New products relating to skyrise

So today i took a close look at the new products. I am kind of ssurprised at how the company predicted our need for this year. Few thoughts on the new products:
first, 84tooth high strenth gear.
This product is no surprise. We have been discussing it for a long time. Comparing to the old way of combining two low strength gears to make a high strength one, the new product saves space. When it comes to building 1:7 gear ratio scissors lifts, this product can be helpful.
second, the high strength shaft kit. VEX published a renewed shaft system, which is going to start a new budget race among teams. Yes we do bend shafts in the past, but that was never a decisive issue in robot building. But who knows, this year super heavy scissors lifts and elevators may require these shafts.
Third, turbo motor gear. Very exciting, that is how it looks like. But considering this year’s game, well… hard to say. High speed roller intake is not the ideal choice for cubes and skyrise sections. If this product were revealed last year, then of course each single team will use 240 rpm for their rollers.
The new wheels, well i am happy to see products from green hulk migrating to vex high school. The wheels did not appeal to me a lot, but the direct mounting holes are interesting. Yes, constraining gears and sprockets sound nice, but most importantly the holes are easier for us to directly mount drive shaft bar locks to prevent stripping the plastic shaft square hole. For this reason they might sell well, but we are used to the 160rpm 4inch wheel speed, so i cannot predict how people will welcome them.
The battery extention is no surprise or necessary. Just a nice addition.
Anybody who has opinions of the new products in new game skyrise, feel free to post reply.

I’m not Shure about the hs shafts because they don’t fit in the motor where the most torque is usually required. But I do see where they could be useful.

Also the gage of wire on the battery extender looks way too small to me and also does not look like the soft silicone wire on the batteries but like the regular wire that we have had so many problems with on the power expanders. I hope we don’t have issues with the insulation on this wire breaking aswell.

I think huge scissors lifts and elevators may require these shafts as joints. Not directly powered by a motor.

The extention wire is really not much of my concen. Great accessory but not required. I hope the connections are made reliable, because we’ve had enough trouble changing batteries at last minute and finding out there is a connection problem with the cortex. More wire connections can be helpful but also brings up the risk.

I don’t think we will be needing any high torque for this game. It’s all about speed!

I mean, the bottom shafts that support the whole structure may perform better if they were high strength ones.

240rpm motors

2.4:1 direct drive drivetrains…

O.O

My favorite new product is the new 84 tooth high strength gear. Can you say TORQUE!

The motor doesn’t have near enough torque to twist an axle. The motor powering a 12 tooth gear going to an 84 tooth gear the axle has 7 times the torque and feasibly could be twisted. This becomes more of an issue on a 1:15 lift. That is when you need the strong shafts.

You don’t understand how torque works in relation to gearing.
I also have never had a problem with the power expander nor has anyone I know. What are you doing to the wire?

The old ones had problems but the newer ones seem to work just fine from what I have heard.

Tabor: look at the support threads. there have been at least 5 or more complaints about problems with the wires on the power expander. The new ones are better, but if the regular wire is fine then why do all rc components have silicone wire?

You can most certainly twist an axle with a vex motor i have seen it done dozens of times.

https://www.google.com/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&cad=rja&uact=8&docid=vBwQTEI2oh5NeM&tbnid=Uusfn5u538UICM:&ved=0CAUQjRw&url=http%3A%2F%2Fwww.vexforum.com%2Fshowthread.php%3Ft%3D75022&ei=xXxeU6WEJ6ecyQGFuYG4Dg&bvm=bv.65397613,d.aWc&psig=AFQjCNGYeZaPukKSDaNFPu52FL1Rl5hwCA&ust=1398787631588669

I was just saying that to get the most performance it would be optimal to have the larger shafts into the motor.

Obviously you don’t understand how to answer respectful or in a constructive way…
but this is not the place for that.

There’s plenty of torque to cause twisting, but maybe not on the initial shaft load out of the motor. Plenty of folks can show their twisted shafts out there but how many came from the motor shaft?

You have about 10 in-lbs being sent from the motor but when the force is sent over a long shaft length, even that little amount can cause some deflection. The area of the shaft profile determines the angular twist along with the material and length from force applied to force transferred…

Doubling that profile of the shaft helps a ton since the profile side measurement is cubed. The length from force application to where you hold it (the gear) is only in the numerator. So increasing the cross section of the shaft helps much more.

The next shaft connected to the big gear is where you get the bigger torque. Making sure there is no length for a twist is even better (like bolting the arm to the big gear)

Here’s a good reference site. You are looking at the angle of deflection and the max stress before it is no longer elastic but becomes permanently deformed (and starts to look like a drill bit).

http://www.engineeringtoolbox.com/torsion-shafts-d_947.html

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As for the power expanders, there were some posts about how the power wire is a bit rigid and can come frayed easily at the base causing you to have a busted power expander. So treat it gently and don’t twist it around too much. Zip tying the power expander power wire to a standoff helps keep it in place.https://farm9.staticflickr.com/8237/8511003123_0e6b4df653.jpg](https://flic.kr/p/dY67Ha)

Thanks for the link. You articulated what i was trying to say much better than i did. Thanks :slight_smile:

The community predicted their own needs. Our development team just makes the products the community asks for (mostly - some we make because we thought of them before the community and decided they’re really awesome ;)).

Everyone should note, the VEX EDR product design cycle is 100% separate from the VRC Game Design cycle. We don’t go through the “what items will teams need to be successful?” thought process. In general, we just do what we can to make sure the VEX EDR system is as capable as possible.

Regarding the new HS Shafts – they’re not needed for the initial reduction off the motor, and as such not designed to go there. The higher torque carrying and bend resistance is needed mainly for reductions later in geartrain.

Use the small shafts for your initial reduction, then use the HS shafts if you need them later in the gearbox.

Let us know if you have any questions. Good luck with VEX Robotics Competition Skyrise!

In all the years I’ve done VEX and see churros of shafts, they’ve always been off the motor. I’ve seen maybe a few that were on the motor, but it wasn’t common.

A few people from home directly bolt their gears onto their arms that are rotating to transfer torque through the gear instead of the shaft in their explanation to me.

It sounds like your saying the power over all coming out of a motor is enough to twist a shaft. The torque is not. I was referring the the earlier post that said the HS axles were useless because it couldn’t enter the motor.

They are fantastic in how they can be applied in applications were it is necessary while still interfacing with their low strength counterparts and using the gears we already have.

Regarding the math behind the shaft coming off a motor, the predominant equations are Theta = LT/(KG) and Max Stress = T/Zp.

T is the torque

Zp is the Torsional modulus. For a square, Zp = 0.208*a^3, where “a” is the length of a side of a square shaft. In our case a=0.125"

L is the length of the shaft

G is the shear modulus. For our steel that is 10.9 x 10^6 psi

K is a constant similar to the polar moment of inertia, but for non-circular sections. For a square, K = 0.141*a^4.

The yield strength of the steel we use on the standard VEX shaft is 60,000 psi.

So, the max torque a standard VEX shaft can take is 60,000 * 0.208 * 0.125^3 = 24.375 in-lbs. The MAX stall torque of a 393 motor is 14.76 in-lbs in high torque mode.

The HS VEX shaft max torque is 60,000 * 0.208 * 0.25^3 = 195 in-lbs.

Also, for a 12" VEX shaft, the related deflections are: 27 degrees for the standard and 1.7 degrees for the HS shaft.

We felt it was not necessary for the HS shaft to interface with the motor. My recommendation, use the standard shaft at the motor.

Paul

But is that really so? Each field element is 1.12 lbs, give or take. That makes them some of the heaviest objects in VEX history, and most teams will probably set an initial goal of holding 4 or so cubes. That makes 4 1/2 lbs, a huge change from last year’s buckyballs. More experienced teams will have no problem designing a lift/intake system that works efficiently enough to surpass that. Although between the strange form factor of the cubes and their considerable weight, it will be a challenge to find that perfect balance between speed and power even for the best VEX has to offer. (Which is good :))

Mr. Copioli,

Will we see high strength shaft versions of high strength sprockets? I have a few design ideas that have I’ve done in the past that historically bent shafts because of the stress. I feel terrible for asking for new products right after a great product release, but this was literally the first application that jumped to my mind when I started designing.

Thanks,