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Unread 26-12-2014, 14:54
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Re: pic: Proto Type Base Built

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.
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Unread 26-12-2014, 22:58
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Re: pic: Proto Type Base Built

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.
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Unread 26-12-2014, 23:36
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Re: pic: Proto Type Base Built

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?
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Unread 27-12-2014, 08:54
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Re: pic: Proto Type Base Built

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.
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