Robot Base
 

Hello guys,
After successful rookie year to my team, I am looking for a simple base to next year robot.
I have some ideas for the base but I can't implement the all idea because it missing some solutions.
I thought of a 6/8 wheels drive base. the main wheels are lower than the other wheels by half centimeter.
The problem to implement it is that I don't want to use chains, it's an headache. But how otherwise I can connect the wheels to the motors.
I saw many sketch at Chief-Delphi but I haven't seen yet a solution to my idea.
If you have any ideas to make it work, I will be happy to hear about it.
Thanks,
Yarden

Re: Robot Base
 

You could do:
-Timing belts
-V-Belts
-Lots of idler gears
-Friction drive through and idler wheel
-Use 1 motor+transmission on each wheel in 6wd (4 cims + 2 fisher price)
-Drive shafts + bevel/helical gears
-4-bar linkage between the wheels (think locomotive)

Just a couple ideas, I'm sure some are better than others.

Re: Robot Base
 

You can use timing belts instead of chains in your drive train.

As an example, I've attached a photo of our robot for Breakaway.

Re: Robot Base
 

What sort of problems have you run into with chains? I know in the last couple years I have never had a problem with a properly tensioned chain and am very curious what sort of problems can arise.

As for a possible solution. http://www.chiefdelphi.com/media/photos/26312 Expensive, heavy, but no chain.

Re: Robot Base
 

because unknown reason after a while the chains are longer than they were and not always the chains fit ecsactly, if you remove one link it is too much short, if you add one link it is too much long and some times half a ling is not helping.
I liked the idea of timing belts but where can I get it and its sprockets?

Re: Robot Base
 

Gates provides some in the KOP.

There are also a number of ways to tension chain. One of the favorite ways is to get a cylindrical block of delrin and mount it by the ends, using an off-center screw or bolt. Rotate to tension the chain.

Re: Robot Base
 

What you need is a good chain tensioner design. Depending on what size chain you use (#25 or #35) will dictate how good your tensioner needs to be. Generally 35 chain is more forgiving if you have some slack, 25 is less so.

If you still want to move away from chain, AndyMark has a product they're working on that doesn't require chain. It may give you some ideas.

http://www.facebook.com/photo.php?pi...d=183701158229
http://www.facebook.com/photo.php?pi...d=183701158229

Re: Robot Base
 

To rehash a very over-discussed topic.....I never quite understand the desire to eliminate chains. They are one of the simplest, most economical, and most proven and reliable drive methods available. Properly assembled, they provide flexible shaft locations, adjustable length, easy repair, readily available sprockets and components, and guaranteed non-slip service. How many trillions of reliable bicycle-hours have run on roller chains? I suspect most of the "troubles" teams experience with chains are due to improper allignement, tensioning, or other implementation errors. Learning to use them well is often easier, and cheaper, than switching to a more exotic drive method.

Re: Robot Base
 

^+1

Re: Robot Base
 

QFT, by the way if you have a hard time aligning chains and getting them to work, forget about exotic drives, especially belt systems.

Re: Robot Base
 

Do anyone one if andymark idea is going to be sold in their shop?
The idea is very smart and helps to solove my problem.

Re: Robot Base
 

They stated that they are going to start selling those tubes by the start of June or something... so i guess yes... they cost 295$ or something so i don't think that it is worth it since there are some better and cheaper methods...

Re: Robot Base
 

For some teams that may be a very good option since a lot of teams in FIRST uses the AM transmissions where each of them cost more than $300. If teams who don't have a machine-shop have access to these components, it would make their life much easier leading them to concentrate on their manipulator. I would also be interested in your "better and cheaper" methods considering time and labor. Please post your viable methods. Thank you.

Re: Robot Base
 

First of all you get 2 Toughboxes in the KoP so it is no biggies to build a tank drive from 4 to even 10 or more wheels without much cost.... what is called kitbot...
Other methods are if you have a good sponsor or supplier that can get you some good gear components for free or cheap. For example one of our mentors this year was able to get us some planetary gears for the drivetrain for free so it is better and cheaper...

In my opinion this "tube" wouldn't be much helpful and cheaper for teams because one will cost 295$, you need 2 on the robot so it is more then 600$ with the shipping, and don't forget that you need different chassis for those "tubes" so it will cost more and it can easily get to 700 or even 800$ just the drivetrain, and it is without wheels... and the 2 wheels cost 295$... go figure how much the other configurations gonna cost....
Toughbox costs 88$ so even if you want to go with mecanum and all 4 gearboxes are toughboxes then it is still cheaper since you get the chassis and 2 gearboxes in the KoP and all you have to buy is the mecanum wheels and 2 toughboxes that cost 176$ excluding the wheels

Re: Robot Base
 

I still don't understand your "better and cheaper" solution. I have used tubes for the last 4 seasons and NEVER had any problems with it. Also, two 2 speed transmission from AndyMark is 360x2 = 720 bucks. The "tubes" are still cheaper (but yes it of course depends on the game in order for a team to decide what kind of drive train they would want to use).

Seems like we are taking over this thread. If you would like to continue this discussion, feel free to pm me.

Re: Robot Base
 

I got an idea to build my base but I have some questions.
How do I put a wheel directly to the gearbox(KoP gearbox).
And how do I put a wheel that is assembled just on one side of a screw?

Re: Robot Base
 

How do I put a wheel directly to the gearbox(KoP gearbox).

To my knowledge you can't, not without buying hex shafts and bearings (not cheap) and basically ditching the kit chassis. also the gear reduction would be WAY to low. I think there is typically something in the range of a 3:1 reduction done with sprockets after the gearbox usually.

And how do I put a wheel that is assembled just on one side of a screw?

With a screw, again it is challenging. The kit bot just isn't made to do this. Someone who has actually done this should elaborate on this not me.

Re: Robot Base
 

I saw many robot with it and I want to know what shaft or hex I need.

Re: Robot Base
 

I really really like these
http://www.andymark.biz/am-0114.html

you assemble them with these shafts and bearings
http://www.andymark.biz/am-0520.html
http://www.andymark.biz/am-0279.html

each box takes 2 bearings and with a 4 inch wheel can be direct driven and shift on the fly from high to low gear with pneumatics.

Re: Robot Base
 

You can put THIS on each wheel and then with a machine key you can put the wheels directly on the output shaft of the toughbox.
The problem is that in most cases you need support on the other side of the shaft in order that it won't get bend, so it will be wiser to get a longer shaft and put a bearing on the end of it, with the bearing inside the chassis and supported.
If you decide to go with hex shaft the you need hex bearing to the end, but not hex bearing on the wheel since you don't really need bearings on the wheels because they are direct driven and putting a bearing will lose it's point so THIS will work with a hex shaft.

If you need further help you can contact me in mail ygutman1@gmail.com, i am also from Israel so i probably will be able to help me more then some posts in here...

Re: Robot Base
 

Ya, forgot to mention insert for the wheel itself. I would suggest staying away from key ways, they sheer occasionally.

Re: Robot Base
 

I've been using key ways for 2 years now and my team have been using them for 4 years (since the team was founded) and we never had any problem with them, so i don't using them. But it is his choice to make since it is his bot. there are much more methods then hex or key... Those are just the two that andymark sells...

Re: Robot Base
 

our team has always used keys, we never shear them, but we loose them, all the time. however we dont want to buy a hex broaching kit. if possible use a hex broach, but keys work just as well. something i would look at is staying away from gearboxes all together, jester-drive uses only belts to gain gear reduction. picture here. http://www.chiefdelphi.com/media/img...09401a44_l.jpg

Re: Robot Base
 

When we stalled a motor, (electrical hooked them up backwards) we sheared a key, We also have had issues with losing keys, they are tiny little things....


What other methods are there? Friction mounts really aren't viable due to costs/vs reliability, and they are really more used to couple shafts.


Also we never have had to broach anything while using hex shafts, we just use the bearings and andymark mounts. Because they are circular anyone with a mill can easily mount them to a bot.