Author Topic: TFA Racing Lakester "tweak" diary  (Read 98009 times)

0 Members and 1 Guest are viewing this topic.

Offline entropy

  • Sr. Member
  • ****
  • Posts: 731
Re: TFA Racing Lakester "tweak" diary
« Reply #120 on: September 21, 2014, 08:27:13 AM »
You mentioned a locked rear (front) end in the above post. Is it a spool or a locker or something else? At this point I might be tempted to follow one of Sparky's favourite suggestions and look at a true track type differential. They tend to have a softer action than some of the other locker types and give you a differential rather than a spool. Just another suggestion to add to the confusion.  :roll: :roll: :-D
Pete
Being a former m/c guy, I am easily confused about car parts, but i believe our front-rear end is called a "spool" with both wheels turning at the same speed. 
What is a "true track type differential" and how much do they cost :-D
Do you think that uneven traction with our spool could cause hunting and that a true track type differential could mitigate it?
I have "call Sparky" on my list but it seems that 2-6am is my only free time these days and few people enjoy being called at that time.
Karl

Offline SPARKY

  • Global Moderator
  • Hero Member
  • ***
  • Posts: 6908
Re: TFA Racing Lakester "tweak" diary
« Reply #121 on: September 21, 2014, 09:07:38 AM »
read about torsen-gleason diffs

there is a reason why LSR is called the thinking mans sport---there are SOOOOOOOOOOO many trade offs that have to be dealt with:
   so much to learn so little time  or as the old folks say  "old too soon -- smart too late"

 or we racers  " broke to soon --never fast enough"
Miss LIBERTY,  changing T.K.I.  to noise, dust, rust, BLUE HATS & hopefully not scrap!!

"Security is mostly a superstition. It does not exist in nature, nor do the children of men as a whole experience it. Avoiding danger is no safer in the long run than outright exposure. Life is either a daring adventure or nothing."   Helen Keller

We are going to explore the racing N words NITROUS & NITRO!

Offline Sumner

  • Global Moderator
  • Hero Member
  • ***
  • Posts: 4078
  • Blanding, Ut..a small dot in the middle of nowhere
    • http://purplesagetradingpost.com/sumner/sumnerindex.html
Re: TFA Racing Lakester "tweak" diary
« Reply #122 on: September 21, 2014, 10:14:17 AM »
....What is a "true track type differential" and how much do they cost :-D....

I don't think you are going to find a true-track/torsen for your quickchange but also think that at some point you will need to rethink the current quickchange and consider a Winters extremeliner qickchange with a taller pinion ratio or possibly another approach.  The frontwheel drive has lots of advantages but also needs to be really thought out well with an overall package approach that addresses gear selection, and overrunning clutch and spool or something like the torsen. 

One possible solution, don't know this for sure, would be go to a transmission like what we use in the Stude and what I bought for my lakester, G-Force 101A, where you can do your gear changes with the transmission and even run overdrive gears (also get a 1st and 2nd that is more useable). 

Sparky would know if you could setup a 7 1/2 like he uses with 2.14 or 2.28 gears and a torsen in a frontwheel drive axle.  That would be a lot less expensive if possible than other options like the few quckchange rears with tall pinion gears.  You don't need a clutch with the 101 to change gears so you might be able to replace it with the overrunning clutch from Beaverfab or Casale (check with them).

On the weight it should help overall traction and with the spool if one wheel is spinning the other is also and then the car wants to step out.  The torsen/true trac will try and stop the wheel with no traction from spinning and actually send some of the power that was going to that wheel to the one with traction.

I think that I might of run a spreadsheet at one time for you that showed the weight needed over the drive wheels for speeds in the high 200's where hopefully you are going.  They might of shown that eventually you might need even more than 400 lbs. more.  Let me know if I did or didn't do that and I could do it again or you could do it with the "HP needed for A Lakester or Car to Run a Certain MPH" spreadsheet here (and you said you like to run spreadsheets  :-))...

http://purplesagetradingpost.com/sumner/bvillecar/bville-spreadsheet-index.html

Sum

Sum

Offline Interested Observer

  • Sr. Member
  • ****
  • Posts: 433
Re: TFA Racing Lakester "tweak" diary
« Reply #123 on: September 21, 2014, 02:11:33 PM »
Quote
The torsen/true trac will try and stop the wheel with no traction from spinning and actually send some of the power that was going to that wheel to the one with traction.

....thereby exacerbating the directional “hunting” problem.

Offline Rex Schimmer

  • Hero Member
  • *****
  • Posts: 2625
  • Only time and money prevent completion!
Re: TFA Racing Lakester "tweak" diary
« Reply #124 on: September 21, 2014, 03:18:53 PM »
Your lift number may go away if you give the car a little "nose down" attitude. Lowering the front a little should increase front down force by reducing the front ground clearance and therefore increasing the speed of the air flow at that point which will lower the pressure and help eliminate some if not all of the lift you are seeing. I don't know how fast the wind tunnel velocity but remember that lift is a power of 2 function so if your tunnel speed was 100 mph and you had 239 lbs of lift at 200 that would be about 960 lbs of lift. Or is you lift number calculated for 200mph?

Rex
Rex

Not much matters and the rest doesn't matter at all.

Offline SPARKY

  • Global Moderator
  • Hero Member
  • ***
  • Posts: 6908
Re: TFA Racing Lakester "tweak" diary
« Reply #125 on: September 21, 2014, 06:00:24 PM »
thereby exacerbating the directional “hunting” problem.

What it does is maximize forward thrust while keeping the wheels turning the same speed!  might happen but there must be a reason why most fwd manfactures's use them
Miss LIBERTY,  changing T.K.I.  to noise, dust, rust, BLUE HATS & hopefully not scrap!!

"Security is mostly a superstition. It does not exist in nature, nor do the children of men as a whole experience it. Avoiding danger is no safer in the long run than outright exposure. Life is either a daring adventure or nothing."   Helen Keller

We are going to explore the racing N words NITROUS & NITRO!

Offline NathanStewart

  • Hero Member
  • *****
  • Posts: 1241
Re: TFA Racing Lakester "tweak" diary
« Reply #126 on: September 21, 2014, 06:20:06 PM »
On the weight it should help overall traction and with the spool if one wheel is spinning the other is also and then the car wants to step out.  The torsen/true trac will try and stop the wheel with no traction from spinning and actually send some of the power that was going to that wheel to the one with traction.

I wandered into this thread to see what's going on and I'm interested to see that someone else is also going to some trial and tribulation with a newer car.  We too (myself and Skip Pipes) have been spending more time trying to get the car situated than making high speed passes.  The roadster has all the right things going for it... well constructed, highly adjustable suspension, long wheelbase (for a roadster), good weight and weight placement and yet the car didn't really like to go straight.  

I quoted the above because we started with a torsen and have since taken it out.  It just simply did not work correctly and we don't really know why.  What's strange is that it's worked well for others but was disastrous for us.  Since day one, the car would quickly pull to the right at the top of any one gear where the engine is really starting to make a lot of power.  We made a short list of possible things that could attribute to the problem and the torsen was the last item as it really wasn't believable that it'd be the problem.  We replaced all the Speedway heims on the car with FK heims as some of the Speedway pieces had developed a click to them.  We ditched the tape measure alignment job and took the car to an alignment shop.  We put the tires that the car was originally built for on and re-adjusted the suspension (had started out with shorter rear tires which made the car too low and required lifting the suspension to get the right ride height).  We added a steering stabilizer/damper. We dialed in more caster.  We did all the right things that should have made the car happy but the torsen was still acting up.  On a test run, everything was going great and the car was going straighter than it ever had and then bam, the torsen wigged out and bad things happened.  Basically, what we think was happening was that the torsen was torque biasing for no real reason and sending all the power to left wheel and the car would "rear steer" off to the right.  

Well we finally saw the light and took the torsen out.  Tested again and viola, no pull to the right at the top of second gear.  I used to not be able to rev past 7k in second gear and now I can go 8k+ without the car turning.  The only problem now is that the car drives like an open diff car which is to say that the car basically wanders down the course.  We ran at El Mirage last weekend and had mixed results.  I only managed two 160 passes when the plan was 160, 180 then 200.  On the last pass the inertia switch popped.  I find that I'm doing more conservative recovery driving and less aggressive WOT fast driving.  I've always driven an open diff roadster at El Mirage and I know that rarely does an open diff roadster ride like it's "on rails" or go perfectly straight - it just ain't so.  The biggest diff (no pun intended) between Skips roadster and the Stewart Family roadster is the new roadster makes about 5 times more horsepower than our old one so the days of holding it wide open and pointing down course are long gone.  

Anyways, long story long, I totally understand and feel you on the getting uncomfortable real fast when a car gets twitchy.  It's always better to back out of it and ease back in versus staying in it and trying to "drive through it" because that's when bad things happen.  Rule #1 is listen to your gut.  If your gut says lift, then lift.  As for us, we've got a few other small things to try including adding in a little weight.  We're at 3000 lbs wet with a 45/55 front/rear distribution and nearly even from left to right.  The other thing working against us was the course wasn't very good - not terrible and not great, just not very good.  When the car went from far left of course to the middle and then from the middle to the far right, I kind of just lightly suggested that we think about going to the left some with the steering wheeo.  It shouldn't ever be a white knuckle, fist over fist kind of deal - just gently guide the car using small steering inputs with your finger tips.  Anything more than that and there's probably something wrong.  
El Mirage 200 MPH Club Member

Offline Sumner

  • Global Moderator
  • Hero Member
  • ***
  • Posts: 4078
  • Blanding, Ut..a small dot in the middle of nowhere
    • http://purplesagetradingpost.com/sumner/sumnerindex.html
Re: TFA Racing Lakester "tweak" diary
« Reply #127 on: September 21, 2014, 06:51:00 PM »
Nate is it possible that something was wrong with the torsen?  Sparky ran straight over 300 with one,

Sum

Offline NathanStewart

  • Hero Member
  • *****
  • Posts: 1241
Re: TFA Racing Lakester "tweak" diary
« Reply #128 on: September 21, 2014, 06:53:38 PM »
Nate is it possible that something was wrong with the torsen?  Sparky ran straight over 300 with one,

Sum

I think Skip was largely influenced to use the torsen by Sparky's success with his but I think the differences between a long narrow lakester and a no so long and wide roadster erase any amount of "well it worked for them so it should work for us too" thinking.  How wide was the tread width on the lakester?  I know it's probably no where near as wide as the roadster.  If there had been a torque induced rear steering action, would it be as noticeable or noticeable at all on a long wheelbase car with a narrow rear end?  Another possible issue is that the axles aren't the same length.  The center housing is way offset to the right and the right axle is probably half as long as the left.  Perhaps there was axle wind up?  Is that even possible?  A torsen is a simple device - I don't know how there could have been something "wrong" with it.  All I do know is that at about 750 ft-lb of torque, the rear end was doing more steering than the front.  And it wasn't the rear end slipping and coming around.  It was the rear end making the car turn right like someone was grabbing the steering wheel and yanking it to the right.  Not fun to drive.  Much better without it.    
« Last Edit: September 21, 2014, 07:04:41 PM by NathanStewart »
El Mirage 200 MPH Club Member

Online John Burk

  • Sr. Member
  • ****
  • Posts: 695
Re: TFA Racing Lakester "tweak" diary
« Reply #129 on: September 21, 2014, 08:20:54 PM »
It would be interesting to see how a roadster handled with independent or dedion rear suspension handled .

Offline jdincau

  • Hero Member
  • *****
  • Posts: 1047
Re: TFA Racing Lakester "tweak" diary
« Reply #130 on: September 21, 2014, 08:31:33 PM »
Ask Rich Fox his has a swing axle.
Unless it's crazy, ambitious and delusional, it's not worth our time!

Offline RichFox

  • Hero Member
  • *****
  • Posts: 2663
Re: TFA Racing Lakester "tweak" diary
« Reply #131 on: September 21, 2014, 08:51:11 PM »
You would really have to ask Al Hollaway. He ran it in what is now E/BFR and went 219. Spun a few times but I think that was on shut down. Running with four cylinder engines the car has only gone 142 out the end. Handles fine at those speeds. I believe the Markley-Hoffman 360 roadster has a Corvette type rear end. Maybe they can answer your question. Lately I have been leaning more toward solid mounting. 

Offline Sumner

  • Global Moderator
  • Hero Member
  • ***
  • Posts: 4078
  • Blanding, Ut..a small dot in the middle of nowhere
    • http://purplesagetradingpost.com/sumner/sumnerindex.html
Re: TFA Racing Lakester "tweak" diary
« Reply #132 on: September 21, 2014, 08:57:27 PM »
....I think Skip was largely influenced to use the torsen by Sparky's success with his but I think the differences between a long narrow lakester and a no so long and wide roadster erase any amount of "well it worked for them so it should work for us too" thinking.  How wide was the tread width on the lakester?  I know it's probably no where near as wide as the roadster.  If there had been a torque induced rear steering action, would it be as noticeable or noticeable at all on a long wheelbase car with a narrow rear end?  Another possible issue is that the axles aren't the same length.  The center housing is way offset to the right and the right axle is probably half as long as the left.  Perhaps there was axle wind up?  Is that even possible?  A torsen is a simple device - I don't know how there could have been something "wrong" with it.  All I do know is that at about 750 ft-lb of torque, the rear end was doing more steering than the front.  And it wasn't the rear end slipping and coming around.  It was the rear end making the car turn right like someone was grabbing the steering wheel and yanking it to the right.  Not fun to drive.  Much better without it.    

Thanks for the additional info :-).  

Sparky is running one in the new car with the widest width he could find, I think Camaro, and he seemed to be fine on his test-n-tune runs in July but I think the fastest before the meet closed was 230 maybe and no where near full power.  I'd think his old car, and new, made probably the torque you guys are, but he would have to clarify that.  He needs to come up with different mounts for the wide one so think if he runs WF/SW it will be with an older axle that is a little narrower.

With so many differences in the way cars are setup I guess this is another "what works in one car might not work in another",

Sum

Offline SPARKY

  • Global Moderator
  • Hero Member
  • ***
  • Posts: 6908
Re: TFA Racing Lakester "tweak" diary
« Reply #133 on: September 21, 2014, 09:02:04 PM »
Nate,  Thanks for sharing the new ride's "sort out" 

If the right wheel was unloading it would transfer more torque to the left and hence more thrust or drive.  I run solid and preload the right wheel with a SWAG of how much the pinion is trying to lift the right wheel---hence I start off with more weight on the rr and the lf..  I have about 150# of preload so transfering 75# make them even.  I have had suspension  and even my low time driving skills I could tell things were changing going down track----

If I were going to try to get a roadster down the track it would be with out suspension or scrub radius  and 3-5 degrees of caster

---I am not any kind of engineer but it just makes for less variables in my mind.
« Last Edit: September 21, 2014, 09:15:30 PM by SPARKY »
Miss LIBERTY,  changing T.K.I.  to noise, dust, rust, BLUE HATS & hopefully not scrap!!

"Security is mostly a superstition. It does not exist in nature, nor do the children of men as a whole experience it. Avoiding danger is no safer in the long run than outright exposure. Life is either a daring adventure or nothing."   Helen Keller

We are going to explore the racing N words NITROUS & NITRO!

Offline entropy

  • Sr. Member
  • ****
  • Posts: 731
Re: TFA Racing Lakester "tweak" diary
« Reply #134 on: September 22, 2014, 09:44:40 AM »
Thanks to everyone for yesterday/last night input!!!!
This thread is really helping me appreciate salt handling factors and driving technique. 

But particular thanks to Nathan Stewart for taking the time to review his trials & tribulations; that post 110% rang my bell.
It takes me a while to digest/save this stuff, none of it is taken casually.  Specific questions will come and I really appreciate you guys continuing to patiently nudge me up the learing curve.
Once again i am reminded that I need to start wandering around the pits and talk to people at the events like my Partner does. Running a car on the salt is assuredly WAY more complex than the point & shoot impression I had previously.
karl