How to Amplify Torque with Gears When Rotary Damper Lacks Torque

Due to its thin model, the continuous rotation damper is ideal for lids with small mounting space, such as electronic piano lids. However, the continuous rotation damper has the disadvantage of lower torque than when a general partial rotation angle damper is mounted, due to its simple structure of stirring viscous material. Therefore, a method to amplify the torque by incorporating gears is sometimes used to achieve a higher damper effect. For lids closed horizontally, it is common to install segment gears due to their structure, but the torque calculation method for rotary dampers is a bit more complicated than for free fall.

In this article, we will explain in detail the torque calculation method when the continuous rotation damper is assembled on a segment gear to amplify the torque, showing an example.

Torque calculation method when a polyacetal plate 230 mm wide x 60 mm long x 10 mm thick is used as a lid
(Specific gravity of POM | Polyacetal = 1.42 g/cm³)

The lid of the small box used for this calculation has a small mounting space and cannot be fitted with a partial rotation angle damper, so a continuous rotation damper is used. We use TD88, which has the thinnest shape among TOK’s continuous rotation dampers that as the base. We calculate and confirm whether TD88 can be used for this lid, and also consider the specifications of the segment gear.

The weight W of the lid is calculated as follows
W = (230 x 60 x 10) / 1000 x 1.42 = 195.96 [g] = 0.19596 [kg].

Distance L from the center of rotation to the center of gravity of the lid as approximately half the length ℓ of the lid,
L = ℓ/2 = 60 [mm] / 2 = 30 [mm].

The torque T₁ required for lid damping is
T₁ = w x g x L = 0.19596[kg] x 9.8[m/S²] x 30[mm] = 57.61[mN･m].

TD88 has a maximum torque of 40[mN･m] at 30[min^-1], which is insufficient for torque T₁, so the gear train is used to gain torque.

Gear specifications for TD88: module m = 0.8, number of teeth Z₂= 11

Since to double the torque, the number of teeth must be doubled,
Number of teeth Z₁ = 22

We can see that TD88 can be used by incorporating a segment gear with 22 teeth to the lid.

Also, the torque T₂ required for TD88 to the torque T₁ of the lid, is calculated by the following calculation.
T₂ = Z₂ ／ Z₁x T₁ = 11 ／ 22 x 57.61 ≒ 28.8 [mN･m].

In other words, a product close to T₂ can be selected as “TD88L1-300” with a torque of 30[mN･m].

In this calculation, the speed ratio is 2:1 because the torque is twice the damper torque.
TD88L1-300 produces 30[mN･m] of torque at a rotational speed of 30[min^-1], so the average closing speed of the lid at this time is half that speed, 15[min^-1].
If this speed is too slow, the lower torque TD88L1-200 may be more optimal than TD88L1-300.

In this case, we were able to apply TD88, but if TD88 does not provide enough torque, another continuous rotation damper, such as TD58 or TD62, may be used.
The torque calculation method for the case where a continuous rotation damper is incorporated with a segment gear described in this article can be calculated by simply entering numerical values on the automatic torque calculation page. We hope you will find it useful.
TOK rotary damper website also provides torque calculation methods for various other types of rotary dampers, so please take a look at these pages as well.