Torsion bar tension, and longevity -

mickmanor · 10-27-2021, 06:56 AM

My question is about how much tension is retained in the torsion bars over how long of a time period in years.

For example, if camper A stores his TM in the raised position all year long, and lowers the camper for travel purposes only, the torsion bars will have Ax amount of "spring power" after ten years.

Then, camper B stores his TM in the lowered position for a few months of the year and the torsion bars are kept in the compressed position. Those torsion bars will have Bx amount of "spring power" after ten years.

I realize that probably little testing has been done on torsion bar tension retention, but maybe somebody has been able to determine that storage somehow might affect the spring tension property of the torsion bars.
Any old-timers with lots of experience might understand what I'm talking about.

Hypotheticals:

Will camper A have full tension retention for 10 to 20 years?

Will camper B have to adjust the torsion bar tension every couple of years and then lose tension over 15 years?

I cannot imagine how the thick tension bars can retain tension similar to a special made machine spring, and wonder if the tension retention concept is similar.

**Larryjb** · 10-27-2021, 12:09 PM

My 2001 2720 has all original torsion bars except for the two front ones. When I replaced them it turned out that the original ones were the incorrect size for the options on the trailer. I suspect that the awning was added by the dealer without upgrading the torsion bars.

All other torsion bars are still half way or less in their adjustments, meaning that after 20 years they are holding up well.

I'm sure that you are right that they lose some spring over time. The ability to adjust them allows us to compensate for this loss.

**rickst29** · 10-27-2021, 01:27 PM

A 2619 from 2006, the front-most pair of the front shell are now inadequate for lifting (and have no "tuning" room left).

All other pairs have lots of remaining power, and lots of remaining adjustment room. The front-most pair may have possibly been mis-chosen at build time.

I always store in closed position.

Shane826 · 10-27-2021, 06:55 PM

Interesting question. I would imagine the camper stored in the open position would have better torsion spring retention as there is little to no tension on the torsion bars in the open position. But that is purely hypothetical.

**Larryjb** · 10-27-2021, 08:41 PM

Quote:

Originally Posted by rickst29

A 2619 from 2006, the front-most pair of the front shell are now inadequate for lifting (and have no "tuning" room left).

All other pairs have lots of remaining power, and lots of remaining adjustment room. The front-most pair may have possibly been mis-chosen at build time.

I always store in closed position.

Can you measure the diameter of your front torsion bar on the awning side? This was the incorrect one on my TM.

**rickst29** · 10-31-2021, 12:41 PM

Quote:

Originally Posted by Larryjb

Can you measure the diameter of your front torsion bar on the awning side? This was the incorrect one on my TM.

I don't have an awning, and the "lift power" is pretty even on both sides. The front shells utilize the 82" lengths, so there are only 3 possibilities (11/16, 3/4, and 13/16 bar widths). When I measured, with paint and possibly paint bubbles, each of the two bars was "right around" .7536 inches in total.

(Although squeezing my micrometer more, or less, completely overwhelms the "accuracy" of that last digit.)

11/16 is only .6875 inches, and that measurement probably corresponds to two additional paint layers about 3/100 inches thick. (A "3/4 bar" would have had thicker paint than 18 ten-thousandths of an inch, so I think that they are not 3/4 bars.) Upgrading into 3/4" bars, parts # 40017 and 40018 (from the 2018 parts catalog) would seem to fit the bill, if I wanted to pay for all the freight and then hassle with the installation.

But your install procedure sounds pretty intimidating, even when optimized by experience - so I think I'll skip doing that job for now. If it ever becomes too difficult to lift when "assisted" be pre-lowering, pre-raising the front jack - then I'll either go ahead and do it, or try to schedule a Service Visit somewhere good (such as the S.D. factory).

**Larryjb** · 10-31-2021, 11:11 PM

It was quite a bit of work on my part to lift the shells. However, I saw a post earlier of some guy who did the job more cleverly. Build a frame that fits securely underneath the front shell around the hitch area. Make sure it's solid both fore/aft and braced so that it won't swing sideways (diagonal bracing). Build it so that you can lower the front of the trailer using the trailer jack. As you begin to lower the front of the trailer, loosen the acorn nuts securing the shoulder bolts that go through the lift arm. Once those are out, you can continue to lower the trailer, effectively raising the shell. Just be careful that the lift arms don't "snag" on anything as you do so. I had one oops which started to separate the side wall from the roof! I thought things were toast until I realized there are only about 3 #10 screws holding the entire side wall to the roof. I reinforced this, and all was good.

**rickst29** · 11-01-2021, 08:27 AM

Quote:

Originally Posted by Larryjb

It was quite a bit of work on my part to lift the shells. However, I saw a post earlier of some guy who did the job more cleverly. Build a frame that fits securely underneath the front shell around the hitch area. Make sure it's solid both fore/aft and braced so that it won't swing sideways (diagonal bracing). Build it so that you can lower the front of the trailer using the trailer jack. As you begin to lower the front of the trailer, loosen the acorn nuts securing the shoulder bolts that go through the lift arm....

My HOA would have a fit if I constructed a larger frame with lots of side bracing - but, if I build a box frame with triangle ties at all the front corners, it would have equivalent strength - and not move, if anchored into the ground at the four corners (at the sides of the driveway). For front/back I could anchor the longer "side" members to the tire blocks.

That's a great scheme, much better than my original thoughts of RAISING the front. (I'm still not doing it within the next two years, but it seems more do-able.)