New guy needs help!!!!!

[imagomer]

Hey every one I'm new to the rat rod game and am interested in building one. I have pretty much every thing needed to build one but am really a little clueless on building the frame. I'm a welder/fabricator by trade so am not scared on taking on this task. I want to run a straight axle in the front with friction shocks and transverse spring, transverse spring and motorcycle shocks in the back. The thing I am confused on is the radius rods, concerning their mounting and adjustment. Any pictures and info would be a great help. Thankyou

 

[Toad]

If you have a Speedway catalogue they have diagrams in there.

Toad

 

[imagomer]

Thanks for the reply Toad. I looked onthe Speedways web page and found a diagram but it really doesnt give much info. Im wondering if they have to be parallell to the ground, how long they have to be, why they need to be adjustable, etc.

 

[klink]

I'm sure you understand that the radius rods position the front axle. The other thing they do is set the caster angle of the axle. Caster is the "lean" of the kingpins fore/aft, the bottom side will be more forward than the top for positive caster. So sometimes they're adjustable so caster can be tuned. I'm sure the adjustment comes in handy for fine tuning the position as well. Caster angle needs to be determined after you decide on ride height. Once ride height is established, you'll set the caster angle, usually between 5 and 7 degrees. The mounting point for the radius rod may not be on the frame. This is why you sometimes see the mounting point located on a tab attached to the frame. There's a lot of info on this, once you understand caster, I think you'll figure out the rest. More caster = hard steering around corners but produces a setup that goes straight. 7 degrees will be noticeable when cornering, but the car will track nice and straight. I like 5-6 degrees. Make sure your front cross member matches the angle you decide on.

 

[rainman]

I agree with Klink, one other thing the more level you leep the radius rods, (paralel to ground) the less the camber angle will change under compression.
However it's not always easy keeping the rods level if you use factory ones!

One other thing, if you're not planning on running a panhard, ( locating bar) make sure you triangulate your rad. rods!!

 

[imagomer]

Wow, thanks alot guys that really cleared up some things. So if I'm understanding things right the radius rods dont have to be adjustable, just as long as you cut them to length and attach them right in order to obtain your correct angle. Klink, when you say front cross member are you meaning the spring perch? How long do you think I should make them? I was planning on building them out of 1/2" sch.80 pipe with 3/4" tie rod ends welded to them, and building two separate ones (mounted by tabs on the top and bottom of the frame) per side. Another question is, if this is built this way, will the angle not change as soon as the motor is put in because weight is being added to the front?

 

[Sam_Fear]

I'm just learning this stuff, but, yes the angle will change - unless you do a 4bar. You'll want them adjustable because you will not know if it steers right until you drive it.

A few guesses here (about the front):
You want the hairpins perpendicular to the transverse spring (in the vertical plane) or there will be binding. You want the hairpins as long as possible to reduce the change in angle through the arc.

Will a triangulated 4-bar work well with a transverse spring or would it bind?

Here is a great read - PDF of Australia's Guidelines for Building Rods - Suspensions: http://www.infrastructure.gov.au/roads/vehicle_regulation/bulletin/pdf/Street_COP_sec_5.pdf

 

[RAT IHC]

Just a couple of thoughts. With as cheap has you can get adjustable radius rods I wouldn't try to make them yourself. Plus you will want some adjustment. When the spring settles the angles on the suspension will change and if you don't have any adjustment your stuck with possible bad alignment on your front axle. Along with other resources for parts on the web check out what some of our members offer (under the "Businesses, Vendors etc!" link). Second I personally would recommend a panhard bar. The ends on a radius rod have lateral movement. Plus the spring shackles will also have lateral movement. In which case the pin/bolt that holds the spring centered and the u-bolts on the cross member take all of the lateral pressure. The purpose of the spring and spring perch is to absorb bumps and such from the road.

Just my $.02...

-Troy

 

[klink]

Wow, thanks alot guys that really cleared up some things. So if I'm understanding things right the radius rods dont have to be adjustable, just as long as you cut them to length and attach them right in order to obtain your correct angle. Klink, when you say front cross member are you meaning the spring perch? How long do you think I should make them? I was planning on building them out of 1/2" sch.80 pipe with 3/4" tie rod ends welded to them, and building two separate ones (mounted by tabs on the top and bottom of the frame) per side. Another question is, if this is built this way, will the angle not change as soon as the motor is put in because weight is being added to the front?

Don't use pipe for your suspension. DOM tubing would be more appropriate, but as mentioned in another post, radius rods/hairpins etc are pretty inexpensive. Pipe is not designed to carry a load.

Yes, I mean spring perch when I refer to the cross member. In a transverse spring setup the angle of the spring needs to match the caster angle, this will keep the spring from binding. The setup your describing sounds like a 4 bar setup, if that's what you're planning, then if it's setup correctly the caster angle shouldn't change when the suspension cycles.

 

[imagomer]

Thanks a ton everybody!!!! I have a real good idea on what to do now.

 

[Sam_Fear]

When you start getting things laid out and tacked up, post some pictures and get some feed back on 'em. There are a lot of little things that can make a big difference and there's a 1000+ years of experience on this board that'll help make sure you get it right (and safe).

Dig through some of the bigger build threads - someone has probably done close to what you want to do. Start a build thread and throw up some pics of what you're doing. We all like following along and it might help the next guy that's trying to figure it out.