Shaft Couplings

Posted by Andy Grady at 2/12/2001 9:25 PM EST

Other on team #126, Gael Force, from Clinton High School and Nypro Inc…

Hello,
Has anyone experienced problems with the special SPI made drill motor shaft couplings?
Thanx,
Andy Grady

Posted by Ken Leung at 2/12/2001 9:57 PM EST

Student on team #192, Gunn Robotics Team, from Henry M. Gunn Senior High School.

In Reply to: Shaft Couplings
Posted by Andy Grady on 2/12/2001 9:25 PM EST:

: Hello,
: Has anyone experienced problems with the special SPI made drill motor shaft couplings?
: Thanx,
: Andy Grady

So far my team never considered using those drill motor shaft coupling, because we are convinced that Dr. Joe’s Drill output shaft will be much more reliable and easier to work with than this coupling.

But looking at the design of the coupling, I can only see couple ways of it failing.

  1. Large load from the wheels are likely to twist the coupling so hard that it tries to spin out, and breaking the pin as it comes out.

  2. Too much bending force from side load of the shaft pushing the coupling against the output shaft of the motor, forcing the coupling to split apart by stripping the thread on socket-headed screws on the side. Which mean the coupling will come off or the connection between the shaft bent.

How about telling us the problems you’ve been facing.

Posted by Patrick Dingle at 2/12/2001 10:03 PM EST

Coach on team #639, Red B^2, from Ithaca High School and Cornell University.

In Reply to: Shaft Couplings
Posted by Andy Grady on 2/12/2001 9:25 PM EST:

: Hello,
: Has anyone experienced problems with the special SPI made drill motor shaft couplings?
: Thanx,
: Andy Grady

We use two couplings on our system… both from small parts. The first coupling is the one specially made for the drill motors, which connect the motors to the 3/8" shafts. We also use a 3/8" to 3/8" misalignment coupler, so any misalignment in the motor mounting does not destroy the gearbox or motor.

So far, we have not experienced any problems with these couplings, even when we press down on the wheels so they stop, and the motor is providing the maximum amount of torque on the shafts and minimum angular velocity (zero).

How about your team? :slight_smile:

Patrick

Posted by Joe Johnson at 2/13/2001 8:09 AM EST

Engineer on team #47, Chief Delphi, from Pontiac Central High School and Delphi Automotive Systems.

In Reply to: Re: Shaft Couplings
Posted by Patrick Dingle on 2/12/2001 10:03 PM EST:

While your test was good as far as it went, you really need to consider the dynamic loading your robot will face.

These loads can be at least twice as high as the stall loads of the motor and are probably closer 3 times the stall torque than 2 times.

If this coupling is breaking under practice conditions, I am scared to death what we will see in competition conditions, were speed matters and the drivers are nervous as Mojo Jojo near the Power Puff Girls.

Perhaps Chemical X will save the day?

Jojo J.

Posted by Matt Leese at 2/13/2001 10:14 AM EST

Other on team #73, Tigerbolt, from Edison Technical HS and Alstom & Fiber Technologies & RIT.

In Reply to: Dynamic Loads are a killer
Posted by Joe Johnson on 2/13/2001 8:09 AM EST:

Methinks someone’s been watching a little bit too much tv… And here I thought you were busy with ship date coming up and all. :wink:

Matt

Posted by Andy Baker at 2/14/2001 1:20 AM EST

Engineer on team #45, TechnoKats, from Kokomo High School and Delphi Automotive Systems.

In Reply to: Dynamic Loads are a killer
Posted by Joe Johnson on 2/13/2001 8:09 AM EST:

Joe,

I’m with ya on the Powerpuff girls… my daughter digs 'em.

But I like Dexter’s Laboratory better. I was trying to get our entire team to dress like him at the competitions, but they never watch Cartoon Network.

Andy B.

Posted by Matt Leese at 2/12/2001 10:17 PM EST

Other on team #73, Tigerbolt, from Edison Technical HS and Alstom & Fiber Technologies & RIT.

In Reply to: Shaft Couplings
Posted by Andy Grady on 2/12/2001 9:25 PM EST:

Ours have been working fine even though our drive train is slightly misaligned (we know about it, we’re just not fixing it until we take apart the robot, paint it, and put it back together). We also are planning to use the keyway slot in the shaft. Are you having problems?

Matt

Posted by Andy Baker at 2/12/2001 11:19 PM EST

Engineer on team #45, TechnoKats, from Kokomo High School and Delphi Automotive Systems.

In Reply to: Shaft Couplings
Posted by Andy Grady on 2/12/2001 9:25 PM EST:

Andy,

We broke one of these couplings while running around the field on Saturday.

The non-threaded part broke. The clamp portion broke off, in the direction of the centerline. One of the screws that clamped it in place was missing, so that’s what we thought caused the problem. We’re going to put on some lock washers so the screws stay in place.

Andy B.

Posted by Ken Leung at 2/13/2001 6:10 AM EST

Student on team #192, Gunn Robotics Team, from Henry M. Gunn Senior High School.

In Reply to: We broke one!
Posted by Andy Baker on 2/12/2001 11:19 PM EST:

HA! I was right about how those couplings will break because of those screws on the side.

Enough of that, can I ask a question?

What makes your team decide not to use Dr. Joe’s drill output shaft? I mean, what factor influenced you and your team to attach the drill motor shaft couplings? And,

I don’t remember if I asked this before… I am so tired from sitting in front of a new Bridge Port milling machining watching the auto feed mill out 2 feet of 1.25" x 1.25" Aluminum into .75" x .75" for 12 hours straight. zzz…zzz… Good thing a student came to me at the end and talked me out of my sleepiness.

Posted by Andy Baker at 2/14/2001 1:15 AM EST

Engineer on team #45, TechnoKats, from Kokomo High School and Delphi Automotive Systems.

In Reply to: Re: We broke one!
Posted by Ken Leung on 2/13/2001 6:10 AM EST:

: What makes your team decide not to use Dr. Joe’s drill output shaft? I mean, what factor influenced you and your team to attach the drill motor shaft couplings?

We have just stuck with what has worked for us, as far as the drill motor coupling. We are trying the SPI coupling because it seems easier. The only tough thing about how we couple to the drive shaft is the drill & tap procedure… and that’s not a problem, as long as we have spares.

Andy B.

Posted by Raul at 2/14/2001 7:45 AM EST

Engineer on team #111, Wildstang, from Rolling Meadows & Wheeling HS and Motorola.

In Reply to: Old habits die hard
Posted by Andy Baker on 2/14/2001 1:15 AM EST:

Andy,

Try making your own solid coupling (about .25" larger diameter than the shaft) and use the “dutchmen” key that I described in an earlier post. You will never have a failure of that joint again (as long as you remove the anti-back drive pins in the drill transmission).

Raul

:
: : What makes your team decide not to use Dr. Joe’s drill output shaft? I mean, what factor influenced you and your team to attach the drill motor shaft couplings?

: We have just stuck with what has worked for us, as far as the drill motor coupling. We are trying the SPI coupling because it seems easier. The only tough thing about how we couple to the drive shaft is the drill & tap procedure… and that’s not a problem, as long as we have spares.

: Andy B.

Posted by Anton Abaya at 2/13/2001 12:14 AM EST

Coach on team #419, Rambots, from UMass Boston / BC High and NONE AT THE MOMENT! :(.

In Reply to: Shaft Couplings
Posted by Andy Grady on 2/12/2001 9:25 PM EST:

: Hello,
: Has anyone experienced problems with the special SPI made drill motor shaft couplings?
: Thanx,
: Andy Grady

well, given that we can catch air over the ramp and have made wicked cool maneuvers, and the fact that we are misaligned and have been abusing them, they’ve stood up pretty darn well.

screws are tight, keyway has never come loose and chains are a little too tight, but those babies have held up…

so far so good. how’d urs break exactly?

-anton