# Teeter system or Teeter/coning hinge

#### russatfirstoff

##### Newbie
I am building a Coaxial 2 person helicopter. I initially designed a 2 blade teetering system. But I have concerns about blade collision when beginning to rotate the 2 teetering assemblies. I saw a R22 helicopter has a teetering hinge in addition to 2 coning hinges. See the picture. Can somebody explain the function of this system as it starts to rotate from 0 RPM to full rotor speed? Is the teetering hinge required with each blade on its own coning hinge?

#### Attachments

24 KB · Views: 15
The teetering hinge is to counteract dissymmetry of lift through flapping up on the advancing side and down on the retreating side, like any other teetering system. This happens whenever there is translational forward speed, which typically only begins after full flight rpm has been reached. Everything is underslung from there to cope with what would be lead-lag forces, by small spanwise shifts in c.g. position.

The coning hinges are there to cope with lifting loads as collective pitch is added. The rotor disc can be flat if there is no lift generated, for example, while spinning up on the ground before pulling any pitch. As load is increased, the tips will reach upward to make a cone. This makes stress that can be absorbed by bending, or relieved by allowing upward flexing through a pair of coning hinges.

In short: teetering is for dissymmetry of lift with translational speed, and coning is for relieving stress from the spanwise lift distribution from collective pitch. For spin up sitting on the ground with no translational airspeed and flat collective, no hinges need be active.

Last edited:
Yes you answered my question perfectly. Thank you very much.

The teetering hinge is to counteract dissymmetry of lift through flapping up on the advancing side and down on the retreating side, like any other teetering system. This happens whenever there is translational forward speed, which typically only begins after full flight rpm has been reached. Everything is underslung from there to cope with what would be lead-lag forces, by small spanwise shifts in c.g. position.

The coning hinges are there to cope with lifting loads as collective pitch is added. The rotor disc can be flat if there is no lift generated, for example, while spinning up on the ground before pulling any pitch. As load is increased, the tips will reach upward to make a cone. This makes stress that can be absorbed by bending, or relieved by allowing upward flexing through a pair of coning hinges.

In short: teetering is for dissymmetry of lift with translational speed, and coning is for relieving stress from the spanwise lift distribution from collective pitch. For spin up sitting on the ground with no translational airspeed and flat collective, no hinges need be active.

That is awesome, no extra wordiness! Just the minimalist exact description.....
A++!

The teetering hinge is to counteract dissymmetry of lift through flapping up on the advancing side and down on the retreating side, like any other teetering system. This happens whenever there is translational forward speed, which typically only begins after full flight rpm has been reached. Everything is underslung from there to cope with what would be lead-lag forces, by small spanwise shifts in c.g. position.

The coning hinges are there to cope with lifting loads as collective pitch is added. The rotor disc can be flat if there is no lift generated, for example, while spinning up on the ground before pulling any pitch. As load is increased, the tips will reach upward to make a cone. This makes stress that can be absorbed by bending, or relieved by allowing upward flexing through a pair of coning hinges.

In short: teetering is for dissymmetry of lift with translational speed, and coning is for relieving stress from the spanwise lift distribution from collective pitch. For spin up sitting on the ground with no translational airspeed and flat collective, no hinges need be active.

So how is this achieved on a system that doesn’t have coning hinges such as a Jet Ranger? I am guessing just the flexibility of the blades or perhaps built in cone like we did in Dragon Wings hubs?

A bit of both. Two or three degrees of precone in the head is common with bending to take care of whatever else is needed.

In terms of angle-degrees, how far will the coning hinges allow the blades to cone before they hit hard limit stop?

I'm sure it's in some Robinson documents somewhere but I don't have that figure handy. However, I do recall during preflight inspections pushing up on each blade to confirm the flex of the coning hinges, and getting travel of several inches before I ran out of arm reach.

Thank you very much for your replies. You helped alot.

Replies
0
Views
965
Replies
6
Views
783
Replies
5
Views
1K
Replies
1
Views
708