How To Reduce Unnecessary Friction

How can I reduce friction on my flywheel?

Make sure your bearings are aligned correctly. Also, you could use some sort of competition-legal lubricant. You could also check to make sure everything is mounted properly and check to see if any shafts are bent. Make sure you use spacers and washers where they are needed and that nothing is loose/about to fall apart.

I find that a common source of friction is when axles apply force to the metal which holds them. For example, putting in too many spacers or pushing collars up while screwing them in can create this force. So I always leave about a washer’s worth of slack on axles. While this does slightly affect stability, I’ve also seen that it significantly reduces friction. But if anyone knows how to reduce friction without adding slack I’d be very interested to know.

Oh and also, I always use silicon washers wherever metal on an axle might touch some other, stationary, piece of metal.

Every time I put an axle through a bearing it becomes stiff and does not spin smoothly.

Couple of possible reasons for that:

  • Shaft is bent
  • Shaft goes through multiple bearings that aren’t line up perfectly
  • Shaft doesn’t go through the bearing perfectly perpendicular to the bearing

A rule of thumb I try to encourage: to support a shaft, use only two bearings. Trying to get more than two bearings to line up perfectly and stay lined up perfectly is extremely difficult/unlikely. It’s okay if you double up bearings so they are cheek-to-cheek to serve as one bearing and then use a second bearing elsewhere, but don’t expect three or more bearings widely spaced apart to all stay lined up. And once 3 or more bearings are out of alignment, the friction goes WAY up.

Then how do teams have flywheels that don’t stop shooting and just fire?

Is there any vex legal lubricant for plastic gears?

Not exactly sure what the question is? The difference is build quality. I would suggest pretesting any bearings before putting them on the flywheel as well as testing each axle on your flywheel without any of the gears.

I just want to second this. I see this problem all of the time and it is usually the primary friction source.

For example, when you grab a gear on your flywheel shaft you SHOULD be able to wiggle it back and forth slightly. If you cannot wiggle it at all, you have to many spacers and are creating friction.

In my experience, the thing you really want to lubricate is not the gear itself but the shaft where it goes through the bearings. My team has had success using small amounts (about 1/4 of a pea-sized drop per bearing) of white lithium grease (available online or from your local hardware store) to lubricate the bearings. We apply the grease using one of our several dozen 11/64" vex screwdrivers. When doing this, just remember to be mindful of rule <R7e>:

We’ve found that careful application of grease and making sure all shafts are very straight have reduced the friction on our flywheels considerably.

Our High school teams flywheel can shoot all 24 balls in 17 seconds. They told me to use normal gears instead of high strength gears. They also said to use grease for the gears. Our robots are exactly alike except for the drive.

That I know of. Would using normal gears help?

they probably wont help much, but its completely unnecessary to use high strength gears for things that are super low torque

Okay I’ll take that into consideration.

It took my students a while to understand the significance of friction. Especially in a high speed application like a flywheel.

To start, we had a lot of success using standoffs to align plates and bearings. Because of the high torque and speed, all of our axles have a bearings on each end. Try not to have an axle go through more that two bearings but if you do then you need to be more careful with your alignment. Our main flywheel shaft goes through four bearings so it can be done.

When using more that two bearings you should test the spin. As you insert an axle, give a spin when it is only between two bearings. Then slide it into the third and it should spin just as easily. If not then you have an alignment issue. Many times you can correct the issue by simply adjusting a bearing.

4149 mentioned having wiggle room - the axle should be able to slide a small amount. Be sure to test the spin of each axle before linking gears together and check that the axles and bearings are straight. We used Nylock nuts to secure the bearings but we didn’t over tighten them to prevent distorting the bearing’s shape.

Test your motors individually if you plan on using multiple. You may want to design in a method to do this regularly. We had a four-motor flywheel that was only running three of the motors but it was hard to tell other than we weren’t scoring as well as we thought we should. Also, a few of our teams found motors with internal gears that skip. To test this, use a 60 tooth gear on a short axle and manually spin your motor. If you hear a clicking sound then you may want to use a different motor.

Use the minimal amount of parts on an axle - don’t overdo the shaft collars. Every piece adds weight, resistance, and friction. Nylon spacers work great for alignment and Teflon washers should be used anywhere collars meet metal.

Good luck!

These are all awesome suggestions.

A 3/16" drill bit also helps in making the holes a tad bigger. in those middle pieces where you now no longer have a bearing block because you did the suggestions above, if the shaft touches the metal square hole, that is friction you want to drill a bit out. Too big a hole on the two bearing blocks and it is wobbling about. Adding a bit of tolerance in the middle metal makes for freer spinning (within reason).

The contact surface area of a regular gear is half that of the high strength varieties. The friction on spur gears is along the face of the teeth where they meet to drive the next gear. Adding lubricant to right there at the contact point is useful. Adding it anywhere else is not doing much.

I don’t quite understand why adding lubricant to the gears reduces friction. I understand that lubricant reduces friction on the gears, but isn’t friction between the gears necessary to transfer energy from one shaft to another? After all, the adjacent gears are spinning at the same linear velocity (right?)


When you mentioned the bearing block, did you mean the image below? Sorry, I am a bit confused on how to refer to the parts.

Some bearing blocks aren’t made as well as others either. Some are just too tight. Make sure the one you use is really smooth before installing it.