Mechanical Movements

~(5,5)

(This would be a very wear-prone mechanism.)

The third sentence of the description holds your answer.

Place the two shafts in any relative positions that allow roller A to travel inside the heart shaped guide.

I'm trying to visualize the suggested position as follows:

With this arrangement, do you think the rotation of wheel 217 could cause the indicated movement of wheel 218? This means: for a rotation of C to D of 217 (the driver) should cause a 1/3 rotation of the wheel 218 (the driven) and rotation of D to e, via B should cause the driven a 2/3 rotation, I'm not convinced.

2 shafts ARE concentric, great thinking, good answer:

I will plot this on 3D and confirm.

You will note that your revised drawing has shortened the A lever. Also note that in the original drawing the 217 is larger in diameter than the 218. These are important points. the A lever must be long enough to have the A roller in the groove at its farthest deviation from centre.

Look at the drawings again and read the description carefully.

It will make your simulation work correctly.

What is not immediately obvious at all is how the catch and lever of G is going to pivot and what centre it has. Thats conveniently left out of the description, only hinted at.

Yes, I've shortened the A lever. I will undo that and sake of better understanding, let us consider wheel 217 and the lever only. Now the lever is long enough to have A roller in the grove at its farthest deviation as in first fig below.

Now, let us rotate wheel 217, say for 15⁰ as in second fig. Wouldn't the roller/lever tent to rotate with wheel 217 for the same degree? If yes, it would do for rest of the full rotation as well. What would compel the lever to rotate to a different angle, the load?

I observe that either pivot H or G must move or the linkage would be triangulated and incapable of movement.

Tony

With you on that.

That word description was hard to read and had me struggling to understand it. Worked up sweat and everything. I only read it once and that was enough for me.

It really needs another thousand words to describe how it works.....or a picture.

"That word description was hard to read"

If you are referring the word image in my first post, please refer the following text...

217 and 218. These are parts of the same movement, which has been used for giving the roller motion in wool-combing machines. The roller to which wheel, F (218), is secured is required to make one third a revolution backward, then two thirds of a revolution forward, when it must stop until another length of combed fiber is ready for delivery. This is accomplished by the grooved heart-cam, C, D, B, e (217), the stud, A, working in the said groove; from C to D it moves the roller backward, and from D to e it moves it forward, the motion being transmitted through the catch, G, to the notch-wheel, F, on the roller-shaft, H. When the stud, A, arrives at the point, e, in the cam, a projection at the back of the wheel which carries the cam strikes the projecting piece on the catch, G, and raises it out of the notch in the wheel, F, so that, while the stud is traveling in the cam from e to C, the catch is passing over the plain surface between the two notches in the wheel, F, without imparting any motion; but when stud, A, arrives at the part, C, the catch has dropped in another notch, and is again ready to move wheel, F, and roller as required.

Well yes, that was actually easier to read but not any easier to stay interested in long enough to get the full picture.. err.. next thousand words.

Not getting the full picture is my basic problem as well and that's the challenge

I think it should be center of 218 on 0,10 ( = A,H ) and the center of 217 on 2.5,0.

Jim

P.s. keeping it short to beat time out.

PPS didn't work

As indicated in my post:8 as the reply for post:6, I'm not inclined to the suggestion of wheels being concentric.

Having back to the suggestion of post:1, I'm trying keep things in 3D space for study. Following are five sequential snaps of the animation for one full revolution of 217 wheel. I'm yet to come up with cam shape that lifts/drops the second lever.

I can only think that for every rotation of wheel:217, wheel:218 can move for one tooth only. Well, we can design to move for 2/3 teeth in one go, but how 2/3^rd (which means an arc of 240⁰) of a revolution?

I like the pics ( wish I could do that ). May I suggest putting blue wheel in front of the lever with tracks on the back. It can then be made big enough to have pin knock the disengage pin on the top lever arm. I also believe it will work better if you move its center to the other side of point 'A'. i.e. move it to the right of the lever and a bit higher.

Jim

I agree your points Jim, when coming to the operation of second lever. My basic doubt lingers around the original statement in the 'Manual of Mechanical Movements' by Mr. Henry T. Brown, "the roller to which wheel, F (218), is secured is required to make one third a revolution backward, then two thirds of a revolution forward."

Thanks for the reply. Yes the forward and backward motion I see as being the same amplitude because the tracks in the back of the wheel are identical. However the wheel 217 has a pad which lifts the top lever bar at point 'G' taking the drive dog out of the groove and dropping it onto the land between grooves thereby denying it the opportunity to move the roller until it falls into the next groove.

Jim

Yes Jim, lifting and dropping has to be achieved by a cam or another lever. Still my basic doubt is, 'having dogged into the grove, the lever has to rotate several degrees to make 1/3 and 2/3 rotation of wheel 218.

In following figures, there are three functional points:

From point: 1, the lever has to describe 120⁰, clockwise until reaching pint: 2. This justifies the statement," The roller to which wheel, F (218), is secured is required to make one third a revolution backward."

From point: 2, still the lever dogged in, should start to rotate 240⁰ counter clockwise till point: 3. This justifies the statement, "then two thirds of a revolution forward"

At point: 3, the lever should be lifted up and continue to rotate counter clockwise, till reaching Pint: 1, wherein the lever has to get dropped into a grove of wheel: 218. This justifies the statement, "it must stop until another length of combed fiber is ready for delivery."

Summarizing the above, the lever has to cover 360⁰, but the heart wheel: 217 can impart only an arc-wise movement to the lever. I'm tangled in this mismatch.

As I read it, the start of the cycle is when the latch at point A has already been lifted and the heart wheel has done 1/3 of a turn. It then drops in and does the other 1/3 reaching the point e and sending the laver back 2/3 of a turn. As you correctly said this is an oscillating ( arc-wise ) motion and not a complete rotation.

Jim