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Damped Shocks, suspensions and suspended weight

22 posts in this topic

Hello

I was watching Jm1971' s http://www.flickr.co...N08/9644835806/ from the Rock Crawler course thread and I noticed that albeit the crawler can adapt it's geometry to terrain the suspension does not seem to work at all. I got the feeling that Lego models seldom achieve right suspended weight/shock hardness balance, 8110 and 9398 feel more like tumbler dolls on wheels than proper suspension designs. A model shouldn't have full extended shocks when static right?

Also I was wondering if anyone tried ever to use those damped shocks as suspension shocks. I know they are too damped and slow, just wondered if a crawler type (read: slow) can use them. I am not sure there is any benefit at all as in my experience only at speed dampening and shock speed make a difference, be it due to terrain, breaking behaviour etc. At crawler speed it looks just a matter of geometry and making ground contact and sometimes Lego shocks feel like all or nothing. I am curious about it anyways.

32181c02.jpg

Usually the videos I see when running over a small bump, the full model tilts instead of the shock compressing/extending at least partially to adapt to it. I reckon a really heavy model could work properly. I wish a slow mo video showing a lego suspension working properly. Anyone taking the callenge? :tongue:

Regulable shocks (precompression nut) even if not damped would help a lot with suspensions I guess.

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Those dampened shocks are useless. They compress easily and extend very slowly.

But yeah, a car should not be on fully extended shocks when static. I had that same problem with the mustang. It just stubled across. Now it squats a bit when you put it on the ground, and the suspension works so much better.

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Nicely working shocks! That model is huge and looks heavy, Do you remember the weight with batteries? did you lubricate the shocks to speed them up?

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Hello

I was watching Jm1971' s http://www.flickr.co...N08/9644835806/ from the Rock Crawler course thread and I noticed that albeit the crawler can adapt it's geometry to terrain the suspension does not seem to work at all. I got the feeling that Lego models seldom achieve right suspended weight/shock hardness balance, 8110 and 9398 feel more like tumbler dolls on wheels than proper suspension designs. A model shouldn't have full extended shocks when static right?

Also I was wondering if anyone tried ever to use those damped shocks as suspension shocks. I know they are too damped and slow, just wondered if a crawler type (read: slow) can use them. I am not sure there is any benefit at all as in my experience only at speed dampening and shock speed make a difference, be it due to terrain, breaking behaviour etc. At crawler speed it looks just a matter of geometry and making ground contact and sometimes Lego shocks feel like all or nothing. I am curious about it anyways.

32181c02.jpg

Usually the videos I see when running over a small bump, the full model tilts instead of the shock compressing/extending at least partially to adapt to it. I reckon a really heavy model could work properly. I wish a slow mo video showing a lego suspension working properly. Anyone taking the callenge? :tongue:

Regulable shocks (precompression nut) even if not damped would help a lot with suspensions I guess.

Lego crawlers don't need dampers, they only need springs to keep the body center of the suspension when on a flat surface, dampers would just slow the bounding and rebounding of the piston, heck if the axles and tyres are heavier than the body than the body centering doesn't even matter anyway :laugh:. The Lego chassis and tyres act as a damper in any lego model, so fast cars don't need em either. Though I still like to see all the shocks and stuff, even if there is no point to them :wub: working model ya know.

Yeah and the wheel needs to have a down stroke and a up stroke from center, so the chassis doesn't drop into any pot holes or so the tyres don't leave the ground say if it got a bit of air on a small jump/bump.

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That's the idea. In lego, you don't realyy need shocks. Springs are enough. But one must adjust the amount of springs to the weight of the car, and when making the suspension, one must take into account, that it'll set a bit when the vehicle is put on the ground.

This means, that one won't know how much spring force is required untill the completion of the model.

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Well, I think pneumatic cylinders are your best option, however they do leak over time, but they are adjustable and at full pressure are nearly impossible to move.

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A model shouldn't have full extended shocks when static right?

I think it's not that simple. Another often forgotten feature of a shock is the pre-compression. And I think Lego shocks are more pre-compressed than real shocks, that means even if they are fully extended, significant amount of force is already acting on the spring. So even if you have the exact realistic ratio between the spring force and the weight on the spring, the shock may still be fully extended.

Maybe the softer Lego springs are more realistic in that regard, but this all means that it can be pretty much impossible to make realistic suspension at particular model scales (either the soft springs are too weak, or the hard ones are fully extended).

And I think that this theory works in practice too, any time I made a suspension that wasn't fully extended under the full weight, the model felt like a huge vintage limousine, while modern cars have quite stiff suspensions. The suspension felt right for Lego when the hard Lego shocks were very close to their full extension. At least that's my limited experience in the ~1:9 scale and my models were maybe too heavy.

Edited by Lipko

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Pneumatic suspension is Always too hard.

What you can do is drill the inlets on a cylinder to 1.8mm or more, then put springs from the lego shocks inside the cylinder. That way the cylinder acts as a shocks and spring casing/mounting, and you can adjust the spring force by changing the springs inside.

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What about that shock that comes with the RC racers, quite expensive piece.

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Oh yeah, I forgot about that one, also in 8420 Street Bike. I don't have one, but I'm pretty sure the rigidity is adjustable.

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I have never had the pleasure to have one in my hand, so i wouldn't know. If someone has it, please report about its properties.

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On this MOC I made a while ago (for the suspension proof of concept and not for looks) I found it was quite soft on the springs and offered quite a bit of adjustment:

1324226287m_DISPLAY.jpg

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And I think that this theory works in practice too, any time I made a suspension that wasn't fully extended under the full weight, the model felt like a huge vintage limousine, while modern cars have quite stiff suspensions.

That's why nearly every car has a stabilisator, which is a torsion bar (some heavier Lego cars also requires this). That bar connects the two wheels in each axle, so they can't be move fully independent. If cars won't have stabilisators, then as you wrote, they would "bend" a lot with "pendular" movement.

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Nice beetle suspension :)

Thanks, totally inspired by the front suspension of the beetle..... Well spotted

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On this MOC I made a while ago (for the suspension proof of concept and not for looks) I found it was quite soft on the springs and offered quite a bit of adjustment:

1324226287m_DISPLAY.jpg

That is cool...

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Pneumatic suspension is Always too hard.

How about 1 or 2 small cylinders multiplied by a linkage?

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Something I've done for 4x4 builds with lego is to use cantilever suspensions similar to what is used in high end real 4x4 vehicles:

DSC00106.jpg

You can increase the travel length of the shock which also puts more pressure, giving the equivalent of a lighter spring.

Also did something similar with a dual spring setup, it worked amazingly well: V5mE2e3.jpg

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Something I've done for 4x4 builds with lego is to use cantilever suspensions similar to what is used in high end real 4x4 vehicles:

You can increase the travel length of the shock which also puts more pressure, giving the equivalent of a lighter spring.

Also did something similar with a dual spring setup, it worked amazingly well

I built something like that with dual shocks and it worked out pretty well.

You can see it in my trial truck teaser video below. I took out that system in the V2.

Happy building!

NXT45

Edited by NXT45

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Your model does not have dual shocks.... :look:

Also, you don't have to continuously bump topics to try to publicize your crawler.

TLH

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