Trailer: Conversion to Torsion Spring Axle from Leaf Spring Axle

Repair or modification of Boston Whaler boats, their engines, trailers, and gear
dtmackey
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Trailer: Conversion to Torsion Spring Axle from Leaf Spring Axle

Postby dtmackey » Thu Jan 20, 2022 10:26 pm

My 1986 15-footer is on an original Shoreline galvanized trailer. After I bought the boat, I went through the trailer; it's very solid and will last longer than me. The trailer has leaf springs. The springs are the slipper-type, and when going over a bump the trailer makes noises like it's coming apart.

The trailer is solid--and this is a function of the spring setup; maybe I'm more in-tune with noise and don't like it. The trailer has the typical welded C-channel galvanized frame. I plan to convert to a torsion-spring axle. I believe a torsion spring-axle has many advantages and will provide the quiet and smooth ride I prefer.

I already have a source for new axles, and I have an idea on fabricating brackets. I would love to find an off-the-shelf bracket rather than making my own.

I would appreciate any advice from someone who has made a conversion to torsion-spring axles from leaf springs.

I was going to buy a new aluminum trailer until I priced them and was shocked at the prices.

D-

jimh
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Re: Trailer: Conversion to Torsion Spring Axle from Leaf Spring Axle

Postby jimh » Fri Jan 21, 2022 10:07 am

Another advantage of using a torsion-spring axle in place of a leaf-spring axle should be less rust corrosion, particularly if used in saltwater launching and loading. The components on my trailer with the most rust are the leaf springs.

I am not familiar with the "slipper-type" leaf spring. Perhaps you can elaborate on that variety.

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Phil T
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Re: Trailer: Conversion to Torsion Spring Axle from Leaf Spring Axle

Postby Phil T » Fri Jan 21, 2022 10:15 am

D--my box-framed trailers have a torsion-spring axle. It has a plate that is attached to the frame using U-bolts.

Isn't a torsion-spring axles sold with a plate or bracket included?

torsionSpringAxle_.jpg
Fig. 1. Torsion-spring Axle with brackets.
torsionSpringAxle_.jpg (15.47 KiB) Viewed 3980 times

Source: https://www.loadrite.com/trailer-parts/axle-assemblies-and-components/axle-assemblies-weldments-spring-torsion/1500lb-oem-torsion-axle-assembly-45-frame-centers-knott/
2.25-inch square, full, galvanized steel axle and hub assembly
with 1.06-inch diameter straight spindles
and pre-greased hubs with 5 of 4.5-inch bolt pattern
built with bearing king 1.06-incg
Price: $416.42
Wt: 70-lbs
Capacity: 1,500-lbs

2.jpg
Fig. 2. Torsion-spring Axle another view.
2.jpg (29.66 KiB) Viewed 3972 times
1992 Outrage 17
2019 E-TEC 90
2018 LoadRite 18280096VT
Member since 2003

jimh
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Re: Trailer: Conversion to Torsion Spring Axle from Leaf Spring Axle

Postby jimh » Fri Jan 21, 2022 10:44 am

Is there only one spring for the whole axle?

dtmackey
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Re: Trailer: Conversion to Torsion Spring Axle from Leaf Spring Axle

Postby dtmackey » Fri Jan 21, 2022 12:10 pm

jimh wrote:I am not familiar with the "slipper-type" leaf spring. Perhaps you can elaborate on that variety.


Slipper spring is restrained on end with a bolt and the other with two metal tabs bent over that allow the spring to slip. This slip fit is loose and makes lots of noise over the simplest of bumps and not smooth at all.

Image
Fig. 3. Diagram of trailer with slipper springs highlighted in red outline circle.

This is not my trailer, but also provides a sense of the frame C-channel.

D-

dtmackey
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Re: Trailer: Conversion to Torsion Spring Axle from Leaf Spring Axle

Postby dtmackey » Fri Jan 21, 2022 12:11 pm

jimh wrote:Is there only one spring for the whole axle?


Both sides (L&R).

dtmackey
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Re: Trailer: Conversion to Torsion Spring Axle from Leaf Spring Axle

Postby dtmackey » Fri Jan 21, 2022 12:14 pm

Phil T wrote:D--my box-framed trailers have a torsion-spring axle. It has a plate that is attached to the frame using U-bolts.

Isn't a torsion-spring axles sold with a plate or bracket included?

torsionSpringAxle_.jpg
Source: https://www.loadrite.com/trailer-parts/axle-assemblies-and-components/axle-assemblies-weldments-spring-torsion/1500lb-oem-torsion-axle-assembly-45-frame-centers-knott/
2.25-inch square, full, galvanized steel axle and hub assembly
with 1.06-inch diameter straight spindles
and pre-greased hubs with 5 of 4.5-inch bolt pattern
built with bearing king 1.06-incg
Price: $416.42
Wt: 70-lbs
Capacity: 1,500-lbs

2.jpg


Thanks Phil, That's similar to other trailers I own. Box frame trailers are easier to swap over, C channel tends to be narrower at the contact point. I'm considering an additional galv heavy angle piece to provide more contact and also spread the load since the inside of C channel is strong, but the outside lip has less strength.

D-

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Phil T
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Re: Trailer: Conversion to Torsion Spring Axle from Leaf Spring Axle

Postby Phil T » Fri Jan 21, 2022 12:15 pm

Sorry D for the tangent.

A torsen axle does not have a spring. Deflection is provided by the twisting of the axle bar inside a square sleeve lined with rubber compounds. Each wheel is independent.

Screen Shot 2022-01-21 at 12.13.39 PM.png
Fig. 4. Torsion axle diagram.
Screen Shot 2022-01-21 at 12.13.39 PM.png (176.04 KiB) Viewed 3959 times


Source: https://www.kendonusa.com/blogs/blogs/k ... rsion-axle
1992 Outrage 17
2019 E-TEC 90
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dtmackey
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Re: Trailer: Conversion to Torsion Spring Axle from Leaf Spring Axle

Postby dtmackey » Fri Jan 21, 2022 12:32 pm

Phil T wrote:A torsen axle does not have a spring. Deflection is provided by the twisting of the axle bar inside a square sleeve lined with rubber compounds. Each wheel is independent.


To tag onto what Phil posted, the rubber in the axle does a great job absorbing impact while providing wheel travel. Also having each wheel independent without a steel axle connecting each spindle is highly desired. The difference in ride is night and day.

D-

TreyWeitzel
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Re: Trailer: Conversion to Torsion Spring Axle from Leaf Spring Axle

Postby TreyWeitzel » Fri Jan 21, 2022 2:32 pm

I have not converted any of my trailers from leaf spring to torsion, however, I did purchased a new trailer for my 13 Dauntless in 2021 and opted for a torsion axle. The difference in ride quality over my old leaf-spring trailer for that boat is night and day; the torsion axle ride is quieter and smoother.

The cost of the 14-16-foot Load-Rite trailer was around $1,800. For a 13-foot Boston Whaler boat the trailer is big. I have adjusted it [to fit the boat].

And [the larger trailer] gives me room to grow [into a larger boat].
1997 Boston Whaler Dauntless 13'
1990 Boston Whaler 9' Tender
1982 Boston Whaler Harpoon 4.6

dtmackey
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Re: Trailer: Conversion to Torsion Spring Axle from Leaf Spring Axle

Postby dtmackey » Fri Jan 21, 2022 2:45 pm

TreyWeitzel wrote:...I did purchased a new trailer for my 13 Dauntless in 2021 and opted for a torsion axle. The difference in ride quality over my old leaf-spring trailer for that boat is night and day; the torsion axle ride is quieter and smoother....The cost of the 14-16-foot Load-Rite trailer was around $1,800.


Thanks Trey--I was quoted $2,400 on a new aluminum trailer for my 15-footer. If I upgrade I would make the jump to aluminum. When I started trying to cut down that price, I was taking away the things that I considered a "must have" and on my trailer now:
  • LED lighting
  • Spare tire and mount
  • Stainless hardware
Considering the only thing I don't like with my current trailer is the axle, so I'm going to spend $200 to $300 to upgrade to a torsion spring axle.

D-

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Phil T
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Re: Trailer: Conversion to Torsion Spring Axle from Leaf Spring Axle

Postby Phil T » Fri Jan 21, 2022 3:19 pm

Trailer prices have just gotten stupid. Crikey.
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jimh
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Re: Trailer: Conversion to Torsion Spring Axle from Leaf Spring Axle

Postby jimh » Sat Jan 22, 2022 12:41 pm

I think the proper name for an axle that absorbs up-down wheel movement loads by twisting is a torsion axle.

There is a bit of confusion in this thread with the term TORSEN axle, which is an ingenious differential power driven axle arrangement. TORSEN is a word derived from TORque SENsing.

More on TORSEN axles: https://en.wikipedia.org/wiki/Torsen

There is also more confusion about torsion bar suspension. Torsion bar suspension uses a twistable bar fixed at one end and twisted at the other end by the individual wheel. There is no rubber involved. It was used by Chrysler cars at one time. This gave independent suspension characteristics to each wheel. More at https://en.wikipedia.org/wiki/Torsion_bar_suspension

In the system shown above, it looks like the axle is a square bar that twists against rubber cushions encased in a larger square tube.

Q5: Is the bar fixed in position in the center of the axle?

If not fixed, it would seem that the suspension of the two wheels, each one attached at opposite ends, would then interact. The torsion spring becomes one spring shared among two wheels. For example, suppose the right wheel encounters a displacement of two-inches upward. This twists the bar and loads up the rubber. Now the left wheel encounters a three-inch displacement upwards. That wheel wants to twist the bar even further. The absorption of the twisting depends on compressing of the rubber cushions. The rubber cushions cannot always exhibit a linear resistance to compression--at some point they won't be as easy to compress as they were initially when not compressed at all. At some point it will be very difficult to compress them. On that basis, the resistance to compression--this is the force that supplies the spring effect if the axle itself is not fixed in the middle--for one wheel depends on where the other wheel is. Also, consider the case if the wheels want to move in opposite directions, one up and the other down. One adds compressive force, the other removes compressive force. Who wins? It is here that I think the square axle must twist to compensate. The square axle is the torsion member, and the rubber cushions are the springs.

Actually, I think the proper name for this approach is a twist-beam suspension. Compare at https://en.wikipedia.org/wiki/Twist-beam_rear_suspension

PatSea
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Re: Trailer: Conversion to Torsion Spring Axle from Leaf Spring Axle

Postby PatSea » Tue Jan 25, 2022 2:51 pm

We have our 13' Boston Whaler on a galvanized trailer with torsion axles. The trailer is very quiet as some have noted. So I like the torsion flex axle from a noise standpoint. The only feature that I don't like is it is a Knott axle with sealed bearing hub assembly. There is no way to grease the bearings with bearing buddies as it is a sealed system. I haul the boat each winter from Ohio to Florida and would feel more comfortable if I could add grease to the bearings as necessary. Or reeplace just the bearings if that was all that was needed.. As it is I carry a new replacement Knott bearing hub assembly with me in case I have a failure. I have changed out the bearing hub assembly once in my garage and it was somewhat of a challenge. I would hate to have to do a replacement while making the trip back and forth to Florida.
I took the trailer to a trailer shop last winter and the owner indicated that the rubber torsion inserts can be replaced by a few qualified shops.

RichS
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Re: Trailer: Conversion to Torsion Spring Axle from Leaf Spring Axle

Postby RichS » Tue Jan 25, 2022 11:51 pm

I made this conversion about a year ago on my Karavan trailer which carries my 1988 18' outrage and am very happy with the results. It rides much smoother and quieter. I also think it is a simpler setup with fewer parts and everything is hot dipped galvanized (no rusty leaf springs). It took a while to find an axle with the right capacity and bracket spacing to match the frame rail spacing. Since the axle U bolts directly to the frame rails, it becomes an additional structural part of the trailer. Another consideration is the spacing between the axle and the boat which will be closer than an axle hanging on a set of leaf springs. Since there is little or no axle movement in relation to the boat, you don't have to worry about an axle hitting the boat if you bottom out the leaf springs on a pothole, speed bump, etc. In my case, I used an axle with a dropped center section to get the needed clearance. One of the few negatives with a torsion axle is that they may not be repairable and at some point may need to be replaced. Given the potential for a greatly extended life and little to no maintenance, I think the positives outweigh the negatives.
I hope this helps.

dtmackey
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Re: Trailer: Conversion to Torsion Spring Axle from Leaf Spring Axle

Postby dtmackey » Sun Jan 30, 2022 10:31 pm

I'm going to hold off any decisions until the spring thaw since we just received 22-inch of snow. I did just buy new alloy wheels and tired and upgrades from the 4.10-12 size to a 5.30-12 along with new galvanized hubs, but it's possible a new axles will come with hubs as well.

One additional thing I did is the hub have studs and with typical trailer lug nuts the thread is exposes after the lug nut is installed and after repeated dunkings in salt water the threads start getting ugly. I do rinse my trailer and also grease the studs, but now I've gone with enclosed lug nuts so there's not exposed stud thread and salt water cannot come in contact with it. They are chrome plated steel with a stainless cap and I did the same to my snowmobile trailer that sees constant salt blasting all winter without so much as a rinse.

D-

jimh
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Re: Trailer: Conversion to Torsion Spring Axle from Leaf Spring Axle

Postby jimh » Mon Jan 31, 2022 7:15 am

Regarding the wheel hubs and the lug nuts: on my trailer the hubs have threaded holes. The wheels mount to the hubs with bolts that have a hex head with a taper. This eliminates any exposed threads. Compare at

https://www.northerntool.com/shop/tools ... _200809743

ASIDE: we missed the big snow storm, but the air temperature was down to minus-1-degree-F overnight Saturday. That's a cold day even for southern Michigan in the winter. It seems that when the air is that cold it's not conducive to big snow falls.

dtmackey
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Re: Trailer: Conversion to Torsion Spring Axle from Leaf Spring Axle

Postby dtmackey » Mon Jan 31, 2022 10:48 pm

jimh wrote:...on my trailer the hubs have threaded holes. The wheels mount to the hubs with bolts that have a hex head with a taper. This eliminates any exposed threads.

That's what I have now and I prefer studs as the threaded holes in a hub that accepts bolts are not blind holes and allow corrosion from the backside. My other reasoning:
  • I prefer to hang the wheel on the studs when changing a tire--not that it happens much as all.
  • With my new alloy trailer rims, stainless capped lug nuts give it that clean finished look.
  • My five other various trailers are all have stud hubs and I like keeping everything the same.
I'm very particular about some things and this is one of them. :-)

D-