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Our Team Needs Help on the Drive!
Okay, today our team decided on a drive for, what is to be our chaise drive train. the layout looks like:
|\-------/| |-|-----|-| Front |o|---- |o| |--|----|--| |--\___/--| |oo-----oo| Back ________ (This is not to scale, the little - just is a space, so ignore them)) Okay the circles are the wheels, the back four wheels in the back will be powered on a chain, and the front two wheels will be none powered and will be held in a straight position, not free on a caster mechanism. Before our team dives into creating this, I was hoping for some feed back, this is essentially 2 back wheel tank drive. So here are my questions? 1) What advantages do you see with this drive? 2) Should the front and back wheels be powered or just the back ones? 3) is there a thread, or some specifics to way a tank drive is bad for this competition? 4) With the layout above, where would you put the wheels, which ones would be powered, and what kind of drive would you recommend for this base layout? TY so much to all who respond, are team is rly in a fix on this, and can't rly decide, and answering these questions, would help us SOOO much, ty again! :) |
Re: Our Team Needs Help on the Drive!
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2) All wheels should be powered. If you don't, your available power drops. Worse, if you're turning, the front wheels are pure resistance. With the back wheels not having a lot of traction, you're going to have lousy turning capability. 4) Experiment! 3) I think there is, but I can't remember where it is. |
Re: Our Team Needs Help on the Drive!
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2. You need to power every wheel touching the ground this year. Depending on how your weight is displaced, you will be giving up tons of traction by not powering wheels. For example if you have around 20% of your weight over the middle of the bot, you could be losing upwards of 20% of your traction, which is a lot in this game. 3.Ill tell you right now why. The latteral coefficient of friction is nearly twice that of the normal CoF. |
Re: Our Team Needs Help on the Drive!
well what is the big gap in the front of the bot going to be used for? the idea looks good but if your are going to put wheels near the front y not the very front of the bot not as far back that is the only thing that i think might help some. and i dont think you need all wheels dive with four or two M. if one slips and one of the others grip it may make the bot jolt to one side. i think they might got the right idea here. 2M/2wheel drive hmm . and resistance is kinda what you need in this game.
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Re: Our Team Needs Help on the Drive!
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5) How would you then get power to the 2 front wheels? 6) Is there another way to model this layout to have that U cutout, but still have a set of front wheels, that are powered? 7) Still not sure as to what drive our team should consider |
Re: Our Team Needs Help on the Drive!
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Re: Our Team Needs Help on the Drive!
Coming from a guy who lives in Wisconsin and see's his fair share of icy roads (dug someone out of a ditch the other night at 2 am in fact), I can tell you that you don't want to do rear wheel drive.
There is also no advantage to doing dual rear wheels. More wheels does not equate to more traction. ^^^ That phrase may just have surpassed "Water game!" as most popular words to be uttered in the past year. |
Re: Our Team Needs Help on the Drive!
Since I can't refresh this thread, and don't want to start a new one, I am going to re-post the questions I still have, ty to all those who replied to the above questions, when answering just refer to the numbers below not the ones earlier in the post.
Questions: 1) What are the advantages/ disadvantages do you see with this drive? (be honest no hard feelings if it is all disadvantages) 2) With the layout above, where would you put the wheels, which ones would be powered with this base layout? 3) How would you then get power to the 2 front wheels? 4) Is there another way to model this layout to have that U cutout, but still have a set of front wheels, that are powered? 5) What drive train would be best for this layout? (ie: tank, swerve, omni, crab ect...)Any specific reasons to why, would be helpful. ty again to any who respond. |
Re: Our Team Needs Help on the Drive!
1. The disadvantages of this design are that the front wheels are not powered. You are going to want to power anything touching the ground. Also two wheels in the back provides you with nothing if not hurting you, if you are trying to increase the surface area you are only decreasing the amount of pressure over the surface area.
2. try to get the wheels as far into the corners as possible and power all of them. 3. Power to the front can be achieved either by running chains from you gear boxes or by having gearboxes on each wheel. 4. you might want to consider driving a wide robot instead of a long robot. |
Re: Our Team Needs Help on the Drive!
I would first stop thinking about half the robot. You will need to think about the trailer joined to the robot. It doesn't matter much what your half a robot can do. It will matter a lot how your complete robot (w/trailer) behaves on the regolith.
The two halves of the robot pivot horizontally on the trailer hinge pin. Study this carefully. You are friction limited. The force available to move forward or backward or change orientation depends only on the Normal force (weight) on your driven wheels. You've decided on an 8 wheel vehicle (2 on the trailer). You should have an explanation of why need each and every one of them. The 6 wheel drive you illustrate may not even be able to turn with normal wheels on carpet. It depends where the center of gravity is. Until you are prepared to do the math and physics, your best bet is to stick with the wide kit bot configuration and drive both wheels on each side. The longer wheelbase is your friend. You may want to buy another pair of wheels and build at least a dummy trailer that you can test with. The last thing you want this year is a toaster that doesn't move because it will end up being a scoring disaster. I would suggest that you get a simple and reliable drive working so that your drivers can practice while you work on mechanisms and software. Don't bite off more than can chew. Good Luck! |
Re: Our Team Needs Help on the Drive!
My team (as of the last meeting) is considering a drivetrain similar to this...
___.........___ |==\....../==| |....|.....|....| |[]...........[]| |[]...........[]| |................| |................| |==.........==| The == are non powered horizontal wheels that don't normally touch the ground. They are only there to keep the chassis from hitting the ground during impacts and abrupt stops. The [] are powered wheels. This is essentially just a 4WD, but the wheels are as close together as possible for better turning. They are slightly towards the front because that is where the majority of our weight is expected to be. That way we keep as much weight directly over the wheels as possible. It also helps balance things, so it has as little rock back as possible. This (or something like it) may be a good fit for what your team is trying to do as well. |
Re: Our Team Needs Help on the Drive!
And we're thinking of something like:
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__ __Of course, building in the wide direction does present other challenges, but also presents other opportunities. We've never built a "wide" robot before, but this year's game has inspried us to try something new. Jason P.S. It is the code tag "#" on your editor window that lets you do ASCII art a bit more easily. |
Re: Our Team Needs Help on the Drive!
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Re: Our Team Needs Help on the Drive!
It doesn't seem that anyone has directly answered your new questions so I will try
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An interesting strategy with this (Although of questionable legality) would be to spin another robot into the wall using your superior turning ability effectively locking them in place. |
Re: Our Team Needs Help on the Drive!
While everyone is thinking about weight distribution, don't forget the tongue weight of the trailer.
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