Author Topic: Ballast Question  (Read 10722 times)

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Offline Sumner

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Ballast Question
« on: December 21, 2004, 01:49:00 PM »
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 We would like to hear some opinions from you car guys on Hooley's car that we ran last year.  Due to oiling problems we only got to make four runs on the car, so Hooley (driver/owner/builder) didn't get a lot of seat time to really feel the car out.
 
 He made three licensing passes of 127, 173 and 191.  The first two passes he said were a piece of cake.  On the 191 run he felt the car move aroung a little, but didn't really have to correct at all.  On the second and 3rd passes we lost oil pressure at the end of the runs due to the fact we were pumping it all up top and it was returning fast enough.  Hopefully we have that problem fixed for next year.
 
 Because of the oiling problem we decided on the 4th run (on the long course) to just run through the 3rd mile and shut it off.  He ran a 198 in the first 1/4 of the third mile and averaged 207.485 for the whole 3rd mile and I figure his exit speed was about 218-219.  Again on this run the car hunted a little, but didn't really require any steering input to keep it straight.  Hooley did say that something seemed a little strange in the back, maybe like it was getting a little light.  The problem was he was at speed for such a short period of time and this was the first time he ever went this fast so a lot was going on for him to take it all in.  If we wouldn't of had the oiling problem and could of run through the 4th and 5th miles I think we would know more.
 
 First some facts.  The car with driver scales at only 2800 lbs. (pretty close to 50/50)and we see so many people adding ballast to their cars and wonder if we should, or if we only should if we run into a problem?
 
 The car didn't have a belly pan, but he is now installing one and almost done.  We don't know if this could make matters worst, better, or stay the same.
 
 He has ladder bars and coilovers in the back.  We are adding chains to the rear axle to limit how much the body can lift before it also has to lift the axle.  Good idea or bad idea?  Our feeling is that the coilovers are pushing up on the body and providing assistance to the air, which might also be creating a lifting effect to the body.  
   -  
 I put this picture in to kind of give you an idea of the car and how it sits from the side view for comparison to the rake of the car in the next picture.  
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 This is about the only picture we have of the car at speed except for some video that isn't that good.  To me it looks like the car is lifting some in the rear in comparison to the picture before this one.  We belive this picture was taken on the 2nd run and the car was running about 175 if that was the case.  Also if that was the case we still had our big 28 inch tires on the front at that point and our small 24 inch tires on the back, which should have made the back lower yet.    
 
   -
 
 Here is a picture of the back spoiler.  We have it raised a little and it has some adjustment, but we really don't know what we are doing with it and what we should be looking for.  
 
 So even though the car ran fast and stable we hope to run in the 235 to 240 mph range next year and want to do everything we can to make the car as safe and stable as possible.
 
 So any comments on ballast, chaining the rear, belly pan, rear spoiler and anything else you could help us with would be greatly appreciated.
 
 You can read more about the runs and see more pictures to compare on the link below.
 
 Thanks in advace for any help,
 
 Sum  
 
 207 mph with Hooley

Offline DallasV

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Re: Ballast Question
« Reply #1 on: December 21, 2004, 02:18:00 PM »
Was the engine running all out or was there a lot of pedal left? With our car when we run out of HP the car gets that really light in the ass feeling and starts to drift. Just the first thing that came to mind.
 
 Dallas
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Offline Sumner

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Re: Ballast Question
« Reply #2 on: December 21, 2004, 02:52:00 PM »
Dallas he was running a stock 400 block and a cast crank so we were limiting it to 6500 and that was right at what he ran on the last run.  It pulled right up to that and by then he was at the end of the 3rd mile and shut off, so the engine probably could have pulled more according to him, but probably would have broke.  We did end up with a couple scuffed pistons.
 
 The first time he noticed any hunting at all was on the 190 mph licensing run where he just ran up to 190 before the 3rd mile and just held it there through the whole mile.  So this situation was a little like what you mentioned.
 
 If the car keeps handling like it has then no problem.  We are just trying to take preventive action with the hopes of running 20 mph faster.
 
 He is getting an after market block and basically a whole new motor, so we won't be limited with the 6500 rpm limit.
 
 Thanks for your thoughts,
 
 Sum

Offline doug odom

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Re: Ballast Question
« Reply #3 on: December 25, 2004, 07:16:00 PM »
What is the front end settings?  Camber, caster and toe?  Does it have a locked or open rear end?? Have you rolled out the tires for the real size of each? Lots of things can make a car wormmy at 200 mph.
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Offline panic

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Re: Ballast Question
« Reply #4 on: December 25, 2004, 08:22:00 PM »
Just a thought, not advice: looks like you're right - the rear is rising at speed. Eventually the rear suspension unloads the tires. Result: oversteer.
 Without going into wing design and placement, you need more angle of attack, even 5 degrees may feel different. If you use too much, the car will be more stable but slower (duh), hopefully before the wing stalls. If you run out of angle adjustment (and still getting improvements), adding length will help some, also an "indy angle iron" can be added to the top surface (only) of the wing rear edge, about 1/4" to 3/8" high. Aluminum "L" shaped extrusion is fine.
 The video would be easier to vet if you took a frame capture and used Photoshop etc. to super-impose that frame on a re-scaled pic of the car at rest to see exactly what angle you're getting (there might be some rise in the front as well, perhaps air is geting under the car).

Offline Sumner

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Re: Ballast Question
« Reply #5 on: December 25, 2004, 10:33:00 PM »
Thanks guys for your input.  It is what we need.  
 
 I sent Hooley an e-mail and will try to find out what he did on the alignment.  I know we didn't measure the tires to check their roll out with each other.
 
 The rearend is a ford 9 inch with a full splool.
 
 panic thanks for the input on the rear wing.  We have never done this before, so Hooley just built one that "looks" right and we set it where it "looks" good and went for it.
 
 I don't think I have any software on my computer that will let me capture the video like you said and our video from outside the car of it going down course isn't that good, but it sounds like a good idea.  
 
 For next year we were going to put some rods on the car with markers on them to see what is happening with the suspension travel.
 
 Also like I mentioned he is finishing up now on a belly pan, but we have no ideas as to the effect it will have on the car.
 
 We are also going to clean up the nose a little and smooth out the fake grill openings at the bottom of the front and make the fronts of the headlights more tear shaped.
 
 Guys we sure do appreciate the input so far and would really like to get all that we can as a lot of you have been running cars over 200 for a lot of years and I'm sure you have a lot of knowledge as to the good and bad things that can happen at those speeds.
 
 c ya, Sum

Offline ddahlgren

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Re: Ballast Question
« Reply #6 on: December 25, 2004, 11:20:00 PM »
You make no mention of the spring rates but if it were me I would start with whatever is the corner weight of the car. IE if the front weight is 800 lbs on each wheel I would use that. if they are slightly different I would average them, a 775 on one side and a 825 on the other is an 800. same for the rear the whole idea is to limit the chassis to around 1/4 inch or less of movement total. Second the angle of attack at speed looks much more realistic that the one sitting still. the aero loss from angle of attack is minor compared to tipping the spoiler/air brake up to gain downforce. Nose up ass down is a bad place to start it looks like a very nice lifting body in the side view standing still. Lastly any chassis is more stable with a g input either positive or negative. if you drone along at zero g input to the chassis it is going to get very 'busy' as it has no way to plant the tires in any direction. Droop limiters are not a bad idea at either end. Chain or cable straps just make sure is something that won't snag anything or hang down below the car at any chassis attitude.
 Dave

Offline ddahlgren

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Re: Ballast Question
« Reply #7 on: December 25, 2004, 11:22:00 PM »
One more thought. When you put the belly pan on I would get the nose as close to the ground as practical,possibly testing spring rates first,  and use approximately 3 degrees on the belly pan with the rear higher than the front.
 Dave

Offline panic

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Re: Ballast Question
« Reply #8 on: December 25, 2004, 11:38:00 PM »
If you can't find anyplace on the car to test that's out of the airstream, the first place to measure is from the rear wheel cover center to the lower edge of the fender. A small dot of sharp color (red or black) in the exact center of the cap will make it stand out in a pic, and a short section of tape with alternate black and white bands 1" apart (smaller is more accurate but may not be visible) on the front and rear of the wheel opening will give you a reference. Easy to draw a line through the center horizontally and pick up which band it catches at speeds. Even if the tape isn't vertical, try to make the bands vertical so you can actually measure it from a pic.
 Many software programs out there that will do a frame capture from a video, someone can do it for you. For best effect (no parallax, minimal perspective) camera height should be as close to wheel center as poss and 90 degrees to the car as it passes.

Offline Bob Drury

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Re: Ballast Question
« Reply #9 on: December 27, 2004, 12:57:00 PM »
Here is one more thing to look at after you have done all of the above.  At speeds above 200 you don't have to move the steering wheel much to affect the car.  Even a subconcious twinge will misdirect the car.  When I was building my car eight years ago, I was told by several Bonneville veterans to use the slowest steering ratio I could obtain.  I wanted to use a rack and pinion steering, so this presented a dilemna.  After much research I found that Roundyround cars use these cute little devices called Steering Increasers to speed up there steering ratios on short tracks.  As I looked at the picture in the catalog, I turned the page upside down, and PRESTO!, I was looking at a Steering Decreaser!  I installed a 1.5 to 1 Increaser upside down below the steering wheel and now have a 66% steering ratio, which has slowed the steering ratio by a full third.  This has in effect taken some of the ability to "over drive" the car avay.  There are now several cars running them and I know that Terry Hunt swears by his.  I have never run my car without it, but I have to believe it helps.  Bob
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Offline Sumner

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Re: Ballast Question
« Reply #10 on: December 27, 2004, 05:56:00 PM »
Thanks for all the respondes guys we really appreciate the input.  Bob I've had some people mention to me about slowing the steering down as much as possible also and think it is a good idea.
 
 I'm still wondering what course of events leads to adding weight to the car.  Seems like a lot of cars have added a lot of weight and are almost twice as heavy as Hooley's.
 
 I'm still trying to get some more facts to some of the questions you have raised and will post them when I get them or Hooley will post them.
 
 Thanks again,
 
 Sum

Offline Bob Drury

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Re: Ballast Question
« Reply #11 on: December 27, 2004, 07:20:00 PM »
Sum,  I don't claim to be a expert, but the rule of thumb I use is: don't add ballast unless the car is spinning the tires or trying to take flight.  Also, keep the ballast between the axles and as low as possible or you may end up with one fast pendulum.  
 Bob
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Offline Rex Schimmer

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Re: Ballast Question
« Reply #12 on: January 03, 2005, 05:23:00 PM »
IFATGMC,
 Just another couple of things to consider with the "Stude". I would suggest that you put the car on scales on each wheel and make sure that the weight on each wheel on each side is as close to the same as possible. I also agree with Dave that you should run some really "stout" springs with wheel rates in the same area as the weight that the wheel is carrying.
 
 From the pictures it does appear that the back end may be lifting which would probably mean that you need to run the car with more forward rake, as it is the air going over the top of the car that is at a higher speed and therefore lower pressure than the air below and is lifting it.   Your belly pan needs to be pretty stiff if you are looking for some sort of gound effect down force from it. When I was doing sports cars back about 20 years ago we had some of the first Lola T600s and they were some of the first "ground effects" cars and our "belly pan" which had the ground effects tunnels in it and extended from the front of the car to the rear was made from Kevlar skins on a 3/4 inch honeycomb core and it was connected to the car with at least 30 fasteners and you could support the thing on each end and stand in the middle and it would not deflect! So make it stiff. You may even consider some sort of side skirt which is legal in your class.Good luck at going 250 and see you a Bonneville in August!
 Rex
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Offline Sumner

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Re: Ballast Question
« Reply #13 on: January 03, 2005, 08:45:00 PM »
Quote
I would suggest that you put the car on scales on each wheel and make sure that the weight on each wheel on each side is as close to the same as possible. I also agree with Dave that you should run some really "stout" springs with wheel rates in the same area as the weight that the wheel is carrying.
 
He has scaled it since last summer and I think the total weight was about 2800 with him in it and almost right on 50/50 front to rear and side to side.  The springs he is using are really stiff and offer very little in the compression mode. I belive they are stiff as they weren't the right ones for the coil overs and he has the coil overs cranked way down. I wonder if they are trying to work with the aero lift and are pushing the car up.  He will have axle limiters on the car for next year.
 
 The pan is out of some pretty stiff aluminum and is attached to the frame rails and crossmembers, so I don't think it has much give, but I'll check with him on that.
 
 Thanks for the suggestions,
 
 Sum

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Re: Ballast Question
« Reply #14 on: January 05, 2005, 06:22:00 PM »
The thing about ballast is you have to be prepared, in advance, to add or subtract as necessary. Remember: as long as you have traction the lighter car will always be faster.
 Same applies to making rear spoilers adjustable. May take several runs to get it where the driver is happy, but seat time is a good thing.
 
 John