We built the Frame and it only took two hours. It was an easy build. We installed the drives and test drove it with no problem. We limited one direction to 30 inches so we could get it though doors.
What size square tubing is that and what did you use to bend it?
Why wide over long?
Looks pretty neat.
How are you planning on mounting gearboxes, wheels, etc?
The tubing is 3/4 x 3/4. We bend it using a 3/4 EMT pipe bender used for bending electrical conduit. For mounting the wheels we will build pillow blocks that will allow us to adjust tension on the chains. The drive system is the same that we used last year, super shifters modified into a modular system that can be remove with just four bolts. More pictures can be viewed on our web site: http://www.team1322.org/ideas.htm#ANTI T-BONE FRAME
What was your reasoning behind the design of the interior frame pieces? It seems at first glance like two rails of C-channel, one on each side, perpendicular to the front and back rails, would have done a better job of holding the transmissions and bearing blocks, rather than the bent tubing shown. It also might be less complicated to build.
Very neat frame. One item I would caution about bending square tubing, You inherently weaken the column loading it can handle. Assuming the flat sides are the front and back, you will want 1 or 2 pieces to run for-aft on a chassis like this that are nice straight columns. Otherwise, with hard impacts, I would expect this frame to continue to bend and compress in length.
This frame is designed around our drive system which you can view on the link. When the drive is mounted it will add front to back support.
Which part of the drive do you use to strengthen the frame from front to back? Do you use the transmissions as stress members?
What I was talking about in my last post would look something like this:
(with the dotted front rail being at the front of the robot, I don’t have a character that is a high horizontal line)
Built that in two hours? Wish we could get our build team anywhere close to that speed.
As shown above we use a special built bracket that we made for the super shifters to help strengthen the frame. We removed the 5 x 5 square tubing from the gear boxes and replaced it with the bracket which allows us to move the frame up a few inches in the bumper zone.
Extremely non-conventional, but very cool, especially given the construction time. Maybe provide a video of it driving eventually?
What happens to your frame when you apply a compressive force on two diagonally opposite corners? It seems that it is the two U-shaped pieces of square tube that keep your chassis from “parallelogramming”.
Is there a reason you chose to use two u-shaped pieces of bent tubing vs. a single straight piece down each side? It seems that the manufacturing tolerances (bending cutting drilling) would have to be pretty tight to keep the six axles parallel to each other. How are the axles for the front and back wheels attached to the two left/right frame members? The holes for these four axles are not perpendicular to those frame members.
Depending on the game we will have sheets mounted to the frame to mount electrical and other items, this will give directional strength. If we use #35 chain we can just mount pillow blocks to the frame at the correct chain tension and that will take care of the axel mounts. I want to keep it simple for the students to build.
The bracket mounting the gearboxes looks like a flat bar. Does it have any extension in the vertical direction? If not, you may have some flex in this member in a head-on or rear-end collision. This could momentarily reduce the chain tension. Combined with the sudden change in the traction force this could lead to losing the chain from the sprockets. I would actually consider that bracket (or some supplementals) to be part of the chassis rather than just a gearbox/wheel mount since it provides the continuous front-rear loading.
Also, why the 1-3-1 wheel count per axle? Does it help traction that much, or do you figure that it’ll reduce the fraction drive force that must be delivered by chain (vice direct drive)?
I’m also in agreement with philso as to feeling queasy about not keeping the wheels aligned in a diagonal collision, or more properly with not keeping the sprockets in the same plane and losing the chain. We have never depended on a control board for this; at least since our second year we either used triangular structure or large (8") flat braces on everything but our wooden prototypes. I wasn’t in the mix our rookie year (Rebound Rumble), but the control board was vertical, so it wasn’t providing stiffness. On the other hand, I don’t recall many robot-to-robot collisions in RR, so we may have just skated on that one.
Thinking about the things that can go wrong with this design makes me like the simple pseudo-WCD* design we’re using for our prototyping tank chassis - short of bending the main c-channel members, there’s no way a bumper collision can mess up the sprocket alignment or spacing.
- Pseudo-WCD in that we’re using cantilevered axles, but not direct driving the center shaft. We’re also using wheel bearings on fixed-mounted axles so imperfect machining won’t cause (as much) wobble. Along the same line, we’re using COTS shifters: AndyMark Super Shifters, but the design is adaptable to Sonic Shifters with just two more holes in the chassis and longer chains.
Oh - but I do like the idea of having one double-ended piston drive both shifters. Since the high gears must be on the motor side of one gearbox and the wheel side of the other, this is probably not a COTS gearbox, or at least a reconfigured one.
I thought for a while that these might be AM Super Shifters with the spacers instead of the extrusion, with the one on the left in the picture built with a lot of pieces backwards (both plates, and the plates on the left gearbox in the picture flipped so the shafts line up, as well as the high/low swapped on the dog and drive axles). Even with all that, the location of the gears on the shifter shaft don’t quite work out; one side would be in low gear while the other was in high - am I missing something?
Here is a picture of the mounting plate for the super shifters. We used the same drive layout last year and had no problems. We added the additional wheels in the center for more traction. How strong the frame will be we will find out if this years game allows. http://www.team1322.org/20140612_201621.jpg