Pb of elementary mechanics on the springs

[Flytox]

To simplify the system you could use rubber which could serve as a spring et simultaneously. In the 70s, Hesketh (F1 manufacturer) had laid a suspension like this. The stiffness was adapted by changing the shape of the rubber cone and the damping by changing (the quality?)



https://www.google.fr/search?q=but%C3%A ... 44&bih=709

[Grelinette]

I made a small prototype to test a simple system that dampens both traction and compression with a single single spring of any model (traction or compression), the 2 types work very well. I think that the effects, if they are really positive, will be found for the traction of my horse.

I mounted the mechanism on the drawbar of a small trailer and on the towing hook of a small tractor.

(nb: this drawing is only an example for a better understanding! ).

For the moment, I only test with simple and common springs (traction and compression, without oil or air) and I do not observe any resonance phenomenon:

- When the engine starts, the tractor moves forward, the drawbar of the trailer gradually lengthens a few cm, and as soon as the tension becomes sufficient, the trailer gradually follows, smoothly noticeable.

- Braking, the tractor idles and the drawbar of the trailer compresses under the effect of the kinetic energy of the trailer which gradually stops, only retained by the tractor which comes to a stop.

In this case, it's like self-braking trailers except that my trailer has no brake, it's just progressive braking by holding the tractor.
It remains to be seen whether this braking of the trailer is really more effective with this system, in other words, is it more effective when the kinetic energy acquired by the trailer (and absorbed by the spring) is gradually restored to the stopped tractor or moving ?…

For now, the real advantage that I see is the elimination of jolts and "hard" shocks, which already seems good to me to reduce wear and breakage. (I have already twisted and broken my towing hooks and tow bars several times during severe impacts).

It now remains for me to make comparative tests in real and specific situations to see if the system brings real advantages in this mechanical traction and braking.

First by comparing the results with and without the system fitted with a simple spring, then with and without the system fitted with a real shock absorber (oil or air, mountain bike shock absorber type):

- take out a bogged down trailer
- hill start with a heavily loaded trailer
- braking on slippery ground
- starts and brakes with fragile load (eg a bucket full of water)
- Etc. ..

If you have ideas for simple tests, I am interested.
Then I will go to the tests with my horse-drawn equipment.

The ideal would be to make precise measurements of the forces at work, at start-up and at braking to draw comparative curves, but I would need sophisticated measurement equipment.

(I made a short video. If some people want to see what it is, I send you the link by MP.)

Now another mechanical problem arises:

The length of a spring or shock absorber (from 20 cm for a mountain bike cushioning to 40 cm or more for a car) is not easy to insert in the reduced space which separates the tractor from the trailer, or the horse in his charge. Remember the sketch from my first post:


It would therefore be necessary to return the direction of the forces in red in the perpendicular direction indicated by the blue arrow, which would also allow to bring together and concentrate the 2 action points (red) in 1 only (blue):


This would also have the advantage of removing the effect of "buttressing", that is to say the" break "in the pulling line, for example the problem of a drawer with 2 handles which become blocked when only one handle is pulled.



I look forward to your ideas, comments and advice on these two points of mechanics! ...

[Ahmed]

The travel of these stops remains very small and the function which is sought here supposes a certain amplitude ...

[Grelinette]

To simplify the system you could use rubber which could serve as a spring et simultaneously. ...

While looking for a traction damper system I actually found this system interesting:


with this argument curve which remains to be confirmed:


But as Ahmed says, the damping amplitude is too low, and it does not allow adjustment. I also think there is rapid wear of the rubber base.

[Flytox]

Put a pin and "shock / spring" at the orange point?

[Grelinette]

In the same subject as that treated in my post (animal traction) and my questions, namely the damping of the forces in games in traction and braking to avoid shocks and jolts, here are 2 new traction damping systems or pressure that I found on the net and that relate to motorcycles.

The principle of the first seems to me complicated and not very functional because if one of the shock absorbers works in the right direction (compression), the other will be actuated contrary to its normal operation (traction) and therefore in abutment ... unless the principle of the mechanism escapes me on certain operations! ....

System 1


Another principle but which dampens, a priori (for the same reason of abutment of the shock absorber) that the inertia of the trailer when braking:

System 2

Note the use of mountain bike shock absorbers which have the advantage of being compact, adjustable, equipped with a spring and a fluid, and economical.

What is interesting is that the question of damping the towing forces arises, especially with a motorcycle, and that some users have devised systems to answer it.
These assemblies would be much more efficient and simplified with the system that I am currently testing.

[Forhorse]

The principle of the first seems to me complicated and not very functional because if one of the shock absorbers works in the right direction (compression), the other will be actuated contrary to its normal operation (traction) and therefore in abutment ... unless the principle of the mechanism escapes me on certain operations! ....

One is used for acceleration, and the other for braking ...

[Grelinette]

There is one (cushioning) which is used for acceleration, and the other for braking ...

Except that this type of cushioning only works in compression: if one compresses, the other must stretch, or it cannot, it is in abutment!
(try to stretch this type of mountain bike cushioning, it's not possible)

[Forhorse]

Precisely, that's why there are two ... they work in reverse: when one is in abutment because in traction, the other work in the normal direction, and vice versa.

[Grelinette]

Precisely, that's why there are two ... they work in reverse: when one is in abutment because in traction, the other work in the normal direction, and vice versa.

If the motorcycle starts, the upper shock absorber will compress, and conversely, the lower one will “should” lengthen, but this type of shock absorber cannot lengthen. (I tried)

So, a priori, the explanation is that they are pre-stressed (the SAG), therefore slightly compressed, one is the other so that if one compresses, the other decompresses by the same length. Their travel is therefore reduced by half (if the same start-up and braking travel), and in maximum travel, there is necessarily a force which pulls negatively on one of the shock absorbers.

That said, this assembly is very complicated because it requires 2 pre-stressed shock absorbers while only one at rest is sufficient!