Breakaway torque 1

[Trommel]

From the outset I am not a fluid engineer.

I am investigating a process which requires a flywheel to be turned, In order to build up that initial momentum to get the flywheel turned a high torque is required and hence there is a very high pressure drop across the motor.
The motors we currently use are simple gear motors which are specced for that breakaway torque but do not for the running torque.

I was looking at variable displacement motors which I think can provide that initial torque and give a much more reduced running pressure.

Does anyone have any experience in dealing with this type of breakaway torque situation?

 

[Trommel]

Okay Gkranz

First off the system will be getting redesigned. How? we don't quite know yet.

What is a good starting point to redesign?

Bearing in mind the focus is on changing the hydraulic system not any other aspect.

Out of curiousity what are SOME of the applications for variable displacement motors.

 

[budt]

Trommel;

The only system I know of for a Variable Displacement Hydraulic Motor is on drives for Farm Machinery such as a Combine (Harvester) They use the Motor in full displacement in the field while harvesting and while the torque requirement is high and speed is slow and the low displacement to travel on the road from one field to another when time is short and torque is low.

This could apply to any application where torque and speed are not required at the same time and can reduce pump maximum volume drastically.


Bud Trinkel CFPE
HYDRA-PNEU CONSULTING, INC.
fluidpower1 @ hotmail.com

http://www.fluidpower1.us

 

[waross]

Hi budt;
I haven't seen an agricultural drive for quite a while now, but I remember them as using variable displacement pumps and fixed displacement motors.
Are they still using variable displacement pumps and adding the variable displacement motors for a greater speed range, or am I completely out of it??
Thanks
respectfully

 

[budt]

The last ones I worked with was helping a Machine Shop add 4WD to some combines in Illinois 8 years back during some wet fall weather. They had Varaible Motors and he put wheel motors on the steering wheels and tied them in series with the drive wheels. Also some valves to bring the eteering wheels in or leave them out and free wheel.

Also some of my studesnts have farms as a hobby (second job) and they mention these drives when we get to Hydro-Statics.


Bud Trinkel CFPE
HYDRA-PNEU CONSULTING, INC.
fluidpower1 @ hotmail.com

http://www.fluidpower1.us

 

[Gkranz]

Trommel,

Quote - What is a good starting point to redesign?
Answer - At the load, always at the load and work backwards.

Quote - Bearing in mind the focus is on changing the hydraulic system not any other aspect.
Answer - I have no idea what this statement means, what other aspect?

Buds quote pretty much states it correctly - This could apply to any application where torque and speed are not required at the same time…

List – drill, vehicles, winches, tunnel boring machines, cable laying machines, etc.

Again, you are trying to associate a variable displacement motor to a specific application, when in fact we as designers do not think in those terms. Good designers know the functions, response, performance and little quirks between manufactures of every hydraulic component. Much like putting a puzzle together using the same pieces and making a different picture every time we do it.

Quote - First off the system will be getting redesigned. How? we don't quite know yet.

Answer – Sounds like to me you do not have the in-house people with the experience and knowledge to solve this problem, you need to get some help. Just because you are an engineer does not mean that every problem they throw on your plate is a problem you can solve without some help. Will this forum help you design a circuit? A resounding NO, you will get all kinds of goofy ideas and waste your time trying to figure out good from bad ideas. There is no shortage of people who want to fix or design something; it is like a hobby for them.

You could try FREE engineering from a fluid power distributor in lieu of buying their products, however you need to try this at least once to see how bad an idea this is, but that is for another post at a later date. Best of luck on your project.

Best regards, Gkranz


Westerndynamics.com

 

[EdDanzer]

Trommel,
The best starting point is to post some answers to my May 24 post.

Variable displacement motors are used in almost any application that requires variable speed, variable load, or energy conservation. Mobile equipment travel and swing drives, and conveyors to name a few.

Don’t expect any help if you don’t provide a technical basis for help.