pic: 1899 Saints Robotics Plywood Drivetrain

[Amar Shah]

Originally Posted by z_beeblebrox

Looks really neat!

As someone who's been spending a lot of time designing plywood robots, I have a few questions:

-About how much does this chassis weigh?

-What thickness of plywood are you using?

-Why are you using such big wheels?

-How are your gearboxes mounted? Do you have prior experience mounting gearboxes like that?

-Why is the chassis glued rather than bolted? How will you repair it if you can't remove individual pieces of wood?

-Next to the gearboxes, it looks like the frame rail is covered by another set of plates that extend to the end. Why is that?

-Does the belly pan extend to the outer frame rails? It would give the chassis a lot of strength if it did, although it might make access to the wheels and chains harder. It might also make sense to cut out the belly pan below the gearboxes so they are accessible from the bottom.

Edit: the image in the above post isn't showing up. Here's the link to the image.

Edit 2: Just saw the description. The whole parametric thing is really cool. We did a very similar thing on our offseason drivetrain. Why did the 2014 chassis have problems with chains? We've found this construction method extremely stiff.

-I do not know how much it weighs off the top of my head. I'll measure it once winter break is over.

-5.2mm. You can buy it at Home Depot.

-They are only 6 inch wheels. Our team has always used 6 and 8 inch wheels, but it is very easy to change the height of the axles to suit 4 inch wheels.

-The inside piece of wood has a cutout for the gearbox shape, and bolts go through the outside piece of wood to the mounting holes on the face of the gearbox. We mounted them like this in 2014 and did not have any problems with it.

-Wood glue is stronger than bolts, because the joint is continuous, rather than stress concentrating around the bolts. This chassis is plenty strong to stand up to abuse. In 2014 we did not need to make any repairs. In 2013, we made two repairs using more wood as a patch, with five minute epoxy.

-I have a picture below that will hopefully it clearer how the chassis goes together. We glue individual pieces into beams first, and then glue those assembled beams together.

-The belly pan is only in the middle area. The chassis is rigid enough there is no point in extending the bellypan, and it is impractical because it would have to pass through the inside beams. There is nothing worth accessing underneath the gearboxes, so I didn't leave any holes.

-The chassis was intended to be used with polycord, but we had problems with slipping so we had to switch to chains in the middle of our first district competition. However, the center-center distance between wheels was not set with chains in mind, and was at the worst possible distance, where the chains would fall off with some driving, but there was not enough slack to remove a link. Now, the axles rest in removable blocks, which can be replaced with new blocks that have the hole drilled in a different location, making it easy to change the wheel spacing.

-I fixed that image, and here is that other one:

Originally Posted by Mr V

I always look forward to seeing 1899's robots at the competitions. Hopefully I'll be working at one of the District events that you are attending.

We will be at Glacier Peak and Auburn this year.