Rear Axle Stiffener

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The rear axle on the Rialta is a Winnebago supplied weldment that uses VW wheel hubs and brake parts.  With the use of just the single tire on the rear, the carrying capacity is limited and thus the design of the rear axle does not anticipate any overload conditions.  Owners that have periodically overloaded the rear axle have noticed some bowing or bending of the axle tube which causes excessive wear on the inside edge of the rear tires.  This can easily be measure by holding a metal straight edge along either the top or bottom of the axle.  An un-laden vehicle is supposed to demonstrate a slight upward bow which is the camber to the tube created during the manufacturing process.  This provides about 1/2 to 3/4 of a degree of positive camber on the tires which is a normal design criteria.  The axle tubes are not supposed to bend or bow to any appreciable extent under normal loading conditions but it becomes clear that the Rialta's axle is the weakest link in the chain.

This modification proposes to remedy or avert the problem of the axle bending and the problem of excessive wear on the inside edge of the rear tires by installing angle iron or channel to provide additional strength and keep the axle from bowing or bending under heavy load.  This DOES NOT add any additional carrying capacity and at best only helps maintain the structural integrity of the axle.  While some engineers have told me it may not do any good, nearly all have said that it can do no harm.

Here are three such modifications done by Rialta owners:

 

 


 

 

Steel U-Channel Installation

This first installation used 3" wide steel U-channel but he failed to mention the length of the legs on the U-channel.  My guess is that the legs were 1-1/2" or 2".  The steel channel is mounted to the bottom only of the axle and the round U-bolts fit neatly over the top of the axle.  The disadvantage of this method is that the threaded portion of the U-bolts stick down and may reduce the ground clearance.  If the excess portions of the bolts are cut off, then they probably stick down no farther than other items on the Rialta such as the sewer pipes, spare tires, etc.

 

 

From:  Harry
Date:  Mon Nov 29, 2004  9:54 pm

I completed my version of the rear axle support or stiffening this weekend.

I used a 48" long piece of 3" channel iron which I clamped to the axle with 5 - 9/16" X 3" U-bolts.  The bolts are spaced with one bolt in the center and two bolts on either side.  I chose 5 rather than 6 bolts because I did not want to interfere with the brake line stand offs.  To help the channel set flat across the bottom of the axle I clipped off the lower leg of each brake line stand off.

For cross straps I used five 5" sections of 2" channel iron with 9/16" holes drilled for the U-bolts.

I used the 2" channel for cross straps because it is stronger than flat stock and gains additional thickness for the axle / channel iron package.  This additional thickness was necessary because the ready made 9/16" U-bolts are not threaded far enough to allow ample clamping action.  I wanted to use 9/16" "U" bolts to insure sufficient rigidity when the axle attempts to flex.

I also used hardened flat washers to prevent the lock washers from distorting when in contact with the softer channel iron when tension is applied.  I tightened the U-bolts as tight as I could with a 12" ratchet wrench.

I do not believe the change in clearance between the axle and the ground will have any negative effects because the wheels determine how low the axle can travel.

If any one has any questions I will do my best to answer them.

Harry P.
98 RD

 

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Steel Angle Installation

No pictures provided but this installation sounds nearly identical to the steel u-channel installation except instead of using a heavy steel U-channel, an angle iron shape is used instead.  The angle iron fits under the bottom of the axle much like a upside down "L" shape.  The long 2" vertical leg of the angle iron provides the stiffening required.

Bud, here are some particulars on the angle iron installation.  The angle iron is 2'' x 2'' size.  The length is such that it extends fully across the axle to the extent that each end reaches under the half cylinders that are welded on the top of the axle.  The "U" bolts are 3'' diameter by 6'' long.  They are just mild steel and I bought them at a hardware store.  I made the bottom clamps myself from 3/8' mild steel flat bar that is about an inch and a quarter wide.  The angle iron is placed on the bottom side of the axle.  The "U" bolts are placed on top of the half cylinders that are welded on top of the axle and you can slip them in between the axle and the brake lines on the back side of the axle.  The angle iron is oriented such that one leg is flat along the bottom of the axle with the other leg pointing down.  This orientation puts the vertical leg in tension when the axle tries to bow and thus the angle iron can never bend itself and provides maximum force to resist bowing of the axle.  At the very end on each side of the vertical leg only on the angle iron cut off just enough so that the "U" bolt clamps can be attached.  Really, what to do is fairly obvious and you shouldn't have any serious problems.  GOOD LUCK!!

Bob

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Stainless Steel Double U-channel Installation

The advantage of using this method is three-fold.  First, the stainless steel will never rust.  Second, the "double-box" provides more stiffening than just a single u-channel or angle iron.  And third, the u-bolt brackets can be pointing upward instead of downward thereby not creating any ground clearance problem.

Stainless steel was selected simply because it is stronger than regular steel and has the added benefit of not rusting.  I used a 2" wide x 1" high u-channel along the top and bottom of the regular axle tube to provide a "boxed beam" design.  The bottom piece is 48 inches long whereas the top piece is 42" long, the difference being the width rebound bumpers which can be seen just to the right of the top piece of channel in the photo.  There is one minor problem with using a u-channel along the top: one small metal bracket that holds two brake lines is welded just off the top left edge to the axle tube and it has to be cut or ground off to allow the u-channel to fit.  Once the u-channel is fitted in place, the bracket can be re-welded in position or a product such as "J-B Weld" can be used to attach and hold it in position.  You can see this towards the far left side of the top piece of u-channel.

A standard axle tube has an O.D. of 2-3/8" which is exactly what the Rialta has so there are standard suspension u-bolts available made to precisely go over the 2-3/8" axle.  Typically these are high strength steel rods with a diameter of either 3/8" or 1/2".  There are even square shaped u-bolts that are available that would have looked better on my double-channel "boxed beam" shape, but I could not find any square shaped u-bolt in a stainless material so instead I opted to use the regular round shape.  Granted, it does not conform to the square shape of the u-channel but once the bolts are tightened, the u-bolts do not slip and do not deform shape.  I used 3/8" diameter stainless steel u-bolts and torqued the stainless heavy hex nuts to 40 ft/lbs.  A stainless angle was used as the pressure plate and the extra leg on the angle prevents the plate from bending down when the nuts are tightened.  Once the torque settings were accomplished, a jack nut was snugged up from the underside of the angle plate to prevent any movement or distortion.  The excess length of the u-bolts can be cut off if desired, but I choose to leave them alone as they are far from hitting anything even if the suspension system is completely bottomed out.

Please note that these are all home made items and unless you live in a major metropolitan area, you may have some difficulty in finding local sources for similar materials in a stainless finish.  Also be aware that there is a significant premium cost increase for the stainless material over the regular steel.  You may wish to contact a specialty plumbing or pipe-fitting contractor that specializes in such jobs as dairies, food processing plants, etc.  You won't find this type of material at your local hardware store or even Home Depot or Lowe's.

Installation by Baldy, 2000 HD, August 2005

 
Here's an end view of the stainless u-channel used.
 
The 4 stainless u-bolts, angle plates, and hex nuts.
 
The finished installation.  Note the bottle jack in the center of the axle as it temporarily supports the entire axle as the fasteners are torque down to this cambered position.

 

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Page Updated: 19 February 2015