Single-lobe Rear Pulley for S.P. Crown - SCA 7mm

Millimetre Precision in Angular Transmission, Directly from the 3D Printer of 3DSRP

When working with an angular transmission in a 1/32 competition car, every gram and every tenth of a millimetre in the drivetrain counts. The Single Lip Rear Pulley from 3DSRP (ref. SRP018120) meets this demand with a component manufactured using high-precision FDM 3D printing, specifically sized for 7 mm cores of S.P. and SCA crown gears in angular configuration.

Function and Performance

The single lip of this pulley serves a very specific function: to guide the belt laterally without adding unnecessary friction on the other side. Compared to double lip designs, the single lip reduces the contact surface with the belt on the flanks, resulting in lower lateral friction and a more direct power delivery to the rear axle.

Designed for an angular layout, it fits mounts where the motor is not aligned parallel to the rear axle, but at an angle — the anglewinder configuration — where the correct positioning of the pulley is crucial to avoid vibrations and premature belt wear.

Manufacturing and Materials

3DSRP uses FDM (Fused Deposition Modeling) technology with technical materials that withstand the usual conditions of high competition on track: temperature generated by the motor, torsional stresses during acceleration and braking, and repeated usage cycles during long sessions. The result is a part with good structural integrity and a significantly lower weight than machined aluminium or brass pulleys, a direct advantage in reducing rotational inertia.

Compatibilities

• S.P. crown gears with a 7 mm core in angular layout.
• SCA crown gears with a 7 mm core in angular layout.
• 1/32 scale chassis with belt drive in anglewinder configuration.

Before mounting, check that the diameter of the rear axle of your chassis matches the 7 mm core and that the width of the belt you are using is compatible with the pulley channel.

Mounting and Preparation

The mounting does not require special tools. It is advisable to clean the rear axle of grease or dirt residues before inserting the pulley to ensure a firm fit. During setup, align the pulley with the crown gear, checking that the belt runs parallel without lateral tensions: even minimal misalignment can result in mechanical noise or asymmetric belt wear throughout the session.

If the fit on the axle is slightly loose, a small application of low-strength thread locker on the core resolves the issue without hindering subsequent disassembly for maintenance.

Common Errors

• Confusing angular layout with inline or sidewinder: this pulley is designed for anglewinder. In inline or sidewinder configurations, the geometry of the drivetrain is different and it may not be the suitable part.
• Over-tightening the belt: an overly tight belt increases the load on the bearings and negates the lightweight advantage of the pulley.
• Not checking the core of the crown gear: S.P. and SCA offer crown gears with different cores; ensure yours is 7 mm before ordering.

Frequently Asked Questions

Is it suitable for crown gears from other brands with a 7 mm core?

The pulley is sized for 7 mm cores of S.P. and SCA crown gears. If another brand uses exactly the same core standard, it could be compatible, but we recommend verifying it before mounting, as small tolerance differences can affect the fit.

What real advantage does the single lip design offer over the double lip?

The single lip guides the belt on one flank, reducing lateral friction on the free side. This is especially useful in narrow belts and in mounts where alignment is very precise, as the double lip can generate slight additional pressure if there is the slightest deviation.

Does FDM printing withstand the heat generated by the motor in competition?

3DSRP uses technical materials in its FDM prints designed to withstand the thermal and mechanical conditions typical in 1/32 slot racing competition. In recreational or club use, the durability is more than sufficient.

Do I need any special tools for mounting?

No. The mounting is straightforward and does not require specific tooling. It is advisable to have a belt alignment tool on hand to check the parallelism between the pulley and crown gear after installation.

Can I use it in a sidewinder or inline mount?

This pulley is designed for anglewinder drive configurations. In sidewinder or inline setups, the transmission geometry is different, so it is advisable to consult the 3DSRP catalogue to find the appropriate reference for each type of mount.

The 3DSRP SRP018120 single lip rear pulley is a 3D-printed FDM component engineered for angular (anglewinder) belt drive transmissions in 1/32 scale slot cars. Designed to fit S.P. and SCA crown gears with a 7 mm core, it delivers precise belt guidance, reduced lateral friction, and a significant weight saving compared to machined metal pulleys — a real advantage for improving rotational inertia and overall drivetrain efficiency in club and competition racing.