8 Wheel Chassis Design

[akoscielski3]

Originally Posted by ratdude747

Suggestion: Beef up the axle mounts... they look a bit skimpy and given a hard enough ramming could warp. with an integrated design like that, such a failure could be catastrophic.

I have't had a problem with axle mounts like this in our 2012 chassis. What should I do to make them better? cross braces meeting in the middle? or make it wider? (currently 1")

@SuperNerd256
We've used them so much they have just been over used. We like the idea of having the gears closed in too. We wont have to worry about getting chips in the gears anymore.

[sdcantrell56]

Originally Posted by akoscielski3

I have't had a problem with axle mounts like this in our 2012 chassis. What should I do to make them better? cross braces meeting in the middle? or make it wider? (currently 1")

@SuperNerd256
We've used them so much they have just been over used. We like the idea of having the gears closed in too. We wont have to worry about getting chips in the gears anymore.

A supershifter is just the AM Gen1/2 with an added stage of gearing. This is heavier and lower efficiency. I would suggest sticking with the Gen1/2 unless you have a good reason to swap like needing to direct drive a wheel. Even so you could make a custom transmission for that using wcproducts gears or better yet drop to a 3" wheel and you can run a stock AM Gen1 direct drive

[Adam.garcia]

Originally Posted by sdcantrell56

A supershifter is just the AM Gen1/2 with an added stage of gearing. This is heavier and lower efficiency. I would suggest sticking with the Gen1/2 unless you have a good reason to swap like needing to direct drive a wheel. Even so you could make a custom transmission for that using wcproducts gears or better yet drop to a 3" wheel and you can run a stock AM Gen1 direct drive

If you are looking to decrease significant weight, look to 1:1 replacement gears for the gears in the supershifter. You can find them here:

http://wcproducts.net/gears-20-dp/

[AlecS]

To go along with what Sean said, why did you chose to go with the SuperShifters, AND an additional sprocket reduction to the wheels?

By looking at the pictures, it appears like you are using a 12-22 sprocket reduction after the SuperShifters. If this is in fact correct, this would yeild,

-With the Standard 2.56:1 Spread,
~2.84 FPS in Low Gear,
~7.27 FPS in High Gear,
and only ~17 Amps per motor to spin the wheels in low gear.

-With the Standard 4:1 Spread,
the same low gear
~11.37 FPS in High Gear.

Using the optional final reduction reduces speed in both cases, though I'm assuming that wasn't your intention.

In either case, you may want to think about reducing your overall reduction. 2.84/7.27 FPS is going to be quite slow for navigating an FRC field (think, FRC71 in 2002), and won't help your overall pushing power, since you're already limited by traction.

If you want to stick with SuperShifters, you will probably want to look into direct driving one wheel, and chaining the other 3, 1:1

Although you may be "sick" of the AM Shifters, using the same (assumed) 12-22 sprocket reduction, they would yield, ~6 and 16 FPS. Both very respectable speeds to maneuver the field, and would still be able to spin the wheels in low gear in under 40 Amps per motor.

The third option would be to make you own gear reductions, and use smaller wheels.

Also, one more note, this drivetrain only has an .SLDASM on frc designs. In order for Assemblies to opened on other machines, both the .SLDASM, and all .SLDPRT files in the assembly need to be present. Using the Pack and Go feature simplfies this task greatly.

-Good Luck

[flargen507]

159 did something similar to this for 2012. To create a strong, light, flexible West Coast Drive, we used 1.5" by 3" aluminum tubes. These were pocketed circularly (a lot) and the wheels were outside. It only needed one tube per side, and even with extensive pocketing it retained structure even under competition abuse. If that's at all helpful to your designs, it worked really well for us. Look up Hawaiian Cadder, he posted the design.

Your design is very interesting. Using traingular pocketing with sheet metal was a good idea, but sheet metal does require the outside wall (although this does improve your turning radius, so more power to you.) I would suggest that the gearboxes be moved to the center to keep the CG (we used the battery as the counterbalence to the shooter). Depending on what type of tread your are using, you may need to increase your center drop to 3/16". If there is any way to use 25 chain instead of 35, this could save you a lot of weight, and 159 had no troubles with the strength of 25 chain. 8WD can turn quite well, but it does need a significant center drop to do so. We used AndyMark supershifters, however I cannot comment on their goodness/badness to Gen I shifters(having never used Gen I's), but so far as I can tell AndyMarks work just fine.

Lastly, if there's any way you can incorporate multiple placements for axles, this could make modifying it very easy for next year's season.