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FotoPlasma
04-16-2003, 03:24 PM
I've been hearing a lot of people (relatively) bad-mouthing the FIRST gearbox (the injection-molded, 90degree, gear enclosure), and I just thought I'd make a thread about it, seeing as how I don't particularly want to drive another thread (http://www.chiefdelphi.com/forums/showthread.php?s=&threadid=20081) any farther off-topic than it already is.

As for the FIRST gearbox, there were actually 6 different gear ratios commonly possible. Teams were given two each of 1" and 2" helical gears, which were able to mate at right angles to one another, and could have been swapped, inside of the gearbox itself, to provide either a 2:1 ratio or a 1:2 ratio. You could also order two 1.5" helical gears, for a 1:1 ratio, very easilly, from McMaster-Carr (I'm looking at the catalog page, right now (page 940, on their website)). This combined with the dual speed drill motor transmission allowed for a lot of variability on the part of teams who opt to take advantage of the FIRST gearbox.

I thought the entire gearbox system was great, personally, but sadly, I was one of a small group to be able to hear a small lecture, from Ron Rioux, about the design and fabrication process of the FIRST gearboxes, so perhaps I just have more appreciation for what went into it.

I hope FIRST releases a whitepaper, or another kind of description of how the design and fabrication process actually went. I'm almost sure it would amaze most of you. I just don't think anyone should berate FIRST for the effort they put into such a system, for nothing but the benefit of teams.

No replies necessary, I just wanted to get this posted somewhere for people to read...

slight spelling

marlon_jbt
04-16-2003, 03:29 PM
Although a great design, and I'm happy that FIRST brought it to all of us, and to the rookie teams... (Although I did not see many rookie teams use them)

It's not really meant for the battles that come upon the playing field. We used the plastic gearboxes this year, and we have had trouble with them...

Our first gearbox lasted us only half of the Pittsburgh Regional, and the second gearbox is still on there, but it amazingly lasted through the Great Lakes Regional, and it's cracked again, on its way back home. Luckily, we have replacement parts.

Vu2000
04-16-2003, 03:38 PM
If you're talking about the exploded gearbox picture they gave to us with the plastic pillow blocks we used them but not for the drive train. We actually used it for our arm that would moved back and fouth on a pivot on the front of our robot. It went probably a total of 180 degrees, 135 degrees up and it would lay flat on our robot in order to go under the bar and about 45 degrees down. We made the arm about 24 x 30, and in theory it could pick up boxes because we cut it in a shape in order it to pick up one box. The gearbox ratio we put in it was 250:1 in order to lift the aluminum arm, We had 3-5:1's and 1-2:1's. The chiaphua motor was used and we were actually surprised that the drive train people didn't use them just because we didn't have proper housing for them. But overall the gearbox was actually the most reliable thing on our robot, and never ever broke down, probably because we hardly ever used it, because we had every single trouble you can think of with our drill motor transmissions after every single match, but yeah the gearbox was reliable.

gburlison
04-16-2003, 04:04 PM
We purchased two more for a total of four on the robot. They were used in series to produce 4:1 reduction. Quick and easy design, but heavy and took up to much space. I believe that a white paper on the design process for the gearbox would be an invaluable learning tool for the newer team.

Bill Gold
04-16-2003, 05:49 PM
Originally posted by Duke 13370
Don't defend the drive train FIRST supplied us with, we're a 4th year team with decent facilities and financing, and we didn't move well till the second day of the second regional. If FIRST wants to even it out a bit, give us gear sets for 4 motor drives made out of metal; the one this year was weak (both in power and in construction).

http://www.chiefdelphi.com/forums/showthread.php?s=&postid=160728#post160728
You, sir, obviously donít know a single thing about how those easy to assemble drive train pieces became kit parts. At the Sacramento Regional I had the privilege of working with Ron Rioux from FIRST. During the course of the regional he explained the long, drawn out, exorbitant process in which those kits were engineered and fabricated. I donít remember everything, but I do remember that special molds in the range of $100,000 had to be machinedout of steel so that they would survive the injection molding process. Also, FIRST and Nypro didnít decide to get these pieces done for the kits until late summer. This information in and of itself is awing. So, Duke 13370, please stop insulting people for trying to help teams.

Adam Y.
04-16-2003, 06:25 PM
I personally like the gearboxes but hated the way you had to assemble them. Next year if our team goes with the supplied gearboxes we are using clamp on shaft collars so the shafts do not become marred and so it is easy to assemble and disassemble.

MisterX
04-16-2003, 06:35 PM
For those that remember us , team 521 L33T CREW, from UTC ( we were the team that would have seizure like movements on the field and had to use the joystick diagonally to go in the somewhat right way) are whole problem was with the gear boxs and trying to get the ratios between the two motors the same!!! Never year we are definatly going to get rid of the prefab and build are own custom ones like we have before

Adam Y.
04-16-2003, 06:46 PM
For those that remember us , team 521 L33T CREW, from UTC ( we were the team that would have seizure like movements on the field and had to use the joystick diagonally to go in the somewhat right way) are whole problem was with the gear boxs and trying to get the ratios between the two motors the same!!! Never year we are definatly going to get rid of the prefab and build are own custom ones like we have before
Our team had problems steering too. While I can't think of a reason that it was the gearbox but here are all the theories I could think of:
a)the drill motors are timed the same-What this means is that the drills will turn faster in one direction and slower the other way. This means if you have one motor wired differntly from the other your robot will have a tendancy to go off in one direction.:)
b)Spacing of wheels- Our wheels were really close together which is not a good thing. Thie closer the wheels the harder to steer.
c)Programming- Meh we had no time to fix it in programming.

sanddrag
04-16-2003, 07:17 PM
Originally posted by wysiswyg
b)Spacing of wheels- Our wheels were really close together which is not a good thing. Thie closer the wheels the harder to steer. Closer which way? What makes skid steering work better is having a short wheelbase and a wide track.

sanddrag
04-16-2003, 07:19 PM
We didn't use the gearbox or helical gears but we did use the aluminum pillow blocks; drill motors, gearboxes, mounts and couplers; and the Chiaphua motors and couplers with much success.

MisterX
04-16-2003, 09:08 PM
a)the drill motors are timed the same-What this means is that the drills will turn faster in one direction and slower the other way. This means if you have one motor wired differntly from the other your robot will have a tendancy to go off in one direction.


Yes that is true, however just as important was the fact that we were unable to get a good contact between the gear box and the motor due to positioning resulting in lots of sliping and grinding

Adam Y.
04-17-2003, 08:10 AM
Yes that is true, however just as important was the fact that we were unable to get a good contact between the gear box and the motor due to positioning resulting in lots of sliping and grinding
Did you use those couples that first provided? They worked fairly well.

MisterX
04-17-2003, 09:06 AM
Yes, we did however to get the box to fit we did need to manipulate it a bit ( so I guess it isn't ALL the boxes fault) and had to use it basiclly backwards so the cuplant was on the opposite side and we needed to extend further in order to get to it resulting in the poor connection.