Four-bar help needed 2

[straycatalyst]

First of all - this is for a one-off project, not a production. I'm building a remote-control plow robot, based on COTS electric wheelchair parts. The plow should be able to shovel snow, yet be simple to operate. I'm thinking of using a four-bar linkage to:
lift the shovel blade upwards at least 18 inches,
push the blade forward at least 12 inches
then tip the blade downwards.

I'm hoping to use a linear actuator for this, as I have one available to me - it'll be the variable-length bar of this assembly. The first two of the movements can be combined, but the "tip" shouldn't happen before the blade reaches the top and front of its movement.

Any ideas on how I can do this, or am I trying to get too much movement out of too limited a device?

 

[TheTick]

You could probably come up with a 4-bar movement that results in something close to what you describe.

Technically, a "4-bar linkage" does not ahave a variable length link. Perhaps what you mean is a 4-bar plus a linear actuator to control the final position?

Using the "relative pole" method, you could develop your linkage around desired positions. It takes three positions to fully determine a 4-bar linkage.

 

[ShaggyPE]

Check out the content starting on page 10 of the following link. If is a good starting point on how to lay out a 4 bar.

http://www.purdue.edu/discoverypark/PLM/SME/four-bar-linkage-synthesis.pdf

This was one of the first places I went after google searching "four bar synthesis"


-Dustin
Professional Engineer
Certified SolidWorks Professional
Certified COSMOSWorks Designer Specialist
Certified SolidWorks Advanced Sheet Metal Specialist

 

[zekeman]

Where do you get the force necessary to move the snow?
Also, if you plan on using a 4 bar, then surely you must understand that it will have to be rotationally controlled during the "push"phase to put the blade in close proximity to the ground. A simple mechanism won't do that.
Lots of problems here; perhaps you can provide a better explanation of your idea.

 

[PeterStock]

You need to control the vertical positon, the angle and to a lessor extend the horizontal position of the shovel. When I worked on skid steers for John Deere, we used a 4 bar linkage linked to a pair of hydraulic cylinders to raise and lower the shovel and a second set of cylinders to control the angel of the shovel. This is approximately what you are designing. Take a look at a skid steer next time you see one. Some skid steers use a simpler linkage for the vertical movement, you may be able to use that. As far as the horizontal position, on skid steers this is accomplished by movement of the vehicle, I do not see a need for something other than that with what you are trying to do. Skid steers are used a lot to shovel snow. Have you thought of doing a r/c snow blower?

Peter Stockhausen
Senior Design Analyst (Checker)
Infotech Aerospace Services

 

[straycatalyst]

I've thought about the RC snowblower, but I'm looking for something simpler to start with - that might wind up in a later version of this.

All of you have given me more to think about on this - and thank you for the link, that'll be a good place for me to begin this.

 

[PeterStock]

It's almost summer, start by making your lawnmower r/c, then add the shovel in the fall.

Peter Stockhausen
Senior Design Analyst (Checker)
Infotech Aerospace Services