Dr. Joe - What is #47's Drive Ratio-Care to share?

[archiver]

Posted by Glenn M. Krcek at 1/26/2001 4:55 PM EST


Other on team #226, Manhatan Project, from Troy and Athens High and GM CRW.



Dear Dr. Joe, are you willing to divulge No. 47's gear ratio this year.
We are targeting latching onto both goals, and driving onto the bridge. We estimate weight to be around 290 lbs max. We've chosen 3:1 out of 2 drill motors and four wheel drive.
Since we all gain this year, in a sence, from performing well, maybe some deeper sharing won't hurt. It's sort of in the spirit of open computer systems and the Internet. I think it's ingenious and cool the way First is changing the game into more of a shared competition.
I believe the winners are all the contestants in USFIRST, not just the finalists.
I am anxious to hear tidbits of what you and other teams are really doing this year. Thanks for the sharing you've already done, such as the White Papers.
May the Force be With You.
GMk

[archiver]

Posted by Joe Johnson at 1/26/2001 9:18 PM EST


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


In Reply to: Dr. Joe - What is #47's Drive Ratio-Care to share?
Posted by Glenn M. Krcek on 1/26/2001 4:55 PM EST:



Hi Glenn,

As to sharing exact gear ratios, I am sorry that I am
going to have to pass.

Yes, this year more than ever, teams are sharing
things. But exact ratios are more of a trade secret
that I am not sure everyone should publish.

I have gone out of my way to give rookies guidance as
to the ranges they should be considering because
getting the ratio really wrong can ruin an otherwise
good year, but beyond that I am a little tight lipped.

I will say this, you don't give your wheel diameter,
but at 64 to 1 from the motor the output shafts in low
gear and another 3 to 1 on top of that, even with an 8
inch wheel you will not be setting any speed records
(unless of course you shift your transmissions which is
tricky but possible with good design and good
software). By the way, you will have something like
150 lbs available per motorized wheel at this ratio and
the 8 inch wheel. You will have a difficult time
getting that much tractiion on the carpet (imho).

Sorry for the non-answer. Good luck just the same.

Joe J.

[archiver]

Posted by Andy Baker at 1/27/2001 12:20 AM EST


Engineer on team #45, TechnoKats, from Kokomo High School and Delphi Automotive Systems.


In Reply to: Still a trade secret...
Posted by Joe Johnson on 1/26/2001 9:18 PM EST:




: but at 64 to 1 from the motor the output shafts in low
: gear and another 3 to 1 on top of that, even with an 8
: inch wheel you will not be setting any speed records
: (unless of course you shift your transmissions which is
: tricky but possible with good design and good
: software). By the way, you will have something like
: 150 lbs available per motorized wheel at this ratio and
: the 8 inch wheel. You will have a difficult time
: getting that much traction on the carpet (imho).

Unless, of course, they added tank treads.

That would definitely be a sight to see!

Andy B.

[archiver]

Posted by Glenn M. Krcek at 1/27/2001 9:15 AM EST


Other on team #226, Manhatan Project, from Troy and Athens High and GM CRW.


In Reply to: Still a trade secret...
Posted by Joe Johnson on 1/26/2001 9:18 PM EST:



:

:
:

:

: I will say this, you don't give your wheel diameter,
: but at 64 to 1 from the motor the output shafts in low
: gear and another 3 to 1 on top of that, even with an 8
: inch wheel you will not be setting any speed records
: (unless of course you shift your transmissions which is
: tricky but possible with good design and good
: software). By the way, you will have something like
: 150 lbs available per motorized wheel at this ratio and
: the 8 inch wheel. You will have a difficult time
: getting that much tractiion on the carpet (imho).

Dear Dr. Joe,
We've calc our approx top speed w/ the drill motors switched in the 64:1 position to be the following:
20000rpm /64=312.5 say 300 rpm
300 rpm / 3 = 100 rpm @ wheels
100 rpm x 8Pi (for 8"dia whls) = 2513"per min say 2500"
2500 / 12 = 208 ft/min approx
I am wondering if we blew it somewhere? I am thinking we have sufficient speed. We are concerned if we'll have sufficient traction, but addressing that with a special wheel design.
Thanks for the reply.
GMk

: Joe J.

[archiver]

Posted by Dodd Stacy at 1/27/2001 9:32 AM EST


Engineer on team #95, Lebanon Robotics Team, from Lebanon High School and CRREL/CREARE.


In Reply to: Re: Still a trade secret...
Posted by Glenn M. Krcek on 1/27/2001 9:15 AM EST:




: 2500 / 12 = 208 ft/min approx
: I am wondering if we blew it somewhere? I am thinking we have sufficient speed. We are concerned if we'll have sufficient traction, but addressing that with a special wheel design.
: Thanks for the reply.
: GMk

Glenn,

You're right in the sweet zone for this year's game, imho. Your drivers will be able to accurately place the bot, it will get where it's going soon enough, and you'll have good torque at the wheels for bridgework with a load. Now, about that carpet traction......

Good luck!

Dodd

[archiver]

Posted by Glenn M. Krcek at 1/27/2001 12:25 PM EST


Other on team #226, Manhatan Project, from Troy and Athens High and GM CRW.


In Reply to: Good To Go
Posted by Dodd Stacy on 1/27/2001 9:32 AM EST:



:
: : 2500 / 12 = 208 ft/min approx
: : I am wondering if we blew it somewhere? I am thinking we have sufficient speed. We are concerned if we'll have sufficient traction, but addressing that with a special wheel design.
: : Thanks for the reply.
: : GMk

: Glenn,

: You're right in the sweet zone for this year's game, imho. Your drivers will be able to accurately place the bot, it will get where it's going soon enough, and you'll have good torque at the wheels for bridgework with a load. Now, about that carpet traction......

: Good luck!

: Dodd
Yeah! That is going to be a good trick.
The trick is to make it stick, but how?
Thanks for the feedback.

[archiver]

Posted by Denny McBride at 1/28/2001 4:20 PM EST


Other on team #379, Robocats, from Girard High School.


In Reply to: Re: Good To Go
Posted by Glenn M. Krcek on 1/27/2001 12:25 PM EST:



: :
: : : 2500 / 12 = 208 ft/min approx
: : : I am wondering if we blew it somewhere? I am thinking we have sufficient speed. We are concerned if we'll have sufficient traction, but addressing that with a special wheel design.
: : : Thanks for the reply.
: : : GMk

: : Glenn,

: : You're right in the sweet zone for this year's game, imho. Your drivers will be able to accurately place the bot, it will get where it's going soon enough, and you'll have good torque at the wheels for bridgework with a load. Now, about that carpet traction......

: : Good luck!

: : Dodd
: Yeah! That is going to be a good trick.
: The trick is to make it stick, but how?
: Thanks for the feedback.

We have the traction but are not sure about the ratios. We are going with 3:1 on a 9.25 wheel. We are prepared to go to 3.5 or 4 to one if needed. Available torgue will be applied to 4 wheels. We will be testing next week.

[archiver]

Posted by Glenn M. Krcek at 1/27/2001 4:06 PM EST


Other on team #226, Manhatan Project, from Troy and Athens High and GM CRW.


In Reply to: Re: Still a trade secret...
Posted by Glenn M. Krcek on 1/27/2001 9:15 AM EST:



: :

: :
: :

: :

: : I will say this, you don't give your wheel diameter,
: : but at 64 to 1 from the motor the output shafts in low
: : gear and another 3 to 1 on top of that, even with an 8
: : inch wheel you will not be setting any speed records
: : (unless of course you shift your transmissions which is
: : tricky but possible with good design and good
: : software). By the way, you will have something like
: : 150 lbs available per motorized wheel at this ratio and
: : the 8 inch wheel. You will have a difficult time
: : getting that much tractiion on the carpet (imho).

: Dear Dr. Joe,
: We've calc our approx top speed w/ the drill motors switched in the 64:1 position to be the following:
: 20000rpm /64=312.5 say 300 rpm
: 300 rpm / 3 = 100 rpm @ wheels
: 100 rpm x 8Pi (for 8"dia whls) = 2513"per min say 2500"
: 2500 / 12 = 208 ft/min approx
: I am wondering if we blew it somewhere? I am thinking we have sufficient speed. We are concerned if we'll have sufficient traction, but addressing that with a special wheel design.
: Thanks for the reply.
: GMk

: : Joe J.

[archiver]

Posted by Joe Johnson at 1/28/2001 4:57 PM EST


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


In Reply to: Re: Still a trade secret...
Posted by Glenn M. Krcek on 1/27/2001 9:15 AM EST:



At top speed it will take you nearly 20 seconds to get
from a home position on one end of the field to the
other end of the field.

If this is acceptable, okay. But if you need to get
there back and there again, over half of the match is over.

Just asking.

Joe J.

[archiver]

Posted by Raul at 1/28/2001 8:47 PM EST


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


In Reply to: Re: Still a trade secret...
Posted by Glenn M. Krcek on 1/27/2001 9:15 AM EST:



OK, The spec in the official document says the top speed of the drill system is 400 RPM in low gear. Various sources say it is between 300 and 400 RPM. Does anyone know the true no-load RPM?

FYI - In all the past years our robot has had a "measured" top speed of between 5 and 7 ft/sec depending on what was most important to us for each year. For example, last year it took us 8 seconds to get across the field; not very quick, but we never had a problem with overheating our drive motors.

Raul

: : I will say this, you don't give your wheel diameter,
: : but at 64 to 1 from the motor the output shafts in low
: : gear and another 3 to 1 on top of that, even with an 8
: : inch wheel you will not be setting any speed records
: : (unless of course you shift your transmissions which is
: : tricky but possible with good design and good
: : software). By the way, you will have something like
: : 150 lbs available per motorized wheel at this ratio and
: : the 8 inch wheel. You will have a difficult time
: : getting that much tractiion on the carpet (imho).

: Dear Dr. Joe,
: We've calc our approx top speed w/ the drill motors switched in the 64:1 position to be the following:
: 20000rpm /64=312.5 say 300 rpm
: 300 rpm / 3 = 100 rpm @ wheels
: 100 rpm x 8Pi (for 8"dia whls) = 2513"per min say 2500"
: 2500 / 12 = 208 ft/min approx
: I am wondering if we blew it somewhere? I am thinking we have sufficient speed. We are concerned if we'll have sufficient traction, but addressing that with a special wheel design.
: Thanks for the reply.
: GMk

: : Joe J.

[archiver]

Posted by Lloyd Burns at 1/29/2001 12:40 AM EST


Other on team #188, Woburn Robotics, from Woburn Collegiate and Canada 3000, ScotiaBank, Royal Bank Financial.


In Reply to: Re: Still a trade secret...
Posted by Glenn M. Krcek on 1/27/2001 9:15 AM EST:



. We always found that the load of the transmission was enough to slow the 20000 RPM down at least some, even when not pulling the robot across the field.

: :

: :
: :

: :

: : I will say this, you don't give your wheel diameter,
: : but at 64 to 1 from the motor the output shafts in low
: : gear and another 3 to 1 on top of that, even with an 8
: : inch wheel you will not be setting any speed records
: : (unless of course you shift your transmissions which is
: : tricky but possible with good design and good
: : software). By the way, you will have something like
: : 150 lbs available per motorized wheel at this ratio and
: : the 8 inch wheel. You will have a difficult time
: : getting that much tractiion on the carpet (imho).

: Dear Dr. Joe,
: We've calc our approx top speed w/ the drill motors switched in the 64:1 position to be the following:
: 20000rpm /64=312.5 say 300 rpm
: 300 rpm / 3 = 100 rpm @ wheels
: 100 rpm x 8Pi (for 8"dia whls) = 2513"per min say 2500"
: 2500 / 12 = 208 ft/min approx
: I am wondering if we blew it somewhere? I am thinking we have sufficient speed. We are concerned if we'll have sufficient traction, but addressing that with a special wheel design.
: Thanks for the reply.
: GMk

: : Joe J.

[archiver]

Posted by Dan at 1/26/2001 9:30 PM EST


Other on team - from Carnegie Mellon sponsored by -.


In Reply to: Dr. Joe - What is #47's Drive Ratio-Care to share?
Posted by Glenn M. Krcek on 1/26/2001 4:55 PM EST:



:Since we all gain this year, in a sence, from
:performing well, maybe some deeper sharing won't
:hurt.

No, not really (at least in the competitive sense.) It's more likely that a team will be your opponent rather than ally at any given point. Then again, you're just trying to ease the Chief Delphi vaults open; a little grease can't hurt.
Dan