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all terrain vehicle

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shanky25

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Hello

I am planning to build an all terrain vehicle. The features of the bot are as listed below

1) It should be able to climb all types of terrains and should react to sudden change in the elevation.

2) It should also be able to run on the surface of water.

what should be the specifications of the base, the dimensions of the wheels and how should the grip be designed?
 

dknguyen

Well-Known Member
Most Helpful Member
I spent a couple years running around looking at possible solutions. And here's what I learned:

-wheels won't work at all unless they have crazy suspension like the mars rover or a radio-controlled rock crawler truck
-even with that suspension, tracks will still beat the pants off of wheels but are hard to find and super expensive
-both tracks and super suspension wheels can barely make it up a set of stairs
-anything "innovative" won't work due to power requirements/weight/complexity/cost. That includes legs, whegs, hopping, snakes, and tow cables
-also trying to make it go over water means your project has an 100% chance of failing if you need to ask the questions that you just asked

So you can rule out any wheeled vehicle, even the ones with Mars rover or rock crawler suspension because they can't swim at all. You can also rule out hovercraft because they can't climb. The only real thing left is an amphibious tracked platform (like an amphibious tank). It will cost you $5k-$10k to get a REAL tracked platform which will also be heavy and very difficult to waterproof and make floating. It's actually much cheaper and easier to just build a plane or helicopter.

Trust me on what I say, I looked at EVERYTHING (including snake robots that could both swim and move on the ground).Stick with water or ground. Boats are actually much easier than all-terrain vehicles since all-terrain vehicles that can climb need very complex and expensive mechanics like suspension systems or tracks.
 
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shanky25

New Member
@ dknguyen

What if i want my bot to run on the water surface only. can i do it using a rock crawler truck wheels?
 

dknguyen

Well-Known Member
Most Helpful Member
THings that are made to climb very well on the ground tend to be too heavy and have too many moving parts to water proof or make float. If I were you, I'd make a boat.

Look very carefully before you leap. Don't make the same mistake I did. I have a $1000 worth of rock crawler setup in my basement that is abandoned right now because it costs another $2k or so to get the mechanics and drives done (although I suppose I could forego on the shiny metal wheel rims and driveshafts which would shave off $640). If you want, you can have it for a low low price of $500. lol
 
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shanky25

New Member
@ dknguyen

I actually wanted to build an all terrain vehicle for military application. So, obviously the size of the bot also matters a lot. I thought of making it around 25-30 cms high and 20 cms wide. Since the size is small I dont think the parts will be too heavy. Am I wright?
 

dknguyen

Well-Known Member
Most Helpful Member
The smallest rock crawlers and tracked platforms are twice as big as the size you are wanting. Anything ground vehicle of the size you are suggesting will not be able to climb effectively unless it's like a cat or dog or insect (that has legs to reach up, or can walk on walls or fly). They all weight between 10-20 kbs and were not made to float (think about getting a 10lbs rock to float- that's what you are trying to do).

If you really want something that size that can travel anywhere, use a little helicopter, either a regular single-rotor helicopter or a quadcopter. Think about it like this- the military has billions of dollars behind it and there they have no robot I know of that can both climb and swim. They have robots that can swim and robots that can climb, but not in the same robot.

THe closest thing you are asking for, is this:
http://www.robotmarketplace.com/products/ML-MMP30TWE.html
It's small (though larger than what you want), but cannot swim and is expensive.

THis one is cheaper:
http://www.superdroidrobots.com/shop/item.asp?itemid=920&catid=73

But this one has cool flipping arms:
http://www.superdroidrobots.com/shop/item.asp?itemid=864

There also some robots out there that can't swim, but they can drive underwater (the ones you can actually get your hands on cost around $2000 and have 4 wheels instead of tracks).
 
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shanky25

New Member
@ dknguyen

Can I use the above said principle for a terrain climber only? ie: If i dont want the bot to run on water?
 

dknguyen

Well-Known Member
Most Helpful Member
Which principle are you talking about? But yes, you can. THe smaller a robot is though,the harder it will be to climb things...unless you can get it to fly, stick to walls, jump, or reach up.
 
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shanky25

New Member
All wright ! Now that I have decided to build an all terrain. :D What kind of wheels do i need to use? I mean where do I get that sort of gripped wheels?
 

dknguyen

Well-Known Member
Most Helpful Member
YOu are sure you want to go with wheels instead of tracks? Tracks are more expensive ($2-4k for the smaller ones) but climb much better with fewer moving parts. Wheels are cheaper and easier to find but require a suspension system to climb anything (or require massive massive wheels).

The best wheels for climbing are the wheels they sell for hobby radio-controlled monster trucks and rock crawlers. THese can be tricky to connect to a motor shaft or a driveshaft. Suspension systems are not the kind of thing you can build yourself unless you know what you are doing (and if you ever looked at a car suspension system, you might realize how complicated it is just to mount the wheels). THe easiest and cheapest thing for you to do is to just buy a rock crawler kit:
http://www.axialracing.com/ftp/ax10/

EDIT: OH, look at that, the rock crawler I posted also happens to be the size you want.
 
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shanky25

New Member
@ dknguyen

Now while climbing a terrain what if the elevation suddenly changes? How will the bot manage to react quickly to the sudden change in the elevation?
 

shanky25

New Member
The elevation might not be 90 degrees. But assume a hill, the elevation seems to be same but it is nit actually constant. What should be the torque of the motors i use for the specified dimensions?
 

dknguyen

Well-Known Member
Most Helpful Member
The suspension on the rock crawler will smoothen out the uneven terrain just fine (you don't want to go over it too fast though, but rock crawlers are made for torque, not speed).

You would need to know the weight of the robot first. But RC motors (the easiest kind to find and the kind that best fits into rock crawlers) don't give torque ratings most of the time. Just choose the biggest slowest spinning motor with the most torque that can fit into the rock crawler and adjust the gear ratio until you get the balance of torque and speed that you want.

If you actually want to calculate it though:
http://www.electro-tech-online.com/threads/motor-sizing-for-moving-robots.23264/

WHere are you from?
 
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shanky25

New Member
@ dknguyen

I am from India. I have taken this as my engineering project. I am very much pleased by your answer. I may need your guidance throughout my project. Hope you help me.:)
 

dknguyen

Well-Known Member
Most Helpful Member
I'm not sure about the availability of RC rock crawlers in India. Is this just an engineering project? Or is it a school project? If it's for school, I don't know if you can just use a rock crawler kit.
 
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