Also, I’m confused why you use a low strength axle immediately above the standoffs. That basically defeats the point of the standoffs. What was the thought process on that?
aah i see now. I was actually wondering when it was best to use high strength axels. I might invest in them. When people talk about screw joints are they talking about using the regular screws because i didn’t know the screws could go through gears.
They can’t go through low strength gears by default. You could either use a high strength gear with slightly drilled out circular inserts, or you could just drill out your low strength gear.
I only had 2 12inch shafts
I understand you reasoning but the spacing that i had and use of slip proof mats made it so that rhe rubber bands didn’t compress to reach the standoffs.
I didn’t use LS Shafts i used screw joints.
as long as the standoffs never interfere with the rubber bands as they compress, it’s good. but with smaller sprocket rollers, they probably would interfere, and you might as well just use a HS shaft.
You don’t need to drill out the circular inserts for a screw joint
In the picture you sent, there’s a low strength shaft used to support the flywheel (?) right above the standoff supports. Your reasoning for the standoffs immediately contradicts the LS shaft design choice.
Like i said i only had 2 12 inch shafts
Using standoffs on the first roller was my way of dealing with the fact that i only had 2 shafts.
The issue is that chain connecting the bottom and top rollers is on the opposite side as the motor, so any force on the top roller is transmitted through the whole length of the bottom roller. You can put the Chain connection on the same side as the motor or the chain can be placed directly on the roller end sprockets which is simpler but it does wear the bands down over time.
Edit: Regarding using high strength shafts, that would work, but you would have to drill out holes in the c-channel for it which in my opinion is not worth it if there are other options.
I think you would be fine with a low strength axle, just make sure it’s not bent. The load on the axles shouldnt be particularly high in the first place, since you are using rubber band rollers which compress
I discovered a while ago when I was working in CAD and I went to use spacers to box a c-channel that they didn’t completely fit, it turns out this is because they were “steel” c-channels that had been named aluminum in the library I was using. Anyway, cause of this I investigated and discovered that aluminum c-channels are actually thicker metal than steel, that is why steel has the larger flange. They both have the same outer size, just not inner.
Aluminum is .064" thick I believe
Steel is .046" I think
This really surprised me because I had no idea all along they were any different (I had been using aluminum since day one of robotics).
I guess it makes sense though. Steel is plenty strong, any more weight would add to unnecessary shipping costs. It’s already really heavy proportionally speaking.
Could be for shipping, but since the product is meant to be competitive still (I suppose) the real reason for making it thinner might be so the robot isn’t ridiculously heavy. Vex might not care about shipping cost who knows, it still cost me a ton in shipping to buy aluminum angles for my tray.
Didn’t Vex originally only sell steel which means that its probably the aluminium that has been made thicker than the steel to compensate for being softer.
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