Recent content by deadstar33

Thanks

I see. Is there an equation that relates the mass moment of inertia to the torque in some way then? I calculated the mass moment of inertia of the cylinder and shaft together to be 0.033kgm^2.

Yeah that's what I meant. I'm guessing the torque will then depend upon how fast I'm accelerating it from 0 to 100RPM? i.e. if I want to be able to accelerate it from 0 to 100 in 1 second it would require more torque than the same increase over 10 seconds. If that's the case, it presumably...

1. The diameter of the shaft is 0.017m (17mm) and the diameter of the cylinder is 0.16m. 2. Sorry you're right, it's 6.28 rad/s at 60RPM and ~10rad/s at 100RPM. 3. Do you mean like air resistance? Or friction due to having imperfect bearings on the shaft? I don't have much experience with...

Hi, I'm trying to choose the right motor for a test rig I've built. I have a shaft attached to a cylinder that weighs 6kg, and I need to know how much torque would the motor I'm getting need to be able to produce in order to rotate the cylinder at 100RPM. My attempt: Torque = Force x r...

Okay, thanks everyone for the help!

To be honest I only really need a very rough estimate, a ballpark figure, of how much the liquid would heat up. If it is assumed as Chet says that all of the heat stays in the fluid does anybody know of any equation or correlation I could use to get an idea? I was thinking there might be a way...

Hi, As part of an experiment I am doing I have a small uniform circular disc that is submerged in 20ml of a liquid and is spinning at 2000rpm for 60 seconds. The disc is 1mm thick and 40mm in diameter. I am trying to see what effect the spinning disc has on the growth of cells that are in the...

Yeah it's a smooth cylinder and the water is initially at rest so it will move with the cylinder as it rotates. The viscous friction should be a tiny load. Cheers, that was very helpful.

My apologies, you already said that the load is so small that it shouldn't be very significant. That's okay then. So can I just ignore the power of the motor and look at the speed rating?

Oh okay, I though the weight of the spindle itself would act as a load on the motor seeing as it weighs nearly half a kilogram? And the spindle will just be submerged in water and rotating at different speeds between 0-3200RPM, so there's no additional load other than the viscous resistance of...

Hi all, Description of Problem: I need to buy a motor to drive a custom-made spindle that I have made but I'm not completely sure what wattage the motor needs to be. Basically the spindle is just a hollow cylinder (closed on all sides) of stainless steel attached to the end of a shaft - the...

Let's just say for argument's sake that I can't change the design. Given this, do you know any formula I could use to calculate the shear stress between the disks? Or even a mathematical function I could use to calculate the shear stress at any given point between the discs? (That way I could at...

Hi mfb, Thanks for the reply, that makes sense. So just to give you more details, I have created a CFD simulation of the problem and looked at the velocity of the flow between the discs. The velocity is at a max at the disc surfaces (around 0.3 m/s) but then drops very dramatically to...

Hey everyone, As part of my PhD project I'm trying to design a small bioreactor in which I will be growing animal cells. This bioreactor will basically consist of a hollow cylindrical vessel that has an impeller in it which will keep the liquid medium in the vessel well mixed. The impeller I am...