We’ve all built the protobot, competed with the protobot and are familiar with it’s minor issues.
I’m about to start mentor training and I want to build a better protobot. Key upgrades that we’ve made in the past have been replacing the small wheels with tank treads with mid-flaps to make it easier to grip things. We’ve also made the scoop from 2x*10x metal to give it more surface.
But the base is a mess. The spacers become loose and the entire drive train falls apart. One of the things we do now is to make the possibility of a four wheel drive. We do two rear driven wheels that also drive the 60 gear. We build in space to support an 84 gear to connect to the 60 gear fronts. We put the bearing blocks in place ready for the axle, gear and three collars to turn a two wheel drive to four wheel. We give the option of doing plain wheels or omni’s on the front. We use nylon locks on the key parts to keep the frame together. We use the star washers to lock the spacers in place.
I’m looking a the Vx+1 protobot. It should pick up rings and the green soccer balls. Should be able to score the high posts in Round Up and High Towers in Clean Sweep. I’m willing to go a few dollars over the basic kit (ie treads and flaps or extension slides and rack gears)
Tell me what you would put in your protobot?
Put a cost estimate over the original protobot. Both Adam and Cody are going to show up with Omni wheels, at $30 a pair that adds a lot of cost. Can you do better?
Prize given for the most changeable robot with the lowest additional cost.
In terms of “kit chassis”, the protobot’s main difference from the squarebot other than the wheel size change was the change in chassis setup - moving the outer rail outside the angle pieces with standoffs. This presents a problem because those standoffs get loose approximately every 5 minutes. The quick solution is thread locker - this stops the drivetrain from falling apart all the time. I don’t like it as much as other design changes though…
How I would like to modify the protobot for demo use:
Get longer angle. The “wide version” of the kit drive works just fine for turning even without omnis, but those standoffs suck. Just get some longer pieces of angle that extend all the way out and you’ll get a more rigid and stable chassis.
If it’s light, try gearing it differently. If you have 4 motors you can pull off gearing your drive 3:1 with small wheels, or 7:5 with big wheels. For demo purposes this should just make the robot a bit more fun and hard to control
Bearing rivets never come loose. Don’t forget that! It makes a lot less bolts come loose so you have less stuff to check on. I don’t know if the kits come with these but they really should.
No one said you couldn’t replace the roller claw with the Vexplorer claw. Works better for tubes than, say, soccer balls, but it’s a lot less of a hassle for a Round Up demo than negotiating a roller claw to work.
Get some rubber bands to balance the protobot’s arm. A lot easier for strangers to control an arm that holds itself up.
I noticed the protobots your team had running at IRI were a bit modified. I think a more rigid structure for the bottom metal plate you guys were using as a roller claw would have worked much better. More bolts holding it on?
I would go with a very large chassis that could surround the arm. I have seem a few protobots flip over when they try to lift something a bit too heavy because the CG is pushed way forward. It the chassis were extended forward and there were wheels out front then there would be no real risk of tipping. Does this make since?
Replace each pair of Chassis Rails with a single piece of C-Channel. C-Channel is good (Use your Tarzan voice to say that part)
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Put the 2-hole side of the C-Channel on top. The “C” will open downward.
Put motors on the inside of the bot, gears and wheels on the outside.
Mount a Flat Bearing block inside the “C” of the C-Channel for the motor. Mount another on the outside for the Wheels/Gears.
Arrange the Bearings so that only their end holes overlap (Axle obviously goes through the end holes). That makes it possible to tighten the inner Bearing’s Screws (the Motor Screws) without removing the outer Bearing’s Screws.
Put a Shaft Collar and a 1/8" Nylon Spacer inside the “C” of the C-Channel to keep the Axle in.
If there is no gearing on the outside of the Bot, put an 1/8" Nylon Spacer between the outer Bearing and the Wheel to avoid collisions between Screw Heads and the Wheel.
Put a Shaft Collar outside the Wheels/Gears to keep them on the Axle.[/INDENT]Both the Wheels and the Gears can be now be swapped out by just loosening the outer Shaft Collars.
This will probably take about 1/2" off the width of each side (If you move the C-Channel closer to the center to get full overlap with the Chassis Bumper you will lose another 1/2") and consequently affect the handling characteristics a bit. I say no big deal, but if you want to regain that 1/2" (or make any other width adjustments, replace the Chassis Bumpers with pieces of 1x2x35 Angle (or 1x2x35 C-Channel or 1x3x35 Angle) cut to whatever length you like.
Blake
[Edit]I forgot to point out that the motors are thicker than the C-Channel. When putting on Chassis Bumpers, or the equivalent, you can’t mount the Motor at the end of the C-Channel (the way it appears in the picture I attached to this post).
Instead you would need to rotate the motor so that it’s bulk is in the interior of the chassis instead of at the end of the C-Channel piece.[/Edit]
Blake’s cost adder is 1/2 of a 4 pack of C channels, about $10 each, thats hard to beat for cost effectiveness. The 4 extra Rails can be salvaged.
Version 1:
Everything that Blake said, with following changes:
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Replace the motor bearing, clutch, axle retaining collar, 1/8" washer, and motor axle with a longer axle, clutch, teflon washer as normal in clutchless setup. This shows that motor socket can be used as a bearing.
put outer bearing block inside the C instead of outside next to wheel to reduce the cantilever moment arm of the cantilevered wheels.
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This provides the opportunity to learn if clutches provide any value, and if so, an opportunity to learn how to replace motor gearheads.
Version 2: (less well though out, trying to avoid cantilevered axles entirely…
Same extra parts as Blakes, one pair 1x2x1x25 C channels each.
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Use C’s to replace or augment the bumpers, so that they reach across all 4 rails.
Place wheels between rails so they are not cantilevered. (yeah!)
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This should works fine if not using gears.
Outside rails shield wheels from running over game pieces, allow sliding along walls better, etc.
Pardon the slight off topicness of this post, but what’s the problem with a well supported cantilevered wheel? I think for the particular application here (light, simple robot with as little additional pieces as possible), cantilevering wheels is not a problem.
Roboteers could consider taking a page from the Squarebot and moving the rails so they’re both inside the robot. All you’d have to pay for would be bearing rivets (which if you couldn’t tell already, are awesome!)
[/INDENT]
This should works fine if not using gears.
Outside rails shield wheels from running over game pieces, allow sliding along walls better, etc.
Sticking with the Protobot assumption of a light bot that doesn’t require strong outside Rails, I would be tempted to use pieces of Flat Plate to create side shields. The Plates obviously protect a larger area than a piece of C-Channel or Rail; but on the other hand, they are also weaker and more easily damaged.
use short motor screws to fasten the motor directly to metal (no bearing)
Fasten a flat bearing block inside the C, with screwheads on the wheel side and nuts against the bearing.
From outside to inside, the axle stack is this:
– Outer shaft collar to hold wheel on.
– wheel
– spacer washer to keep wheel from rubbing frame and bearing bolt heads
– outer edge of the C frame
– bearing on the inside of the C frame at the outer edge
– inner edge of C frame (If axle corners scrape the metal, this frame hole could be enlarged.)
– teflon or other low friction washer
– shaft collar to hold axle into motor
– motor axle socket, which acts as inner bearing for lever loads from wheel.
If that doesn’t do it, I’ll have to post a picture. Posted…
