front uprights

[Cement Legs]

I'm trying to come up with an alternative design for our front uprights. currently we are set to use steel tubing with attachment points welded on the main piece. After some consideration and hopefully some inovation as well I've come up with a design that I think will suit our team much better (ie more adjustability with less work). I know it depends on many factors but I'm just curious what thickness of material, 6061, teams are using for this type of process.

Secondly, for teams that are shimming the top of their front upright for camber adjustmentsare you using wedge shapped shimms to keep from moving your roll center when you go from say one degree of camber to 4 degrees. If not are you setting up the system to have the ideal roll center for camber settings that your would prefer for events like the autocross and endurance. Therefor just accepting the suspension as is with the adjusted camber for other events like the acceleration and skid pad.

And lastly, would a press fit for the spindle be enough assuming a tight tolerance with a "nail type head" comming from the inboard side of the upright?

Cheers

[Denny Trimble]

Howdy,
I think 6061 is a less-than-ideal material for uprights. The only reason to use it instead of 7XXX would be that you're welding your uprights out of sheet, and to be honest we've had bad luck with welded aluminum structural stuff. Make sure your welder is good, and leave a lot of room for post-heat-treat finish machining, because of warpage.

You should look into steel sheet uprights. We used to do steel tube uprights, but recently our boxed uprights have doubled in stiffness compared to the previous design, at the same weight.

They follow the same design idea as aluminum box uprights, but you can use 1/3 the wall thickness for the same stiffness and weight, and slightly increase the diameter of your box sections for a little more stiffness. Plus, the hardpoints don't take up as much space. If you're constrained on outside dimensions, steel will give a more efficient structure than aluminum or magnesium.

Our steering arm mount is inclined to be parallel with the upper control arm at some nominal ride height, so camber adjustments create a minimal IC location change. Also, we rarely adjust outside of -.75 to -2.0.

We've used that type of press-fit spindle for several years. Make sure you account for your expected operating temperature, and find out how much your aluminum will expand at that temperature, and make sure it's still a press-fit You can do a shrink fit (spindle in freezer, upright in the oven, assemble quickly) to help things along.

[Cement Legs]

Hey Denny, to be honest I really like the way some people reply on this site, objective and factual, with just a little touch of "but I kinda like it like this". I appreciate it because you don't come off sounding like someone whos telling me what to do, rather more like someone with good honest experiencial feedback.

Anyway, when you say boxed uprights, what is different than using normal steel tubing? I guess I'm just not familiar with the term 'boxed' in this context.

[Denny Trimble]

Well, instead of using square or rectangular tubing, you can weld up (or fold and weld) trapezoidal or other crazy tapered box shapes. Then the structure connects your bearing bore to your control arm points efficiently, and you can change the taper and thickness of each plate.

You can see this on our rear uprights from 2004:
http://students.washington.edu/denny...r%20small.html

Yeah, I like these forums too.

[Cement Legs]

WOW! Denny that model is impressive. Really nice work.

Yeah I guess I can see why you would prefer steel with that setup. I remeber seeing some posts of people claiming less than 2 lbs for upright and spindle and that kinda makes it more believable now.

Cheers

[Angry Joe]

I agree on going with steel if you're making it from sheetmetal and tubing. One thing I hate seeing, though, is uprights basically consisting of one tube in bending with a bearing support stuck in the middle.

If you're going with aluminum, machining from billet is probably the best. It won't be quite as light as a good sheetmetal upright, but manufacturing is easier. We did use shim inserts to adjust camber, they were machined so that you simply loosened the upper mounting bolts and slid them in.



Just don't put rod ends in bending like we did! (oh the shame...)

[MikeWaggoner at UW]

You can also make hollow aluminum uprights. You can incorporate ribs that help with stiffness. The bond surfaces can be easily milled using a taper mill.

[alfordda]

Denny-

How are you adjusting camber? Is it through shims on the monocoque side?

[Denny Trimble]

With a big hammer...

But seriously, there are inserts in the steering arms that have their attachment holes drilled at various lateral offsets. Swap 'em out and the steering arm is at a different lateral location relative to the upright for camber adjustment.

[Buckingham]

To answer the orignial post:

We ran 6061 uprights last year. They never broke. We drove last year's car almost four days a week, every week from early march through May. 6061 is a lot cheaper, more machinable, and nearly the same stiffness.

This year we will be using 7075 because I went into the forest and chopped down an aluminum tree.