Thanks for your replies, everyone, we really appreciate your help!
Here's a little more information to clarify a few things:
- We're wanting to use normal wheels (not a holonomic drive) and steering like on a car
- We had a mechanical engineer give a presentation to our club and he also recommended Ackermann steering, so we'll be trying to implement it somehow with a servo
- We'll be using a cRIO for the control system
- We estimated that the weight should be around 30lbs, but to be safe we should probably plan for twice that, or 60lbs
- If we end up using FIRST motors, then we'll probably get one of the standard batteries that FIRST robots use (12V motorcycle battery?), as long as that doesn't put us way over our weight limit
Quote:
Originally Posted by gpetilli
I have been working on a spreadsheet to help with motor and gearbox selection. It may be useful for you. The final speed calculations are optimistic, but relative results should be reasonable.
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Wow, that looks like it might be really helpful. Thank you!
Quote:
Originally Posted by stinglikeabee
Suggestions for motors are great and all, but may not be the best for the application. An FRC setup will most likely work for you, but I urge you to define the requirements.
What are the major areas of functionality and concern? These could be things such as maintainability, maneuverability, reliability, durability, etc. For each of the requirements, outline an objective (what you really desire) and a threshold (the minimum that you will accept). The space between the objective and the threshold is the trade space - you will use this to determine if your solution is workable.
Here are some of my first thoughts on requirements:
So far, I have two "requirements": 30lb weight and 6 mph. Do you have a maximum weight allowed? A minimum speed?
What acceleration is required? This will help define your motor HP and gearing/transmission requirement. It will also help define your electrical power requirement.
How will you get electrical power? Internal combustion engine with a generator-inverter setup? Battery? Fuel cell? Solar? This will help define motor power limits or operating time.
What is the vehicle operating time? How long will it be using full power? What other electrical loads are required?
What ground clearance is required? This will help define wheel diameter and relates to the HP and transmission requirement.
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Thanks for your help! Here's some more information:
- The weight we're shooting for is 30lbs (not sure how realistic this is..), so let's plan for up to 60lbs
- The maximum speed needs to be at least 4 mph, but we'd like it to go up to 6 mph
- I'm not sure on acceleration, but it's not a huge issue since speed isn't our primary concern
- We need it to be battery operated. What type of battery we use mainly depends on how much power the motors draw, so we don't know what battery we'll be using yet
- We'd like an operating time of at least 20 minutes of running non-stop, which would hopefully translate to at least 40 minutes of on and off use. Obviously a longer running time is preferred, though!
- We'll be using a cRIO as the control system and will have a couple of low power sensors and some kind of camera (possibly an Xbox Kinect)
- We need at least 2" of ground clearance, so we were planning on using 6" wheels
So far we've had these motors recommended:
- Banebot (possibly with a 4:1 or a 16:1 ratio)
- BAG motors with the versaPlanetary gearbox of 10:1 (but they might be bad, according to a few)
- miniCIM in a versa-planetary
Where do you all buy your parts from? Is there any particular place you recommend?