Roll-Off-Roof Gear
Observatory drive gear modified to fit 600W roof motors with 3/4" shaft. Module 4 pitch meshes with standard racks. No machining required-ready to install.
Out of stock - will ship when available
The Missing Piece Between Motor and Rack
The Roll-Off Roof Gear is a 17-tooth steel gear modified to fit our 600W Roll-Off Roof Motor and mesh with standard gate opener racks. We've bored it to 3/4" and cut a channel for a cross pin-modifications that would otherwise require a machine shop. Slide it onto the motor shaft, secure it with the collar, and your drive system is ready to move your roof.
Why This Gear?
Standard gate opener gears don't fit a 3/4" motor shaft. They're designed for smaller motors with smaller shafts, which means if you want to use a proper high-torque motor for your observatory roof, you're stuck finding a machinist or doing the work yourself.
We've eliminated that hassle. The Roll-Off Roof Gear comes pre-bored to 3/4" with a cross pin channel already cut. It drops onto our 600W motor shaft and meshes directly with standard Module 4 gate opener racks-including the Topens racks we sell and racks from other suppliers using the same standard.
Dozens of these gears are running on observatory installations right now. The gear itself is proven technology from the gate opener industry, designed for outdoor conditions and repeated cycling. Moving an observatory roof a few times a night? That's light duty compared to a commercial gate opening hundreds of times a day.
Key Benefits
Direct Fit with Our 600W Motor
The 3/4" bore matches the motor shaft exactly. No bushings, no adapters, no hoping things line up. The cross pin channel is already cut, so you're not drilling through hardened steel yourself. This gear was modified specifically for our motor-it's a matched set.
Meshes with Standard Gate Opener Racks
Module 4 pitch means this gear works with standard steel gate opener racks. Use our rack, use Topens, or use another Module 4 rack you already have. The compatibility gives you flexibility while keeping costs reasonable.
45 Steel for Durability
Medium carbon steel handles the torque and wear of repeated roof cycles. This isn't a soft metal gear that will strip under load-it's the same material used in industrial applications where reliability matters.
Tool-Free Pin Installation
The cross pin is face-mounted, so you don't need a hammer or press to install it. Slide the collar onto the shaft first, then the gear, then insert the cross pin. Tighten the collar with a hex key to lock everything in place and prevent the gear from walking off the shaft during operation.
What's Included
Standard Purchase:
- Roll-Off Roof Gear (3/4" bore, 17-tooth, Module 4)
- Cross pin
When Purchased with 600W Motor:
- Roll-Off Roof Gear
- Cross pin
- Locking collar (secures gear to pin)
Technical Specifications
| Specification | Value |
|---|---|
| Teeth | 17 |
| Module | 4 (meshes with standard gate opener racks) |
| Bore | 3/4" (19.05mm) |
| Material | 45 steel (medium carbon) |
| Mounting | Cross pin with collar |
| Rack Compatibility | Standard Module 4 gate opener racks (DDA, Topens, others) |
Integration/Compatibility
The Roll-Off Roof Gear is designed to work with:
- DDA 600W Roll-Off Roof Motor - Direct fit to the 3/4" output shaft
- DDA Drive Rack - Module 4 pitch for proper mesh
- Topens Gate Opener Racks - Standard Module 4 compatibility
- Other Module 4 Racks - Any standard gate opener rack with matching pitch
This gear is one component of a complete drive system. For a full setup, you'll also need the motor, rack, and motor mounting bracket.
Installation/Setup Reality Check
This is one of the simplest parts to install in your drive system.
Time required: 5 minutes
Tools needed: Hex key (for the collar)
Skill level: Beginner-if you can tighten a bolt, you can install this gear
Process: Slide the collar onto the motor's 3/4" shaft first, then the gear, then insert the cross pin through the face-mounted hole. Tighten the collar with a hex key to lock everything securely in place.
What You Need to Provide
From Dark Dragons Astronomy (sold separately):
- 600W Roll-Off Roof Motor - The motor this gear is designed to fit
- Drive Rack - Module 4 rack to engage the gear
- Motor Mounting Bracket - Secure mounting for the motor
You'll also need:
- Hex key for tightening the collar
Real-World Performance
Dozens of these gears are in service on observatory installations. The gear design comes from the gate opener industry, where these components handle outdoor exposure, temperature swings, and thousands of cycles per year. An observatory roof that opens and closes a few times per night is well within the gear's design envelope.
The 45 steel construction handles the torque from our 600W motor without issue. Combined with a properly installed rack, this gear delivers smooth, reliable roof movement cycle after cycle.
Complete Your Drive System
The Roll-Off Roof Gear is the interface between your motor's power and your roof's movement. Without a properly fitted gear, you're looking at machine shop visits or DIY modifications that may or may not work.
We've done the machining. The bore is right, the cross pin channel is cut, and the pitch matches standard racks. Pair it with our 600W motor and drive rack for a complete, tested drive system-or use it with compatible components you already have.
Pro tip: Purchase the gear with the motor to get the locking collar included. It's a small part, but it's what keeps everything secure during operation.
Need help? Join our Discord community for installation guides, troubleshooting, and direct support.