WEIGHT A MINUTE

[roadsterswap]

I need some help and ideas from others with experience. I am running B/Alt coupe #532. It is a 1932 Ford 3 window coupe. You can see it running backwards through the course with my son driving on the scta website. My questions is.......Where to weight the car. On the scales the car is  approx 51% in the front. On the course the front end feels light. My thoughts and others are to weight the front end. Others say the rear. I would like to hear your thoughts and comments. I would like to hear from someone running a short wheelbase barn door like mine and what has worked for them. I have about 13 degrees of caster and 1/8 inch toe in. Tracks very well. Just seems to want to float. It takes allot of finesse to get it down the track OK. It has a rigid rear suspension and a sprung front end.
One other thing. Should I suspend the rear end? I have coil over set up with 250 Lb springs. Available. Currently I run it rigid.

The scales read the following:
LF 716
RF 689
LR 692
RR 706

left  1408    50.2%
rear  1398   49.9%
Cross  1301  49.3%

This is my rookie year. I want to learn from others. The learning curve is brutal. The 1-2 runs per month make it hard to dial in a car. I just think I should not have to drive it so much. Or am i wrong? Any help or ideas are appreciated.

Thanks.

[Sumner]

I have no experience at all with a car like this, but I guess that won't stop me from giving you something to think about.

Short wheelbase, center of gravity and center of pressure probably about in the same place is going to be hard and is why more of these cars spin than all the rest combined.  Since is is going to want to spin once it starts you need to concentrate on trying to stop that process from starting.

Anything that upsets the balance of the car will start it around (think about a car on ice/snow or a washboard road).

Personally I would put suspension on the back that is fairly soft with a lot of dampening in it.  Anytime the wheels don't hook, small bumps, they will spin and could cause the car to be upset and spin.

It looks like the rules allow a rear spoiler.  If this is so and you don't have one (I didn't see the picture of the car) I would put one on with the largest side spill plates the rules allow.  This will improve the center of pressure.

Anything you can move forward weight wise will help with moving the center of gravity forward.  This will lighten the rear and make it more susceptible to wheel spin (one of the things that will upset the car and start a spin) so hopefully the softer suspension will allow the car to hook to the track better and avoid wheel spin.

The driver needs to try and do anything possible to avoid upsetting the car.  A lot of these cars spin at the ends of runs as the driver backs off the gas there is sever compression braking, the back breaks loose and come around.  Get off the gas easy and on the brakes easy.  You just need to control the throttle like you would on ice/snow.

Hope this helps a little and hopefully you will get some better advice than this from some of the guys who have these cars.

c ya, Sum

[Rex Schimmer]

I think that Sum hit it on the head, you need more front weight and if a rear spoiler is legal make sure that it has BIG side plates. You want your car to be like a dart, weight in the front big aero area in the back. CG in front of the CP.

I did look a your picture at the June meet and was thinking that it must have been a hell of a ride!

Rex

[fastesthonda_jim]

I run a liner, not a roadster, and have a full belly pan, so I'm not sure I will be of any help here.  

Currently I run solid front and rear, no suspension anywhere.  But my theory about suspension (for the ever present "next car") is to NEVER spring the front.  I don't want anything at all that will tend to make the front rise under any circumstance.  I will probably put 1 maybe 1.5 inches of travel in the back just to compensate for some of the bumps out there and to help the tires hook up.

Your basic problem as I see it, is that you put a big flat plate (the radiator) out there and then push it from the rear hoping the push doesn't get off center.  Sort of like a trailer jack knifing if you don't keep everything lined up.  The trailer pushes the truck around just like your rear axle pushes the radiator around.  Combined that with a trunk lid that says nothing but lift and you have a dicey situation at best.

Don't know what the rules say about it, but I've heard of guys actually deploying a small chute for the whole run just to keep everything lined up.

Anyway, good luck.

Jim

[Sumner]

 But my theory about suspension (for the ever present "next car") is to NEVER spring the front.  I don't want anything at all that will tend to make the front rise under any circumstance.  I will probably put 1 maybe 1.5 inches of travel in the back just to compensate for some of the bumps out there and to help the tires hook up.
Jim

Hi Jim, I have to maybe disagree with you on the front suspension .  My older jeep with the leaf springs/solid axle in the front is for all practical purposes similar to a car with no suspension in the front.  If I'm going very fast and hit a hole the front about or does come off the ground (ask my wife ), since the suspension bottoms out almost immediately. If I hit the same hole in something with independent front suspension the suspension absorbs the hit and the vehicle doesn't rise.

I think having suspension travel for compression is a good thing. If done right the car should stay level with the ground and only the wheels should go up and down.  Limit the rebound and you won't have lift.  I'm setting mine up with about 1 1/4 to 1 1/2 travel on the compression and only 1/2 inch on rebound (with suspension limiters).  I'll be running "good -- expensive" 50/50 shocks with quite a bit of dampening, but soft (by B'ville standards) springs.

For very fast cars, like the speeds you are approaching, suspension might not have time to react, so all of this might become mute.  Personally I feel (gut feeling) that for cars under 275 suspension can have benifits if designed right (look at how Keith was able to set a 250??mph record last year on a bad track).  

   

Since I don't know what "right" is at this point I've designed a lot of adjust-ability into my suspension right now and will be able to vary the spring and shock rates with one set of springs and shocks.

Keep us informed how your changes work out.  You've gone lots faster than I have (zero for me at this point), so I respect your ideas and thoughts on the subject.  Now should we discuss which are better cars, Ford or Chevy, oops I forgot you are a Honda guy .

c ya in August,

Sum

[fastesthonda_jim]

Sumner,

First of all, Chevy as I have a Pro-Street 55 shoebox.  As to suspension, it all encourages the front of the car to come up even with stops.  I mean just see how far you can lift the front of your car with the springs helping vs how far you can lift the front of a non-sprung vehicle.

The clearance between the ground and the underside of the car is important and in some instances critical for my long term health so I prefer to set it and not have to think about it.  And no suspension means one less thing to break or to think about, i.e., KISS.

Now I have built cars in another venue that had teeter toter rear suspension with the two rear wheels in line, so that a 1" deflection in either wheel would result in only 1/2" of body movement, and it worked out okay.  But speeds were max about 45mph so we're talking different games here.

Anyway, I still wouldn't spring the front of any car that would go over 150mph.  It's just too risky in my book.  And let's not talk about Corvettes, Ferraris, Veyrons, etc.  They have smart people designing their stuff, not me.

Keep your shiny side up,

Jim

[Sumner]

Sumner,
 As to suspension, it all encourages the front of the car to come up even with stops.  I mean just see how far you can lift the front of your car with the springs helping vs how far you can lift the front of a non-sprung vehicle.
Jim

 Good points Jim and a good garage discussion.  On my car if you lift the front 1/2 inch you would be on the stops and then it would be like lifting a "no suspension" car.  Our street cars don't have stops built into them.

One other thing is we are comparing very different types of cars here.  If I was designing a streamliner and had it sitting on the ground I wouldn't put suspension on it.  My lakester has been designed so it has about 6 inches of ground clearance at the lowest point, so suspension travel is no problem.  I have limited the lifting possible to 1/2 inch (for the reasons you stated), so I think we are on the same page there.

c ya on the salt,

Sum

[fastesthonda_jim]

Off we go on another possible thread, Sumner.  You mention lakester and "up in the air".  I have been searching for a few years for the (a?) definitive answer on what is the optimum cross section for a liner.  Now Jack Costella has done quite well with cars that have probably less than 1" or ground clearance.  But the really top dogs, Nish, Burkland, Vesco, White, Teague all have their cars up in the air some like your lakester.

My belief is it's important to "bleed" the boundary layer off rather than have it build to compression at some point under the car.  Therefore it would seem that a rounded bottom, even a pointed boat shaped bottom might be the best.  

Additionally there is the subject of cross winds and the need to be aerodynamic cross wind wise, if you will.  It would seem that a Nish type cross section with highly rounded sides would be the least reactive to the winds.

But then I've seen the videos of Nish's airborne maneuver, and it wasn't pretty either, so I'm still rather lost about the whole thing.  I find from experience that my square car has been rock stable in all but the most heavy crosswinds, literally being a "one hander" even in the plowed field that El Mirage became in the final few runs in June.

So who knows?  

Anyways likewise; see ya' on the salt.

Jim

[Sumner]

Off we go on another possible thread, Sumner.  You mention lakester and "up in the air".  I have been searching for a few years for the (a?) definitive answer on what is the optimum cross section for a liner.  Now Jack Costella has done quite well with cars that have probably less than 1" or ground clearance.  But the really top dogs, Nish, Burkland, Vesco, White, Teague all have their cars up in the air some like your lakester.

A number of years ago when I first though about building a car Jack convinced me to build the car with suspension.  Of course those were the years in the 90's when the track was really getting bad and Jack couldn't always run, since his head was getting beat around so much he lost vision.  Now someone has told me Jack would try and talk me out of suspension and his recent car (5050) has reinforced that.  I would love to see what he is doing with the lakester he is suppose to be building.  I'm betting it will break with all current tradition .  Haven't had a chance to talk to him about that.  Sure wish he would post on here as he is a wealth of information.  Except for last year the salt has been pretty smooth and suspension/no suspension has been pretty much a non-issue.  Unfortunately I believe if the BLM lets the current Potash operation continue, regardless of the salt put back, the salt will eventually deteriorate again and then there could be years like last year regardless.  After waiting all year to run and the expenses involved make me want to try and design a car that can run under as varied conditions as I can anticipate.

Additionally there is the subject of cross winds and the need to be aerodynamic cross wind wise, if you will.  It would seem that a Nish type cross section with highly rounded sides would be the least reactive to the winds.
But then I've seen the videos of Nish's airborne maneuver, and it wasn't pretty either, ......Jim

I'm finally going to get to your "definitive answer on what is the optimum cross section for a liner" comment.  If I wasn't running suspension I would want the car flat on the ground like Jack has done and what it looks like you have done (I don't have any pictures of your car ).  Keep the air out from under the car and just deal with what is going down the top and sides.  I would want the car to have rounded corners in the front and flat square  corners in the rear.  This would help keep the center of pressure at the back of the car even if both ends had about the same height.  Since the center of pressure is effected by the side view of the car you can look at the Cd of the side view.  Let's say the car is a perfect rectangular shape from the side with the height the same front to back.  Since the front would have more rounded corners it's Cd from the side would be lower than the back with it's flat sharp cornered sides, which would be worst case "like a brick/flat plate" with a high Cd.  So in this case the center of pressure would be rear of the center of the rectangle even though the side view would indicate that the center of pressure would be in the center of the rectangle.  Hope this makes some sense.  Also this is my feeling on the subject, based on my thoughts and also conversations with others.  I welcome any other views.

.........But then I've seen the videos of Nish's airborne maneuver, and it wasn't pretty either, ......Jim

I guess nothing is going to save your a** in every situation

Since I want to run suspension I'll have air going under the car and just can't get around that.  So after reading the "Leading Edge" and some other material it seem like the minimum height for a body to be above the ground and get away from the effects of bad aero from air going under the car is about 6 inches.  More is better, but with diminishing results.  The other thing that helps is to have the bottom curved (in cross section) to avoid air being trapped under the body as it can bleed away, and I'll do that.  So I agree with your...

My belief is it's important to "bleed" the boundary layer off rather than have it build to compression at some point under the car.  Therefore it would seem that a rounded bottom, even a pointed boat shaped bottom might be the best. ............

...............I find from experience that my square car has been rock stable in all but the most heavy crosswinds, literally being a "one hander" even in the plowed field that El Mirage became in the final few runs in June............

If it works, why change it then

.........So who knows?...........Jim

Not me ,

Sum

[jimmy six]

If your car (coupe) seems to "float" at speed, it's because it is. My coupe lifted at 150. Studebakers lift at 185. If you don't want to add a giant spoiler at the rear consider air ducts from under the car that exit behind the rear window. These will breakup the air which is causing the lift. I choose not to do them on mime and just took off the nitrous and won't drive it 150 any more.  If you need help with this, see me at the July meet in impounds on Sunday...J.D.
PS: they work

[fastesthonda_jim]

TWO Red Hats?  What's up with that?

[russ jensen]

: Have pics of crowere T and it appears to have side plates that  are on slots that slide on or close to salt  on sides of body;. with front pushing air off to either side. was this to keep any air  from getting under car?? good idea ?? was it a better idea than wide flat front to push air up & over??? getting more confused by the post.

[roadsterswap]

I have talked to many racers and they all seem to have a different opinion. The Art of lakes racing.....experience, trial and error.
I am going to try #400 lbs in the rear over the axle. Leave the suspension rigid and close off the grille shell.

I am trying to make as few of changes as possible and see what happens. The priority is the weight. If I can do nothing else for July I will have the weight in the car. We shall see what happens.

then again........i may add taller rear tires to get some rake... readjust the caster.............add a step pan..........a rear spoiler..........( You may be wondering when I had my head injury !!!??)

[Sumner]

I have talked to many racers and they all seem to have a different opinion. The Art of lakes racing.....experience, trial and error.
I am going to try #400 lbs in the rear over the axle. Leave the suspension rigid and close off the grille shell.

I am trying to make as few of changes as possible and see what happens. The priority is the weight. If I can do nothing else for July I will have the weight in the car. We shall see what happens.

then again........i may add taller rear tires to get some rake... readjust the caster.............add a step pan..........a rear spoiler..........( You may be wondering when I had my head injury !!!??)

It will be interesting to see how that works.  Not the way I would go as you could tell from my previous post.  It is a shame more guys with roadsters/coupes didn't respond to this post.

I would give Doug Robinson (BMR car) a call if you haven't already talked to him at HP Engineering (626) 440-0440.  He is also the coupe & sedan Chair.  His car has spun, but it has also set lots of records.

Please let us know how the changes worked,

Sum

[roadsterswap]

I have not limited the approach I am going to use. I am crunched for time. And the changes are pushing me. I was joking about the step pan and the spoiler. I thought I would change one thing at a time. I thought the weight first. The front grille block out I can do pretty quick.

But again I want to leave the car unchanged and change one thing at a time. I want to feel the effects of the weight on the car without any other changes. If it feels worst I will try something else. I may then just try the suspension in the rear.
 You know how it is. You have to change one thing at a time or you do not know what made the effect.

I talked to Ron Bennum and he was the straw that broke the camels back on the weighting of the car. I will try. I may bring the shocks. If the weight is ok, I may put on the shocks and see what happens. The other issue with the shocks is that if fully compressed or if the car spun and the rear moves a little i may have tire clearance issues. The last thing i want is the tires catching the body and then flipping the car on itself. So the rigid suspension gives me a little piece of mind.

So: More driving experience
Some weight
maybe shocks.
block out grille
run the 18" tires in the rear with 15s in front for rake adjustment

and go from there.

The problem I have been having is getting lead melted and made into ingots. I only have a few days left to do this. So it is a scramble.

If i cannot weight the car......worst case scenario i will try the taller tires for rake and check the caster to make sure I have not lost too much.

Or leave it alone and just drive the dang thing. I need seat time. I dont want to miss any driving time. I may go slow but I am still driving. If there is any problem we will abort the run. We will not push it through again.

That is the plan. We shall see how it goes next month. Thanks for all the help and yes I wish more coupe guys were on here talking about what worked for them. I like to hear all the ideas and then I do what I think will work or what my time and money will allow me to do.