28d Crown Gear. In-Line Modular for Axles 2.38mm

The Slot.it modular inline crown gear for precise millimetre transmission adjustment

The 28-tooth In-Line Modular Crown SIGM28I from Slot.it is designed for inline motor setups —motor aligned with the rear axle— where precise transmission adjustment makes the difference between a well-tuned car and one with play that detracts from performance.

Technical specifications

• Number of teeth: 28
• Mounting type: Inline (longitudinal motor, in line with the rear axle)
• System: Modular — two-piece crown for easy assembly and disassembly without removing the axle
• Compatible axle diameter: 2.38 mm
• Pack contents: 1 crown + 3 adjustment shims of 0.1 mm

Compatibility and spacers

The Slot.it modular system requires the use of a spacer to secure the crown to the pinion with the correct spacing. The SIGM28I is compatible with two pinion sizes:

• 5.5 mm pinions: used with the SIGMF55 spacer (not included).
• 6 mm pinions: used with the GMF60 spacer (not included).

The three included 0.1 mm shims allow for precise lateral positioning of the crown, eliminating play and ensuring a clean engagement between crown and pinion.

Advantages of the two-piece modular system

Compared to single-piece crowns, the modular design greatly facilitates work on the bench: it is possible to mount and dismount the crown without needing to remove the rear axle from the chassis. This speeds up gear ratio changes between sessions, which is highly valued in club racing where time between runs is limited.

Recommended applications

A 28-tooth crown offers a moderate-long gear ratio. It is particularly suitable for:

• Circuit layouts with long straights where top speed is important.
• Inline setups where small pinions are already used to multiply the reduction.
• Preparations aimed at GT classes or prototypes with adjusted transmission regulation.

Assembly and preparation

For correct assembly, it is advisable to clean the axle of any grease residue before placing the crown. The adjustment shims are positioned between the crown and the axle support or the pinion depending on the available space in the chassis. It is recommended to check the engagement by turning the axle by hand before connecting the motor: it should roll smoothly and without any tight spots.

Common mistakes

• Forgetting the spacer: the modular crown is not properly secured to the pinion without its corresponding spacer (SIGMF55 or GMF60 depending on the pinion used). Ensure you have it before mounting.
• Not using the shims: omitting the adjustment shims can lead to incorrect lateral engagement, generating noise and premature wear.
• Confusing inline with sidewinder: this crown is designed for inline configurations. In a sidewinder setup (motor parallel to the rear axle), crowns of different geometry are used.

Frequently asked questions

Are the spacers included in the pack?

No. The pack includes only the crown and the 3 shims of 0.1 mm. The SIGMF55 spacers (for 5.5 mm pinions) and GMF60 (for 6 mm pinions) are purchased separately.

Can I use this crown in a sidewinder setup?

No. The SIGM28I is specifically designed for inline configurations, where the motor is in line with the rear axle. For sidewinder, Slot.it offers crowns of different geometry.

What are the included 0.1 mm shims for?

They allow for precise adjustment of the lateral position of the crown on the axle, ensuring optimal engagement with the pinion. Multiple shims can be combined to achieve the desired spacing.

What advantage does the two-piece design have over a conventional crown?

It allows for mounting and dismounting the crown without removing the rear axle from the chassis, simplifying gear ratio changes and reducing preparation time between sessions.

Which Slot.it chassis is this crown compatible with?

It is compatible with Slot.it chassis that use 2.38 mm axles in inline configuration. Check your chassis documentation or the Slot.it catalogue to confirm specific compatibility with your model.

The Slot.it SIGM28I is a 28-tooth inline modular crown gear for 2.38 mm axles, compatible with 5.5 mm pinions using the SIGMF55 spacer and 6 mm pinions using the GMF60 spacer. Includes 1 crown and 3 shims of 0.1 mm for precise lateral adjustment. Ideal for slot car racing setups requiring fast gear ratio changes and accurate inline drivetrain tuning.