Clutches

[jbbjjbt]

Our team finally has a robot together. We are using 4 wheel drive, with the motors directly driving the largest 5" wheels. The robot is fairly heavy.

In preliminary trials all worked well, even when we added extra weight. However, last night when we drove the robot around for just a few minutes, two clutches popped on one side and then the motors just spun.

Any ideas what our problem is?

Thanks,
Jon T
Team 3543

[Joe Johnson]

We need more details. What motors are you using? What gearboxes are you using? What is the ratio between the gearbox and the wheels? What size and type of wheels are you using? Etc.

Help us help you.

Joe J.

[jbbjjbt]

Originally Posted by Joe Johnson

We need more details. What motors are you using? What gearboxes are you using? What is the ratio between the gearbox and the wheels? What size and type of wheels are you using? Etc.

Help us help you.

Joe J.

The motors are the standard VEX motors: Pn 276-2163 and can be seen here:

http://www.vexlabs.com/vex-robotics-motor-kit.shtml

The wheels are the 5.0 in knobby tires on the 4.0 in hubs: Pn WHEEL-KNOBBY-2PK and can be seen in the wheel kit:

http://www.vexlabs.com/vex-robotics-wheel-kit.shtml

We have the motors directly attached to the wheels.


From the chart at:
http://www.vexlabs.com/vex-robotics-motor-kit.shtml

this gives a velocity of 2.18 fps.

Jon T
Team 3543

[fredliu168]

tighten the 6-32 screws more...? The clutches shouldn't fall off...

wut do u mean motors directly attached to the wheels? You mean the clutch is attached to the axle and the axle is attached to the wheel right...?

[jbbjjbt]

Originally Posted by fredliu168

tighten the 6-32 screws more...? The clutches shouldn't fall off...

wut do u mean motors directly attached to the wheels? You mean the clutch is attached to the axle and the axle is attached to the wheel right...?

I'm sorry. The motors are attached to the clutch and the clutch to the wheels using a driveshaft. When I said directly I meant there are no gears.

The clutches are not falling off. They are slipping so that no torque goes to the wheels. I assume that the teeth inside the clutch are damaged as there is no visible damage on the outside of the gears.

Jon T
Team 3543

[DRIVEN Caleb]

Originally Posted by jbbjjbt

I'm sorry. The motors are attached to the clutch and the clutch to the wheels using a driveshaft. When I said directly I meant there are no gears.

The clutches are not falling off. They are slipping so that no torque goes to the wheels. I assume that the teeth inside the clutch are damaged as there is no visible damage on the outside of the gears.

Jon T
Team 3543

With the clutch off, does the motor spin?
If it does, I would suggest just using another clutch, since when clutches break, it's usually because the plastic has been warped and this can't be fixed.
We've had many clutches where the plastic around the shaft rubs down to be a circle, and then the shaft just slips.

If the motor doesn't spin, then it's possible that the gears in the motor itself are stripped. A quick fix would be to just replace the motor, or you could take it apart and replace the gears with the provided spares...

Caleb S.
DRIVEN team 2158

[jbbjjbt]

Well, it turns out the clutches were torn up on the outside and fine internally. It also appears that the axles were installed loose enough to slide toward the wheels allowwing the clutches to be torn up. So we are replacing the clutches and not changing the design. If we tear up the clutches again the team will have to rebuild and install gears.

Jon T
Team 3543

[gblake]

jbbjjbt - See you Saturday at GFHS - If you are still having problems, look me up or ask Mr Willis to have one of the GFHS students take a look at it.

Blake

[jbbjjbt]

We replaced the clutches and still have some issues. We took off the tires so there is less friction when turning and that helped. We still get some popping of the clutches on hard turns but its not continuous. So I don't know how long the clutches will last. I have clutches, gears and a little metal on order but it isn't scheduled to arrive until Monday.

Blake,
We still plan to be there Saturday. I hope with a robot that will drive all day.
Jon T

[zerozio2u]

you can use motors without clutch but you really need to be careful with what you are doing becasue the inner gears could be strip. I have used motors without clutches for for many of my projects for about two years now and i still havent had any problem with them. this is just some examples of the parts.

[jbbjjbt]

It seems the main way we tore up the clutches was by having the axle come loose. It would slip part way out and then spin in the clutch and tear up the clutch. So I think it would be a bad idea for our team to put the axles straight into the motor.

Jon T
Team 3543