Harvard-Westlake Robotics: BLZ-i Reveal

The HS shafts have a lot more friction in the bearings than the LS ones do in the LS bearings, so sanding them down where they pass through the bearings does help reduce friction.

I wouldn’t recommend sanding it down as much as they did in the assembly videos though, those had a lot of play and I’d be almost worried about the gears slipping when they didn’t mesh.

You should straighten up the geometry some, using shoulder screws, either from Robosource.net or the vex ones can help a lot with that.
Additionally, you can use a low strength shaft, if you build it right you won’t have any problems with it bending and it’ll be lower friction.

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It is fairly noticeable. By about a mm or two. Is it legal to shave down the sprockets?

You can find the answer to that in the game manual, more specifically R22



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I’m running in to that problem now. could you elaborate on what you did? Did you add gearing to the motor before it connects to the HS axel?

Yea, I just added an extra axel in between the intake and roller flex wheel that had the largest size sprocket and the smallest size sprocket on it. Then connect the intake to the big sprocket and the roller flex wheel to the smaller sprocket. This creates compound gearing for torque as the middle axle with the 2 sizes of sprockets on it will have a torque ratio from the intake and will create a multiplicative torque ratio to the roller. This happens because the sprocket on the roller flex wheel is bigger than the smaller sprocket on the middle axel.

My team is late to the jump and decided to build this bot, but it is not shooting far at all. We believe the indexer is not generating enough force when hitting the discs. How can we make it hit harder with that limited amount of space? Any help is greatly appreciated. Thank you!

Your flywheel is the problem here. You’d need to post a little more, maybe a picture, maybe a video, if you want help.

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What rpm are the flywheel motors spinning at? If you built the flywheel the same way the videos + cad did chances are your issue is with excess friction. Take the motors out and try spinning the axle manually. It should be able to spin with very little resistance. The issue likely isn’t the indexer, but if you still suspect it try pushing the disk in manually with your hands to test and see if it would work.

I have a couple of questions. My team has got the bot nearly built but we they are working on the shooter and the intake. I messed up when ordering parts and didnt realize that I needed the 16 tooth sprockets, so all we have are the 12 tooth and I have no way of getting the 16 tooth this late. Can we use the 12 tooth instead or are we in trouble? Secondly with the shooter, there is a strip of polycarb at the top that uses Vexfoam, I didn’t order that either, and the pieces of polycarb I have left arent long enough to make that piece without splicing it somehow. Do I have to use VexFoam or can I use essentially weatherstripping since that is what it is.

You can use 12 tooth sprockets as long as they are kept in a 1:1 gear ratio. If they are 9p sprockets you will have to come up with your own spacing as putting 2 9p sprockets next to each other on an axle causes the chain to rub. There are alternatives to the Vex Adhesive foam. The easiest one would be to use grip mesh instead of foam. Another solution would be to increase the compression of the curved polycarbonate strip, eliminating the need for the foam. If you don’t have enough polycarbonate to make the curved strip, you could probably make a similar curve with 5 wide plate.

I meant to reply and thank you for all of your assistance! Your advice helped tremendously!

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Seems as if I made one more error in judgement. I forgot to take into consideration the wheel gear ratios. I don’t have 4 blue motors for the drive motors. I had to order two extra anyway. Will the green ones do in a pinch?

Kind of, it will work but you will be going very very slow, 100 rpm to be exact

Not really, it will be very slow. But I’m sure you can find an alternate gearing takes up the same space and uses the same wheel size and is a decent speed. Look here:

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