Technical > Roo Man's Room
Steering turns issue
dreracecar:
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.
32bantam:
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
wideopen231:
--- Quote from: rooman on January 07, 2014, 02:33:59 PM ---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
--- End quote ---
So wich woul give best steering RoooMan 90 to shaft or 90 to link?
rooman:
--- Quote from: janjon on January 09, 2014, 05:12:09 PM --- 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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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
rooman:
--- Quote from: wideopen231 on January 09, 2014, 08:14:40 PM ---
--- Quote from: rooman on January 07, 2014, 02:33:59 PM ---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
--- End quote ---
So wich woul give best steering RoooMan 90 to shaft or 90 to link?
--- End quote ---
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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