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Author Topic: TFA Racing Lakester "tweak" diary  (Read 52758 times)
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entropy
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« Reply #60 on: September 16, 2014, 12:53:41 AM »

Just a thought regarding your front alignment. Are you running any toe in or toe out. Typically toe out can cause a certain amount of hunting also lots of caster is always good to go straight. I was helping Steve Nelson with his V4 Fuel Lakester at the meet and this car has a rear engine and drive, it is based upon a Albatross drop tank that has been lengthen, no rear vertical stabilizer, at best the CG and CP are probably at about the same place. We ran a best of 202.6 got the record over 200, (Red Hat for Steve!) and it runs absolutely straight, no wondering, Steve says he could easily drive it with one hand. He runs about 1/16 to 1/8 inch toe in. Admittedly toe in (or out) causes tire scrub which takes power but it can add stability.
Rex

Rex,
Thanks much for the thoughts.  Every suggestion is very much appreciated!
Our crew checked toe in at the track, and IIRC found it was a tiny bit "toe in", so they set toe-in to 1/8" as best as they could with tools available.  We will put the car on an alignment machine and check/adjust.
Also we will re-re-check scrub.
Karl
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Peter Jack
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« Reply #61 on: September 16, 2014, 01:17:38 AM »

Karl, you may want to check the toe in in the rear. If there's any toe out the car will definitely be squirrelly. I'm not sure what you have for a rear axle but toe can easily be set on a solid axle by bending, usually using heating and cooling. The other thing to make sure is that the toe is equal on both sides and not all on one side. The car has to run straight.

Pete
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entropy
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« Reply #62 on: September 16, 2014, 03:01:34 AM »

Karl, you may want to check the toe in in the rear. If there's any toe out the car will definitely be squirrelly. I'm not sure what you have for a rear axle but toe can easily be set on a solid axle by bending, usually using heating and cooling. The other thing to make sure is that the toe is equal on both sides and not all on one side. The car has to run straight.
Pete
Pete, thanks a million for the tip!
Rear toe was not on our list, now it is.
Karl
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Chaz
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« Reply #63 on: September 16, 2014, 09:34:30 PM »

Also , although you've probably done this, check the rear axle for being perfectly perpendicular to the car's centerline. Just a thought.
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entropy
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« Reply #64 on: September 17, 2014, 03:19:08 AM »

Also , although you've probably done this, check the rear axle for being perfectly perpendicular to the car's centerline. Just a thought.

Chuck,
Thanks for the thought.  I particularly appreciate you suggesting something that "you've probably done this". 
People tend NOT to suggest things that are basic, but what is basic to long-timers may be a revelation to noobs (like me).
I'm lucky to have a partner like Don, who has long experience with automotive issues, but he's also a salt noob.

Once i get our preliminary list of "set up stuff to check & driving tips related to handling", I may start a thread in the Technical Discussion section on those issues and get a wider audience.
karl
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« Reply #65 on: September 17, 2014, 08:35:47 AM »

Karl
If I recall your driveline doesn't have an over-running clutch . The advantage of the pull of the front wheels becomes a negative during deceleration when the car is pushing the front tires . A couple of brands of what drag boats call whirlaways or prop releases can be adapted for FrWD cars . These are available from Casale and a company in Texas who's name I've forgotten . Sprag clutches don't seem to work well in this application .

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« Reply #66 on: September 17, 2014, 10:13:26 AM »

John,
You are exactly right, our car does not have an over-running clutch. We have kicked around various ways of getting the car to free wheel during decel, but it wasn't a priority.  I suspect I wouldn't have gone into that slide at the 5 if we had one, but i sure as heck will be much more careful coming off WOT next time.

Thanks for the info
Karl
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Stan Back
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« Reply #67 on: September 17, 2014, 11:12:26 AM »

I'm thinking that when (probably not always if) the crankshaft stops going around suddenly for a variety of reasons, you may not have time to disengage it before it sends the car somewheres.
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Glen
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« Reply #68 on: September 17, 2014, 11:22:12 AM »

John and Stan are correct, you should really consider the upgrade. BTW, I like the car and I am sure you will have many years running it. Be safe and go fast. cheers
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« Reply #69 on: September 17, 2014, 01:18:03 PM »

Karl
Beaverfab is the one from Texas I couldn't think of . JJ the owner used to post here and I'm sure would be helpful . Beaverfab and Casale both come with a neutral position handle that is unneeded for our use .
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« Reply #70 on: September 18, 2014, 02:50:17 AM »

Karl
Beaverfab is the one from Texas I couldn't think of . JJ the owner used to post here and I'm sure would be helpful . Beaverfab and Casale both come with a neutral position handle that is unneeded for our use .
John, thanks much!
Karl
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« Reply #71 on: September 18, 2014, 03:28:28 AM »

Issue:
At the recent WOS, my Partner & I made a total of 8 passes and in all of them we both experienced the car hunting at speed to the point we momentarily got out of the throttle or were throttle-tentative.  
   Experts say that some degree of this type handling comes with the territory with FWD car on salt.  On my last pass I was WOT for all of 3rd gear except once and the car does indeed "fix itself".  Maybe we are not driving it right.
   Don & I are ex-motorcycle guys so maybe we are just being over sensitive, but in any event we'd like to minimze the jinking/hunting because it spooks me somewhat.  Besides... My MC experience taught me that getting out of the throttle at ANY point on the course costs mph (except as dictated by traction management)

Below is a hit list of issues to address; we'd like your comments.

#5448 handling issue - set up stuff to check/adjust:
1. Would adding 300# F ballast help stability? (gives 55/45%) Pros & cons
2. Re-determine our Cg-Cp relationship, basic vehicle info
3. Re-check L-R tire psi are equal; is F-R psi a factor?
4. Further minimize play in steering linkage, improve mounting of associated universal joints
5. Confirm scrub radius is close to zero, find a way to measure it more accurately
6. Other?
7. Put car on automotive alignment system:
- measure castor; lots of caster is always good to go straight (not adjustable)
- measure front toe in; set to ?1/8?", is it better to err on the side of more or less toe in?
- check the rear axle for being perfectly perpendicular to the car's centerline
- check the toe in in the rear, assure it is equal on both sides and not all on one side
- other?

I was torn between posting this here in TFA's thread or posting a new topic in the Technical Discussion section.  
It went here because I am such a noob with my A, B, C's-type questions and the issue is specific to TFA #5448.  
   Our Mentors are VERY well versed in this stuff & eager to talk about it, and my Partner Don has strong automotive & aircraft experience so why even put this question here?
   I am just learning and am looking for as wide exposure/comments as possible.  Sometimes two people can say the same thing differently, one way rings my bell, one way goes over my noob head.  Thanks for your help.
Karl
« Last Edit: September 18, 2014, 03:41:02 AM by entropy » Logged
RichFox
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« Reply #72 on: September 18, 2014, 08:41:13 AM »

Once again I am speaking out about something I know nothing about. But on your list i didn't see check front tires for roll out. On a rear drive car i found pressure equalization to be not important compared to diameter. Maybe it is important, I just didn't notice it. But diameter is for sure important, I think.
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« Reply #73 on: September 18, 2014, 09:10:39 AM »

.....
4. Further minimize play in steering linkage, improve mounting of associated universal joints
8. ...measure front toe in; set to ?1/8?", is it better to err on the side of more or less toe in?..

Definitely try and minimize any play and that also ties into 'toe in'.  It was always my understanding that the primary reason for 'toe in' is that steering and the other frontend components will always have some play (give).  Toe In helps to getting the wheels/tires going straight down the road once the car is underway and the slack/play/give goes out of all of the steering and other frontend components.  How much?  Probably depends on how much play there is in ever thing and all vehicles don't have the same combination of frontend parts..  I'd rather have a little to much toe so would start on the high side of what has been suggested.  With that said I think Hooley has the Stude setup with some 'Toe out'  (Hooley ??) and the car steers like it is on rails.


.....
5. Confirm scrub radius is close to zero, find a way to measure it more accurately..
7. ...measure castor; lots of caster is always good to go straight (not adjustable)

Don't forget that castor effects the scrub radius along with kingpin inclination and tire height.  The way that I've always understood it (someone correct me if wrong) is that it is the projected point on the ground that the tire pivots on.  More castor will move that point further forward resulting in the point being further from the cars center line.

I personally believe that unknowingly people have tried to fix, or over come, what was actually a 'scrub radius' problem (car hunting, darting around) by putting a lot of castor in the car.  If they would get the 'scrub radius' right there would be no need for all of the castor.  Just my opinion,

Sounds like you have a well though out plan and sure you will end up with a car that is easier and fun to drive,

Sum
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« Reply #74 on: September 18, 2014, 10:12:51 AM »

I agree with Rich on rollout.   More important than pressure. Set the largest tire to the pressure you want to run, than add more to the smaller one. We try for 1/2 inch difference. Less if we can get it. Sometimes we can be right on.

And always re check air at the starting line. The right side always gains from sunshine exposure.

Frank
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