Dart actuator gets jammed

[Tomker]

Hi all,
We are having a major problem with our 6" dart actuator, we use it to raise and lower a shooting arm and are using its entire range of motion. Whenever we lower it to the bottom and have a little bit of force applied on it, it gets stuck and is not able to push back up. Even after we detach the dart from the arm and there is no pressure applied on it, it is unable to open itself.
We are able to spin it by hand but it is much harder than it should be when no force is applied on it.

The last time we had this happen to us we had to disassemble the dart pretty much completely and reassemble it in order to fix this lock and this does not seem like a valid solution especially since it's reoccurring

If anyone ever encountered this phenomenon or is having any idea as to what could cause it and how it could be fixed we are pretty desperate for a solution...

Thanks...

[Chak]

To my limited understanding, you probably reached the end of the ACME screw powering the DART actuator. I'm not exactly sure why or how this happens, but I would fix it with the DART sensor kit, which uses magnets and hall effect encoders to put an electronic stop at either end of the DART.

Now I'll take this thread slightly off track: What lubricant are you using for your DART?

[Aaron Ng]

Is the motor driving the dart spinning, yet the dart isn't moving? or is it stalled.

my best guess is either:

1. You forgot a bearing on the inside of the dart, and when the dart bottoms out, the brass fitting is being press fitted into the bearing hole.
2. The shaft collar on the end of your dart (the gearbox end) has shifted out, so that when you bottom out, the ACME rod unthreads itself from the brass.

of course, these are just guesses, and I cant really say more without more details or seeing it myself. If you cant fix it, your best bet would probably be to just move the mounting point on the shooter closer to the hinge, so you need less extension to get the same angle change, and just never bottom out the DART.

On a side note, we've also had many problems with our dart. The major one being that the magnet inside juts out too much, and disintegrated when we ran it, causing magnet dust to get all over the ACME rod. Taking these things apart is definitely not fun. =/

[Coach Seb]

Wow... we just experienced the same problem here... 6" Dart... we just took it apart and found the 2 bearings in the bearing block to be totally different than what the instruction are calling for.

The assy instruction call for 3/8" ID (AM-0209) but the bearing we received are 1/2" flange... This cause the shaft to wobble inside that bearing block....

Not sure what to do next, we also notice that the black plastic block with the magnet is binding inside the square tube... look like the magnet is sticking up just a bit and binding...

Will keep you posted on what we are doing... anybody else?

[Chak]

Originally Posted by Coach Seb

we also notice that the black plastic block with the magnet is binding inside the square tube... look like the magnet is sticking up just a bit and binding...

Originally Posted by Aaron Ng

On a side note, we've also had many problems with our dart. The major one being that the magnet inside juts out too much, and disintegrated when we ran it, causing magnet dust to get all over the ACME rod. Taking these things apart is definitely not fun. =/

From our recent experience, I would suggest that you file off or otherwise get rid of the magnet binding, before the DART files it down for you!

[Coach Seb]

Update - late last night, i meant earlier this morning... We filed the black block and broke it apartnin the process... Lets just hope a temp repair will allow this to run
We are also actively looking for 2 bearings mfg part #1614zz (am-0209)
http://www.andymark.com/Bearing-p/am-0209.htm
Look like a standard bearing, lets just hope we can find this on a saturday morning. Anyone in southeast MI that has them and wiuld not mind swapping, please pm me.

[IndySam]

AndyMark is aware of the magnet problem. Give them a call for a replacement.

[Dr. Robot]

We filed the opposite side of the block from the magnet slowly and slightly until the black block slid along the inside of the shaft smoothly. Beware not using Hall effect sensors to limit actuator!

We tested the 6" Dart out using code to set our limits, went past the limit, broke the potentiometer, and gave the frame a big ol' inadvertent stress test. The Darts are quite strong. Had to replace the pot. Got it working finally. Very cool when it's functioning.

[Tomker]

The magnet problem is one we haven't encounter yet (and hopefully will not). We did break a few potentiometers two.

We found that the lock could be freed without taking the whole thing apart by spining the dart shaft counterclockwise while holding the motor shaft in place, but that doesn't prevent it from reoccurring.
We tried a few mechanical fixes within the dart itself which seem to lower the chances for it to lock, but don't solve it completely.
With an added mechanical stop, raising the bottom limit and using code to decelerate the motor when lowering the arm, it doesn't seem to get stuck (we didn't have too much time to test it though).

This product really is great when it functions properly, but given its price and how distructive it might be to itself and the surrounding mechanisms, I feel like there's not enough technical information about how to safely work with it. We are really dependant on using its entire range and are not able to change our design at this point.
Hopefully all problems are behind us and we'll be able to focus on other things.

Btw - either we assembled it incorrectly or the highest position for the hall effects is lower than the dart's higheat point, while the lowest position for them is lower than the dart's lowest point.
At the moment we solely rely on the potentiometer and it seems to work fine