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Thread: Practical Physics Question.

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    Default Practical Physics Question.

    I am wanting to build the equivalent of a 3 Point hitch for my little toy Tractor so I can put on some implements I want to make like a scraper and a ripper for a bit of landscaping.

    I want to attach a length of steel tube which will Pivot on a mounting in the framework. Above that Pivot point which will be 20-40MM from the end of the tube, I will have another point at which I attach a Linear actuator which will do the lifting and pushing . Basically a Beam fixed at one end with a lifting point along it's length.

    The 2 Part question is with the leverage and the fixed pivot point, Will the actuator see a greater or lesser load than the weight of the object being lifted if the actuator is positioned closer than the half way point of the length of the Square Tube or further away?

    I know this is lever and Fulcrum stuff but with the points mucked around to the usual example, not sure which way it's going to go.
    My thought is the actuator will see a greater load but that load will decrease the farther out the attachment point is away from the fixed point.
    That will be determined in practice by the length of the ram and the amount lift and push I want which will also be negative in the case of a scraper where I want downforce to make the blade bite...... which will be a catch 22 in then ligting the back wheels and reducing traction but that's another issue which may be compensated with blade angle.

    The rating of the actuator is 600KN which I believe is 600KG so being Chinese made could be 300KG in reality or 150kg but what I have seen on the net suggests the things are not terrible if not accurately rated. The tractor is only 300KG so that's the max downforce it could get but if the weight it's lifting is multiplied, I may have to watch that.

    Really would have liked Hydraulics if they weren't so expensive (and have been looking for a log splitter with a stuffed motor but no luck) But figuring I could always buy another actuator if needed or would be wise.

    Smart peoples advice welcomed.



Look Here ->
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    Just have another closer look how I did it:




    I have the actuators working always between 90˚ and no less than 30˚ to their working lever.
    You see that I raised them with the hardwood poles to achieve that.
    The one for the shovel has a pole to increase the leverage and torque for the shovel's working angle, currently shown in the upwards position but can be tilted down about 120˚. If I lower the shovel to the ground and then tilt it, it comfortably lifts up the tractor.

    The 2 slashers have a lot of torque because they are geared down(which I did not know when I ordered them) and when I lower the rig while they are rotating they will dig into compacted ground, then I drive back and collect the softened soil and move it with the shovel. For mowing lawn they spin a bit too slow but work well if you want to REMOVE the lawn.

    600kN is about 60kg, that is not much. So if you have it attached at the middle if the arm, the end of the arm will only lift 30kg(ignoring the weight of the arm) , depending on the angle even less.
    Ideally you want to have it when the actuator is half extended at 90˚. That is roughly how I have them for the steering. Both axles are steerable, there is another actuator on the back (right hand side) not visible on the photo.
    My actuators are 1000kN so I get at least 40kg force to turn the axle at the wheels, way more than I could produce by hand. Downside of this electrical steering is the that it is slow but as I am steering both axles the response doubles and it is comfortable to drive around normal curves up to 12km/h. If I really have to turn on a plate, I just stop and wait. At some point of the steering radius the power to inner wheels is cut so all power is on the outer wheels in the apex.

    It has a password protected ludicrous mode that I haven't dared to try yet. This thing has no suspension. Would have to be on flat preferably tar road that is not available for me.

    It is designed to be remote controlled and also autonomous(robotic). Due to other issues I haven't been able to get to that property since 4 months, so that project is on the back bench ATM.
    Probably in April ...I'll Be Back !


    Edit: I should mention that I am running my 24V Actuators at around 40V. This is more about faster response time for the steering than torque. I would keep them at the rated voltage if merely needed for lifting and use 2 for more torque and redundancy. Mine have a position sensor(10k pot) for the steering comtroller.
    Last edited by Uncle Fester; 24-02-20 at 02:51 PM.
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    I like the "tractor" fester, would it not have been cheaper just to buy a second hand ride on and adapt that?
    I'm out of my mind, but feel free to leave a message...

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    Quote Originally Posted by Uncle Fester View Post
    Just have another closer look how I did it:
    Ah! has nothing on you.

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    Thanks for the info... and the scare. I thought the actuator I bought was 600Kn but looking up what I bought it's 6000 so should be OK.
    Also got me thinking about doing a loader instead of a 3 Point. I'll have to look closer at the tractor to see if I can do a Mid mount Pivot to split the weight between all the wheels.
    Having it all hung off the front may be counter productive to traction and overload the axle as well. Wish Mine was 4WD as well as 4 Wheel steer.

    What power actuator do you have have on your shovel and will it do meaningful work moving Dirt OK?

    A scraper may be useful to me as well as a ripper but Thinking about it I'll probably want a way to move the soil around as well.

    Spose even if I do both, still a lot cheaper than buying another tractor with a bucket. Been looking long enough that's for sure. Full size tractors often o for a lot less than the compact ones But a full size tractor wouldn't get round my little block too well. I would really like one of those Mini digger/ excavators on a frame type thing but they don't often come up.

    Thanks for the food for thought.

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    Quote Originally Posted by lsemmens View Post
    I like the "tractor" fester, would it not have been cheaper just to buy a second hand ride on and adapt that?
    I am a man of electricity and have everlasting 'free' access to it.
    Horses and combustion engines are not my thing.
    I can't tame them the way I like to.
    They are high maintenance and moody.
    I don't like the noise they make and all the stuff they need to consume and expel.

    The business end will be modular and replaceable with a robotic arm that will have all kinds of electric powered attachments.
    It is also not supposed to be a ride on, that is just an optional extra.
    Think of it as a far more clumsy looking version of this:
    but for outdoor use with more power and higher speed and longer run time. Might even have a couple of 200W panels as a sun shade but finding it's charge port on it's own from a fixed panel location is probably more practical.


    I just wish I could have kept it at home to build a lot more on it but it took too much space away in my garage and my wife does not like it.
    Now I have access to my n-scale model train again, that is also in the 'garage' so I am building sometimes on that which is currently running with 5 PIC micros, more than the tractor has.
    My wife likes the train a bit better at least.
    Last edited by Uncle Fester; 24-02-20 at 11:07 PM.
    Update: A deletion of features that work well and ain't broke but are deemed outdated in order to add things that are up to date and broken.
    Compatibility: A word soon to be deleted from our dictionaries as it is outdated.
    Humans: Entities that are not only outdated but broken... AI-self-learning-update-error...terminate...terminate...

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