Help with my Sky chairs

[RazerTDI]

Hi all,

i'm working on a motorized technic sky chairs and it's my first project with Technic. I've build most of it but i have some troubles that stopped my work.

Here's some photos of my setup:

https://ibb.co/TmXXbR3
https://ibb.co/VCmVLhH
https://ibb.co/BzhRZQd

Problems:

1. Cable slipping and cable's attach to sky chair. The best solution i've found is in the photos but sometimes the cable exit from the wheels or when the chair turn back, it drops down.

The chair is not very stable with this solution.

2. Traction: even if i used a rubber band around the big wheel, the cable continues to slip sometimes.

 

For the cable i use this:

Dark Bluish Gray
String, Cord Medium Thickness 300cm
Part No: x77cc300

and for the big wheels i use these:

Dark Bluish Gray
Wheel 75mm D. x 17mm Motorcycle
Part No: 88517

I also check this topic for any advices but whithout results:

Can you help me?

Thank you very much

Regards,

 

Alessio

Edited May 6, 2020 by RazerTDI

[Lakop]

Hi,

I like what you are trying to do. The real sky chairs (or sky lifts) have a system that moves it along the rope, it has it's own clamping system. there is a video on youtube called the LPA grip that explains the system. Your chair is fixed to the rope whereas the real system moves along the rope. Fixing it to the rope comes with obvious issues. I wish you luck in your project.

H

Edited May 6, 2020 by Lakop

[1980SomethingSpaceGuy]

A lot of the answers you're looking for are here, I think:

That is:

A ski lift (that's how we call them here in Switzerland) uses a cable under tension. You'll either need heavy weights or a strong structure to hold both stations in place. Luckily, your setup should allow for a decent Technic superstructure under the white plates figuring the snow slope. By increasing the tension, you'll reduce the slip on the driven wheel. 

It appears you'd rather use wheels with tyres (and rely on their grip) than just rims with added rubber tape or others. Using a stack of 2 motorcycle wheels create a nice groove that holds the cable in place, but the grooves of a single motocross tyre may work in your case too. 

Using non Lego for the cable is usually deemed acceptable. A bit of elasticity is welcome for the purpose, and hard to find and maintain with official parts. 

Then, your setup matches the simplest scheme; horizontal end stations, 2 angles, slope in between, no intermediate pylon:

Angles should be dealt with at least 4 wheels, on levers by pair. As in:

The green spot and the points where the orange meets the red are articulated. This provides the necessary smoothness for the chairs cable linkage system to go through. 

For the latter, catching the cable between 3 half bushes as in 

seems to work well. 

Good luck with your build! Keep us updated! 

Edited May 7, 2020 by 1980SomethingSpaceGuy

[RazerTDI]

Hi all,

here's a little update. I solved the traction problem and the ski chairs attack to the cable.

Now it's work but it's not so smooth. For example sometimes the chairs are blocked by the wheel (first image) instead of passed below (second image).

I release a little bit the cable but the situation doesn't change. i also tried a bigger wheel but it's worst

Edited May 13, 2020 by RazerTDI

[1980SomethingSpaceGuy]

As stated in my previous post, when there's too much of an angle, you have to do this:

2 wheels are not enough. 4 is a minimum, but you may want to go up to 8, on the same principle (balanced tree). The more you have, the smoother it gets.

[Andman]

20 hours ago, RazerTDI said:

I solved the traction problem and the ski chairs attack to the cable.

How did you solve it? By increasing the contact surface between the rope and the wheel? Something like that: 

Looks like your rope could fit at least two times in that little gap.

[RazerTDI]

Hi all,

here's another update. I've changed the number of the wheels in the base station like this:

And it works better then the previous one but very often, after the ski chair has passed, the cable falls outwards but there's no reason because the two stations are perfectly aligned ( 2nd photo)

Any suggestions?

On 5/14/2020 at 9:12 AM, Andman said:

How did you solve it? By increasing the contact surface between the rope and the wheel? Something like that: 

Looks like your rope could fit at least two times in that little gap.

I solved the traction problem putting some rubber band around the wheel with the motor:

It's not looking good but it works.. Maybe in the future i build a roof so i can hide it

Edited May 15, 2020 by RazerTDI