dieselcruiserhead
16 Years on ExPo. Whoa!!
That's very generous of you... Sure, why not... Those bushings are actually Energy Suspension, if it helps... 
Trailer Building Indepent Arm Building - Official Guide
- Thread starter dieselcruiserhead
- Start date
ntsqd
Heretic Car Camper
I'll second MotoDave's concern about Heim (Rose/"SRE"/etc.) joints. By the time you buy a quality level that will last you've invested heavily, and their life span is directly affected by the airborne dirt encountered. If SRE's are the chosen pivots I would highly suggest that some Seals-it washers be part of the build from the very beginning. Even then their life span isn't going to be exceptional. Might be acceptable, but not exceptional.
Might be helpful to start with identifying what is needed/desired out of the pivot assembly, and go looking from there. Could well be that an industrial or other non-automotive solution would work better.
It would seem to me that the primary two functions are a pivot point and some vibration isolation. Ideally any misalignment would be a function of damage and not fabrication.
Might be helpful to start with identifying what is needed/desired out of the pivot assembly, and go looking from there. Could well be that an industrial or other non-automotive solution would work better.
It would seem to me that the primary two functions are a pivot point and some vibration isolation. Ideally any misalignment would be a function of damage and not fabrication.
ntsqd
Heretic Car Camper
The impact loads would seem to rule out a Nylatron sleeve bushing unless someone has experienced that they do work in this application.
Hum, speaking of Seals-it, this looks promising:
http://www.sealsit.com/gbody.asp If required, a field replacement could simply be a stock G-body rubber suspension bushing.
Hum, speaking of Seals-it, this looks promising:
http://www.sealsit.com/gbody.asp If required, a field replacement could simply be a stock G-body rubber suspension bushing.
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R_Lefebvre
Expedition Leader
I'm not sure how Nylatron compares to Delrin, but I've had the Delrin in for a number of years, and no issues. It's common in race cars and I've never heard of failures.
Andre, you touched on one of the things I felt since day one, is that trailers don't need to have "flex", and the idea of an "independent" suspension isn't that important. The simple fact is, a trailer is a tripod. It will straddle the terrain no matter what is under it. The only thing you really need is enough bump travel to absorb any bumps you will be encountering *at speed*.
I also wouldn't suggest using spherical bearings. Those things are a nightmare, and only suitable for pure race cars. Though I guess I shouldn't say that because I built myself some camber plates using them. Haven't had a problem yet, but it doesn't have that many miles. Anyway, I think they're a poor choice for this application.
As far as flexibility is concerned, I don't think any will truly benefit a trailer. Keep the axles rigidly in line.
Andre, you touched on one of the things I felt since day one, is that trailers don't need to have "flex", and the idea of an "independent" suspension isn't that important. The simple fact is, a trailer is a tripod. It will straddle the terrain no matter what is under it. The only thing you really need is enough bump travel to absorb any bumps you will be encountering *at speed*.
I also wouldn't suggest using spherical bearings. Those things are a nightmare, and only suitable for pure race cars. Though I guess I shouldn't say that because I built myself some camber plates using them. Haven't had a problem yet, but it doesn't have that many miles. Anyway, I think they're a poor choice for this application.
As far as flexibility is concerned, I don't think any will truly benefit a trailer. Keep the axles rigidly in line.
MotoDave
Explorer
Forgive my ignorance, but why is it bad to have some compliance in the pivots of your swingarms?
If you wanted it to be super stiff and no compliance, you can use some sort of bearings (roller?), but you'd better have really great tolerances in your build, as any misalignment will make installing the pivot bolts impossible.
I guess vibration isolation isn't as important on a trailer, but it still seems like you'd want some give in the system to keep everything from being shaken to pieces.
If you wanted it to be super stiff and no compliance, you can use some sort of bearings (roller?), but you'd better have really great tolerances in your build, as any misalignment will make installing the pivot bolts impossible.
I guess vibration isolation isn't as important on a trailer, but it still seems like you'd want some give in the system to keep everything from being shaken to pieces.
DGarman
What could go wrong?
Howdy All-
When I worked in off-road racing in the mid-90s, we started changing from Delrin for suspension bushings over to UHMW. IIRC, it stands for Ultra High Molecular Weight (Polyethylene?). It seemed to be more resilient than Delrin, and would last longer.
However.....
Dieselcruiserhead-
I think your bushing problem and deformed crossmember problem are being caused by misalignment of the a-arm pivots. I just can't see a Jeep leaf spring bushing dying in an a-arm trailer application if the pivots are in line.
A good way to check pivot alignment is to pull out the pivot bolts and run a similar-sized length of all-thread from one side of the trailer to the other.
Good Luck
When I worked in off-road racing in the mid-90s, we started changing from Delrin for suspension bushings over to UHMW. IIRC, it stands for Ultra High Molecular Weight (Polyethylene?). It seemed to be more resilient than Delrin, and would last longer.
However.....
Dieselcruiserhead-
I think your bushing problem and deformed crossmember problem are being caused by misalignment of the a-arm pivots. I just can't see a Jeep leaf spring bushing dying in an a-arm trailer application if the pivots are in line.
A good way to check pivot alignment is to pull out the pivot bolts and run a similar-sized length of all-thread from one side of the trailer to the other.
Good Luck
dieselcruiserhead
16 Years on ExPo. Whoa!!
What happens is the arms are vertical, tow great, and are perfect out of the box with the trailer empty. Under load however the bushings deflect heavily (and/or possibly the arms themselves are flexing) with a top-side-in type camber to the wheels. It is messing with both alignment and tire wear heavily and really there is a lot of flex to it all. Some of you guys know I'm sort of waivering/wishy washy about selling my trailer mostly because it will be used maybe once a year on a good year... As mentioned in the ad I was planning to take extensive steps to bring it back to line before I sold it. I was probably going to remove the bushings all together and have a piece of steel thick wall DOM and a long bar as the pivot point to eliminate all flex at least as the front of the arms. I was then going to beef up the arms some more from gusseting.
I have to say despite the deflection the trailer still tows really well. I was able to even fishtail on fast dirt roads at 35-45 mph (as fast as I could drive my truck without the trailer regardless) and it did just great... It literally follows you anywhere and effortlessly and over anything and all terrain. I built my pickup with long travel soft suspension something more 'baja' oriented rather than 'off road' and the trailer suspension as in line with all of this, I found...
I have to say despite the deflection the trailer still tows really well. I was able to even fishtail on fast dirt roads at 35-45 mph (as fast as I could drive my truck without the trailer regardless) and it did just great... It literally follows you anywhere and effortlessly and over anything and all terrain. I built my pickup with long travel soft suspension something more 'baja' oriented rather than 'off road' and the trailer suspension as in line with all of this, I found...
MotoDave
Explorer
OK, that makes sense, got it.
The way the swing arm is loaded is putting a twisting force on the bushings, which is why you're seeing camber changes due to bushing deflection. Ideally you'd have the forces balanced so that both bushings see the same force, deflect equally, and you don't have camber change under load. I'm not sure if that's possible with the packaging constraints you have, but I'll draw up a few ideas in CAD tomorrow and throw them up for discussion
The way the swing arm is loaded is putting a twisting force on the bushings, which is why you're seeing camber changes due to bushing deflection. Ideally you'd have the forces balanced so that both bushings see the same force, deflect equally, and you don't have camber change under load. I'm not sure if that's possible with the packaging constraints you have, but I'll draw up a few ideas in CAD tomorrow and throw them up for discussion
UK4X4
Expedition Leader
My trailer build also uses poly bushings and I've seen no deformation to date
if the complience of poly bushings on a car is OK, why should it not be OK on a lighter trailer ?
I did mine a little diferent in that I used a straight axle to align the two sides
then cut out the middle, but with most garage built things, mounts on one sideended up slotted to get the wheels alighn'd
The issue with mine was the mounting nuts I welded into the frame.
On the whole I'm very happy with mine, on the trail, extremely compliant and active.
On the road it toes up to 85 mph with no issues ...............but the trailer bump steers all the time and never sits quite still.
I think this comes from my use of gas shocks with the air bags, rather than an oil damper
even heavily loaded the trailer is easy to move on the suspension.
Here's the thread
http://expeditionportal.com/forum/showthread.php?t=12092
My frame was home built with a 2" box for cross bars and a 2X1" C section as well.
the outer sides are mounted onto the frame rails with nuts welded in
The mounts were quite large !
if the complience of poly bushings on a car is OK, why should it not be OK on a lighter trailer ?
I did mine a little diferent in that I used a straight axle to align the two sides
then cut out the middle, but with most garage built things, mounts on one sideended up slotted to get the wheels alighn'd
The issue with mine was the mounting nuts I welded into the frame.
On the whole I'm very happy with mine, on the trail, extremely compliant and active.
On the road it toes up to 85 mph with no issues ...............but the trailer bump steers all the time and never sits quite still.
I think this comes from my use of gas shocks with the air bags, rather than an oil damper
even heavily loaded the trailer is easy to move on the suspension.
Here's the thread
http://expeditionportal.com/forum/showthread.php?t=12092
My frame was home built with a 2" box for cross bars and a 2X1" C section as well.
the outer sides are mounted onto the frame rails with nuts welded in
The mounts were quite large !
I don't see how your shocks are doing much UK. The mounting angle has them doing just a fraction of the "work" they're supposed to do (assuming maximum "work" is available with the shock perpendicular to the axis of rotation). This might be a contributing factor to the twitchy tenancies you describe. With the angle splayed back as far as your picture indicates, the shock is moving in and out at just a small percentage of the movement up and down. We could discribe this with some TRIG a bit better, but it is far too early in the morning for me to remember what SAH-COH-TAH stands for....
Spence
Spence
R_Lefebvre
Expedition Leader
It is early, it's actually SOH-CAH-TOA
You are correct that having the shocks layed down like that decreases their actual damping rate at the wheel, but that is easily compensated by using extra stiff shocks. And then the net result works out. Very common to lay down the shocks on racecar applications for aerodynamics or CG, and compensate with a high damping rate.
Key-Lock, I don't think we *want* to remove compliance for the sake of removing compliance. The issue here is the geometry of that suspension is not ballanced and there's a large twisting force on the arm, and the compliant bushings allow the wheel to achieve negative camber.
Car applications have compliant bushings, but they are designed with adjustable alignment elsewhere, so that one can compensate for any movement of the arm via bushing deflection. So, you align it to be relatively "straight" with a steady weight and no forces, as the vehicle would have travelling straight down the road. However, when the vehicle is being "handled" or on a rough road, there are HUGE movements in the wheels. Not just vertically, but for-aft, camber loss, etc. Most people just don't see it, because they don't drive like that, and if they do, they are inside the car. Go to an autocross sometime and watch the stock cars in the corners.
You are correct that having the shocks layed down like that decreases their actual damping rate at the wheel, but that is easily compensated by using extra stiff shocks. And then the net result works out. Very common to lay down the shocks on racecar applications for aerodynamics or CG, and compensate with a high damping rate.
Key-Lock, I don't think we *want* to remove compliance for the sake of removing compliance. The issue here is the geometry of that suspension is not ballanced and there's a large twisting force on the arm, and the compliant bushings allow the wheel to achieve negative camber.
Car applications have compliant bushings, but they are designed with adjustable alignment elsewhere, so that one can compensate for any movement of the arm via bushing deflection. So, you align it to be relatively "straight" with a steady weight and no forces, as the vehicle would have travelling straight down the road. However, when the vehicle is being "handled" or on a rough road, there are HUGE movements in the wheels. Not just vertically, but for-aft, camber loss, etc. Most people just don't see it, because they don't drive like that, and if they do, they are inside the car. Go to an autocross sometime and watch the stock cars in the corners.
60LCConvert
Observer
hmm lots of thoughts about the bushings going on, not sure if you can see them in any of my photos but I am using poly bushings that match my FJ60. In my post I stated that in the begining this trailer was going to be jjust for me, so I chose bushings that I new had good life and would also be common for me to find as replacements. If you are getting enough twist out of your arms to affect tire wear I think the bushings might not be your only culprit. Think of your vehicles when the bushing are sloppy and the springs are week how mush does that effect your tires, one reason I used a solid axle was I was not sure the torsional loads that a split type axle could take before causing that type of deflection. Test the theory, take of an arm and mount it to a table solid, weld your upper links down so no bushing to worry about, put a cheater on your spindle half the lenght of your trailers width and load it up with about as much weight you put in your trailer. I would be willing to bet that you willl see at least some torsional deflection in your arms. If you are realy wide at the top link and narrow at the bottom link it would theorectically make it worse. You know looking at your pics with enough load you might even be flexing your trailers body. Just my thoughts the arms look good, just dont think bushings are your only culprit.
ntsqd
Heretic Car Camper
Rigidity of the trailing arm is important. It needs to be rigid in torsion about it's length, bending, and resist the type of torsion that results in toe-out (better said as parallelograming?).
A thought that occurred to me in looking at some of the posted pictures is that the pivot tubes of each arm need not be pairs. It could be one long tube if the bushings have low enough compliance.
A concept:
A thought that occurred to me in looking at some of the posted pictures is that the pivot tubes of each arm need not be pairs. It could be one long tube if the bushings have low enough compliance.
A concept:
R_Lefebvre
Expedition Leader
You are correct, but for the practicalities of actually pushing a bushing that long into the pivot tube.
dieselcruiserhead
16 Years on ExPo. Whoa!!
I'm not sure you would need a bushing. My thoughts were metal to metal. ntsqd, that CAD image is along the lines of exactly the type of repair/mod I was going to make to the independent arm.
Also if it helps my bag is placed squarely center between the two mounting points. It appears as they are on the far side but they are between the bushings on a lateral scale. However this still provides resistance on the far side of the arm allowing for some flex in the material. Everything in the arm is 3/16" in so pretty thick...
Also if it helps my bag is placed squarely center between the two mounting points. It appears as they are on the far side but they are between the bushings on a lateral scale. However this still provides resistance on the far side of the arm allowing for some flex in the material. Everything in the arm is 3/16" in so pretty thick...