What's Breaking?

FIRST General Forum
1

Posted by Dodd Stacy, Engineer on team #95, Lebanon Robotics Team, from Lebanon High School and CRREL/CREARE.

Posted on 3/12/99 7:49 AM MST

What are people finding to be breakage-prone, as the Regionals go forward? There were a number of posts here before we all put our machines in the crates, discussing problems with new components - Victors and Fisher-Price drive trains, in particular. How are those components holding up in the heat of battle? We’re still in that antsy limbo land waiting for our first regional in Hartford next week, getting anxious about what problems to anticipate. So come on, those of you past the butterflies and into the bruises and bandages - what’s breaking?

2

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

Posted on 3/12/99 9:03 AM MST

In Reply to: What’s Breaking? posted by Dodd Stacy on 3/12/99 7:49 AM MST:

One of our biggest fears is smoking motors.

I have discussed on our old forum (see archives) how the new speed controllers really can provide the juice to the drill and Fisher Price motors.

The combination of a little taller gear ratio than we should have, these Victors and Floppies getting caught in our drive wheels has really lost me some sleep.

I think that we have finally got the problem licked but it was a very serious issue in Chicago. In fact, on the Monday after Chicago, we looked at the Fisher Price motors and saw that they had a blob of plastic where there once was a cooling fan !!!

So, for our money, extra drill and Fisher Price motors are very high on the spare parts list.

Still waiting on news from Philly,

Joe J.

P.S. the Globe motors should also be counted among the unprotected motors by the way – FYI, I have an unconfirmed report that, contrary to what I had thought, Globe motors DO NOT have thermal protection inside of them as the seat, window, and power sliding door motors do – this is not a good thing.

If you are running them with a Victor, you should definitely have the 30 Amp breaker in line with them even though under normal conditions they draw less than 20 – short curcuit + Victor = Toaster coils :frowning:

3

Posted by Nate Smith, Student on team #74, Holland FIRST Robotics, from Holland High School and Haworth, Inc…

Posted on 3/12/99 2:59 PM MST

In Reply to: What’s Breaking? posted by Dodd Stacy on 3/12/99 7:49 AM MST:

A state of panic came over HFR headquarters just two days before shipping during a practice session(one of our few). During a driving session, one of our drill motor transmissions started going click-click-click, to the point that we were just sitting there spinning around…we had to rush to the local hardware store to get a replacement motor so we could keep practicing and not have to switch out a non-kit motor in Chicago, when we got a replacement…

: What are people finding to be breakage-prone, as the Regionals go forward? There were a number of posts here before we all put our machines in the crates, discussing problems with new components - Victors and Fisher-Price drive trains, in particular. How are those components holding up in the heat of battle? We’re still in that antsy limbo land waiting for our first regional in Hartford next week, getting anxious about what problems to anticipate. So come on, those of you past the butterflies and into the bruises and bandages - what’s breaking?

4

Posted by Daniel, Student on team #192, Gunn Robotics Team, from Henry M Gunn Senior High School and NASA Ames.

Posted on 3/13/99 7:49 PM MST

In Reply to: Not in the regionals, but just before… posted by Nate Smith on 3/12/99 2:59 PM MST:

My team has had problems with the Drill motors clicking too, but with a little playing around we noticed it was due to the motor being jammed in between hi and low gear. Sometimes the gearbox gets a little sticky. Did you try detatching the motor from the gearbox and seing if it’d still run? Just a thought, may not have been your particular problem.

As for the G-Force 'bot, we have a pair of globe motors hooked up to get us on the puck. Unfortunately the system is slightly skewed so the motors wobble a little when we run the roller. We had a problem with one of the wire’s snapping off at a point we couldn’t get inside the motor. Those wires are small and wimpy, we are now doing everything to keep them from wiggling. We put some heat shrink down into the motor to try to re-enforce the joint and also ziptied the wire to the motor so that the part that wiggled was no longer the joint. Watch those wires!

-Daniel
(GRT)

5

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

Posted on 3/13/99 8:31 PM MST

In Reply to: Re: Not in the regionals, but just before… posted by Daniel on 3/13/99 7:49 PM MST:

Daniel,

It is sort of tricky but you can get inside those motors if you have to.

You have to first drive those 3 roll pins in. Once this in done, you can pull the motor off (be careful the or the guts of the gearbox will come out with it). Now you can get to the screws that hold the motor cover to the rest of the motor, but before you do, locate those roll pins and put them somewhere safe! Also, be careful pulling the motor apart. It has been a while since I did this, but I think you can pull the die cast cover off without affecting the brushes. Anyway, as I recall you can get to the wires when you have the die cast cover off.

Good luck if you attempt it.

Let us know how it comes out.

Joe J.

P.S. Read my note about Globe Motors (which I have yet to write by the way… we shall see if I can link to a message that I have yet to write :slight_smile:

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

Posted on 3/13/99 8:42 PM MST

In Reply to: it is sort tricky but it can be done… … and a repeat of my PS about Globe motors. posted by Joe Johnson on 3/13/99 8:31 PM MST:

Rats,I screwed up the link for the globe motors in the above message.

I KNEW something like that would happen…

Attached is the link I wanted.

Joe J.

7

Posted by Daniel, Student on team #192, Gunn Robotics Team, from Henry M Gunn Senior High School and NASA Ames.

Posted on 3/14/99 1:43 AM MST

In Reply to: it is sort tricky but it can be done… … and a repeat of my PS about Globe motors. posted by Joe Johnson on 3/13/99 8:31 PM MST:

Joe,

You and I both know it’s loads of fun to take stuff apart. It’s about as destructive and uncivilized as they let us get under the name of progress! But still, sometimes it’s quicker just to take the right precautions. Not that that’s gonna stop me from giving it a try…

Wish me luck, I’m off to the operating room! =)

-Daniel
(GRT)

Oh and thanks for the info!

8

Posted by Thomas A. Frank, Engineer on team #121, The Islanders/Rhode Warrior, from Middletown (RI) High School and Naval Undersea Warfare Center.

Posted on 3/19/99 10:42 AM MST

In Reply to: What’s Breaking? posted by Dodd Stacy on 3/12/99 7:49 AM MST:

: What are people finding to be breakage-prone

Hello All;

We’ve found that the Fisher-Price gearboxes are somewhat prone to failure. The output gear loses
teeth after a while, and once it loses one, it self destructs in about the proverbial 5 seconds.

Oddly enough it has occured only on one side of the machine. Since the machine is symetric, this is
weird, and we haven’t yet decided what the cause is. In the meantime, we’ve obtained some spares (looking
for more), and we’ve determined that a failure in a match doesn’t really handicap us, so we’re not too
worried about it. It’s just strange.

I guess that’s what happens when you use something at roughly twice it’s design load!

TAF

9

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

Posted on 3/19/99 5:09 PM MST

In Reply to: Re: What’s Breaking? posted by Thomas A. Frank on 3/19/99 10:42 AM MST:

Tom,

Your machine may be symetric, but your driving may not be. Your drivers may prefer to operate your machine in a method that stresses one motor/gearbox more than another.

Alternately, it could be that the electical lines on one side are longer or have other losses the other does not, thus protecting one slightly from the full stall forces.

Yet another factor could be that even though you machine is symetric, the gearboxes themselves are not. Specifically, perhaps the asymetry puts more plastic in the load path during its worst case loading. This more plastic could either be protecting the failure mode or adding to the failure mode. Either way, one side fails consistently before the other.

Just some thoughts.

Joe J.

10

Posted by Thomas A. Frank, Engineer on team #121, The Islanders/Rhode Warrior, from Middletown (RI) High School and Naval Undersea Warfare Center.

Posted on 3/26/99 10:56 AM MST

In Reply to: machine is symetric but… posted by Joe Johnson on 3/19/99 5:09 PM MST:

Joe;

Many thanks for the suggestions!

: Your machine may be symetric, but your driving may not be. Your drivers may prefer to operate your machine in a method that stresses one motor/gearbox more than another.

We will definitely look at this in FL.

: Alternately, it could be that the electical lines on one side are longer or have other losses the other does not, thus protecting one slightly from the full stall forces.

Nah, already check this part.

: Yet another factor could be that even though you machine is symetric, the gearboxes themselves are not. Specifically, perhaps the asymetry puts more plastic in the load path during its worst case loading. This more plastic could either be protecting the failure mode or adding to the failure mode. Either way, one side fails consistently before the other.

Now that sounds interesting indeed. Can’t wait to get to EPCOT to check!

TAF

11

Posted by Chris, Coach on team #308, Walled Lake Monster, from Walled Lake Schools and TRW Automotive Electronics.

Posted on 3/29/99 6:11 AM MST

In Reply to: Re: What’s Breaking? posted by Thomas A. Frank on 3/19/99 10:42 AM MST:

This probably won’t get read since it’s so far down the list, but I’ll go ahead anyway.

We finally got to play in a regional, and this is what happened:

We burned up one FP motor just pushing the puck. Of course FIRST got a good close up of it on the big screen.

We also tore up one FP gear box. We are currently getting more spare parts to take with us to nationals.

I think that the FP motors and gear boxes are great to do what they were designed for - I just don’t think robots were in mind during the design.

: : What are people finding to be breakage-prone

: Hello All;

: We’ve found that the Fisher-Price gearboxes are somewhat prone to failure. The output gear loses
: teeth after a while, and once it loses one, it self destructs in about the proverbial 5 seconds.

: Oddly enough it has occured only on one side of the machine. Since the machine is symetric, this is
: weird, and we haven’t yet decided what the cause is. In the meantime, we’ve obtained some spares (looking
: for more), and we’ve determined that a failure in a match doesn’t really handicap us, so we’re not too
: worried about it. It’s just strange.

: I guess that’s what happens when you use something at roughly twice it’s design load!

: TAF