Rat Rod problems!! (chassis question)

Hey, I'm interested in my safety too!...but I'm still not really understanding you.

When a little weight is applied to that spring BOTH shackles point downward and the spring is free to "Grow" outward towards both hairpin brackets...which it does. There is plenty of room for it to spread out.

Are you saying that the shackles should already be at a 45* angle without weight applied to it?

Are you saying that I have the spring itself set up at a bad angle to the axle? If so, the entire system is adjustable. I've not really "set" anything up yet in the pic...

I'm not trying to snotty here, I don't have a lot of experience and if somebody with more experience is seeing something I'm not...then I'm genuinely worried.

Could you draw me a picture of how it should look? Seriously. I'm not being a smart *** here...

Tingler

 

This won't work WELL. there will be a "dead space" on initial movement while you take up the "slack" of the shackles. I have attached a picture of a modified shackle mounting location and orientation that will have much better road manners.

http://img6.imagevenue.com/img.php?loc=loc67&image=117_front_end_redo.JPG

http://img6.imagevenue.com/img.php?loc=loc67&image=117_front_end_redo.JPG

Click here for picture

 

Tingler,
Here is a redo of front shackle link location.

 

Me too.

 

Whew, you guys don't get it either....I thought I was going nuts for a second there.

I seriously appreciate ANY and ALL suggestions, and I'm still NOT trying to be a smart ***....but I'm still confused at what alittle1 is trying to say.

 

I do not have a picture for you , but I think I can explain so it makes sense. The shackles, when under load would preferably point slightly downward. This prevents bind when the force pushes aganst them when the spring compresses. It has been suggested that if they are perfectly horizontal under load and the spring compresses they will bind and pop. Since the chances of the force being exactly equal and oposite is so unlikely it will most likeley never pose a problem. Now, the ultimate position of the shackles is yet to be determined because the suspension is not under load yet, so they may be in the right position under load, and this may be a mute point.You mentioned that you purchased the front end from speedway. Their catalog has a diagram in it that will explain this same thing with illustrations. Posie also has a diagram of this in their literature.

 

BUT THEY AREN'T under LOAD!
The spring was obviously spread to even hook up the shackes and it's pulling them (almost) horizontal BECAUSE THERE AIN'T NO LOAD ON THEM!

 

Here's what your spring shackles should look like loaded. If you have a Speedway kit, the springs should be set for a T. If you get the ch***is done, motor in, and the spring shackles don't look like this, then you will have to either add leafs, or change the spring. I would trust Speedway, and not worry about it now.



Mutt

 

Hotrob,
I tried to explain this earlier. I can get up on the spring and just under my weight (200lbs) the spring settles in and the shackles point DOWNWARD like they are supposed to. If I put more weight on it, the shackles would only go further in the RIGHT direction (downward toward the middle at about 45degrees).....

I could understand all this if the shackles looked like they do WITH the weight of the car on it....but it doesn't.

I think it will work fine.

Here's an illustration....

 

Tingler: you've got it right.Please continue.
Post pics when your done.

 

Hey. I'm just trying to help out here. I said all along that the geometry should change when placed "under a load. Simple. just answering a question. I am not suggesting that it is unsafe or wrong in any way. so relax and read the post completely before you get yourself excited.

 

I planning on doin the reverse tie tod if possible as well. What do you have to do to the steering arms to get it to track right? I heard movin em out as far as possible is what you do.

-Dave

 

Tingler, Your on the right road and everything will be fine. Your explanation of how the system works when subjected to a load is exactly how it should operate. I'm not sure how your critic thinks he has a better idea, but I'd leave it for him to try on his own ch***is. Just don't be on the same road when he makes his maiden voyage. Carry on and be sure to keep us posted about the future progress.


Frank

 

I found this paper on suspension geometry and more several years ago. I don't see how reversed spindles would let you steer correctly. The only way would be to bend the arms severely outward and that would hit the tires. Am I wrong in interpreting his Ackerman drawing that way?
http://www.rqriley.com/suspensn.htm

 

Nobody seems to have mentioned yet that the car hangs from the axle, via the shackles
The only reason the shackles are there is to allow that leaf spring to widen as it flexes under load. That is all they are there for. What you have is the perfect set up. That is the accepted way to mount shackles: horizontal before load is put on. As soon as you load them up, the weight, and the spring growing wider, will pull them shackles down a few degrees, maybe up to 45 degrees or so, plus it will hold the axle central, saving the need for a Panhard rod. If you had them real slack, say 45 degrees unloaded, the axle could sway sideways on corners.

 

Gregga,
I've been thinking about this a bit since it was suggested on here to put my tie rod in front of the axle.....
I think it will work fine in front of the axle (bye bye ackerman), it just comes down to ****py LOW speed manueverability.....If I'm reading it right, the Ackerman steering allows for better low speed manuevers like parking lot type stuff...(maybe I'm wrong)

Here's a quote from that article you linked to:

That seems to sum it up for me. In a straight line and on the highway, Ackerman, don't mean squat. (someone correct me if I'm wrong, please).However,flip your spindles and run your tie rod out front, and you LOSE a bit of parking lot parking ability.


THANKS fellas for all the encouragement and discussion. It has really both inspired me and helped me in my quest to create a fairly safe ch***is.
Watch for updates throughout the summer.....

TINGLER

 

I thought this was where I found the triangle relation of the steering arms to the pivot points. If you draw a line from the center of the kingpin to the center point of the rear axle, it should p*** through the tie rod end. That gives the offset for cornering. If you have the tie rod ends in front of the axle and project the line forward through the kingpin, it ends up in the wheel or tire. Thats the way I learned it, anyway. The diagram that shows projected lines from the front spindles to the line of the rear end is needed because the tires travel different diameter circles. If you don't follow those circles, one wheel will be fighting the other. Tire squeal on every corner, I bet. I seem to recall that some production cars had front rack and pinion setups, though. Don't know how they did it..

 

i design racing go karts every day, and ackerman is my dude. here's what he does...



when you turn a corner, the centre of the corner lies on the line of the rear axle. the more you steer, the closer the centre of the corner comes to the car. the closer the centre of the corner is to the car, the MORE the inside front wheel needs to turn, compared to the outside front wheel. go outside to your driver, and pull it round to full lock. look at how much the outside wheel is turned, compared to the inside.

HEAPS MORE!

without ackerman, your two front wheels ARE NOT facing the same way. (that said, too much ackerman has the same effect). by flipping the spindles to the front, you end up with reverse ackerman, which means that the outside wheel would turn MORE than the inside wheel, which is completely back ****wards.

does it help more at low speed? yes... tyres have a poorly named characteristic named slip angle, which basically means that the tyre is happy to go in a direction slightly OFF that which the wheel is actually pointing. that said, you don't want to take a corner at 80 mile and hour, and hope that you're not exceeding an unknown slip angle of a tyre because of the unknown amount of reverse ackerman you're running. ackerman steering was originally conceived to stop cars from tearing up driveways when pulling U-bolts, but it certainly has it's place at speed as well.

ackerman rocks, and he makes your car gooder. leave the spindles the right way round.

 

Guys.Flipping the spindles does not change the geometry at all.

The pivot of the spindle is centered. All the tie rod does is tie them together so that the right wheel does what the left wheel does. With the tierod behind: the left wheel pushes the right wheel, and with the tie rod out front: the left wheel pulls the right one. They both rotate on the same axis. Now you alter the caster and camber and that will change things, but I am afraid you are making to much out of the position of the tie rod. All it does is connect the two hubs. It cannot affect the steeringas long as the caster and camber remain the same. These Hot rods are almost always set up with the axle on a perfect vertical plane (straight up and down), so the the tierod is at 90 degrees regardless of position in front or behind. If you want to get a more precise geometry you can, by adusting the front axle with a positive or negative camber, and the using the length of the tierod to adjust the Toe, but there is little need for it in a situation such as this.
We are talking about a self procaimed RatRod not a formula One racecar.

 

"Guys.Flipping the spindles does not change the geometry at all."

Wrong. If you want your car to drive like a POS and be a danger to yourself and others ignore this principle.

Do a bit of reading on what these guys have posted or search the web of some ch***is books. It DEFINITLEY changes the geometry.

When you turn a corner the inside wheel must (if you want a car that drives correctly) track a smaller arc than the outside wheel.

That's what the Ackerman Principle is all about.

A line drawn thru the left kingpin center and the left steering arm/tie rod hole center must intersect a similar line drawn on the rightside components at a point at the centerline of the rear axle.

HERE'S THE BIG ONE.

This does work with the tie rod in FRONT of the axle, but ONLY if the steering arm/tie rod hole is OUTBOARD of the spindle centerline.

So it works both ways as long as the geometry is correct. Simply reversing the spindle arm just doesn't do it. If you only reverse them the the 2 lines will intersect out in FRONT of the car, bend the steering arm towards the tires will bring the geometry back to where it belongs. The problem with this method is that because of the front wheel offset, diameter and type of brakes, you may not be able to get the steering arm points out far enough.

Check out this web page, lotsa pictures and good down home words.

http://www.nationaltbucketalliance.com/tech_info/ch***is/ackerman/Ackerman.asp

 

I have read extensively on the subject, and am fairly well versed in the laws and concepts of physics. I am however far from being an expert and will not profess to be. I do know however that what I am proposing is not the redneck deathtrap you are trying to make it out to be.
This is tried and true. It has been repeated hundreds of times with excellent results. I would not carelessly recommend a method that I have not used myself, and found to not only be effective, but safe. I will again stress that this is a primitive setup and will never handle like a ferrari, especially since you will be unable to use a crossover. You must use traditional direct draglink setup. I will go one further and conceed that the tierod ends may get into the tire on some wheels if you reposition the tierod arms, but this can be remedied by wheel selection or spacers.

How many times have you seen a setup with the tierod out in front. A bunch if you have been around many altered hotrods. Do you think people would continue to use this set up if it handled that poorly or caused accidents?

Not trying to cause anyone any grief so if you belive that this is not for you, please disregard.