CadGaragePro 3D scans of trucks and 4x4s · 1:1 · mm

Bumper and bracket calculator

A plate weighs its length times width times thickness times the density of the metal: a 1800 by 250 mm face plate in 5 mm mild steel is about 17.7 kg. Enter the plates of your bumper or bracket below to get its weight, what it leaves of your front axle rating, and the flat length to cut for each bend.

1. What will it weigh?

The rows hold an example front bumper. Change the sizes, add or remove parts; all sizes in millimetres.

Material
Plates
PartLengthWidthThicknessQtyWeightRemove
 
 
 
 

Your answer

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2. How long is the flat plate before bending?

For a plate with one bend, measured on the outside of each leg (to where the outside faces meet). All sizes in millimetres.

Your answer

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How the numbers are worked out

Weight. Each plate is counted as a full rectangle: length × width × thickness gives its volume, and the density of the metal gives its mass (mild steel 7850 kg per cubic metre, 304 stainless 8000, 5052 aluminium 2680). Holes, cut-outs and the corners you trim make the real part lighter, so treat the total as an upper figure for the plate work. Tube, a winch and lights go in "other weight".

Axle margin. The margin is the front axle rating minus what the axle carries once the bar is on: today's front axle weight, less the factory bumper you take off, plus the new bar and what you mount on it. The bar sits ahead of the front axle, so in practice it also lifts a little weight off the rear; the front figure is the one that runs out first. Springs, airbag sensors and the rules where you drive matter as much as the weight: check them for your vehicle before you cut.

Bend allowance. When a plate bends, the inside squeezes and the outside stretches; the line that keeps its length sits at K × T from the inside face. The bend allowance is the length of that line through the bend: BA = angle in radians × (R + K × T). The outside setback is tan(angle ÷ 2) × (R + T), the bend deduction is twice the setback minus the allowance, and the flat length is leg A + leg B minus the deduction. Different machines, tools and batches of steel give different K-factors, so cut a test piece before a run.

To design the plates around the real vehicle, start from a measured scan of its front or rear: the file format picker lists the scans and plans that suit a bumper project, and building a bumper from a 3D scan walks through the design. Stuck on a part? Ask us; we take one or two small CAD jobs a week free.