Upright Problems

[cdoc83]

Hi all,

Im new to formula student and have been given the project to design the front uprights.
I was wondering if anyone give me a few examples of what to look out for when designing these?

Thanks

Chris

[kwancho]

My advice is to go download the competiton pictures, especially the ones Leon took from WWU and sift through those. Infinitely helpful.

[Matt Gignac]

You can find them here

http://fsae.com/eve/forums/a/tpc/f/825607348/m/39210181521/p/8

Matt Gignac
McGill Racing Team

[Schumi_Jr]

If you have access to titanium laser deposition forming we have our 2006 design posted on : http://pg.photos.yahoo.com/ph/gakenwor/album?.dir=b4c4&...h/gakenwor/my_photos (http://pg.photos.yahoo.com/ph/gakenwor/album?.dir=b4c4&.src=ph&store=&prodid=&.done=http%3a//pg.photos.yahoo.com/ph/gakenwor/my_photos)

The images are from a finite element optimization software.

[James Waltman]

(If you read through all of the posts at the topic that Matt linked to you'll find most of this.)

You can download a zip file that has reduced resolution versions of all the pictures we took in Detroit 2005 here:
http://dot.etec.wwu.edu/fsae/HostedPics/ALL_2005_FSAE_PICS_BY_WWU.zip
It is about 120MB and 1300+ pictures. I think about a third are mine. Major contributions by Leon, Ché, Justin, Jack, and Vedran.
Email me if you want a full resolution version of any you see.

Dan G (U Michigan – Dearborn) has a pretty good set of pictures here: http://evilallianceracing.com/ipw-web/gallery/FSAE05?page=1

Mexellent (UTA) has a zip file of about 370 pictures here: http://www.moretab.com/alex/FSAE/detroit05.zip

Vu (Rutgers) has some really nice pictures in this gallery: http://stoopidsavant.com/v-web/gallery/0505fsae

[WAM BAM]

Way to go, do you have a life at all?

Wow, I thought the universally accepted design philosophy on here was the 'brown go-cart', right, Rob? How is the cmpetition suposed to be even if guys like you farm out FEA and (obviously) manufacturing of all critical components?

This competiton should be run more like 'junk yar wars', so that you guys are forced to think on your feet, rather than, hiding behind your fancy computer-thingies!

Back when I was working on SAE supremileage, we did all of our design and calculations on paper and still managed to build a car that would be the lightest at any FSAE competition.

Get wth the times!

[Denny Trimble]

http://img.photobucket.com/albums/v471/cdmandus/awgeez3.jpg

Oh yeah? My micro-baja car is lighter than your supermileage car. Therefore, you are obviously inferior.

[Jersey Tom]

Schumi - how do the mechanical properties of your laser-deposited Titanium structures compare to the base metal?

Dunno bout the rest of you, but I'm machining my uprights. I wouldn't even contemplate letting someone else do em for me. Too much fun!

Was pushin a .500 flat end mill at 80ipm today, ho my my my, too fun. Makes me wish I had a Mori so I could push 200.

[jack]

Originally posted by WAM BAM:
This competiton should be run more like 'junk yar wars', so that you guys are forced to think on your feet, rather than, hiding behind your fancy computer-thingies!

yeah, just like real racing! http://fsae.com/groupee_common/emoticons/icon_rolleyes.gif

jersey tom, you can have our mori--you haul.

[Jersey Tom]

You have a Mori Seiki.. mill? Model? Year?

Christ, if I had one of those... I'd machine our whole chassis out of a solid block of 4130. And get it done in an hour.

You dont want it, I'll find a way to haul it to Colorado. Gotta be less than the cool quarter mil for a new one...

[Psychosis]

so unfair... first machining, then CNCing, then laser deposition. we're stuck with folding bits of steel, which we bastardise to shape with a hacksaw and file, and welding them together http://fsae.com/groupee_common/emoticons/icon_biggrin.gif

beats laser deposition uprights any day http://fsae.com/groupee_common/emoticons/icon_razz.gif

steel... its the way forward (i can only think of one load bearing part on our car which isnt) http://fsae.com/groupee_common/emoticons/icon_wink.gif

back to topic, biggest thing to look for in uprights, is manufacturability. i.e. can you make them and in good time? the more parts you make yourself the less you rely on others, who may not be working to your deadlines.

[Cement Legs]

We make our uprights out of weld... entirely... the tricky part is getting started but once you've got the proverbial ball of weld rolling... just add according to dimensions http://fsae.com/groupee_common/emoticons/icon_razz.gif

[Schumi_Jr]

Jersey Tom,

Sorry, we actually CNC machine our uprights. I only know laser powder deposition exists because I saw some guys from South Dakota School of Mines & Tech talk about it at the 04 SAE Motorsports conference - maybe you can ask them?

Chris - Denny has made some very good points in previous upright discussions particularily on steel vs. aluminum. Try searching for "Upright Design" on this forum.

Obviously upright (and suspension) design is a structural problem. I'd suggest approaching your design with a stiffness target (obtained from tire data and experience)for the ENTIRE system, find out what components dominate the system compliance and focus on making them stiffer. We have targets for vertical, toe and camber stiffness and try to make our suspension as light as possible while meeting them. Also, don't forget about the necessity of a stiff caliper mount.

As far as inspiration for your design - look to F1. I'm not suggesting that you should investment cast your uprights out of Al MMC (though you should if you can) but look at the structure of their uprights. You could definately produce something with similar load paths out of sheet steel or CNC'd aluminum.

[cdoc83]

Thanks for the help all. Im sure I will have more questions when I get into this.

[Z]

Originally posted by Schumi_Jr:
As far as inspiration for your design - look to F1.
Gotta disagree there.

F1 uprights are dominated by the cooling passageways for the wheel bearings and brakes. You definately (Edit: Oops, "definitely") don't need these in FSAE (at least nowhere near as big as the F1 ones). No offence (best put some of these in http://fsae.com/groupee_common/emoticons/icon_smile.gif http://fsae.com/groupee_common/emoticons/icon_smile.gif http://fsae.com/groupee_common/emoticons/icon_smile.gif), but blindly copying an F1 upright would be plain stupid. (Edit: BTW, I agree with Aaron's paragraph on upright design being a structural problem, setting stiffness targets, etc.)

IMO folded and welded sheet steel (~1mm/0.040" thick 4130, or ~1.5mm/0.060" MS) is, all things considered, lightest, stiffest, strongest, cheapest, and easiest!

Z

[fade]

ETS made some definately F1 inspired uprights on their latest car. Can anyone comment on the welding fixtures used for constructing sheet metal uprights?

[Z]

Fade,

If you do it right the folded sheet metal approach is just about "self-jigging" - ie. fold on dotted lines, assemble by "inserting tab-A into slot-B", etc., then weld along seams...

Otherwise a very simple jig defining position of 3 x ball joints and central bearing housing.

Z

[Garbo]

Don't write off F1-esque uprights as being purely aerodynamic. We did some interesting analysis and had some surprising results (which WERE checked with some common sense and DO make perfect sense)... come by and have a look in Detroit...

That said, I think, based on my experience, boxed steel uprights would be an excellent choice for stiffness and weight, particularly for a team with limited resources. This is largely by virtue of it being possible to fab nice closed sections (the old lunch box analogy). Building light fabbed uprights is not easy, however. Building dimensionally accurate fabbed uprights requires heavy jigging during heat treat and post machining. It is easier to build a very accurate set of aluminum uprights but there is possibly a penalty to be paid in stiffness/weight as well as $$$, depending on your CNC hookup. Flip-flopping again: our current aluminum uprights are (I believe) lighter and stiffer than our old fabbed steel ones but this is for a variety of reasons unrelated to material choice.

... and finally, as Jr. said, you have to look at all contributors to compliance. It is entirely possible that stiffening the upright gives diminishing returns where better supporting your wheel bearings could lead to a much cheaper (in terms of weight) increase in stiffness.

Cheers
G

[Storbeck]

Does anybody know where there are good pictures fo an F1 upright? Seemslike with all of the ducts and a huge rotor and caliper there the pictures i've seen you can't really see the upright itself.

[TG]

Originally posted by Storbeck:
Does anybody know where there are good pictures fo an F1 upright? Seemslike with all of the ducts and a huge rotor and caliper there the pictures i've seen you can't really see the upright itself.

Here's a '99 minardi upright
http://www.castsolutions.com/archive/CastingSucesses/Images/CA0600_04.jpg

I guess common sense would tell you that the cooling passage area would act similar to the core of a sandwich construction. The radial patern would be fine because there isn't supposed to be much torque about the axis of the spindle.

I dug up this link that was posted on another thread of ETS' car at Formula Student (http://people.pwf.cam.ac.uk/mac65/misc/formula%20student/Photos/ETS/).

[Chris Clarke]

Originally posted by fade:
Can anyone comment on the welding fixtures used for constructing sheet metal uprights?

Here is a link to a CAD drawing of an upright that uses lasercut sheet metal, and demonstrates how it can be partially self-jigging. The pic is in the middle of the page.

Lasercut sheetmetal upright (http://www.locostbuilders.co.uk/viewthread.php?tid=33544&page=2)

[Psychosis]

Originally posted by Chris Clarke:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by fade:
Can anyone comment on the welding fixtures used for constructing sheet metal uprights?

Here is a link to a CAD drawing of an upright that uses lasercut sheet metal, and demonstrates how it can be partially self-jigging. The pic is in the middle of the page.

Lasercut sheetmetal upright (http://www.locostbuilders.co.uk/viewthread.php?tid=33544&page=2) </div></BLOCKQUOTE>

that's commedy, build it like a jigsaw.

i've always been under the impression that (though a large amount of work goes into it, don't get me wrong!) that the ETS car is a scale model of an F3 car. hence uprights (which look odly like shrunk F3/F1 uprights) with air passageways that odly, don't lead to vented rotors. sorry, i find it amusing. http://fsae.com/groupee_common/emoticons/icon_biggrin.gif

[Jersey Tom]

Welded box uprights are cool, and when we started design this year a lot of people wanted to see that implemented on our car. There are a lot of concerns though, for this part which sees all the forces the car develops through cornering, acceleration, and braking, and is so safety critical.

Our top dog welder graduated, and we were originally unsure who if anyone was going to fill that void. As such you have to wonder, when someone lays down those weld beads, how strong is the weld? How well is it penetrating? Even if you fabricate a test specimen and have it x-ray'd to find out - how repeatable is your welder?

Takes time to accurately cut, prepare, and jig all the stel. Then you have to do a post-weld stress relief with a full anneal.

After that, there's still secondary spot-machining required on critical areas (bearing housing for example). And since due to cut tolerance and welding the outer dimensions of this thing are going to vary from part to part, that will make fixturing it that much momre difficult. After that you can heat treat it and bring it back up to whatever hardness you want.

And in the end, while steel as a base metal has good fatigue properties, your fatigue life at the weld seams is a fair amount lower.

I could go on...

Doing decision analysis on this whole thing, FOR OUR PROGRAM and the resources we have available, a CNC'd billet design is more advantageous.

[Schumi_Jr]

Originally posted by Z:
F1 uprights are dominated by the cooling passageways for the wheel bearings and brakes.

Don't worry Mr. Zapetal, I'm not that easily offended http://fsae.com/groupee_common/emoticons/icon_smile.gif. I agree about the ducts. I'm not suggesting anyone copy F1, but the way they deal with the load paths in their design are worth considering. The ribs between the bearing housing and outer ring provide excelent camber/toe stiffness. A hollow sheet-steel upright will have problems with the thin plane sections bending. Internal ribs will reduce the effective size of the planar sections and increase toe-stiffness. They can also provide a more direct load path between the outer ball joints and wheel bearings. Since an FSAE car doesn't really need cooling ducts of that magnitude the open central section can be closed out further increasing stiffness. I guess it all comes down to the trade-off between sophistication (complexity) and simplicity in your design.

[Z]

Originally posted by Schumi_Jr:
Don't worry Mr. Zapetal...
Grrr! I make all this effort to simplificate and people still spell it wrong! http://fsae.com/groupee_common/emoticons/icon_rolleyes.gif

Back on topic... I agree with Psychosis regarding the "jigsaw" upright. Why go to the effort of laser cutting sheet steel and then make it look like it has been thrown together from some offcuts of RHS? http://fsae.com/groupee_common/emoticons/icon_confused.gif

For anyone considering the folded sheet metal approach I suggest you make it look like a "triangular pillow" with a hole in the middle for the axle. This can be made from a single roughly triangular sheet with the corners folded inwards. Practice with a sheet of stiff paper (Cornflakes packet is good), a pair of scissors, and sticky-tape (or hot-melt-glue gun). The central bearing housing, and the ball-joint/caliper lugs, are probably easiest made from machined bar. The bearing housing should have external flanges (circumferential ribs) that connect to the folded sheet (these can be tapered from thicker near the bearings, to sheet thickness at the outer diameter).

Regarding the jigging/welding/stress-relieving/heat-treating/post-machining; a lot of this is unnecessary. With mild-steel (~1.5 - 2.0mm thk) just weld it (oxy/tig/mig/stick), then paint it. If one of the ball-joint gubbins moves half a millimetre I doubt the best driver would ever notice it. The bearing housings often don't need any post-machining. If they do move it is because they shrunk a few thou', so you take them out a little. With 4130/4140 you can tig with stainless steel filler rod, then paint. Welds should always be in areas of lower stress. If you want to go the full heat-treat route with thin-gauge high-tensile steels, then fine - you have the lightest, stiffest, strongest uprights in the paddock.

A big advantage of folded sheet is that it is very easy to have a closed shell with lots of tapers and curves. If done right this is very efficient structurally - just look in the boneyards out the back of an abattoir. You can also do this with castings, but it is harder to make them hollow shells (with no holes in the walls), and the walls are much thicker and rougher, and often have porosity. Thin wall shells are very light, stiff, and strong - look a bird skeletons. http://fsae.com/groupee_common/emoticons/icon_smile.gif

Z

[Jersey Tom]

Regarding the jigging/welding/stress-relieving/heat-treating/post-machining; a lot of this is unnecessary. With mild-steel (~1.5 - 2.0mm thk) just weld it (oxy/tig/mig/stick), then paint it. If one of the ball-joint gubbins moves half a millimetre I doubt the best driver would ever notice it.

Residual stress is one concern, but I'm more worried about the heat-affected zone of the weld , and the whole region being laced with martensite from rapid cooling (quenched by its surrounding, colder steel). Thus the full anneal to both relieve residual stress and more importantly recrystalize the welded area.

[Z]

Tom,

The reason mild steel is so widely used is that it is so easy to weld - any half decent weld on mild steel is stronger than the base metal (the filler rod is higher grade steel). Also any good design should have the welds in areas of lower stress, just in case it is Monday and the welder has a hangover... Or the weld area has a greater section than the base metal, eg. fishmouthing, or gussets...

Also worth noting that 4130 was developed in ~1920's as a higher strength steel that is EASY to weld when used in thin wall tubular sections for aircraft spaceframes. Back then all the welding was done with oxy-sets, and there was no putting it all in a big oven for stress-relief or heat-treat.

Also common was brazing of 4130. This works best when done with gussets (look at older bicycles) because the braze metal is quite weak so needs a larger section area. Brazing doesn't get so hot, so less "heat damage" - think of it as high strength glue. Welding with stainless filler rod also requires more section area (or weld in lower stressed area) because the SS is also weaker than 4130. But the SS is quite ductile (good for impact safety), and the chrome/nickel prevents the 4130 getting brittle.

That said, you either enjoy welding (and bashing away on a piece of red hot iron on the anvil - blacksmith style), or you are s#*! scared of it. In the latter case it is probably better to gently place a block of aluminium in a CNC machine, press the "On" button, and go have a cup of tea http://fsae.com/groupee_common/emoticons/icon_smile.gif.

Z