trailer axel location

motox · Sun Jul 05, 2015 7:11 am

with all the trailer builds here though this might
helpful to someone.
craig

ShaunBlake · Wed Jul 15, 2015 5:53 pm

Thanks! (Don't expect to ever need it, but I keep thinking of dumping my utility trailer and building my own.)

Wed Jul 15, 2015 6:45 pm

I learned CG calculations while studying aircraft design, and this information is spot on.

I hope many would-be trailer builders pay attention to this.

It's also useful if you buy a home-built trailer. Step one is to verify CG, and step two is to check tracking against the hitch.

Steve S

ShaunBlake · Wed Jul 15, 2015 11:43 pm

Otto Nobedder wrote:... and step two is to check tracking against the hitch.

Hunh? How would you do that? Tow it in a straight line then stop and measure from the center of the hitch to the outermost point on the axle you can reach; each side must be nearly exactly the same dimension?

Or do you mean some other tracking?

Boomer63 · Thu Jul 16, 2015 8:23 am

ShaunBlake wrote:
Otto Nobedder wrote:... and step two is to check tracking against the hitch.
Hunh? How would you do that? Tow it in a straight line then stop and measure from the center of the hitch to the outermost point on the axle you can reach; each side must be nearly exactly the same dimension?

Or do you mean some other tracking?

The way I have done it is to find center of hitch; mark it and drop a plum line. Measure from a set point on the axle on both sides. I did use the 'U' bolts. That is how I was able to center out the hitch. Maybe not the most efficient method, but it worked just fine for me.
Gary

ShaunBlake · Thu Jul 16, 2015 9:52 am

Boomer63 wrote:...
The way I have done it is to find center of hitch; mark it and drop a plum line. Measure from a set point on the axle on both sides. I did use the 'U' bolts. That is how I was able to center out the hitch. Maybe not the most efficient method, but it worked just fine for me.
Gary

Ah, got it. It seemed to be what Steve (Oo No) was recommending, but I haven't seen it referred to as tracking, and wondered if there might be some other meaning.

On a side note, what is the consequence of having the axle twisted out of square to the travel? It doesn't seem that the tire wear would be excessive unless the angle was so great that the trailer trailed with a considerable shift to the side. And it seems that if it trailed an inch or two to either side, it wouldn't he hazardous, even loaded. Wouldn't it have to trail half a foot or more to the side to cause problems braking?

PS: Are you sure that SteveS didn't mean tracking me with spy satellites?

Boomer63 · Thu Jul 16, 2015 10:45 am

I have a theory that all trailers are slightly 'out of alinement' ... but no one seems to care because there doesn't seem to be any consequences. On the other hand, I might be completely wrong and full of shit. My rule of thumb on projects like this is that if it seems to be tracking straight, it probably is. If the tires aren't wearing, they aren't. If it looks straight, it probably is. Or something like that.

Thu Jul 16, 2015 7:49 pm

I work with trailers that weigh 26 tons empty.

I align the axles to the fifth-wheel hitch with a tolerance of 1/16 of an inch.

Tire wear is one concern. Fuel efficiency is another.

If your tractor (or truck) has to side-pull your trailer, even a little, it costs you both fuel and tire wear.

Steve S

ShaunBlake · Fri Jul 17, 2015 2:42 pm

Otto Nobedder wrote:I work with trailers that weigh 26 tons empty.

I align the axles to the fifth-wheel hitch with a tolerance of 1/16 of an inch.

Tire wear is one concern. Fuel efficiency is another.

If your tractor (or truck) has to side-pull your trailer, even a little, it costs you both fuel and tire wear.

Steve S

So you prolly know what I've puzzled over: in a previous lifetime, I worked at a large scrap metal company. The welders would occasionally need to build "new" trailers, and one of them mentioned to me that the hind-most of the tandem axles had to be offset 6" from the leading axle or it wouldn't track properly. Can you explain the dynamics? It seems counter-intuitive to me.

Fri Jul 17, 2015 6:31 pm

ShaunBlake wrote: ...one of them mentioned to me that the hind-most of the tandem axles had to be offset 6" from the leading axle or it wouldn't track properly. Can you explain the dynamics? It seems counter-intuitive to me.

The dynamic here is that the man in question was a complete idiot.

When I install a new air-ride, each pair of suspension towers is equidistant from the pull-point (king pin of the hitch) within 1/16" inch, and both front and rear towers are square within 1/16" before the first tack weld happens. This is done on a level surface with plumb-bobs. Additionally, the distance between front and rear tower sets is 49" within 1/32".

The result is, when I do the wheel alignment, the aligning cams are never moved more than 5* from the 12:00 position.

It really doesn't add much labor time to do it right, and saves the clients a fortune in tire wear, fuel, and general maintenance. Our primary client is impressed enough with my method and it's results that we now measure suspensions installed elsewhere, and will cut them out and replace if they're not within tolerance.

Steve S

ShaunBlake · Sat Jul 18, 2015 12:20 am

Otto Nobedder wrote:
ShaunBlake wrote: ... tandem axles had to be offset...
The dynamic here is that the man in question was a complete idiot.

Well, he wasn't alone, and I don't like having such thoughts about them. However, it has really bothered me all these years because it was so contrary to my scant knowledge of physics. I am very grateful for your clarification!

Boomer63 · Sat Jul 18, 2015 8:31 am

Steve, you are working with trailers that are way, way bigger than I have built. I have put together some custom jobs for hauling skid-steers, etc. Nothing like the big boys you are talking about.

rick9345 · Sat Jul 18, 2015 10:43 am

Every thing Steve says about alignment applies, big or small. Simple tools ,plumb bobs and string works as well as lasers etc.
Practical application of what is at hand is all that is needed. KISS.

nathan · Mon Sep 07, 2015 11:49 pm

I need to remember this post. I want a truck just so I have an excuse to build a trailer. This will help

Bill Beauregard · Tue Sep 08, 2015 9:23 pm

Otto Nobedder wrote:
ShaunBlake wrote: ...one of them mentioned to me that the hind-most of the tandem axles had to be offset 6" from the leading axle or it wouldn't track properly. Can you explain the dynamics? It seems counter-intuitive to me.
The dynamic here is that the man in question was a complete idiot.

When I install a new air-ride, each pair of suspension towers is equidistant from the pull-point (king pin of the hitch) within 1/16" inch, and both front and rear towers are square within 1/16" before the first tack weld happens. This is done on a level surface with plumb-bobs. Additionally, the distance between front and rear tower sets is 49" within 1/32".

The result is, when I do the wheel alignment, the aligning cams are never moved more than 5* from the 12:00 position.

It really doesn't add much labor time to do it right, and saves the clients a fortune in tire wear, fuel, and general maintenance. Our primary client is impressed enough with my method and it's results that we now measure suspensions installed elsewhere, and will cut them out and replace if they're not within tolerance.

Steve S

I have a feeling if you took a Dale Carnegie course you failed. I got a good laugh at that.

Wed Sep 09, 2015 6:33 pm

Bill Beauregard wrote: I have a feeling if you took a Dale Carnegie course you failed. I got a good laugh at that.

I've read his book, "How to win friends and influence people".

Excellent read. I use it often, but selectively. Sometimes, you have more influence by being very direct, and skipping the dance around the facts.

Steve S

ldbtx · Wed Sep 09, 2015 10:49 pm

Otto Nobedder wrote:
Bill Beauregard wrote: I have a feeling if you took a Dale Carnegie course you failed. I got a good laugh at that.
I've read his book, "How to win friends and influence people".

Excellent read. I use it often, but selectively. Sometimes, you have more influence by being very direct, and skipping the dance around the facts.

Steve S

The one I read was "How to lose friends and alienate people"