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Old 11-10-2022 | 06:25 PM
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John_M_
 
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Originally Posted by 1967brutus
No doubt a paved runway would help with the legs "as is", but here's the nasty thing: that nose leg suspension ain't right.
The swingarm in extended position is near vertical, while the cantilever acting on the vertical spring is near horizontal.
Now when the plane rolls, due to this setup, the slightest bump will push the wheel backwards, compressing the spring.
This will bring the swingarm towards horizontal, but the cantilever towards vertical. This changes the springing geometry such, that the springforce is regressive instead of progressive. The further the suspension is compressed, the lower the returning force becomes.I tested this with weights, and at a given additional weight that will NOT compress the extended spring, when the nose is pushed down the spring will not return.

So when the plane rolls down the runway, the suspension compresses but won't come back.
For the maiden I improvised with a few tie-raps around the plunger, but that basically limited the spring travel "hard", which resulted in a bad landing.
https://www.youtube.com/watch?v=BZFwc3aQn2w
So now I put a few O-rings around the spring plunger, that add a bump of additional springforce about halfway through the travel, and that should cure the issue.

Attachment 2272450
Ahh yes I understand... Is it possible the model has a nose down stance when the model is static on the ground, it would have a negative wing incidence ... that would aggravate the issue, as the models ground speed increases so would the downward pressure on the nose gear... can you raise the nose stance so the wing has a positive incidence sitting on the ground?

***EDIT***
Never mind I just saw your photos of it sitting on the table, it looks like it has a good positive stance on the ground.




Last edited by John_M_; 11-10-2022 at 06:40 PM.