FrontEngineDragsters.Org Forum
Technical => Roo Man's Room => Topic started by: buickfed on January 05, 2014, 07:23:22 PM
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mine is a 68 cali rail with p-s box and spindles. it takes forever to make turns. when we visit different tracks, I always ask for a pass to see if we can make the turns at the end. right turn is not bad. left turn takes about 25% more. at Lebanon valley, left turn only, we had to do 2 k-turns to come back. any ideas w/out cutting it up?
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Pictures would help
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Sounds like your pitman arm needs to be re-aligned. Take the arm off the steering box shaft, find the center of your steering wheel/ box by turning it all the way to the left, then all the way to the right, then turn steering wheel to the center of both. Re-install pit arm, and then adjust draglink so the front wheels turn equal left and right. Make sure the front wheels are not hitting any part of the racecar.
That should straiten you out.
Good Luck
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Another possible issue is that the arm that comes off the steering shaft is to long (the arm that is parallel to the body panel on the side of the car) The length of that arm and the length of the arm on the spindle makes a difference on how it steers.
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HOW LONG IS YOUR CAR?
OURS TAKES TWO FOOTBALL FEILDS AND THE PARKING LOT TO TURN RIGHT OR LEFT.
OUR WHEEL BASE IS 230"
YOU SHOULD WATCH US LOAD AND UNLOAD IT
WE JUST PICK THE FRONT END UP AND IT TURNS LIKE A VW lol 8)
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The P&S box does not turn symetrical. The box it was designed after was offset mounted and they compensated the steering action with long and short ty-rods. The left side was slow because the ty-rod was short and quick acting while the right side was long(thus slow) so it had to be quicker.
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I had a similar problem with my 175" FED. Turned right pretty good but refused to turn left. I found three things that fixed it. First I found the slot in my P&S box was tight on one end. A little grinding and polishing fixed that. Second the long steering link from the pitman arm was too light. It was 3/4" .058 tube. Turning right it was in extension and worked fine but turning left it was in compression and would bow down and wheels wouldn't turn as far. I doubled up the tube with the next size up and it fixed that problem. It still turned a little stiff. So I changed the caster from 30deg to 18deg now it drives like a sports car.
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All three of my P & S boxes must be different then as when I center the arm inside the box, turning the sector shaft until it runs out of travel turns the input shaft the same amount in either direction--starting at 12 o'clock it ends up at 10 and 2 o'clock. If the pitman arm is mounted at 90 degrees to the steering column rather than at 90 degrees to the drag link, that will have an affect on the amount of right and left lock depending on the angle of the steering column relative to the drag link.. Not having the steering arm on the spindle at right angles to the drag link will have the same effect. I did not pull the worm gear out of the box to check the helix on the worm but even it that varied from end to end it would simply change the steering rate, not the total travel.
Roo
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it's 192" w/b. probably part of the problem is the caster. full turn flops the wheels right over. need another person to help straighten it out. will have to check the castor angle. it does needs the 2 footballs fields to turn around. ;D other than that, its a fun ride.
will get my son to post some pictures.
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If someone needs to stand the wheels up. You can bet it has all of 30deg of caster. That would be the place to start. At 150 mph I didn't feel 18deg of caster was a problem. Any faster you will need input from someone else.
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our car has 20* and still layes the wheels over ;) but it backups nice 8) did have 40* (can you say broken wrist)
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our car has 20* and still layes the wheels over ;) but it backups nice 8) did have 40* (can you say broken wrist)
same symptoms but w/o the broken wrist. don't know if I can change the camber to help anything.
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FYI
It is the CASTER you will be changing.
Camber it the amount the wheels tip in or out at he top.
Caster is the amount the king pin is angled to the rear at the top, or in the case of ball joints, how much the top ball joint is behind the lower.
Steve Walczak
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I used to watch the big show cars back up after burnouts and see some pretty alarming-looking front-wheel wobble. At the time I wondered why no one seemed to get all upset about it, just went on about their business and made the pass without the fronts falling off. Upon getting my FED bout 10 years back, and having the wobble thing happen to me I understood what was going on, that the caster that made it stable going forward did the opposite in reverse, especially if you let speed build and get too far from straight at the same time. "Oh-Sh*t" moment but no broken wrists or otherwise. So just keep speed moderate and no wild steering and all is well. It's not like I'm backing up from half-track, anyway.
Just for grins, (not feeling the need for sh*ts), me and the kitten just went and measured the caster on my car, it reads 25' on one side, 28' on the other.
Evidently, old-school thought was that more was gooder, seems modern thought might be that less is more, or at least that less is enough.
Any expert opinions on what is optimum? And any relation to wheelbase or anything else?
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castor, right. measured it tonight, 40*. hopefully if I can make it less w/o cutting anything up. just need a little warmer weather to start the furnace up. I have an old green house heater in my garage and it likes to burn fuel. :(
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Caster changed when the tires changed--front runners will work with less because of their flat profile and compound verses an Avon speedmaster which has a round profile and needs the extra caster to roll around the tread.
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40.......man that is a BUNCH!!!! I don't think a shopping cart has that much!!! lol
15 is usally enough for most cars...but I will let Roo chime in.
Steve
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All three of my P & S boxes must be different then as when I center the arm inside the box, turning the sector shaft until it runs out of travel turns the input shaft the same amount in either direction--starting at 12 o'clock it ends up at 10 and 2 o'clock. If the pitman arm is mounted at 90 degrees to the steering column rather than at 90 degrees to the drag link, that will have an affect on the amount of right and left lock depending on the angle of the steering column relative to the drag link.. Not having the steering arm on the spindle at right angles to the drag link will have the same effect. I did not pull the worm gear out of the box to check the helix on the worm but even it that varied from end to end it would simply change the steering rate, not the total travel.
Roo
So wich woul give best steering RoooMan 90 to shaft or 90 to link?
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I used to watch the big show cars back up after burnouts and see some pretty alarming-looking front-wheel wobble. At the time I wondered why no one seemed to get all upset about it, just went on about their business and made the pass without the fronts falling off. Upon getting my FED bout 10 years back, and having the wobble thing happen to me I understood what was going on, that the caster that made it stable going forward did the opposite in reverse, especially if you let speed build and get too far from straight at the same time. "Oh-Sh*t" moment but no broken wrists or otherwise. So just keep speed moderate and no wild steering and all is well. It's not like I'm backing up from half-track, anyway.
Just for grins, (not feeling the need for sh*ts), me and the kitten just went and measured the caster on my car, it reads 25' on one side, 28' on the other.
Evidently, old-school thought was that more was gooder, seems modern thought might be that less is more, or at least that less is enough.
Any expert opinions on what is optimum? And any relation to wheelbase or anything else?
I normally run 20 degrees on dragsters (front or back motor)and have used anything from 10 to 15 on altereds etc depending on engine placement. FYI most modern top fuel cars are in the 18-20 range and the JFR funny cars were 6 degrees when I was working there.
Roo
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All three of my P & S boxes must be different then as when I center the arm inside the box, turning the sector shaft until it runs out of travel turns the input shaft the same amount in either direction--starting at 12 o'clock it ends up at 10 and 2 o'clock. If the pitman arm is mounted at 90 degrees to the steering column rather than at 90 degrees to the drag link, that will have an affect on the amount of right and left lock depending on the angle of the steering column relative to the drag link.. Not having the steering arm on the spindle at right angles to the drag link will have the same effect. I did not pull the worm gear out of the box to check the helix on the worm but even it that varied from end to end it would simply change the steering rate, not the total travel.
Roo
So wich woul give best steering RoooMan 90 to shaft or 90 to link?
Normally having the link at 90 degrees to the arms is the correct geometry to have symmetrical steering. As the arm moves off center (90 degrees) it will move the link less per degree of travel the further it is around the arc. With a typical 5" pittman arm the effect is not that much but it is there. Most standard steering arms are 6" center to center and thus are a little more sensitive to the angle. If the link is not square with the arm at the starting point the travel will initially accelerate in one direction before slowing down while in the opposite direction it will be falling off right from the start.
Roo
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What I was thinking.I must have miss read post earlier on subject.Man that neve happens!
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It would seem to me that the system does not know or care what angle the pitman arm might be to the steering shaft, it cares somewhat or greatly whether it's 90 degrees to the link, with the wheels pointed straight ahead, as regards equal rates and equal travel left and right. Same with front bellcrank, if equipped.
John
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It would seem to me that the system does not know or care what angle the pitman arm might be to the steering shaft, it cares somewhat or greatly whether it's 90 degrees to the link, with the wheels pointed straight ahead, as regards equal rates and equal travel left and right. Same with front bellcrank, if equipped.
John
Exactly
Roo
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Should be able to adjust your radius rods to bring the caster in, and set it the same on both sides. Once you've done that, recheck your toe-in, try for 1/8" in at front.
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Should be able to adjust your radius rods to bring the caster in, and set it the same on both sides. Once you've done that, recheck your toe-in, try for 1/8" in at front.
With most radius rod set ups it is hard to reduce the caster more than a few degrees through adjustment. Major changes usually mean longer tubes so that there is still sufficient rod end engagement in the radius rod. The taller the axle brackets are the less effective lengthening the rods will be. With a tube axle, if the caster varies from side to side you are stuck with that variation as moving one side will move the other the same amount.
On the subject of toe, if you run a bellcrank to turn longitudinal motion into lateral and have an articulated front end (i.e. suspension) you must run from the bellcrank to one steering arm and then from there to the other arm with a link (like an early Ford beam axle car). If you run links from the bellcrank to each steering arm and you have any significant suspension travel the bump steer (toe in-out) will be diabolical. Ask me how I know :)
Roo
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if I lengthen the rods, it will make the spindle c/line higher, therefore the front end will sit higher. correct? is this a bad thing?
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if I lengthen the rods, it will make the spindle c/line higher, therefore the front end will sit higher. correct? is this a bad thing?
Lengthening the rods will actually make the center part of the axle sit lower as the ends of the axle will be swinging up in an arc. Your wheelbase will also increase a bit as the spindle moves forward as well as up (say from 2 o'clock to 1 o'clock). In other words if the wheel/tire diameter stays the same and the spindle is raised relative to the lowest part of the axle the axle has to be lower for the wheels to still be on the ground.
Roo
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Ain't geometry wonderful? And widely misunderstood?
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I have P&S steering as well, before I attached the pitman arm I rotated the steering full left to full right ,found the center and marked the steering box and shaft next to the same spot so I know when the box is centered.
the pitman arm cannot be straight down unless the steering box is horizontal with the ground-this means I had to have the pitman arm somewhat angled to the rear of the car so the steering box was centered as the wheels were at dead straight ahead, this allows me equal turning raduius left and right, but it's also only a 150" car.
another issue I dont see many address is the angle of the steering arms off the front spindles.
the proper angle should be- draw a straight line through the center of the king pin to the center of the rear end, that string line will show you where the steering arm should attach to the tie rod.
this ensures the inside wheel will always turn the proper radius of a shorter turn than the outside wheel. dragsters dont turn? ever see a car a bit loose, turn to correct and peel the front tires off? ever wonder why?
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This red I sold last year to friend of mine. If you look at right front wheel you can see steering arm does have double bend in it, possibly done to align it with rear end (what Geri wrote)??? Don’t know for sure, bought car from second owner in 2003 at chrr, then picked car up in LA on way home, his friend who was there said he had it made for him by Don Long. That car was so smooth running down the track, straight as an arrow, no steering required. Probably could have made a pass without a driver in it : ) DF
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Absolutely NOT a "Don Long" car--- period
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I have SPE box and I located center.Slid the pitman arm on running straight up and down and I can turn front wheels to point the hit last lint and actuall made arm at spindle 1/2" longet to make sure tire did not rub and link is only 3/4 from body at that point. I do have 6" pitman to help clear headers with Hemi and still have to put slight bend in it at that. MAybe got lucky or just screwedup in right order but seems to work great.
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dreracecar – thank you for letting me know : ) I had bought the car for $2500 at the chrr and just sold it to my friend for $2000, I definitely got $500 worth of enjoyment out of it the past 10 years. On another note, of all the comments made on Glenn’s forum, I look forward to reading yours the most, because they are entertaining and enlightening (e.g. helpful) at same time. Thank you for sharing your experience and good information so timely, please do continue! DF
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dreracecar – thank you for letting me know : ) I had bought the car for $2500 at the chrr and just sold it to my friend for $2000, I definitely got $500 worth of enjoyment out of it the past 10 years. On another note, of all the comments made on Glenn’s forum, I look forward to reading yours the most, because they are entertaining and enlightening (e.g. helpful) at same time. Thank you for sharing your experience and good information so timely, please do continue! DF
Wow, a fan for Bruce. :) you are doing better over here than on the HAMB mate.
Roo
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No Geri, I have never seen tires skinned of the rims from improper Akerman, nor do I care to, especially from anywhere near 150" away!
By the way, kudos on your restoration! Maybe someday I'll get to hear it run up close.
John
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;D
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and I haven't done anything to the axle yet because it's too cold in the garage.