Drive System/Frame questions

[Grim Tuesday]

So, My team, has in the past, made a fully custom frame out of T-Slot and 1" Square tubing, with supershifters, and tank treads. This ends up quite heavy, taking up a significant amount of our weight budget.

So, I was looking into doing a Kitbot on Steroids style frame, with some modifications. How much will this end up weighing, about? Both including gearboxes, and excluding them.

The other thing we were looking at was the NanoTubes frame. It seems to have a multitude of problems (center wheel not driven)
Whats the weight situation with these? Any teams with experience of these?

What do you guys think? Any other easy to use/build drive systems available?

[Andrew Schreiber]

You know the Nano Tube you linked has the center wheel driven off of a series of spur gears right?

http://www.andymark.com/product-p/am-0689.htm May be of slightly more interest to you since it uses chain instead and is cheaper.

[Hawiian Cadder]

The kitbot weighs somewhere around 40-50 lbs depending on what plywood and how much (correct me if i am wrong, we tore ours apart a year ago)

Another option is the 221 robotic systems stuff, while a lot more expensive, it is lighter and more effective (middle wheel driven by both cims, ability to use more wheels, and possible a tread system, option for multi speed gearboxes) than either the kit-bot or the nano-tubes.

Originally Posted by Hawiian Cadder

The kitbot weighs somewhere around 40-50 lbs depending on what plywood and how much (correct me if i am wrong, we tore ours apart a year ago)

Another option is the 221 robotic systems stuff, while a lot more expensive, it is lighter and more effective (middle wheel driven by both cims, ability to use more wheels, and possible a tread system, option for multi speed gearboxes) than either the kit-bot or the nano-tubes.

Can you legally order a 221 drive base and have that as your competition base?

[JesseK]

2 AndyMark SuperShifters + 4CIMs and associated pneumatic shifting accessories is ~16.5-17lbs by itself. Simply changing your strategy can change your weight allocation. (4CIMs = 10.4lbs, 1 SS= ~3lbs each). 2011, 2008, 2007, shifting was desired by many teams since it was a high-speed open field coupled with some fine movement control. In 2010, many teams didn't need shifters -- single speeds between 10-11 ft/s were fine and controllable. Yet in 2007, 2008, and 2011 plenty of teams were very successful with a single speed drive train.

The KOP frame itself weighs a bit -- 13lbs with all of its bolts and blocks if I remember correctly. Honestly, weight is the only issue I have with it. You may be able to save 2-3 lbs if you can fab your own plate gussets and use 1/4" rivets to hold it together, but I'm not sure.

This frame weighs under 7lbs after all of the bolts for the wheel blocks (black) are added. However, the frame rails (purple) are welded together; if you don't have welding capability then the KOP frame or 80/20 could be subsituted. Before electronics that drive train is a hair over 30lbs. Usually we allocate 35lbs if we do shifting, yet we can also get the frame welded.

Using #25 chain instead of #35 chain can save ~1.5-2 pounds but adds alot more fickleness to precision in sprocket alignment and tension. Chains have been our achilles heel some years.

The 2 teams I talked to with Nanotube frames said they're great. Drive the center wheel via chain and you're set. The hardest part was figuring out how to mount bumpers and a super structure to it.

[Andrew Schreiber]

Originally Posted by SuperNerd256

Can you legally order a 221 drive base and have that as your competition base?

Can you cite a rule (from 2011 since we don't have 2012 yet) that would say you can't?

Originally Posted by Andrew Schreiber

Can you cite a rule (from 2011 since we don't have 2012 yet) that would say you can't?

touché.

[JamesCH95]

3-4lbs can be dropped from the kit frame by welding it together instead of using fasteners. It's made from 5052 aluminum so it will maintain strength and is easy to weld, as far as aluminum goes. Just food for thought.

[Taylor]

Originally Posted by Andrew Schreiber

Can you cite a rule (from 2011 since we don't have 2012 yet) that would say you can't?

Originally Posted by 2011 Logomotion Rules

<R19> B. No individual item shall have a value of over $400.00. The total cost of COMPONENTS purchased in bulk may exceed $400.00 USD as long as the cost of an individual COMPONENT does not exceed $400.00.

The SuperLight Chassis Kit is $485. Since it is one line item on the order form, it would be one component.

[Andrew Schreiber]

Originally Posted by Taylor

The SuperLight Chassis Kit is $485. Since it is one line item on the order form, it would be one component.

Except it has two items inside the kit.

This kit includes the following:
1 - Super Light Side Rail Kit (37" or 27")
1 - Super Light Ladder Bar Kit (20.5" or 30.5")

[Arefin Bari]

We used these Nanotubes this past season and the whole team was very happy with the performance (We just want to make it faster in future). I believe after mounting the motors, all the wheels and the belly pan, the chassis weighed about 25 pounds. Our final weight of the robot was 101 lbs.

[Taylor]

Originally Posted by Andrew Schreiber

Except it has two items inside the kit.

So how would one show this on the bill of materials? Are inidividual prices given for the side rails or ladder bars? I can't find that information on the website.

-edit- nevermind. I was one click away. I'm surprised the kit price is the same as the sum of the individual part prices.

[Andrew Schreiber]

Originally Posted by Taylor

So how would one show this on the bill of materials? Are inidividual prices given for the side rails or ladder bars? I can't find that information on the website.

-edit- nevermind. I was one click away. I'm surprised the kit price is the same as the sum of the individual part prices.

Yes they are http://www.team221.com/viewproduct.php?id=95 and http://www.team221.com/viewproduct.php?id=96

[Grim Tuesday]

Thanks for the help everyone! Lots of interesting info here. I checked, and for reference, our current frame is ~60 lbs, including motors, and supershifters, but not electronics, or anything else. Youch.

I have a couple questions remaining:

-On the subject of Nanotubes, they seem to work pretty well. Am I correct in thinking that the middle wheel is driven by only one of the motors? If so, then wouldn't the speeds between the directly driven one, and the one driving the center one vary? Also, why are they only 31" when the robot can be up to 38?

-On the subject of IFI wheels: What size do most teams use, and why? What is better, the ones from IFI, or the ones from Andymark (non sequiter, IFI wheels from andymark, I get it)

So far, this frame seems quite good; have you guys had any durability problems with just the tubing? (I assume it's 1/8 inch? Or is it 1/16?)

Finally, we do have welding capabilities, as well as CNC in-school. If you want to see what this year's robot looked like, take a look in my signature. If the video isn't long enough, here are the stats:

Bottom from T-Slot, the top from 1/16 tubing (21 lbs)
Supershifters and 4 CIMS (20 lbs)
Tank Treads (20 lbs)

[Jared Russell]

You have multiple options with the Nanotubes...

1. Each of the three wheel mounting locations has all of the necessary holes to install a ToughBox Nano gearset. This means you can very easily install a motor to directly drive the center wheel (I would recommend it - that way if a chain fails, your "most important" wheel is still powered). This also means that you may do a 6-motor drive if you want to.

2. One of the Nanotubes comes with a set of spur gears to transfer power between one pair of wheels, and you can add chain to transfer power from the middle to the other end.

3. If you purchase one of these (or the Hex equivalent), you can cut it to length and replace the standard axle. This allows you to use two sets of chain, as well as wider wheels if you desire, to create a more conventional all-three-wheels-connected-by-chain 6WD drive module. This is what we did in 2011, using 4" diameter, 2" wide IFI wheels with blue nitrile tread. Just note that you may need to think about chain tension in this configuration (we actually simply used high-quality #25 chain, and had spare runs ready to install in case of damage or stretch. Despite some HARD driving through two regionals and the Championship, the chain never stretched to an unacceptable level).