[WIP] Azure Racer XL

[Erik Leppen]

11 hours ago, Didumos69 said:

Yes softer, but the car's weight will compress the springs just as far as with shorter arms.

Suppose you have 6l suspension arms (5l center to center), you have travel of 2 studs and the car sinks in its suspension by 1 stud (50%). Now when you extend the suspension arms to 9l (8l center to center), while preserving the exact layout of the springs, you get roughly 8/5 times the travel (>3l) and the car still sinks in its suspension by approximately 50%.

By this logic, if you extend the suspension arms to 500L, you would get 100 times the travel but still the shock compressed by 50%? (ignoring the suspension arm's own weight). I'd say this conclusion is absurd, yet it follows your logic. So I'd say your logic has a mistake somewhere.

Looking up some definitions online, I conclude the spring has potential energy (called "elastic potential energy"), that is stored in the spring by compressing it, and when decompressed, does work to push the vehicle upwards (against gravity). Energy translates to work, and the amount of work is therefore fixed. Work is force times distance, so if distance (= travel) increases, force (= weight) can only go down. See Work (physics) - Wikipedia -> "work and energy".

of cousre, you could also test it. If you have any MOC or set or WIP with suspension lying around, take the wheels off and attach 15L beams to the lower suspension arms, basically extending their length, and see if it, at rest, the springs are still compressed the same. Without testing, I predict they will be more compressed and the vehicle will not be lifted.

Anyhow, i think this is slightly off topic, so sorry for interrupting :)

[Didumos69]

1 hour ago, Erik Leppen said:

Anyhow, i think this is slightly off topic, so sorry for interrupting :)

You are quite right @Erik LeppenLeppen. And you're also right about the travel etc. I just tested it and the springs compressed substantially more. I do wonder where my reasoning is wrong. Will give that some study. Anyway, I won't be bothering this topic anymore too.

[howitzer]

2 hours ago, Didumos69 said:

You are quite right @Erik LeppenLeppen. And you're also right about the travel etc. I just tested it and the springs compressed substantially more. I do wonder where my reasoning is wrong. Will give that some study. Anyway, I won't be bothering this topic anymore too.

Sorry for continuing the offtopic, but the suspension arms work like a lever, and extending their length is like extending the lever travel which translates into greater force.

The comments on this topic is btw. a great demonstration why I like this forum: proper advice on how to make the MOC better and good discussion about the reasons why something works better than something else while still keeping the discussion polite and good-spirited.

[JLiu15]

On 11/29/2020 at 2:18 AM, amorti said:

The front hubs are much better than the current ones, as the ball joints can't pull out.

Yes - that's why I decided to use them for this MOC. For such a fast MOC you gotta make sure everything is sturdy and that there's no weak points.

On 11/29/2020 at 4:41 AM, Erik Leppen said:

By this logic, if you extend the suspension arms to 500L, you would get 100 times the travel but still the shock compressed by 50%? (ignoring the suspension arm's own weight). I'd say this conclusion is absurd, yet it follows your logic. So I'd say your logic has a mistake somewhere.

Looking up some definitions online, I conclude the spring has potential energy (called "elastic potential energy"), that is stored in the spring by compressing it, and when decompressed, does work to push the vehicle upwards (against gravity). Energy translates to work, and the amount of work is therefore fixed. Work is force times distance, so if distance (= travel) increases, force (= weight) can only go down. See Work (physics) - Wikipedia -> "work and energy".

of cousre, you could also test it. If you have any MOC or set or WIP with suspension lying around, take the wheels off and attach 15L beams to the lower suspension arms, basically extending their length, and see if it, at rest, the springs are still compressed the same. Without testing, I predict they will be more compressed and the vehicle will not be lifted.

Anyhow, i think this is slightly off topic, so sorry for interrupting :)

I think you're spot on with this - we learned about this in my physics class last year (I'm currently a second year engineering student) and using physics terminology explains it really well.

Edited November 30, 2020 by JLiu15