Race Trailer Question

[Randy V]

A third axle will do what you need it to and I think that when towing on the highways, with such a competent tow vehicle you will not notice any issues in turning. You will drag tyres around corners but for the amount you use the trailer and tyre wear, that should be an acceptable price to pay. So long as you don't leave tyre marks on the driveway at home.....

Every triple axle trailer I've ever been associated with (3 of them now) was a tire shreader... Each had a number of cases where the tires would have ply separations and/or blow-outs. Each was running trailer specific tires and well within the load rating. One trailer was a Tag and the others were Goose.

I think for your application Ron, The best bet would be the relocation of the rear axle to a location forward of the front axle. It might require the relocation of both axles.

Also - Keep a close eye on your hitch. I've seen two Class V Hitches now (Reese) start to fail and one on a friend's 3/4 ton Suburban failed altogether with my trailer on the back.
Poor welds. But not all of them are so - so you need to inspect carefully and replace or beef up the hitch..

The hitch that failed could have killed my pal and his two friends in the Sub. As it was it totalled out the truck, trailer and Corvette inside.

 

[zollis]

Hi Ron ,

Us humans can't beat the laws of physics . Total weight on the hitch is the sum of all the moment arms . Each weight multiplied by it's distance from the fulcrum , which is the trailers front axle .

Perhaps not practical but will reduce the weight on the hitch is to replace those aluminum up-ramps with 3/4 inch thick steel ones .

Otherwise you can always try to overcome the laws of physics by bolting on , on to the top of the white box , a device called a " Z- spin- negative- gravity-anti-cyclone" .
I just don't know who sells them .

Z.C.

 

[David Morton]

Ron - I have a fairly large twin axle trailer and the weight on the nose pin is never ideal which also results in poor directional stability - especially when being over taken by large trucks. I fitted the Bulldog double anti sway bars and tightened up the clutch mechanism to 120ft/ lbs and that went a long way to addressing the problem. I still feel trucks coming by but the whole rig just has slight sensation - more like a slight lean instead of swaying like a snake (which was very alarming at times) - as the trucks come past. Incidentally I normally tow this with a Mercedes Sprinter 3.5 ton van and the whole shooting match is 6 tons, but when I hitch up my Ford Explorer, the air suspension levelling system keeps the Ford in the same vertical position irrespective of the weight on the trailer nose so the stance of the truck is not always an indication as was suggested in a previous post so the position of the truck/Explorer in this case has no bearing on the weight on the towbar on the Explorer.
I also use the Bulldog system on that car as well. It works really well for me and I just set the cruise at 55mph, put on some Cream or Hendrix, pour a coffee, and a thousand miles
goes by in two days driving split into four two hour sessions each day, all preferably at night.

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[Mark Maybury]

Ron,
It looks like you will be relocating the 2 axles forward to lesson the weight on the hitch. Just be careful that you do not move them forwards too far as that will make the trailer sway.
Mark

 

[Wally]

Ron I Have to agree with Randy on the tri axle trailers there to be avoided if at all possible. Unless the axle are well supported they wander all over the road along with eating tires. We made a subframe that mimicked what was there ( note the fenders are with the subframe ) then slid the trailer back till the tongue weight was where we wanted and bolted it in place. ( eight bolts and we can change this at any time to compensate for different configurations ) I think we did end up 3/8 to a 1/2 in. higher the thickness of the angle iron used. Is this a C channel frame or Boxtube ???? Ours was C channel made bolting this easy.

 

[John]

Ron, mate from my experience , and for what its worth i have built more trailers than i care to remember, you towball hitch weight should be around the 50-80kg max with the trailer loaded, and the centre of the two axles should be a couple of inches behind centerline of trailer frame, the latter will assist trailering, ie stop the swaying etc, some times it comes down to reconfiguring how you load it. you may have a situation where you are just carrying to much weight in the front box, and it may be adventageous to transfer some of that load into the tow vehicle.
trailers are a wonderfull thing but they unfortunatly do have limitations, and can be killers if not set up right, and god forbid we dont want that to happen.
as for a 3rd axle as suggested, avoid it like the plague
cheers John

 

[Trevor Booth]

"Total weight on the hitch is the sum of all the moment arms . Each weight multiplied by it's distance from the fulcrum , which is the trailers front axle"

I hope not !!

The suspension should be load sharing then the fulcrum is the centre of the set of wheels.

 

[zollis]

Yes Trevor it will be ideal if the 2 axles are load sharing and the fulcrum is in the centre of the set of wheels . But in this case here the load on the hitch is measured in a static condition as 1600 / 1700 lbs . Kaspa ( John ) is in the ball park with 50/ 80 kg ( 100/160 lbs ). In this case it seems as the front axle is doing all the work while the rear axle is there just for a joy ride .

Z.C.

 

[Trevor Booth]

"In this case it seems as the front axle is doing all the work while the rear axle is there just for a joy ride ."

On what basis do you make that assumption ?

 

[Russ Noble]

Hell, I might just have my welding trailer man reinforce the hitch receiver and the trailer tongue and call it a day. Thus far the thing works great.

Well, since you say it tows well and if you're not getting front wheel lockup under heavy braking, and your only concern is the possibility of a failure in the hitch then the easiest solution is, as you say, beef up the coupling and drawbar and vehicle attachment points. That way you won't risk upsetting a combo that you say works well.

 

[zollis]

To answer post # 29

Trevor as you know there are different methods of mounting the axles;

1) If the two axles are mounted in a bogey fashion with a central pivot between the two axles, then the load on each axle is the same.
2) On the other hand, if the axles are mounted directly to the frame, each with its own mounts and shackles, then the load on each axle can be different.

I took a guess at the second method because post # 1 states "move the two axles forward". I assumed each by itself.

Ron, by which method are the axles mounted, #1 or #2?

As an aside, have you already called it a day, as you suggested in post #10?

Z.C.

 

[Trevor Booth]

Zollis
obviously you have some enginnering background, Assumption has no place -

 

[Ron Earp]

Ron, by which method are the axles mounted, #1 or #2?

As an aside, have you already called it a day, as you suggested in post #10?

Z.C.

Method #1, they are mounted together on leaf springs with some sort of cantilever in there and both share the trailer load. No doubt they are both loaded.

I haven't called it a day. What I have called it is trailer science "voodoo". I posted the same thread over on another race board I'm a member of and the total number of replies between the two boards is probably over 50 or so, expressing every opinion on the various facets of this topic that you can imagine.

To summarize on a couple of points:

1. The three axle camp is strongly divided into "I hate them they eat tires" to "I have one and it is awesome, but yes, it is a bit more difficult to turn sharply". I'd like to try and avoid it simply due to cost.

2. Tongue weight - again, camp at two ends of the spectrum. "You should only have a couple of hundred pounds" to "the more it has the better it tows". I strongly believe that a couple hundred pounds is too light, based on my experiences, and somewhere in the neighborhood of 700-900 lbs of tongue weight is where I want to be.

I'm going to have the receiver and hitch beefed up so that a failure there won't be a problem. Then, I'm going to relocate as much weight to the rear as I can (or do the calculations) and see what I have. If that doesn't solve the problem then we're going to move both axles forward a bit. The problem the moving them is it is time consuming and we're in the middle of race season.

 

[David Morton]

If you dont have a tow vehicle connected and your trailer fully loaded, will the
tow connecter.socket /part on the trailer fall to the ground or sit at a particular height? If it doesn't fall to the ground (twin axle) then the height of the ball on your car decides the nose weight. If it were neutral (same heights) then you have no nose weight. There after it's a simple matter of lever moments.

 

[Ron Earp]

From initial description:

I've a question for those knowledgeable about trailers. My race trailer has too much tongue weight. Way too much. We measured it on the scales yesterday at about 1600-1700 lbs of tongue weight.

Oh yeah, it falls to the ground with a mighty thud.

 

[David Morton]

I use about 120 kg (264 lb) unloaded and about 160kg (352lb) loaded but on its own it sits on the four wheels and doesn't "fall to the ground with a mighty thud". Both the tow bars on the Sprinter and the Explorer were modified to give me the same height and consequently similar towing characteristics. The three trailers are all the same height but each with different all up weights but similar nose weights loaded and not loaded.

 

[Russ Noble]

Method #1, they are mounted together on leaf springs with some sort of cantilever in there and both share the trailer load. No doubt they are both loaded.

I'm going to have the receiver and hitch beefed up so that a failure there won't be a problem. Then, I'm going to relocate as much weight to the rear as I can (or do the calculations) and see what I have. If that doesn't solve the problem then we're going to move both axles forward a bit. The problem the moving them is it is time consuming and we're in the middle of race season.

Provided your hubs and stubs and wheels are sufficiently robust, get rid of the cantilever so the front axle takes more of the weight. This will reduce the tongue weight and is quite a bit less work than moving all the spring mounts and mudguards forward.

It will also have the benefit of reducing side loadings on all the bearings and wheels when doing sharp manoeuvering.

 

[Wally]

HI Ron Is this what you have ??? With the fender clearance you have you could sneak the front axle forward by stretching the walking beam as you only need a couple hundred # shift and with the brackets in hand could be accomplished in an evening. As 2-3 inches may make enough difference to get you where you want.

 

[Russ Noble]

I haven't got time to do the maths right now but I think 2 -3 inches will make a relatively insignificant change to the tongue weight..

 

[Ron Earp]

HI Ron Is this what you have ??? With the fender clearance you have you could sneak the front axle forward by stretching the walking beam as you only need a couple hundred # shift and with the brackets in hand could be accomplished in an evening. As 2-3 inches may make enough difference to get you where you want.

That is the very thing. I would bet that 4 to 10 inches would make a fairly decent change. The complicated matter is that the trailer has the large under deck steel boxes that I designed into it when built. And, one of the boxes is right where the axles would shift too. So, there will be some cutting and re-welding of boxes as well, a hell of a lot of work. But, I think it is going to have to get done.