2015 Off Season Chassis

The chassis (grabcad) is made out of 2x1-1/2" square tubing with 1/8" thick walls that has weight savings to allow for maximum rigidity while cutting the most amount of weight out of the tube. With all of the hardware on the chassis, it should weigh around 23-28 lbs. The gussets are made of 3/16" thick plate that will keep the chassis square. The sheet metal siding is made of .009 in. thick metal that is bent to make it stay straight.
http://s22.postimg.org/8zg782cml/2015c_chassis.jpg](http://postimg.org/image/8zg782cml/)

How much weight does your CAD program say that all those cutouts in the tubing will save? Will the tubing still be strong enough? There are 16 long bolts tying the corner gussets to the tubes. How much weight can you save by riveting the gussets to the tubes instead? Will these bolts crush the tubing, especially if you have removed so much material from the tubes. Using a triangular piece of 1/8’ material instead of an L-shaped piece of 3/16" material would probably give you more stiffness and possibly lower weight. The pieces outside of the wheels have cutouts with sharp corners. Do you have access to manufacturing processes that can do this? Will these sharp corners cause stress fractures? Do these two side pieces attach to the front and rear tubes? You may want to make the flanges on these side pieces larger so that they will be stiff and can be riveted to the tubes. Are those pulleys on the wheels for belts to connect the 2 outer wheels on each side to the middle wheel? What do the belt runs look like?

“How much weight does your CAD program say that all those cutouts in the tubing will save? Will the tubing still be strong enough?”
It approximately save 50% of the weight by keeping enough strength to hold up in the heat of competition (this comes from a design of a chassis used in 2014).

“How much weight can you save by riveting the gussets to the tubes instead? Will these bolts crush the tubing, especially if you have removed so much material from the tubes?”
We only have the capability to do blind rivets which can easily be broken so that is why we feel that it is necessary to use the long bolts to attach the chassis together. Another advantage of using bolts is that it makes taking apart the chassis easier. The gussets have enough surface area to distribute the force of the bolts on the tubing accordingly to prevent the tube from bending. This is a design that we have been using for the past few years with no problems.

“Using a triangular piece of 1/8’ material instead of an L-shaped piece of 3/16” material would probably give you more stiffness and possibly lower weight."
This is a good idea that I will go over with my team, thanks for the suggestion.

“The pieces outside of the wheels have cutouts with sharp corners. Do you have access to manufacturing processes that can do this? Will these sharp corners cause stress fractures? Do these two side pieces attach to the front and rear tubes? You may want to make the flanges on these side pieces larger so that they will be stiff and can be riveted to the tubes.”
We are using a CNC plasma jet to machine out these cutouts and it is capable of cutting these sharp corners. These side-plates are not structural at all, it is only there for the bumpers meaning that it needs little strength. The side-plates are attached to the chassis by the 1/4" plates between the wheels. It does not attach to the front/rear tubes, it simply is bent around the tubes.

“Are those pulleys on the wheels for belts to connect the 2 outer wheels on each side to the middle wheel? What do the belt runs look like?”
We are using 9mm wide belts on 18mm wide pulleys making it possible for both of the belts to originate at the middle pulley and have one go to the front pulley and the other to go to the rear pulley. This is an image of what I am talking about.
http://www.wcproducts.net/media/catalog/product/cache/1/image/650x/040ec09b1e35df139433887a97daa66f/p/u/pulley-belt-demo_2.jpg