Thread: Problems with the stretcher?
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Unread 23-06-2002, 23:20
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#0047 (ChiefDelphi)
  
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Push or Pull?
Posted by Raul at 1/21/2001 12:09 PM EST


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


In Reply to: Re: Problems with the stretcher?
Posted by nick237 on 1/20/2001 11:08 PM EST:



I am not convinced that the robot will get better traction pulling the stretcher or goals over the bridge. With the proper design, you can get as much or more consistent traction when pushing.

Some factors to consider:
There is a transition from horizontal to sloped. This means if you are not careful in your design, you could either greatly reduce the normal force on the wheels nearest the strecher or lift them off the ground altogther. So, if you are relying on your rear wheels for traction when pulling the strecher, you better use momentum to get you through that transition.

Control issues:
It is much easier to control what you are hauling if you pull it. When you pull it,it is directionally stable. In other words the payload just follows you. But it does require a wide turn to make sure it it lined up straight behind you.
When you push, you have to direct its direction, which does take more effort in controlling. However, if you design it to grab the stretcher so it cannot jack-knife on you then, it is much easier to line it up with the bridge in a tight radius and control its direction. This becomes even easier if you use crab (aka swerve, aka omni-directional) steering on the wheels farthest from your payload.

Raul


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