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Discussion Starter #1 (Edited)
here is something i read in another post -

There are two CORR Pro 4 trucks running solid axles front and rear and they get it on!
Jason :)
i need to see pics of those solid FRONT axles - it's very important for my build.

anyone can post a pic or give a link?
 

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Surprises me, too, but Jason would know since he crews on one.

They used to be more sportsman/street-truck based back in the 90's. Now they're all tube-framed.
 

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The solid axle trucks have not been competitive for more than 10 years.

There were some that still raced mostly twin traction beam fords. These trucks were easy to spot, they sat a foot or two taller.

Dale Dondel raced one for one year 4-5 years ago that he bought from I think Mike Leslie but it was several years old already.

You are looking for trucks that were built before Marty Reid started CORR think SODA the Short-Course Off-Road Drivers Association in the early 90's (yes I have been around that long).
 

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Discussion Starter #5
The solid axle trucks have not been competitive for more than 10 years.
why is that?

i keep hearing it, and i only see IFS in desert racing, but never got any real scientific reason and argument explaining it.


You are looking for trucks that were built before Marty Reid started CORR think SODA the Short-Course Off-Road Drivers Association in the early 90's (yes I have been around that long).
thanks for the info.
 

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i keep hearing it, and i only see IFS in desert racing, but never got any real scientific reason and argument explaining it.
Too much unsprung weight and a high propensity for death wobble are just 2 reasons.
 

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CORR is not desert racing, there is no silt or deep ruts so ground clearance is generally kept around the minimum allowed by the rules. The pro 4 trucks are very fast in the tight turns that are common on the short courses. Light weight is very important in being able to change direction quickly. Another factor is the center of gravity.

Think of a F1 car if you could move the center of gravity down 3 inches that would be a huge achievement.

In the last 15 years the center of gravity of a CORR pro 4 has moved down 2 feet or more.

The newest trucks are several hundred pounds lighter than trucks built 6-8 years ago. This was really brought on from the rules on engine size to weight. The Nissan and Toyota engines can not be built to the same large cubic inch sizes that the Ford and Chevy trucks can, so these trucks were built lighter. Rod Millen's Toyota from 6-7 years ago is an excellent example.

If you can save 50-75 pounds or more by running an aluminum center section and CV shafts in an IFS set up over the weight of a solid axle and lower the center of gravity 12 inches by lowering the ride height of the vehicle that is a HUGE advantage.

Other considerations are the steering, adjustability, slip angle of the tires during cornering, and as mentioned by Triaged unsprung weight. Another consideration is that these trucks are very wide and when you are at the point that you have to make a custom width front axle and reinforce it so it is durable it is not much more work to go to an A arm set up with CV shafts.
 

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The solid axle Pro 4's out there are not as competive as the more modern trucks for sure but you can do well in the Pro Classes if you finish. As far as me saying they "get it" well these older style Pro 4's do go well and would easily beat most any current Desert truck or Trophy Truck at the typical CORR style closed course so while they are not as fast as the fastest trucks they are faster then many current desert truck when in their element on a closed course style "groomed" track. Many times 1/2 the field breaks so it would not be hard to get a top 10 finish even with 15 or 20 entries because of high attrition rates at many races.

Jason :)
 

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what about the fact that with a straight axle, a bump at one tire affects the other side where as with independent it doesn't...that would be the biggest reason i could see...
 

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Discussion Starter #10 (Edited)
Another factor is the center of gravity.

Think of a F1 car if you could move the center of gravity down 3 inches that would be a huge achievement. .
i see no problem in building a VERY LOW COG car with a front solid axle. in fact, i've done it myself. the front axle does'nt necessarily sit under the frame, and when it sits infront of the frame, it can be made so the car's COG is as lower as in an IFS car, if not lower.

If you can save 50-75 pounds or more by running an aluminum center section and CV shafts in an IFS set up over the weight of a solid axle and lower the center of gravity 12 inches by lowering the ride height of the vehicle that is a HUGE advantage.
if you go 4x2 then you dispose of the diff and then we're talking two knuckles and one strong chromo connecting tube, which would be lighter then any IFS setup.....

Other considerations are the steering, adjustability, slip angle of the tires during cornering.
steering is no problem, since the steering devise can be mounted on the axle and not on the frame. this would completely solve any frame related bumpsteer, and other steering phenomena. besides, once you solved those steering issues, there's really no major factor to make you vote for IFS. otherwise, TTs would'nt run solid rear axles, and would run IRS, is'nt that so????[/QUOTE]

Another consideration is that these trucks are very wide and when you are at the point that you have to make a custom width front axle and reinforce it so it is durable it is not much more work to go to an A arm set up with CV shafts.
no. it would be much easier to build a strong front solid axle than to build a strong IFS, with the same unsprung weight.

i'm stil not convinced. sorry.
 

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Frog I am not trying to convince you of anything.

CORR trucks are a very specialized vehicle. There are many things involved in building one of these trucks including a rule book and truck manufacturer involvement. Ford, General Motors, Toyota, and now Nissan all make 1/2 ton trucks that are 4 wheel drive with IFS. The rules are not exactly clear in this section but it is generally understood that the design should be generally the same as a production vehicle. If you wanted to build a new 1987 Chevy 4x4 I think you may be able to but would have a hard time getting any help from GM and there is the risk that CORR could change the rules to limit design to current model years.

Let me try this ....... most Pro 4 trucks are set up with a massive amount of camber, the tires almost look like this / \. Explain to me how to build a solid front axle that the people who sponsor you do not want you to use, with a camber adjustment range of 15 degrees or more. Now how can I independently adjust the caster or camber from one side to the other at the race track? Antidive ?

A few years ago some of the racers (Adrian, Carl ?) tried to run cambered rear solid axles (small amount of camber) and had continuous problems with breakage.

CORR is a contact sport. With IFS if we get hit on or hit something with a front wheel usually all that is necessary is to replace a broken CV and adjust the upper A arm to accommodate for slightly bent parts. When you are trying to prep the truck for Sunday after a crash Saturday, it is 3 AM and you have been up and working at the race track for 20 hours already, it is a lot easier to do this than to assemble a solid axle and install it.

4x2 .... the CORR pro 2 two wheel drive trucks are a standardized chassis design to keep costs down. The main frame rails and the front suspension attachment points (A-arm) are all built to CORR rules.

I do not understand exactly where we are going with this. Unless you are building something specifically to race in CORR you may be better off looking at some of the desert race trucks.

Do you have a specific problem or question with your build?

I looked at your posts with the Frog 2 are you working on that or something new?

Have you seen this thread? http://www.pirate4x4.com/forum/showthread.php?t=596316
 

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Discussion Starter #13 (Edited)
Do you have a specific problem or question with your build?

I looked at your posts with the Frog 2 are you working on that or something new?
first of all, let me thank you for your elaborated posts - i really appreciate it.

the Frog 2 is almost a part of history - it is a fantastic vehicle with some unique ideas, but whoever knows me, knows i keep going on, so the frog 2, although quite young, is about to be dismantled. i learned and proved all had to learn and prove with it....:)

what i am about to finish is a rig i call the "grasshopper", which you can see here - http://www.pirate4x4.com/forum/showthread.php?t=569157&page=8

what i'm starting now is not a CORR car, because we do'nt have this kind of racing in Israel.

what we do have is desert racing, similar to what you have in the Baja races.

it's going to be a 4x2 rear solid axle car, with 37" wheels and a 400hp engine, built TH-400 manual only tranny, 4 bilstein 18" coilovers and 4 18" four bypass shocks, etc.

i never could really figure out the advantages of the IFS over a solid axle, although i can see everybody runs it.

on the contrary - i see a lot for a solid axle in the front, but before i do anything i'll regret later, i want to make sure that my design can overcome any of the faults or disadvantages of the tradditional front solid axle design, such as my solution for moving the steering system to the axle instead of to the frame.

for example, let me say that i do not buy the argument which says that when a wheel goes over a bump it affects the second one - effecs yes, affects - no, on the contrary.

so, if you can help me out here, i'll be for ever in your debt...:smokin:

Barry
 

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Barry correct me if I am wrong.

You are building something new that is not the grass hopper.

The new vehicle will have-
four wheels
rear wheel drive (solid axle)
long travel possibly radius arm front and four link rear suspension

you want a front that is not driven and not IFS
you want steering that will provide feel and not bumpsteer

If you read that and thought YES, I understand what you are after.

Unfortunately I have not been able to find a picture of the steering only the whole vehicle.

http://www.race-dezert.com/forum/attachment.php?attachmentid=1525&d=1046188290

The link is a picture of the Skiltons Cherokee.

This Cherokee won the Baja 2000 in class 8 with Curt LeDuc driving.

You are looking for the "LeDuc bellcrank Cherokee Steering setup" simple in the way it works but hard to describe clearly.

From looking at your other projects you should be able to build this using a ChroMo tube with Dana 44 knuckles.

Can any one else help with the pictures? Jeepspeed guys? I had a computer meltdown last year and lost 2-3 years of pictures, all the places I have been, and stuff that I have done.
 

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One big problem with a solid front axle in a desert racing application is what I call lack of "Recoil", but I dont know what other terms are used to describe it.

When a solid axle front end with long link suspension droops out, it moves back, when it hits the next bump, it moves foreward and tries to move up at the same time. This is not a good thing. You dont notice it when you have 15" of wheel travel, but with 24" of travel, no matter how long your front trailing arms are, you still dont have recoil, you actually have the opposite, or antirecoil. That is my new word that I just made up:D

The same reason a reversed shackle in a Jeep rides better, the axle moves backwards absorbing the bump, not pushing back into the bump and fighting upwards movement.

Many a arm setups dont have recoil, and still ride well, but they also dont push the tire into the obstacle or "antirecoil"

Look at the late great Nye Frank A arm suspension designs on the "Mighty Mouse" trophy truck or the 4 wheel drive truck he built for the Dondel's. The front lower a arms are angled to give a ton of recoil.

Another advantage in the desert with an a arm is the clearance you get with a front a arm setup. You get a ton more initial clearance. The a arms and the front skid offer a dirt ramp to let you slide over things if you bottom the chassis out, it acts like a big sled in the dirt.

In ruts you drag a rear solid axle over things, if you hit something big it just compresses the suspension or drags the axle over the rock or rut. On a front solid axle, you hit a rock or rut and it either wants to push the suspension down due to the angle of the front control arms, or it wants to stop the whole vehicle from moving foreward and at the same time crush the hydraulic steering components that are mounted onto the front of it. Then you are forced to run rear mounted hydraulic steering.....

I am a big fan of solid axle pre runners, but they do have thier limits, and probably 15" of wheel travel is one approximate limit.
 

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Discussion Starter #18
Barry correct me if I am wrong.

You are building something new that is not the grass hopper.

The new vehicle will have-
four wheels
rear wheel drive (solid axle)
long travel possibly radius arm front and four link rear suspension

you want a front that is not driven and not IFS
you want steering that will provide feel and not bumpsteer

If you read that and thought YES, I understand what you are after.
i was thinking YES, with a little corerection - the solid axle(empty with no diff) will be located INFRONT and not UNDER the frame.

look at the pics
 

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Discussion Starter #19
One big problem with a solid front axle in a desert racing application is what I call lack of "Recoil", but I dont know what other terms are used to describe it.

When a solid axle front end with long link suspension droops out, it moves back, when it hits the next bump, it moves foreward and tries to move up at the same time. This is not a good thing.

this is one of the most important issues in my design - since the "recoil" happens only if the front links are pointing downwards, my front links will be pointing(in ride height) UPWARDS, so the wheels move backwards, while hitting a bump.

it is true that if the links are too short or the upwards angle is'nt enough, then in full droop a certain amount of "recoil" might occur.

i think my design overcomes this obstacle, even with a reasonable amount of droop and a long travel front suspension.

BTW, this is exactly why the rear links should be pointing DOWNWARDS and not upwards - the wheels must follow, as much as possible, the face of the terrain.

thank you all for your input - i really need it :beer:
 

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How much uptavel do you plan on having? how much droop?

If your links are pointed upwards at ride height, when they move up to the top of the travel what happens to the frame end where they're mounted? Is it going to dig into a whoop or bump?

If you have any droop, the links are going to have to go below horizontal which means they'll still be dealing with the "recoil".

I like the ideas and thinking differently, but I am having a hard time seeing a rig with a lot of go fast potential over rough ground, built like what you're saying.

I still see it limiting the speed the rig can go. Hell Drew's rig flies over stuff, but it will onyl go "so" fast. but that might be fast enough.
 
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