Strider Ver 3's Frame

Frame triangles are critical for making strong frames for walkers, but LEGO's integer-based beam lengths can make it difficult to find diagonal beams of the correct length. You can find other ideas for creating triangle-based frames with LEGO beams in this blog post.

This frame build assumes that each side of the robot will have its own motor for steering, using either the battery box and IR sensors, or the EV3 components. If instead you want to build Strider Ver 3 without steering and only one motor, then you can still build most of this frame, except for the gear train and motor mounts. For ideas on how to add only one motor to Strider Ver 3's frame, see Strider Ver 2's instructions.

Below is a battery box version:

And below is a Mindstorms version, which would be much smoother if built in a 12 leg version. Also, you could try mounting the EV3 brick on top for more clearance (but it would be less stable)

Below is a 12 leg build using the same Strider linkage. If you use medium motors for the 12 leg build then the only differences from the 8-leg version are:

1. use the shorter toes shown in the leg's instructions
2. change the four inner cranks to 120 degrees, as shown at the bottom of the leg's instructions (which require longer axles for the legs)
3. cut longer, 20 inch metal rods

Strider Ver 3

Strider Ver 3 using medium motors

You can find some detailed images of mounting an XL motor at the end of these instructions.

Each side of Strider's frame is the same.

Build 2 of the following frame sides.

Below are the frame Parts for one side, which we purchased on Bricklink.com

Also, the two metal support rods have a 3/16" OD. We've used both brass tubes and aluminum rods, depending on what our local hardware store had in stock. We cut the rods to 15" for 8-legged Striders, and to 20" for 12-legged Striders.

Let's begin:

Next, flip the frame over:

then, turn the frame around and add a red bushing to the other side:

Again, this part is for mounting the battery box, not for mounting the EV3 brick.

Make a second frame side, then join them with the below 3/16" OD metal rods

Rotate the rods to make them easier to slide thru the parts.

This lower beam is for mounting the battery pack, and is not necessary for mounting the EV3 brick

cranks attach as shown below.

Battery Box mounting (EV3 further down)

Be sure to add outer frames, like below, so that the outside axle connects to the leg's Center of Rotation. The diagonals are beams with 11 holes, connected to the 6th hole of the top beam.

EV3 Mounting:

Be sure to add outer frames, like below, so that the outside axle connects to the leg's Center of Rotation. The diagonals are beams with 11 holes, connected to the 6th hole of the top beam.

12 Leg Strider
Below are some images of a 12 leg Strider. Four more diagonals were added to the outside of the frame to strengthen it a bit more for its load bearing test, but adding them is just an option. Also, the version in these images used an XL motor geared up by 1:1, which works well on surfaces with friction, like on carpeting, but its feet are too fast for smooth surfaces like wood or tile floors.

Note: 12 leg Striders run well with the medium motors geared down by 5:1 (like 8 leg Striders), which do not require a longer beam for the gear train as built below.

Be sure to add outer frames, like below, so that the outer axle connects to the leg's Center of Rotation. The diagonals are beams with 11 holes, connected to the 6th hole of the top beam.

Below are videos of 3 different speed options for the XL motor: slow using an 8 tooth gear, medium using a 24 tooth gear, and fast using a 40 tooth gear.

Slow (8 tooth gear):

24 tooth gear:

40 tooth gear - this version's feet are too fast for smooth floors (like wood or tile):

XL Motor Mounting
If you want to use XL motors, then you'll need to extend the length of the beams supporting the gear train. The outer beam will need to be switched from 13 to 15, and the inner beam can be extended with the assemblage of parts shown further down.

Below shows how the XL motor was mounted for the 40 tooth gear, but it can be mounted many different ways

1. add the gear to the 15L beam:

2. Add a 5 hole beam to the metal support rod, which is easiest to add when first sliding the metal rods thru the frame!

3. Put 4 pins into the XL motor, and then assemble the below parts as shown in the following images

Then attach the motor