View Single Post
  #36   Spotlight this post!  
Unread 05-05-2005, 00:57
BrianBSL BrianBSL is offline
Registered User
FRC #0190
 
Join Date: Sep 2004
Rookie Year: 2000
Location: Worcester, MA
Posts: 251
BrianBSL has much to be proud ofBrianBSL has much to be proud ofBrianBSL has much to be proud ofBrianBSL has much to be proud ofBrianBSL has much to be proud ofBrianBSL has much to be proud ofBrianBSL has much to be proud ofBrianBSL has much to be proud ofBrianBSL has much to be proud ofBrianBSL has much to be proud of
Re: pic: Jester Drive:Mecanum Wheel Drive Train

Quote:
Originally Posted by EricH
BEFORE you commit to doing the mechanum drive, be sure you know what will happen and have a backup plan. We almost did it, but we decided that our design, which is closer to 190's than 357's, did not meet our requirements, so we are currently getting ready (very slowly) to try the next stage of design. The problems observed both on ours and 357's: a) lack of pushing power, and b) slow sideways motion. Both problems may be fixed in later editions and/or by other teams. So, test now, and if you decide to do it, good luck!
We didn't have a huge issue with lack of pushing power, although we rarely got into pushing matches because of the maneuverability it gives you (unless they have you pinned up against something you can almost always get out by going sideways. As far as sideways speed, because our drive was field oriented (pushing the joystick moved the robot in the direction you pushed the joystick, not in the direction relative to the front of the robot), we actually limited our forward speed to equal the speed we could move sideways. That way going full speed, you can move along a vector while spinning without it looking like you changed speed at all. I suppose that we could have added a "turbo" button to allow you to go full speed when you were moving forwards, but we never really had an issue with speed. In fact, we actually decided that we needed to gear it down a bit for our demo season as it is too fast for the average elementary/middle schooler who drives it during one of our demos.

As far as making them, it was quite a task to take on. We didn't know that there would be 4 identical motors in the kit this year (a requirement for this type of drive), so we had no plans on how to do it until after our 1 week of planning. We spent nearly 4 weeks actually manufacturing the wheels including making the molds and casting the molds (casting them was quite the learning experience). There is no affordable source to buy them that we found - in fact it would probably be cheaper to draw up prints and have a machine shop make the parts. The couple places we found that sell them are all custom runs in the thousands of dollar range for a set (which would blow you way out of budget as far as the $3500 limit). The most expensive part is the labor - especially in machining a hub like 357's uses.