Compound Gear-Trains

Schematic of Compound, three stage, Gear Train.

Schematic of Compound, Three-Stage, Gear Train

A 'Compound Gear Train' has at least:

•two Gear-Pairs
•one shaft with more than one gear

In MechDesigner, it is easier to add Compound Gear-Trains than Simple Gear-Trains.

 

The image to the left shows a Compound Gear Train. There is more than one gear-pair and two shafts have two gears.

Therefore, it agrees the definition of the Compound Gear Train.

See Also: Simple Gear-Pair, Simple Gear-Trains, Planetary Gear-Trains

 

Compound Gear Train – Gear-Pair 1

QST14-3-1

Start with a Gear-Pair with an External Mesh- see Option 1 Step 14.1

Here, the number-of-teeth are:

T1=201s-red, T2=402s. The Gear Ratio is T1/T2 = 2

Use the rule:

'Three Parts, with three Lines, joined together with two Pin-Joints'

Note 1: In this Tutorial, we sketch the Lines-of-Centre between the gears in the Base-Part.

Prepare Compound Gear-Train – Stage 2

QST14-3-2A

Again, we need three Lines, in separate Parts, with Pin-Joints that join the three Lines end-to-end.

Line 1 and Part 1 – see image.

The Input Shaft2s to the second Gear is the Output Shaft of the first Gear-Pair. It also has a Line along it.

Hence, we do not need to add anything for Line1/Part1/Joint1.

QST14-3-2

Line 2 and Part 2

'Line-of-centres'.

Because this Gear-Pair also has 'fixed-centres' , this Line must also be in the Base-Part.

1.Edit the Base-Part3s – Double-click it.

QST14-3-3

Note the Length of the Line-of-Centres for the first Gear-Pair = 120mm. Why?

Module = 4; Teeth are 20 and 40; Centre Distance = 4*((20+40)/2) = 120mm.
2.Add a Line1s-red.
3.Add a dimension to the Line
4.Use Merge-Points to merge the Point2s (the Point at the end of the Line-of-Centres for the first Gear Pair), and Point3s at the end of the new Line1s-red
5.Close the Part-Editor

QST14-3-4
6.Add a Part4s , with a Pin0Joint at the end of the new Line. The length of the Part is not important.

 

Add Compound Gear Train – Stage 2

CM-AddGearPair-clear-tags
(Element 4 is the Dimension of Line 3)

(Element 4 is the Dimension of Line 3)

 

Preparation of Model to add the Third Gear-Pair.

1.Add Gear-Pair
2.Click the four elements

QST14-3-7

You can see the new Gear-Pair.

 

The module is different. Usually, Gears have the same module throughout a Compound Gear Train.

QST14-3-8

Use the Gear-Pair dialog-box to edit

1.The Module to 4
2.The number-of-teeth on Gear 1 to be 30
3.The number-of-teeth on Gear  2 to be 50

The image shows the Two Gear-Pairs

•Gear-Pair1s-red in Blue
•Gear-Pair2s in Red

Prepare and Add Compound Gear Train – Stage 3

QST14-3-9

Preparation – the same as Stage 2.

1.The New Line in the Base-Part ...
2.... with the end Point in the Line merged to the Point at the centre Gear 2 in the Second Stage
3.A New Part Joined to the end of the new Line.

As before, we will use the Part that has Gear 2 of Stage 2, as the Part for Gear 1 of the Stage 3.

QST14-3-10

You can see the Gear-Pair Stage 3 – in red.

 

The module is different. Usually, Gears have the same module throughout a Compound Gear Train.

QST14-3-11

Use the Gear-Pair dialog-box to edit:

1.The Module to 4
2.The number-of-teeth on Gear 1 to be 22
3.The number-of-teeth on Gear  2 to be 52

The image shows the complete Compound Gear Train.

QST14-3-12

Frequently, the centre of the Gears in Compound Gears are in line:

1.Edit the Base-Part – double-click it
2.Use Add Horizontal to the Lines for each 'Line-of-centre'.

Important: Merge the Points at the ends of each Line.

QST14-3-13

Here is the third stage of the Compound Gear Train.

QST14-3-14

To make the Gears 'Solid':

1.Use the Home key to make sure the model is at the home position - this is important.
2.Click Solids Toolbar : Add Polyline
3.Click a Gear in one of the Gear-Pairs
To see the Polyline as a copy of the Gears, click the Gear-Pair to see the Gear-Pair and Polyline elements in the Selection-Window.
4.Repeat 2 and 3 for each Gear-Pair
5.Click Add Profile
6.Click the Gear-Pair with a Polyline
7.Repeat 5 and 6 for each Gear
8.Edit each Profile, to offset it etc, to give a model similar to the image to the left.
9.Edit the Parts to add shafts etc.

Tutorial and Reference Help Files for MechDesigner and MotionDesigner 13.2 + © Machine, Mechanism, Motion and Cam Design Software by PSMotion Ltd