Rear Bumper/Spare Tire Mount Thoughts

Ok, I think I now understand about the mounting height for different tires.  But since this is getting less and less generic I think the limited tire size capability will be adequate.

As for making the swing arm shorter, there are several issues.  One is the stop on the left end.  It is something like 2" high in order to effectively capture the arm, but the tailgate only clears the bumper by 1", so it has to be on the left end of the bumper beyond the tailgate.  And there's the latch - if the arm stops in the middle the latch will be under the spare tire.  So I came to the realization that the arm needed to be full width.

And the wall thickness of the swing arm was picked so that when it is fish-mouthed the full wall is there for the whole weld length, thereby making the weld strong.  However, I could downsize the A-arm walls.  And I'll look into that.  But those arms aren't an appreciable portion of the weight, so won't change the overall wight much.

More later as I have to run now......

Time for an update and a few pics.  (But, I'll admit that the other pics, like in Projects or on the website are not up to date.  )

I think I'm done and ready to have Ben start fabricating it.  The most recent changes are:

I've picked a pin-latch (Ruffstuff's R2215), but I'm having second thoughts as it has a handle that looks to be 3" across and if it were to be in the fore/aft position when the swing arm is close it'll hit the tail light.  So, I may change to one with a ball handle.

I'm going to use a Destaco latch to pull the swing arm down to the stop tightly to ensure there are no rattles and it can't come loose.  It'll be their stainless model but it'll look like this one.

The left stop, against which the arm will rest, will be made of UHMW (ultra high molecular weight polyethylene).  I'll machine it to fit once the bumper and swing arm are completed, which will let it fit snugly.

The jack, which I now have courtesy of my son and his family for an early Christmas, fits neatly on top of the tire carrier via studs that come through the holes in the jack's ladder.

Here's an overall view



Here's a view of the jack mounted.  It rests against the piece of angle on the right end, and the studs go through the holes and will be held on with wing nuts and washers.  Plus, one of the studs will be drilled to accept a small lock to deter those with sticky fingers.  

But, I just thought of a change - I think I'll replace the welded piece of angle with a piece of UHMW, and turn it around so the jack rests on it instead of the swing arm.  That way there won't be any metal-to-metal contact.  Plus, I'll make the spacers for the studs, the things that hold the jack up off the swing arm, out of UHMW and slip them over the studs.  Again, no metal-to-metal contact.




This shows the left stop.  The left/front hole in the illustration will have a 3/8" socket-head cap screw down against the land shown about 1/2 way down and threaded into the bumper.  And then the pin of the latch will come down the same hole, as you'll see in the next drawing.  Also, a 3/8" countersink screw will hold the back of it down to the bumper.




And here's the arm resting on the stop and the pin latch holding it in place.  The 3/8" SHCS will take the force of the swing arm hitting the stop, and the slippery nature of UHMW will let the arm as well as the pin for the latch slide onto it nicely w/o taking the powder coat off.

The big tube parallel to the bumper does not add strength - only weight.  The whole thing would be lighter, cheaper, & stronger if the big tube went from the pivot up to the spare mount.  If you don't want to catch/lock the arm at the pivot (which is easier), you could add smaller material going back down to the bumper for a catch somewhere.  But there is no advantage to putting it all the way at the far (driver's) end of the bumper.  It will look cleaner & have a smaller swing arc (it won't hit as many things, and it'll be easier for you to walk around it) if the latch is hidden behind the spare like the Bronco's.  Putting the spare offcenter will give you a better rear view for backing/trailering.  Putting it toward the same side as the pivot makes everything stronger, lighter, & easier.

Hmmmm, good ideas.  I'll have to think about that one......

Since there's no space above the bumper when the tailgate is down, I put the left stop past the tailgate.  And that meant that the arm had to go all the way across.  But, if the stop were on the right side, ......

However, one manufacturer of spindles for swing arms such as this was emphatic that you must cinch the swing arm down very firmly as they've had spindles and swing arms damaged when they weren't.  And the only way I can see to do that is by placing the clamp a ways away from the spindle.  But you can only get 2 1/2" left of the spindle before you are into tailgate territory if the clamp is on the right end of the swing arm.  And if you place the clamp there the tire would have about 20:1 leverage advantage on it.

However, another option would be to make the swing arm half-length and bring a piece of square tubing straight down to the swing arm, thereby closing the triangle.  And, while I can't put the stop on the bumper or it'll hit the tailgate when it opens, I could put the stop on the swing arm.  But, it would have to be a piece of plate making a positive stop, and that would give a metal/metal contact which I'm trying to avoid.

I'll think about this a bit more as maybe I'm missing something simple.  So you if see it please let me know.

I somewhat agree with Steve 83, but only somewhat.  The big tube going across is necessary, but it doesn't need to be the strongest piece of the whole frame.  The main thing it needs to do is provide a straight shot from the pivot to the latch.  To see this imagine what would happen if it wasn't there, but otherwise the whole thing was as drawn above.  If you were to put any force forward or backward on the latch (which is what it will do), that translates into a twisting moment on the arm going from the pivot up to the tire.  (the Bronco tire carrier doesn't need this because it has a pivot at the top of the fender and the latch at the top of the tailgate, so it has a straight shot from the pivot to the latch in the top tube.)  The other thing the tube across the bottom does is triangulate the whole thing which adds a lot of strength.  But as it isn't carrying most of the weight it doesn't need to be so beefy.  I'd probably do with the same tubing as the top angled pieces for the aesthetics.  But it could probably be smaller.

And I definitely would not put the latch on the same side as the pivot.  As Gary already noted, the leverage just gets nasty.  That puts a LOT more force (like 20 times as much) on both the pivot and the latch.  It won't hold up well that way at all.

By the way, here's a link to a thread on a home-built carrier a guy built recently for an early Bronco.  It has it's strong and weak points, but you might be interested in it.
http://classicbroncos.com/forums/showthread.php?t=291053

Several thoughts.  But thoughts, not answers or decisions.

Tomorrow afternoon I plan to measure my trailers to see if the long swing arm will hit anything on them.  That may be a real problem if so, and that will mean I'll have to reduce the length of the lower arm.  But, the weight of the extra 36" of lower tubing, assuming I stop it right in the middle, is 20 lbs.  And the weight of the extra 23" of the smaller tubing is 14 lbs, assuming I bring it down vertically to the lower tube.  So we are talking about a total of 34 lbs.

As for the size and thickness of the bottom tube of the swing arm, the 3 1/2" height was chosen to give the maximum resistance to rotation or twisting and still allow it to be welded easily to the 4" tall pivot.  That's because the center of the tire sits 14 3/4" above the centerline of the bottom tube, and under rapid deceleration the tube needs to resist twisting or the tire or the jack could hit the tailgate.  My limited remembrance of the structural dynamics class I took is that the rigidity goes up as the square of the height, assuming the width stays constant, and that has just been confirmed by my nephew who is a mechanical engineer.  So the 3 1/2" tube is almost exactly twice as resistant to twisting as the 2 1/2" tube.  And the thickness of the tube walls, 3/16", has been picked to allow fish-mouthing it to properly fit the diameter of the pivot on the spindle.

If I stop the lower arm in the center I could put the plastic ramp on the swing arm so it won't be in the way of the tailgate opening.  But, there's not room to put the Destaco clamp right in the center due to the receiver being there.  So I'd at least have to extend the lower arm a bit to the left of center, or put the clamp to the right of the receiver.

That carrier on the early Bronco is interesting.  I like how he captured the jack in front of the carrier so that it would be secure if the carrier were somehow locked closed - although I don't think he has that ability.  

But I don't particularly like the way he seems to be securing the carrier.  First, it appears that he only has one way - the handled bolt on the left end.  That bothers me as I want both a belt and braces approach because if that carrier gets loose it is going to cause a lot of damage. Second, what I've read says you need a strong clamp in the vertical direction to prevent the whole assembly from moving as you go down the road - or off the road.  And while that bolt will keep it from going very far, I wonder if it will allow the two pieces of metal to move in relation to each other, which will remove the finish as well as cause noise when the rust starts there.

Gary Lewis wrote

....

As for the size and thickness of the bottom tube of the swing arm, the 3 1/2" height was chosen to give the maximum resistance to rotation or twisting and still allow it to be welded easily to the 4" tall pivot.  That's because the center of the tire sits 14 3/4" above the centerline of the bottom tube, and under rapid deceleration the tube needs to resist twisting or the tire or the jack could hit the tailgate.  My limited remembrance of the structural dynamics class I took is that the rigidity goes up as the square of the height, assuming the width stays constant, and that has just been confirmed by my nephew who is a mechanical engineer.  So the 3 1/2" tube is almost exactly twice as resistant to twisting as the 2 1/2" tube.  And the thickness of the tube walls, 3/16", has been picked to allow fish-mouthing it to properly fit the diameter of the pivot on the spindle.

True and important.  But only important between the tire and the mounting points (the pivot and the latch).  I suppose the beef of the beam will help resist some of the twisting force as the left side arm is resisted by the pivot (on the right).  But I think for the most part the left side will be supported by the latch and the right side by the pivot.  So yes, you want a tall pivot and a tall latch, and you want the metal that is supported at the pivot and latch to be tall.  But I think it's a lot less important between the two side pieces.  Although that might not be the case if you go to a center latch and aren't able to make such a beefy latch.  In that case you might need all of those twisting forces to go back to the pivot.

Gary Lewis wrote

....

That carrier on the early Bronco is interesting.  I like how he captured the jack in front of the carrier so that it would be secure if the carrier were somehow locked closed - although I don't think he has that ability.  

But I don't particularly like the way he seems to be securing the carrier.  First, it appears that he only has one way - the handled bolt on the left end.  That bothers me as I want both a belt and braces approach because if that carrier gets loose it is going to cause a lot of damage. Second, what I've read says you need a strong clamp in the vertical direction to prevent the whole assembly from moving as you go down the road - or off the road.  And while that bolt will keep it from going very far, I wonder if it will allow the two pieces of metal to move in relation to each other, which will remove the finish as well as cause noise when the rust starts there.

As I noted, that carrier has strong and weak points.  I haven't looked it over all that closely, but I don't think I'd choose to copy it exactly.

One usually mis-used term that this brings to mind is "over-engineered."  People use it to mean something that's built way stronger than it needs to be.  But that's not over-engineering.  It's over-building, frequently to try to make up for the lack of engineering that went into it to begin with.  And pivot and latch points are usually the weak links in under-engineered but over-built tire carriers.

Ok, side-stepping the "how big/thick/strong does the swing-arm material need to be" question for the moment so as to deal with the "how far across does the swing arm need to go" question, I measured my two trailers.  And, it is intuitively obvious to the casual observer that the full-width swing arm is NOT going to open with either of my trailers attached.  And probably not anyone else's trailer either.  

But, a half-width swing arm will clear essentially any trailer as the midpoint doesn't quite reach the ball if the ball is 8 1/2" back of the pin in the receiver, which is about where my draw bars would put it.  On top of that, the ball is going to be many inches below the swing arm, so there's chance of hitting.

So, the question I need to answer is whether I want to be able to open the tail gate, and by necessity the swing arm, when a trailer is connected.  And, I think the answer is "yes", assuming I can redesign the latches, rubbing blocks, etc to my satisfaction.

So, that's my next quest.  And then I'll worry about what material to use.  

I'll be back!!!!  (But, don't let this keep you from commenting, suggesting, or even critiquing.)

I'm back!  And, I think, and hope, that I have "the answer".  But, I'll need several "pics" to 'splain it to you.  And, the detail isn't all done, but why get the detail right if I'm going to throw it away - again?  

First, I have a spring-loaded pin-lock drawn in just ahead of the vertical tube that comes down from the tire carrier to the lower swing arm.  It will ride up on a ramp of that UHMW plastic and then drop in a hole in it to secure the arm temporarily, meaning while in camp but not while on the road.

And, I have a T-bolt that will go into a tapped hole in the bumper to secure the swing arm for on the road.  It will pull the arm down against the ramp mentioned above, and prevent it from swinging back.

And both of those are shown here - from the left-front with the bed off:

And here's a closer view of that.  Note that the T-handle has a spring to retract it so it doesn't hit the bumper when the arm comes home.

And, there's a 2" x 3" x 1/4" plate on the back of the swing arm to ensure it doesn't go too far forward.  However, this puts metal on metal, so I need to space the tab rearward 1/4" so I can put 1/4" of the UHMW plastic on the front of it and still have the swing arm stop flush with the bumper.

And, here's a view from above showing that you can reach both the pin-lock and the T-handle.  But, the pin-lock has been changed to a model with a ball for a handle instead of the longer handle as if the handle were left in the fore/aft position it would hit the tailgate when the arm was swung home.  And the arms of the T-handle are sized at 3 3/4" total as that will just clear the tire, the tailgate, and the vertical support arm as you tighten it.



And, now for the view that had me stumped for a while today.  I downloaded the file for Destaco's clamp as I thought I was going to use it.  But, I discovered that it is too tall, top-to-bottom, to put the handle on the bottom as it hung below the bumper.  And, when I pointed the handle up I realized that it had to be at least 16" left or right of the tire's centerline or a 35" tire would hit it.  So, if you put it on the left you have to extend the lower swing arm 18" past the center, and that defeats the purpose.  And, if you put it on the right it is now close to the center of the lower arm, and thereby loses its leverage.

Plus, while the better clamps are rated at 2000 lbs, I've also read that many people have had the "U" break on them.  And that wouldn't be good, at all, when on a trail or the highway.  So, I think the old-fashioned bolt idea sounds better.



I have a lot of details to work out, like the L-bracket for the T-handle, and how to keep the T-handle in that bracket, and the stop tab needs cushioning, and I need to design the ramp and make sure that will work, etc.  But, I wanted to get some feedback before I go to that trouble and then someone points out another major flaw.  So, please tell me what you think!

I see no major flaws.  Personally I think having to turn a screw out and then back in again would be more effort than I'd want to do to open the tailgate.  I don't see a great way around that with your goals and constraints.  And of course it's not me that needs to do it, so take it for what it's worth.

And a thought from someone else's design (maybe that early Bronco I linked before?), I read that someone wanted the spare tire as far to the left as possible.  He thought it would be less in the way of visibility if it was right behind the driver.  I'm not sure if I completely agree wit hthat, but it makes some sense to me at least.  To see behind you  the middle is probably most important.  And for lane changes you want to be able to see over the right end of the gate, but to the left you're going to look out the side window.  Anyway, just a thought.  If you chose to do that (and I'm not saying you should), you could mirror it to put the pivot on the driver's side, and move the tire as far over as you could without the tire hitting the bed when it swings open.  (Might give you room for the DeStaco clamp on the end again?)

Thank you for the review!

I've thought about it long and hard, and I don't think I want to move the tire from the center.  The main reason is that I have the jack mounted on top of the swing arm and with the current position of the tire in the center the jack, w/o the bit on the end, just stops at the top of the tailgate.  But, if the tire moves to the side it'll change the angle of the upper swing arm and the jack will stick way up in the air.

And, I do plan to put a rear-view camera on the truck.  I don't like the idea of having the spare tire behind the bumper and just waiting to be the first thing that hits - and then it will hit the tailgate.  On the other hand, it isn't nearly as far back as many I've seen on the road as people frequently use a spare tire carrier that goes into the receiver, and those put the tire typically another 6" to 12" further aft.  So my approach isn't as bad, but I still want the camera.

As for the screw, it is fiddly.  But, I don't think I'll be opening the tailgate all that much to make it a real pain.  And, the knowledge that it is very secure and won't be coming loose is worth it to me.

Having said that, I won't need to use the screw except when getting on the road as the pin-latch should provide good retention while parked.  But just not good enough to make me comfortable when driving.

Gary Lewis wrote

...one manufacturer of spindles for swing arms such as this was emphatic that you must cinch the swing arm down very firmly...

It's probably a consideration for that mfr.'s spindle.  But if you use a Ford spindle (like the ones on the front of your truck, or a similar 4WD truck), that consideration becomes irrelevant.  A spindle strong enough to hold the ENTIRE TRUCK up is certainly reliable enough to hold a swinging spare DOWN.

Gary Lewis wrote

...if the clamp is on the right end of the swing arm.  And if you place the clamp there the tire would have about 20:1 leverage advantage on it.

Again: irrelevant if you use a stock 4WD hub lock designed to take the torque from the engine (~200 lb-ft) multiplied through the trans (~6:1), t-case (~3:1), & diff. (~4:1); total ~15K lb-ft.  The weight of the whole arm & spare assembly should be (far) less than 200 lbs, so its COM would have to be 70' from the pivot (if it were pivoting horizontally, so subject to gravity) to equal the potential load on the hub lock when it's on a real truck.

Gary Lewis wrote

...thereby closing the triangle.

That's more of a design choice than an engineering consideration.  Having a triangular arm in this application does not improve strength or strength-to-weight.

Gary Lewis wrote

...a metal/metal contact which I'm trying to avoid.

Easy to design out later with a piece of UHMW self-adhesive tape, or a thicker panel screwed on.

But a significant weak point in your design is the catch...

With a round pin (regardless of the hole shape), the whole load essentially rests on a line along the axial surface of the pin, which presses against the stop (the hole in the top of the bumper).  That's high-wear, no matter what the material.  A vastly-stronger (lower-wear) design is a pawl: a moving prismic shape with a large(r) surface area in-contact with the stop.  Look at the latch on the doors in your house.  Just remember that it needs AT LEAST as much wearing surface on its attachment (swingarm) side as on the stop (bumper) side.  So imagine a vertical rectangular tube with a rectangular steel bar inside wrapped in plastic low-friction tape.  The bottom end of the bar is angled (ramped) so it rides up the top corner of the bumper, and then drops into a rectangular hole, giving a rectangular (vs. linear with the round pin) wear surface.  The farther it drops into the bumper, the more vertical slop (bounce) it tolerates, BUT the deeper (fore-aft) it has to be for its ramp surface to have a workable slope.  The wider it is, the less wear it will experience, exponentially (~1/4 the wear at double the width) for each material.

The handle for the latch (regardless of shape) does not need to be near the latch itself - it's cheap & easy to add a small operating rod (or flexible sheathed cable) from a conveniently-placed handle down to the latch pin, hidden behind the spare.  Common plastic replacement bearings for any vehicle door latch operating rods are cheap & available to reduce wear & noise.

Steve83 wrote

....  But if you use a Ford spindle (like the ones on the front of your truck, or a similar 4WD truck), that consideration becomes irrelevant....

Again: irrelevant if you use a stock 4WD hub lock designed to take the torque from the engine (~200 lb-ft) multiplied through the trans (~6:1), t-case (~3:1), & diff. (~4:1); total ~15K lb-ft....

Interesting!  However I'm thinking there's too much slop in a locking hub to hold the carrier tight enough for even my standards (and Gary sure seems to have a lot higher standards than me on things like this).  But as a latch it would be plenty strong.

As to the spindle strength, I wouldn't doubt it either.  But it does mean that the end of the bumper would need to be strong enough to take the entire load rather than being able to share it with the latch point.

On your later point about the line contact of the pin latch, I don't think that's a concern in Gary's design because the bolt is what will be holding it while driving.

Wow, guys!  Lots to think about.  Let me try to go point by point:

Spindle: I'm pretty sure that a Ford spindle will be much too tall.  I actually started trying to use a light-duty boat trailer spindle that I happen to have, and it was too tall.  And I'll bet that the Ford spindle will be even taller.  The issue is where the top of the spindle is with respect to the tail light.  The spindle I have in the plans is just tall enough to cover the reflector that is below the backup light, and the trailer spindle would have covered the backup light.  So I would expect that a Ford spindle would be into the tail light itself, and I don't want to do that.

Plus, the trailer and Ford hubs are cast and wouldn't be good to weld to.  I consulted my fabricator friend on that one, and he nixed a cast hub.  But we even looked at bolting to a cast hub and couldn't make it work.  Fortunately, there are at least two companies making spindles specifically for swing arms, and they have steel hubs and are short enough to clear the lights.

But, I will say that all of this saddens me as I really did want to use Ford parts where I could.  

Lock: I love the idea of using the hub lock!  That's absolutely cool!  But, I agree with Bob that the slop would be too much for this application.

Triangle: Yes, this is a choice.  And I want the triangle closed so there's no give.  Obviously there are two ways to design it w/o closing the triangle.  One is to omit the vertical piece, and to do that would then focus all of the tire's weight via the lever arm of the upper tube on its weld to the lower arm - not something I want to do as I'm pretty sure it would crack the weld in short order.  The other way, by eliminating the upper, angled, arm does away with the jack's mounting point.

Metal/Metal: Yes, I'll prevent that with a piece of UHMW between the two parts.  I just need to remember to space the stop back to keep the swing arm parallel with the bumper in the closed position when the UHMW is there.

Pin Latch: This is the red ball-handled latch that will be used when the truck is stationary.  And I agree that there are stronger designs.  But, as Bob pointed out, it is not intended for use while driving. In addition, it will be latched into a block of UHMW, and the latch I've selected is probably as strong as the block.

Clamp: As shown above, this is the T-handled bolt that will clamp the swing arm down to prevent bouncing as well as ensure it doesn't move rearward.  In the illustration above I had a major error as I didn't include the upper support for the T-bolt.  So, as drawn, rearward pressure on the swing arm will try to bend the bolt.  But with the upper support in, meaning that the t-bolt passes through two pieces of steel which are inches apart, rearward pressure is trying to shear the bolt, which isn't likely to happen given the 1/2" size thereof.

Having said that, I'm still struggling with that screw as the clamp.  And, if it is to be a screw, where should it be?  One idea is to make the screw a lot longer so the T is easier to reach.  Another is to use some form of a quick-turn fastener so there doesn't have to be a lot of twisting.  Or, leave a hex head on it and stash a ratcheting wrench nearby with a magnet.  (There are copious tools in the toolbox up front, but that wrench would be handy.)

Or, use some type of over-center latch to pull the arm down to the bumper.  But, I can only put something that is no more than 1/2" high on top of the bumper or the tailgate will hit it.  

Anyway, please keep those ideas, suggestions, and critiques coming in.  Paraphrasing "it takes a village", it takes a forum to design a bumper.  

https://shop.opticsplanet.com/freespirit-recreation-overlander-trailer.html?_iv_code=3H1-TND-TRFY-TROV200&utm_source=google&utm_medium=cpc&utm_campaign=plusbox-beta&gclid=Cj0KCQiAi57gBRDqARIsABhDSMorg3TwrOMr4ajQIf0WGm2qO-gArVNVUkz_fQBgQ7A3Ae0y2r5b0WgaAjn-EALw_wcB

Grumpin - You think I need to go with a trailer instead of a bumper w/a tire carrier?  Just leave the spare in the back?  

Oddly enough, the guy that's going to build the bumper makes off-roading/excursion trailers.

Here's another link to another early Bronco thread.  I haven't looked at it very closely,but it's specifically about custom tire carrier latches.  You might find it helpful.
http://classicbroncos.com/forums/showthread.php?t=288715

Gary Lewis wrote

The issue is where the top of the spindle is with respect to the tail light.

Not if the spindle is recessed down into the bumper, or if the spindle points down (eliminating the possibility of a hub-lock latch).

Gary Lewis wrote

...cast and wouldn't be good to weld to.

I'm pretty sure they're forged steel, and are fine for welding.  But you wouldn't actually need to use a real hub - just a (weldable) steel tube to fit the bearings into, with splines (which can be VERY sloppy & coarse) for the hub lock to grab.

Gary Lewis wrote

...the slop would be too much for this application.

Not if you position the arm against the stop, and then adjust the hub lock's angular position to eliminate the slop before welding its splined axle stub to the bumper.

Gary Lewis wrote

...the upper tube on its weld to the lower arm...

But there's no need for a lower arm - just an angled arm from the hub up to the spare mount, at the angle needed for the jack stowage.  No triangle; no bracing; no extra weight/cost/complexity - just an arm to support the spare's & jack's weights.

Gary Lewis wrote

...I'm pretty sure it would crack the weld in short order.

Only if ALL the welds are going to crack.  If you think you (or your welder) can lay down a good bead, then you can lay a good one there.

Gary Lewis wrote

...it is not intended for use while driving.

I'm still trying to (not-so-)subtly encourage you to use a SINGLE latch that does the whole job.

Gary Lewis wrote

...into a block of UHMW...

That wouldn't WEAR away, but it would DEFORM far more-rapidly than steel-on-steel.  Plastic is too soft for such a concentrated load - it still needs to be spread out over a large flat surface.

Gary Lewis wrote

Grumpin - You think I need to go with a trailer instead of a bumper w/a tire carrier?  Just leave the spare in the back?  

Oddly enough, the guy that's going to build the bumper makes off-roading/excursion trailers.

I'm impressed with what you're doing and the planning. That's more tongue in cheek of what I would do, if I could afford it, because I'm not patient enough! Trying to be funny!

And I went back and read the first post to see why you're not using the bed. Makes sense, room for gear.

Bob: Thanks for the link.  Those guys were going through many of the thought processes I/we've been going through - and coming to many of the same conclusions.

And, they were using/thinking of the same clamps I've been looking at, three of which are shown below.  The top one below is from Smittybilt.  I know 'cause I held one in my hands yesterday at 4WD Parts when I took Janey in so she could shop for a few gifts for me.  It is part #76856-05.  But, it doesn't really appear as something the sell on their website, so I'll have to call them - if I can figure out how to use it.

But, I haven't figured out how to use any of those.  The limitations are significant, and include that I don't dare put anything more than 1/2" high on top of the bumper or the tailgate may hit it, and the big spare tire prevents placing something in the center.  But, it would be easy if the lower arm went all the way across.  



Steve: I haven't gotten a mind's eye view of how the spindle could be used upside down, nor easily recessed into the bumper.  But that's sorta moot as even if the hubs aren't cast, and you may be correct, they'd take a hole bunch of machining to get down to the diameter that would fit - if that is even possible given the size of the bearings.  And to make a hub is more machining than I want to do - especially since I'm hoping to make this something that can be built commercially and/or by others.

So I'm not going to use a Ford spindle.  Instead I'll be using one of the commercially-available spindles meant for this purpose as they'll fit w/o obscuring the tail light and don't require a lot of modification.  None, in fact.

As for the swing arm, I'm going to use a closed triangle.  I want a stop/rest on the far side of the swing arm that takes the load off of the spindle and ensures there are no rattles, and that is much easier to do if the arm has a component that is a fraction of an inch above the bumper.

And, I'm going to have two latches - one that is easily used while "in camp", and one for traveling that is very positive that ensures the whole contraption cannot move in any direction.  Just what that positive latch will be is what I'm struggling with, and that's where I'd like to have help.

Grumin: A trailer would be easier in many ways, but it will also be more expensive, cut down on the already-dismal MPG, and would have to be dropped before heading out on many of the trails.  But, it is something that I did consider before embarking on this quest.