Suspension mod on pull-behind trailer - CONCLUSION

[MarkT]

Got the HF pull-behind cargo trailer a couple years back.  




Suspension WAY too stiff.  Destroys stuff I put in it.  Ride-On won't balance but instead unbalances the tires and makes the vibration worse. Reference this previous discussion on how Ride-On and other dynamic balancing media works: http://www.valkyrieforum.com/bbs/index.php/topic,99324.msg988651.html#msg988651

 The vibration coming through the hitch can't be good for the bike either.  So I was looking to soften the suspension.  Took out the helper leaf.  Practically the same.  Replaced the springs with the softest ones I could find online.  Still way to stiff.  So now I've radically changed it.  Cut off the back half of the leaf springs, designating  the front half as trailing arms, and replaced the support function with Valkyrie OEM shocks.  Before I did that, I made a jig to measure the shocks.  Found something I didn't expect.  

The shocks travel a hair over two inches.  Setting the preload at any of the 5 settings results in the top weight being 265#.  (Measured on a bath scale). The difference is, higher preload settings increases the spring pressure for a given deflection from zero up.  IOW, higher settings mean stronger springs at the beginning of deflection but no change at the top of the travel.  Contrary to my understanding.  Now my scale has some stiction so it's not scientific - but that is overcome by tapping it with a screwdriver.

Does this jive with your suspension understanding?  I'm not explaining it here - this is from empirical measurement.  I didn't graph it.  Maybe I should.

I want to have some adjustability with this, and it doesn't appear the preload is going to help with that.  The trailer is rated at 600# gross.  I think that's way more than I will usually need.  And I want the wheels to have sufficient movement to balance with Ride-on.  So I'm thinking a suspension range of say 200-450 is about right.

These shocks with a max capacity of 265# ea is too much.  So I determined I can lower their capacity and increase the suspension travel by angling them.  I set up two lower mount positions to change the angle.  The lower mount puts the shocks at 50°. So in theory, sin(50°) is .766 should yield 203# per wheel or 406# total.  Still feels very stiff, but in reality the fwd half of the spring is still providing some support.  The upper mount puts the shocks at 26°.  Sin(26°) is .438 should yield 116# per wheel or 232# total.  In both of these cases the angle changes - becomes less as the axle is deflected up so the actual spring support changes as a graph curve - if one needs to know those numbers, probably be easiest to just load it up, measure and graph it unless you are a math professor.  I think I'll just use it - give it a "smoke test" and if it works OK call it a day.

Here's a couple shots of the mod.  Here, it's in the upper, 26° 116# position. Now, the suspension has plenty of cushy travel.  And I can stiffen it for a road trip if I'm gonna load it up, with a wrench, in 10 minutes.  I haven't installed the panhard bar yet.  It really has no lateral movement now.  But I probably will, anyway.  Already have the parts.  No paint on the raw steel yet.

[John Schmidt]

Mark, seems like a fair amount of guess work involved. If it were me, after looking at all you did with it, I'd just pick up a set of torsion bar suspension, mount that and be done with it. You can get it either in a single axle that goes all the way across and moves independently on each side, or two individual trailing arm torsion bars that move independently. Seems like it would be less work in the end and give a better ride, especially when you hit a bump on one side it doesn't transmit across. Just something to ponder on. 

[MarkT]

Thx John. Actually I dont have any experience with installing torsion bar suspensions, or sourcing them either. This was almost free for me and it appears to be working.  This is a trailer - for hauling stuff not people - so I'm thinking independent suspension for better ride quality is overkill.  Prototyping for me - w/o having done this before - does involve some guesswork (guessing what weight loads I want to haul) but it involved some math and prediction as well as results coming out about as expected. Cost was just my time, mostly parts I already have (I did pick up some Heim joints for the panhard bar) and some welding materials . Pretty sure Im better off than I was as this trailer now has adjustable softer suspension that I now expect not to damage what I put in it. I like tinkering and I learn things.

I plan to use this on the ride to Roanoke.  And other long rides this year.

Here's a shot showing the 2 positions for the lower shock mount.  It's now in the softer position; the lower doubles the spring force.

[John Schmidt]

Unique set up, should work fine. My "Murphy's Law" experience would prompt me to add a U-bolt (similar to what is on the adjacent spring) diagonally across the frame member and passing under your welded attachment for the shock mount. Extra support/security for the welds since all the forces on them are downward. The welds look good, but a few thousand miles of jolts and vibrations can make a difference. But that's just me over-engineering again. 

[Gryphon Rider]

Weld gussets between your lower shock mounts and the axles.  A little bit of steel in that high-stress connection will make it way stronger.

For the upper shock mount, is your bolt clamping onto a steel bushing within the shock eye, or is your bold clamping the shock eye hard against the 1/4" flat bar?  If the latter, you are looking for trouble as this joint needs to flex; over time something will fatigue, perhaps the connection between the shock eye and the shock body.

[MarkT]

Weld gussets between your lower shock mounts and the axles.  A little bit of steel in that high-stress connection will make it way stronger.

For the upper shock mount, is your bolt clamping onto a steel bushing within the shock eye, or is your bold clamping the shock eye hard against the 1/4" flat bar?  If the latter, you are looking for trouble as this joint needs to flex; over time something will fatigue, perhaps the connection between the shock eye and the shock body.

I made the welds there extra thick to act as a gusset.  Actually the thickness of the axle is questionable - it's channel steel at 1/8" thickness - the weld is much thicker.  Also force on the shock mount-axle weld doesn't get the shock it would if it was immovable like the upper mount which is much more robust.  I'll inspect it periodically looking for cracks etc.  Pretty sure the axle steel will tear before the welds will.  Maybe with that in mind more steel clad on the axle would be a good idea.  All 4 shock eyes are with thick steel bushings provided by Progressive shock kits, inserted into the big OEM rubber bushing from Showa, and with an added washer and blue loctite (after I disassemble, paint and reassemble).  Bottom bolts have locknuts.

[Gryphon Rider]

Weld gussets between your lower shock mounts and the axles.  A little bit of steel in that high-stress connection will make it way stronger.

For the upper shock mount, is your bolt clamping onto a steel bushing within the shock eye, or is your bold clamping the shock eye hard against the 1/4" flat bar?  If the latter, you are looking for trouble as this joint needs to flex; over time something will fatigue, perhaps the connection between the shock eye and the shock body.

I made the welds there extra thick to act as a gusset.  Actually the thickness of the axle is questionable - it's channel steel at 1/8" thickness - the weld is much thicker.  Also force on the shock mount-axle weld doesn't get the shock it would if it was immovable like the upper mount which is much more robust.  I'll inspect it periodically looking for cracks etc.  Pretty sure the axle steel will tear before the welds will.  Maybe with that in mind more steel clad on the axle would be a good idea.  All 4 shock eyes are with thick steel bushings provided by Progressive shock kits, inserted into the big OEM rubber bushing from Showa, and with an added washer and blue loctite (after I disassemble, paint and reassemble).  Bottom bolts have locknuts.

I still advise gusseting that lower mount to the axle.  Look below how far around the axle shock mounts typically go; it looks like a 90° arc to me.

I didn't realise the axle was a channel shape.   Your shocks will really want to twist the axle, such that I would recommend boxing it between the shock an where the axle spindle is welded to the axle.  If you box it in all the way across, you won't need an anti-sway bar.

[MarkT]

OK I'll compromise and add some reinforcing angle iron along the corner of the axle between the shock mounts and extend the weld to reach to the mounts.  In both cases that will add steel to the tension side of the stress of the mounts to resist tearing.  Hope I have some 3/16 X 1.25" angle steel - might not & it's not a hardware store item; have to get it from one of my steel suppliers.  Also not keen on adding unsprung weight.

[MarkT]

Finished.  I added angle steel to the axle at the shock mounts and built up weld to act as a gusset.  I have plenty of confidence in this mod.  Didn't add a sway bar as the trailer is lightweight and the pivot points at fwd end of the leaf spring and again at all shock mounts are quite robust. And they can be tightened to take up lateral play which I did.  And used locknuts so they won't loosen.  I can't make the axle move laterally at all with large levers.

Haven't hooked this up to the bike and checked to see if the vibration will balance out.  We're supposed to have some good weather heading in so I expect I can do that soon.  I suppose I should load it up with some weight for testing.

Now I have to get back on the pipe job I was waiting for a part that had to be replaced.

[Alberta Patriot]

Is there a panhard rod of sorts for lateral support in the plan. Even small amounts of lateral movement might set up a trailer sway situation that could get out of hand. Maybe just give the trailer a good hard rocking motion sideways to see how much deflection there is in the connecting parts..

[MarkT]

Is there a panhard rod of sorts for lateral support in the plan. Even small amounts of lateral movement might set up a trailer sway situation that could get out of hand. Maybe just give the trailer a good hard rocking motion sideways to see how much deflection there is in the connecting parts..

That's what I was talking about above and mentioning the pivot points being robust and they were tightened to remove any play.  I have the panhard bar on hand with heim joints but it looks to be redundant.   As I said there is no lateral movement even with a lot of force with a large pry bar, as I'm using the previous leaf suspension, fwd half, with shocks replacing the back half. Wikipedia says

"panhard bars are not usually used with a leaf spring suspension, where the springs themselves supply enough lateral rigidity, but only with coil spring suspensions."

  I'm taking it for a test drive tomorrow when it gets warm to confirm it's good to go on the Inzane ride.  There will be several more test rides locally after that as well, before June.  I also have the right wrenches in my toolkit if they should need tightening on the road.  BTW another purpose of the large cooler mount frame is so I can add plenty of weight to the towbar to prevent trailer sway.  I found on the Morganville ride, the Timeout camper had far too little tongue weight and would sway with minor provocation from wind gusts.  I had to stay a quarter mile back from trucks on the slab and keep speed 65 or less to prevent that.  After returning I removed the streamline fairing so I could install a large cooler frame - now can load that up with drinks and ice to a hundred pounds - no sway issues after that.

As an aside - REALLY nice to have the cargo capacity of a trailer, and a cooler full of iced-down water bottles on a road trip.  Super convenient to just throw your stuff in the trailer and go w/o having to carefully pack it onto a bike and bungie stuff down. Not to mention the security of a locked trailer. Having got used to that I probably won't do road trips anymore w/o a trailer & cooler.

[MarkT]

Took the trailer on a spin yesterday, first empty then with about 200# in it.  The trailer no longer bounces wildly when hitting big bumps.  The buzz in the handlebars is gone, so the Ride-On appears to be balancing the tires.  There was no sway going on empty or loaded, while I did not install the cooler and load it up to ensure plenty of tongue weight.  There was no damage to the load though I put some sensitive material in there - pills - but the ride was not long enough (eg. thousand miles) to mean much. Pushing down on each side while loaded, seemed like the suspension was positioned approximately in the "sweet spot".

I conclude this mod is a good one - and inexpensive for me, as I had a spare set of Valkyrie OEM shocks, and other steel parts already on hand.  If you have this trailer from HF - or another one with a too-stiff leaf suspension - I recommend, do this mod, it will preserve what you haul in it, from vibration on long rides.