Chief Delphi sprockets

Posted by Patrick Dingle at 03/04/2001 9:41 PM EST

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

Anyone on Chief Delphi want to give me a clue how you machine those nice big sprockets on your robot for the 1/4" and 3/8" chain? Very impressive!

Patrick

Posted by Jim Meyer at 03/05/2001 2:30 PM EST

Engineer on team #67, HOT Team, from Huron Valley Schools and GM Milford Proving Ground.

In Reply to: Chief Delphi sprockets
Posted by Patrick Dingle on 03/04/2001 9:41 PM EST:

I can’t speak for the Chief, but we machined 300 tooth 1/4 pitch sprokets from lexan for the HOT Bot last year. In case you don’t want to do the math, it’s around a 2 food diameter sprocket. Both the Marks Standard for Mechanical Engineers and the Machinists Handbook have tooth profiles for roller chain sprockets. If I remember correctly there are only 3 tangent circles that make the tooth profile. The rest is simply a loop rotate on a CNC mill.

A similar method can be used to make gear theeth but they have to a large pitch so you can use a reasonably sized endmill. You can machine smaller pitch gears by buying specially designed cutters.

Hope this helps,

Jim

Posted by Matt Berube at 03/06/2001 11:36 AM EST

Engineer on team #49, Delphi Knights, from Buena Vista High School and Delphi Automotive.

In Reply to: Chief Delphi sprockets
Posted by Patrick Dingle on 03/04/2001 9:41 PM EST:

: Anyone on Chief Delphi want to give me a clue how you machine those nice big sprockets on your robot for the 1/4" and 3/8" chain? Very impressive!

: Patrick

One trick we used this year we got from the Beatty/Hommond team.

If you don’t need more than ~270 degrees of rotation on the large sproket you really don’t need to make the teeth. Just wrap the chain around a disk and pin it to the disk in 1 location. The disk will rotate when the chain is moved until the pin location hits the tangent point on the chain.

Matt B.
T49
The “other” Delphi team

Posted by Michael Ciavaglia at 03/07/2001 8:43 AM EST

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

In Reply to: Chief Delphi sprockets
Posted by Patrick Dingle on 03/04/2001 9:41 PM EST:

Patrick,

Thanks for noticing our sprockets!

We were forced to wire burn 1/4" and 3/8" pitch sprockets. We bought the steel sprockets from SPI and continued accordingly (i.e. steel shafts & welding). I can’t remember exactly when we weighed CD6 but when we did we were about 138#. We had to go on a diet!!

That’s when we had to make the aluminum sprockets. The next problem was, how do we attach aluminum sprockets to steel shafts?

We took a hollow steel tube and plugged the ends. Then we took 1.5" dia steel, bored out the center and put a chamfer on the hole for the weld to go somewhere. Then we faced off the weld so the sprocket would mate flush to the slug. Finally, we drilled and tapped the steel so we could screw the aluminum sprocket to the shaft.

Initially I shyed away from this because of cost. However, I found a source that would produce them at a few dollars more than I could get sprockets from SPI.

Why did FIRST change the rule this year on sprockets, gears, and pulleys? I loved last year’s rule!!

Does anybody know why they changed the rule back?

Mike C.

Posted by Joe Johnson at 03/07/2001 9:58 AM EST

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

In Reply to: Wire Burned Sprockets
Posted by Michael Ciavaglia on 03/07/2001 8:43 AM EST:

Basically we wire EDMed aluminum sprockets for about $60 each that cost $40 each from Small Parts Inc.

Something is wrong when you can get a custom piece made for that close to the mass produced item.

Just my 2 cents.

Joe J.

Posted by Raul at 03/07/2001 1:59 PM EST

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

In Reply to: Wire EDM for 150% of SPI Cost!
Posted by Joe Johnson on 03/07/2001 9:58 AM EST:

Ouch!

I hope this does not make you feel bad - our shop charges $75/hr and we were able to get four 50-tooth sprockets for less than an hours work on a laser. But then the students clean up the parts by chamfering the edges on a sander and deburring on a wire wheel. Wire EDM is much more expensive (longer run time) than a laser for thin parts such as sprockets.

My advice is to tell your shop to leave it rough and that you will clean it up yourself. This will always save you a considerable amount of money an it allows the students to actually participate in the fabrication of most parts.

We attach (with screws) all sprockets to hub turned on a lathe.

Raul

Posted by JVN at 03/07/2001 3:02 PM EST

Student on team #250, Dynamos - Capital District Robotics Team, from Shenendehowa High School and General Electric and Verizon.

In Reply to: Re: Wire EDM for 150% of SPI Cost!
Posted by Raul on 03/07/2001 1:59 PM EST:

We use wire EDM’d gears, but to save money/machine time we have the students prep the stock for cutting, and do the finishing work.

Posted by Patrick Dingle at 03/07/2001 3:17 PM EST

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

In Reply to: Re: Wire EDM for 150% of SPI Cost!
Posted by Raul on 03/07/2001 1:59 PM EST:

Being involved in FIRST for three years and playing a major role on the design of our robot this year, I like to think that I know a lot about machining. However, the truth is I am a computer science major. Can someone explain what a “wire EDM” is, and how it works? Also, how does the laser technique work? Sounds interesting.

Thanks
Patrick

: Ouch!

: I hope this does not make you feel bad - our shop charges $75/hr and we were able to get four 50-tooth sprockets for less than an hours work on a laser. But then the students clean up the parts by chamfering the edges on a sander and deburring on a wire wheel. Wire EDM is much more expensive (longer run time) than a laser for thin parts such as sprockets.

: My advice is to tell your shop to leave it rough and that you will clean it up yourself. This will always save you a considerable amount of money an it allows the students to actually participate in the fabrication of most parts.

: We attach (with screws) all sprockets to hub turned on a lathe.

: Raul

Posted by Joe Johnson at 03/07/2001 3:43 PM EST

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

In Reply to: Re: Wire EDM for 150% of SPI Cost!
Posted by Patrick Dingle on 03/07/2001 3:17 PM EST:

EDM = Electo Discharge Machining (approx. words).

Basically, an electrode is used to make a spark. The spark “zaps” a bit of metal and a bit of the electrode (often made from carbon). With time, the electrode burns its way into the metal. A new electrode is used after the rough cut to make the hole look just like the electrode.

This machining technique has revolutionized injection molding (especially for plastic parts).

Enter Wire EDM.

Same idea, but the electrode is replaced by a wire running from a feeder on top to a collection spool on the bottom. This wire gets partially zapped as it “cuts” the metal, but it is not a problem because new wire is constantly feed to do the new cutting.

This vertical wire is walked around a horizontally mounted work piece in the pattern you want. Essentially, the wire is like a hot wire going through butter, only on a much slower scale.

If you add computers and servos to move the top and bottom wire points you can make very complex parts very easily (e.g. gears).

Wire EDM is wonderful.

Every FIRST team should have a source for this type of work. They are usually in small prototype shops. Go knock on their door and ask them for a coupon for next year’s build cycle.

Joe J.

Posted by Joe Johnson at 03/07/2001 3:30 PM EST

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

In Reply to: Re: Wire EDM for 150% of SPI Cost!
Posted by Raul on 03/07/2001 1:59 PM EST:

I am telling you, the sprockets and gears in SPI way out of line.

It is just silly to think that Martin Sprocket has all that high volume equipment cranking out sprockets like popcorn out of a carnival cart and I can go to a one off job shop and get substantially the same price as Small Parts Inc.

I don’t begrudge SPI their money, I just think that as a rule, FIRST has some serious thinking to do.

Let me explain. I have a bunch of sources for cheaply and quickly getting stuff made that I need. Others don’t. If I were in the “let’s all make this thing as fair as possible” crowd (which I am not by the way), I would be thinking hard about the fairness of the current situation.

Joe J.

Posted by Ed Sparks at 03/08/2001 3:12 PM EST

Engineer on team #34, The Rockets, from Bob Jones High / New Century High and DaimlerChrysler.

In Reply to: You make my point!
Posted by Joe Johnson on 03/07/2001 3:30 PM EST:

I have a theory …

I suspect (I repeat, suspect) that the problem of unlimited sprockets and gears has everything to do with the ablility of teams such as ours (we have both a Wire EDM and Laser in our shop) to develop an array of specialized gears and sprockets for use on future machines. I suppose teams with such an inventory would be able to rationalize these parts as “free” since they would be on the additional hardware list although they would not necessarily be “off the shelf”. As the rules are now, I must manufacture my gears and sprockets within the 6 week construction period for them to be legal. Secondly and regrettably, I suspect $MONEY$ is a factor here. Small Parts is clearly the beneficiary of the current rules as most of you do not have the equipment to manufacture these parts. My hat is off to Small Parts for being a major player for so long but I’ll bet my ‘bot that they get a benefit out of it (just look at my bill for this year – HEY how about a poll !).

I loved the way the pneumatics was handled this year. Since FIRST and SME are somewhat tight, maybe an ME organization such as SME and/or Boston Gear could supply a “Drivetrain Kit Of Parts” much like the pneumatics kit where some level of components are selectable (say 10 gears and/or sprockets).

I interpret FIRST’s rules as trying to keep the “spread” of super-teams vs rookies within some reasonable level to keep the game winnable by all. I’d love to go unlimited but I understand why we can’t.

Here comes my boss …

Ed now yields the soapbox to someone else …

Posted by Jason Rudolph at 03/08/2001 5:39 PM EST

Coach on team #459, Rampage, from University of Florida/Eastside High School and Adaptive Equipment.

In Reply to: My 2 cents and misc ramblings …
Posted by Ed Sparks on 03/08/2001 3:12 PM EST:

Well, I agree with you on some levels. But I do not agree that this evens out the spread between te “super teams” and the rest of us. This is how I see it…

Last year, if we needed a specific sprocket, or pulley, or gear or whatever, all I had to do was open up a catalog, find it, and buy it. This year, we can’t do that. However, teams that have access to these various machines, etc, can legally machine their own parts out of kit legal components. At the same time, since my team has no such access, we have to either compromise with something from SPI, IF it is even available, or just ditch the idea right off. Now, to me, this does not seem to be helping that spread, but hurting it.

Just my opinion,

Jason

Posted by Patrick Dingle at 03/08/2001 6:40 PM EST

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

In Reply to: Hurting, not helping
Posted by Jason Rudolph on 03/08/2001 5:39 PM EST:

I would not mind if they put sprockets & chain on the additional hardware list, however I do not want to eliminate the SPI sponsorship, since they GIVE each team $200 of free parts, and half off on the rest. This is a HUGE assistance to teams with tight budgets.

Patrick

: Well, I agree with you on some levels. But I do not agree that this evens out the spread between te “super teams” and the rest of us. This is how I see it…

: Last year, if we needed a specific sprocket, or pulley, or gear or whatever, all I had to do was open up a catalog, find it, and buy it. This year, we can’t do that. However, teams that have access to these various machines, etc, can legally machine their own parts out of kit legal components. At the same time, since my team has no such access, we have to either compromise with something from SPI, IF it is even available, or just ditch the idea right off. Now, to me, this does not seem to be helping that spread, but hurting it.

: Just my opinion,

: Jason

Posted by nick237 at 03/08/2001 8:15 PM EST

Engineer on team #237, sie h2o bots, from Watertown high school ct and sieman co.

In Reply to: Re: Hurting, not helping
Posted by Patrick Dingle on 03/08/2001 6:40 PM EST:

Patrick, Wake up and smell the gear oil.
We get nothing for nothing in this world and free parts and discounts from SPI is a total smoke screen.
You seem to forget the $5000.00 entry fee to a regional event for each team.
You forget that what you do buy from SPI has a value equal by weight to GOLD.
Two years ago SPI charged our team $17.00 for 20 feet of string at a regional.
We all pay, and through the nose with SPI. So dont think SPI or FIRST is doing you any favors, they are doing it for $$$$$$$$$
Disney also reeps their share of our event by overcharging for rooms and packaging park tickets to room rates. Also once in thier hotel system you have to pay their prices for any thing you need to buy as the stores and towns are miles away.
It costs $4000.00 per team to enter the Nationals, multiply this by the amount of teams going to Florida and your looking at a large chunk of change.
The fees to the nationals do not include hotels, air fares, food etc etc.
We the adults students and parents pay this, so dont be fooled… FREE HAHAHAHAHAHA.
NICK237

: I would not mind if they put sprockets & chain on the additional hardware list, however I do not want to eliminate the SPI sponsorship, since they GIVE each team $200 of free parts, and half off on the rest. This is a HUGE assistance to teams with tight budgets.

: Patrick

: : Well, I agree with you on some levels. But I do not agree that this evens out the spread between te “super teams” and the rest of us. This is how I see it…

: : Last year, if we needed a specific sprocket, or pulley, or gear or whatever, all I had to do was open up a catalog, find it, and buy it. This year, we can’t do that. However, teams that have access to these various machines, etc, can legally machine their own parts out of kit legal components. At the same time, since my team has no such access, we have to either compromise with something from SPI, IF it is even available, or just ditch the idea right off. Now, to me, this does not seem to be helping that spread, but hurting it.

: : Just my opinion,

: : Jason

Posted by Patrick Dingle at 03/08/2001 9:45 PM EST

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

In Reply to: Re: WHAT???..
Posted by nick237 on 03/08/2001 8:15 PM EST:

All I’m saying… for us, it is a LOT cheaper to purchase sprockets through SPI when they charge ONLY SHIPPING for them then when we purchase them through another catalog such as mcmaster carr.

That’s all i’m saying.

I agree with you, that if you buy a lot of stuff from small parts, then you are paying a lot. But even with the half price I think it’s less than through other catalogs.

Let me see if I understand you: You are saying it is cheaper to buy from other sources than buy from SPI with the $200 discount and 1/2 price on the rest? I have looked at other catalogs, and the cost from other catalogs is usually very comparable to the catalog price from SPI.

Now, obviously there is nothing for FREE. Well, there is $200 of parts for free. With this $200 our team purchased sprockets and chain for our drive system. We also purchased a small amount of other parts from the catalog. All in all, we spent about $400 catalog price, but we only ended up having to pay about $120 for all of it… ($400 - $200) / 2 + shipping = ~ $120. Had we ordered from another catalog the same parts, we would have had to pay around $300. Granted, SPI is still benefitting from our team, because the amount they charged us ($120) more than pays for how much it costs them to get the parts or manufacture them.

My point is: Who cares? We saved about $200 by ordering from Small Parts.

Obviously, SPI is in this for money, but who cares? It benefits both them and us.

Now, as I mentioned in my previous message, I see no reason why FIRST should prohibit all teams from purchasing sprockets and chains from other sources.

There are such things as business deals that benefit both sides.

Patrick

: Patrick, Wake up and smell the gear oil.
: We get nothing for nothing in this world and free parts and discounts from SPI is a total smoke screen.
: You seem to forget the $5000.00 entry fee to a regional event for each team.
: You forget that what you do buy from SPI has a value equal by weight to GOLD.
: Two years ago SPI charged our team $17.00 for 20 feet of string at a regional.
: We all pay, and through the nose with SPI. So dont think SPI or FIRST is doing you any favors, they are doing it for $$$$$$$$$
: Disney also reeps their share of our event by overcharging for rooms and packaging park tickets to room rates. Also once in thier hotel system you have to pay their prices for any thing you need to buy as the stores and towns are miles away.
: It costs $4000.00 per team to enter the Nationals, multiply this by the amount of teams going to Florida and your looking at a large chunk of change.
: The fees to the nationals do not include hotels, air fares, food etc etc.
: We the adults students and parents pay this, so dont be fooled… FREE HAHAHAHAHAHA.
: NICK237

:

: : I would not mind if they put sprockets & chain on the additional hardware list, however I do not want to eliminate the SPI sponsorship, since they GIVE each team $200 of free parts, and half off on the rest. This is a HUGE assistance to teams with tight budgets.

: : Patrick

: : : Well, I agree with you on some levels. But I do not agree that this evens out the spread between te “super teams” and the rest of us. This is how I see it…

: : : Last year, if we needed a specific sprocket, or pulley, or gear or whatever, all I had to do was open up a catalog, find it, and buy it. This year, we can’t do that. However, teams that have access to these various machines, etc, can legally machine their own parts out of kit legal components. At the same time, since my team has no such access, we have to either compromise with something from SPI, IF it is even available, or just ditch the idea right off. Now, to me, this does not seem to be helping that spread, but hurting it.

: : : Just my opinion,

: : : Jason

Posted by Jason Rudolph at 03/09/2001 3:47 PM EST

Coach on team #459, Rampage, from University of Florida/Eastside High School and Adaptive Equipment.

In Reply to: Re: WHAT???..
Posted by Patrick Dingle on 03/08/2001 9:45 PM EST:

Well, in our case, we found a local company to help us out. Now, this company can get us whatever materials we need from various companies, like McMaster. However, since they are constantly getting things from these companies, they pay for our shipping. So, really, it IS cheaper for us to get from another catalog. Plus, many other catalogs don’t run out of materials, or parts as SPI does. So, SPI does have it’s benefits for some teams, but is a hinderence to others. That’s what was ggreat about alst year. If SPI was a hinderence to you, you could buy from wherever you wanted. While at the same time, if it was easier for you to get it from SPI, you could, and it didn’t count against your allowable material on the robot.

Jason

Posted by Thomas A. Frank at 03/09/2001 4:53 PM EST

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

In Reply to: Re: WHAT???..
Posted by Patrick Dingle on 03/08/2001 9:45 PM EST:

: All I’m saying… for us, it is a LOT cheaper to purchase sprockets through SPI when they charge ONLY SHIPPING for them then when we purchase them through another catalog such as mcmaster carr.

Jason;

Assuming SPI has a size that mets your needs, and assuming it is in stock, you are probably right when looked at in a narrow way, but while I can see what you are saying, I think you might be missing the bigger picture.

Under last years rules, you could have gone over to your local bicycle shop and asked them to donate 20 feet of chain and some sprockets. I guarantee you would have gotten them (probably used, but who cares?), and they would really have been free (ignoring the thank you letters 34 cents postage).

I don’t have any problem with SPI doing this, and making money at it. That’s how our economic system is supposed to wrok. But with the freedom to engage in such a business, there exists a responsibility that requires that you be able to provide the goods/services required in a timely and cost effective manner. SPI is not always very good at this. Thus I think that FIRST needs to continue loosening the construction rules to make it easier for teams to utilize whatever they have on hand to build the machine.

It is hard enough getting volunteers to do this without annoying those who do give of their time with absurd rules that do not accomplish anything positive.

Everybody has access to a “junk bin” of some sort or other. The standard refrain I heard was “why can’t we just use this (fill in the blank) which is just sitting hear”. 'Cause that’s the rules (grumble, grumble).

Makes it tough to get people to volunteer for next year…

Tom Frank

Posted by Jason Rudolph at 03/09/2001 6:42 PM EST

Coach on team #459, Rampage, from University of Florida/Eastside High School and Adaptive Equipment.

In Reply to: Re: WHAT???..
Posted by Thomas A. Frank on 03/09/2001 4:53 PM EST:

um, I agree with you, it was Patrick who posted that.
Read my message above.

Jason

Posted by Thomas A. Frank at 03/12/2001 5:32 PM EST

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

In Reply to: Re: WHAT???..
Posted by Jason Rudolph on 03/09/2001 6:42 PM EST:

: um, I agree with you, it was Patrick who posted that.
: Read my message above.

: Jason

Posted by Patrick Dingle at 03/09/2001 6:58 PM EST

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

In Reply to: Re: WHAT???..
Posted by Thomas A. Frank on 03/09/2001 4:53 PM EST:

Yes, it is clearly me who you meant to address the message to. Until today, I was unaware that chains and sprockets had been on the additional hardware list… And as i’ve mentioned before, I see no reason why they shouldn’t. All I’m saying, is thank you to Small Parts for the discount they are providing, because it did help out our team.

Patrick

: : All I’m saying… for us, it is a LOT cheaper to purchase sprockets through SPI when they charge ONLY SHIPPING for them then when we purchase them through another catalog such as mcmaster carr.

: Jason;

: Assuming SPI has a size that mets your needs, and assuming it is in stock, you are probably right when looked at in a narrow way, but while I can see what you are saying, I think you might be missing the bigger picture.

: Under last years rules, you could have gone over to your local bicycle shop and asked them to donate 20 feet of chain and some sprockets. I guarantee you would have gotten them (probably used, but who cares?), and they would really have been free (ignoring the thank you letters 34 cents postage).

: I don’t have any problem with SPI doing this, and making money at it. That’s how our economic system is supposed to wrok. But with the freedom to engage in such a business, there exists a responsibility that requires that you be able to provide the goods/services required in a timely and cost effective manner. SPI is not always very good at this. Thus I think that FIRST needs to continue loosening the construction rules to make it easier for teams to utilize whatever they have on hand to build the machine.

: It is hard enough getting volunteers to do this without annoying those who do give of their time with absurd rules that do not accomplish anything positive.

: Everybody has access to a “junk bin” of some sort or other. The standard refrain I heard was “why can’t we just use this (fill in the blank) which is just sitting hear”. 'Cause that’s the rules (grumble, grumble).

: Makes it tough to get people to volunteer for next year…

: Tom Frank