Quarter elliptic bobber suspension

[KsM715]

The only reason the rear suspensions works as well as it does is because of the pivot point that you would be disabling. By locking the rear of the leaf spring to the frame. you would end up relying on the leaf spring only, for suspension travel. The springs themselves, don't have that much travel in them.

Exactly. The springs on a stock tandem are very stiff and meant to absorb small bumps on the road. The articulation for off road manuvering comes from the axles pivoting on those center bearings. You lock those down, you lose all the articulation. That would be one very rough riding bobber.

 

[plym49]

The only reason the rear suspensions works as well as it does is because of the pivot point that you would be disabling. By locking the rear of the leaf spring to the frame. you would end up relying on the leaf spring only, for suspension travel. The springs themselves, don't have that much travel in them.

I'm not sure that is correct. The rear spring is a slipper spring. The axle location and articulation is handled by the torque rods. They would be intact under this proposal, so in fact the rear might articulate better than using semi-elliptic springs and no torque rods, as on most bobbers. IOW side to side articulation would be the same. Front to rear articulation would be less, but probably no less than on a regular bobber.

 

[Highdiver]

You're understanding of the deuce suspension must be beyond mine. Good luck with that.

 

[Trango]

I'm not sure that is correct. The rear spring is a slipper spring. The axle location and articulation is handled by the torque rods. They would be intact under this proposal, so in fact the rear might articulate better than using semi-elliptic springs and no torque rods, as on most bobbers. IOW side to side articulation would be the same. Front to rear articulation would be less, but probably no less than on a regular bobber.

Not quite. Since the entire leaf spring assembly is itself joined to the frame via a massive pivot (which is essentially a spindle, bearing, and hub arrangement), a large measure of articulation occurs with each individual spring assembly completely flat. Allow me to explore that word, "flat". By this I mean that the leaf spring could be completely diagonal, using the frame or bed rails as a reference point; but that it's completely "flat" (or perhaps better said to be "in plane") with reference to the mounts it's u bolted onto.

Take away the seesaw action provided by the pivot and the other axle on the other side of the seesaw, and you will find that the leaf behaves very differently.

Now, the heart of your question is just *how* differently it behaves, once you lock the pivot and then place the entire load on one side of the leaf. Yes, via the spring law, you will see increased deflection when you load that one side of the leaf. Will it more than compensate for the loss of articulation experienced when the pivot is allowed to freely seesaw? Based on my experience, that's unlikely. That said, will the increased deflection be nonetheless sufficient to allow enough articulation to prevent loss of traction through wheelspin? Perhaps.

Untimately, this would be a cheap and almost free mod to perform. You would need to lock out the front of the leaf (or weld the pivot, which would be potentially dangerous and really not recommended), and then build a new driveshaft to the rear (assuming you ditch the front tandem). Otherwise, the rest of the mod is simple excision. A caution, however - make sure the lock you create for the one side of your leaf is beyond bombproof, because if that lets go, well, it would be far from ideal.

Best,
Bob

 

[plym49]

Not quite. Since the entire leaf spring assembly is itself joined to the frame via a massive pivot (which is essentially a spindle, bearing, and hub arrangement), a large measure of articulation occurs with each individual spring assembly completely flat. Allow me to explore that word, "flat". By this I mean that the leaf spring could be completely diagonal, using the frame or bed rails as a reference point; but that it's completely "flat" (or perhaps better said to be "in plane") with reference to the mounts it's u bolted onto.

Take away the seesaw action provided by the pivot and the other axle on the other side of the seesaw, and you will find that the leaf behaves very differently.

Now, the heart of your question is just *how* differently it behaves, once you lock the pivot and then place the entire load on one side of the leaf. Yes, via the spring law, you will see increased deflection when you load that one side of the leaf. Will it more than compensate for the loss of articulation experienced when the pivot is allowed to freely seesaw? Based on my experience, that's unlikely. That said, will the increased deflection be nonetheless sufficient to allow enough articulation to prevent loss of traction through wheelspin? Perhaps.

Untimately, this would be a cheap and almost free mod to perform. You would need to lock out the front of the leaf (or weld the pivot, which would be potentially dangerous and really not recommended), and then build a new driveshaft to the rear (assuming you ditch the front tandem). Otherwise, the rest of the mod is simple excision. A caution, however - make sure the lock you create for the one side of your leaf is beyond bombproof, because if that lets go, well, it would be far from ideal.

Best,
Bob

Thanks for the helping think this through.

I can see a couple of possibilities.

If you are eliminating the front tandem, then you don't need to cut the spring. Just solid-mount the front slipper end to the frame visa a suitably strong bracket. The pivot will for all intents and purposes be locked (no need to weld not would I ever consider such a thing. This would provide a fairly easily reversible way of eliminating the front rear tandem axle.

If you were eliminating the rear tandem, then this option is probably not possible (depending upon how mush you were shortening the frame). If you had to cut the main spring it could be cut vertically behind the topmost short leaf. Remove the u bolts, build a saddle (for it to mount on) and stirrup (to add rigidity) that wraps around the center section of the spring pack and attaches to the vertical face of the frame. Replace the ubolts - the pivot might sit at a slightly different angle (not completely flat to the ground) but that would not matter. Still reversible except for the spring.

Since the remaining rear spring is slipper-mounted to the remaining axle, I suspect it would articulate as easily if not better than a semi-elliptic setup (with Deuce front or trailer springs).

I agree that the key is how well that center section of spring is controlled once one rear axle goes bye-bye. It would seem the two options are keeping the spring intact and locking the distal end to the frame, or cutting the spring and fabricating a bulletproof - I like your term bombproof - saddle/stirrup to positively locate the fat end of the spring no matter what.

 

[KsM715]

I'm not trying to change your mind or disagree with you here, just giving suggestions.........

If you're going to cut the frame of the truck then why worry about making a modification to the suspension that is easily reversible back to stock. You can knock out the rivets and remove the whole tandem set-up and set it aside. It can be easily re-riveted back in place. Right now I can unbolt the whole M105 suspension from under my bobbed deuce and put the tandems back in the original location.

The whole worrying about killing another truck or trailer is pointless, thats going to happen anyways, infact theres one totally wrecked truck in the forums right now thats getting parted out. Theres no way that truck will get restored back to factory specs with out someone else parting out some other truck. M105s are cheap and plentifull

 

[plym49]

I'm not trying to change your mind or disagree with you here, just giving suggestions.........

If you're going to cut the frame of the truck then why worry about making a modification to the suspension that is easily reversible back to stock. You can knock out the rivets and remove the whole tandem set-up and set it aside. It can be easily re-riveted back in place. Right now I can unbolt the whole M105 suspension from under my bobbed deuce and put the tandems back in the original location.

The whole worrying about killing another truck or trailer is pointless, thats going to happen anyways, infact theres one totally wrecked truck in the forums right now thats getting parted out. Theres no way that truck will get restored back to factory specs with out someone else parting out some other truck. M105s are cheap and plentifull

I appreciate that.

But I like to look at alternatives. It gives you a better insight and also sometimes you hit on something good.

So far there seem to be three ways to bob a Deuce: trailer suspension with either axle blocks or a subframe under the main frame rails, Deuce front suspension or an air-bag setup from an 18 wheeler. If this is feasible, then here is a fourth way.

Even if you have no qualms about cutting up a Deuce or a trailer, each of the existing three alternatives requires the Deuce owner to obtain something else.

Modifying the tandem into a single would then, if it can work, also provide an alternative where no 'other' parts are needed.

 

[shovelheadmike]

That truck is now owned by a SS member.

Yes, it.was. However, the last I.saw, he was trying to sell it.

 

[SamM]

I'm no expert but I do have a little experience with a 4-link quarter-elliptic rear suspension. After a call to Jeff Beach at Beach's Off-road in California and him telling me that I could not build a quarter-ellptic suspension myself, I set off to do just that. He wanted me to send my FJ-40 and $5000 to him in CA for the conversion. Not happening! I then, contacted Avalanche Engineering in CO and bought an FJ-40 quarter-elliptic rear suspenion kit that they happened to make. In a nutshell, the kit was very well made but it turned out to be poorly designed. I was able to use everything but it had to be re-engineered to fit under my truck. The Avalanche kit had the springs oddly placed outboard of the frame and all the links inside the frame. I had never seen this before. The odd placement of the springs limited movement and limited the space for tires. My plan was to run 35 or 37" tires on 8" rims. I moved the springs under the frame and the lower links outboard. The upper links were left in the original Avalanche kit location as they worked well there. The kit included: chromoly links, link mounts, heim joints, jam nuts, springs, spring hangers, shackles, limiting straps, bumpstops and all the hardware. The springs ride normally on the bumpstops but drop away during off-road articulation. My Land Cruiser as pictured here had over 40" of rear articulation with the pictured 33" tires. I'd love to see a quarter-ellptic on a deuce. The truck also featured: an Aqualu aluminum body, aluminum fenders, 350 V-8 engine conversion, 4 wheel disc brakes, a full rollcage, Cobra gunship harnesses, a custom frame with airtank, Bestop Jeep seats and much, much more.

Not much of the stock deuce suspension could be used. You'll need to size your parts to fit a deuce axle. Read: BIG! The good news is that these parts are available. Do a search of 4X4 suspension components and you'll find everything you'll need. It will be pricey. Sorry the pictures aren't bigger. These were all I salvaged after my computer went down.

On a sidenote: the State said that my truck was no longer safe and I had to cut the 4-link kit from my truck. In disgust, I cut everything from the truck, welded in new mounts for stock type springs and sold it off a few years ago. I now drive a Jeep TJ with all the axle movement I could want.

SamM

 

[SamM]

Just to sum up. The pictures show about half of the movement possible with a quarter elliptic rear suspension. The limiting straps located above the axle are only at half their length. It's hard to see in the crappy pictures. You may also be able to see that the driver's side spring has dropped away from the bumpstop located just above it. The passenger side rear wheel and tire are stuffed into the wheelwell but do not touch anything as I cut the wheelwell to fit the bigger tires.

The Avalanche kit also included the axle truss for my stock FJ-40 rear axle. My ultimate plan was to make a custom centered diff hybrid axle for this truck. I purchased a Front Range Off-road full floating axle kit for a Toyota Minitruck. The outer minitruck axle ends would be cut from a mintruck axle, centered and welded to a cutdown FJ-40 axle center section. Since both axles assemblies use 30 splined shafts, it would work perfectly. Minitruck stiffeners and a custom truss for the links would make it pretty stout. Much larger FourRunner 40mm calipers would work at both ends of the FJ. I planned to use an NV4500 tranny and an Atlas case to finish the truck up.

This truck had lockers front and rear as well!

SamM

 

[trukhead]

Some 1/2 strap iron or some log chain looped up over the frame and a bolt through the chain or strap and under the spring end to hold up the end of the spring where the axle you removed used to be, badda-bing: badda-boom you golden homes

 

[booger]

Some 1/2 strap iron or some log chain looped up over the frame and a bolt through the chain or strap and under the spring end to hold up the end of the spring where the axle you removed used to be, badda-bing: badda-boom you golden homes

sounds like a wreck waiting to happen

 

[Awesome Possum]

Some 1/2 strap iron or some log chain looped up over the frame and a bolt through the chain or strap and under the spring end to hold up the end of the spring where the axle you removed used to be, badda-bing: badda-boom you golden homes

Exactly what I was thinking. Mind you, I wasn't thinking it was a GOOD idea, but an idea nonetheless. I have seen a couple of bobs that used some sort of larger trailer suspension for the rear axle, but even these looked to be overkill, and a bit iffy to boot. I'd've cut up the 105 if I hadn't managed to get a set of front springs locally.