Motor On Tower Temporarily Isn't Turning

[Athan]

Okay thanks for the help guys, I will try that out and hopefully that fixes problems

[mvas]

I wanted to make a few clarifications to a couple of statements I made (so not to confuse anyone). You should test freespin with a wheel or a gear because that will allow you to see the overall resistance in the system in comparison to momentum.

But to get an accurate gauge of the actual friction acting on the axle, use only the axle to get a feel for the amount of resistance. It should be negligible in both cases.

[marinmersenne]

Unless I’m mistaken(I’m on mb), you seem to be transferring power through the 12" shaft. It would be better to avoid this as it could twist the shaft and warp the frame(which may be the cause of your friction)

[mvas]

While this is true, there is hardly a load on this system. Additionally, there is no other way to transfer power with Vex parts for rubber band rollers. You could do something bulky or impractical with screw joints, but I wouldn’t recommend that for this particular case.

So yes, this statement is true:

@marinmersenne

t would be better to avoid this as it could twist the shaft and warp the frame(which may be the cause of your friction)

But only because the shaft is experiencing a high load due to friction. Once that issue is resolved, it shouldn’t matter.

[Athan]

I’d like to understand this problem. Are you saying that I shouldn’t connect 12’’ shafts to the motor because those are likely to twist? If so, how could I avoid this problem? I know that I probably won’t have to worry about this because I don’t have much of a load, but I’d still like to know what I don’t have to worry about if that makes sense lol

[mvas]

@mvas

Depends on two things: the length the axle will span and the load on the flywheel. If the axle spans length is more the full length of the ball (6"+), then use a high strength axle. If your flywheel requires a high amount of compression to transfer energy, use a high strength axle.

I am confused why everyone was so quick to dismiss the idea. For reference, most (if not all) of the 169 teams in TP used HS axles on their world robots. Any minute improvement to the robot is worth it, and a HS axle is simply more durable than a LS one.

Here’s a bit of explanation on my thoughts on an axle. This whole thread in general discusses it.

This is also a noteable reply:

@Aditya_Narayanan

This makes intuitive sense, and would seem to explain why low strength axles tend to bend when used over very long distances, but thinking about it in terms of pressure is not exactly the best way to go about explaining it, because the pressure on the ball need not be the same as the pressure on the axle.

I do want to hear what @marinmersenne has to say

Also:

@Athan

If so, how could I avoid this problem?

Screw joints

@333A

The most important takeaway from our research was that you should use screw joints whenever possible. This change had the greatest impact on the stability of our lift, and forever changed the way we build anything.

This whole thread has good coverage on that

BTW

An axle must be connected to the motor in order to power anything. Everything else could theoretically be replaced with a screw joint.

[768A]

Another solution is to add standoffs between your sprockets
Most teams in turning points had standoffs.
For their intakes.

[768A]

I am using screw joints and booth gears are connected with Standoffs powered by a gear train

[mvas]

@768A

Another solution is to add standoffs between your sprockets

I was considering this, but it’s not ideal for intaking. The main benefit of using rubber bands is their compliancy which could minimze the amount of space the subsystems take up (since the ball could “dig” into the rubber bands). This is impossible with standoffs. There is also contact loss from the irregular shape of the standoffs as opposed to circular rubber bands.

TL;DR space efficiency and energy transfer decrease with standoffs. The reason it was done in TP was that the front intake had to span the width of the robot and the low strength axle needed to be reinforced. Again, this could be completely eliminated with a high strength axle.

[mvas]

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?

[Athan]

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.

[Aditya_Narayanan]

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.

[768A]

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.

[768A]

I didn’t use LS Shafts i used screw joints.

[Xenon27]

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.

[mvas]

@Aditya_Narayanan

high strength gear with slightly drilled out circular inserts

You don’t need to drill out the circular inserts for a screw joint

@768A

I didn’t use LS Shafts i used screw joints

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.

[768A]

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.

[Calvin_Thrasher]

Robot leeks
20 characters

[marinmersenne]

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.

[Railgunawesome]

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