Landracing Forum
Tech Information => Technical Discussion => Topic started by: entropy on June 29, 2015, 05:47:19 AM
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Hi guys!
I am curious as to exactly what steering ratio our TFA lakester has????
Calculations say it should have 24.7:1, but i'd like to measure it.
Mr google says:
"Steering ratio is the ratio of the number of degrees turned at the steering wheel vs. the number of degrees the front wheels are deflected".
Does anyone have a simple method for doing this?
karl
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I was taught to use effective angle, versus mechanical angle. You set the front wheels straight ahead, then rotate the steering wheel 360 degrees. Effective angle is the degree change of both front wheels, summed, divided by two. Divide the 360 number by the averaged wheel angle change to get your result.
Your Ackerman angles will cause the front wheels to change angle unevenly (side to side compared). If the Ackerman is wrong, you will see that problem by checking ratio results at 90, 180, 270 degree points. Checking effective angles at those multiple data points can be a real eye opener.
You will see that ratio number is a continual change, from straight ahead to full lock...whatever is available.
I really prefer checking this on alignment turn plates, as opposed to measuring wheel rim angle change. Your car only cares about what the wheel to ground interaction does. The initial turn plate line is marked, and the dgree changes are measured on the turn plate, not the wheel. Talk to a local aliignment shop about using or getting their help with a pair of turn plates off the alignment rack.
Hope this helps.
JimL
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JimL
Thanks much for your explanation and turning me on to Alignment turn plates.
I know that its surely overkill for my purposes but to satisfy my curiosity, i will buy a set of plates, from this place or other.
http://gilsmithracingfab.com/alignment-turn-plates.html
thanks again,
karl
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IF you have a solid mounted frt axel why not just put the car on jack stands :?
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IF you have a solid mounted frt axel why not just put the car on jack stands :?
Sparky,
that occured to me also after i looked at how the alignment plates work.
I dug around my lil shop and found 2 x 11" crank degree wheels i used to use in building my MC engines, setting up the cams. It seems i can jigger something up without spending anything!
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IF you have a solid mounted frt axel why not just put the car on jack stands :?
Sparky,
that occured to me also after i looked at how the alignment plates work.
I dug around my lil shop and found 2 x 11" crank degree wheels i used to use in building my MC engines, setting up the cams. It seems i can jigger something up without spending anything!
Try using some ball bearing lazy susan bearings from a home improvement center for the base part. If you can't find ones large enough in diameter, check Woodworkers Hardware: http://www.wwhardware.com/catalogsearch/result?order=relevance&dir=asc&q=lazy+susan+bearings They go up to 17" diameter.
:cheers:
Fordboy
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We have used the el cheapo HF laser to mark on the shop floor and string lines --instead of a degree wheel we had a HF plastic protractor
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i also have a fine, imported, "precision" HF laser and will find a way to make it work.
all i want to so is check the steering ratio and see Ackerman at work (thanks JimL), hopefully no mods will be needed as a result of this test, just curious.
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we just held it against the wheel on both sides and marked the straight ahead spot on both wheels turned the wheels and again marked the spots ---and stared compareing
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If you can't do it off the ground, a simple & cheap way to do it is how I pull a set of duals off a semi on the side of the road.
Put a smooth sheet of something under each wheel, throw down some liquid soap & park your car on it.
This will also allow the tire to move sideways due to any caster or scrub.
I have not found any "fine china" lazers from HF that would repeat both ways so you might want to check yours on both sides of a vertical flat surface to see what the variation is.
Sid.
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lol Sid is so spot on there is not much HF that is symmetrical
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thanks guys, as soon as i get some other stuff crossed off the list, i will gin up the steering angle measurement process.
this stuff is just sooooo much fun, but Speed Week is roaring at us.
Last July the car was in a spotless hanger, acres of space and ex-partner Don doing most of the work, all the engine stuff.
Now the car is sharing a 3 car garage w/my wife's jalopy, i'm doing everything AND i have to learn to manage the engine. Ah, the good ole days... Real different from simply managing 2 race bikes. Every day i have more & more appreciation for you "car guys". Cars are much more "work" than bikes.
karl
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Ditto on that Karl. Others may know what you're building but I've been living under a rock (streamliner), can you enlighten the hillbilly? :-D
Sid.
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Sid,
sorry about the delay :(
TeamFatAzero has a front wheel drive B lakester w a crate 383" Chev engine. With its modest hp, we are not looking at all for records...
At World Of Speed last year we made its first trips down the track, got an A license (foot on the floor, 209 exit speed), but i was concerned about the stability. Some folks said "hey ex-motorcycle guy, you just gotta learn to drive the car :) Other people gave items to assure are set up right.
Joe at Delaware Chassis Works tweaked the steering and aligned the rear axle this winter/spring. This year at Speed Week we are just looking for me to be comfortable in the drivers seat. If the handling is the same as last year, i'll know its my technique and i'll deal with it.
karl
(https://lh6.googleusercontent.com/-_EixWzJcwjc/VAvMmB4NpOI/AAAAAAAAB6E/RZZhcoMEyK4/w800-h600-no/IMG_0060.JPG)
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geeeze that very much looks like Bud Lite Blue :-D
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geeeze that very much looks like Bud Lite Blue :-D
TFA official "beer-like cold beverage" just happens to be Bud Light...
(also we liked the Viper Blue of rex Svoboda's Saab)
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Oh, I'm with you now Karl. :roll: This is the ex Montana tank we'd talked about before.
Did you slow the steering down?
Sid.
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Oh, I'm with you now Karl. :roll: This is the ex Montana tank we'd talked about before.
Did you slow the steering down?
Sid.
Yup, its the Montana one and i gotta say a big thanks for your advice as we finally selected that car.
The steering should be slowed with a bit longer arms, but i haven't measured it yet (on my list)
karl
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Might be easier to redrill the pitman arm if it has a box, (sorry can't remember) just make sure it can't over center.
I'll come look you up at the salt, I wanna see this little gem in person.
Sid.
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Might be easier to redrill the pitman arm if it has a box, (sorry can't remember) just make sure it can't over center.
I'll come look you up at the salt, I wanna see this little gem in person.
Sid.
Sid
I'd love to yak with you in our pits, get yr thoughts on our efforts. You know how ignorant i am of car stuff but i am inching up the slope, lil by little. "All" i want this year is to plant my foot on the gas all the way thru 3rd gear with some degree of confidence. :-D
karl
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it's a lot more fun when you fear to plant but try to anyway
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I bought a pair of 12" Alignment Plates from Gil Smith Racing Fabrication and they did the job of measuring my steering ratio.
I had a couple cam degreeing wheels laying around from my bike motor building days which fortunately fit nicely on the turntable of the Plates
Like so many things, there are tricks to getting consistent info and i learned each trick the hard way.
Bottom line is my steering ratio is very close to 25:1
karl