dimensioning

[Jeffcott]

Hi, I'm finding it difficult to make the size of a tree, so I was wondering if anyone could give me all the delucidations about it and clarify all the steps to follow for a proper size of the trees. I attach the schema and list all the data in my possession.
- engine power 400 watt (motor positioned at point 1)
- torque moment of 23 nm
- rotation shaft 46.67 rpm
- pulley diameter 93.65 mm (even diameter pulleys and positioned at points 2 and 3)
- weight of each pulley 1,14 kg
- bearings are positioned at points a and b

 

[MBT]

We turn the problem, otherwise we are at the usual ("do you that I then put in beautiful". . . )
You tell us how you'd solve it, then see where the mistake is!

 

[Jeffcott]

I'm sure I wouldn't put it in good shape. rather I would have a procedure to follow when I have to resize a tree. returning to the problem, the first difficulty lies in the schematization of forces. I have no driving wheel but the engine (1) rotates the shaft directly. how do I shcematize the forces to make the balance?

 

[gerod]

How do you size the tree?
torque moment
at the moment
cutting (usually cutting is negligible, but not always)

then fatigued, and here is to know how forces are, how they vary, etc.

there are formulas for fast calculation (see manual of mechanical engineering) and other much more full-bodied.
the thing is quite simple and solves with the theory of construction science going to check the state of tension in the most stressed section.
I did not solve the problem but I gave you the method, also because the problem is not solved because there is no essential data!
diameter and material I would say that they are the sine here not!
then the maximum torque of the motor at the point!
Are there any joints between engine and tree?

 

[mcdue]

How do you size the tree?

diameter and material I would say that they are the sine here not!

I miss something probably, but the diameter is not exactly what he asks to calculate?
For the rest could I dare to be able to dimensional with the hypothesis of von mises or have I taken a bark? (of course you need at least the material you want to build)
If you tell me that I'm on the right path and that my memories have not betrayed me I can dare to make two accounts later...

 

[Fulvio Romano]

development better the method proposed by gerod, which is correct, but explanations are perhaps a little too tight.

I would do like this:

- I know the engine power
- I know the number of regime turns
- I find the maximum torque between the point and the regime (this given you take it from the characteristic of the gearmotor, do not make the trivial error to calculate at regime, then the alert and you burst into the face!)
- I calculate the wheels resistant moments 2 and 3, depending on the load applied, to the diameters etc... (if the diameters are not known, of course, work in symbolic! )
- on section 1 - 3 I will have a torque moment of m3, on section 2 - 3 I will have m2
- Let's see the forces. Tangential forces (which do not stress the shaft) in 2 and 3 are equal to the torque moment divided the radius of the wheel. to calculate the normal ones (which instead stress the tree), you have to calculate the component that, together with the tangential develops a resulting orthogonal to the face of the tooth intake. if they are straight teeth is easy, if they are helical teeth, consider the equivalent to straight teeth. It's the same thing, even if you have to do two accounts to prove it.
- you calculate a and b to balance forces and weights
- calculate the tension of von mises (combining twisting and stinging moment) and find the most stressed section.
You see, if you're under the fatigue limit, go to sleep on a soft pillow. but this is another story

 

[mcdue]

development better the method proposed by gerod, which is correct, but explanations are perhaps a little too tight.

I would do like this:

- I know the engine power
- I know the number of regime turns
- I find the maximum torque between the point and the regime (this given you take it from the characteristic of the gearmotor, do not make the trivial error to calculate at regime, then the alert and you burst into the face!)
- I calculate the wheels resistant moments 2 and 3, depending on the load applied, to the diameters etc... (if the diameters are not known, of course, work in symbolic! )
- on section 1 - 3 I will have a torque moment of m3, on section 2 - 3 I will have m2
- Let's see the forces. Tangential forces (which do not stress the shaft) in 2 and 3 are equal to the torque moment divided the radius of the wheel. to calculate the normal ones (which instead stress the tree), you have to calculate the component that, together with the tangential develops a resulting orthogonal to the face of the tooth intake. if they are straight teeth is easy, if they are helical teeth, consider the equivalent to straight teeth. It's the same thing, even if you have to do two accounts to prove it.
- you calculate a and b to balance forces and weights
- calculate the tension of von mises (combining twisting and stinging moment) and find the most stressed section.
You see, if you're under the fatigue limit, go to sleep on a soft pillow. but this is another story

perfect ok, I find myself now (regarding impolite notes) and reading how much you wrote to understand something. Thank you.

 

[sampom]

Hi, I'm finding it difficult to make the size of a tree, so I was wondering if anyone could give me all the delucidations about it and clarify all the steps to follow for a proper size of the trees. I attach the schema and list all the data in my possession.
- engine power 400 watt (motor positioned at point 1)
- torque moment of 23 nm
- rotation shaft 46.67 rpm
- pulley diameter 93.65 mm (even diameter pulleys and positioned at points 2 and 3)
- weight of each pulley 1,14 kg
- bearings are positioned at points a and b

development better the method proposed by gerod, which is correct, but explanations are perhaps a little too tight.

I would do like this:

- I know the engine power
- I know the number of regime turns
- I find the maximum torque between the point and the regime (this given you take it from the characteristic of the gearmotor, do not make the trivial error to calculate at regime, then the alert and you burst into the face!)
- I calculate the wheels resistant moments 2 and 3, depending on the load applied, to the diameters etc... (if the diameters are not known, of course, work in symbolic! )
- on section 1 - 3 I will have a torque moment of m3, on section 2 - 3 I will have m2
- Let's see the forces. Tangential forces (which do not stress the shaft) in 2 and 3 are equal to the torque moment divided the radius of the wheel. to calculate the normal ones (which instead stress the tree), you have to calculate the component that, together with the tangential develops a resulting orthogonal to the face of the tooth intake. if they are straight teeth is easy, if they are helical teeth, consider the equivalent to straight teeth. It's the same thing, even if you have to do two accounts to prove it.
- you calculate a and b to balance forces and weights
- calculate the tension of von mises (combining twisting and stinging moment) and find the most stressed section.
You see, if you're under the fatigue limit, go to sleep on a soft pillow. but this is another story

perfect:finger: (obviously, I say it to you

However, jeffcot, it seems to me that it is the same "exercise" (although another "paragraph") of your other thread regarding the transmission to dense straps (http://www.cad3d.it/forum1/showthread.php?t=20980 from the bottom of the first page).
we do not do as for the weighing tape with different open discussions; in the end there were questions and answers a little everywhere and putting together everything becomes a mess. try to uniform in a single "project".
I ask gerod (if it considers it useful and appropriate) to join in a single these two discussions.

the thing can be useful and interesting for many (a good resumption never hurts, even for what is now considered "discounted") and jeffcot gives us good ideas.

greetings and good work (good week end really.. and eye to witches)
Marco:smile:

 

[Jeffcott]

Forgive me sampom but I wanted to put a different thread from the other conversation even if they look very similar. thank you for the answers but I found nothing on the first question, concerning the schematization of forces. I repeat that I do not have any driving wheel as the shaft is stuck with an appropriate key to a gear motor. The first problem I have is therefore the schematization of forces and moments to be able to make balance. Could someone make it clear to me better, maybe with a pattern? precise that the torque moment I will have at point 1 while I have no toothed wheel but only two pulleys for a belt drive at points 2 and 3. straps transmit motion to further pulleys placed on the same tree. How do I achieve the balance of forces? I hope you can help me.