, the tolerances against the range of Olympic plate dimensions on the market, and the wear behaviour over time are the questions that decide whether the product feels premium and secure or loose and cheap.

Soft goods and the metal-to-textile integration

The waist belt, shoulder harness, padding, and adjustability are a soft goods workstream that must integrate cleanly with the rigid frame. Material specification, stitching and load-bearing webbing, comfort under heavy load, and the mounting interface between the textile and the structural parts all feed the cost and the perceived quality. This is delivered through our qualified soft goods supply chain.

Cosmetic finish and brand feel

Premium positioning depends on the surface finish and the fit and finish of the assembled product. The finishing path for the structural and moulded parts, and the consistency of that finish across batches, is identified in Phase 1 and delivered through our qualified supply chain as part of the all-in unit cost.

2.2 Design maturity note

The product is functionally mature. A working prototype exists, the architecture is proven, and Luke is happy with the current form. This is a strong starting point and it speeds up the CAD rebuild, because we are reconstructing a design that already works rather than developing from a blank sheet. The work in Phase 1 is to convert that prototype into a clean, manufacturing-ready engineering basis, resolve the rod simplification, and confirm the cost and supply pathway. Our working assumption is a single product with no variant family at launch.

03 — Volume and Timeline Targets

Volume and Timeline Targets

The following reflects current working assumptions drawn from the brief, intake form, and discovery call notes. The figures will be reconciled and validated through Phase 1.

Field	Value
First Production Run	Approximately 150 to 200 units (client indicated)
Quantity Breaks to be Costed	100, 200, 300, 500, and 1,000 units
Annual Forecast	Approximately 2,000 units (to be confirmed)
Target Unit Cost	To be validated through the Phase 1 Indicative Quotation (see Section 5 note)
Target Retail Price	GBP 199 to 249 (client indicated)
Target Timeline to First Production	Approximately 8 to 12 weeks from Phase 1 completion (indicative)
Target Markets	United Kingdom primary; premium fitness positioning
Timeline	Flexible, when ready

04 — Phase 1, Engineering Validation

Phase 1, Engineering Validation

Phase 1, Engineering Validation is the first paid engagement in the Backstack development program. The work is engineering-led: a reconstruction of the CAD to a manufacturing-ready standard from the prototype and measurements, a focused engineering workstream on the structural spine and adjustment mechanism, a DFM, DFA, and DFX engineering assessment across the rigid and soft goods sub-assemblies, supplier engineering engagement with indicative pricing at quantity breaks, and a Development Roadmap that consolidates the output into a costed phase-by-phase pathway to qualified mass production manufacture.

Duration: approximately 8 working weeks, measured from arrival of the prototype at Shield Works, Zhuhai. Completion is possible sooner, around 6 weeks, where the prototype arrives promptly and kickoff aligns quickly.

Phase 1 consists of the following seven deliverables.

Engineering Kickoff Workshop

A working technical session with the Shield Works R&D team, not an introductory call. We walk through the Backstack product architecture, the prototype, Luke's commercial goals, and the proposed design changes, and agree the engineering priorities and workstreams before work begins. Luke has direct access to our engineers from this point.

CAD Reconstruction and Design Feasibility Assessment

Reconstruction of the product CAD to a manufacturing-ready standard from the physical prototype. This deliverable replaces the standard CAD and BOM audit, because no usable CAD exists. Output: a clean 3D CAD model, a full set of 2D manufacturing drawings with dimensions, tolerances, materials and finishes, and a structured bill of material, together forming a manufacturing-ready technical pack. This is the level of engineering detail that suppliers need to return meaningful, comparable prices rather than rough estimates. Also included is a written feasibility assessment and a ranked list of recommended design revisions for manufacture and cost. The rod simplification options are assessed and a recommended direction is given here.

Structural Spine and Adjustment Mechanism Workstream

Dedicated engineering workstream on the central technical question. Includes load path analysis through the spine, plate carrier, and mounting interfaces at the rated 30kg load, material and section selection trade-offs, fastener and joint strategy, a working safety margin, and the adjustment mechanism redesign including evaluation of fixed, screw-in, and off-the-shelf threaded options. Output: a documented engineering position with trade-off analysis and recommended direction for Phase 2 confirmation.

Preliminary DFM, DFA, and DFX Engineering Assessment

Written assessment covering DFM and DFA across the rigid frame, plate mounting, adjustment mechanism, and soft goods sub-assemblies, tooling strategy and indicative tooling direction, finishing path selection, packaging scope direction, assembly sequence, and a structured risk register with mitigations. Preliminary at this stage against analysis and supplier data; full DFM execution, engineering drawing release, and supplier qualification testing sit in Phase 2.

Supplier Engineering Shortlist and Indicative Quotation

Qualified supplier shortlist drawn from our Shield Works supply chain and wider network, with first-round engineering engagement to confirm capability and capacity across metal fabrication and machining, any moulded components, and soft goods manufacture. Indicative unit pricing at the quantity breaks set out in Section 3 (100, 200, 300, 500, 1,000), benchmarked against the shortlisted suppliers. Accuracy is subject to the defined level of readiness for manufacture; final unit costs are locked against specific supplier quotes as the Phase 2 development phases progress.

Industrial Design Review and Design Alignment

A standalone review of the current prototype industrial design against the positioning and target unit cost Luke is aiming for, with reference to comparable products in the category. Output: written recommendations for design language improvements to be carried into the CAD reconstruction, developed to work within Luke's cost target. Where optional premium enhancements would lift the product but add cost, these are presented as clearly costed options for Luke to review and decide, not as changes we impose. The core principle is to serve the target, not push past it.

Development Roadmap (Full RTMP)

The 25 to 35 page consolidating document that carries the Phase 1 engineering output forward into Phase 2 and through to qualified mass production manufacture. This is the full Route to Market Plan for Backstack.

The Development Roadmap will include:

Phase timelines and phase management costs across the full development program.
Shield Works resource allocations and core deliverables across sampling, development, design optimisation (full DFM, DFA, DFX), prototyping, pilot run manufacture, mass production, and scaled production.
Consolidated written output of the Phase 1 engineering work, including the CAD reconstruction, the structural workstream output, and the DFX assessment.
Component-level bill of materials with material specifications and qualified supplier direction.
Mechanical engineering and DFM plan for the rigid frame, plate mounting, adjustment mechanism, and soft goods.
Tooling strategy and indicative tooling investment direction.
Cosmetic finishing plan with indicative cost direction.
Prototyping and iteration plan with validation gates.
Pilot run manufacture plan with QC gating criteria.
Mass production pathway and scaled production goals.
Packaging direction and indicative packaging cost.
Risk register with mitigations and owner assignments.

Note: Phase 1 is the first phase of the Backstack development program. Phase 2 and subsequent development, tooling, and production work is scoped and costed within the Development Roadmap for Luke's approval before any execution begins.

Investment

USD 7,500

payable in full on project confirmation

05 — Indicative Development Envelope Preview

Indicative Development Envelope Preview

The figures below are preliminary ranges produced from our initial review and our experience with multi-component fitness and metal-and-textile products manufactured in China. They are shared ahead of the Phase 1 Indicative Quotation so that the shape of the investment is clear from the outset. They will be firmed up, detailed, and locked against specific supplier quotes in the Phase 1 output.

5.1 Development pathway, Phase 1 to first production

Stage	Scope	Timeline	Indicative fee
Engineering and DFM	Full DFM execution, engineering drawing release and revision from the Phase 1 tech pack, supplier qualification, finishing strategy	4 to 6 weeks	USD 6,000 to 11,000
Prototype build	First pre-production prototype in target materials and processes	4 to 6 weeks	USD 5,000 to 10,000
Prototype iteration (likely)	Second iteration on the adjustment mechanism, fit, finish, and any DFM-driven changes	3 to 4 weeks	USD 3,000 to 6,000
Tooling	Tooling for moulded components where used; fabrication tooling and fixtures for metal parts	6 to 10 weeks	USD 7,500 to 25,000
Pilot run	Trial production run for assembly validation and QC	3 to 4 weeks	USD 3,000 to 6,000
Industrial design execution and refinement	Delivery of the approved Phase 1 ID recommendations into the CAD and finalisation of the design language	2 to 3 weeks	USD 2,000 to 4,000
Development total (before mass production)	Indicative envelope, single prototype iteration	approx. 4 to 5 months	USD 27,000 to 62,000

Ranges assume a single product with no variant family at launch, a single prototype iteration, and finishing delivered through our qualified supply chain as part of the all-in unit cost. The envelope above excludes sample shipping and any third-party testing or certification fees, which are addressed separately in Section 6.

5.2 A note on target unit cost

Luke has indicated a target unit cost of around USD 60 and a target retail of GBP 199 to 249. We want to be straight with Luke on this from the outset, because it shapes the commercial plan.

Backstack combines a load-bearing metal frame rated to 30kg, a precision adjustment mechanism, a plate mounting system, and a padded soft goods harness, all assembled and finished to a premium standard. On a product of this type, a unit cost of around USD 60 is unlikely to be achievable at a first run of 150 to 200 units. Lower volumes carry higher per-unit setup and tooling recovery. Unit cost falls as volume rises, and the quantity breaks in the Phase 1 quotation (100 to 1,000) will show how far and how fast.

We are not setting a unit cost in this proposal. Material, process, and supplier decisions materially affect it, and it will not be locked until the Phase 1 work is complete. The Phase 1 Supplier Engineering Shortlist and Indicative Quotation is specifically designed to establish unit cost with confidence at each quantity break before any production commitment is made, so that Luke can build the retail and margin plan on real numbers.

5.3 Preliminary risk register

The risks below will be carried into the Development Roadmap with quantified mitigations. Surfacing them now signals where our engineering focus will be during Phase 1.

Risk	Likelihood	Impact	Primary mitigation
Structural frame fails to carry 30kg safely under repeated dynamic load	Medium	High	Load path analysis and material selection in the structural workstream; validated at prototype stage in Phase 2
Adjustment mechanism redesign reduces cost but compromises durability or usability	Medium	Medium	Options assessed in Phase 1 against load, usability, and cost; off-the-shelf parts evaluated; direction confirmed before tooling
Plate retention loose against the range of Olympic plate dimensions on the market	Medium	Medium	Tolerance study against standard plate dimensions in Phase 1; retention method confirmed at prototype
Target unit cost not achievable at low first-run volume	High	Medium	Indicative quotation at quantity breaks in Phase 1; honest cost-down options and volume planning in the Development Roadmap
Metal-to-textile integration affects comfort, fit, or perceived quality	Low-medium	Medium	Soft goods specification and integration interface engineered in Phase 1; confirmed at prototype

06 — Exclusions

Exclusions

The Phase 1 fee covers all six deliverables in Section 4, including the engineering work, the CAD reconstruction, the structural workstream, the DFX assessment, supplier engagement, the indicative quotation, and the Development Roadmap. The following are excluded and would be scoped and costed within the Development Roadmap itself.

Full DFM execution, engineering drawing release, and supplier qualification testing.

Prototyping, sampling, and physical testing.

Tooling and mould costs.

Shipping of the prototype or any samples between the United Kingdom and China.

Production unit costs.

Patent or utility model filing fees (guidance is included; filing costs are separate).

Any third-party product testing or certification fees, routed through external partners and quoted separately if required.

Note on the post-Phase 1 model: once a supplier set is confirmed and production begins, C2W and Shield Works operate as BodyRax's manufacturing partner. Luke receives a single unit cost for each Backstack unit that covers goods, assembly, quality control, supplier management, packaging, and logistics coordination. These are not billed as separate service fees. The Phase 1 Supplier Engineering Shortlist and Indicative Quotation is specifically designed to establish those unit costs with confidence before any production commitment is made.

07 — Payment Terms

Payment Terms

USD 7,500, payable in full on project confirmation.

08 — Safeguards and Clarifications

Safeguards and Clarifications

Provisional status and engineering review

This proposal is provisional pending a dedicated Engineering Review Call between Shield Works R&D and Luke. The scope and fee are firm. The purpose of the call is to align Phase 1 emphasis against the real engineering priorities, principally the structural spine and adjustment mechanism and the rod simplification, so that the Phase 1 output is built on the right starting assumptions.

CAD reconstruction

No usable CAD is being provided, so our team rebuilds the CAD to a manufacturing-ready standard from the physical prototype. The prototype is sent to the Shield Works R&D team in Zhuhai for this work. Having a working prototype already speeds this up, because we are reconstructing a proven design rather than developing from scratch.

Scope changes

If requirements change materially during Phase 1 (for example a change to the adjustment mechanism approach, a material change in target volumes, or the addition of testing or certification requirements), we will adjust cost and timeline accordingly and agree any changes before proceeding.

Quotation accuracy

The Indicative Quotation delivered as part of Phase 1 is subject to the level of readiness for manufacture. The cost envelope in Section 5 is directional. Final pricing is locked against specific supplier quotes inside the Phase 1 output and progressively refined through Phase 2 development.

Structural work and product testing

The Phase 1 structural output is a directional, reference-based engineering position. It draws on the readable geometry of the prototype and on comparable load-carrying products, and it gives a confident direction on load path and materials. It is not a design engineered and signed off to a formal safety standard. Physical load testing to confirm the frame at the rated load is a required part of Phase 2, not an optional formality. Phase 1 does not include accredited physical load testing or product safety certification. Where Luke requires load testing or certification for the United Kingdom market, Shield Works will identify and coordinate specialist testing partners as part of the Development Roadmap, with testing fees quoted separately and paid by Luke to the testing partner directly.

Intellectual property

BodyRax retains all intellectual property in the Backstack product, including the design, the reconstructed CAD, the BOM, and any derivative work produced under our engagement. Shield Works operates within an IP-secure, ISO-certified facility. An NNN agreement covering all third-party suppliers engaged on the project will be put in place before any external engagement begins.

Timelines

The 8 working week Phase 1 estimate is measured from arrival of the prototype at Shield Works, Zhuhai. Shipping and any customs clearance time sit outside this window. The Engineering Kickoff Workshop can be held while the prototype is in transit, so that hands-on engineering begins as soon as it arrives. The estimate assumes reasonable availability for the kickoff and follow-up technical discussions.

09 — Why C2W and Shield Works

Why C2W and Shield Works

Full-time dedicated project manager in our China HQ coordinating all suppliers, engineering resources, and the BodyRax team, with full visibility on who is making what and where.

In-house R&D, mechanical engineering, DFM and DFX, quality control, and audit resources, led by Mark Jacobs, a mechanical engineer with over 27 years of manufacturing experience and CEO of Shield Works and the C2W Group, alongside Sourya Ghosh, Head of R&D, who leads the engineering content of every Phase 1 engagement.

Direct experience in fitness equipment, including our own in-house fitness brand, and in metal-and-textile multi-component hardware assemblies.

Over 20 years of proven track record delivering complex multi-component consumer products from China, across metal fabrication and machining, moulding, soft goods, and premium cosmetic finishing.

IP-secure, ISO-certified manufacturing facility (Shield Works, Zhuhai) available for sub-assembly integration, quality control, packaging, and warehousing.

Established supply chain with Luke dealing with a single commercial counterparty for the all-in supply. No hidden middlemen, no opaque quotes, no surprises on quality.

End-to-end capability from concept through to qualified mass production, with packaging and 3PL services available through the same group of companies.

10 — Next Steps

Next Steps

Luke confirms the proposed Engineering Review Call between Shield Works R&D and BodyRax (no cost, approximately 45 to 60 minutes), with Mark Jacobs (CEO) and Sourya Ghosh (Head of R&D). Focus: the structural spine and adjustment mechanism, the rod simplification options, plate retention, and the soft goods integration.

On alignment from that call, Luke confirms acceptance of this proposal and the Phase 1 fee.

C2W issues invoice for USD 7,500.

On receipt of payment, we hold the Engineering Kickoff Workshop with the Shield Works R&D team. This can take place while the prototype is in transit, so no time is lost during shipping.

Luke sends the Backstack prototype to the Shield Works R&D team in Zhuhai so the hands-on engineering can begin.

The 8 week Phase 1 engineering window begins on arrival of the prototype in Zhuhai. Phase 1 output, including the full Development Roadmap with costs and timelines at quantity breaks, is delivered within approximately 8 working weeks of arrival, and potentially sooner where everything runs smoothly.

This proposal is non-binding at this stage and is intended to give Luke clarity on cost, structure, and what Phase 1 will actually produce. If you are happy with the direction, we can move to the Engineering Review Call at your convenience and proceed from there.

Best regards,

Mark Jacobs

CEO, C2W Group / Shield Works

June 2026