Heya,

im gonna preface this by saying, yes i used AI to go over my Text to make it make more sense since im not an native english speaker.

I’m trying to properly tension a new timing belt on a machine and would appreciate some help from someone familiar with Optibelt timing belts.

Here is a Link to the Optibelt documentation regarding proper belt tensioning:
https://web.optibelt.com/en/timing-belts-rubber/optibelt-omega-high-power-12644579495483?attribute%5Bprofile%5D=8M&attribute%5Barticle_number%5D=1280+8M+85+HIPO+&attribute%5Bnominal_length_mm%5D=1280
https://a.storyblok.com/f/192292/x/2d92ee5443/optibelt-tm-rubber-timing-belt-drives.pdf
Also a photo of the setup without the belt installed. The measurements shown in the photo are my own approximate measurements.
I’ve also attached a photo of the motor nameplate.

Belt / drive information

• Belt: Optibelt Omega High Power 8M
• Belt length: 1280 mm
• Belt width: 85 mm
• Motor pulley: 48 teeth, approximately 120 mm diameter
• Gearbox pulley: 44 teeth, approximately 110 mm diameter
• Center-to-center distance: approximately 457 mm
• Motor: 16 kW
• Gearbox output speed: rated for either 600 or 1200 RPM
• 3-phase system, located in Germany

The machine is from 1995 and had originally a belt of the same type installed (Contitech HTD 1280 8M), but I had to remove the motor for maintenance. I’ve now bought a new belt and need to get the tension back to the correct value.

Operating conditions

The motor starts via star-delta. It doesn't ramp up particularly slowly — it reaches operating speed in less than a second.

There aren't normally huge shock loads.

Typical current readings are approximately:

Low speed:

• Idle: ~1.5 A
• Under load: ~10 A

High speed:

• Idle: ~3.5 A
• Under load: ~14 A

When switching from low to high speed, I've seen a brief current spike of up to approximately 40 A, but this only lasts for a fraction of a second.

What I'm trying to determine

Could someone help me calculate the appropriate static belt tension for this setup based on the Optibelt documentation? Im not an engineer, just the owner of my small Stonemasons workshop but trying to do it right. I dont particularly understand some of the Calculations in the Manual, i feel like the diagram does only show half of the things i need to calculate the tension.

More importantly, I don't have the Optibelt tension measuring tool. I'd therefore like a practical way to set the tension using belt deflection with a known applied weight/load. And sanity check with a Sound frequency tester i have from my brothers guitarlessons

Ideally, I'd like to know:

1. The recommended belt tension in N
2. What this corresponds to in terms of deflection (mm) at a known applied load, preferably something I can reproduce using kilograms/weights
3. The expected natural frequency in Hz, so I can tension the belt by deflection and then sanity-check it using a frequency/tension app on my phone

I'm deliberately including as much information as I have, and think would be useful.
If there is additional information needed to calculate this properly, please let me know what measurements/specifications I need to provide.

Thanks in advance!