pic: Its twins - prototype drives

[Jonny_Jee]

Originally Posted by GarroH

Just curious, what sort of efficiency loss do you get with using the right angle gears? Is the loss in efficiency/power worth the savings in space?

I'm a little late to the party here but according to MEADinfo.org

1 Spur 1:1 to 6:1 94-98% Efficient
2 Straight Bevel 3:2 to 5:1 93-97% Efficient

reference:
"Comparison of Gear Efficiencies." MEADinfo.org . N.p., n.d. Web. 11 Aug. 2016. <http://www.meadinfo.org/2008/11/gear-efficiency-spur-helical-bevel-worm.html>.

[Cothron Theiss]

Originally Posted by Jonny_Jee

I'm a little late to the party here but according to MEADinfo.org

1 Spur 1:1 to 6:1 94-98% Efficient
2 Straight Bevel 3:2 to 5:1 93-97% Efficient

reference:
"Comparison of Gear Efficiencies." MEADinfo.org . N.p., n.d. Web. 11 Aug. 2016. <http://www.meadinfo.org/2008/11/gear-efficiency-spur-helical-bevel-worm.html>.

Are those figures assuming that exact center to center spacing is used? If so, spacing those gears out just a few thousandths can squeeze out some extra percentage points to make up for any loss. It's the first stage of gearing, so the loss in load capacity shouldn't be an issue.

Looking at that page, I realized the OP could probably switch to spiral bevel gears without much increase in price, depending on the supplier they're using, but since they already have the straight bevel gears they need, it probably doesn't matter.

[asid61]

Originally Posted by Cothron Theiss

Are those figures assuming that exact center to center spacing is used? If so, spacing those gears out just a few thousandths can squeeze out some extra percentage points to make up for any loss. It's the first stage of gearing, so the loss in load capacity shouldn't be an issue.

Looking at that page, I realized the OP could probably switch to spiral bevel gears without much increase in price, depending on the supplier they're using, but since they already have the straight bevel gears they need, it probably doesn't matter.

Spiral gears tend to be 2-3x as expensive as straight tooth, and IIRC don't give an efficiency advantage as much as they do a quietness advantage.
The quoted numbers have no context, but I would assume most FRC bots will get less efficiency.

[GeeTwo]

I like the wide open interior space - it would have relived a number of constraints on manipulators this year.

With those long chain runs close to the carpet, I would be worried about snagging threads and other debris, especially as the chains get loose. Is there some reason you decided to route the idler offsets to pull the top chain down rather than lift the bottom chain up?

My initial understanding of the small wheels inboard was to have the ability for more contact points with the floor. If you reduced this from 6 wheels per module to 4, would you make the wheels of equal/closer size, or did you do this for some other reason?

[Seth Mallory]

I like what you are trying to do. Four of the last five years the GRT drive trains have been working on increasing the free space in the robot. With the three motor drivers the loss of a few percentage points of power is compensated by the increase in space for interesting mechanisms.

[Dave McLaughlin]

Nit-picking at best, but I can't help but notice a lack of fillets on both interior and exterior vertices. The sharp corners will introduce stress concentrations that could be avoided by including even small radius fillets (albeit larger than the inherent radius left but whatever cutting tool you are using). If you are going to continue using 3/16th material during competition I would urge you to reevaluate your truss pattern. I think that you can be much more aggressive on material removal.

I appreciate trying to free up space inside the frame, but I have to wonder what is the acceptable cost. Max hits the nail on the head with this question IMO.

What exactly are you guys trying to get out of this drivetrain that could not be done with a standard 4 or 6 cim versa drive or even a kitbot?

I want to be clear that I am not trying to stifle creativity, which seems to be the current sentiment critical analysis brings about on CD.

[Nick Lawrence]

This is cool. I definitely like the idea of trying to save interior space in the robot for mechanisms. It sure can make moving multiple or large game pieces through a robot easier.

Only one thought - other than wheel bolts, are there any standoffs inside the frame connecting the inside and outside plates of the pods together? I would be a little bit worried about a significant impact to the plates - even 3/16" thick. Some carefully arranged standoffs could help mitigate this, especially near the corners.

Please keep working on this drivetrain, offseason projects are a great way to try new designs that push the limits of "should I really do this?"

-Nick

[ArtemusMaximus]

Looks like motorized roller blades LOL