Determining Axle Length?

[Uncle Chan]

So, if I wanted to build a basic 4 x 8 TD, and wanted to use a torsion axle, how would I determine axle length?

[Uncle Chan]

I figured it out. If I use a torsion axle, I will want the width of the axle to be the same as the outside frame width. So, a 48 inch wide frame would need a 48 inch torsion axle.

[madjack]

...Chan, I am afraid it is not so simple...there is some excellent info located in the stickies in this section of the forum...you will need 3 different measurments to accurately order an axle...outside2outside frame, which will determine where the MOUNTING PADS sit...outside2outside hub measurments, which will be determined according to what wheels you use...this is probably your MOST important measurment and if you want the body to come down over the frame, you will need to determine inside2inside measurments for the torsion arms...not taking these things into consideration may well cause you to end up with something you don't want and possibly can't use...........
madjack

[Uncle Chan]

Oh sure, just burst my bubble!

Back to research.

[jjlentz]

Hey Madjack,

What's a good rule of thumb on tire clearance when mounting the body over the frame? My outside dim. will be 60'' Is the clearance amount added to OD for the "inside 2 inside" torsion measurement? Thanks for your help earlier 2day in response to the pm I sent. My wife says I need 2get off the computer and out in my shop!!!

Jeff. Salisbury NC

[madjack]

...between the body and the torsion arms, a 1/4" is adequate since the torsion arms have no side to side deflection...between the body and the tires, an inch or so is adequate...if you can stick your hand, to the "palm" knuckle, you should be OK...a bit more should be added for spring hung axles...not taking this into account on my first build resulted in about a sheet of paper clearance...they never rubbed but it sure made me nervous...on Camp-Inns, they actually relieve the plywood itself to provide clearance....................
madjack

[eamarquardt]

I like to see the tire centered in the width of the fender. If the clearance seems too tight, then maybe you're using too wide of a tire/rim. You need to have your tires and rims before you order the axle as different rims have different offsets (where the mounting surface (rim to hub) is in relation to the center of the tire.

Step one: obtain rims and tires
Step two: determine center distance for spring/torsion mounts
Step three: determine outside hub to outside hub distance to make sure the tires end up in the center of the fender (or where ever YOU want them to be).

I had a change of plans and lengthed the axles for my dump trailer so on leaf spring axles it can be done. Not sure what it would take to adjust torsion axles or if it can be done after their fabricated.

Cheers,

Gus

[aggie79]

...you will need 3 different measurments to accurately order an axle...outside2outside frame...outside2outside hub measurments..this is probably your MOST important measurment and if you want the body to come down over the frame, you will need to determine inside2inside measurments for the torsion arms...not taking these things into consideration may well cause you to end up with something you don't want and possibly can't use...........
madjack

Madjack is right. I wish I had seen this post before ordering my axle. I got the first two right, but didn't think about the last. The torsion arms would have been almost flush with my outside wall, so I am having to notch it like Asianflava.

Tom

[kennyrayandersen]

there are a few topics that bare repeating -- this is one of them! That axle stretcher is hard to come by!

[madjack]

there are a few topics that bare repeating -- this is one of them! That axle stretcher is hard to come by!

...naw Kenny, a BigJohnsonStrecher is available from...oh wait...that's a different subject
madjack

[asianflava]

Madjack is right. I wish I had seen this post before ordering my axle. I got the first two right, but didn't think about the last. The torsion arms would have been almost flush with my outside wall, so I am having to notch it like Asianflava.

Tom

I don't get to post (or camp) much anymore but my ears must have been burning to make me click on this post.

Here is what I learned from doing mine:
Yes I had to notch my body, it wasn't that big of a deal.
I had 2in clearance between the tire and sidewall, too much IMHO (1/2in would be fine).
Have your wheels with the tires mounted so that you can find your exact offset.
See if a "short spindle" is available and order it if possible.


Step 1 Get your tires mounted to the wheels you want to use
Step2 Lay the wheel on the ground and measure the distance from the floor to the hub face.
Step3 Tire Offset X2 + sidewall to tire clearance X2 + body width = hub to hub distance.

Somebody please correct me if I forgot something, It's been awhile since I had to figure this one out.

[aggie79]

Madjack is right. I wish I had seen this post before ordering my axle. I got the first two right, but didn't think about the last. The torsion arms would have been almost flush with my outside wall, so I am having to notch it like Asianflava.

Tom

I don't get to post (or camp) much anymore but my ears must have been burning to make me click on this post.

I hope you didn't interpret my post as being negative. I was trying to be complementary to you for already thinking through a situation and providing me a solution.

I agree that if there is a short spindle option, get it. There was an option for this on the Dexter #9 axle but I wasn't aware of it. If had known, this would have allowed me to keep the same mount to mount and hub to hub dimensions, but it would have pulled the torsion arm further away from the side wall.

Not to complicate things further, but on the Dexter axles, you need to think about the start angle. I went with the 10 degree up because I wanted a lower teardrop and I plan to use tall wheels/tires. I haven't polled the forum, but I believe most are using the 10 degree down.

Tom

[madjack]

...the short spindle on the Dexter is what allowed me to have that 1/4" clearance on the torsion arms...otherwise, they would have been flush with the side walls...it also allwed me to keep my 205-70-15 tires under a 10.5"W fender...I used a 0* start angle, along with the 26" tall tires and a 2" axle tube, I ended up with 12"s of ground clearance under the axle...
madjack

[asianflava]

I hope you didn't interpret my post as being negative. I was trying to be complementary to you for already thinking through a situation and providing me a solution.

I agree that if there is a short spindle option, get it. There was an option for this on the Dexter #9 axle but I wasn't aware of it. If had known, this would have allowed me to keep the same mount to mount and hub to hub dimensions, but it would have pulled the torsion arm further away from the side wall.

Not to complicate things further, but on the Dexter axles, you need to think about the start angle. I went with the 10 degree up because I wanted a lower teardrop and I plan to use tall wheels/tires. I haven't polled the forum, but I believe most are using the 10 degree down.

Tom

Oh no, it was just a funny coincidence that I just happened to click on this post.

I too, did not know about the short spindle option until I had my axle in hand. I was looking at it thinking, "If this spindle wasn't so long, I wouldn't have to notch my sidewall." Then I saw some paperwork that came with my axle that indicated that a short spindle was an option.

I had no clue for the start angle, I just knew that 45deg would be too tall and 0deg would be too short. I just split the difference and ordered it with a 22.5deg start angle. With my wheels and tires, it works out just right. Not too short where it drags on steep driveways and not too tall to make it difficult to enter/exit.

[Uncle Chan]

I'd be remiss if I didn't tell you that all of this is confusing the heck out of me!!!!

Ain't learning fun?