Need help with mates and gear relation please

tarek_mustafa

Hallo All, I learned a bit about gear design and created 2 gears with a gear ration of 2.5. I would like to do a visual test to see if I got the drawing based of my calculation right but I can't get the mates to work.

Please can someone help me to assign mates to the gears so I see them spin? A short step by step instructions would also be vert much appreciated!
I have made the document public.

Thank you!

jakeramsley

I have two "gears", one has a diameter of 25" and the other has a diameter of 10".  The distance between the centers is going to be (25" + 10") /2 = 17.5".

1. Go to assembly and insert one of the gears (I prefer to have the bigger gear in the center/about the origin).


2. Make a revolute mate and select the center of rotation on the first "gear"


3. Hover over the origin and select one of the mate connectors from the origin.  I chose the one that has the normal in the z-direction.  This allows the first "gear" to rotate about the origin.


4. Create an explicit mate connector that overlaps the one that was the origin.  We will be moving this 17.5" to give the center of rotation of the second "gear"


5. Select "Move" checkbox and move the mate connector in either the x or y axis 17.5".  I chose the x axis


6. Insert the second "gear" and start a second revolute mate.  Select the center of rotation for the "gear"


7. Select the explicit mate connector.  This allows the second "gear" to rotate about that point (which is essentially tangent to the first "gear")

8. Add a gear mate relation between revolute 1 and revolute 2.  Set the ratio to be 2.5.  Once accepted, start spinning and see if the ratio needs to be flipped

andrew_troup

All that remains to do in jake's model is to position the smaller gear, using a revolute mate to his offset connector, then create a gear relation between the two revolute mates.

I think Jake's model strikes a nice balance, by establishing the tricky precept (repositioning the offset mate connector), but leaving enough to the end user that the model has to be thoroughly explored and understood, making the process memorable. Seems to me a great sampler of some excellent teaching skills, @jakeramsley

Another thing about this thread: it shows how easy and fun it is to help others climb the learning curve with Onshape, in comparison with other packages. Mainly this is due to the ease of sharing models.
It's also greatly assisted by the inherent nature of history-based (as opposed to purist direct edit) modelling: the model itself contains its own explicit recipe.

So there seems to me a reasonably strong chance, once a substantial feature-set is in place, that Onshape (easy/fun/free/self explanatory) could go viral. 

nav

Hi @tarek_mustafa have you tried following this tutorial :https://cad.onshape.com/help/#materelation-gear.htm?Highlight=gear ;

tarek_mustafa

Hi @nav , thanks for your reply. Yes I looked into the tutorial but unfortunately this didn't help me. If possible I don't like to model a support structure I just want to connect the two gears and see if they rotate correctly.

david_sohlstrom

You need a hole in the center of each gear. Then you need a third part with 2 holes in it at the correct center distance for the gear pitch. Once you have that you mate 1 gear to each of the holes with a rotating mate. Next you go to the gear relation tool and choose the gear type. In your case spur gears. In the tool you set the gear ration and then you have it. This all has to be done in an assembly of course.
If the gear teeth do not match up then you go in and rotate one of the mates so the gears mesh correctly.
once all of this is done you can grab one of the gears and rotate it and the other gear will rotate at the correct ration. If you put a small hole out close to the teeth of each gear it makes it easier to see if your ratio is correct.

Hope this helps

Dave 

jakeramsley

Make revolute mates with respect to the origin.  Make two explicit mate connectors, one that is at the origin and one that is offset in one direction by (D1 + D2) / 2.  From here, make the revolutes with respect to those mate connectors.  Put the two revolutes in a gear mate with a ratio of 2.5 and start spinning them.

For example:
https://cad.onshape.com/documents/53bddf1068004057bd194191/w/7b9f3a41b660461c881d3b32/e/2c97adf316ce4ad2a88e6c01

tarek_mustafa

Hi @jakeramsley that is a Solution I was looking for but unfortunately I can not make it work using your description and example. I keep looking into this to figure it out. Thank you!

tarek_mustafa

Hi @david_sohlstrom thank you for your Solution. I am looking for something that @jakeramsley described and try now to make it work. Thank you!

jakeramsley

I have two "gears", one has a diameter of 25" and the other has a diameter of 10".  The distance between the centers is going to be (25" + 10") /2 = 17.5".

1. Go to assembly and insert one of the gears (I prefer to have the bigger gear in the center/about the origin).


2. Make a revolute mate and select the center of rotation on the first "gear"


3. Hover over the origin and select one of the mate connectors from the origin.  I chose the one that has the normal in the z-direction.  This allows the first "gear" to rotate about the origin.


4. Create an explicit mate connector that overlaps the one that was the origin.  We will be moving this 17.5" to give the center of rotation of the second "gear"


5. Select "Move" checkbox and move the mate connector in either the x or y axis 17.5".  I chose the x axis


6. Insert the second "gear" and start a second revolute mate.  Select the center of rotation for the "gear"


7. Select the explicit mate connector.  This allows the second "gear" to rotate about that point (which is essentially tangent to the first "gear")

8. Add a gear mate relation between revolute 1 and revolute 2.  Set the ratio to be 2.5.  Once accepted, start spinning and see if the ratio needs to be flipped

andrew_troup

All that remains to do in jake's model is to position the smaller gear, using a revolute mate to his offset connector, then create a gear relation between the two revolute mates.

I think Jake's model strikes a nice balance, by establishing the tricky precept (repositioning the offset mate connector), but leaving enough to the end user that the model has to be thoroughly explored and understood, making the process memorable. Seems to me a great sampler of some excellent teaching skills, @jakeramsley

Another thing about this thread: it shows how easy and fun it is to help others climb the learning curve with Onshape, in comparison with other packages. Mainly this is due to the ease of sharing models.
It's also greatly assisted by the inherent nature of history-based (as opposed to purist direct edit) modelling: the model itself contains its own explicit recipe.

So there seems to me a reasonably strong chance, once a substantial feature-set is in place, that Onshape (easy/fun/free/self explanatory) could go viral. 

tarek_mustafa

Excellent thank you all!