Pb of elementary mechanics on the springs

[Ahmed]

Grelinette, I have no reaction from you ...
Do my last explanations seem understandable to you?
Otherwise, I will try to make a schematic diagram ...

[hic]

hic, your conception of mechanics seems as little credible as that concerning magnetism!

By a sleight of hand,
(as for magnetism)
you ignore the fact that a spring is not progressive,
therefore not very effective.

As we noticed the big brands like Citroën or Rolls-Royce
We don't have the same values, to say the least!

[hic]

hic, your conception of mechanics seems as little credible as that concerning magnetism!

By a sleight of hand,
(as for magnetism)
you ignore the fact that a spring is not progressive,
therefore not very effective.

As we noticed the big brands like Citroën or Rolls-Royce
We don't have the same values, to say the least!

Maybach, Rolls-Royce, Lexus, Citroën C4 Grand Picasso, Jeep Grand Cherokee, Cadillac (GM), Mercedes-Benz, Land Rover / Range Rover, SsangYong, Audi, Subaru, Volkswagen and Lincoln and Ford, among others

[Ahmed]

We don't have the same values, to say the least!

We especially do not have the same reading : I do not understand what you mean...
The springs are progressive, not to please me, it is only a fact; as for their "effectiveness", it consists in absorbing then restoring a quantity of energy ... not in dissipating it (except a little the leaf springs, because of the friction inherent in this device).

It is not relevant to blame the springs for not being effective for functions that are not theirs ...

[moinsdewatt]

..... the fact that a spring is not progressive,
therefore not very effective. .....:

New proof of Hic's trollism.

A spring IS progressive.

F = -kx

http://fr.wikipedia.org/wiki/Ressort_%2 ... entaire%29

[Grelinette]

Sorry for the lack of response to your comments, but as I wrote in another subject, I started a new and very exciting job: I am currently working in a workshop for autists with the project of using the horse as a support for work (agriculture, harnessing, ...).

I still a little advanced on the ideas suggested in the previous comments (bi-directional shock absorber system with spring), and I made a model of a shock absorbing traction device (also made with my group of autistic).
As soon as I have a little time, I make a video of the model of the system and I post it on the site. You will see it is fun.

I was also able to test this interesting device on a drawbar allowing to tow a specific agricultural tool (a cumulus cut in 2 ) for the collection of horse droppings in a park !!!

Certainly the principle of bi-directional damping is not necessarily very useful in this case (no interest in braking), but the traction nevertheless becomes much more flexible and smoothly.
The tests done with a well loaded trailer are quite positive at start-up and braking, but precise measurements should be made to quantify the real benefits.

Inside the bar there is a Compression spring (also allowing the damping in traction), and history to test the same system on another material, the towing hook of the small tractor is also bi-directional with 1 large tension spring (allowing system compression), coming from an old box spring! :

Picking up droppings by scraping the ground:


As soon as the bucket is full, it is switched to rolling mode:


I would like to take this opportunity to submit to you a new problem with the experimental tool presented, which still has a great need for improvement: if the tool catches a large pebble or a root, it remains blocked and the tractor stops (flexibly because the bar and the hook play their damping role!).

How to avoid hanging obstacles on the ground?

Ideas ?....

[Grelinette]

Hello,

I am updating this subject because I have new information: an elastic link between the towing vehicle and a towed mass actually seems to bring some advantages!
Video of so-called "dynamic" or "kinetic" straps:
For example: http://www.youtube.com/watch?v=Y_GnDm7Fp1E
Other comparative traction video with rigid / flexible strap: http://www.youtube.com/watch?v=011bDrSn02Y

I think this mechanical phenomenon will be interesting for animal traction.

In addition, I had the opportunity to discuss with a manufacturer of agricultural trailers who confirmed to me that according to the uses a flexible attachment would be advantageous:
- either to benefit from the kinetic energy of the tractor at start-up,
- either to soften the traction, in particular for the transport of fruits and vegetables which seem to suffer from knocks during towing.

I did not have time to make the video of the small system that I fixed on my small tractor, but at the first clearing, I fix a camera on the attachment of the tractor and I film the movement.
A priori no oscillation felt, however there are only springs (without hydraulics).

[Grelinette]

Hello everybody

I forgot to keep this post up to date but I continued my research and I come back to present the results to you.

To recall the object of my research, I was looking for a simple and space-saving system to fix between the horse and the carriage or the horse-drawn tool towed, and which absorbs the jolts of Traction (start, acceleration, coup de collar), and those of Compression (sudden braking and stopping, reversing).


I made a system which seems interesting to me because it is simple and allows to absorb the jolts in both directions, in Traction and in Compression. It works with a single "shock absorber" (*), and icing on the cake the same system works indifferently with a compressible or extensible member (spring or damper of compression or traction, elastic, silent-block, ...).
(*) Shock absorber or spring, the difference comes from the presence or not of a fluid braking the decreasing oscillations of the spring.
In the present case a simple spring is already working well because the inertia and the friction forces of the towed mass attenuate almost all the oscillations.

Curiously I have not found on the internet mechanical systems using this principle, but other more complex systems to finally give the same result of traction damping, like this one, or that one.
If you are aware of similar material, I am very interested to know it.

Before revealing this system to you, here is first a small video of a wooden assembly with the same system and which allows to compare the operation of a compression spring and a tension spring. The system is hidden to make you look for the principle of operation! Video here.

This two-way damping system is in fact an element of a more complete mechanism for returning perpendicularly the forces which are in the direction of travel (the less distance there is between horse and towed mass, the better). It also suppresses the phenomenon bracing (breakage of horse alignment / towed load).


I now seek to perfect this principle of force transfer. Here are already 2 versions: Mechanism1, Mechanism2.
I have not yet had time to do field tests with these 2 mechanisms. I'm curious to see which system will be the most functional! If you have other ideas, I am interested.

Next I will show you a video of the same shock absorber system attached to the towing hook of a micro-tractor with trailer. You will see, it is very interesting to see closely what happens during a pull! The advantages of the system seem obvious, but I have not yet made precise comparative measurements.
I think that I will find these advantages with animal traction and that the horse will feel better in its work!

[Ahmed]

Why complicate the assembly by interposing deformable structures to return the forces perpendicularly?
Why not leave on a single point of transmission?

[Grelinette]

Why complicate the assembly by interposing deformable structures to return the forces perpendicularly?
Why not leave on a single point of transmission?

Good evening Ahmed,

Several reasons, just as important:

- 2 attachment points is a standard on most horse-drawn vehicles to fix the stretcher / lifter / lines assembly.

- One point seems to me too fragile because it concentrates all the forces, unless you have an ultra strong, massive and heavy assembly. The stretchers are long and produce a significant leverage (moment of force) in the turns in traction and compression.

- 2 distant fixing points allow, as explained in my last comment, to avoid bracing (break in the alignment stretcher and front axle).

- The perpendicular reference allows to insert only one shock absorber system longer with more travel.

- Another important point: the mechanical damping system, in addition to damping the jolts, will also be used to manage the auxiliary drive on the hybrid carriage. Currently I use a force sensor which only measures traction. The data is processed electronically, it is efficient but fragile and complicated to configure: you have to plug in 1 pc (this is not always possible in practice). I hope that this mechanical system, even if it does not bring as many possibilities, will solve the drawbacks of electronics,.

- Finally, inserting it perpendicularly limits the size. For example, car shock absorbers (easy to find, economical and bcp of choice), have a length of about 40 cm, which moves the horse too far from the towed mass.

I take this opportunity to put the link of the two-way shock absorber system attached to the towing hook of a small tractor because it is the heart of the principle of the double shock absorber.
It is this system which will be inserted into the return device to absorb traction and compression with the horse. If the advantages with the horse are as convincing as with the tractor, there will be a real advantage in terms of flexibility and efficiency. As soon as I have the means, I have the solid metal return assemblies made and I test them on the carriage. (I'm leaning for the 2nd!)

In this assembly (that of the video) there is only one very simple but very rigid tension spring. As you anticipated in one of your comments, there is actually no oscillation or they are imperceptible! Here's the video.

You can see on this video that I put the system to the test (brutal acceleration and braking, reversing, turns, etc.), but that it works very well! In the trailer there are about 200 kg of logs. I would be very interested to know the peak forces when I accelerate and when I brake.