Gears Skipping

Our team was building a claw for the past week, but encountered the gears were skipping. To fix this problem we decided to change the gears to HS ones. This sort of helped, but the problem continued. The next thing we tested was adding free spinning gears to sandwich the other gears that were skipping. This reduced skipping, but it still occurs.

In general how can we make the gears stop skipping?

If you have any 1/4" pitch metal, you could use some of that to hold the axles together (put a strap going over both axles).
Make sure your axles are supported on both sides and the gears are close to axle supports.

Well This can happen alot if you dont have secure sides
Make sure on top and bottom of your gearing you assemble 2 pieces of metal one on top another on bottom.
what this will do is make sure everything is tight and structurally in sound.

If the problem proceeds write back for another idea

Well, as a general rule, I’ve usually found it good to make sure axle lengths (dead axle length between gears and bearing blocks) are as short as possible, reducing cantilevering or bowing tendencies that would cause gears to skip.

If you have gears meshing with support only on one side (i.e. axle section not sandwiched between structural support w/ bearing blocks), gears will tend to skip more often as well.

A good setup with high torque loads would be to have the bearing block to bearing block distance on either side of the axle just barely able to accommodate your high strength gear and lock collar/few spacers.

Other than that, I’ve noticed that once axles become bent or bowed by too much torque load, causing teeth to skip, its usually best to reduce the torquing force, tighten up the structural support as described above, and replace those axle sections with new pieces guaranteed to be straight.

I realize that this question has migrated over from the “chinese middle school team style” scissor lift discussion, and that any structural reinforcement or redesign to lower torque in the gears would be pretty involved.

Just my two cents :slight_smile:

The best solution I have found is to have metal and bearings on both sides… Make sure the same piece of metal is holding both axles as well… This makes it so the gears can’t bend or move at all, and are locked in position…

Also, maybe look at extending the axles, and putting more support further from the gears… This can help a lot with stabilization…

UncleJoe is correct
i do agree with waht he is saying make sure the axles are locked in to postition and could hardly move just rotate:D

If you can post a picture of your skipping gears, it will be easier to point out possible improvements.

In general, gears skip because the axles are moving apart.
All suggestions above about supporting axles on both sides of the gear, and surrounding with other gears are meant to help prevent this.

The original 1/4" plastic gears sometimes skipped the axle hole.
The solution here is HS gears, axle locking bars, or better yet, don’t send torque through the axle.

As jgraber says, a picture will be a big help. The suggestions above are all good approaches to helping with slipping on spur gears (the round green ones), but another common gear slipping point is on the rack-and-pinion gears on the linear slides. You can usually fix the slipping gears on the rack-and-pinion setup by improving the gear mesh using washers between the gearbox bracket and the slide to shim the bracket down tighter on the rack.

If you take a look at this picture you will see a “floating” 1x strap down the center of the gear train to keep the axles from flexing. It worked really well.

Is that geared 27:625 for torque?

Here’s how we solved our gear skipping problem:
4 12-tooth high-strength gears
And 1/4" pitch 1x metal on the gears powered by the 393s because with the higher torque they were more likely to skip

Another solution that is similar to the 1/4" pitch solution is to use metal barlocks, which are a lot stronger than the 1/4" pitch, but they only work when you are gearing 1:3 or 3:1.

What we ran into our first and second year was we didn’t use the black bearing correctly or failed to fasten it correctly.

Some things that you might want to check are
1: Make sure that your black Delrin bearings are not smooshed. What we realized that if we don’t align them to fit in the square holes of the metal it damages the bearing and make it very hard for axles to spin.

2: Fasten the bearings well. We never use just the plastic rivets. We always secure it with at least one bolt and kep nut.

3: Make sure those bearings never move. When we tested our first transmission the metal 12 t gears slipped and broke. This was a result of the bearings shifting just slightly. You may want to secure the bearings with teflon nuts instead of kep nuts for applicatuons involving high torque.

It’s generally not a great idea to attach a bearing with only one bolt. It might work for bearings with low loads, but it can fail quite badly - we did it on one of our robots this year and the shaft ate its way through several millimetres of aluminium, dragging the bearing with it. It left some nice glitter all over our robot, which in fact is how we worked out it was happening.

If you need two shafts going through one nutrigrain, one way to do it is like this:

one bolt holds the nutrigrain in place, and another bolt holds a nylock nut in whichever corner it wants to pivot towards. With a bit of effort, you can get the nutrigrain to still line up straight.

Honestly I dunno how you guys are using your bearings so that rivets don’t work. I love them!

I’ve had great luck with the rivets when installed correctly with the rivets in the end holes of a bearing flat and the axle run through the center hole. The rivets sometimes need a washer when installed through steel rails, but rarely when installed in aluminum. If the rivet doesn’t fit extremely snugly, either try a different rivet or a washer. They are cheap – if one doesn’t fit right, toss it and try another.

I was browsing the Forum Gallery and happen to stubble across these. These are not mine, I don’t take credit for them.




Also, two bearing blocks placed end to end (or at right angles to make a “L” shape) can often fit in spots where you need two side-by-side axles. The six holes of the bearings would be filled like so
Bearing #1: Screw, Screw, Axle
Bearing #2: Axle, Screw, Screw

This is an example where the plastic rivets don’t work so well. If you want to use the end hole in a bearing flat* use screws to mount it.

(* I nearly always refer to this part as a “bearing block,” as does Blake, even though on the VEX Website it is called a “bearing flat.”)

sorry i didnt read this whole post, but one problem i know of is that if you are using a 24 tooth gear, it is the worm gear and the teeth are slightly slanted in. if you attach it to a normal gear, the gear will get dominated and will start skipping. not sure if someone put his or not, but just saying

I now know why the New Zealanders are so good at VEX - they prototype during breakfast! :stuck_out_tongue:
Wow… that’s a very interesting cereal, though…