Changing from single to tandem axle

DStraitwell

Cadet
Joined
Jun 12, 2010
Messages
6
Hey guys: have a question for the trailer people. I am going to renovate my Dilly boat trailer. Going to move my single axle forward and add a rear axle. What kind of problems might I encounter? And what is an equalizer? Thanks Don
 

180shabah

Rear Admiral
Joined
Mar 26, 2005
Messages
4,995
Re: Changing from single to tandem axle

Well, an equalizer basically allows the trailing end of the front spring and the leading end of the rear spring to be mounted to a single pivot point. When one axle moves up, it pushes down a little on the other axle.

Alignment can be an issue when "just adding" a second axle. You can buy a plate that has the mount points for both axles, and just bolt it to your trailer.

Also, watch your load ratings on everything.
 

Silvertip

Supreme Mariner
Joined
Sep 22, 2003
Messages
28,758
Re: Changing from single to tandem axle

Visit Champion Trailer on-line and look in the suspension part of their catalog. They show typical suspension systems. The equalizer is also called a walking beam since it allows the front and back wheels on each side to "step" over obstacles relatively independently while still maintaining equal loading of each tire. You do realize lots of welding is required in this conversion. You need front spring hangers, the tandem axle kit (equalizer, hanger and shackles) and rear hanger, along with all the U-bolts and tie-plates.
 

DStraitwell

Cadet
Joined
Jun 12, 2010
Messages
6
Re: Changing from single to tandem axle

Silvertip: thanks for the site. I'll definitely look into it. I do realize the welding involved. I am setup for MIG,TIG, high freq, and stick here. It's the despersement of the weight and the act of this new equalizer that I need to understand.
On my boat, most all the weight is in the rear. The weight of an 350 chevy engine, 40 gallon fuel tank, 2 batteries, gearbox, prop, etc. Plus the weight of the cage and the rest of the stainless engine stand and seat riggings I just built. I may just need to visit the airboat shop Monday and take a few measurements and a picture or 2.
I got ahold of McClain Trailers and got a price quote for a tandem trailer rigged the way I wanted. 4K is a little steep after just spending 18K on the boat. thanks for the tips and wish me luck. Don
 

Silvertip

Supreme Mariner
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Sep 22, 2003
Messages
28,758
Re: Changing from single to tandem axle

Location of the axles should not be difficult to determine.

1) Ensure you have the correct tongue weight right now. (7 - 10% of total weight)
2) Mark the exact axle location on the frame as it is right now.
3) That mark is the location of the equalizer pivot point.
4) Front and rear spring hangers get positioned from that point. (Location depends on spring length but the web site shows how to measure that.)
5) When everything is installed the tongue weight should be pretty close if not identical to what you had before.
 

DStraitwell

Cadet
Joined
Jun 12, 2010
Messages
6
Re: Changing from single to tandem axle

Silvertip: I investigated the Champion site and the tech info there. With the info listed and the tips you just gave me, I beleive I can move forward now with confidence. My guess would be for the second axle to be exactly the same as the one I installed last wednesday. Same # spring leafs,axle, parts, etc. Also the exact same tires and rims. the equalizer still throws me off, but after more reading, it should become clear. Thanks again. Don
 

kenmyfam

Supreme Mariner
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Aug 10, 2006
Messages
14,385
Re: Changing from single to tandem axle

Just interested here, may I ask why you want to add another axle ??
 

Silvertip

Supreme Mariner
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Sep 22, 2003
Messages
28,758
Re: Changing from single to tandem axle

Look at the equalizer this way -- if you were to mount both axles just as though they were single axles, there would be tremendous stress placed on one wheel/tire as it passed over an obstacle. Remember, there isn't a lot of flex in a leaf spring system so that tire would be quickly overloaded. An equalizer is a pivoting assembly that has the back end of the front spring and front end of the rear spring attached to it. As the front wheel passes over an obstacle the equalizer pivots to provide the suspension travel required without adding stress to the wheel/tire assembly. Hence the name "equalizer". The opposite happens if the wheel drops into a hole. The longitudinal CG (minus tongue weight) for the trailer is at the pivot point of the equalizer.
 

DStraitwell

Cadet
Joined
Jun 12, 2010
Messages
6
Re: Changing from single to tandem axle

Kennyfam: it's to insure that I don't loose my load completely. I trailer an airboat. I just rebuilt it all stainless rigging and cage/engine stand. I actually lost approx 900lbs doing this, but never thought much about the capacity of the load. I drove way across town in a very busy part (city/freeways/fast pace) for a carb rebuild/ tuning.Well known race track driver, did a super job, got my boat up to 450hsp. Coming home dropped one leaf spring letting the axle go against the fender well. Very scarey and smokie situation. Limped back to his shop and replaced both leafs and axle. All had to be hand cut with a grinder due to damage from saltwater.
Bottom line: I was three blks from getting on the Beltway where you must go from 30mph to 70mph ASAP to blend into the merging traffic. If I had done this and the leaf disintagrated there could have serious loss of life.

Silvertip: thanks for that tip. I am going to due some more reading on the equalizer bar situation tonight if it's posted. Took the boat out today; trailer pulled fine. But the earlier scenerio was on my mind all the while I was driving.
Thanks Don
 

180shabah

Rear Admiral
Joined
Mar 26, 2005
Messages
4,995
Re: Changing from single to tandem axle

Coming home dropped one leaf spring letting the axle go against the fender well.....All had to be hand cut with a grinder due to damage from saltwater.

Total redesign to compensate for a lack of maintenence???
 

DStraitwell

Cadet
Joined
Jun 12, 2010
Messages
6
Re: Changing from single to tandem axle

Shabah: I haven't had a chance to have a maintainence program. Just bought the boat, 350C.i.,prop, and trailer. Pulled the cage, engine stand, seat stands and rigging; cut them up with a torch. All carbon steel in a saltwater environment. Rebuilt everything, except trailer. Now it's time to get it online.
Yes, I agree with the lack of maintainence; the engine was a mess, tie wires/suction line for radiator hose.Duct tape-you name it. One project at a time though and I'll have a nice setup.
Silvertip- after looking at the explaination of the equalizer, I don't beleive the springs I just bought will work. They have the ends which slide up in the brackets in the rear and bolt in the front. Looks like with the equalizer- bolt front/bolt equalizer--bolt equalizer/bolt rear. That would be using the spring clips with bolt holes, not the slip-in type bracket on back of spring.
Maybe I can use those springs on another trailer around here. Thanks don
 

oldjeep

Admiral
Joined
May 17, 2010
Messages
6,455
Re: Changing from single to tandem axle

2 cheaper/easier possibilities
1) buy a used tandem trailer - around here its not uncommon to see them for $500
2) Forget the second axle. Just get some heavier springs, a new axle rated for whatever weight you think you need and tires rated to match.
 

kenmyfam

Supreme Mariner
Joined
Aug 10, 2006
Messages
14,385
Re: Changing from single to tandem axle

Thanks for the explanation. I see you are trying to protect your precious cargo. I do however think it would be easier, cheaper and a lot less time to hunt for a decent twin axle trailer.
Just my 2 cents though.
 

DStraitwell

Cadet
Joined
Jun 12, 2010
Messages
6
Re: Changing from single to tandem axle

Thanks guys for all ur input and tips. going to be out of town for a little bit. Will make a decision when I return. don
 

krakatoa

Senior Chief Petty Officer
Joined
Aug 8, 2008
Messages
705
Re: Changing from single to tandem axle

Yes, very interesting I would like to know How it is finished,:rolleyes:
 
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