Instructions For Assembling A Pedicruiser Cart To A Huffy Fixed-Frame Bicycle

Downloadable Instructions here

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The following is a general step-by-step guide that can be adjusted to suit the bicycle and attachment you want to put together. My idea was to craft this as a rigid HPV (Human Powered Vehicle) that can be used in the place of motorized transportation. In this era of challenging fuel prices, the race is on to create efficient vehicles that minimize the carbon footprint and get you from place to place as inexpensively as possible.

Whether you're a seasoned wrench-turner or just diving into custom fabrication, this project is your gateway into lightweight frame welding and vehicle assembly. If you've tackled mechanical repairs or upgrades before but never picked up a welding torch, don't sweat it-MIG welding is widely considered the easiest method for beginners to learn. It's forgiving, intuitive, and ideal for the kind of steel tubing commonly used in bike frames and cargo trailers. The goal here is to empower you to build something durable, functional, and environmentally smart-using basic tools, some elbow grease, and the same determination that's gotten you through your other DIY adventures. We'll walk you through what gear to grab (most of which can be sourced from places like eBay, Ace Hardware, or Amazon), how to set up your workspace, and where to find no-nonsense video guides to visualize each step. By the end, you'll have not only a working HPV rig-but the confidence to tackle future welding projects head-on.

Step 1: Planning, Measuring, and Frame Prep

Before the sparks fly, it's all about precision, vision, and layout. A solid sidecar build starts with a solid plan.

Begin by placing the mobility cart alongside your Huffy mountain bike to get a feel for wheel alignment, overall width, and ride height. Use chalk or painter's tape on the ground to mark where everything will sit once bolted together. You're aiming for three key anchor points that will form a rigid triangle between the bike and the sidecar. These mounts will keep everything stable at speed and across uneven terrain. Using a level and ruler, measure and record the following:

• Distance from bike bottom bracket to the front and rear mount points
• Height of the cart's frame from the ground (aim to match the bike’s axle height)
• Wheelbase alignment and sidecar wheel lead (usually 10–15% of the bike's total length ahead of the rear axle)

Cut your steel tubing (we recommend 1" square mild steel, 14-gauge thickness) using a portable bandsaw, angle grinder with a cut-off wheel, or a chop saw. Always wear eye protection and gloves. Before welding, clean every surface thoroughly with a wire brush or flap disc to remove paint, rust, or oil. This ensures clean welds and prevents splatter or weak spots. Pro Tip: Clamp the bike in a bike stand or brace it securely so it won't shift. Likewise, set the cart frame on blocks to level everything before tack welding your brackets. Watch: Pre-Welding Setup & Connector Bar Alignment

Essential Gear & Tools (Beginner-Friendly)

These tools will get you up and running for your first metal frame welding project—sourced from eBay, Ace Hardware, and Amazon.

Helpful YouTube Tutorials for Beginners

Even if you've never welded before, these creators break it down step-by-step.

Step 2: Fabrication & Tack Welding

With your measurements dialed in and your tubing prepped, it's time to bring this frame to life-one spark at a time. Think of this stage as roughing in the skeleton of your sidecar rig before you fully commit to anything permanent.

Start by laying out your steel tubing on a flat fire-safe surface-ideally with a steel workbench or a concrete garage floor. Keep your main sidecar frame rectangular or triangular for strength and simplicity. The frame should align level with the bike's rear axle and provide stable base support under the cart's wheel. Use your magnetic clamps and corner guides to hold angles square as you begin assembling the base shape.

• Double-check all angles with a speed square or framing triangle
• Use scrap tubing or temporary gussets to brace the corners before welding
• Begin tacking pieces together using short 1/2-inch welds at the joints-don't fully weld anything yet

Work slowly and let each tack cool for a few seconds before continuing. Too much heat at once will warp thin steel and throw off your geometry. After you’ve got your base done, move on to tacking the three support arms that will mount from the sidecar frame to the bicycle: one low near the bottom bracket, one high near the seat stay, and one near the rear dropout.

Alignment Tip: Have a friend hold the bike upright or strap it to a tree/post to ensure the sidecar attaches straight. Check tire alignment and ride height one last time before locking in the frame.

Watch: DIY Sidecar Frame Assembly Techniques

Step 3: Full Weld Passes & Sidecar Mounting

With the frame tacked and squared, it's time to commit. This step transforms your temporary structure into a ride-ready, load-bearing chassis-solid, reliable, and built to take a beating.

Start by checking all your tack welds. If anything shifted during mock-up, now's the time to break a tack and re-clamp. Once you're confident in your layout, begin laying full weld beads at each joint. For mild steel tubing, run your MIG welder between 90-110 amps using .030" solid core wire with CO₂ or a 75/25 Argon/CO₂ shielding mix.

• Weld in short bursts, alternating between joints to prevent warping
• Let each weld cool slightly before welding the opposite side of the same joint
• Use multiple passes on stress-bearing joints like mounts and crossbars

Once all welds are complete, clean them up with a wire wheel or flap disc on your angle grinder. Inspect for porosity (tiny holes or bubbles), cracks, or weak penetration. If you see any, grind them out and re-weld until you get clean, strong fusion. Now it's time to mount the frame to the bike. Using your industrial-strength U-bolt or bolt-on bracket kits, secure the three arms to the bike’s frame at the following points:

• Mount 1: Down near the bottom bracket or lower frame tube
• Mount 2: Mid-height, at or near the seat stay or water bottle cage bosses
• Mount 3: Rear triangle or dropout area, using existing eyelets if available

If your mounts require drilling into the bike frame, be cautious-ome bike tubing is thin and doesn-t like being modified. Use rubber bushings or washers to reduce vibration and stress. Once all three points are secure, give the sidecar a shake test. There should be zero flex at the connection points.

Road Test Tip: Start slow in an open parking lot. Practice turns and stops. Sidecars change how bikes handle. You'll feel the difference immediately.

Watch: Full Weld Techniques & DIY Bracket Mounting

Step 4: Finishing Touches, Paint, and Accessories

The hard part's done, and now it's time to give this rig some personality and protection. This step is all about durability, weatherproofing, and turning heads on the street.

First, degrease and prep the entire sidecar frame for paint. Any leftover oils from your hands or grinding dust will ruin paint adhesion. Use acetone or denatured alcohol and wipe it down with a clean rag. Lightly scuff all metal surfaces with a sanding sponge or 220-grit sandpaper to give your primer something to grip.

• Apply 1-2 coats of high-adhesion metal primer (Rust-Oleum Professional or similar)
• Let dry 24 hours, then hit it with 2-3 coats of enamel paint or a durable rattle can clear coat
• Optional: Add reflective tape, stripes, or custom decals for extra visibility

While the paint cures, think about how you want the cart itself to function. Do you want a platform to haul groceries? A secure child carrier? A mount for a cooler or toolbox? This is where your vision takes shape.

Mount the cart to your finished frame using heavy-duty hardware-bolts, washers, and lock nuts. You might also want to bolt or weld in:

• Fenders: To keep mud and water off your cargo
• Lighting: USB rechargeable LEDs or solar bike lights
• Weather protection: A tarp or plastic fairing if you ride in the rain

Once everything's mounted, go for another road test. Listen for rattles, creaks, or movement in the mount points. Re-tighten everything after your first mile. And when it feels rock solid, take a victory lap.

Paint Tip: Let everything cure for 2-3 days before hard use to prevent chipping or soft spots.

Watch: DIY Bike Sidecar Paint + Cargo Setup Ideas