JVN calc with two motors in Linear Mechanism

#1

I have been using JVN calc to test the speed and gearing that we should have for out elevator, and we are using two RS-775s.
How should I add up the two motors in the “Linear Mechanism” calculation? It only allows the specs for one motor to be inputted. So far I have been doubling the stall torque, but I don’t know if that’s necessarily correct. It seems like it as, as free speed shouldn’t change. Do I double the current too?

#2

Here is how we did our calculations for our lift with 2 775-18s.
We used the “Intake” sheet with the configurations seen in this image.





#3

Ah ok. That should work great.
Thank you!

EDIT: That doesn’t seem to work in the version that I have as there is no option for extra motors. Where can I find the version the you have?
DOUBLEEDIT: Nevermind, I just made the sides of the intake 2 instead of 1.
ANOTHEREIDT: That doesn’t seem to work either as the stall load doesn’t change…

#4

When using two of the same motors, the torque provided doubles while the free speed remains the same. Seems like you got it right. I have a few older versions of the Jvn calc backed up on my computer if you’d like me to dig them up tomorrow.

#5

Which version are you using. The most recent one I have found allows you to put the number of motors per gear box, assuming that you are using 2 of the same motor. Don’t forget to adjust the efficiency based on your chosen transmission and add some extra weight to account for overcoming the sticktion if you are using sliders rather than rollers.

#6

That is correct.

It seems like … free speed shouldn’t change.

That is correct

Do I double the current too?

Yes, and the free current as well.

#7

I believe I’m using the 2013 version. Search for it here on CD, and see if you can find it. I’m not where I can send you a copy of it, but when I get home today I will see if I can email you a copy.

#8

Paper: JVN's Mechanical Design Calculator (2013 version)
http://www.chiefdelphi.com/media/papers/2059 (2008-2011 versions)
http://www.chiefdelphi.com/media/papers/1469 (2004 version)

#9

Yes, as Ether said. The Banebots motors will have to be on separate motor controllers and therefore separate breakers, so the current draw on each breaker is the original value.

#10

Okay, that looks good then. Thanks for all the help!
I think I’m using 2011.