Beware - transmission output shaft is not 5/8"!
 

You cannot just slip a standard 5/8" sprocket on the transmission output shaft. This shaft is metric, with a diameter of 16mm, or 0.63", NOT 0.625".

You will need either to turn the shaft down to a smaller diameter on a lathe, or drill out your sprocket to 16mm with a metric drill. This year and last year we turned the shaft down.

Re: Beware - transmission output shaft is not 5/8"!
 

This came up last year as well. Everyone just took a quick look at the shaft with a pair of calipers and assumed it to be 5/8ths. Then we all had to figure out why we couldn't get any sprockets to go on.

I think most teams just ream out the sprockets, and call it even. It's a pain, but hopefully teams learned a lesson and took the time to look at the drawings this year.

Thanks for the reminder though, I had completely forgotten.

Re: Beware - transmission output shaft is not 5/8"!
 

All I can say is WHY?!?

Why give teams a great transmission and make a drive system easier for teams to get up and running, but then make in necessary that teams turn down a shaft (a keyed shaft for that matter!) or ream out sprocketts simply to change the output sprocket?

WHY?!?

Does anyone know of a source of various 16 mm bore 35 pitch sprocketts with a standard keyway?

Perhaps I am a bit frustrated because a great deal of our work time goes into making non-standard parts work together. For teams with limited machining ability, this is a real issue. Yes, I know. It has always been an issue, but with the Kit Chassis, Kit Transmission, etc. FIRST has moved a great deal towards making things easier, but a 16 mm output shaft on the transmission seems to be like "Two steps forward, one step back".

(This whole thing was not an issue for us last year, because we made our own shafts that fit the Kit Transmission. I'm speaking for those teams who have limited machining opportunities - like us this year - we lost our shop!)

-Mr. Van
Coach, 599

Re: Beware - transmission output shaft is not 5/8"!
 

Yea its a bit of a hassel. Just ream out the sprokets. I think this is the easiest approch. However, You may have to cut the keyway a bit deeper to get the key to fit after reaming.

Ken

Re: Beware - transmission output shaft is not 5/8"!
 

Consider it part of the challenge. Sure it would be easier if they were 5/8" but part of the challenge of FRC is to work with what you have in the time your given. This is just another one of those real world simulations. Consider that in the rest of the world 16mm may be more common than our 5/8". Maybe this is a hint from FIRST to start moving toward the global metric standard. It is a bit odd though to have a 16mm bore on a 3/8" (#35) chain sprocket.

Re: Beware - transmission output shaft is not 5/8"!
 

Why metric? Why not?!?

There are only three countries in the world that haven't changed over to the metric system - Liberia, Burma, and the United States. Using metric is not backwards, but rather the correct way to do things nowadays. We silly backwards Americans still cannot get that through our heads.

Re: Beware - transmission output shaft is not 5/8"!
 

Also, I believe that the answer given by the transmission designers was that the output shaft was 16mm because it was the most cost effective method, while still giving teams the option of using 5/8ths sprockets with relatively little effort.

Reaming out sprockets is fairly easy. If you can not do this, then consider turning down the output shaft either by cutting on lathe or by turning it and liberal use of sandpaper. None of the methods of using 5/8ths hardware is ideal, so you should consider buying sprockets from IFI through their website. You are stuck with 21 teeth from IFI. Another option is to look around and find a 16mm sprocket supply. They are out there.

-Andy A.

Re: Beware - transmission output shaft is not 5/8"!
 

Here's the deal. FIRST is not a "buy it and build it robot kit" competition. If you can't be resourceful enough to at the least make do with what they give you, there is no way you will survive in coming up with your own designs. I can't believe that FIRST is so generous as to provide such a great gearbox, and some of you still complain and find every little thing wrong with it. If you don't like it, make your own. But let's not complain when we are getting magnificent items in the kit that teams just a few years ago could only wish for.

Back in the day, we never had beautifully machined pieces included in the kit of parts. Hex broached gears. Cast housings. We didn't even have CIM motors.

Be thankful for what you have, not frustrated with it because it doesn't exactly suit your needs.

Re: Beware - transmission output shaft is not 5/8"!
 

I agree 1000%!

Re: Beware - transmission output shaft is not 5/8"!
 

A dremel tool with a sanding cylinder and 10 minutes will make a standard 21 tooth 5/8" bore sprocket fit. A 9th grade girl team member did ours last night.

Re: Beware - transmission output shaft is not 5/8"!
 

We decided to turn down the shaft, as that then gives us the ability to change sprockets easily, should we want a different gear ratio.

Re: Beware - transmission output shaft is not 5/8"!
 

AND we had to walk uphill both ways to get to our shops!
And we likesed it that way!

trying to keep it light hearted,
-Andy A.

Re: Beware - transmission output shaft is not 5/8"!
 

someone should make this a sticky at least for years with the transmission....it will save a lot of people time and anguish

Re: Beware - transmission output shaft is not 5/8"!
 

I am very grateful for the increadible advances that have come along to help teams. As one who has been there (since 2000) and walked uphill both ways, I know what you are talking about.

In those days, many, many robots barely moved - so great were the challenges in getting the drill motors mounted and coupled to a drive shaft and delivering power to the drive wheels. Now, rookie teams are able to build very compettive robots even if they have limited machining capabilities. Do keep in mind that there are teams out there who are trying to be competitive with nothing more than hand tools or perhaps a wood-shop band saw and drill press.

Thank you to those who suggested practical ways for us to use standard sprocketts - we'll probably try the dremel... that sounds pretty easy - we could do that.

Thanks!

-Mr. Van
Coach, 599

Re: Beware - transmission output shaft is not 5/8"!
 

Stick it in a drill or drill press(if available) and use sand paper on that, then it is an easy 5 minute project.

Re: Beware - transmission output shaft is not 5/8"!
 

Ah yes. The wonderful makeshift vertical lathe. We've done this a couple times to get things to fit. Just keep it limited to sandpaper and emory cloth. Another favorite improper use of tools is using a precision vice in place of an arbor press.

Re: Beware - transmission output shaft is not 5/8"!
 

This is pure genious by FIRST. They plant this seed of frustation in us over our outdated units of measure. It is part of their plan for global domination! (kidding, but it's not like I would mind :) )

Re: Beware - transmission output shaft is not 5/8"!
 

how easy would it be to extend the drive shaft output? our team is planning on using a six wheel drive but without using the skyway wheels. rather some modified off the shelf wheels. the problem is they are 2 inches wide at the widest point (the tread is only 1 inch) and the easiest way to line them up is to extend the output. any help?

Re: Beware - transmission output shaft is not 5/8"!
 

We just took one of our '05 KOP gearboxes apart. It is in great shape -- no visible signs of wear and no metal bits in the grease. We haven't touched them since building them during the second build week last year. The new ones are apparently just as bullet-proof, and is quieter to boot. I'm a HUGE fan.

Re: Beware - transmission output shaft is not 5/8"!
 

I dunno. When the UK used Imperial measures, they ruled history's largest empire. Now they use metric and are just a medium-sized European country. It gives you something to think about.

(We used a metric bit to fix the problem.)

Re: Beware - transmission output shaft is not 5/8"!
 

We got our 5/8" sprockets to fit by filing them out with a rat tailed file, it took about 10 minutes per sprocket.

Re: Beware - transmission output shaft is not 5/8"!
 

I figure I am the most qualified person in the FIRST community to talk about the transmission and why all choices were made. So here goes:

1. The 21 tooth sprockets supplied with the kit are supposed to mate with the transmission output shaft with no modifications. If this is not the case, then something is wrong and you should contact IFI or FIRST.

2. The transmission was designed as a result of FIRST listening to many people in the FIRST community regarding the importance of a functional drive train for all teams. FIRST, along with IFI and Dr. Flowers, asked JVN and I to help design a kit transmission and a kit gearbox for rookies and low budget teams to have a functioning, competitive drive base without any advanced machining capabilities.

3. 100% of my time was donated to FIRST for this activity which included concepting, design, detailed drawings, prototyping, and (important) the entire manual creation. If you read the manual, it mentions the 16mm output shaft in 10 different locations.

4. The only change made from last year to this year is the addition of mounting holes for the gear tooth sensor. IFI and FIRST may have chosen different suppliers than last year, but no design changes were made.

5. Metric is the World standard. There is no argument. When you get into industry you will probably deal with metric components. You must be what I call "metric bilingual". If I had my way, the entire transmission would be metric simply because I am an engineer that does all design work in metric. One of the terms I had for volunteering my time was being able to use metric where no significant cost to FIRST would be incurred.

6. For reason number 5 above, some things are still in the English system. The hex shafts are 3/8" and 3/4" for purely cost reasons. The fasteners are 1/4"-20 for commonality with the kit frame and for cost reasons.

7. Metric bearings outnumber English bearings by almost 2:1 in availability. My team bought a 16mm drill and reamer with a 5mm key way broach for less than $100. If your team can't afford that cost, then the kit transmission had you in mind ... use it as given to you.

8. The kit transmission will last you for multiple years. My team plans on re-using our gears on the competition bot this year just to prove this point.


The bottom line is that in week 1, at a regional with about 10 rookies (Finger Lakes) everyone was driving around and there were no spin in place robots to be found. This was a drastic improvement over the prior years. The kit transmission was (and still is) a huge success. If the 16mm shaft bothers you that much (it is 0.004" larger than 5/8"), then just machine your own transmission ... or keep quiet. I really have no more patience left for the complainers. Better yet, you do something; I mean really DO something; to help out FIRST and the rest of the FIRST community.

When you give more than you receive, then come talk to me about the kit transmission.

Sincerely,

Paul Copioli

Units of measure
 

Are we the only team doing all dimensioning in cubits?

Re: Beware - transmission output shaft is not 5/8"!
 

Try moving your wheels a bit on the axle shaft to see if you can get a clear chain path. See if moving the center wheels out a bit and bringing in the others helps, or something similar.

Re: Beware - transmission output shaft is not 5/8"!
 

Everyone take note of this statement.

How many people who used the kit transmission last season, took the time to thank Paul for all his hard work? (I did.)

It's never too late to say thank you.

Re: Beware - transmission output shaft is not 5/8"!
 

even though Team 25 does not make use of the kit transmission, I admire Paul a great deal

WHY?

cause he does crazy things like this (and he can bear hug me ) You may not like it but read his post, FIRST, has been evolving since 1992
its not just Inspiration and Recognition anymore, you have to throw a P in there for Preparation....

FIRST is preparing us for the real world, and in the real world you are going to encounter Metric and SAE, if you don't believe me, just ask Mr. Lavery

Thanks Paul, For all that you do

Re: Beware - transmission output shaft is not 5/8"!
 

Great idea John
Thanks Paul the Kit trans Rocks!!! We used it last year over our own design because we found it to be so good and reliable.
I suspect most teams who used it are greatful. It makes building a good driving competitive robot acesssable to many teams who have limited resources.

Ken

Re: Beware - transmission output shaft is not 5/8"!
 

We too used a Dremmel to modify purchased #35 chain sprockets to fit on the Metric shaft. We thought about taking the parts to the machine shop but, it was not difficult to make the adjustment with the help of a small file for key way.

I think the gearboxes as is are great. Thanks everyone who helped make them happen.

Re: Beware - transmission output shaft is not 5/8"!
 

It seems like no matter what you do to help people, someone will have a problem with it. I guess its to be expected. My company gave everyone gift cards for the grocery store at Thanksgiving, and people complained about it. "I don't shop there... Is that all they can give" etc. What fun people.

I think most people's frustration comes when trying to apply a sprocket of smaller than 21 tooth size to the output shaft. I think reaming/sanding etc. are fine for opening up a 5/8 sprocket, but people may have a tough time with the 5mm keyway.

Maybe someone should offer up a source for smaller sprockets that are "plug and play" with the transmissions. (I smell a new product for AndyMark...)

Anyway, My team is using the kit transmissions and kit frame again this year. It is no secret that using these last year allowed us to focus on mechanisms and was a huge factor in our success last year.

Good luck to all teams, whether you use the kit components or not!

Rob

Re: Beware - transmission output shaft is not 5/8"!
 

the thing about this is that it is easy to just change the sprockets on the wheels instead. Remember with gear ratios you can change either sprocket and have the same effect. If you look at this from a company standpoint i would rather sell new sprockets for the wheels (more volume) then a more specific product of a lesser quantity.

Re: Beware - transmission output shaft is not 5/8"!
 

Last year, we lapped out the sprockets with valve grinding compound on a drill press. We used a short length of old 5/8" shaft as a tool. Took forever, but the precision and fit was fantastic. This year, due to needing four sprockets, we uses emery paper to reduce the shafts. Since we are swapping sprockets at the last minute, this saved a lot of work.