Re: pic: Spectrum Fall 2013 Drivetrain
 

I can't tell you why you should like it but I can tell you what's attractive to us.

Off The Shelf Parts
Outside of the sheet metal which we get produced by our sponsor, every piece in this is off the shelf and can be assembled with little to no modification. Nothing requires a lathe or a mill. Seeing as we don't have access to either (yet), this is an important feature. It's currently near impossible to meet this requirement with belts.

Narrow
The new robot dimensions (assuming they stick around) make the standard kit bot way of doing chains seem really large, the kit bot or VEXpro drive in a day are good examples. For reference those are the types of drives we have used before. A WCD might be a bit thinner but we don't have milling and welding resources but we have a great laser cutter/sheet metal sponsor.

No tensioning or ever throwing belts/chains
A good drivetrain has a great tensioning system and never throws belts or chains. I am not confident enough that we can build a drivetrain that will meet those requirements. The gear drive solves that problem.

No need for access from the top of the box
We now have the entire width of the robot for our game playing elements. We can cover the entire top of the drive train and not worry about having to ever reach in a fix a chain or belt. We can replace wheels extremely quickly with just one bolt each. This also might be marginally safer as it is harder to get a finger or drop something in the drive.

Can change wheel configurations easily
10, 8, or 6 wheel configurations are all available with this robot without changing much of anything except removing a wheel or two. You could build the same thing into a chain/belt system but that would be a lot of tensioning.

It's a prototype
And the last reason is it's a prototype and it's different. In 3 months I might be completely on the other side of this issue and telling people to never build gear drivetrains ever. If that does end up being the case, we'll have with a nice stock of gears to use for future gearboxes and a story to tell.

Re: pic: Spectrum Fall 2013 Drivetrain
 

Thanks for pointing that out, I didn't even realize there was a 3rd stage available. That makes things a lot easier.

Also thanks to you and Madison for posting your prototype drive trains in the off-season. It's been fun to read the discussion and mull over some ideas for sheet metal fab drive trains.

Re: pic: Spectrum Fall 2013 Drivetrain
 

Yep, that's what we do. In fact, the Verskey pattern in the gears was meant to help with gear alignment for this purpose.

Re: pic: Spectrum Fall 2013 Drivetrain
 

I'm not trying to bash your drive nor am I against the concept of a gear drive. If we had the time and the drive to do something different I'm sure my team would prototype one as well. Just thought I would share some info about belts.

If you can manufacture a drivetrain with enough precision for a functional gear drive, you have more than enough precision to make a dead spaced belt drive, which does not need tensioners.

A properly designed belt drivetrain should never need any maintenance. For the past three seasons we have not touched a drive belt since week 4-5 of build season (unless we had to remove an axle for another reason, but that doesn't really count). So this same advantage can apply to belts as well.

Re: pic: Spectrum Fall 2013 Drivetrain
 

Yes but where do I get pulleys with the 6 hole pattern already machined (and preferably with versakeys)? Aren or Paul want to chime in here?

Also I did a quick cost break down of the Gear Drive vs. an 8 wheel #25 chain drive.
The gear system is about $170 more.

Here are the spreadsheets.

Re: pic: Spectrum Fall 2013 Drivetrain
 

andymark?

http://www.andymark.com/product-p/am-2234.htm

we used these in our shooter this year. worked great! I would love to see more sizes available in plastic. Buying from gates in canada takes a long time, and is far too expensive. Still did it this year though, and it was worth it.

Re: pic: Spectrum Fall 2013 Drivetrain
 

Thanks Kevin, I should have clarified, that I was looking for more sizes that just the 42t AM pulleys.

Re: pic: Spectrum Fall 2013 Drivetrain
 

OH yeah! GT2 or HTD pulleys with a versakey pattern! Aren make it happen!

Re: pic: Spectrum Fall 2013 Drivetrain
 

I'd be surprised if this wasn't already in the works at IFI or at other suppliers.

Re: pic: Spectrum Fall 2013 Drivetrain
 

Looks like a really good drivetrain, I'll have to have my team look at this and maybe try something new this year. We usually just use the standard drivetrain but this looks like something we could do this year.

Re: pic: Spectrum Fall 2013 Drivetrain
 

I wish there were more sizes too. Ive been thinking of cadding up a drivetrain using only gears, but I could never justify the weight when compared to the same thing with the plastic 42 tooth pulleys and 15mm belts. Always liked the idea though.
How are you planning on adjusting the backlash on all those gears, or are you not worried. I cant see it being a major issue, but i thought id ask.

Re: pic: Spectrum Fall 2013 Drivetrain
 

This. Please. Please. Please. (If we keep asking does the chances of it actually happening go up).

The only current problem with belts (at lease in my opinion) is that pulleys require decent amount of post machining to be utilized the most effectively. COTS FIRST-standard pulleys would fix that (as I understand it there's something about licensing the tooth profile that stands in the way, but mon dieu if this could happen it would make my 2014 build season).

Re: pic: Spectrum Fall 2013 Drivetrain
 

I agree that belts would be lighter, though we really haven't had a weight problem the last two years. We actually have been struggling to get up to 120lbs, to get more traction. Right now I would take the smaller footprint over the lesser weight option.

I haven't thought about the backlash, several teams have done gear drives and haven't mentioned it being a problem.

Re: pic: Spectrum Fall 2013 Drivetrain
 

Backlash, what backlash? Not a problem. Also we were under 80lbs this year so weight wasn't a problem for us.

The new small drive size was one of the factors that made a gear drive practical this past year in both weight and cost.

Re: pic: Spectrum Fall 2013 Drivetrain
 

I like your effort for making a smaller footprint. For the last couple of years 192 has been working to reduce the footprint in a different way. For those that know 192 you will be shocked to hear that the students have a new gear box that should be more space saving then the last 2 years.:)