Author Topic: Springfield Flyer.  (Read 1452632 times)

0 Members and 1 Guest are viewing this topic.

Offline Interested Observer

  • Sr. Member
  • ****
  • Posts: 433
Re: Springfield Flyer.
« Reply #2730 on: October 19, 2016, 07:44:29 PM »
In reviewing the Speed Demon crash cockpit video it is clear that it did not LEAN at all, it YAWED to the right with George feeding in left steer to counter the yaw.  Unclear what drove the yaw, but longitudinal aero instability seems highly likely, what with its refusal to answer the helm.  If it were stable it should have self-corrected or not departed in the first place.

Offline ggl205

  • Sr. Member
  • ****
  • Posts: 956
  • G/FL 218.282 since 1995. G/FL record since 1993.
Re: Springfield Flyer.
« Reply #2731 on: October 19, 2016, 09:37:46 PM »
It might be helpful to know where Speed Demon's front and rear roll centers are in relation to center of gravity. Also, is the suspension designed to be adjusted (not possible with solid mount axles) for roll center front and rear and if they decouple?

John

Offline Ron Gibson

  • Sr. Member
  • ****
  • Posts: 770
Re: Springfield Flyer.
« Reply #2732 on: October 20, 2016, 12:35:59 AM »
FWIW  When I watched the rear view camera, it looked to me that the rooster tail from the tires changed. To me that would indicate a tire going down which would cause yaw.
Just my opinion and it's worth what you paid for it but I have stayed at a Holiday Inn.

Ron
Life is an abrasive. Whether you get ground away or polished to a shine depends on what you are made of.

Offline Peter Jack

  • Hero Member
  • *****
  • Posts: 3776
Re: Springfield Flyer.
« Reply #2733 on: October 20, 2016, 01:50:15 AM »
I've spent a good portion of my life building, setting up and tuning race car chassis for both oval track and road course racing. I think what we learned from those disciplines has very little to do with what we're dealing with here. For those types of applications we're setting up the car with the intention of turning it and the chassis tuning we use is designed with that in mind.

In lsr we're in fact designing the car to go straight. I think at the speeds we're talking suspension has very little to do with what happens and aerodynamics almost totally determine what happens. This is providing that the alignment is correct and the suspension is stiff enough to support the car at speed. By the time the car is yawed far enough that roll couple has a significant effect I'm sure that aerodynamics are far more influential and the tires lack enough grip to offer any assistance.

Just a little more food for thought.

Pete

Offline ggl205

  • Sr. Member
  • ****
  • Posts: 956
  • G/FL 218.282 since 1995. G/FL record since 1993.
Re: Springfield Flyer.
« Reply #2734 on: October 20, 2016, 10:48:41 AM »
Pete:

I think there are some takeaways here with regard to road racing setups. If roll induced by torque is unwanted, then placing roll center (RC) above center of gravity (CG) will negate or reduce roll. My brief nine years in LSR has taught me that chassis tuning can help with handling and grip the same way it did in road racing only to a lesser degree. The same physics apply to both venues. A modern Formula car, even those down at the club level, have greatly reduced suspension travel along with greatly reduced roll. My old Lola T580 FC car was designed to roll in order to keep camber and toe in check. Today's formula cars have very long upper and lower wishbones to further reduce changes in arc and they do not handle roll very well. like an LSR car, they limit suspension travel via high spring rates, employ bell cranks to increase motion ratio and dampers to control springs responding to track surface irregularities. I see a great deal of parallel to LSR here.

John


Offline SPARKY

  • Global Moderator
  • Hero Member
  • ***
  • Posts: 6908
Re: Springfield Flyer.
« Reply #2735 on: October 20, 2016, 02:59:35 PM »
The W A in me could not resist---the parallel relationship--well almost parallel--- that that I am most interested in---oh not that---this---the bottom of my car and the racing surface  :-D
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 Peter Jack

  • Hero Member
  • *****
  • Posts: 3776
Re: Springfield Flyer.
« Reply #2736 on: October 20, 2016, 03:28:38 PM »
Pete:

I think there are some takeaways here with regard to road racing setups. If roll induced by torque is unwanted, then placing roll center (RC) above center of gravity (CG) will negate or reduce roll. My brief nine years in LSR has taught me that chassis tuning can help with handling and grip the same way it did in road racing only to a lesser degree. The same physics apply to both venues. A modern Formula car, even those down at the club level, have greatly reduced suspension travel along with greatly reduced roll. My old Lola T580 FC car was designed to roll in order to keep camber and toe in check. Today's formula cars have very long upper and lower wishbones to further reduce changes in arc and they do not handle roll very well. like an LSR car, they limit suspension travel via high spring rates, employ bell cranks to increase motion ratio and dampers to control springs responding to track surface irregularities. I see a great deal of parallel to LSR here.

John



John:

I think we may have to compromise a little here or agree to disagree which is alright too.

There are a couple of things involved with the long skinny cars that don't necessarily apply to the shorter, wider cars, which may even include lakesters. The first is that in the case of streamliners with two of the wheels virtually in line with one another there is no roll resistance at that end so it won't resist the roll at the end with the wheels on either side. The other thing to consider is with the very narrow track and a very long chassis that isn't necessarily designed to be the ultimate in torsional rigidity I have my doubts whether a roll couple calculation is very effective. I think the more important area to consider beyond aero is spring rate and damping. While I'm not a fan of total rigidity I think urethane with its properties of elasticity and self damping may be an answer.

In all cases, proper geometry and alignment is mandatory.

Again, I'm submitting this as food for thought rather than cold hard fact.

Pete

Offline Peter Jack

  • Hero Member
  • *****
  • Posts: 3776
Re: Springfield Flyer.
« Reply #2737 on: October 20, 2016, 03:35:18 PM »
The W A in me could not resist---the parallel relationship--well almost parallel--- that that I am most interested in---oh not that---this---the bottom of my car and the racing surface  :-D

Sparky, without knowing the shape of the bottom of your car and the relationship it has with the ground, it's hard to even offer a wild a$$ed guess. The only thing I can offer is that I want to see at least some forward rake in a car at all times. Blow overs are never pretty.

Pete

Offline ggl205

  • Sr. Member
  • ****
  • Posts: 956
  • G/FL 218.282 since 1995. G/FL record since 1993.
Re: Springfield Flyer.
« Reply #2738 on: October 20, 2016, 06:06:30 PM »
Pete:

We are on the same page here. We simply view these problems through differing levels of importance. I love the discussion even if it goes nowhere.

It is true, I think mostly in terms of lakesters these days and I fully agree that these narrow front track cars (slight offset to one another. We do not want to make sidecars out of them) have their own issues to deal with. Roll is likely not one of them. Rear suspension could still remain a problem if RC is too far below or above CG. I may fire up WinGeo3 and run a few simulations.

I like the idea of using urethane in suspensions. Didn't the Shadow F5000/CanAm car do something similar? It did not work well but those guys were thinking. We used to put urethane doughnuts of varying densities (very light densities) on our dampers to assist in full compression dampening. Probably could have done the same thing with valving but didn't have trackside ability to change these things back in the 70's.

John
« Last Edit: October 21, 2016, 09:42:12 AM by ggl205 »

Offline Rex Schimmer

  • Hero Member
  • *****
  • Posts: 2625
  • Only time and money prevent completion!
Re: Springfield Flyer.
« Reply #2739 on: October 22, 2016, 02:02:57 PM »
The Shadow guys actually used die springs which look like valve springs on steroids! Another thought would be belville washers which are spring steel washers formed in a shallow cone shape. They can be used in parallel or series mounting and they have a pretty high rate of kinetic dampening when they are compressed so you may not need a shock.

Rex
Rex

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

Offline kiwi belly tank

  • Hero Member
  • *****
  • Posts: 3132
Re: Springfield Flyer.
« Reply #2740 on: October 22, 2016, 04:43:20 PM »
When we stretched the Herbert-Steen liner for the 7 speed B&J's & gave it a little suspension, it was stacked Belleville washers with no shocks.
  Sid

Offline ggl205

  • Sr. Member
  • ****
  • Posts: 956
  • G/FL 218.282 since 1995. G/FL record since 1993.
Re: Springfield Flyer.
« Reply #2741 on: October 22, 2016, 08:58:00 PM »
Sid, where is that liner now? Wasn't that car built in Twin Falls, Idaho?

John

Offline wobblywalrus

  • Hero Member
  • *****
  • Posts: 5503
Re: Springfield Flyer.
« Reply #2742 on: October 23, 2016, 01:07:52 AM »
It is possible to change the damping rate from responsive to almost rigid using vehicle position sensors and computer control   Bikes have this sort of setup now.  It is a lot like electronic fuel injection.  The only limits are the ability to program the computers. 

Offline tauruck

  • Hero Member
  • *****
  • Posts: 5126
Re: Springfield Flyer.
« Reply #2743 on: October 23, 2016, 07:31:36 AM »
I'm more confused than ever now!. I'm going to change the whole rear end and add shocks and the "mother of all roll bars".
We'll see how that works out.
Guys, I'm exhausted. Trying to build a liner in Africa without a budget and an exchange rate that defies description isn't a joke
and I'm not looking for sympathy but all this S$$t is too confusing.
Truth is that I've been in situations far worse but I'm not going to go all "Health and Safety" on this. If it doesn't work and I stop posting so
be it.
My tranny is junk for starters so if i ever get tires the thing will probably break before it gets to a speed where it will be dangerous!.

Offline kiwi belly tank

  • Hero Member
  • *****
  • Posts: 3132
Re: Springfield Flyer.
« Reply #2744 on: October 23, 2016, 10:39:28 AM »
Sid, where is that liner now? Wasn't that car built in Twin Falls, Idaho?

John

Yep, just up the road from me in Idaho Falls & it's still there in the shop. With both Chet Herbert & Roy Steen gone now & Clayton Steen now running the business alone, it is unlikely Big Bertha will ever run again.
  Sid.