another pinion angle question!!

ok everything i have found out about setting up a pinion angle is with the trans higher than the rear end.my trans is about 1 1/2-2'' higher than the rearend.i set the trans at o deg.and the rear is about 3deg down.the shaft is about 9''' long.i cant move the trans up but i can move it down.it is a leafspring car with a bar holding the rear in place.i have been told it is wrong and would like to find out what is right.any help will be great.

 

on my street cars that run leafs I've always set the pinion angle about a half degree down from whatever the output shaft on the transmission is to acount for a little bit of the spring wrap. On a car like yours where the springs are going to be wrapped much harder and pretty much the whole time it's running I would say 3 degrees down from the output shaft angle would be in the ballpark??? I'm really not sure how much driveshaft length plays into the equation but I'm curious to hear more educated responses.

 

If you extend the output shaft of your trans using an imaginary line and extend the pinion forward, using an imaginary line, these two lines should be parellel and never intersect.

Esentially, if your trans (output shft) is on a decline of 3 degress the pinion should be on an incline of 3 degrees...

With a leaf spring suspension, add an extra .5 degrees approximately to account for spring wrap.

 

they are parallel but the trans is lower then the rear.wich makes the driveshaft run up hill.than the pinion is pointing down.this is the first car that i ever built from scrach.and i was in a hurry to get it done{2 1/2 months}it works fine but i dont think that i set the rear up right.just looking for some good advise.

 

but what if the trans is lower not higher?

 

Just change the name on the diagram. Axle to trans. Trans to axle.

 

flip the pic up the other way.

if its for racing i set mine with the pinion down 2 degree's to allow for windup

 

Lets ask why its wrong. Are you having traction issues or a vibration on the top end.
The way you have it set up from your discription is fine for a drag car. Just rotate the front caps from time to time. Ive run as much as 6* down pinion before. The output shaft being straight in your case is fine.

 

This is what I have read on lots of sites and the way I set up my street car

3 degrees down on tranny 3 up on pinion. Engine centerline and pinoin centerline must be parellel.
Does not matter whether the tranny is higher or lower then the pinion.
Does not matter if you have an offset pinion.
In drag cars more down on the pinion is preferable because the pinion will climb the ring gear so when you are running down the strip it will be at the correct 3 degrees.
What I ve read not from exp.

 

This help?

 

Not advisable to have everything in a straight line as the uj's won't move round the grease in them.

 

Alot of race cars run 0* output shafts. Its a race car. On the street everything else is 100% correct. Its a race car.

 

im just not sure with the trans lower if this effects anything.so should i keep the rear at 3deg.or should i add more?a guy said it is wrong and that is why it picks the front wheels up high then drops then picks them up again.he also said that he cant believe that i havent broke the tranny yet.

 

The u-joint doesn't know which end of the shaft it's on, as long as they are parallel to each other it doesn't matter which end is up and which is down.

 

but i think it does.im looking for good traction and good weight transfer.i think that this is part of my problem.im not sure but i know that there are many people out there that can tell me that it is wrong-right.im just not sure wich way to go.all help is app.thanks.

 

With those big sticky slicks and that bar setup the question I have is : "What's REALLY going on down there during a launch?"

And if I had to guess the answer is "don't know!"

So ..... what about strapping a video camera on there and actually watch what goes on!! My buddy at work duct tapes one on his m/c for track runs - it works amazingly well. I wanna strap one on the digger just for the fun of it.

Anyways that said - 1 piece driveshafts are simple - they want:

1. COMPLIMENTARY U-Joint angles. The illustration above is the standard method of achieving that. However one could ALSO set it up the OTHER way - SAME SAME as far as the mechanics goes.
2. They don't want a TON of angle to contend with - reason being that the driveshaft DOES NOT move at a constant speed (even when teh car IS moving at a constant speed) it actually SPEEDS UP and SLOWS DOWN every 1/4 revolution. Having those angles complimentary means that even though the TRANS has a CONSTANT output speed the driveshaft does not (thanks to ujoint operating angle) to remedy this that second Ujoint having a complimentary angle REVERSES this variation in speed and the result is that the input to the differential is once again constant. So the issue here is that as you make that driveshaft speed up and slow down MORE you are wasting HP - having to deal with inertia and such. SO by keeping it MINIMIZED you MINIMIZE all these issues. Having it at ZERO would be IDEAL IF (a big IF) the only consideration was efficiency. But as stated you also want to smear that grease around a bit - which the rollers WON'T do if there's no working angle. So by having a small working angle we aren't wasting very much HP and we get it to LIVE a lot longer.
3. Balance
4. Phasing

Your setup may be working ideally -- or maybe not - watching it from underneath it seems to me would be a definite help in determining exactly how much windup you are dealing with. Once you know that you can make a good decision on how much "down angle" you want or rather NEED.

Given you rvery short driveshaft - your pencil needs to be a tad sharper than most others. In your case small changes in suspension height may make for some very interesting Ujoint angles real fast.


OTOH you could always go SOLID! ha ha ha

 

Looked at your pic but can't see if the bar is a single bar or a ladder bar, looks like a single bar to me ???

 

single bar.i wanted to put a nother one above it but there isnt much room and was afraid it would hit the rear frame.

 

You need to give more info. ET, 60', wheel base, air pressure, motor size.
I dont think you leaf setup is helping. Does it carry the front or jerk it, how far are the shocks moving front and rear. Thier is alot of variables to it and maybe some one here might get you close. Also high HP short wheelbase cars have the tendency to hop after gear changes and you might be at the limit of your car. Good luck.

 

Looks to carry front end. If the car goes straight and doesn't break parts, I'd say its OK as is. Why did someone say its not correct? I would add a loop at the front of that 'bar' to keep it off the track should something come loose.

 

11.57 1.53 92''17lbs 360ci amc with turbo 400 brake and 4500 stall bte converter.just jerks it up.shocks front 3'' rear about same.only about 350-400 hp to tires.

 

Lots of good info here. I run an off topic drag car (maverick) and ran leaf springs for a few seasons before going to ladder bars and coil springs. Car ran 1.39 60 ft times like clockwork with the front tires in the air. What you need to look at is the "cancelled" angle, should be set up to run at 0 deg to 2 deg "down" while running down the track with the trans and pinion as close to parallel as posible, but starting with a "down" pinion angle. The cancelled angle at the launch with front tires in the air is going to be very dependant on several items; spring rate, vehicle weight, axle extension (drop) while leaving the line, spring wrap, ect. However once the front settles down and for the majority of the run the pinion angle will not be so drastic. Aim to set your cancelled pinion angle to 0 to 2 deg down during this part of the run. This worked best for me. I don't see any reason that the trans being lower than the pinion would be a problem. As far as why the car picks the front end up twice..... I have no idea how the chassis and the chassis components transfering the torque from the axle to the frame have any impact from pinion angle. No lift is imparted on the chassis by the driveshaft or you have much bigger issues....,

 

3" of rear travel hits me as alot for the wheel base. Have you tried stiffer rear shocks/ springs and maybe limiters on the front. It seems to me the car is over reacting on the launch. I think at your weight ( guessing 1800#) you should 60' better. Are you spinning the tires at all after the rear unloads?

 

I just re read this and while I think you are probably ok with the pinion angle, I think the answer to taming the launch might lie in the wheelie bar adjustmant and the front suspension. It looks in the pic of the car with the wheels in the air that the car has a fair amount of air under the front tires, but the wheelie bars havn't touched the ground yet. If you shock load the wheelie bars hard enough, they will load up to a point and then unload by forcing the nose of the car back down. Also, if the wheelie bars are attached to the rear end housing (couldn't tell by the pics, but it looks like they are) in combination with the leaf springs, as they load up they will be unloading the leaf springs as more weight and force is applied to them. At that point this will counter act the spring wrap up which will also start the nose back down toward the track surface. The combination of unloading weight and spring wrap is probably the cause of the wheelie "bounce". Have you tried running the wheelie bars lower? You might also try limiting the amount of drop the front axle has before the front tires start to come off the ground with a strap on each side of the axle. This will also reduce how hard the wheelie bars hit the ground as the chassis will have to lift the weight of the axle and wheels/tires earlier in the launch.

 

i have set the wheelie bars at 3.5''.i do know that when i first leave they touch befor the front wheels come off the ground.yes they are att.to the top of the axle.i put some pics.of my launch.

 

the last one is me comming out of my burnout.not leaveing the line.

 

Have you tried lower air pressure in the slicks? Alot lower? You might be able to tame how hard it "hits" by running less air. That would also allow the tire to squat and help in not lifting the front so hard. The pics of your car also look like the chassis is rolling over on the rear susp. Lots of air between the tire and fender lip on the left side,but very little on the right. The energy "wasted" in lifting the nose, loading the wheelie bars and suspension and rolling the chassis over is E.T. left on the table. I calculated that your car at 2000 lbs with 450 flywheel hp should go mid 9s and you should be able to shed a bunch of time off the 60 ft time. I found a set of plans on he net a couple years ago for home made "cal tracs". They work awsome and should be easy to fab. Even just plain slapper bars can work awsome with some tuning. Here is a pic of my off topic car with leaf springs, slapper bars and 9 inch wide slick at 9.5 psi. 1.39 60 ft ETs, 10.20 at 132mph

 

my 60 fts are 1.4-1.6 dep.on how hot the trans is and how high i lift the front.i know i would pick up some ets if i keep the front end down but it is sooooooooooo much fun picking them up.

 

Somebody correct me if i'm wrong but if i remember correctly ladder bar angle could have a lot to do with your problem as well. I believe if you raise the front of your bars up it will soften the hit at launch and be less likely to produce so much upward motion and more forward motion instead.
Most ladder bars have long mount at front with three or four mounting choices for up and down adjustment to adjust the hit at launch.