flipping axel to the top of the leaf spring

Silvertip

Supreme Mariner
Joined
Sep 22, 2003
Messages
28,771
Re: flipping axel to the top of the leaf spring

To refine this flipping business some more, you can flip any straight axle -- we are all clear on that. If you buy a cambered axle without spring perches, they can be welded on top or below the axle for below axle or above axle mounting so that's not an issue either. But unless you cut off the old perches on an existing cambered axle and install new ones you cannot flip a cambered axle for the simple reason the perches are in the wrong position. I suppose I should clarify what a cambered axle is for those that don't know. Take a straight axle and put a slight bend in the middle. The purpose of this is to allow the wheels to take a slightly "cambered" stance (tilted in at the bottom and out at the top) so when the trailer is fully loaded, axle and suspension flex allows the wheels to run closer to straight up. Thats why you need to specify an "oversprung" or "undersprung" axle when ordering a new cambered axle. They are not interchangable. Here is a diagram of an axle mounted over the spring. The rectangular block between the spring and the axle is a spring perch which is welded to the axle. If this was a straight axle (no bend in it) you could simply rotate it 180 degrees and install it beneath the springs. However, if it were a cambered axle, rotating the axle 180 degrees would place the bend in a downward rather than upward direction so a sever camber issue would exist. If a simple through hole is used in the axle and spring perches are not used, then flipping can be done.

spring.jpg
 

htv

Seaman
Joined
May 4, 2009
Messages
73
Re: flipping axel to the top of the leaf spring

Axles mounted underneath the spring create more of a leverage factor on the spring tie bolt. Shear a tie bolt and your axle will spin all away around, whereas an axle on top of the spring is less likely to shear the tie blot but if it does your axle is confined within your spring shackles and bolts and the trailer frame. Shear strength of your u-bolts trump shear strength of a measly 5/16"-3/8" tie bolt.
 

skargo

Banned
Joined
Sep 14, 2008
Messages
4,640
Re: flipping axel to the top of the leaf spring

Axles mounted underneath the spring create more of a leverage factor on the spring tie bolt. Shear a tie bolt and your axle will spin all away around, whereas an axle on top of the spring is less likely to shear the tie blot but if it does your axle is confined within your spring shackles and bolts and the trailer frame. Shear strength of your u-bolts trump shear strength of a measly 5/16"-3/8" tie bolt.

If by tiebolt you mean centering pin, I wouldn't sweat it. I put WAY more force rock crawling my sprung over suspension on the rear of my offroad rig, than a trailer will ever see.
 

htv

Seaman
Joined
May 4, 2009
Messages
73
Re: flipping axel to the top of the leaf spring

If by tiebolt you mean centering pin, I wouldn't sweat it. I put WAY more force rock crawling my sprung over suspension on the rear of my offroad rig, than a trailer will ever see.
Like hitting a curb "crawling" at 60mpg? Or a pothole at 60mph?
 

skargo

Banned
Joined
Sep 14, 2008
Messages
4,640
Re: flipping axel to the top of the leaf spring

Like hitting a curb "crawling" at 60mpg? Or a pothole at 60mph?

It used to be street legal and hit potholes at 60, I don't follow. :confused:
 

jeeperman

Lieutenant Commander
Joined
Aug 2, 2001
Messages
1,513
Re: flipping axel to the top of the leaf spring

which one is a "tie bolt"?
 

mchin

Petty Officer 2nd Class
Joined
Jun 15, 2007
Messages
195
Re: flipping axel to the top of the leaf spring

Thanks for all the good advise. I'm hearing that if I do decide to flip it, I should make sure I have good clearance (fenders are frame mounted), upgrade my shackles ( had to do that anyway) and make sure the axel is true, which was previously done with a centering pin. The some of the ramps here in jacksonville are shallow and at low tide, your rear tire wheels are in the water, long before the transom of the boat is even wet. Which is why some people flip their axels. Given my boat weight and lack of engineering knowledge (I'm surely not smarter then the engineer who designed the Continental trailer) I'll probably buy new springs, and mount it the way it is now, under the springs. I'll cut the rear of my bunks at an angle to help retrieval and I'll be sure to move my bunks back a tad to ensure support for my transom.

Thanks again.
 

jay_merrill

Vice Admiral
Joined
Dec 5, 2007
Messages
5,653
Re: flipping axel to the top of the leaf spring

I argued on the side of caution and realization that the stresses involved have to be understood. I still believe that.

In spite of this, I would contact Continental to see what they think. Spring-over arrangements are not unusual, so they can be done. The trick is to do them properly. Anecdotal advice is nice, but getting an opinion from someone who designed your trailer, or someone who at least has enough real expertise to tell you what you should and shouldn't do, might make the difference in your decision.



???
 

jeeperman

Lieutenant Commander
Joined
Aug 2, 2001
Messages
1,513
Re: flipping axel to the top of the leaf spring

if you have 15" rims and changed to 10" rims you could drop the trailer about 4".
But 10" rims wont clear disc and some drum brakes.
You might also be able to adjust your bunks down a little or rip them lengthwise to take some off the top.
 

109jb

Lieutenant Commander
Joined
Jul 15, 2008
Messages
1,590
Re: flipping axel to the top of the leaf spring

Just go to a spring shop and tell them the gross weight of the trailer, the diameter of the axle tube, and tell them you are going to make it a "spring-under" suspension. Tell them you want their suggestion for u-bolt diameter. They can then make you the appropriate size u-bolts. The spring shops have the experience to do this for you and most work on everything from cars and small trailers up to 18-wheelers. Spring shops can be found in most larger towns and cities.

If the axle is not cambered then you can just put it on the top of the springs using the existing perches. If it is cambered, you either have to do something like the dexter kit, or you take it to the spring shop when you get the u-bolts and they can cut the existing axle perches off and weld new ones on the opposite side. Or, get a new axle.
 
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