Mounting wheels to Zheng DC motor and Mounting free wheels

[Jenn]

Dear Robotshop technical experts,

This is my first time building anything... so I'm sorry for the excessive questions!

I am currently building a robot for a design project in university. I am currently using a Zheng DC gearbox motor (12V, 50RPM), and I would like to mount RB-Ban-94 (Banebot 2-7/8") wheels on them using a suitable hex hub.

The problem is that the shaft on my motor is about 4mm in diameter and round except for one slightly flat side (looks somewhat like a D in shape) and only about 1.1 cm in length, so I am afraid that the hex hub will not fit onto the motor shaft.

Do you have any products/advice that would help?

Also, I would like to mount to non-driven wheels to a 4mm diameter round shaft and secure them in place, as well as securing the shaft to the chassis of my robot.

Do you know how I could accomplish this?


Thank you so much for your help!
Jenn

[Cbenson]

Don't purchase RB-Ban-94! Instead purchase RB-Ban-104 (1/5" hex mount, 0.8" wide) with RB-Ban-156 (1/2" hex mount, 2 x 0.4" = 0.8" wide with 4mm bore - select the options). Since there are two set screws on the hub (instead of one at the center), you will be able to properly tighten at least one set screw against the flat part of the motor's shaft.

For the non-driven wheel of the same type (if in fact you want the same type) you can purchase the same parts above and simply not use the set screw - the wheel will spin freely. To keep the wheel from sliding left and right on the shaft, you will need two shaft locks (shaft collars) with 4mm bore. RobotShop does not offer these particular collars at this time, but you can try an internet search (smallparts.com for example). You can use the shaft locks to secure the shafts in place on your robot, or even set screw hubs, or bearing blocks with shaft locks... the choice is yours based on complexity and budget.

[Jenn]

Thanks for the help!

To build on your answer, I'm afraid that the two wheel wide hubs will be too big... but since 0.4" is approx. 1cm, it should work on my motor, right?

Also, would it work to use a bushing instead of a hex hub?

Thanks,
Jenn

[Cbenson]

... since 0.4" is approx. 1cm, it should work on my motor, right?

In theory it should work well, but you may want to choose a thinner wheel and hub combo such as RB-Ban-152 (4mm inside diameter and 0.4" wide, 1/2" hex) and RB-Ban-92 (0.4" width, 1/2" hex insert).

Also, would it work to use a bushing instead of a hex hub?

For the idler wheel, you'd need to press fit the correct sized bushing into the wheel. The easier option is to use the correct hub which is guaranteed to work.