What Pinion Angle are you running?

[DARK AGE 53]

Anyone know?

[Tom Cole]

2.5°-3°

[justfreaky]

Hi Al,
 Are you asking about the actual pinion angle, or the angle of the top link? I'm getting ready to mount my rear end and am also curious.
 Dwarf Car Technology, by Steve Smith, recomends the top link be 7 to 10 degrees.
  " The upper link should be angled downhill (towards the front of the car) at a seven-degree to ten-degree angle. This promotes good traction without the problems associated with rear end lightness and wheel hop. On a Dwarf Car, with the rear pivot point of the upper trailing link setting 9 inches above the axle centerline, a 7-degree downhill angle creates 21 percent anti-squat. A 10-degree downhill angle creates 28.5 percent anti-squat."
(page 52 in my book)
 Most of the info in the book relates to both Dwarf and Legends Cars. Not a lot of difference that I can see. Legends Cars have stricter rules governing what parts must be used.
 Hope this info helps.
 
 My best to you this season.
 Steve

[DARK AGE 53]

2.5°-3°

Thanks for the info, I was at less then 2.5 so I turned the top link to get me closer to those numbers.

Hey Steve, Good info also, I marked the top link just in case I need to turn it back some.

What gear are you installing, it looks like people have anywhere from two to three different gears for there cars.

Regards,
Al

[Tom Cole]

Steve, I can't figure how I could change the 3rd link angle.  On my car, the lollypop and the 3rd link bracket on the rear end pumpkin are not adjustable.  All I can do is alter the length of the rod, which changes the angle, but only slightly.

Al, it is important that you check the squareness of rear end when you change the third link length.  You have to get the angle right AND get the axle square.  That is often a tricky thing .

[DARK AGE 53]

Al, it is important that you check the squareness of rear end when you change the third link length.  You have to get the angle right AND get the axle square.  That is often a tricky thing .

Tom, Why would adjusting the upper rear link affect the axle squareness , I could see if you adjusted one of the trailing arms it could affect the squareness  of the axle. Thanks.

[justfreaky]

Hi Tom,
 The front mounting bracket has several different holes, so can be adjusted up or down. This is on a Dwarf, with a solid top link. I wasn't sure if the Legends ran the same set up. I was looking at the pic on www.littleracecars.com. Looked like similar set up as mine.
Sounds like your set up works slightly different. I would think that the principle is the same, moving the pinion angle either up or down.
 I'd like to get a better look at the Legends Car suspention, both front and rear. Unfortunately, up here in Montana, I don't get to see many Dwarfs or Legends Cars. The few Dwarf Cars I've seen here use very crude leaf springs in the rear. Probably not legal anywhere. I heard that they race Legends Cars in Kalispell, but that's a 4 hour drive from where I live. I started building my car when I lived in Nebraska. What I'll most likely do is run SCCA autocross. Not too many options for me right now, unless I can get the local track interested.
 I do appreciate this forum; as I get some great ideas, as I continue my build. I try to share what I can. If it helps Great! If not, Sorry! Don't want to upset anyone.
 Best of luck to all this season.
 Steve
 

[DARK AGE 53]

Hey Steve,

I'll take a bunch of pics today of the front and rear  suspentions and e-mail them to you later.

Al

[justfreaky]

Al,
 Thanks for the pics. !!!
 I'm guessing Tom is using a rubber torque link. My set up is similar to yours except for the front mount has multiple mounting holes. Either way, as you shorten the link, the pinion angle moves downward and the rear of the link move upward. The rubber doughnut would allow the angle to change slightly during acceleration and brakeing.
I do have one of those rubber torque links also. Do you think it is the better compromise between acceleration and brakeing? Sounds reasonable.
 Curious,
 Steve

[Tom Cole]

I'm not exactly sure why, but I measured it, so I know it is happens.

Here is my explanation.  May be right, may be wrong.
As you alter the third link length, it twists the axle housing, which changes the angle of the radius rod bracket on the bottom of the axle to lean toward, or away from the radius rod lollypop on the chassis.  That changes the distance between the centerline of the axle and the lollypop.  If you have different radius rod lengths or angles to begin with, it will effect each side a little differently.   It is the same as changing radius rod lengths.  When you change them, you are changing the arc of travel and effecting the rear steer of the car.  I am VERY particular about knowing the squareness of my car's rear end.

How much or how little these things will change and the magnitude of their effect is something that I do not know how to calculate.  I probably could if I really wanted to, but I'm still dealing with bigger fish with respect to setup.  I do know, however, that my son can tell when I change the RR radius rod length by as little as 1/2 of a turn.  You can see it on the clock and you hear about it when he comes off.

Thanks for the explanation Steve.  Your info and insight has me questioning things, and that is what I need.  I'm not going to learn a darn thing doing everything the same way over and over.

[DARK AGE 53]

Al,
 Thanks for the pics. !!!
 I'm guessing Tom is using a rubber torque link. My set up is similar to yours except for the front mount has multiple mounting holes. Either way, as you shorten the link, the pinion angle moves downward and the rear of the link move upward. The rubber doughnut would allow the angle to change slightly during acceleration and brakeing.
I do have one of those rubber torque links also. Do you think it is the better compromise between acceleration and brakeing? Sounds reasonable.
 Curious,
 Steve

Steve,
I must be missing something here, what rubber doughnut are you talking about...the only doughnuts I know about are the dozen glazed doughnuts I bought today. BTW, I'm sure my doughnuts taste better then any rubber doughnuts also.

Al

[justfreaky]

I hear ya on that glazed doughnut
I think it called a biscuit bar. It's similar to your upper link, but one end has  hard rubber doughnuts. somewhat like a strut or lower control arm brace on a street vehicle.
Doughnuts, Biscuits .... I'm getting hungry! 
 Steve

[qweedqwag]

The angle of the third link is very important, I was getting into a 4 wheel drift in the middle of the corner because I had to little angle on the third link, moving  the angle to be more down towards the from of the cars stop the rear end from lifting under braking  and keeping me planted to the track with on the brakes hard, beware that to much angle will rob horsepower because it put the driveshaft in a bind, I measure mine from the distance from the frame rail to the u-joint, nothing closer than 1 and 1/2 inches.


Later boys,

Mike

[Tom Cole]

Mike, what you are describing is the pinion angle.  What was confusing us was Steve's description of the third link angle change.  In other words, the angle of the aluminum bar.  Since, on a Legends car, the third link mounting brackets are in fixed positions, the angle only changes based on length adjustment, which is not as substantial as it would be if you could change the height of the lollypop on the chassis or if the bracket on the rear end pumpkin had several holes from which to choose.

[legends13]

You guys are making this too complicated. get a smart tool (digital level) or an angle finder. put it on the bottom of the third member (rear end gear) with the car on a level surface. Get it close to 2-2.5 degrees. after you get this correct, do as admin said and recheck square. It should not have moved unless you have a bent heim or mounting tab onthe housing, but it is good to check, since almost everycar has a slight variation.

As far as the top link, whatever it takes to get the pinion angle you need is where it should be. Legends have fixed mounting points so you can't adjust it other then lenght.

Brad