VEXpro 2016

[jwfoss]

Originally Posted by Nemo

Maybe somebody can satisfy my curiosity here. Why would a sealed can motor survive a stall better than an open motor that can be cooled more easily? BAG and 9015 are roughly the same size and power, but BAG survives a stall for longer. Is it because it's sealed or in spite of that?

Edit: Is it the lack of oxygen?

I believe the largest contributing factor is the greater thermal mass of the motor.

[cgmv123]

Originally Posted by JesseK

It's funny how typing 'cement v' into google will auto complete that exact search, and yet it's the 4th link down before there's any reasonably short explanation for what the difference between the two is. And yet even after reading that simple and short explanation, I have already forgotten if concrete is used in cement or vice-versa, and which one is limestone-based vs just water and substrates.

Since no one else has clarified for those who may not know, concrete = cement + aggregate + water.

Originally Posted by Nemo

Maybe somebody can satisfy my curiosity here. Why would a sealed can motor survive a stall better than an open motor that can be cooled more easily? BAG and 9015 are roughly the same size and power, but BAG survives a stall for longer. Is it because it's sealed or in spite of that?

Edit: Is it the lack of oxygen?

The 9015 (like most other open motors) is air-cooled. The motor spinning drives a fan that draws air through the body of the motor. At stall, the fan doesn't spin, so the motor doesn't cool nearly as well.

The BAG (like the CIM and the Mini-CIM) isn't cooled per se. Rather it's case has a high thermal mass and the internals can take more heat than the internals on an air-cooled motor.

[Aren Siekmeier]

Originally Posted by Nemo

Maybe somebody can satisfy my curiosity here. Why would a sealed can motor survive a stall better than an open motor that can be cooled more easily? BAG and 9015 are roughly the same size and power, but BAG survives a stall for longer. Is it because it's sealed or in spite of that?

Edit: Is it the lack of oxygen?

I believe it's nothing more than the mass. The BAG motor has almost 50% more than the 9015 (320 g vs ~220 g). The CIM and miniCIM obviously have a much bigger advantage over the likes of the 775pro, about 3x.

EDIT: Wow I need to stop refreshing like it's 1995.

[JVN]

Originally Posted by Nemo

Maybe somebody can satisfy my curiosity here. Why would a sealed can motor survive a stall better than an open motor that can be cooled more easily? BAG and 9015 are roughly the same size and power, but BAG survives a stall for longer. Is it because it's sealed or in spite of that?

Edit: Is it the lack of oxygen?

Nemo,
jwfoss, cgmv123, and Aren Sikmeier nailed it.

I didn't mean to be unintentionally confusing, but the OTHER motors sold as part of VEXpro (which all happened to be sealed) are much more comfortable in a stall situation.

You can see the individual performance at motors.vex.com

If you're speaking in gross over-simplifications and generalities:
"Air-breathers like running fast, and don't handle high-load, low-speed very well."

Sometimes gross over-simplifications are good enough for FRC.

-John

[Ari423]

On the VersaDrop, does anyone know how the pancake cylinder is connected to the module? It looks like it just pushes on that standoff with nothing actually connecting them together. I would imagine this is not the case. If it is the case, how does the piston not slip and miss the standoff? If it isn't the case, how does the cylinder bend with the standoff as it turns around the circle? Or is this not a major issue?

[cadandcookies]

Originally Posted by Ari423

On the VersaDrop, does anyone know how the pancake cylinder is connected to the module? It looks like it just pushes on that standoff with nothing actually connecting them together. I would imagine this is not the case. If it is the case, how does the piston not slip and miss the standoff? If it isn't the case, how does the cylinder bend with the standoff as it turns around the circle? Or is this not a major issue?

When I asked this a few years ago, here's the answer Aren gave me.

I'd assume the answer is somewhat similar here-- the arc motion is so short, and the cylinder and bar are very well defined, so it isn't necessary to connect the two.

[AllenGregoryIV]

Nick has it right. If you have omni wheels floating, you can just leave them and they won't hurt your driving. If you float traction wheels you would probably need to add a spring to raise the module to keep it from scrubbing during turns.

[GeeTwo]

Originally Posted by cadandcookies

When I asked this a few years ago, here's the answer Aren gave me.

I'd assume the answer is somewhat similar here-- the arc motion is so short, and the cylinder and bar are very well defined, so it isn't necessary to connect the two.

Originally Posted by AllenGregoryIV

Nick has it right. If you have omni wheels floating, you can just leave them and they won't hurt your driving. If you float traction wheels you would probably need to add a spring to raise the module to keep it from scrubbing during turns.

I think that it is necessary to raise the omni wheel, because it is geared twice as fast as the fixed wheel; it would be spinning against the carpet whenever you were driving in traction generating heat and wearing down the wheel. In Aren's previous answer, he refers to a spring lifting the moving wheel up. I don't see one in the assembly directions, but it may be implicit in the way pieces fit.

[AllenGregoryIV]

Originally Posted by GeeTwo

I think that it is necessary to raise the omni wheel, because it is geared twice as fast as the fixed wheel; it would be spinning against the carpet whenever you were driving in traction generating heat and wearing down the wheel. In Aren's previous answer, he refers to a spring lifting the moving wheel up. I don't see one in the assembly directions, but it may be implicit in the way pieces fit.

It won't really wear the wheels since there is no down force on the wheel other then the weight of the module itself.

[Mr V]

Originally Posted by Nemo

Maybe somebody can satisfy my curiosity here. Why would a sealed can motor survive a stall better than an open motor that can be cooled more easily? BAG and 9015 are roughly the same size and power, but BAG survives a stall for longer. Is it because it's sealed or in spite of that?

Edit: Is it the lack of oxygen?

Thermal mass. A fan cooled motor is designed as a fan cooled motor and if it is operating at zero or low rpm the fan does not cool the motor. A sealed motor on the other hand is designed without forced air cooling in mind so while operating at 0 or low rpm will cause it to heat up more than normal it is still operating as designed, ie w/o the benefit of a fan cooling it.

The fan cooling is what allows a motor to have a higher power to weight ration vs a sealed motor.

[R.C.]

We now have 775pro's in stock. They'll be shipping out all week for anyone who wants them etc..

[thatprogrammer]

Has anyone tried using the new Poly carb tubing for prototyping? Curious how strong it is.

[s_forbes]

Regarding motors.vex.com:

The link for the locked rotor stall test data exists for all of the motors, but returns a 404 for the CIM and BAG motor. The data seems to exist for the other motors... Is this just an error in the site? (obligatory "fix plox")

[Grant Cox]

Originally Posted by s_forbes

Regarding motors.vex.com:

The link for the locked rotor stall test data exists for all of the motors, but returns a 404 for the CIM and BAG motor. The data seems to exist for the other motors... Is this just an error in the site? (obligatory "fix plox")

Whoops.. Thanks for pointing that out! This has been fixed.

For future reference, you can also let us know about website errors by emailing prosupport [at] vex [dot] com directly - you will likely receive a result quicker than by posting on Chief Delphi!

[Akash Rastogi]

Originally Posted by R.C.

We now have 775pro's in stock. They'll be shipping out all week for anyone who wants them etc..

Amazing pricing on these, RC.