Anyone have a Linear actuator FEL? Like it or no? Why?

[DennisThornton 4,769]

Handy Don has pointed out a serious difference between a hydraulic cylinder and an electric actuator that never occured to me at first.  Years ago I saw actuators used in place of hydraulics but actuators won't take the beating that hydraulic cylinders will!  Don't replace your cylinders on your FEL will linear actuators and push against them.  OK for lifting a load but not the other stresses a FEL needs to take.  But I still think that there is hope for this design, whether manual or assisted or modified as many prototypes need.

[wallfish 15,912]

8 hours ago, Handy Don said:

(in @wallfish's schematic above, if you ram it into a dirt pile there aren't springs absorbing that "tipping" force, it's directly "pulling" on the actuator so it'll just strip the gears in the actuator)

Maybe I'm missing something but... Push pull of an actuator is accomplished by an acme screw turning a threaded "nut" similar to something like a C clamp so the impact or pull force is equivalent to pushing a nut down a bolt without spinning it. It's striping limit of the threads is limited by the thread contact area and or the material used for the "nut" part. Some actuators use a spring loaded threaded piece designed to skip threads when too much force is applied and some are made of plastic but the forces cannot spin the acme screw to damage the gears. Maybe it's possible to ram that acme screw out the back or pull the clip out holding the acme screw in place. They are NOT designed for impacts and can certainly damage it but a good quality actuator should be able to handle normal use for this application. The pivot point of the blade will take the majority of the impact forces and that mechanical leverage point up on the back will reduce the forces quite a bit.  As you know I'm not an engineer but just trying to understand as that's how learning goes. Maybe a spring added to the end or bottom of the actuator could accomplish a tripping of the blade?  

[ebinmaine 62,986]

10 minutes ago, wallfish said:

The pivot point of the blade will take the majority of the impact forces and that mechanical leverage point up on the back will reduce the forces quite a bit.  As you know I'm not an engineer but just trying to understand as that's how learning goes. Maybe a spring added to the end or bottom of the actuator could accomplish a tripping of the blade

The way I'm understanding this, if the pivot point at the top is built correctly and there are stops at the bottom for the flat clamshell blade to sit against the plow... There should be minimal damage possibilities for the actuator.  

[wallfish 15,912]

My drawing used an actuator for tilt up and down of the blade. Not completely necessary but does add some advantages over a fixed position. The clam shell can be pulled by a rope from the lever on the top or use of an actuator. This design isn't intended for scraping up or carrying 300 lb loads of dirt but more of a light duty carry tool for mulch and stuff like that 

[ebinmaine 62,986]

40 minutes ago, wallfish said:

light duty

My original intent for something like this was to move small amounts of something like rock or sand or as you said, mulch.

 

I never did get around to building it because I had a trailer and then was given another one and I only had one plow blade and didn't want to screw something up.

 

Now, not having ever tried it I can't say for sure but I have a strong feeling that with a reasonable amount of strength and some good leverage on the rope you're talking about you could pretty easily pick up and move around 100 to 150 lb. 

[DennisThornton 4,769]

1 hour ago, wallfish said:

Maybe I'm missing something but... Push pull of an actuator is accomplished by an acme screw turning a threaded "nut" similar to something like a C clamp so the impact or pull force is equivalent to pushing a nut down a bolt without spinning it. It's striping limit of the threads is limited by the thread contact area and or the material used for the "nut" part. Some actuators use a spring loaded threaded piece designed to skip threads when too much force is applied and some are made of plastic but the forces cannot spin the acme screw to damage the gears. Maybe it's possible to ram that acme screw out the back or pull the clip out holding the acme screw in place. They are NOT designed for impacts and can certainly damage it but a good quality actuator should be able to handle normal use for this application. The pivot point of the blade will take the majority of the impact forces and that mechanical leverage point up on the back will reduce the forces quite a bit.  As you know I'm not an engineer but just trying to understand as that's how learning goes. Maybe a spring added to the end or bottom of the actuator could accomplish a tripping of the blade?  

Yeah, it's just that hydraulics will handle shocks well over their lift capacity where the same rated linear could be damaged.  Both will lift at rated but the cylinder will take more shock.   A 200lb rated linear actuator lifts a 150lb rear blade with ease until the blade hits a boulder and shoves a sudden 1000lbs upward against screws meant for 200lb.  Enough force might bend a hydraulic rod or blow a hose as well.   I suppose a weak link like a shear pin could be incorporated to deal with overloads.

[Handy Don 10,567]

4 hours ago, wallfish said:

Maybe I'm missing something but... Push pull of an actuator is accomplished by an acme screw turning a threaded "nut" similar to something like a C clamp so the impact or pull force is equivalent to pushing a nut down a bolt without spinning it. It's striping limit of the threads is limited by the thread contact area and or the material used for the "nut" part. Some actuators use a spring loaded threaded piece designed to skip threads when too much force is applied and some are made of plastic but the forces cannot spin the acme screw to damage the gears. Maybe it's possible to ram that acme screw out the back or pull the clip out holding the acme screw in place. They are NOT designed for impacts and can certainly damage it but a good quality actuator should be able to handle normal use for this application. The pivot point of the blade will take the majority of the impact forces and that mechanical leverage point up on the back will reduce the forces quite a bit.  As you know I'm not an engineer but just trying to understand as that's how learning goes. Maybe a spring added to the end or bottom of the actuator could accomplish a tripping of the blade?  

Agreed. I simplified by using the term "gears". Yes, it is an Acme screw and yes, the damage would be as you describe. It is possible to carefully design to avoid having impacts be felt by the actuators but "carefully" is the operative word here (stops when closed, the shear pin Dennis mentioned, or a spring-tensioned release are among the options).

You have to dig into the specs for actuators' impact force ratings since most don't quote one (and the vast majority of the ones I did find a rating for had it identical to the push/pull rating, meaning NO extra impact capability). 

And after load has been settled, this still leaves speed, size, and weatherproofing to be considered. 

I do fully agree that this can be done with actuators. Just not casually or well or reliably with cheap ones. My guess is the two moderately strong and weatherproof units on the Johnny Bucket would retail for $400-450 each. That bucket package sells for $1,600. Watch its videos closely and note the careful editing to obscure the slow speed of the actuators.

[DennisThornton 4,769]

57 minutes ago, Handy Don said:

You have to dig into the specs for actuators' impact force ratings since most don't quote one (and the vast majority of the ones I did find a rating for had it identical to the push/pull rating, meaning NO extra impact capability). 

And after load has been settled, this still leaves speed, size, and weatherproofing to be considered. 

A few years back I got excited to think what all I could do with electric actuators and then the more I dug into them the more my excitement declined.

I still intend to add one to my CUT snowblower chute angle.  Too easy, cheap and low force required.  But then to weatherproof, not just water but ice.

[wallfish 15,912]

6 hours ago, Handy Don said:

I do fully agree that this can be done with actuators. Just not casually or well or reliably with cheap ones

Agreed. This is more of a work around type thing discussion for me to at minimum come up with a good design.

Anything done with actuators instead of hydraulics is definitely going to be light duty and slow.

What about using bar steel instead of springs to take the trip load impact and the actuator is then used to only tilt it and not take any impact loads?

 

 

 

[Handy Don 10,567]

Interesting take and I agree that the solution is to isolate the actuator from impact forces. Isolation is, to me, one of the attractions of the clamshell. When closed, impact is not on its lift or opening actuators but carried directly to the blade and its frame (operator responsible for fully closing before ramming, right)?! With the clam fully lifted, the blade is accessible for use, as well.

In your sketch, if the green and red linkages were perfectly aligned an impact on the blade (yellow straight arrow) would cause it to pivot (yellow curved arrow) around the axis (yellow circle) and the force would go into the pivot and into the hinge at the base of the red link. The pivot and hinge base together would exert torque on whatever frame was holding them both,

However, if the Red and Green are misaligned, even a little, then the impact is shared by the actuator, the axis, and the hinge base. The effect depends on the forces and angles involved.

It could be done like a human knee -- it bends one way easily but locks when straightened out.

So there is a lift somewhere, and this lets you tilt the blade back. Now, if there is a bucket attached to the front of this blade, how do you dump it?

[DennisThornton 4,769]

7 minutes ago, Handy Don said:

Interesting take and I agree that the solution is to isolate the actuator from impact forces. Isolation is, to me, one of the attractions of the clamshell. When closed, impact is not on its lift or opening actuators but carried directly to the blade and its frame (operator responsible for fully closing before ramming, right)?! With the clam fully lifted, the blade is accessible for use, as well.

In your sketch, if the green and red linkages were perfectly aligned an impact on the blade (yellow straight arrow) would cause it to pivot (yellow curved arrow) around the axis (yellow circle) and the force would go into the pivot and into the hinge at the base of the red link. The pivot and hinge base together would exert torque on whatever frame was holding them both,

However, if the Red and Green are misaligned, even a little, then the impact is shared by the actuator, the axis, and the hinge base. The effect depends on the forces and angles involved.

It could be done like a human knee -- it bends one way easily but locks when straightened out.

So there is a lift somewhere, and this lets you tilt the blade back. Now, if there is a bucket attached to the front of this blade, how do you dump it?

I was concerned and going to take the other approach, but now I'm thinking you are on to something.  If those "hing points" were a tad overcenter they have to take the brunt!  Maybe a good way to use linears for over their stress limits!

Gads I love this forum!  Why not?  Just a tad overcenter and take the linear out of danger?  Not sure how that I see how to do that everywhere but seem simple here!

[Handy Don 10,567]

10 minutes ago, DennisThornton said:

I was concerned and going to take the other approach, but now I'm thinking you are on to something.  If those "hing points" were a tad overcenter they have to take the brunt!  Maybe a good way to use linears for over their stress limits!

Gads I love this forum!  Why not?  Just a tad overcenter and take the linear out of danger?  Not sure how that I see how to do that everywhere but seem simple here!

Putting the green-red linkages past center alignment where the hinge is on the blade side and up against the red block (blue arrow), isolates the actuator.

Still don't see a dump option here 

[ranger 1,618]

12 hours ago, wallfish said:

Maybe I'm missing something but... Push pull of an actuator is accomplished by an acme screw turning a threaded "nut" similar to something like a C clamp so the impact or pull force is equivalent to pushing a nut down a bolt without spinning it. It's striping limit of the threads is limited by the thread contact area and or the material used for the "nut" part. Some actuators use a spring loaded threaded piece designed to skip threads when too much force is applied and some are made of plastic but the forces cannot spin the acme screw to damage the gears. Maybe it's possible to ram that acme screw out the back or pull the clip out holding the acme screw in place. They are NOT designed for impacts and can certainly damage it but a good quality actuator should be able to handle normal use for this application. The pivot point of the blade will take the majority of the impact forces and that mechanical leverage point up on the back will reduce the forces quite a bit.  As you know I'm not an engineer but just trying to understand as that's how learning goes. Maybe a spring added to the end or bottom of the actuator could accomplish a tripping of the blade?  

Any actuators I’ve had dealings with will actually (no pun intended) extend or retract if the load applied exceeds certain limits. So the thread didn’t lock like a nut and bolt  I suspect more impact damage could occur if the unit is being energised at the time of impact ie “locked”. When I have used them I wired the motor so both motor cables were connected together when “switched off “, this would effectively “brake” the motor and reduce the unwanted extension or retraction, depending upon if the load was pulling or pushing.

[DennisThornton 4,769]

1 hour ago, Handy Don said:

Putting the green-red linkages past center alignment where the hinge is on the blade side and up against the red block (blue arrow), isolates the actuator.

Still don't see a dump option here 

Just protects the actuator.  Not sure about everything else.

[wallfish 15,912]

1 hour ago, Handy Don said:

Still don't see a dump option here

See previous drawing with the clam shell for dump

[Handy Don 10,567]

1 hour ago, wallfish said:

See previous drawing with the clam shell for dump

Separate actuators for lift, tilt, and dump then.

In the design I'll get back to as soon as I stop reading and responding to posts here  I've got only a clamshell actuator. Lift is done separately.