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Hopkins Baja Design / Build Thread |
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Old Greg
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Joined: 2009-Jun-24 Location: Tampa, FL Online Status: Offline Posts: 24 |
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Topic: Hopkins Baja Design / Build ThreadPosted: 2009-Nov-12 at 11:35pm |
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My sincere apologies to the Louisville guys, I was going by the results spreadsheet from sae.org, and that's the way Excel sorted it.
Adam, all I mean is that correlation is not causation. 62 inches may be the end all, be all of wheelbases, I don't know. But don't mistake the fact that a lot of fast cars are in that ball park with the idea that it was their wheelbases that made them fast. You can be fast with a long car and you can be fast with a short car; ETS and TTU are both prime examples of this. Don't get me wrong though 62" is a fine number to shoot for, but it isn't the only (or even necessarily the best) way to go. |
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USF SAE
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jhu42
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Joined: 2009-Jan-26 Location: Baltimore MD Online Status: Offline Posts: 128 |
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Posted: 2009-Nov-13 at 8:35am |
Right, there are other things at play that make the fast cars fast, of course. CVT tuning, Weight, Driver skill. I understand what your saying. |
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Adam Baumgartner
Fmr. Hopkins Baja Team Captain- ('08-'10) http://www.jhu.edu/asme/baja.html Honda Design Engineer Underbody Design Honda R&D Americas |
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Waffles
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Joined: 2009-Jun-02 Online Status: Offline Posts: 76 |
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Posted: 2009-Nov-13 at 9:45am |
Was making the point that TTU has a swing-arm, and high CG - you have a swing-arm and low CG... Now I'm sure that there is a difference in stiffness of your arms, but I would have thought that given the same swing-arm stiffness, that the low CG car would have a more difficult time going into oversteer. As such, I was thinking that with a direct drive system, it would be easier to get the rear tires to spin - I was thinking similar to my manual tranny truck, I can't just break the rear tires loose at will, but if i put slack in the drivetrain and then floor it, it's enough of a transient that the rear tires break the static friction and begin to spin. I suppose I'm just making stuff up, lol, it was just a far off theory given two very different cars with IFS+swingarm, yet both equally maneuverable. |
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OctoberSky
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Joined: 2009-May-20 Location: Los Angeles Online Status: Offline Posts: 84 |
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Posted: 2009-Nov-13 at 11:18am |
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Again it is all speculation, but assumingTTU and USF used the same swingarm setup, had the same weight, same tires, etc., with a higher cg TTU would probably oversteer more IMO than USF in terms of actual inches of lateral slide in a turn, but because of TTU's longer wheelbase, the measured "degrees of oversteer" would be about the same. Further proof (speculation) that you can reach the same end result in a variety of ways.
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UCLA Racing
2010-2011 Captain "we'll never win mini baja" -Cheddar |
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dillon_b12
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Joined: 2008-Nov-15 Online Status: Offline Posts: 360 |
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Posted: 2009-Nov-13 at 11:43am |
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What's the obsession with carbon composite rims? From what I've heard from sport ATV guys, they leak, aren't as light as Douglas(depending on label), and cost about 3x more than Douglas.
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Dax
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Joined: 2009-Oct-25 Online Status: Offline Posts: 32 |
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Posted: 2009-Nov-13 at 12:47pm |
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The big thing with composite rims it they are able to deflect elastically, and then return to their original shape, and thus not bend and cause the bead to break and loose air. They also typically come with bead locks to keep the wheel on the rim at low tire pressures and when 'flat'
We are looking into them right now, but are still trying to determine if it is worth it. Any other teams have experience with either composite rims, or even just a bead lock aluminum rim? |
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McMaster Baja Racing
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Waffles
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Joined: 2009-Jun-02 Online Status: Offline Posts: 76 |
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Posted: 2009-Nov-13 at 1:13pm |
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BTW, I think we have successfully derailed the "Hopkins Baja Design / Build Thread", we should probably stop some of these side discussions!
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dillon_b12
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Posted: 2009-Nov-13 at 1:27pm |
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Agreed. Someone can start a new thread about carbon composite rims if they want to continure discussing it.
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Old Greg
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Joined: 2009-Jun-24 Location: Tampa, FL Online Status: Offline Posts: 24 |
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Posted: 2009-Nov-13 at 4:15pm |
Don't forget that TTU's swingarm cars had more rearward weight bias than ours and ran massive rear tires, where we ran 21x7's. In the end they're likely quite similar. If you'd really like to know how they compare, ask Chris Reedy from TTU (CLReedy21); If I'm not mistaken, we let him take a few laps of Auburn in one of our old cars at the 2008 invitational. |
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USF SAE
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USF Stick
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Posted: 2009-Nov-17 at 10:52pm |
The main cons of the rims are Cost and Weight, but the big pro is the durability. Last year, across all 3 races we changed ONE tire. A sharp rock pierced the tire sidewall within the last hour at Wisconsin. That includes hitting the railroad ties in Auburn at full boar EVERY LAP. |
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Justin 'Stick' Van Hall
USF SAE Baja Designer/Fabricator |
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jhu42
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Joined: 2009-Jan-26 Location: Baltimore MD Online Status: Offline Posts: 128 |
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Posted: 2009-Dec-09 at 5:14pm |
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Bringing the thread back ;)
Sort of a teaser, but here's the improved frame side view.
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Adam Baumgartner
Fmr. Hopkins Baja Team Captain- ('08-'10) http://www.jhu.edu/asme/baja.html Honda Design Engineer Underbody Design Honda R&D Americas |
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dillon_b12
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Posted: 2009-Dec-09 at 5:19pm |
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More pics dammit!
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jeiB
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Joined: 2009-Jul-17 Location: Montreal Online Status: Offline Posts: 125 |
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Posted: 2009-Dec-09 at 5:26pm |
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what is your wheelbase on this car?
are you going to the seat yourself? AND MOAR pics... ![]() |
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McGill Baja
2009 - 2011 Captain minibaja.mcgill.ca/ |
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adrive7
Baja Godfather
Joined: 2008-Oct-19 Location: Los Angeles, CA Online Status: Offline Posts: 400 |
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Posted: 2009-Dec-09 at 5:34pm |
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-Joe
Ohio State Baja SAE 2005-2009 |
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blue2kss
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Joined: 2008-Dec-23 Location: USF Online Status: Offline Posts: 79 |
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Posted: 2009-Dec-09 at 9:25pm |
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How tall of a tire are you running?
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Dustin Bride
University of South Florida SAE Alumni/Consultant Mechanical Engineer - Naval Surface Warfare Center, Marine Corps. Counter IED Development |
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charles ulaval
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Joined: 2008-Dec-31 Location: Québec, QC Online Status: Offline Posts: 57 |
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Posted: 2009-Dec-10 at 1:06am |
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looks like you don't have the 12" required that extends from the lowest point of the seat to the upper LC on the RHO.
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BenPoulin
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Joined: 2010-Jan-08 Online Status: Offline Posts: 3 |
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Posted: 2010-Jan-08 at 10:07pm |
I like that quote...
But for the '' We will never win baja'' as long as you learn from your mistakes and that you document your stuff enough so that futur team members can build from your work you'll have a few steps ahead of a lot of the other teams...
Hi everyone, just to introduce myself I'm Ben and I was Sherbrooke's Driver in 2005, 2006 and 2007.
Salut Charles!
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jhu42
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Joined: 2009-Jan-26 Location: Baltimore MD Online Status: Offline Posts: 128 |
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Posted: 2010-Jan-09 at 2:33am |
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Hi guys!
I dont have more pics of the car :( sorry, because we are still finalizing stuff like the suspension and steering. However, when its done I'll upload the SW model for you to check out. Answers to the questions from before. Wheelbase is -> arg! I forgot, will check tomorrow Seat is the Jegs Highback Pro II with the seat cover http://www.jegs.com/p/JEGS/JEGS-Pro-High-Back-II-Race-Seats-and-Seat-Covers/1118147/10002/-1 Really cheap seat that is quite comfy! Really low for the cost report. tire size: fronts 22x7 Holeshot XC , rears 22x8 Mudlite AT Charles -> Good catch!! I see what your saying! Thanks for the note. I will make sure to change that :) Ok!! We started construction back on Jan 3, and have just finished day 5. Hopkins has a nice Intersession period. Class for us starts back up again on Jan 21, which gives us a lot of time to work on the car Putting in some long days but its paying off, we are moving ahead quite rapidly with car construction. Below are some pics along with some captions of how our construction works. ![]() Here's our setup for jigs. We use a smooth pressed cardboard with high quality wooden blocks. Pretty simple. This is our RRH being constructed and assembled before being welded. ![]() Here was our main step today. One of our guys had the idea to use ratchet straps to hold the notched frame pieces together for tack-ing. He saw it on the USF website, thanks guys! I guess I should mention that we do our tacking with a small portable MIG welder in our labspace, but do the actual welding in our Welding room with a really nice TIG. I think its a great combo, the trigger style of the MIG makes it really easy to get a lot of tacks down vs trying to balance a foot pedal for tacking with a TIG. ![]() Here's where we are at so far. Lots to go for sure, but hey, its progress. Cool, ok well I need to get some rest.... Catch you guys later, Adam |
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Adam Baumgartner
Fmr. Hopkins Baja Team Captain- ('08-'10) http://www.jhu.edu/asme/baja.html Honda Design Engineer Underbody Design Honda R&D Americas |
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msctgb
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Joined: 2009-Jul-25 Location: Rolla Online Status: Offline Posts: 14 |
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Posted: 2010-Jan-09 at 4:39pm |
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Looks awesome, love the SIM bends.
Did you change some tube diameters from the CAD model to the real deal? Looks like you stepped a lot of the 1" up to 1.25", looks great. |
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Redhawk_Racing
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Posted: 2010-Jan-10 at 3:11pm |
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Looks great so far! We use the method to jig the frame of the car. Same tube bender too!
We started fab work this Monday and here is our progress thus far: ![]() Edited by Redhawk_Racing - 2010-Jan-10 at 3:14pm |
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SAE 2010 Baja Captain
Miami University |
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jhu42
Welding Master
Joined: 2009-Jan-26 Location: Baltimore MD Online Status: Offline Posts: 128 |
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Posted: 2010-Jan-10 at 10:10pm |
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That's a pretty sweet chassis.
We've always avoided three dimensional bends, but it appears that you can do them very well !!! |
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Adam Baumgartner
Fmr. Hopkins Baja Team Captain- ('08-'10) http://www.jhu.edu/asme/baja.html Honda Design Engineer Underbody Design Honda R&D Americas |
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msctgb
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Posted: 2010-Jan-11 at 1:56pm |
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We use a plane of bend bracket for 3D bends, very simple (I made our team's) to make and use. http://www.offroadfabnet.com/forums/showthread.php?t=924
Helps for 3D bends, and we also use it to make sure we have notches on either end of a long tube in the exact same plane. Or if notches need to be in specifically different planes, whatever. Way better to just turn the tube a known amount than to tilt the head of the mill. |
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Redhawk_Racing
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Posted: 2010-Jan-11 at 2:20pm |
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The 3D bends aren't too hard. You just have to take your time and measure the angles very accurately.
Try it with a couple scrap pieces and you'll get the hang of it. Our rear bends took about three tries to get perfect, but the floor we got on the first try. |
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SAE 2010 Baja Captain
Miami University |
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jhu42
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Joined: 2009-Jan-26 Location: Baltimore MD Online Status: Offline Posts: 128 |
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Posted: 2010-Jan-25 at 3:53pm |
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Hi guys,
Well, classes have finally started at JHU :(, but we got a ton of work accomplished. Here are some photos from the different stages over the last 2 weeks.
Edited by jhu42 - 2010-Jan-25 at 3:53pm |
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Adam Baumgartner
Fmr. Hopkins Baja Team Captain- ('08-'10) http://www.jhu.edu/asme/baja.html Honda Design Engineer Underbody Design Honda R&D Americas |
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EAD Motorsports
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Posted: 2010-Jan-25 at 5:40pm |
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I've gone and forgotten frame basics. Is there a reason not to put the front bracing on the bend? The picture might be deceiving, but it looks like the front bracing member is a long way from point C. |
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