Help needed for gear connection 1

[Ramone1]

I am able to create a gear connection but I am trying to create a connection between two gears with variable diameters.

I have tried using a cam connection but cannot achieve this, I would like to see the reaction between two gears where the ratio between them varies as they turn through a whole turn.

Could someone tell me if this is possible in Mechanism or if there is another way to model this.

Many Thanks

 

[cadcamguy]

Ramone,

Not sure if you can achieve that with a gear connection.

I'm thinking tieing two different servo motors together that both use table driven magnitudes

you will need to create .tab files which is a plain text file , first column being time and second being magnitude.

then read in table under your servo's profile > magnitude.

it will be as good as your math , anyway

perhaps you may be able to use a user defined magnitude, haven't tried it but "t" shows up which may give you the 0 to 1 expression.

 

[cadcamguy]

I use the table to stage my motor, but after digging around found this and it may be the way you want to go

Magnitude as a User-Defined Function
User Defined generates the magnitude of a servo motor, force motor, or force/torque with a function you create using sets of expressions and domain constraints.

For servo motors, you must define magnitude as a function of analysis time.

For force motors and forces/torques, you can define magnitude as a function of time, or as a function of multiple variables that may include time and one or more existing measures. For example, to define a force that decreases directly as the inverse of the separation between two points, first create a distance separation measure named septn1. Then define the force magnitude with the expression 1/septn1.

When you select User Defined as an option for the magnitude definition of a servo motor, force motor, or force/torque, the corresponding dialog box expands displaying the following buttons and fields:

Click to add a new row to the table. The table has a two-column format:

Expression—When you add a new row, this column contains a default expression, representing either time or, if applicable, a measure. You can edit the default expression directly in the table cell.

Domain—When you add a new row, this column contains no values for the expression domain. You can specify the domain values directly in the cell. For example, to enter a range of time between 1 and 10, enter 1 < t < 10.

Be aware that you must define each domain segment in the expression using only the primary variable.

Click if you need to delete selected rows from the expression table.

Click to edit the selected expression or domain. The Expression Definition dialog box appears. Use the dialog box to enter a new algebraic expression and domain. After you enter the new values, Mechanism Design places them in the expression table on the Servo Motor Definition, Force Motor Definition, or Force/Torque Definition dialog box.

Primary Variable—Use the drop-down list to select time or a predefined measure. The selected variable appears in the formula in the Expression column here and in the Expression Definition dialog box. This field is available only on the Force Motor Definition and Force/Torque Definition dialog boxes.

For Mechanism Design to provide a two-dimensional plot of your expression, you must select one variable as a primary variable. Mechanism Design uses the primary variable for the X axis when it graphs your expression, and requires you to supply constant values for the other variables—the secondary variables—in the expression. In addition, you must use the primary variable to specify all domain segments in the expression.

Unit Conversion Factor—This uneditable field becomes visible only when you initially defined the user-defined function in a unit system different from the current one. The field lists the variables included in the expression and the magnitude of the expression and displays the multiplication factors that Mechanism Design uses to convert the numerical values to the current unit system.

hth

 

[Ramone1]

Thank you very much for your help, I have had a play around and think I'm on the right tracks.

I've tried to enter a distance separation measurement between points at the centre of the two gears using Anaylsis -> Measures which I think has worked.

Using a Servo Motor with the driven entity as a Motion Axis and selected as the pin connection.

I've then chosen Velocity as the Specification. Under the magnitude I've selected User defined tab.

I now need to define my ratio in terms of the separation between the gear centres, as a default the "Expression" is set to t. Can anyone tell me how to change this to the separation measurement I've set up and how I fill in the "Domain" to vary the velocity of rotation with respect to the separation.

This will be a great help, Thanks

Ramone

 

[cadcamguy]

Ramone,

here are some links from the knowledge base that should help

http://www.ptc.com/cs/cs_25/howto/apm11083/apm11083.html

http://www.ptc.com/cs/cs_25/howto/apm10804/apm10804.htm

http://www.ptc.com/cs/cs_25/howto/apm10805/apm10805.htm

I think you can get to the second ones from the first

I tend to use tables and visual basic.

there may be a function there that might fit your needs.

If only info about proe was as popular as dirt on brittney spears.

 

[Ramone1]

True!

I cannot access these links because my account won't let me, I've e-mailed the PTC support. Is there any way you could send these to me in the mean time.

I've set up a hotmail account for this, if you could do it I'd be very greatful.

proestuff@hotmail.co.uk

Thanks Very Much

 

[cadcamguy]

Ramone,

Not sure if I am allowed to send you the files as they claim copyright.

Any one know the rules ? Is this a ptc no-no? Forum no-no?

In fact the files do not go into much detail from what i have seen about the user defined magnitude other than what i posted earlier, but I willing to bet that you may be able to use on of the off the shelf functions.

I tend to go with tables and vb.

You it's one of the things you have to like about proe.

You have this function with little or no info about it, but it feels good just knowing that you have it

Hopefully someone can join in and shed some light

 

[Ramone1]

Thanks for your help CCG, I'm still having a bit of trouble, I think inserting the data in a table would suit me perfectly but I notice that the variable in the table is set to default "time".

Do I have to give values of rotational velocity relative to time or can I change this to be relative to the separation of the centres.... or is this why I need to choose the user defined function?

Thanks Again