1C: Practice Mechanisms

Exercise 4: Telescoping Hook

In this exercise, you will be modeling a telescoping climber. This mechanism features WCP GreyT telescoping bearing blocks and REV MAXPlanetary mounting gearbox plates. Be sure to pay close attention to hook and gearbox sketches when modeling.

Leveraging COTS Components

Using COTS components is crucial in a time-constrained build season. Even if you have the capability to fabricate every part, relying on COTS parts allows you to spend your time on more important tasks—like refining designs or testing. This helps ensure your time is spent where it makes the most impact, rather than on re-inventing parts that are already readily available.

Exercise 4 COTS Components

The telescoping bearing blocks have complex geometry that would be difficult and time consuming to manufacture for most teams. The REV MAXPlanetary is an easy way to get a large gearbox reduction without the need for a custom gearbox. (Photo Credits: WCP, REV)

Part Studio Instructions

Navigate to the "Exercise #4 Part Studio" tab in your copied document and follow the instructions in the slides to complete the part studio for this exercise.

1. Begin by creating a side profile sketch of the telescope tubes on the right plane.

2. Use two extrudes to create the solid bodies for the tubes. Then, use the Tube Converter Featurescript to convert the solid bodies into two thin-wall tubes with no hole pattern.

3. Add the holes for the WCP bearing blocks to the inner and outer tubes. The dimensions are from WCP's documentation.

4. Model the crush block at the top of the inner tube. You will add the holes that go through the crush block after you model the hook.

5. Sketch the hook. Pay attention to the sketch relations in the solution document.

6. Extrude the hook. Then, extrude the mounting holes to cut through the tube and the crush block. Also add the hook spacer.

7. Model the hook 3d printed spacer. With sketch imprinting enabled, we only need to draw the line for where the 3d printed block starts. There is no need to use the Use feature to copy the hook profile into the sketch.

8. Sketch the gearbox mounting plate on the outside of the tube. There should be a small 0.01" gap between the 3/8" clamping spacers and the tube to make sure that the gearbox can be assembled properly. The 13.75 mm construction circle represents the rounded hex spool. The #10-32 tapped hole allows for a bolt to thread into the plate and sit flush with the inside of the outer tube to lock the gearbox in place without interfering with the inner tube.

9. Sketch the pull down string by creating a line tangent to the rounded hex spool. Note that we will use this line to create a sweep of the rope, therefore this line cannot be construction geometry.

10. Extrude the plate, then add half depth pockets. The pockets should leave 1/16" of material on the bottom. The half-depth pocketing allows the contact face between the gearbox plate and tube to be solid. The plate should be mirrored to generate the opposite hand version on the other side of the tube.

11. Add a 10-32 clearance hole for the bolt that is threaded into the gearbox plate. Also model the gearbox spacer and the shaft.

12. Model the rope by creating an 3 mm circle on the end of the vertical line from the gearbox. Then, sweep the circle along the vertical line from the gearbox to create a model of the rope.

13. Finish the part studio by naming your features and putting them into folders. Also assign materials according to the reference design.

Assembly Instructions

Next, navigate to the "Exercise #4 Assembly" tab in your copied document and follow the instructions in the slides to complete this exercise.

1. Insert the climber components and group only the base stage components together to the Origin Cube. This is because the inner stage moves relative to the base stage, so we cannot group them together.

2. Fasten the inner stage components together.

3. Insert and fasten the WCP GreyT telescope bearing blocks from the WCP GreyT telescope document.

4. Use two Slider mates to constrain the inner stage. By using two slider mates, one for the bottom and one for the top, the inner stage motion constraint is parametric to length changes in the base stage. We do not need to explicitly specify a travel length.

5. Fasten the spacer and replicate it. Insert and fasten the shaft bearing to the plate and shaft. Note that we only require one bearing on the plate since the MAXPlanetary gearbox has another bearing at its output as we do not want to overconstrain the shaft.

6. Insert and fasten the MAXPlanetary gearbox from MKCad. We use the 90 degree output with a 25:1 gear ratio.

7. Insert, fasten, and replicate all of the required fasteners.

8. Close up of the bolt used to pin the gearbox in place. This bolt keeps the gearbox from sliding up and down.

9. Finish your assembly by organizing the parts into folders and naming your replicates.

Verification

Make sure to have you and/or a more experienced member/mentor of your team review your CAD! Your assembly should have 27 instances.

Section Views

Section views are a helpful tool that allow you to reveal the internal features of a part or assembly by slicing through it along a specified plane. You can select a plane, planar face, cylinder, cone, or mate connector to use as the sectioning plane. You can also choose to include or exclude specific parts from the section view.

Creating a Section View

Creating a section view to get a better view of the pinning bolt.