# How do I calculate the velocity of the piston?

I have a system with a motor connected to the trapezoidal lead screw. The lead screw is connected to the tube which is connected to the piston. The piston has to pump 1000cc oil against a pressure of 20 bar into the bladder.

Well , first I found out the force on the piston at 200m which is 10054 N. I calculated the torque considering 20 bar+1000 Pa of extra pressure to push the oil into the bladder at 20 bar. The resulting torque was calculated as 12.6 Nm (this seems a lot to me and hence asked the question on this forum). Once I know the RPM of the motor, I can calculate the piston velocity (using stroke length ,lead and RPM)

Is this approach correct? Am I doing something wrong? If not, then which motor should I use?

• Piston diameter: 80 mm
• Pitch of the screw: 3mm
• Lead angle: ø = 9.38˚
• Helix angle: α = 6.8˚
• Time to pump the oil into the bladder at 20 bar: 12s ± 3s (This can increase but I am trying to keep it as low as possible)
• The orifice diameter is 17.77mm

• Velocity needs time and you don't say... May 7 '18 at 11:51
• Welcome to Engineering! This looks like a "homework question" (even if it isn't actual homework). In order for such questions to be answered in this site, we need you to add details describing the precise problem you're having. What have you tried to solve this yourself? Please edit your question to include this information.
– Wasabi
May 7 '18 at 12:49
• Your edit is useful, but doesn't solve the key issue with your question, which is that we don't know what you've done to try to solve this. Please edit your question to show us what you've tried.
– Wasabi
May 8 '18 at 10:05
• @MarcClintDion Yes, that is a part of the question. Second, don't assume that the OP is a male, it can be anyone May 9 '18 at 5:54
• whats the stroke? Where does the initial pressure come from? May 10 '18 at 17:03