Deuce Tailgate Assist

[rustystud]

Hi Rusty

This and its precursor thread are great, I've read each installment and await the source of the perfect springs. I have a modified M35 dropside cargo bed on my CMP 3 ton. The dropsides make the truck just so useful.
When I got the bed it had been sitting and the hinges were all very stiff. Had to use long drift on the air chisel to drive out the pins to remove sides and tailgate, to adjust the width of the bed to fit my truck, sliced 10" out of the length of the bed. While they were off clean all of the hinge rolls back to bare bright and shinny inside. Made new pins and when reassembling coated the inside with anti seize compound. Greatly reduced the effort to raise the sides and tailgate. But as you mention they get noticebly heavier as we age.

Even if the springs do not totally balance the weight of the tailgate if the reduce force by 50% it would be a great improvement.

Has anybody put gease fittings on the pins or hindges? When I was making new pins I thought about lline drilling the pins and putting grease fittings on the ends.

Cheers Phil

I just used a heavy grease on mine. Since there is no seals to keep the grease in having a "zerk" fitting to replenish the old grease might be a good idea. I almost did for mine but since I'm still in the modification stage I thought I would wait and see. I also went with "stainless steel" pins and shaft so no more rusted together parts.

 

[rustystud]

Here's a couple of diagrams I came up with to make a Hydraulic ram system for opening and closing the tailgate.
Maybe some of you engineers out there can look at this and tell me if it would work ?

View attachment 720371View attachment 720372View attachment 720373

The first two are of the same design. The first shows the tailgate in the up position and the second shows the tailgate in the down position. The third is a totally different system I thought might work too.
I'm totally aware that the dimensions are all wrong and the angles would be different for the ram in the retracted position versus the deployed position, but is the "concept" workable ?

No comments from any engineers ? I was hoping someone could give me an answer about these ideas, could they actually work ?

 

[offroadrunner]

Rusty,
I had not thought of a tailgate assist until I saw this thread, now I want one. I took a look at your hydraulic-cylinder drawings, but I don't see how they could work. The first design (drawings 1 & 2) seems to me won't work because your "welded stop bracket" won't allow the link between the tailgate and the clevis to rotate out - thereby not allowing the tailgate to open beyond horizontal (instead of all the way down). The second design may have a problem when the upper link approaches a line between the tailgate hinge and the bellcrank (sometimes called "going over-center") - where it will lose all mechanical advantage, and be unable to support or close the tailgate. It sometimes helps me to make a cardboard model on a bulletin board (with push-pins for hinges) to test my ideas - as I can then actually "see" the movements that the parts will make.
That being said, I still like the idea of a spring (less complicated than hydraulics) "assisting" in the lift. I am however, not a fan of the spring on the hinge of the tailgate (no offense intended to those designers) - because I don't want the tailgate "flopping around" when all the way down, as I sometimes drive my truck with the tailgate lowered (when I transport a group of airsoft-players, they need to load/unload too quickly and often to put the tailgate up during transport). So I have come up with an idea that uses a pivoting-link (think of the cam-shaped pulley in a compound bow) that will give maximum assist when the tailgate approaches horizontal (when it needs the most "grunt" from me), then goes over-center (assist goes away, and actually holds it open when all the way down). I think it might work with a garage-door spring, but we'll see when I get around to cutting metal. I have made one of my cardboard models though (and if I can figure out how to upload pics, I'll share), and I don't yet see why it won't work.
Cheers,

 

[offroadrunner]

Here's what I was thinking (hopefully you can see what I'm thinking from the pics I hope will upload)...

Upper red pin is anchored to the bed-side (would have to be removable for dropsides); lower red pin is the tailgate's hinge. Blue pin is to connect one end of spring to pivot-link (other end of spring would attach to bed-side).
The first photo shows the closed tailgate - the spring would have no/very-little tension.
The second shows the point where the spring would be giving maximum assist.
The third is where all assist goes away (even though the spring is at max tension).
The fourth is over-center, and the spring actually holds the tailgate DOWN.
Cheers,

 

[CMPPhil]

Hi Bob

Like your force analysis with the card board pin model. Agree that as the force passes directly through a pivot point it will not work. A two piston approach might over come this.

Cheers Phil

 

[tobyS]

How about the spring/shock devices that hold hoods and rear gates on cars? Those have rather long stroke and with an arm, can be positioned strategically to go over center.

I'm making a dump bed out of mine, so wondering about a fold around wing, like a 929/817 dump truck.

The spring designer has not got back with me yet.

 

[porkysplace]

No comments from any engineers ? I was hoping someone could give me an answer about these ideas, could they actually work ?

The one thing I would look at is using air cylinders instead of hydraulic , the truck has easy access to air and 99% of commercial dump trucks that have power tailgates are air operated.

 

[rustystud]

The one thing I would look at is using air cylinders instead of hydraulic , the truck has easy access to air and 99% of commercial dump trucks that have power tailgates are air operated.

I was thinking about that also since I own several air cylinders that would handle this job. I just need to know if the basic concept is sound before I start cutting up my truck. I also own a tailgate lift pump system that would work, though it is 12 volts instead of 24 volt.
I have all the parts now to finish the "spring assist" system. The weather though has not been friendly lately. Constant rain and cold temperatures has kept me inside. I'm still getting over the pneumonia and my lungs cannot take the rainy cold weather. I go outside and then start coughing my lungs out. Hopefully this coming weekend will be sunny and warmer and I can finish the tailgate project.

 

[rustystud]

This weekend I finished my tailgate assist system. It closes great ! Just one hand easily closes the tailgate. The one issue it has, is it will not go down far enough. It needs weaker springs. The problem is these where the weakest ones I could find in this style. I suppose I could eliminate one spring, but that would look weird and cause undo strain on one side of the tailgate.

 

[offroadrunner]

A different approach

I thought I'd finally add a writeup with how I decided to solve this problem on my truck. While Rusty's approach works, I was not fond of the way that it failed to allow the tailgate (TG) to go all the way down (180 degrees - instead of the 90 or so that the horse trailer springs he used were designed for), or made it rather "bouncy" if it did. Since I sometimes need to drive my truck with the TG in the down position, I needed a different solution.

What I finally came up with is unfortunately a bit heavier/more complex, but hides most of its components up under the bed floor (all except for one cable and pulley only visible in one rear corner inside the bed, and five 1/4" or 5/16" nuts visible from the outside), is easily disconnectable (e.g.: if dropping the side is needed), can be modified for more/less assist as desired (by swapping springs), and provides its greatest assist when the TG is near horizontal (when I most need it) with the swing-assist diminishing to zero as the TG approaches either vertical position.

This design utilizes a tension-type garage-door spring, a couple of small pulleys, and a wire cable (all available from HD or Lowes); then I had to fabricate a lever-arm, some brackets and connection-links to make it all work (I hope to attach photos of most of the parts before and after mounting to illustrate). Fortunately, none of the parts were difficult to fab - just took a lot of measuring and staring at the underside of the truck to get everything to fit the way I wanted.

Here's how it works: Under the bed, one end of the spring is anchored to the far right of the bracket where the right-rear mud-flap supports are mounted. The moving end of the spring (in the area above and between the frame-rails) is then connected to the cable with a link that also is supported by a lever arm. The lever-arm in the middle (mounted against the inside of the rear-face of the bed) serves two purposes - to support the moving end of the spring (to keep it from bouncing around while driving), and to increase the stretch of the spring (thus its assist) during the part of its travel corresponding to the horizontal portion of the tailgate's arc. From the lever arm link, the cable passes to a pulley in the left rear corner of the bed - which turns it up (through a 1/2" slot I cut in the left rear corner of the floor) to the second pulley (attached to the inside of the rear of the bedside), then to a bracket on the tailgate itself.

With the tailgate at horizontal, I have to hold about 70 pounds of weight without the assist, but only 34 pounds with it (which makes it not much heavier than my 3/4-ton pickup's TG). That was with the lowest-rated (100#) spring I found at the hardware store; they also had 140# rated springs - in case I need more assist later.

I'm fairly happy with how it turned out, and a few other folks I've shown said they liked it as well. It's now been in service for a while (and it hasn't broken in the 3 camping trips and several dozen cycles of the TG so far) - sorry it took so long to post it up, but here it is in case somebody else wants to give it a try or suggest improvements.

Cheers,

 

[rustystud]

I thought I'd finally add a writeup with how I decided to solve this problem on my truck. While Rusty's approach works, I was not fond of the way that it failed to allow the tailgate (TG) to go all the way down (180 degrees - instead of the 90 or so that the horse trailer springs he used were designed for), or made it rather "bouncy" if it did. Since I sometimes need to drive my truck with the TG in the down position, I needed a different solution.

What I finally came up with is unfortunately a bit heavier/more complex, but hides most of its components up under the bed floor (all except for one cable and pulley only visible in one rear corner inside the bed, and five 1/4" or 5/16" nuts visible from the outside), is easily disconnectable (e.g.: if dropping the side is needed), can be modified for more/less assist as desired (by swapping springs), and provides its greatest assist when the TG is near horizontal (when I most need it) with the swing-assist diminishing to zero as the TG approaches either vertical position.

This design utilizes a tension-type garage-door spring, a couple of small pulleys, and a wire cable (all available from HD or Lowes); then I had to fabricate a lever-arm, some brackets and connection-links to make it all work (I hope to attach photos of most of the parts before and after mounting to illustrate). Fortunately, none of the parts were difficult to fab - just took a lot of measuring and staring at the underside of the truck to get everything to fit the way I wanted.

Here's how it works: Under the bed, one end of the spring is anchored to the far right of the bracket where the right-rear mud-flap supports are mounted. The moving end of the spring (in the area above and between the frame-rails) is then connected to the cable with a link that also is supported by a lever arm. The lever-arm in the middle (mounted against the inside of the rear-face of the bed) serves two purposes - to support the moving end of the spring (to keep it from bouncing around while driving), and to increase the stretch of the spring (thus its assist) during the part of its travel corresponding to the horizontal portion of the tailgate's arc. From the lever arm link, the cable passes to a pulley in the left rear corner of the bed - which turns it up (through a 1/2" slot I cut in the left rear corner of the floor) to the second pulley (attached to the inside of the rear of the bedside), then to a bracket on the tailgate itself.

With the tailgate at horizontal, I have to hold about 70 pounds of weight without the assist, but only 34 pounds with it (which makes it not much heavier than my 3/4-ton pickup's TG). That was with the lowest-rated (100#) spring I found at the hardware store; they also had 140# rated springs - in case I need more assist later.

I'm fairly happy with how it turned out, and a few other folks I've shown said they liked it as well. It's now been in service for a while (and it hasn't broken in the 3 camping trips and several dozen cycles of the TG so far) - sorry it took so long to post it up, but here it is in case somebody else wants to give it a try or suggest improvements.

Cheers,

Could you give us a drawing ? I'm having a hard time trying to wrap my head around this idea. Words are great but pictures and drawings are better !
Thanks.

 

[offroadrunner]

trying to add pictures

Sorry, when I added the pictures last night, I used the "manage attachments" feature - which attached the pictures as thumbnails - they looked OK (and I can open them fine on my laptop), but I can't seem to open them when I view this thread on my phone. Maybe that's the wrong tool, or maybe 9 pictures is too much at once? - guess I'll try a different ("Insert images") method here.

The first two show two positions of the TG (max-assist and vertical-down) and the cable (above the bed floor) passing through the slot in the left/rear corner of the floor, through the upper pulley, and to the mid-point of the TG.
The next two are views (closeup near frame, and from just inside the floor's edge) from UNDER the bed floor (from the right side of the truck - both taken when TG was UP, with the spring not stretched) showing the spring - with its moving end attached to the lever-arm and the cable, and the cable routed to a pulley in the far left corner (which routes the cable UP through the slot in the bed floor). You might be able to see some small scratch-marks made on the underside of the floor (in the right side of the pics) of the arc the lever-arm end-link follows when the spring is stretched by the attached cable.
I'll attach the pictures showing some of the parts (before mounting to the truck) - in the next post.

 

[offroadrunner]

OK - it looks like that may have worked - so here's the pics of the parts I used (before attachment to the truck):


The first one shows the pulleys (small one - under bed, longer bracket attaches to bedside), and the link between cable and spring - before I decided to make a clamp (of two flat pieces of aluminum) to hold the free (adjustable) end of the cable to go here (and use the loop-end on the tailgate instead).
The second shows the addition of this cable-clamp piece and its attachment to the end of the lever-arm.
The third is the bracket and eye-bolt that attaches the fixed end of the spring to the outer edge of the right mud-flap support bracket (under the bed).
The fourth is the lever-arm assembly as though you were looking from the ground up towards the bed (the base at the bottom of the pic attaches to the inside of the rear face of the truck bed).
Last pic is just another view of most of the pieces.
Hope that helps.
Cheers,

 

[77 AMG]

If you wouldn't mind, could you post up measurements for the cable length, your arm that you designed and the spring length?

 

[offroadrunner]

Sure. The cable length isn't super critical - that's why I only used a loop on the TG end (for ease of removal, just pull the pin out of the TG bracket); the end that connects to the link at the end of the lever is clamped between a couple pieces of 1/4" aluminum so I could take up the slack there - as well as with the threaded end of the eye-bolt (at the fixed end of the spring - also used to "pre-tension" the spring a little). I think I wound up cutting the cable less than 72" from the loop, and I still have a couple of inches of the end sticking out of the clamp.

I made the lever arm with an end piece that could be attached at three different lengths (12", 13", and 14" measured center-center, inner pivot pin to the hole that the link goes through) - in case I needed to adjust once installed. I wound up using it at the longest (14"), and it might have been OK another inch longer (a bit more stretch at max-assist, but probably not worth making a new end piece). It might be hard to tell from the pics, but the end piece also "jogs" to one side by an inch (to allow clearance for the link as the arm articulates).

The spring is 28" from the outsides of the eyes on both ends. I'm pretty sure it's advertised as a 28" 100-pound door spring. Since I only needed it to stretch about 22" max - I figured that was OK.

Hope that helps.

Cheers,

 

[77 AMG]

That helps tremendously! Thank you, offroadrunner.

 

[77 AMG]

That helps tremendously! Thank you, offroadrunner.