Every car I set up with a panhard. In fact, nearly every mass production car I have ever seen with a panhard rod is set up the exact same way. See for yourself by Googleing panhard rod.
I agree. The frame appears to have only the single dropped cross member with a pair of forward facing braces so it definitely lacks torsional strength. Having the front ladder bar mounts close together will allow the rear end to rotate relative to the frame more than a set of drag race style parallel ladder bars but also but also allow the engine torque to twist the frame more. If the torque induced roll is high enough it may be pulling the front axle sideways. On the subject of the front end geometry try putting the front half of the car on stands so the wheels clear the ground and then jack the axle up while watching what happens with the lateral location of the axle and also the effect the travel has on the steering geometry. Or try jacking the frame up under one frame rail to simulate the chassis roll. Roo
When dealing with oval track cars the following are really good rules to follow. A panhard bar that is attached to the right side of the frame lowers during chassis roll. However, a panhard bar that is attached to the left side of the frame raises during chassis roll. However, the effects on handling of a right side versus a left side frame mounting are not always predictable. The location of the panhard's axle mount can counteract any predictable handling effects. The current tendency is to mount the panhard to the left side of the dirt car chassis and to the right side of asphalt chassis.
If your mount the rear panhard like that and front panhard (and drag link with a vega box) from the drivers side frame to the passenger side axle the car will twist in compression and rebound (top view). Correct? I have experienced this before but it always has been on parallel 4 link cars with off the shelf chassis. I always thought it was roll steer induced by torque and terrible shock valving. I usually don't see it with rear anti roll bars.
I have never notice any odd characteristics from crossed panhards like you describe. It's a matter of using torque to your advantage. Front axle with cross steer needs to have the panhard parallel and similar lengths to deal with steering torque as well as body sway (real sway, not roll like we use "sway bars" for). Since there is no acceleration torque to deal with on the the front there is no other reason for the mounting to either side. Kinda busy right now, but check out this thread: http://www.eng-tips.com/viewthread.cfm?qid=267284&page=1
Good reading but I didn't see the part where it explained how a panhard is used to control torque steer. Maybe it is hidden in all that engineering talk.
Yeah, crap it's the wrong link. I thought I had it bookmarked. I'm a bit pressed for time right now, but feel free to check out the threads here. Those guys cover it a lot. http://www.eng-tips.com/gsearch.cfm...rd+rod&sa=Go&siteurl=www.eng-tips.com%2F#1061
""Because your shocks are mounted at an angle,you have to apply a correction factor to the spring rate.(The shock maker can provide the correct factor based on angle your shocks are mounted.) We'll use .89 210 lbs/in *.89=186.9 lbs per inch. Spent some time with some scales and substitute in the values for your car and can dial the spring rate you need."" The above is wrong in the fact that you don't multiply by the correction factor, you divide..Thus the 210lbs/in per above, divided by the .89 will be 235lbs/in.. http://www.qa1.net/qa1_motorsports/images/drag_tech.pdf
my pan hard for my rear was built to mount to the axle on the passenger side..and the frame mount to the drivers side.. if this is wrong..IF than why are there any made to work that way? and if the function is to keep the rear end centered and it does this,,why would it matter what side it was anchored on? its not like i have 6" of travel in a Model A Hot rod with coil overs...so the Arc of the pan hard is such that it is almost non existant. Just looking for teaching..not a lecture. others that i have seen set up like I have mentioned, have 0 issues I was also told to set up my pan hard..(if used) for my front end , to anchor it on the same side cross steer vega set up
i think its that big lump of steel up front thats your problem i have a nice little 4banger ic can do a quick swap for you just jokeing i think its frame twist do yourdoor gaps get bigger when lift hapens
Like Don said, if it works then you're fine. The OP has an issue and the symptoms he describes fit my diagnosis. The reason why is torque. If the drive shaft is spinning clockwise (viewed from the rear) then the chassis sees a counter clockwise torque. This causes the right rear to unload, you will notice most (not all) open drive axle cars spin the right rear tire. :: added:: Using the drive shaft torque in this case, the right side of the car is squatting thus lowering the panhard rod mount. This puts lateral load on the right side tire, similar to anti dive on a front suspension or anti-squat when dealing with the longitudinal force. I would love to plot it out for you guys in a nice simple graphic. Maybe after the Open House party I will have more than 10 minutes to check in. There are reasons for mounting it the other way, cornering for one. There can be roll axis benefits in balancing cornering loads. But we are talking about drag racing, straight line performance here.
Girls, girls , girls. On a street car it virtually makes no difference which side the panard rod is mounted on the rear. More important are the locating and anchor points as well as the angle of attachment. The arc swing of the panard rod determines the lateral axle shift during the bump or roll of the chassis during operation. The longer the arm and more parallel and closer proximity to the center line of the axle the less lateral movement. Below is similar to above and crossing the axle center is also of importance but more for high speed fine tuning purposes. You can determine the lateral scuff of your panard rod by simply unhooking it at the axle mount. Take a straight edge at the same height of attachment and form a perpendicular to the floor and mark the spot of interesction. Now to determine the lateral movement just repeat the same process by raising the rod end up 3" over your mount and marking the representative point with a dot on the floor and then lowering the rod end 3" under your mount and marking it again on the floor for a reference point. A comparison of these three points will give you an idea how much lateral movement you have left or right and if it is offset depending on the up or down motion. Your ride dots should be almost next to each other favoring the frame mount for a neutural ride and any dot that is a good distance from the ride height dot or crosses outside the original ride height dot indicates a potential issue. Panard rod mount on the front of a beam axle car are up for debate but the approach of putting the frame anchor on the same side as the cross steering box mount produces the least amount of conflict during the suspension operation. By putting the panard rod mount on the same side as the steering box mount both pivot points are in relatively the same location. Because most hot rods are limited to only 2-3 inches of travel in the suspension, the panard rod and the drag link make almost concentric arcs and do not influence the steering during bump or roll. Panard rod on a side steer car would have no influence on the steering.
Exactly I keep my right rear preloaded that it spins the left. Also my panhard is frame anchored to the frame on the left and tracks fine under hard power.I'll add. More on a Oct rather than my phone
It's definitely frame twist. I had the same problem in my '32 Chev. When the body started breaking I decided to do something about it. Here's how I cured it. Once you get the frame solid then you can worry about panhard bars, etc.
I have a chassis very similar to yours on my truck with a blown 327. I once mounted a video camera on the side of the cowl area while I was playing around at an autocross event. The video shows a significant amount of frame flex even with the tires smoking. I could only imagine how much if it actually hooked up BTW in the video the front suspension stays virtually unchanged all the flex appeared to be from the motor back. So I would assume you are getting enough flex and rear suspension movement from unloading the RR to cause a bit of a rear steer situation.
I don't see any center cross member, ie. K member. There is a known fact the Howel Truss doe's wonders. The transmission mount is not a cross member. Just the opinion of an old guy.
Thanks for all the ideas. Upon further investigation I believe the rearend is not square. The left side is further back than the right side which would steer the rear of the car to the left making the car feel like it is pulling to the right. When the rear of the car steps out to the left I'm having to steer to the left..Everything is starting to make sence. When my lighter rate coil springs come in I'll correct everything at once. Then I'll give it a good test.
If this is true the car would crab walk sideways.....have someone follow you.....I still think your frame is weak..ie no center K crossmember to keep the frame from twisting
Put a zip tie on all 4 shock shafts and slide them up against the shock body. Make a hard pass with it...once. Check the shock travel by how far the zip ties have moved. If you can feel the car twist and the zip ties don't move much at all, the frame is flexing. Ditto on the rear ladders...beef those mounts up.
May I make my only correction to ElPolacko? Excuse me please, I KNOW it's a typo........ Ummmmm, When looking at the headlights of almost every rear wheel drive vehicle, the engine crankshaft and driveshaft will rotates clockwise. The exception I know of to this is a Honda car engine, so that definitely does not apply or belong here. Everything else described correctly. Another post asked about only one rear wheel pushing the car. That is a common misconception of a "one wheel wonder, peg leg, one tire on fire" rearend. Only other way one wheel pushing could be true would be if you had a locker diff or spool with one broken axle. "One tire on fire" is because engine torque had changed suspension action to unload the right rear tire and making traction lesser than the left rear. Therefore, both have torque applied, one overcomes available traction because of torque induced suspension weight changes. That's not to say tire choice and diff choice won't make a vehicle wag it's nose with throttle and decell in a stock current vehicle. Done it.
When I first started drag racing my truck, it was so unpredictable. Some may remember me hanging the tail out on a 2-3 shift and nearly taking out the 1/8 mile marker at Day of the drags some number of years ago. I went through everything, nothing out of square, no squished bushings, no odd pre-load or corner weighting, I was stumped until I notices a scuff mark on the back of the axle housing. The panhard rod is a good 1.5" away but it also had a corresponding scuff mark. The axle housing was flexing under load enough to contact! I since girdled the rear and straightened the housing and it launches without much drama. I still have an instant center issue to deal with, just no time. We are all here to learn.
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