Drive Assembly Sprockets are Custom Bored
 

We just took our transmission assembly (out of the kit) down to Bearing, Belt, and Chain, Inc. thinking that we could get a couple of more sprockets that would fit right onto the assembly so that we can get our machine driving by this weekend. They informed us that the sprockets for these are custom bored (as designated by the "b" in the model number). They said that we could use standard keyed sprockets but if we did that we would have to have them pressed onto the shaft.
We thought FIRST was doing us a favor by making a ready to go tranny/drive assembly, but if we want to go four-wheel-drive with a different sized sprocket, then we're pretty much out of luck. I can't figure out why they would limit us like that, but maybe you (Chief Delphi Participant) can shed some light on it?
Update: And to get the same "custom bored" sprockets from IFI will cost us an additional $80 for about $14 worth of sprockets if they weren't custom bored.
Whaaaaaaaaaaaaaaaaat?

Re: Drive Assembly Sprockets are Custom Bored
 

We noticed that today as well. I haven't had a chance to check it with my calipers yet, but one student suggested that it was close enough that we could heat up our standard 5/8" bored sprockets and press them on. Might be worth a shot, but check it first with some calipers to see how big the difference is, because it maybe harder to get off then it was to get on (especially if the transmission is all put together).

Re: Drive Assembly Sprockets are Custom Bored
 

Yeah, we're in the same prediciment.

:(

Re: Drive Assembly Sprockets are Custom Bored
 

The transmission output shaft is metric - 16mm dia with a 5mm keyway.

(as taken from the transmission manual found here: http://www.ifirobotics.com/kitbot.shtml in the output shaft drawing spec)

Paul, please correct me if I'm wrong.
Teams can buy any size sprocket they want (with a bore less than 16mm), rebore it to 16mm and rebroach to 5mm. There is probably a fancy way to broach this keyway, but the simplest way is just to buy a metric broach set.

Anyone else have advice?

Re: Drive Assembly Sprockets are Custom Bored
 

I'm trying to be gracious and professional about this, but ... before anyone calls this a "predicament" or thinks they are "limited" please think twice. First off, how much design, engineering, and manfacturing time was spent by Paul, JVN, and IFI? What if you had to include that time in your build and/or deduct it from your allowable expenses? 80 dollars would seem pretty cheap then. And FIRST DID do you a favor. Try and build this with last year's kit. I don't remember anyone promising you 4WD right out of the box. What you were promised was a robust gearbox and ready made chassis to get you rolling quickly.

Relax. Have fun. Enjoy the improvements. Build what you want to. Thanks Paul, JVN, IFI, and FIRST.

Re: Drive Assembly Sprockets are Custom Bored
 

Ok, according to my nifty little (well, it's like 4" thick) KBC tools catalog, a 16mm drill bit will run you approximately $16

as for the keyway, if you have a mill, mill a key, it wont be pretty, but it's a hell of a lot cheaper than a broach set.

Or, get your freshmen to start filing ;)

Re: Drive Assembly Sprockets are Custom Bored
 

Mr. Kressly,

I don't think anybody is attacking the work Mr. Neun did on the transmission kit this year. From what I have seen, the transmission is top-notch. Mr. Neun has also been extremely helpful on these forums and I appreciate the work he has done. I also don't think Mr. Neun is responsible for what was and what was not included in the kit of parts.

However, FIRST could have informed us of the custom modifications made to the sprockets and informed of us the fact that we could not use standard sprockets unless we made modifications. I also feel FIRST was misleading on how easy it was to build the drive system. Most teams DO NOT have access to the type of machinery needed to custom bore and/or press the sprockets onto the shaft. This isn't the biggest hurdle in the world, but it is a major annoyance and it will cost us (even it is just 80 dollars, it adds up!).

Re: Drive Assembly Sprockets are Custom Bored
 

You could also turn down the output shafts to 5/8" on your handy dandy lathe. You could also mill a 3/16" keyway on the opposite side of the shaft from the existing 5mm keyway.

-Joel

Re: Drive Assembly Sprockets are Custom Bored
 

How much would it have cost you to make those gearboxes?

The answer is either:

A) We couldn't, because we don't have access to a mill or lathe

-or-

B) A whole hell of a lot of money and time.

Major annoyance? How big of an annoyance would it be to make the darn things from scratch? How annoying would it be to design it?

The value of those gearboxes should be measured in the hundreds of dollars, so even a measly 80 is quite a deal.

and like I said in my previous post, buy your $14 sprockets, buy a $15 16mm drill bit, and I'm sure you have files and then you're good to go. That adds up to about $50 less than if you buy them from FIRST, so you should be happy

Have you seen the FIRST drive systems of the past? They were big pains in the $@#$@#$@#. This one is incredibly easy and light years ahead of anything they've ever given us before. You could set it up in an afternoon. FIRST isn't responsible for making sure every team can have a driving robot, but they choose to by giving us this.

Re: Drive Assembly Sprockets are Custom Bored
 

I don't see in any way how this is an "annoyance". A complete lightweight frame and 4 motor drive train out of the box. So FIRST only gave enough sprockets for 2 wheel drive, but you can upgrade to 4 wheel drive for $80. Thats four custom sprockets that you can attach to your kit bot and almost instantly have a 4 motor, 4 wheel drive robot base. Sounds like a pretty good deal to me.

Eric

Re: Drive Assembly Sprockets are Custom Bored
 

OK I have 2 things to say on this subject:

If you dont like what is in the kit, then be thankful you did not do FIRST in the past. This is by far the best quality and most useful kit ever provided.

If you don't want to buy an $80 custom sprocket, then don't. just use the provided 21 tooth sprocket on the gearbox output shaft. You will have to cut some pieces of PVC or aluminum tubing to do this. If you can't cut PVC or aluminum, you can buy a bunch of large washers at your hardware store.

You can also skip the sprockets that FIRST gives you to put on the wheels. In fact this might be a good idea because the provided wheels have low traction. This does require a bit of creativity and custom designing. You will need the following items:

Some 5" long 3/8" bolts for axles.
some wheels with bearings (3/8" bore).
some sprockets of whatever size you choose to use (1/2" bore is probably good).
some 3/8" bore 1/2" OD bronze bushings.
some spacers.
some small diameter bolts long snough to go through the sprockets and the wheels.
the ability to drill some holes through the sprockets and wheels.

Press the bushings into the sprockets, and place them on the shaft with the wheel. Drill holes through the sprocket and wheel. Bolt them together. Cut your spacers to position the wheel sprocket in line with the transmission sprocket. Put another sproket on the other side of the wheel. make a simmilar wheel, but with only 1 sprocket on it. run chain from the transmission to the wheel with 2 sprockets, run chain from the 2nd sprocket to the wheel with only 1 sprocket.

for a 4 wheel drive setup, this might cost you around $80 to $100, the same as your replacement sprockets. If you were to make your own drivetrain from scratch it would cost you well over $400, and maybe not be as high quality.

Good luck with the driving!

Rob

Re: Drive Assembly Sprockets are Custom Bored
 

This is a good example of engineering for all students. Many US industries have converted to metric, it is the US general public that does not have/use metric on a regular basis.

Re: Drive Assembly Sprockets are Custom Bored
 

WARNING! Long Post!

Mark & dukesAZ,

"They" is me. Do not blame FIRST for the design decisions made on the gear box. I designed the entire thing. JVN had a lot of design input, but he spent most of his time designing the frame and interfaces. Your beef is with me. Your beef is not with FIRST, IFI, JVN, or anyone else. That being said, I have volunteered my time since July to design, test, and source the transmission gearbox, so be a little more tactful when expressing your dissatisfaction (that one was directed at Mark). The transmission manual: yep, that was me too. I did not receive one red cent from FIRST, IFI, or anyone else. I spent the equivalent of an entire six week build season making sure all the criteria were met (see the transmission manual page 1-2 for details). As for my qualifications: I have my Master's Degree in Mechanical Engineering from the University of Michigan and hve been working at FANUC Robotics for 8 years designing and engineering mechanisms for industrial robots.

Every single choice I made on that gearbox was weighed against many others. The custom die casting, for example, was chosen due to the volume of housings we needed to make and the cost (yes, cost) impact. Our criteria was to beat the cost of the drill motor solution or it was a no go. The gears are cut from a long roll formed bar and are sliced to our specs. They can be replaced with Martin equivalents. As a matter of fact, I made the prototypes from Martin gears. Martin can bore any size hole you want and they actually put the keyway in, too. Call Martin sprockets and fax them the drawing at the end of the manual and see what price you get. I bet it will be cheaper to buy the stuff from IFI, because we got a volume discount on the sprocket modifications. Better yet, take Corey's advice and modify them yourself. The standard 21 & 28 tooth sprockets have a 1/2" bore. Buy a 16mm drill and a 5mm broach set from MSC or McMaster and you are all set for the input sprocket. Bottom line is that if you do not like it, then build your own. There is no way you will get the same functionality for the same cost.

dukesAZ,

The custom modifications are clearly spelled out in the transmission manual on pages 5-13 and 5-15. In fact, every single part drawing is shown in chapter 5. Misleading? The standard drive base can be put together in a matter of hours. My 4 year old son put together one transmission housing in 30 minutes by just looking at the pictures (yes, he knows how to use Allen wrenches). Custom modifications are essential to get cost out of high volume products (over 2400 units). If you use standard components, the cost goes way up and it would have been cost prohibitive to put them in the kit.

In closing,

I expressed my dissatisfaction with FIRST at the end of last year. I said they were not doing enough to help the rookies and lower funded teams be ready to drive on day one of their regional. I offered my services and they took me up on my offer. If you are not part of the solution, then you are part of the problem. I suggest you start being part of the solution.


Paul

Re: Drive Assembly Sprockets are Custom Bored
 

Paul and everyone else.
Calm down people.
One of the major problems that I see with FIRST is that one cannot offer the slightest bit of criticism of FIRST without someone else getting overly worked up about it and starting a flame war.
The first couple of responses to my issue (up to and including JVN's) were what I was going for by posting this thread. I wanted to make sure that I was not the only one with this problem and I was hoping someone could offer a fix. Low and behold, JVN told me of a quick and easy fix. I would have been happy if the thread ended right there, or even if you would have chimed in with your reasoning.
What makes me and my team upset is that we cannot put our beefs with FIRST out there without someone feeling as if they need to be the defender of the almighty FIRST. Criticisms should be allowed. According to everything I've heard from the regional directors, FIRST wants to hear them.
They, and I will include YOU (Paul) in this since you developed the tranny, should be the only ones that need to answer to the criticisms. The regular team mentor, coach, or member that thinks they have the right to get upset with me for criticizing FIRST is the real problem.
Can't we all just get along?

Re: Drive Assembly Sprockets are Custom Bored
 

Mark,

I re-read your initial post thinking I might have responded harshly. Nowhere in that post did you ask for help. Since you are an advocate of constructive criticism, I will give you some of my own.

In your initial post, you could have just asked for the dimensions and specs. I would have been the first to respond with the answer. Instead, you took "pot shots" at the individuals who provided the parts. Now I know that sometimes words on paper don't come out quite like intended, so I will just chalk this up as a misunderstanding.

I will assume that you have good intentions and want to improve FIRST for not only your students, but all the students touched by this competition. If you have any other questions or concerns about the transmission, feel free to ask.

-Paul

Re: Drive Assembly Sprockets are Custom Bored
 

Must say its an excellent design Paul, Props on that!

Re: Drive Assembly Sprockets are Custom Bored
 

All heat aside, I love the transmission. I also like the information in this post, I most likely would have missed the shaft being metric with out it. Being responsible last year for getting 3/64" key ways cut by mistake in a pair of 30t #25 sprockets, (was supposed to be 5/8" bore with 3/16" key) we used the T shaped key way and adjusted. I took one look at the casting and said wow, custom die cast and low cost to make so many, somebody did a great job with the over all design. After my first read of this post, I looked at the output shaft and thought, Cool start with 3/4" hex stock and go from there if you want to get to 5/8 final out. My second read finds use a metric drill and metric broach, if you need a different final sprocket. Thanks Paul for the great work and the learning that has flowed from it. Tom Cooper

Re: Drive Assembly Sprockets are Custom Bored
 

Those gear boxes are are gold to our team. We only have hand tools and very little cash. Thanks for your time and effort.

Re: Drive Assembly Sprockets are Custom Bored
 

I agree with Mark, FIRST should have given us some heads-up before custom boring the sprockets and making it costly to upgrade our drive system.

Re: Drive Assembly Sprockets are Custom Bored
 

I had really hoped all the moaning about the sprockets would stop now that FIRST is selling the sprockets you need for $20 each.

Everyone who has complained seems to be forgetting that FIRST and other individuals bent over backwards to make sure that EVERY team could have a driving robot. They didn't have to. And not only did they develop the gearboxes and frame, they compiled a fantastic guide to using them, and possible upgrades.

FIRST made an option available to you. You don't have to use it. You don't have to spend the $40. Since their solution costs so much, why don't you develop your own? I can tell you right now, you won't be able to. You'll spend hundreds of dollars to make the same thing FIRST did, and who knows how reliable it will be.

Seriously guys, no matter what FIRST does, there's always something being griped about. As has been said many times in the last few weeks, if you're going to complain, do something about it. Offer your services to FIRST. Find a supplier that will donate sprockets to FIRST. This is a lot like voting. You have no right to complain about our political system if you don't vote. If you don't do anything to resolve what you're complaining about, DON'T COMPLAIN.

Re: Drive Assembly Sprockets are Custom Bored
 

<sarcasm>
:ahh: :ahh:
What!! The kit isn't a lego set!!!¿?¿?¿?¿? You actually have to build and design something? This is terrible!!
:ahh: :ahh:
</sarcasm>

This is relly ghetto but i have dome something similar before and it worked. Run the gearboxes at full speed. Get a piece of coarse sandpaper, a pair of gloves and sand that sucker down.

Re: Drive Assembly Sprockets are Custom Bored
 

Four wheel drive is simple. Its called sprockets on the other two wheels, and one chain with a tensioner.

Re: Drive Assembly Sprockets are Custom Bored
 

Are you referring to making the sprockets fit on the shaft easier or something like that? We use a tool I call the "vertical lathe" (there actually is such a thing, but this is not it). We pop the shaft into the chuck of the drillpress, spin it up and put a nice file, sandpaper, or preferable emery cloth to it. Works every time. Slightly less ghetto.

Re: Drive Assembly Sprockets are Custom Bored
 

Keep in mind now, the most advanced piece of machinery we have is a drill press... no lathe, no mill, so if we had been in the same problem (which we weren't, but anyway), we would have had to get the sprockets custom-made by some machine shop.

Re: Drive Assembly Sprockets are Custom Bored
 

But, if the chain breaks, you can't drive on that side. I've seen enough chains break during matches to want the extra redundancy.

Re: Drive Assembly Sprockets are Custom Bored
 

My team ran into this. We opted to run with the two wheel drive, but to drop the 21 toothed sprockets for 15's (we wanted to slow down a bit, rookie driver and all). I was in charge of ordering the new sprockets, and just as I was on my way out shop one night, I asked a student to measure the shaft for me so I could order them that night. He quickly grabbed a pair of calipers, and I guess 16mm was close enough to 5/8ths that he figured he had made a mistake and assumed it was 5/8ths (all our other drive train shaft is). I probably would have done the same.

So I ordered sprockets from McMaster with a finished bore for 5/8ths. Needles to say, I was confused when the sprockets just wouldn't go on!

After a while, we figured it out. 5/8ths of an inch does not equal 16mm's it seems. The solution was to ream out the bore and 'press' the sprocket on with a hammer. It was tighter then I would have liked, and I hope we never have to take that thing off, but it works. I probably spent more time trying to figure out why things didn't fit then I did fixing anything.

Moral of the story- Sometimes, that metric system will show up in the most unlikely of places. Read your manuals!

Although, now that I think of it, I probably still would have gotten the same sprockets. I'd rather have to take a few passes with a reamer then drill/bore out a unfinished sprocket. But I'm lazy.

My only critique of the kit trannys is that ours seem to run out lubrication real fast. That may have something to do with how we (mis)assembled them, but I notice that they need periodic lube jobs. If thats my only beef with them, I'm happy enough to go back to dealing with all my real problems on the bot, like where I'm going to find room for ballast.

-Andy A.

Re: Drive Assembly Sprockets are Custom Bored
 

I did the same thing and assumed a 5/8" bore for the sprockets. So we were rather surprised when our ordered sprockets would not fit. Therefore, I second Andy A's suggestion to READ THE MANUAL. It was unexpected, but easily designed around, and if we were delayed in getting our bot mobile, it was no one's fault but our own (mine). We just took the ordered sprockets back and quickly ordered 2 more 21 tooth kit sprockets.

That being said, the new kitbot transmissions are AWESOME!!! They are easy to assemble, can be used for a variety of configuations and purposes, and are quality-made. If you used the transmissions from years past, you know that there really is no comparison. Any team will be hard pressed to come up with a superior single speed transmission.

All I can say is thank you Paul Copioli. I don't know you, but I sure like your work! :)

Re: Drive Assembly Sprockets are Custom Bored
 

I will second that!

-dave

Re: Drive Assembly Sprockets are Custom Bored
 

I sure hope the 2006 game includes the same transmissions (hint) and that we can re-use the 2005 transmissions (hint, hint, hint) in 2006. Wouldn't it be cool to have 250 omni-drive teams??

Re: Drive Assembly Sprockets are Custom Bored
 

My experience in design and building is as a mentor for the past four years (including 05) on a team with no engineering support, limited funds, few tools but lots of students with grit and determination to get things done. We have gone from homemade to ready made and I can attest that this year's kit of gears and motors was the best ever. Last year we tried a self-designed system using similar motors, sprockets from the local supplier and chain. We crashed and burned (literally) so many times that we spent the entire first day of the competition last year running between teams trading parts, information and expertise with a robot that we never ran after the first go-round on day 1. This year we had the robot built and running by the end of week 1! For my money this helped us concentrate on making things right instead of trial and error. I'd like to personally thank the person or people responsible for the entire kit and also for their tireless efforts in making the process work for ALL teams, not just those with unlimited tech assistance, tools and funds. FIRST should be about inspiring students to reach beyond what they thought possible. This concept kit did just that. Keep up the good work and make next year's kit just as user-friendly for ALL teams!
:)

Re: Drive Assembly Sprockets are Custom Bored
 

did anybody else have the problem with the lockwashers grinding in the transmissions? we had this horrible noise and saw they cut a groove into our gears...the manual says it was really rare...but it happened to us. And the washers were on there exactly as they had told us...they just seemed too big. We worked it out, but it was quite a scare to hear grinding in the gearbox.

Re: Drive Assembly Sprockets are Custom Bored
 

The lockwashers on the end of the CIM motors came in 0.010" too large on the diameter. The prototype boxes did not have this problem. The lockwashers will be replaced by something else next year (if FIRST wants to use them next year. I really do not know that for sure, but I am pretty positive we will see them again). We are using the set screws in our transmissions and they are holding up fine. Remember, you must use loctite on the threads of the set screw and make sure the set screw is clean and dry before applying the Loctite.

Re: Drive Assembly Sprockets are Custom Bored
 

If I remember correctly there were two sizes of the plastic washers and each size had a particlar place it needed to be. That could be what caused the grinding noise... :confused:

Re: Drive Assembly Sprockets are Custom Bored
 

What we are talking about is the metal locking ring that looks like a washer. It is round on the outside and has little fingers on the inside. You press it on the CIM motor shaft to lock in all the components on the shaft.

Re: Drive Assembly Sprockets are Custom Bored
 

It happened to us, too. We eventually just popped them off and relied on the setscrews. So far, so good, but our tournament starts tomorrow...

Amusing anecdote: we first tried to reduce the diameter of the washers by holding a file up to them as they spun. Ha. Ha ha. Ha ha ha. Want to buy a file with a nice groove carved into it by a spinning washer? Those washers are made of hard steel...

Re: Drive Assembly Sprockets are Custom Bored
 

I just ground the OD down on a bench grinder--no problem at all, and took about 2 minutes each.