Mechanical Physics Question.

[Piemaster]

As I've already started, why it's easier to move the tractor using the wheel than just pushing it, it's an increase in the length of the lever. You could of course just eat more spinach.

 

[midlife]

Has anybody mentioned work / energy as its a force being delivered over a distance (Joules) ?

Shaun

 

[vernon]

You could of course just eat more spinach.
View attachment 118698

Or get a smaller tractor.

 

[Markymark]

I agree with Descartes on this question. We simply can't know.

Please expand?

 

[Markymark]

No. I'm large enough as it is.....





(Descartes said we can't know anything because we can't trust our own senses.....all of this might be a dream or a wicked plot by someone trying to fool us)

Ah. The separation of body and mind?everything can be doubted except my mind?

 

[twentysix by twentyfive]

all of this might be a dream

If it is a dream it's a very persistent one. (I think that was Einstein - but I might have dreamt that)

 

[Seevio]

No matter how you look at the problem - from a torque to the hub idea or a linear push from the rear idea, the amount of force required to get the tractor to start moving is 500N (rounded up for sanity). Now, see the tractor as positioned about 1m from a wall and you are between the tractor and the wall. Your feet are up on the wall and you are pushing the tractor back at 500N and it starts moving. Now, put a lever of unknown length on the hub and again position yourself against the wall. How hard do you think you have to push on the lever to get the tractor moving? I'll give you a hint. The opposing force is 500N.

I suspect that you may be confusing torque and force. The force will vary inversely to the length of the lever although the torque will be the same for any given radius of wheel. In cycling terms, for any given speed, you have to push the pedals harder in a high gear than in a low gear.

I was hoping it wouldn't come to it but I can see I'm going to have to break out MS Paint to do a diagram.

 

[Seevio]

[QUOTE 4151027, member: 9609"]this was the answer I was looking for, seems obvious now but I wasn't getting my head round it earlier. But in my head it simplifies even further it if I think of what i would expect a motor delivering 500nm of torque, and of course i would expect it to be pushing at 500n at 1 metre out from centre. So clearly the opposite is bound to be true.[/QUOTE]
I hate to confuse things but this only works if the wheel has a radius of 1m. If the radius was 2m, a 500Nm motor would only be pushing 250N at the rim...

 

[classic33]

If it is a dream it's a very persistent one. (I think that was Einstein - but I might have dreamt that)

Reality is merely an illusion, although a very persistent one - Albert Einstein

 

[Profpointy]

I'm afraid it can't.

Kg is a measure of Mass. So if you're on Earth, Jupiter, wherever...a Kg is a Kg

But force varies dependent on where you are. The Force required to lift a Kg on Jupiter is not the same as on Earth. As it does to accelerate a body

pedant mode on...

a Kg is in fact a kg

 

[Piemaster]

I was hoping it wouldn't come to it but I can see I'm going to have to break out MS Paint to do a diagram.

I offer an online course in MS Paint. See my previous posts for the quality of work you can expect to achieve after only a few lessons. My rates are very reasonable.

 

[Piemaster]

[QUOTE 4151560, member: 9609"]I have never seen a hydraulic one, have used the multipliers but the ones I have seen are just for loosening.[/QUOTE]
You may be thinking of something a bit different from what I use, it isn't a wrench as such that rotates the nut, most of the nuts are actually round, no flats on them.
It's more of a stud stretching tool. Nut goes on hand tight then a circular jack goes over the top of it, pump up the jack, typically for my usual use 400-600 bar, tighten nut hand tight on the now stretched stud. Remove pressure + jack. With a cylinder head all are connected to the pump at same time so get same pressure and same tension on the stud.
Something like Enerpac. Theres an animation here 'bolt tightening' -the horizontal flange on the left.

 

[deptfordmarmoset]

Archie says “Give me a place to stand and with a lever I will move the whole world.” I say, '''Give me a place to stand and a big enough wheel and I will move the car for you.'' Science, innit?

 

[Seevio]

I offer an online course in MS Paint. See my previous posts for the quality of work you can expect to achieve after only a few lessons. My rates are very reasonable.

Ahh, you fall into the trap that many people do. You have made your Paint effort look good using shapes and stuff. For authentic results everything in Paint should be done freehand. Using a mouse.

Edit: The physics in the last pic was right though.

 

[Piemaster]

[QUOTE 4151601, member: 9609"]Great animation, the bolt tensioning tool was interesting. Presumably that gives a more accurate tension than a torque wrench, and a lot faster - I have noticed on some stuff, cylinder heads etc, they now give a torque figure, then you are told to turn the stud by a set amount of degrees (for instance 90 degrees) presumably that is also a more accurate way to achieve a set tension.[/QUOTE]
Exactly right with the 'torque plus an angle'. Bolt pitch x angle gives a length bolt is stretched, the material / length / cross section of a machined section controls the tension. That said it's not something I come across much any more since the use of hydraulics. A flogging spanner and a 75mm bolt wasn't much fun.
The hydraulic stuff is great but really does need instructions followed to avoid blowing jack seals. Also good as it does not actually apply any torque as such to the bolts, only stretches them so no shear forces on the bolt/threads as with a torque wrench.