Welded Steel Uprights

[RacingManiac]

Nice setup, the design and construction method is really similar to ours. We were(and to my knowledge for the current team, still is) very limited to CNC resources because our school has no CNC facility available to students, and school shop's pro CNC service is basically occupied with academic projects(machining a giant chamber out of a 700lb Al billet, sure...that'll be 3 weeks, gotta love that...), while outside machining sponsor's timing is based pretty much solely on their initiative and so we try to minimize CNC as much as possible. In fact in 2005 when we last CNCd both our uprights and hubs, they were 3 weeks late with the uprights. So these days we outsource the Hubs and make our own welded uprights inhouse. Manufacturing was pretty much the main reason we went with welded steel, it was important that we get as much control over our timing as we can and running car by mid-March is always the goal to make sure we get a whole lot of running done before comp. Welding 4 uprights was basically a weekend's work and spend another week for heat-treating at our sponsor and a day post machining the bearing bores. Can the CNC Al be lighter? Most likely. can they be as stiff? Possibly if we do a good job on designing them. Can they be done on-time? I doubt that. We usually have the maching design out to our sponsor in Sept, and in 2005 we got them back in parts by mid-late march. For comparison in 2006 and 2007 the uprights were done over Xmas and the car were rolling late Feb. Ours weigh in at ~1.8-1.9lb each...



http://www.fsae.utoronto.ca/20...uction/Rolling05.JPG

[Adambomb]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> In any event I find it very odd that your uprights weren't stiff enough. How did you figure that out or quantify it? </div></BLOCKQUOTE>

Well, we have an old design board that gave a COSMOS deflection of 0.07 deg/g, but I don't believe it. Also, design judge Steve Fox said they looked flimsy. It doesn't appear we have any good pictures, so I'll just describe: They were maybe 1.5 in. thick, ran a dead spindle that was at most 1.2 in. OD, made out of 0.065" sheet, and had some sorry excuse for double shear mounting that involved strips of sheet metal that were 1/4 in. wide where it really mattered. They also had bends and a bunch of goofy angles on everything, and were made out of like 8 pieces of sheet metal. After all this they still weighed something like 1.8 lbs, although with the dead spindle the hubs were a little lighter, like 0.7 lbs. All the ones posted here look 4 times as stiff and half as complex, and pretty much weigh the same.

Also, with the tiny spindle the wheel bearings needed tightened after every hour of driving, which is a pretty bad sign.

As for the "best" way, I'd agree that there really isn't a clear-cut winner between welded steel and machined aluminum, other than what you have the facilities or contacts to get done better. Stiffness per weight is practically identical, and 7075 is only 15% stronger per weight than 4130...although we are still stiffness constrained. The economy has hurt our sponsors, so if the budget looks too bad next year and our friendly neighborhood machinists can't hook us up I can see us re-designing them for good ol' steel.

Ooh, and if we have a numbers competition going here, this year's 7050 Al uprights are 1.25 lbs, should deflect an honest 0.1 deg/g, run true double shear all around, and run 2.6 in. bearings spaced 2 in. apart. Our front unsprung mass is 21 lbs with 20.5x6-13 tires and 9 in. steel rotors. They involved 8 hours of computation time in Matlab...outside of that I'm not talking!

[t21jj]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Adambomb:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> In any event I find it very odd that your uprights weren't stiff enough. How did you figure that out or quantify it? </div></BLOCKQUOTE>

Well, we have an old design board that gave a COSMOS deflection of 0.07 deg/g, but I don't believe it. Also, design judge Steve Fox said they looked flimsy. It doesn't appear we have any good pictures, so I'll just describe: They were maybe 1.5 in. thick, ran a dead spindle that was at most 1.2 in. OD, made out of 0.065" sheet, and had some sorry excuse for double shear mounting that involved strips of sheet metal that were 1/4 in. wide where it really mattered. They also had bends and a bunch of goofy angles on everything, and were made out of like 8 pieces of sheet metal. After all this they still weighed something like 1.8 lbs, although with the dead spindle the hubs were a little lighter, like 0.7 lbs. All the ones posted here look 4 times as stiff and half as complex, and pretty much weigh the same.

Also, with the tiny spindle the wheel bearings needed tightened after every hour of driving, which is a pretty bad sign.

As for the "best" way, I'd agree that there really isn't a clear-cut winner between welded steel and machined aluminum, other than what you have the facilities or contacts to get done better. Stiffness per weight is practically identical, and 7075 is only 15% stronger per weight than 4130...although we are still stiffness constrained. The economy has hurt our sponsors, so if the budget looks too bad next year and our friendly neighborhood machinists can't hook us up I can see us re-designing them for good ol' steel.

Ooh, and if we have a numbers competition going here, this year's 7050 Al uprights are 1.25 lbs, should deflect an honest 0.1 deg/g, run true double shear all around, and run 2.6 in. bearings spaced 2 in. apart. Our front unsprung mass is 21 lbs with 20.5x6-13 tires and 9 in. steel rotors. They involved 8 hours of computation time in Matlab...outside of that I'm not talking! </div></BLOCKQUOTE>

Here are the offending parts

[L B0MB]

and a pic of the new design?....

[t21jj]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by L Bomb:
and a pic of the new design?.... </div></BLOCKQUOTE>

Sorry, no can do.

[Adambomb]

You can see them in Detroit

[JamesCH13]

That looks like messy business in fabrication.

An update: hubs are back from the heat-treaters. We asked if we should have holes in the enclosed sections... heat treaters said no... we were nervous about that, but they are the experts, in theory... The front uprights were fine. One of the rear ones, however, looks like a balloon. All of the panels are bowed out and the center bearing housing warped 0.20". We machined balls to the walls yesterday and made a new bearing housing in 5 hours and I welded together the new rear upright in about an hour. Luckily we had extra sets of panels and the "upright ends" (those threaded studs). DRILLED HOLES THIS TIME. Back at the heat-treaters.

[RacingManiac]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by JamesCH13:
That looks like messy business in fabrication.

An update: hubs are back from the heat-treaters. We asked if we should have holes in the enclosed sections... heat treaters said no... we were nervous about that, but they are the experts, in theory... The front uprights were fine. One of the rear ones, however, looks like a balloon. All of the panels are bowed out and the center bearing housing warped 0.20". We machined balls to the walls yesterday and made a new bearing housing in 5 hours and I welded together the new rear upright in about an hour. Luckily we had extra sets of panels and the "upright ends" (those threaded studs). DRILLED HOLES THIS TIME. Back at the heat-treaters. </div></BLOCKQUOTE>

Lessons to live by with welded upright.....if you drop by Toronto's pit I am sure someone can show you the exact same thing......We had one balloned on us back in 2006, we had to do the same thing to make a new upright, and from then on we've been putting small holes in the tube-gusset for the bolt-on camber block. We ended up cutting that upright in half and use it as prop to show in design presentation. Makes for a good story, and show off the design....