Automatic Gear Transition issue

Hi I am a Junior at TKO team 1351. We are using a open looped PercentVbus system with a dog clutch and duel speed gearbox. When we attempt to use the double solenoid to change gears one side of solenoids starts to fire before the other causing us to turn. Have any other teams found any ways to deal with this issue?

Pneumatics right?
If so make sure both of your lines are the same length otherwise you’ll find that one will always fire an nth of a second sooner.
If you can’t find a place where it makes sense to use the double solenoid and keep the lines the same length; try using two single solenoids, one on each side.
Otherwise stop, shift, then continue.

Let me ask a simple question…

Are your shifting cylinders using One solenoid or two? It appears from your description that you are using two.

You would normally use one and then plumb the air lines to a tee fitting and then to both cylinders.


I recommend using single solenoid on your shifting transmissions. Then set the ‘default’ gear to what you plan to start autonomous in. That way it is impossible for the drive team to forget what gear they need to put the robot in, because it happens automatically.

Other than that, there are a couple of things to mitigate the imbalance.

First, one gearbox may require more force to shift than the other, and therefore there is more hysteresis in the shifting cylinder, causing a delay. To determine if this is an issue, disconnect the air tubes, turn the robot off and then manually shift from one speed to the other. If one gets ‘stuck’, then you may need to gently file the inside of the dog gear until it works. In rare cases the pneumatic cylinder may be bad. We had to do file one of our dog gears this year - no big deal if the gearbox is already apart.

The next way to mitigate it, mentioned above, is to make sure the lines to both sides are the same length. Also, remove all flow control valves from the cylinders.

Finally, your driver may be able to mitigate it some by slowing down/stopping before it shifts.