Questions about ride height.

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Questions about ride height.

Postby TinKicker » Thu Jan 01, 2009 1:25 am

For obvious appearance reasons I'd like to figure out how low my tear design will ride when completed and loaded so as to get the best look. Is there a compiled chart anywhere showing amount of drop with a particular type of axle (say, a #1200 tru-flex) and varying amounts of weight? Can anyone tell me a rule of thumb for how much drop to figure for say, every 100lbs?
This info would help me figure the capacity axle I need (not too stiff or soft) so that I could in turn revise structural plans accordingly.
If you know that this subject has already been covered, please direct me there.
Peace. And Happy New Year!
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Postby angib » Thu Jan 01, 2009 11:32 am

Sorry, it won't be as simple, as you want!

I've never seen load/deflection tables like you want for any axle (and I haven't heard of Tru-Flex before) - at best all you'll get is the ride height unloaded and the ride height at full rated load, which does at least give you a max and min.

The problem is that the rubber torsion axle should have a 'rising rate' loading curve - the axle should be soft to start and then get stiffer as more load is put on it. However the experienced folk like Grant and Cary who've commented about this say that they work the other way around - not much movement to start with, and then movement when there's a good load on them.

So yer pays yer money and takes yer pick.

If you want to get the ride height just right, you'd better get a Flexiride axle that will allow you to fine tune the right height after construction by moving the arms on the splined axle.

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Postby Steve_Cox » Thu Jan 01, 2009 1:05 pm

You might be over thinking this "problem". I have a Flexiride 2000# axle with about a 1500# load. The ride height change was insignificant compared to the ride height change in the tow vehicle, a Honda CR-V, with all the camping gear loaded in the back. uh oh.... maybe I just added a new variable to the equation. :lol:
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Postby TinKicker » Sat Jan 03, 2009 1:27 am

Andrew, I believe I meant to say "Torflex", though there's no telling what I might call it in the future. You all will just have to do like I do with my automotive customers and "interpret" what I really mean. :lol:
I'm referring to the Dexter axle. I suppose since no one has compiled the info I need I'm down to two choices:
1) Build 20 or so teardrops identical in every way except for a sequential increase in weight of #50 each. Examine the amount of drop on each and keep the one I like, destroying the rest.
2) Get a Flexiride.
Steve, I KNOW I've seen this in my travels within this forum, but about how much of a price difference can I expect between the Flexiride and equivalent Dexter?
Yes, mama always said I was an over thinker. Sometimes I do it to the point of never getting anything done, but my mental picture of the thing sure looks good. :) And thinking is even cheaper than talking!
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Postby Steve_Cox » Sat Jan 03, 2009 11:12 am

TinKicker wrote:Steve, I KNOW I've seen this in my travels within this forum, but about how much of a price difference can I expect between the Flexiride and equivalent Dexter?


I know I've seen it here a bunch of times but can't remember the difference exactly, and I'm not motivated today to look it up :lol: But I would guess it is $75 - $100 more for the Flexiride. I bought it for the adjustable feature, but due to my expert planning and design, it came out perfect so no adjustment was needed. :lol:
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Postby angib » Sat Jan 03, 2009 11:51 am

I doubt you could measure a different ride height for a 50 lb change in trailer weight. This Dexter chart gives you quite a bit of the information you need:
http://i.b5z.net/i/u/1080235/f/Torflex_ ... n_4-04.pdf

Looking at the first line of the first table on page 1, just as an example, you'll see the 'H' dimension (which is the ride height, minus the wheel/tyre radius) varies between:
3.8" at no load
2.4" at full load
1.9" at shock load

My guess is that 'shock load' is at least 2G - so at least doubling the weight of the trailer is moving the suspension just 0.5" - and removing all the trailer weight only increases the ride height by 1.4".

These changes are not much more than the change in the wheel/tyre radius under load - a typical 205/75R14 tyre loses 1.5" of its radius at full rated load (not that any teardrop will fully load that size tyre).

So as long as you don't guess/estimate a trailer weight that's half or double the eventual weight, the suspension movement with weight shouldn't be a big deal - with a Torflex (or any fixed angle axle) getting the right start angle is more important.

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Postby madjack » Sat Jan 03, 2009 12:11 pm

TK, my experience has been about a 1/2"-1" difference between bare frame and completed TD...and Steve is right, it is about a 100USD difference between the Flexi-Ride and the Tourqflex (Flexi the more expensive)...I believe the Flexi MAY be the better quality unit...maybe...by just a little
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Postby brian_bp » Sun Jan 04, 2009 1:04 pm

angib wrote:...
The problem is that the rubber torsion axle should have a 'rising rate' loading curve - the axle should be soft to start and then get stiffer as more load is put on it. However the experienced folk like Grant and Cary who've commented about this say that they work the other way around - not much movement to start with, and then movement when there's a good load on them...

I agree that the rubber's deflection is probably rising-rate, but I don't doubt the practical observations. I suspect what is going on is that these suspensions are usually used with a starting angle significantly below the horizontal, and the falling-rate behaviour is the result of the arm getting closer to horizontal.

But as already noted, trailer suspensions are so stiff that it won't make a lot of difference! This is not just true of rubber suspensions: the whole range of travel in the common leaf-spring suspension (equivalent to a Dexter D35) under my travel trailer is not much greater than the Torflex numbers.
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Postby TinKicker » Sun Jan 04, 2009 8:58 pm

Thanks, all of you, for the information. I went out and jumped up on my little 4x8 tilt-bed utility trailer and realized what you're all saying is true...not much deflection at all! (That's no small thing with MY mass :lol: )
I guess I have been overthinking the problem, but I hated the thought of building with an axle height that I wouldn't have been happy with if I had to throw in more equipment than I had planned on.
I believe I was trying to compare the trailer suspension with vehicular suspension...I can step up on my Tacoma's rear bumper and the deflection is much more noticeable than the trailer's. Of course, we actually have to RIDE in vehicles, don't we? Makes sense that it's cushy, huh? :?
So, one more desperate worry off my list. As far as axles go, I'll just use the cheaper Dexter and simply plot out the angle carefully.
Thanks again, fellows!
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Postby halfdome, Danny » Sun Jan 04, 2009 11:45 pm

You can adjust your ride height with different tire sizes too. A 205 75 R15 is 27" tall and a 195 65 R15 is 25" tall. I had to go with the shorter tire until I figured I could lift the chassis with a piece of tubing to clear my fenders. When ordering your Dexter torsion axle it is advisable to order it with the removable mounting brackets. There's not an extra charge for them. I was able to lift my axle 3" with an extra set of brackets and some tubing. This demonstrates that you can lift or lower your ride height with a Dexter Torsion axle a couple inches if needed. I've dialed in the correct degree on my current build, I hope. :D Danny
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Postby TinKicker » Mon Jan 05, 2009 5:20 pm

Danny, I guess sometimes the best answer is the simplest. This is one of those "why didn't I think of that?" moments. :lol:
You did a good job on that setup, though if you're like me with my projects, you can nitpick it to death. Simple and functional beats worrying out 15 different overthought approaches any time.
Thanks a lot for the idea! :thumbsup:
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Go ahead and get your project started because it's just like having kids...if you wait to start until you're skilled enough or rich enough, you'll never do it. And just look at what you'd miss!
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In planning any project you've never attempted before, always allow for the three three's: It will take you three times longer, three times more material, and three times more money than you thought.
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Postby Alphacarina » Wed Jan 07, 2009 5:17 pm

If you're pulling with a small car, design your trailer to be as low as you can make it and it still won't be too low. Mine with a HF frame, reversed axle and 13 inch tires is still higher off the ground than I would like

If you're pulling with a pickemuptruck, you may have to think on it a bit more ;)

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Postby TinKicker » Wed Jan 07, 2009 6:36 pm

Now that I think about it, since I'm pulling it with my Toyota, really low probably wouldn't look too good. I was thinking more about sitting in the doorframe and tieing shoes, but I guess that's not that critical or hard to accomplish. As long as it's not too tall.
Don, I thought about flipping an HF type axle, and wondered how much that would really lower things. How much did it drop yours?
I could always make the thing LOOK lower by extending the sidewalls down and building storage under the frame to keep from wasting that area.
It blows my mind to realize I didn't even think about how my Tacoma would look pulling a really low trailer. Not to mention the ball drop I'd have to rig up. Thanks for the idea. I may just get some wheels and tires as tall as my truck's and set it up tall. It's all paper tigers right now anyway.
Peace. :thumbsup:
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Go ahead and get your project started because it's just like having kids...if you wait to start until you're skilled enough or rich enough, you'll never do it. And just look at what you'd miss!
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Postby Alphacarina » Sun Jan 11, 2009 6:23 pm

Flipping the axle dropped mine about 3 inches - You'll have to notch the spring mounts so the axle doesn't hit them

You can always design your tongue for a 'taller' hitch - Getting the trailer down inside the wind shadow of the tow vehichle sure helps with gas mileage . . . .

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Postby TinKicker » Mon Jan 12, 2009 9:56 am

Don, I agree with the wind drag comment. I guess I shouldn't overthink everything so much, but with my projects I don't like wasting time or money (which I seem to do too much of anyway) so I hate to think I'd have to go back and reengineer something. I need to just build it and then correct the flaws on teardrop #2! :twisted:
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Go ahead and get your project started because it's just like having kids...if you wait to start until you're skilled enough or rich enough, you'll never do it. And just look at what you'd miss!
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In planning any project you've never attempted before, always allow for the three three's: It will take you three times longer, three times more material, and three times more money than you thought.
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