Dragster Pinion Angle

Discussion in 'InsideTopAlcohol.com Tech Questions' started by BEDNAR1320, Dec 10, 2018.

  1. BEDNAR1320

    BEDNAR1320 Member

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    I would like thoughts on what effects pinion angle has on a hard tail dragster. My 09 272" Spitzer has about 1.5° up angle relative to the top frame rail. Measuring from the top frame rail to the deck surface of the block, it's 1/2" higher at the front.

    Trying to get a handle on my wheelie issues...……..
     
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  2. Bob Meyer

    Bob Meyer Comp Eliminator

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    Lord knows what angle the top rail is ! Find a level surface and measure to ground. Much success can be had with the crank bolt CL, 1/2" higher than the end of pinion. Speaking in degrees of angle in somewhere near 5' out from rear axle center is almost impossible, you need to speak in tenths of a degree.
    Tires, air pressure, wheel width, RPM, launch ratio, and holding your mouth right are more important than changing your car or fiddling with wheelie bars (no-no for solid mount rear end). Always remember the true definition of a wheelstand….."the back tires aren't going around fast enough" ! Let that sink in for a week, it'll be cheaper! ;)
     
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  3. BEDNAR1320

    BEDNAR1320 Member

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    Thanks for the response, Bob. I'll put it on the ground and see what is then. On this car with rear slips right behind the cage, the pinion/crank angle goes way high as soon as it leaves with the slips at 1/4". I was thinking of tightening them to see what that will do.
     
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  4. sammy christian

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    tighten the slips, lower the engine angle, more power-- all adds up to less bite/more wheelspeed.
    I think you are answering your own questions/
    Comes back to those previous statements about wheelies- underpowered for the setup.
    You're way past this, but, it's funny listening to certain friends that are trying to go TD fast but think they're going to do it with a deadhook bracket car leave, wheels in the beams. Usually doesn't work at the range you're talking about.
     
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  5. BEDNAR1320

    BEDNAR1320 Member

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    Yup, when I setup to go 3.80's or so it seems to be pretty happy, if I try and go quicker it's not so happy and that's usually when conditions are better including track conditions...…….
     
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  6. Will Hanna

    Will Hanna We put the 'inside' in Top Alcohol
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    as a frame of reference most TAD's are 0-.25 deg. As Bob said, that top frame rail is relative.

    lock that rear slip up, should help a bunch in my opinion.

    one well known dragster chassis builder told me that slips can be inconsistent because if you don't hit the tire the same, the chassis works different.
     
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  7. BEDNAR1320

    BEDNAR1320 Member

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    Well, just put the car on the ground and the engine is level, also measured the pinion CL to ground and front of the crank CL to ground to confirm it.

    Like has been said with the slips loose that 0° angle goes way up at the hit...……...I have plenty of pictures to prove it.
     
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  8. Bob Meyer

    Bob Meyer Comp Eliminator

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    Anybody in your area know how to weld ? ;)
     
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  9. BEDNAR1320

    BEDNAR1320 Member

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    Absolutely.

    But all I have to do is tighten the bolts up to stop them from moving....
     
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  10. Will Hanna

    Will Hanna We put the 'inside' in Top Alcohol
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    Ok, I'll bite...

    Uncle Bob, why don't you like adjusting the wheelie bar....
     
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  11. Bob Meyer

    Bob Meyer Comp Eliminator

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    Will; the week isn't up yet, no quick decisions allowed.
    Bonus hint: fix what's wrong first, it's 90 degrees away from your thoughts.o_O
     
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  12. Will Hanna

    Will Hanna We put the 'inside' in Top Alcohol
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    I will say in a perfect world the tire stays round and you never hit the wheelie bar. I have some theories on how to make things better than the low bar theory. Might get a chance to play with some things on my car, but a dial in car isn't exactly the best car to go try stuff.
     
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  13. rb0804

    rb0804 Member

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    My experience with slip tubes is that they would basically go down a dirt road. I have never seen one with limiters to stop them from moving. Surprised with all the talk of pinion angle and such, no one mentioned the position of the mid-plate in relation to the rear end. Some really fast top alcohol guys in dragster and funny car both rely on tagging that bar at the hit to get up on the tire. I would imagine running a car this way is hard on the chassis, as one of the bars I saw was pretty “well used”. I tried this method a few times and could never get it to work, I prefer the method Will Hanna described above as keeping the tire round, but you have to get up after it pretty good to make this happen and get pretty creative with the timing curve. I call the wheelie bar an automatic wheelspeed generator.

    At Charlotte, I seen a dragster that had some monstrosity mounted below the rear with two wheelie bar wheels and such in addition to the regular wheelie bar. Looked to me like it was some sort of ride height limiter. I only got to watch one of their runs but when they took off all 3 wheels hit and the car proceeded into tire shake. I also recently seen a promod that had an underslung chassis similar to a Mauney or Pittman type car, but the wheelie bar was hooked to the rear of the chassis not to the rear.
     
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  14. Will Hanna

    Will Hanna We put the 'inside' in Top Alcohol
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    The dragster in Charlotte was most likely Doug Doucette's car with Alan Bradshaw driving. I saw it in Ennis and it was a thing of beauty. Two wheels under the rear end and the wheelie bar. They all touched about 2.5" and up on the tire and gone.

    Dragsters are a different animal that FC's, but more often than not, on a FC, the car doesn't start moving forward until it hits the bar and stops moving downward.
     
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  15. rb0804

    rb0804 Member

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    It sure was. I took a picture of it in the staging lanes. They have a super cool tow rig as well, both the truck and trailer! I however wasn’t trying to mention names...
     
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  16. BEDNAR1320

    BEDNAR1320 Member

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    Will what true wheel speed do you shoot for at .25, .50 when going .940-.930 60's?
     
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  17. rb0804

    rb0804 Member

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    What rear gear?
     
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  18. BEDNAR1320

    BEDNAR1320 Member

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    4.10, but that's why I said true wheel speed, DS divided by gear ratio
     
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  19. Will Hanna

    Will Hanna We put the 'inside' in Top Alcohol
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    800-850 axle speed at 1.0. That's off the button or WOT on a clutch, not zero off DS. Multiply that times your ratio to get driveshaft speed. When you get close to 900 you are getting down in the low .90's or better if you have the power to carry that.

    That's a pretty reasonably hooked, not a big controlled spin number.
     
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  20. Will Hanna

    Will Hanna We put the 'inside' in Top Alcohol
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    Prior to 1.0 I'm more of a 'shape' of the line guy than a bunch of targets. I have notes obviously but I want to get the hit right, then have a nice arc to 1.0. We have all had combos that were 'safe,' in that we know they will work in certain conditions, but may not be 'right' in terms of really getting the tire happy early. You can develop some early check points from these type runs that will be a reference for your combo, but not a 'blanket' reference for all cars. You really gotta commit some time and testing to really get a car right off the hit, especially a solid car. I think the payoff is worth it if you can have a baseline that minimizes sidewall gyration cycles. That's when you can carry some good wheelspeed to 1.0 and get away with it.
     
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