Trailer engineering · Colorado-based
Trailer design and engineering support
Weight distribution and axle placement, bridge formula and state compliance checks, structural calculations, engineering drawings and design consulting for trailers and tractor-trailers, by Dustin Randle.
Engineering services for trailers
Get the axle loads, the compliance check, the calculations or the drawings you need, with the engineering behind them.
Trailer Weight Distribution & Axle Placement
Where the axles go, where the load sits, and what each axle group carries, calculated with statics and checked against legal limits.
Learn more →Bridge Formula & State Size/Weight Compliance Checks
Every axle group checked against the Federal Bridge Formula and the state rules on your route, with the margin on each.
Learn more →Trailer Structural Calculations & Design Review
Frame, crossmember and connection checks for new designs, repairs and modifications such as extensions or axle moves.
Learn more →Trailer Engineering Drawings
General arrangement, axle layout and detail drawings, with weight sheets that match the calculations.
Learn more →Trailer Design Consulting
Engineering support from concept to build for new models, custom and specialty trailers.
Learn more →Free Bridge Law Calculator
Check axle group loads and the federal bridge formula for a 5-axle tractor-trailer or a straight truck in your browser.
Open the Bridge Law Calculator → Quick check →How it works
- Send the details. Drawings, spec sheets, scale tickets, photos, and what the engineering is for.
- Get a scope and quote. You will know what will be checked, what you will receive and the price before work starts.
- Engineering. Loads, axle placement, bridge formula and structure are calculated and checked.
- Deliverable. A layout sheet, calculation package, drawing set or written findings, as agreed.
Forensic engineering
Trailer and truck failure analysis, overloading and load-shift investigations, rollover contributing factors, claim and warranty support, and expert reports for attorneys and insurers.
Why get engineering help on trailer weights
Scale tickets tell you what happened. An engineered layout tells you what will happen before the trailer is built, modified or loaded: which axle group runs out of capacity first, how far the axles or load can move, and whether every axle group passes the bridge formula.
- Statics-based axle load calculations for every axle and group
- Federal bridge formula checked on every consecutive axle group
- State rules checked for the states you name
- Clear documentation of assumptions, calculations and results
About the engineer
Dustin Randle is a Colorado-based trailer engineer working on trailer weights, layouts and structure. Have a question for him? Ask Dustin directly.
About Dustin →Common questions
What does a trailer engineer do?
A trailer engineer works out how loads travel through a trailer and onto the road: where the axles should go, what each axle group carries, whether the frame and connections are strong enough, and whether the finished rig meets axle-weight laws. The result is usually a layout, a calculation package, a letter or a drawing.
What is the federal bridge formula?
It is the federal rule that limits the weight on any group of two or more consecutive axles: W = 500 × (LN/(N−1) + 12N + 36), where L is the distance in feet between the outer axles of the group and N is the number of axles. Interstate limits are also 20,000 lb per single axle, 34,000 lb per tandem and 80,000 lb gross. States can add their own rules.
Is the Bridge Law Calculator an engineering review?
No. The Bridge Law Calculator gives estimates for planning. It is not an engineering review, the quick check does not check state rules, and it does not replace an engineered layout or a scale ticket.
What information do you need for a quote?
Trailer and truck drawings or spec sheets, axle spacings and ratings, empty weights (scale tickets are best), payload weight and position, the states you run in, and what the engineering is for. Photos help for modifications.
Need an engineered layout? Request a quote.
Send your trailer details, drawings or scale tickets. You will get a scope and a quote before any work starts.
Request a quote