Weight distribution?

[bharmon77]

I am building a 130" w.b. lakester, front engine, rear wheel drive. Can someone advise a target or most desirable weight distribution? The total weight of the car will be around 1300lbs.

[Stainless1]

That is a little shorter than ours, but with the driver on board our fronts are roughly 350-375 lbs each and our rears are 425-450 lbs.  We have several drivers (ballast configurations), they are the variable.
While building, you may want to build in options for non-driver ballast.  Weight is your friend at times...   

[bharmon77]

Stainless1,

Thank you for your reply it helps alot coming from a record holder with a similar car. I am not sure about my total weight it may end up around 1500lbs? The car is now off of the chassis jig and I can get some scales under it and have a better idea of where I am at with the total and the distribution. I will add weight to compensate and move things around fore and aft.

Thanks again,
Bruce Harmon

[Sumner]

Stainless1,

Thank you for your reply it helps alot coming from a record holder with a similar car. I am not sure about my total weight it may end up around 1500lbs? The car is now off of the chassis jig and I can get some scales under it and have a better idea of where I am at with the total and the distribution. I will add weight to compensate and move things around fore and aft.

Thanks again,
Bruce Harmon

As you probably know, where your center of gravity and center of pressure is on the car is also going to play into how it handles. 

Stainless do you guys know where the CG and CP is on your car and if so would you be willing to share that??

Bruce if you changed your name around a little by adding a "d" after the "r" and changing the "o" to an "a" you would be Hardman and already have a bunch of lakester records in the book  , but since Stainless is going after some of those you had better hurry  .

c ya,

Sum

[hitz]

  bharmon77, stainless and Sum,

  Apparently, my lakester will be the porker of this group at 1900 to 2000 #.

  There is a rumor that Jack C will have a small engine lakester running soon. This may change a lot of records!

Harvey

[Sumner]

  bharmon77, stainless and Sum,

  Apparently, my lakester will be the porker of this group at 1900 to 2000 #.

  There is a rumor that Jack C will have a small engine lakester running soon. This may change a lot of records!

Harvey

Mine might be up there with you weight wise and I have a smaller motor  .  Remember what they say though that weight is good, so maybe there will be some hope for us.

Jack is innovative, but I wouldn't count out the guys who already have records.  I think somewhere I heard that Jack is going 500cc -- K class to begin with, but don't take that to court,

Sum

[Stainless1]

Center of gravity is easy
Center of pressure, I'll leave that guess to the experts.... 

[Sumner]

Center of gravity is easy
Center of pressure, I'll leave that guess to the experts.... 

Thanks, using your weight distribution I got the center of gravity about 2-3 inches further forward, but you probably used one of your lighter living ballasts to figure your CG 

I printed out the picture and added just a little to the tail where you cut it off in your picture.  Then I transferred it to a piece of cardboard like people talk about and then balanced that and got the Center of Pressure a little ahead of the CG about where the "T" is in Automation (see yellow arrow).  Like Jack said this probably gets you close, but doesn't take into consideration a few factors.

Have you (meaning any of the drivers) ever spun the car??

Thanks again for the info,

Sum

[Speed Limit 1000]

Have you (meaning any of the drivers) ever spun the car??
[/quote]

Yes, I had quite a ride in about a 15 MPH cross wind at 220+ entering the "5" on a return record run. The main reason if the wind > 10 MPH we just stay in line. Stainless can tell you about his "spin" in the car. Two good reasons we have an electric chute button on the wheel so you only have to move a finger and your air-brake is open.

[tortoise]

Yes, I had quite a ride in about a 15 MPH cross wind at 220+ entering the "5" on a return record run.

Have you thought about adding a fin?

[landracing]

They ALWAYS had one, until stainless spin which if I remember correct blew the canopy off. They then went to the busa motor and redid part of the tail section.

Look at stainless picture (latest), then look at the one I posted (circa 2002), notice the change in width around the middle of the car for airbox design. That was changing from the Kawasaki Zx11 motors to the busa motor.

They have a new fin ready to go for this year if they decide to put it on...

Stainless or SpeedLimit1000 can give the timeline and direct facts on that.

Jon

[Stainless1]

The spins in the past have always been in the 200+ range.  We had a panhard arm suspension design that worked great until the car was above 200. then small changes caused a little "unintentional" (for Jacks memory) rear steering input.  The air suspension would feed that and the car would occasionally decide to make a left.  After about 5  of those, we figured it out.  Triangulated the rear 4 link and the front trailing arms.  Car has stayed controllable since then.  We are talking about putting the fin back on...  when we rebuilt to top, the fin was omitted, we may be putting one back on because every dart needs flights to go where you throw it...   

[Sumner]

It is none of my business, but I would put the fin/tail back on the car and think about maybe 100 lbs. more up front.  If the center of gravity is behind the center of pressure that doesn't mean you can't drive the car straight, but if something upsets the car, loosing traction, wind, or handling like you mentioned then the car is ready to spin.  In your case now it looks like the CP is slightly ahead of the CG or they are very close to one another and that can make a situation of something that likes to spin around that point.

In the new picture I'm posting I added a tail that looks to be a little larger than your old tail and put 100 more pounds over the front axle.  This moved the CP a fair ways behind the CG.  One other observation and take it for what it cost is that the sides of the car from the canopy down are pretty flat front to back, but from the canopy back the top half of the car is very rounded.  Nothing wrong with that, but it doesn't have as much effect in moving the CP rearwards, since it is so rounded.  The flat faced tail/fin will help a lot with the CP.  I also think even a small 4-6 inch high fin running down the top of the car from the canopy back would help to keep the car straight.  In effect it would be like an exaggerated "roof rail".

Not trying to butt into what you guys are doing, just making some observations that might or might not be correct  ,

Sum

[Speed Limit 1000]

Not trying to butt into what you guys are doing, just making some observations that might or might not be correct  ,

Sum
[/quote]

 Sum, thank you for the input. Jack, what do you think

[JackD]

Pretty close and certainly in the right direction.
Roof rails only spoil the lift over the top when the car is already sideways and reduce the tendency to lift.
While a fin sticking out the top adds to the surface area in the rear, the height makes it more sensitive to crosswinds with more of a tendency to roll.
Think about where you are adding the side pressure.
A flat extension to the rear of the body but not above will produce the desired surface area add but might mess up your exit air theory with the flat shape.
 Special construction LSR vehicles (cars and bikes) have not been perfected yet.

"Professional only means you charge for your time, it doesn't mean you are any good at it." (me)