The Lack of Spares ... Good or Bad

[MrForbes]

Philosophically speaking....

It's good to have a lack of spares for some items, because you are forced to make a decision about the wisdom of using that part in your design. You can decide to accept the risk of not being able to replace it at a critical time, or you can decide to keep working on your design until it contains few or no parts for which you cannot obtain spares.

It is bad to have a lack of spares because the above lesson is a tough one to learn by experience!

[Jon Stratis]

Originally Posted by squirrel

Philosophically speaking....

It's good to have a lack of spares for some items, because you are forced to make a decision about the wisdom of using that part in your design. You can decide to accept the risk of not being able to replace it at a critical time, or you can decide to keep working on your design until it contains few or no parts for which you cannot obtain spares.

It is bad to have a lack of spares because the above lesson is a tough one to learn by experience!

I agree wholeheartedly with this - the lack of availability of some items is a design constraint that makes developing a suitable engineering solution difficult! In professional life, you come across these types of decisions all the time - do you do the "safe" thing that might not be as good, or do you accept the additional risk of trying to do the best performing design? There's always a trade off between risk and performance on practically every project you'll work on after school - it's good to start understanding how that trade off can affect your success.

That being said, i'm sure every team would really like some spares

[Jeff Waegelin]

I am of the firm belief that all Kit motors should be available for purchase somewhere - either through IFI, FIRST, or the manufacturer's distributor network. If FIRST is going to require that teams use only this year's model of a motor, they should be responsible for finding enough motors, and a way for teams to purchase more. Not being able to purchase more of a part should never be considered part of the challenge of design. Things happen in prototyping, building, and competition. You should never be forced to alter your design, or fear for the life of your motors because of a lack of availability.

[MrForbes]

I don't think that all the motors need to have spares available. In our young team's 2.5 year existance, we have never used a motor that does not have spares available...which means the only motors we've used are the small CIMS and an RS540 banebots motor.

This year we are using only pneumatics for ball handling. There are many reasons, and the availability of spares is one of them.

[AndyB]

Also keep in mind that in the real world, you may be put into a situation as a project leader or engineer where you must work with limited resources. It just adds another aspect to problem solving. Not only do you have to work your way around it, like you would in real life, but it also forces you to communicate alternative designs as well.

FIRST is all about preparing young people for careers in STEM and business. I find it hard to believe that you will never ever run into a situation where you have limited supplies, you can't get spares of something, or you have to make multiple design choices which allow interfacing with more than one part (ie Motors.)

Life ain't always beautiful, but its a beautiful ride...

[JesseK]

If we only have 1 of something, and it is the best option for us to use, then we need to have a design that extends the longevity of the item. In other words, we need to hyper-engineer our project to ensure this one failure point will never fail. We have to account for every scenario that could cause our item to fail and prevent that scenario from happening.

Specifically for the FP's:
Limit switches to ensure it doesn't extend past a limit
Bumper switches in case your mechanism hits something
Fans with ducting straight into the holes to prevent overheating, but more importantly:
A design that keeps the load of the motor for best-case normal operations way under the specs, specifically current draw

To engineer this much takes experience or alot of research/time. It's up to each team to consider the time investment vs return & liability. For 1885, we have found a "suitable replacement" scenario and will produce both motor/gearbox/sprocket combos just in case our primary option fails.

However, general practice in the real world would not pick a part for a valued customer knowing that there is no way the company could support the product/part after production. Companies lose money that way.

[dtengineering]

In regards to FP motors specifically, there is nothing in the rules preventing you from running them off a lower current circuit breaker, or putting a fuse in line with the motor to ensure that it will never exceed a particular current. Yes, that also means that it will never exceed a particular torque.

However given that FIRST is largely about learning, and that part of learning is making mistakes, it would be extremely unfortunate to have a team show up for a regional with a major component running on a part made of unobtanium and have it blow on Thursday or Friday. Yes, there would be learning taking place, but at the cost of the overall experience for both the team with the busted part, their partners and their opponents.

Fortunately, while we have broken many components at competitions... up to and including the RC, we have never found that we could not get the part replaced or repaired in time to have a good experience at the competition... even if it meant that for a match or two we were partially unable to compete at our full capacity. (An appropriate consequence for a poor decision is a big part of learning!) We have also been able to help other teams get up and running/repaired in time to have a good weekend as well. So I guess my conclusion would be that just because spares aren't available for sale doesn't mean that spares aren't available. In fact there is a pretty good chance we'll have two spare FP's in our pit, as well as some advice on how to not smoke them, should a team in Portland or Seattle need one.

Jason

[EricH]

The lack of spares is both good and bad.

Good: You are forced to design so that the original lasts. If you do it right, you get the Mars rovers--more than ten times the original mission length, and they are still going. You may also design for a suitable replacement to be easily placed in in case of emergency. It forces creative engineering.

Bad: If something goes wrong and there isn't an acceptable replacement, you're toast. In the real world, you have to have at least a backup plan, if not a spare. Spares are easier (they just slap in, and you can make them with little extra effort).

Overall, the lack of spares is not exactly a good thing.

Oh, and if the FP service people tell you to bring your "toy" in so they can replace the motor, just do it if you are in range. I want to see their faces when you bring in your robot...and explain that this is why you just want a motor.

[MrForbes]

I expect we will continue to bring unused "critical spares" to the regionals for other teams to use as needed....it's a good way to cut down on the clutter in the storage room, and help out other teams at the same time.

[Jeff K.]

For the FP motor, if someone could find out which vehicle it came from, everyone will probably be able to contact their relatively local service center to get a spare or two. When I call them, they give me a hard time saying that they are trying to help me, but they need the part number from the vehicle it came from. I just tell them that it didn't come from a vehicle, and it came in the KOP and what we are. She just goes back to asking which vehicle it came from...

[Cory]

Originally Posted by Jeff K.

For the FP motor, if someone could find out which vehicle it came from, everyone will probably be able to contact their relatively local service center to get a spare or two. When I call them, they give me a hard time saying that they are trying to help me, but they need the part number from the vehicle it came from. I just tell them that it didn't come from a vehicle, and it came in the KOP and what we are. She just goes back to asking which vehicle it came from...

A service center told someone from a team that FIRST bought every single motor of the correct model (This is from the FP thread thats been going on for a few days)

[Jeff K.]

Originally Posted by Cory

A service center told someone from a team that FIRST bought every single motor of the correct model (This is from the FP thread thats been going on for a few days)

Yeah I didn't see that until after I contacted them. If one service center knew about it, then shouldn't all of them be aware? Instead of making me have to explain 3 times how I did not get it from a vehicle. Oh well.

[artdutra04]

While the concepts of constricting the design constraints is a good idea, since it can lead to a better end product (since it requires a lot more thought in the process), not having spares is a bad idea.

What if a computer company like Dell or Apple or Lenovo told their engineers that there would never be any way proclaim a spare battery or hard drive for the laptop they were designing? Even though they might be exceedingly careful with their design, I guarantee you that there will be a small percentage of batteries or hard drives which would fail prematurely, due to any number of reasons which might be beyond the engineer's control.

Stuff fails in the real world, and if you do not design accordingly you won't succeed.

[AdamHeard]

I've worked at Northrop Grumman (a major aerospace company) for several years. From what I've seen there, they would never use a product or part to which no spare or replacement was available.