The dance floor
Floor → joists → beams or trusses → supports → verified chassis attachments. Design for stiffness, vibration and moving loads.
Structure study / 01 · Requirements fixed, concepts open
A lighter frame.
Same dance floor.
Two ways to carry the party and the sheep. Compare the load paths, see where the weight lives, and explore what a four-station frame would have to save.
DESIGN STATUSExploring
Neither concept is selected or load-rated. Donor measurements are deferred.
01 / The shared brief
Keep the job the same.
20people · 225 lb each
5 mphmaximum event speed
206exterior panels
102″maximum road width
Dancing while moving. Keep the modeled 37.4 × 8.9 ft deck, its 11.16 ft surface height above ground, and removable event assemblies. The 4,500-lb people allowance is a design input; it is not an approved occupancy.
Open to change: support count, sections, floor construction, truss depth, bracing and connections. Road mode retains the bus and permanent supports with every fitting; the event deck/frame, panels, projecting arms and speakers come off.
What is deliberately unresolved?
Measurements · deferred
Actual body/rub-rail envelope; chassis dimensions and attachment access; scale weights and axle ratings; equipment weights and locations.
Engineering · still to establish
Loads from dancing, stops, turns, bumps and wind; floor vibration; transverse restraint; joints and chassis flexibility; vehicle stability. A speed limit does not define these loads.
No modification selected
No rub-rail cutting, body welding, assumed roof-body capacity or final tube sizes. The deck footprint and height remain the comparison constraints.
02 / Two concepts, one job
Follow the load.
Loading the comparison diagrams…
Floor / primary framePermanent supportsPanel envelopeLoad direction
Concept A
Optimized six-station frame
Keep the shorter spans. Rework floor construction and member efficiency before removing supports.
12uprights
10.6 ftlongest support span
Side view shows one row of supports; each station is a pair. Bus and station positions follow the current unmeasured model. Cross-sections and connections are schematic.
The sheep
206 panels → lighter removable subframes → selected primary-frame attachment points. Panel wind loads still need restraint.
The heavy things
Speakers, head and equipment → dedicated supports. Put their actual concentrated loads into the frame analysis.
| Question | A · Optimized six | B · Four + trusses |
|---|---|---|
| Starting support locations | A, B, C, D, E, F | A, C, D, F; first trial, not optimized |
| Weight-saving strategy | Lighter floor and members while retaining shorter spans | Remove two stations; use longitudinal trusses to carry longer spans |
| Known reference | 4,466 lb frame/floor subtotal before optimization | 524 lb gross station removal before replacement steel |
| Floor work | Same footprint and surface height. Compare joist depth, spacing and deck construction; no lighter floor is yet specified. | |
| Transverse stability | Must be designed. Side diagonals and roof-plane bracing alone do not establish transverse restraint. | |
| Main tradeoff | More attachments and posts; potentially lighter spanning members | Higher concentrated reactions, truss joints and larger modules; depth must fit without raising the deck |
| Final weight / structural result | Not yet sized or checked as a complete frame | Not yet sized or checked as a complete frame |
03 / Where the pounds are
Start with the floor.
4,466lb · current modeled subtotal
The joists and plywood account for almost 2,000 lb. Station count is one lever; the floor is another. These are masses from the current model, not minimum required sizes.
Excludes connections, fasteners, guardrails, panels and their subframes, head, speakers and equipment. Nominal tube dimensions and material densities are approximate. Source member schedule ↓
04 / A weight budget, not a strength calculator
When do fewer supports pay off?
Try the same floor-weight targets for both concepts, then account for the four-station frame’s extra steel. These controls express hypothetical mass changes. They do not resize members, check capacity or predict a finished build weight.
0–40% is an exploration range, not a demonstrated achievable saving. Existing joists: 1,220 lb.
A lighter floor construction must still satisfy local loads, spans, durability and stiffness.
Net change relative to retained members: trusses, replacement beams, reinforcement and differential fittings. Default is near break-even, not an estimate. Common unsized systems remain excluded.
Hypothetical comparable subtotals
A · Optimized six—
B · Four + trusses—
Loading budget…
Four-station break-even allowance524 lb
Above this net added weight, removing two stations no longer saves weight under otherwise equal assumptions.
05 / Road fit remains a hard requirement
102 inches. Every retained fitting.
The current v5 model is 103.35 inches wide including the mirrored docking-pad estimate. It fails the width requirement. The complete retained-hardware inventory and real donor dimensions are still unresolved. Neither new concept has a verified road envelope.
Reducing station count does not narrow the remaining uprights. Recessing or integrating them into the bus requires its own design; it is not assumed in these comparisons.
Current geometry audit ↗ Washington width rule ↗06 / What this enables next
Size the systems.
Then choose the lighter one.
The comparison brief is ready. A preferred design comes after the engineering and donor evidence, not from the budget sliders.
- Develop members and connectionsFloor options, available truss depth, transverse restraint and removable joint layouts.
- Establish loads and check the whole frameCrowd distribution, moving loads, wind, vibration, chassis attachment forces and vehicle stability.
- Reconcile with the donor when measurements are availableVerify fit, access, axle limits and all retained hardware; recalculate mass including fittings.
- Review before fabricationResolve the structural and vehicle-interface details, then produce member schedules and assembly drawings.
Basis & downloads
Shared design brief · Comparison data & assumptions · Reference geometry · Existing 3D study
The existing bus body is not credited with dance-floor capacity. Blue Bird’s family manual describes structural bows and rub rails, but does not establish the capacity of this donor or conversion. Body reference. Truss members and joints need to be considered together: Steel Tube Institute connection guidance.
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