Fun little weight distribution program

[PatClarke]

Here is a fun little program for looking sat weight distribution.
It is really aimed at UK 750 Formula cars, but is fun nontheless. It is courtesy of the Racing Aspirations site.

http://www.racingaspirations.com/weightdistribution.php...1&r1=10&r2=104&r3=48 (http://www.racingaspirations.com/weightdistribution.php?wb=250&wt=150&d1=80&d2=79&d3=-1&e1=50&e2=159&e3=2&g1=10&g2=218&g3=-1&f1=10&f2=109&f3=-47&a1=20&a2=253&a3=1&r1=10&r2=104&r3=48)

There is also a simple suspension design program and a wheel frequency calculator. All fun to play with.
Oh, and a Happy and Prosperous New Year to all
Pat

[Wes Johnson]

On an unrelated note..

http://www.racingaspirations.com/gallery/xmas2007/images/06.jpg

Interesting inboard suspension design. The rocker/rocker pivot/a-arm are one piece!

Lots of bending in this picture:
http://www.racingaspirations.com/gallery/xmas2007/images/15.jpg

Looks pretty fun to drive though..

Regards,
Wes Johnson

[PatClarke]

Wes,
That rocker arm type suspension was pretty common on racecars in the early '70s.
When aero download resulted in very high spring rates, the rocking beam bacame an undamped spring, so push/pull rod and bell crank suspension became the norm.
Sometimes we need to look backwards in order to see forwards =]
Pat

[murpia]

Originally posted by Wes Johnson:
Looks pretty fun to drive though..
Possibly not with that much scrub radius...

Regards, Ian

[Kurt Bilinski]

Originally posted by Wes Johnson:
On an unrelated note..

http://www.racingaspirations.com/gallery/xmas2007/images/06.jpg

Interesting inboard suspension design. The rocker/rocker pivot/a-arm are one piece!

Lots of bending in this picture:
http://www.racingaspirations.com/gallery/xmas2007/images/15.jpg

Looks pretty fun to drive though..

Regards,
Wes Johnson

That's what I use at the front of my mid-engine Mini. Sort of retro. http://www.kimini.com/Diaries/2004Winter/front%20suspension%20in.JPG

[Christopher Catto]

Hey Kurt

i wanted to congratulate you (and your patient and understanding wife/partner!) for your excellent book! http://fsae.com/groupee_common/emoticons/icon_cool.gif

I bought it about october I think but haven't got round to reading it. The person who has read it is actually my dad (elecronics engineer)! I just had the book resting on the table and my dad just asked if he could borrow it after having read a few pages.

So every now and again he brings up things that you did to your Mini. Last night we were talking about how to make the exhaust system as cheap as possible by buying all tubes with same radius bends, as you mentioned.

PS. Wes, I don't understand how you see bending from the picture. Maybe I'm not concentrating enough... I know the design may bend a bit but hardly that much to be fair. Ok, on aero-driven F1 I can understand...

[Kurt Bilinski]

Thanks Chris,

Just put the book in your restroom, that'll give you quality reading time! About the header, it was great fun to make, though having a TIG makes it MUCH easier to weld. I don't know how tough it would be with MIG.

[Mike Sadie]

If you look closely, you can tell that the upper ball joint is a rod end, and in this case with the weight of the car putting it in bending. I think the lower is too; you can see the tube it likely threads into.

It looks like someone put chewing gum on the ARB bearing.

[Wes Johnson]

Originally posted by Christopher Catto:
Hey Kurt

i wanted to congratulate you (and your patient and understanding wife/partner!) for your excellent book! http://fsae.com/groupee_common/emoticons/icon_cool.gif

I bought it about october I think but haven't got round to reading it. The person who has read it is actually my dad (elecronics engineer)! I just had the book resting on the table and my dad just asked if he could borrow it after having read a few pages.

So every now and again he brings up things that you did to your Mini. Last night we were talking about how to make the exhaust system as cheap as possible by buying all tubes with same radius bends, as you mentioned.

PS. Wes, I don't understand how you see bending from the picture. Maybe I'm not concentrating enough... I know the design may bend a bit but hardly that much to be fair. Ok, on aero-driven F1 I can understand...

Christopher,

As Mike said, the upper and lower ball joints are rod ends. Not only does the vertical force put the rod end in bending but the braking torque is reacted with a bending load in the rod end. Yes it will work, just do a search and you can see the many discussions on this.

Also note that the ARB arm is attached to the drop link in single shear and the ARB has a pretty long unsupported length from the bearing putting that section of the bar in bending. Seems like a good way to introduce some stiction in roll.

Even if the design on that car works it's still not the absolute best engineering practice.

Thats just my 2 cents though.

Best,
Wes Johnson

[flavorPacket]

Single-shear ARB mounts are typically not a big deal. Our 07 car has a fairly soft ARB and a relatively short single-shear mount, and the mount is roughly 3 orders of magnitude stiffer than the bar, which puts it in the same category as the droplink itself. Maybe your numbers are different, but it was easy for us to "get away with."

Of course, a double shear mount is almost always more efficient, but if the forces are tiny, it may not be necessary.

edited for spelling

[ben]

I think single-shear mounts are acceptable if packaging is very tight and only then if it's not primary structure.

ARBs are fine because the car won't collapse if it fails - it'll just roll more. Any suspension or steering link is another matter.

The Dallara F3 lower front ball joint is an example of someone getting away with an imperfect design. However the GP2 car is definitely double shear, as was their LMP car.

Ben

[Wes Johnson]

Originally posted by ben:

ARBs are fine because the car won't collapse if it fails - it'll just roll more. Any suspension or steering link is another matter.

Ben

True, however if the ARB's provide a large percentage of the roll stiffness then I'm sure the driver won't be too happy when his front bar fails mid-corner...

As stated above and before, it's all about making compromises and balancing pros/cons of particular designs. If single shear mounts and rod ends as balljoints fit your design criteria better than the alternative, then you must employ these design decisions.

-Wes