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Subject: 
Re: Newbie needs Help
Newsgroups: 
lugnet.robotics
Date: 
Mon, 5 Jun 2006 18:35:46 GMT
Viewed: 
3385 times
  
On Mon, June 5, 2006 12:47 pm, raj wrote:
One major key to making a good Tug-of-War robot will be making it go the
"right"speed.

- the wheels do keep spinning when the robot is held in place
- weight limit is imposed indirectly by being limited to one set of 9794

Problems/questions:
- even after 'loading' the robot with the entire set (IR tower too!), there
   is insufficient weight for the torque available. No way around this is
   there?
- roughly at what gearing ratio are you at risk of breaking gears and axles?
   FLL literature mentions 125:1 as probably too much. What would be 'extreme'
   and still safe?

I suspect you're far from breaking gears or axles.  However, keep in mind it is
always possible (so don't blame me if it happens)  :)  Keep the distance between
gears & wheels small, so the axles don't twist.

Sounds like you still have more torque that you are using.  (the wheels are
spinning)  So, you don't need to gear it down anymore.  That will just give you MORE
torque.

You can (A) add more weight (B) make it go faster, or (C) add more traction.
Considering you're already at the weight limit (out of parts), option (A) is out.

Making it go faster is a reasonable option.  Geared down 5:1 should still work,
depending on the wheels.

Adding more traction would mean using more wheels.  It's likely you're out of
wheels, because there are only 3 wheels in a couple types in the RIS kit.  So,
you're best option would be to increase the speed.

Also, it sounds like you can really start doing some testing.  Use some string or
something, and have the robot drag books across the table.  See how changing things
will make a difference in the weight of the books it can move.

Finally, remember, you can mechanically connect all the motors together, so they are
driving the same wheels.  This assures all wheels are getting the maximum amount of
power.

BTW, don't use tank treads.

Steve



Message has 2 Replies:
  Re: Newbie needs Help
 
Steve Hassenplug wrote: > You can (A) add more weight (B) make it go faster, or (C) add more traction. > Considering you're already at the weight limit (out of parts), option (A) is out. > > Making it go faster is a reasonable option. Geared down (...) (18 years ago, 5-Jun-06, to lugnet.robotics)
  Re: Newbie needs Help
 
(...) Steve, Philo's page on 'Wheels, Tyres & Traction' seems to imply that increased speed will not make much of a difference or am I reading that wrong? By 'mechanically connect' do you mean by using two differentials? The maximum 'safe' gearing (...) (18 years ago, 6-Jun-06, to lugnet.robotics)

Message is in Reply To:
  Re: Newbie needs Help
 
(...) Steve, Thanks for the tips and good wishes. Currently this is what we have: - 3 wheels driven by 3 motors. Each geared down at 15:1 - the wheels do keep spinning when the robot is held in place - very generous size limit, a 250mm cube - so no (...) (18 years ago, 5-Jun-06, to lugnet.robotics)

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