Simple Gear-Trains

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Simple Gear-Trains

Simple Gear Trains

Schematic of Simple Gear Train

Schematic of Simple Gear Train

A Simple Gear Train is a number of Simple Gear-Pairs in series. Each shaft/axis has only one gear. Use a Simple Gear Train:

To increase the distance between the input and output shafts and still use small gears

To reverse the direction of the output shaft on a Simple Gear-Pair

To increase or decrease the Torque and Speed at the output-shaft.

The image to the left shows a schematic of a Simple Gear Train.


1.Only the gears on the input and output shafts change the speed ratio. All other change the rotational direction.

2.The gears not on the input and output shafts are called idle gears or idlers.


Monobloc Machines

Monobloc machines are frequently used with Filling, Capping, Labeling, Coding, Orientating and many other high speed packaging applications.

The monobloc has a simple gear-train to transmit the motion from one 'head' to the next.

See  YouTube Video:


Gear-Pair 1


Do Add a Gear-Pair with Fixed-centers

Edit the number-of-teeth as follows.

Here, the number-of-teeth are:

Z1=20Red-14-2, Z2=40Red-14-3.  

The Gear Ratio is Z1/Z2 = 2

Remember this basic rule:

Three Parts, three Lines, joined together with Pin-Joints. Two Lines must be in Parts that are kinematically-defined.



To add a Simple Gear-Train, we use the same basic rule, again, and again.

We need three Parts each with a Line, a Line is joined with a Pin-Joint to the Start-Point and the end-Point of one Line.

Gear-Pair 2:

Before we start, we have a Line in a kinematically-defined Part.

Line 1 / Part 1 : LineRed-14-5 is the CAD-Line in the Driven-Gear of Gear-Pair 1.

We need two more Parts and Lines.

Line 2 / Part 2 : It is a new Line in the Base-Part. It will be the Line that joins the gear-centers

1.Edit the Base-Part

2.Part-Editor: Geometry toolbar > Add LineRed-14-1b AND Add DimensionRed-14-2  (the actual length is not important).

IMPORTANT rule: You must MERGE PointRed-14-3 and PointRed-14-4

You can Hover + Drag to add LineRed-14-1b  from PointRed-14-3 OR

3.Part-Editor: Geometry toolbar > Merge-Points : Click PointRed-14-3 and then click PointRed-14-4

4.Click the graphic-area to complete the merge-points.

5.Close the Part-Editor



Line 3 and Part 3 : It is a new Part - it will be the Driven-Gear.

1.Mechanism-Editor: Kinematics-toolbar > Add Part: Drag to the PartRed-14-6

2.Mechanism-Editor : Kinematics-toolbar > Add Pin-Joint  Join the start-Point of CAD-Line in PartRed-14-6 to the end of LineRed-14-1b, with a Pin-Joint.

The length the CAD-LineRed-14-7 along PartRed-14-6 is not important.


We are ready to Add Gear-Pair

Gear-Pair 2 : ADD GEAR-PAIR


1.Click Machine-elements toolbar > Add Gear-Pair

2.Click the elements, Red-14-5Red-14-7Red-14-1bRed-14-2 from top to bottom - refer to Preparation images, above

3.Click OK-tiny-11-15  at the bottom of the Command-Manager.


You can see the Gear-Pair 2Red-14-2


MechDesigner adds two new gears.

A Simple Gear Train does not need one of the Gears of Gear-Pair 2.

We must hide the Gear on the same shaft center.

This is a MechDesigner trick.


Use the Gear-Pair dialog-box to edit:

1.Module = 3

2.Number-of-teeth Gear 1 = 40 : the same as Gear 2 of Gear-Pair 1

3.Number-of-teeth Gear 2 = 20

The image shows the Gear-PairRed-14-1b and Gear-Pair

You can see only 3 gears.

Gear 2 of Gear-PairRed-14-1b is hidden by Gear 1 of Gear-PairRed-14-2

You can do the same actions to add more Gear-Pairs.